Note: Descriptions are shown in the official language in which they were submitted.
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A METHOD IN CONTROLLING AN ENGINE OF A FOREST MACHINE, AND A
FOREST MACHINE
Field of the Invention
The invention relates to a method in the control of an engine used as the
primary
power source for a forest machine. The invention also relates to a forest
machine
fitted to perform manipulation of tree trunks on a terrain.
Background of the Invention
For harvesting, several forest machines are known which move on a terrain,
such as
harvesters. In the harvesters, a boom assembly is used, whose end is provided
with a
harvesting device, so-called harvesting head. By means of the harvesting head,
an
upright growing tree trunk can be cut, felled, delimbed, and further cut into
logs of
desired length. The tree trunks thus treated can be collected from the terrain
aboard a
moving forest machine equipped with a loading grapple, i.e. a forwarder. In
the load
space of the forwarder, the tree trunks are transported further, for example,
to the side
of a drivable forest road. There are also known combined machines in which the
functions of a harvester and a forwarder have been combined, wherein the
loading
grapple may be replaced with a harvesting head that is also suitable for
loading.
Alternatively, in the combined machine, it is possible to use several boom
assemblies
for harvesting and loading functions separately.
The primary power source used for forest machines of the above-mentioned type
is
typically a diesel engine which further rotates a hydraulic pump. The purpose
of the
hydraulic pump is to convert the mechanical energy produced by the diesel
engine
(rotational speed, torque of the engine) to hydraulic energy (volume flow,
pressure
produced by the pump). The hydraulic energy contained in the hydraulic system
of the
forest machine is further used to drive the actual hydraulic actuators of the
forest
machine. The hydraulically driven actuators, for example in a harvester,
include
hydraulic driving motors coupled to the wheels, hydraulic cylinders of the
frame
steering, hydraulic cylinders moving the boom assembly, as well as various
hydraulic
cylinders and motors included in the harvesting head. To the diesel engine
used as
the primary power source can also be coupled a number of various hydraulic
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pumps which may be placed, for example, one after the other on the
same driving shaft. Separate hydraulic pumps may be provided, for
example, for the driving motors, the boom assembly, or the harvesting
head.
In forest machines of prior art, the diesel engine is arranged to rotate
the hydraulic pump/pumps substantially at a constant speed of rotation
when the forest machine is in operation. The hydraulic pump driven at
a constant speed of rotation is, in turn, arranged to provide either a
given constant pressure level on the main line of the hydraulic system
or to operate in a load-sensing manner, wherein the main line is always
supplied with a pressure level and a volume flow according to the
need. From the main line of the hydraulic system, hydraulic power is
taken, for example, by the hydraulic actuators of the harvesting head
via their respective control valves according to their respective needs.
In a situation in which the loading of the hydraulic system increases so
high that the torque required of the diesel- engine driving the hydraulic
pump exceeds the capacity of the diesel engine, the production of vol-
ume flow by the hydraulic pump is reduced, if necessary, so that the
hydraulic pressure in the main line of the hydraulic system can be
maintained substantially on the desired level. The above-mentioned
limitation in the power of the hydraulic system is typically implemented
by changing the so-called control angle affecting the stroke volume of
the hydraulic pump.
The speed of rotation of the diesel engine is conventionally kept con-
stant with a mechanical governor in connection with the injection pump
of the engine, to increase or decrease the fuel supply to the engine, if
necessary. Consequently, the governor thus, in a way, increases or
disengages the throttle of the engine to maintain a constant speed of
rotation when the output of the diesel engine required by the hydraulic
pump varies in different situations. During maximum output of the
engine, said restriction of the power of the hydraulic system is used, if
necessary; in other words, the volume flow (control angle) produced by
the hydraulic pump is reduced to prevent a situation in which the torque
of the diesel engine required by the hydraulic pump exceeds the
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maximum capacity of the engine, and the speed of rotation of the
diesel engines may drop.
In forest machines, particularly harvesters, the total need for hydraulic
power varies to a great extent according to the operation conducted by
the forest machine at the time. In the case of the harvester, these func-
tions can be roughly divided into, firstly, the movement of the harvester
by driving on the terrain of the ground for logging and, when the har-
vester stays still, the manipulation of tree trunks by means of the boom
and the harvesting head connected to the same. Hereinbelow, refer-
ence to these functions will be briefly made by the terms transport and
harvesting.
Harvesting can be divided further into different steps which include, for
example, the movement of the boom and the manipulation of a tree
trunk by felling, cross-cutting and delimbing. With respect to the power
demand,for example felling and cross-cutting' are'Toperations which will
temporarily require a high hydraulic power, whereas the movement of
the empty boom without a tree trunk in the grip of the harvesting head,
the working machine staying still, will only require a relatively low
hydraulic power.
To maintain the efficiency of the forest machine as high as possible, it
is known to be important that, for example in harvesting, the speed of
rotation of the diesel engine must not drop during the felling and cutting
of trees which temporarily require high hydraulic powers, because this
will significantly slow down the harvesting or affect directly on the qual-
ity of the timber to be manipulated. In the worst case, a drop in the
speed of rotation of the engine, for example, during cross-cutting, may
cause a temporary deceleration in the sawing, and a cracking of the
tree trunk in the longitudinal direction when under torque and sup-
ported by the harvesting head, which reduces significantly the value of
the trunk being manipulated. During delimbing, in turn, the feeding of
the trunk at the harvesting head may, for example, stop at a particularly
thick branch because of insufficient engine power. As a result, said
manipulation operation is significantly slowed down or must be
repeated.
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In the design of a forest machine, such as a harvester, the category of
the size and capacity of the diesel engine used as the primary power
source must be, in practice, selected so that the maximum output of
the engine is sufficient for performing even the most power demanding
operations, such as felling and cross-cutting, without recurrent unde-
sired drops in the speed of rotation of the engine due to overloading.
The power source must also be capable of overcoming situations in
which, for example, several hydraulic functions of the boom and the
harvesting head are applied simultaneously during the manipulation of
a heavy trunk. Consequently, the selection falls on a diesel engine
whose power and torque properties provide an optimum compromise of
the needs occurring in practice.
However, it is the maximum needs of the functions of the forest
machine which primarily determine the size, nature and operating
mode, to be kept substantially constant, for the engine to be selected
for the forest machine; consequently, the arrangements of prior art are
not operating in the range of the best efficiency when said engine is
loaded with a partial load only. In practice, maximum output of the
engine and the hydraulic system is required only occasionally, and
during most of the operating time, a partial power substantially lower
than the maximum capacity is applied. As a result, the efficiency and
the specific fuel consumption of the engine are not optimal during typi-
cal use of the forest machine according to arrangements of prior art.
The reason for the poor efficiency with partial loads can be understood
in the following way. According to prior art, the engine is only aimed at
keeping its speed of rotation at a constant level, corresponding to the
respective valid need for the speed of rotation, wherein the power out-
put of the engine, in practice, also follows the engine output required by
the hydraulic pump at each time. However, since the engine is not
subjected to any other control parameters representing more closely
the on-going working situation or particularly the forthcoming situation,
the readiness for power production is always at a maximum level in the
arrangements of prior art. In other words, the engine is ready to pro-
duce more power up to its maximum capacity only by increasing the
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throttle, if this is required by the power intake of the hydraulic pump
from the shaft of the engine. In situations of partial loading, this readi-
ness for power production which is unnecessarily high and redundant
to be maintained, reduces the efficiency of the engine, because the
5 settings effective on the method of fuel supply into the engine are con-
tinuously "maintained" optimal for the maximum output only. With par-
tial outputs, these settings prevent the operation of the engine at an
optimal efficiency, thereby increasing the fuel consumption of the
engine, which is further manifested, for example, as an increase in the
quantity of harmful exhaust gas emissions.
Furthermore, a mode of the forest machine is known from prior art, in
which the driver of the harvester when in light work, for example work-
ing in a stand marked for cutting and containing only relatively small
trunks, manually adjusts the level of the constant speed of rotation
used in the diesel engine to a lower constant level than normally in a
situation when the maximum output of the engine is not likely to be
used. This procedure reduces the engine's readiness for power pro
duction and thereby reduces the total fuel consumption of the working
machine, but it also significantly increases the risk of an undesired drop
in the speed of rotation of the engine, for example, when the harvester
hits particularly strong points in the trunk or branches during delimbing
or cross-cutting. The procedure also decelerates the functions of the
working machine as the continuously more slowly rotating hydraulic
pump produces, on the desired pressure level, volume flows which are
smaller than normally. Moreover, in a diesel engine equipped with a
conventional mechanical control means, a reduction in the speed of
rotation from the range of the nominal speed of rotation will also involve
shifting off the range of the best efficiency of the engine. In practice,
the driver cannot manually adjust the level of the speed of rotation con-
tinuously as the work proceeds, but he must select a constant rotation
speed level suitable for the job.
It is a primary aim of the present invention to provide a quite new
method in the automatic control of the engine of a forest machine,
which method enables the operation of the engine used as the primary
power source for the forest machine with a better efficiency than before
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and thereby with a lower fuel consumption and also with significantly
smaller exhaust gas emissions. The invention also relates to a forest
machine implementing the method.
The basic idea of the invention is to optimize, by prediction, the control
parameters of the primary power source of a forest machine, preferably
a diesel engine equipped with an electronic control unit ECU, by
adjusting the power source to produce a suitable and sufficient power
level needed for each operation to be performed by the forest machine,
without maintaining a redundant readiness for power production,
wherein said operations can be performed more economically than in
prior art and causing as little emissions to the environment as possible.
For understanding the basic principle of the invention, it is essential to
notice that a given partial power level of the engine, for example 50 %
of the maximum power indicated for the engine, can be produced in
modernry electronically controlled engines at different efficiencies by-,
selecting -the control parameters of the engine in different ways. In
other words, with different values of the control parameters, the fuel
consumption of the engine is different, even though the same partial
output of 50 % were taken from the engine in all these situations.
Reciprocally, the readiness of the engine for power production is also
different with different values of the control parameters. In this context,
the readiness for power production refers, first of all, to the maximum
output of the engine with said values of the control parameters, but
also to the way in which the engine reacts, i.e. its "aggressiveness"
when the power demand is suddenly changed. As a result, it is possi-
ble to optimize the control parameters of the engine in relation to each
operation to be carried out by the forest machine in such a way that the
engine economically provides the sufficient power output for each
operation but without maintaining an unnecessarily high readiness for
power production, which thus has the disadvantage of a distinct reduc-
tion in the efficiency.
In view of the fluency of working with the forest machine, the above-
mentioned selection of the control parameters of the engine must be
essentially made by predicting the operations of manipulating a tree
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trunk with the forest machine, wherein it is possible to minimize the risk of
an
unnecessary drop in the speed of rotation of the engine during said
manipulating
operations.
The invention relates particularly to such forest machines, for example
harvesters,
which are used for the manipulation of tree trunks on a terrain in such a way
that the
properties of the tree trunk subject to manipulating operations at the time
are
determined by means of one or more measurements of said tree trunk by the
forest
machine and/or by means of information entered by the driver of the forest
machine
into the systems of the forest machine.
One example of such measurements, known as such, is the measurement of the
felling diameter of the tree trunk by the harvesting head when the harvesting
head
grips the upright growing tree trunk for the felling of the trunk. The
diameter and the
length of the trunk can be measured in ways known as such, also when the
harvesting
head shifts its grip of the tree trunk during delimbing and cross-cutting of
the trunk.
The driver of the harvester, in turn, can, in a way known as such, enter
information
about the wood species of the trunk to be manipulated at the time, into the
system of
the harvester at the beginning of the manipulation of said trunk. On the basis
of this
information, the harvester can, in a way known as such, determine, for
example, the
estimated conicality and length of the tree trunk, and by using this so-called
trunk
prognosis determined for the single trunk, mark said tree trunk for cross-
cutting, i.e.
make a sawing layout for cutting the trunk in an optimal way into wood
products for
different classes of length and diameter.
According to the invention, the properties of a single tree trunk, such as the
trunk
prognosis, defined at the beginning or during the manipulation
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of said tree trunk, are used to estimate the power levels required by the
manipulating operations to be carried out on said tree trunk by predic-
tion, i.e. already before said manipulating operations are started. Such
manipulating operations may include, for example in a harvester, the
sawing for felling the tree trunk during harvesting, and the delimbing
and cross-cutting of the trunk according to the sawing layout.
Consequently, the present invention is characterized in that informa-
tion, such as a trunk prognosis, collected of a single tree trunk under
manipulation into the system of the forest machine is used for estimat-
ing by prediction in advance those power levels of the actuators of the
forest machine, which will be required for the operations to be carried
out for the trunk. This makes it possible that, according to the invention,
it is now possible to further set the control parameters of the engine
used as the primary power source for the forest machine in a signifi-
cantly more specific manner so that one or more power levels required
for the manipulation, of, said single tree trunk are, provided as economi
cally and with as small exhaust gas emissions as possible.
According to one embodiment of the invention, for the tree trunk to be
manipulated, only the highest power level required for its manipulation
is estimated in advance, and the control parameters of the engine are
optimized in view of this single power level only.
According to another embodiment of the invention, the power levels
required for the manipulation of a tree trunk are estimated for several
operations to be carried out on the trunk separately. Such operations
include, for example, sawing for felling, feedings of the trunk required
by delimbing at the harvesting head, and cross-cuttings of the trunk.
For these operations, several values are determined for control
parameters, wherein the operation of the engine is optimized for each
trunk and further for each operation. In the most advanced embodi-
ment, each operation to be carried out for the tree trunk is performed
by using separately optimized control parameters of the engine.
In an advantageous embodiment of the invention, the engine of the
forest machine is a diesel engine, in which the fuel supply is controlled
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by an electronic control unit ECU instead of a mechanical control
device. This makes it possible to set the control parameters for the
engine in a versatile way so that the power required of the engine each
time can be produced at an optimal efficiency, for example, by select-
ing in each situation the most suitable control graph of those stored in
the electronic control unit of the engine.
Said control graphs contain informaton relating to the scheduling and
feed volumes related to the fuel supply of the engine, and the different
control graphs can thus be used to affect the efficiency of the engine
and further the maximum output to be achieved with said settings of
the engine and the behaviour of the engine in situations of sudden
changes in the load. The last mentioned adjustment, affecting the sen-
sibility of the engine to react, is commonly called droop control.
In a second embodiment of the invention, also the speed of rotation of
the engine is automatically selected by prediction according to the
situation. In a third embodiment of the invention, the operation of the
engine is optimized by actively adjusting the settings of the charger of
the engine, typically a variable geometry turbocharger (variable nozzle
turbocharger).
The present invention provides significant advantages to prior art.
Thanks to the invention, it is possible to significantly reduce the fuel
consumption of the forest machine and thereby also the exhaust gas
emissions caused by the forest machine. As the control parameters
and the speed of rotation of the engine are automatically selected to be
suitable for each situation, also the mechanical loading and wear
caused to the engine and the other devices and parts of the forest
machine are decreased, which reduces the need for maintenance of
the forest machine and prolongs the lifetime of its engine and devices.
The invention also contributes to the reduction of noise levels caused
by the forest machine, which is important for the working environment
as well as for the driver of the machine.
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In the following, the invention will be described in more detail by using,
as examples, advantageous embodiments of the invention with refer-
ence to the appended drawings, in which
5 Fig. 1 shows, in a principle view, the functions of a forest machine
of prior art,
Fig. 2 shows, in a principle view, the functions of a forest machine
according to the invention, and
Fig. 3 shows, in a principle chart, the optional torque graphs of an
engine equipped with an electronic control unit.
Figure 1 shows, in a principle view, the functions of a forest machine of
prior art. Figure 2 shows, in a corresponding manner, the functions of a
forest machine according to the invention. In Figs. 1 and 2, only such
functions are presented as examples which are essential for under-
standing the principles of the present invention. For anyone skilled in
the art, it will be obvious that in Figs. 1 and 2, the hydraulic system of
the forest machine is illustrated in a very simplified manner and not in
its entirety for all its parts but for those parts only which are necessary
for describing the principles of the invention.
In Fig. 1, the engine 10 of the forest machine, which is typically a turbo-
charged diesel engine, is arranged, according to prior art, to rotate, at a
given constant speed of rotation, a hydraulic pump 11 which provides
the main line 12 of the hydraulic system with either a given substan-
tially constant pressure level or, under a load-sensing control, a given
pressure level and volume flow. The constant pressure level is typically
applied in the use of the functions of the harvesting head 21, and there
may also be several different constant pressure levels to be selected
for different purposes. The load-sensing control is typically used in
connection with the functions of the boom 20.
The speed of rotation of the engine 10 is set to a given constant level
by means of measurement 13 of the speed of rotation and a control
device 14 for the engine. Conventionally, the measurement 13 of the
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speed of rotation and the operation of the control device 14 of the
engine are connected to a mechanical governor for the injection pump
of the diesel engine. The pressure level in the main line 12 is adjusted
by means of a pressure measurement 15 and a control device 16
affecting the hydraulic pump 11.
From the main line 12 of the hydraulic system of the forest machine,
the hydraulic power is transferred further via control valves V1-VN to
different hydraulic actuators H1-HN, such as hydraulic cylinders and
motors for the boom 20 and the harvesting head 21. The control valve
V1-VN for a single actuator H1-HN controls, on the basis of the control
signal 23 controlling the same, the volume flow and pressure of
hydraulic fluid from the main line 12 to the respective actuator accord-
ing to the operation performed by the actuator at the time. From the
control valves V1-VN, control lines are also typically coupled to the
control device 16 of the hydraulic pump 11, wherein these control lines
are used to control the hydraulic system to operate either at a given
constant pressure level or in a load-sensing way, depending on the
control valve V1-VN and the function used at the time. Said control
lines, which are not shown in Figs. 1 and 2, can be implemented either
hydraulically or electrically.
The measuring and control system 22 of the forest machine is
arranged, in ways known as such, to control the operations of the for-
est machine according to control commands 25 from the driver. By
means of measurement data 24 obtained from the harvesting head 21
and relating to the respective tree trunk subject to manipulation, the
measuring and control system 22 draws up a trunk prognosis for the
trunk to be manipulated, and by utilizing the trunk prognosis, marks the
trunk for cross-cutting, i.e., divides it in a given manner into wood prod-
ucts of different classes in length and diameter. According to the saw-
ing layout obtained on the basis of the marking for cross-cutting, the
measuring and control system 22 helps the driver, in ways known as
such, for example by adjusting the functions of the harvesting head 21
in such a way that during the delimbing and cutting of the trunk, the
trunk is automatically stopped for cross-cutting at locations complying
with the sawing layout (sawing window), wherein the driver only needs
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to accept the cutting to be performed at the proposed location. If
necessary, the driver can transfer the cutting to take place at a desired
location, if the trunk has local defects, such as crooks, which have not
been taken into account in the sawing layout complying with the trunk
prognosis.
The measuring functions of the harvesting head 21, known as such,
include the measurement of the diameter of the trunk under manipula-
tion, and the measurement of the length of the trunk during the forward
feeding of the trunk at the harvesting head 21.
The first trunk prognosis of the trunk to be manipulated is obtained
when the harvesting head 21 of the forest machine grips the upright
growing trunk at its butt end for a felling cut. At the same time, the
driver preferably enters information in the measuring and control sys-
tem 22 about the wood species of the trunk to be manipulated. The
trunk prognosis and the marking for cross-cutting can be made more
specific during the manipulation of the trunk when more detailed infor-
mation is obtained e.g. on the conicality of the trunk. When making the
trunk prognosis, the measuring and control system 22 can, in a way
known as such, utilize information stored in its memory about trunks
manipulated previously on said lot. This information can be used to
specify, for example, the estimate on the conicality of the trunk and/or
the knottiness of the trunk.
The sawing layout, made on the basis of the trunk prognosis, can, on
one hand, be based on so-called value marking for cross-cutting, to cut
as valuable pieces of the trunk as possible. On the other hand, the
sawing layout can be implemented by using so-called distribution
marking for cross-cutting, wherein the aim is to produce wood products
belonging to different classes of length and diameter in a given propor-
tion. In its simplest form, the sawing layout may be based on cutting
the trunk to pieces of equal length.
The present invention is characterized in that information collected, by
methods known as such, in the measuring and control system 22 about
the single tree trunk to be manipulated, for example a sawing layout
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made on the basis of the trunk prognosis, is utilized for the estimation
in advance of those power levels of the actuators H1-HN of the forest
machine which will be required by the manipulating operation to be car-
ried out on the trunk.
The forest machine of the invention, shown in Fig. 2, comprises a
power control system 30 implementing the method according to the
invention, which is arranged to control the functions of the engine in a
way to be described in more detail below.
The power control system 30 is connected to a data transmission con-
nection 31 with the measuring and control system 22 of the forest
machine in such a way that the properties of the tree trunk under
manipulation, determined at the beginning of its manipulation and/or
updated during its manipulation, are available to the power control
system 30. Via the data transmission connection 31, the power control
system 30 also receives information about the operations to be carried
out next to said trunk, for example via the sawing layout formed by the
measuring and control system 22. According to the invention, this
information is used by the power control system 30 to estimate the
power levels required for the manipulating operations to be carried out
on said tree trunk before said manipulating operations are started. On
the basis of this, the power control system 30 further optimizes the
functions of the engine 10 by means of the control 32 in such a way
that the suitable control parameters of the engine 10, such as the
speed of rotation level, the graphs controlling the fuel supply, the set-
tings of the supercharger, and the droop control, have been set avail-
able by prediction even before said operation is started. The timing
data required for said prediction is obtained by the power control sys-
tem 30 from the measuring and control system 22 via the data trans-
mission connection 31.
In an advantageous embodiment of the invention, the engine 10 is a
diesel engine equipped with an electronic control unit ECU, wherein the
function and nature of the engine 10 can be optimized by selecting the
most suitable of the control data stored in the form of graphs or charts
in the electronic control unit ECU.
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Figure 3 shows, in a principle view, some torque graphs M1-MN as a
function of the speed of rotation of the engine. The different torque
graphs M1-MN are obtained in a way known as such by means of con-
trol data of the fuel supply (quantity injected, timing of injection) stored
in the memory of the electronic control unit ECU. The engine can be
set to function according to a given torque graph by changing the con-
trol parameters of the engine electrically in a way known as such. With
different settings and thereby different torque graphs, the engine gives
different maximum outputs, and also the efficiency of the engine varies
according to the graph selected at the time. In addition to the different
torque graphs, the droop control of the engine can be changed electri-
cally to affect the sensitivity of the engine to react to changes in the
loading of the engine. At low droop values, the speed of rotation of the
engine can drop only a little by an increase in the load, but at high
droop values, the speed of rotation of the engine can, in a correspond-
ing manner, temporarily drop lower when the load is suddenly
increased.
If the engine 10 is a supercharged engine, preferably an engine
equipped with a turbocharger, the function of the supercharger can
also be controlled by prediction according to the invention. From
engine technology, it is known as such to use variable geometry turbo-
chargers to reduce exhaust gas emissions on the basis of exhaust gas
recirculation EGR. According to the invention, the electronic control unit
ECU of the engine can be fitted to control the operation of such a vari-
able geometry turbocharger in such a way that the supercharging pres-
sure produced by the supercharger is suitably increased in advance
before the engine is loaded. An increase in the supercharging pressure
also makes it possible to increase the fuel quantity supplied to the en-
gine faster, wherein the engine's capacity to react to changes in the
load is substantially improved.
According to the invention, for a given manipulating operation of a tree
trunk, the control parameters of the engine can be used to set, for
example, the torque graph used by the engine, the droop control, the
settings of the supercharger, as well as the level of constant speed of
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rotation to a suitable level in advance, wherein said manipulating
operation can be performed at an optimum efficiency but still avoiding
an excessive undesired variation in the speed of rotation of the engine
during said manipulating operation.
5
The control data for the fuel supply to the engine, stored in the form of
charts or graphs in the control unit ECU, are typically entered by the
engine manufacturer. These charts, which have been stored in
advance in the memory of the control unit ECU and which can be
10 selected by means of the control parameters, make it possible to test
the emission and noise levels of the engine at different modes and
have them approved in advance by authorities.
However, the invention is not limited solely to the selection of various
15 pre-programmed charts and graphs stored in advance in the control
unit ECU, but it is also possible that the control parameters are used to
directly affect the fuel injection quantities, the timing of injection, or the
setting of the supercharger in real time. In such an embodiment, the
power control system 30, in a way, assumes some of the functions
which are normally performed by the control unit ECU.
When the tree trunk under manipulation is, for example, sufficiently
small, it is possible, according to the invention, to reduce the constant
speed of rotation of the engine 10. The advantage of this embodiment
is that when the speeds of rotation of the engine 10 and the hydraulic
pump 11 are reduced, losses and wear which are caused in them, for
example by friction, are also reduced. Also, the noise caused by the
devices at lower speeds of rotation is at a significantly lower level.
In the simplest embodiment of the invention, the control parameters of
the engine 10 and the maximum power level determined by means of
them are set constant for the time of the whole harvesting of a single
tree trunk. Alternatively, the control parameters of the engine can be
changed separately, for example for the felling, delimbing and cross-
cutting of a single tree trunk.
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By means of the invention, it is also possible to determine the power
levels required for moving the boom and the control parameters of the
engine, optimized for their production, in a situation in which the boom
is moved when the harvesting head has gripped the trunk to be
manipulated. The weigt of the trunk and thereby the power levels
required for moving it can be estimated, for example, on the basis of
the trunk prognosis and the wood species. In cross-cutting, the change
in the weight of the remaining trunk can be estimated by means of the
trunk prognosis when the cross-cutting of the trunk proceeds according
to the sawing layout.
In its simplest form, the automatic selection of the control parameters
of the engine of the forest machine according to the invention can be
made, for example, solely on the basis of the felling diameter of the
trunk and/or the wood species of the trunk. In more advanced optimi-
zation according to the invention, the selection of the power levels is
made on the basis of the trunk prognosis and/or the sawing or
manipulating layout of the trunk, derived from the trunk prognosis.
In the control of the engine of the forest machine, preferably the delays
in the different control methods are taken in account. The selection of
the different torque graphs M1-MN or droop values by electrically
affecting the electronic control unit ECU is fast and has a substantially
immediate effect on the function of the engine. Compared with the
above-mentioned variables, the effect of adjusting the speed of rotation
of the diesel engine is distinctly slower, the delay in major changes in
the speed of rotation being even in the order of a few seconds. In the
change of the settings of the supercharger and the supercharging
pressure, the delays typically fall in the middle ground between the
above-mentioned delays.
Naturally, it is obvious that if the power control system is utilized when
the forest machine is transferred from one harvesting location to
another, it is possible to select control parameters for the engine which
are economically suitable for the transport. The selection of the power
level and thereby the control parameters of the engine can also be
made by the driver of the forest machine who may, in certain situations,
CA 02486278 2004-11-17
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set edge conditions for the automatic control of the engine by the
power control system 30, or the driver may also, if necessary, manually
by-pass the power control system 30, forcing the forest machine to a
specific power control mode.
In one embodiment of the invention, the power control system 30 is
arranged to give the driver of the forest machine feedback of the fuel
consumption of the forest machine, wherein the driver is motivated to
work in such a way that the fuel consumption remains as low as possi-
ble.
By the present invention, it is possible to significantly reduce the fuel
consumption of the forest machine per produced cubic metre of timber.
This reduces the operating costs of the machine, but furthermore, par-
ticularly the emissions from the forest machine to the environment are
also distinctly reduced. This is important, because in view of the whole
life cycle of the forest machine, about 80 % of the environmental load
caused by the forest machine is due to emissions from the diesel
engine. Furthermore, the invention also reduces the loading and wear-
ing of the engine and devices of the forest machine, as well as reduces
the noise level caused by the forest machine.
By combining the modes and system structures presented in connec-
tion with the above embodiments of the invention, it is possible to pro-
vide various embodiments of the invention which comply with the spirit
of the invention. Therefore, the above-presented examples must not be
interpreted as restrictive to the invention, but the embodiments of the
invention can be freely varied within the scope of the inventive features
presented in the claims hereinbelow.
For example, it is obvious that in the estimation of the power levels
required by the operations to be carried out on the tree trunk, these
power levels do not need to be determined, for example, in kilowatts or
corresponding absolute values, but it is also possible to use other
parameters which describe the power demand and the loading of the
engine caused by the operation.
