METHOD FOR COMBINED PREHEATING AND COOLING OF A COOLANT

METHODE DE PRECHAUFFAGE ET REFROIDISSEMENT COMBINES D'UN FLUIDE REFROIDISSEUR

English Abstract

The invention concerns a method for cooling a coolant for
waste heat cooling of an internal combustion engine in an
agricultural working vehicle, wherein a heat exchanger
through which coolant flows and air delivery means to
generate an air flow through the heat exchanger are
provided.

Claims

CLAIMS:
1. Method for combined preheating and cooling of a
coolant for waste heat cooling of an internal
combustion engine in an agricultural working
vehicle, wherein a heat exchanger through which
coolant flows and air delivery means to generate an
air flow through the heat exchanger are provided,
and the air delivery means is configured so as to
generate the air flow in a direction towards the
internal combustion engine or in a direction away
from the internal combustion engine as required,
wherein the air delivery means is set to generate an
air flow in the direction away from the internal
combustion engine as long as a temperature value,
which is characteristic of the temperature state of
the internal combustion engine, lies below a
threshold value, and the air delivery means is set
reversed when the status value is exceeded.
2. Method for combined preheating and cooling of a
coolant according to Claim 1, characterized in that
the threshold value is at the level of the operating
temperature of the internal combustion engine.
3. Method for combined preheating and cooling of a
coolant according to Claim 1 or 2, characterized in
that the air delivery means is a fan with electric
or hydraulic drive.
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Description

Mk 02908153 2015-10-09
Method for Combined Preheating and Cooling of a Coolant
The invention concerns a method for cooling a coolant for
waste heat cooling of an internal combustion engine in an
agricultural working vehicle, wherein a heat exchanger
through which coolant flows and air delivery means to
generate an air flow through the heat exchanger are
provided.
Fluid-based cooling systems for waste heat cooling of an
internal combustion engine are normally designed such
that the cooling circuit is divided via a coolant
thermostat into a secondary cooling circuit, also called
the bypass circuit, and a main cooling circuit. In
principle, during the warm-up phase, the coolant
thermostat is in a position in which the flow of coolant
in the main cooling circuit through the heat exchanger,
also called the engine radiator, is blocked and a coolant
flow through a coolant line bypassing the heat exchanger
is opened. The associated reduction in circulated coolant
leads to a faster passage through the warm-up phase, and
the operating temperature of the internal combustion
engine is reached earlier. In the region of the so-called
switching temperature of the coolant thermostat, the
bypass coolant line is closed to the extent that the flow
through the heat exchanger is opened. Also, coolant not
yet heated is thus included in the coolant circuit and
must be heated to a higher temperature. This leads to a
brief fall in the temperature of the coolant circuit.
Furthermore, the warm-up phase always lasts for a
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specific duration, whereas the temperature in the engine
bay in which the internal combustion engine is placed
exceeds the ambient temperature relatively soon after the
cold start.
The object of the present invention is to improve a
cooling system such that a further shortened warm-up
phase of the internal combustion engine is achieved.
This object is achieved by a method for combined
preheating and cooling of a coolant for waste heat
cooling of an internal combustion engine in an
agricultural working vehicle, wherein a heat exchanger
through which coolant flows and air delivery means to
generate an air flow through the heat exchanger are
provided, and the air delivery means is configured so as
to generate the air flow in a direction towards the
internal combustion or in a direction away from the
internal combustion engine as required, wherein the air
delivery means is set to generate an air flow in the
direction away from the internal combustion engine as
long as a temperature value, which is characteristic of a
temperature state of the internal combustion engine, lies
below a threshold value, and the air delivery means is
set reversed when the status value is exceeded.
The method according to the invention is advantageously
able to exploit the temperature difference which can
occur after a cold start of the internal combustion
engine, during the warm-up phase between the ambient
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temperature and the engine bay temperature. Since usually
at the moment of cold start, the coolant in the heat
exchanger is at the level of the ambient temperature,
during the warm-up phase a temperature difference exists
between the coolant in the heat exchanger and the engine
bay. The method according to the invention firstly
achieves that, on reaching the switching temperature of
the coolant thermostat, i.e. on opening of the flow
through the heat exchanger or the main cooling circuit,
there is no or at least only a reduced brief temperature
fall in the coolant circuit. Furthermore, the method
according the invention shortens the duration of the
warm-up phase since an additional heat input into the
coolant circuit takes place during the warm-up phase. It
is decisive that this heat input comes from a heat
source, for example the exhaust manifold, the emitted
heat of which is not normally used for any other purpose.
To this extent, the efficiency of the internal combustion
engine increases during the warm-up phase.
Preferably, the threshold value is at the level of the
operating temperature of the internal combustion engine.
This ensures that as far as possible, the entire warm-up
phase is used to guide air, which has already been heated
in the engine bay, through the heat exchanger.
Preferably, the air delivery means is a fan with electric
or hydraulic drive. This is simple to install in a
cooling system.
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The present invention is described with reference to the
figures below. These show:
Figure 1 an agricultural working vehicle with a cooling
system controlled according to the prior art,
and
Figure 2 an agricultural working vehicle (extract) with
a cooling system controlled according to the
invention.
Figure 1 shows an agricultural working vehicle 12,
depicted purely diagrammatically in parts, with a cooling
system 10 arranged in a frontal area, for waste heat
cooling of an internal combustion engine 20 placed in the
engine bay 18. The agricultural working vehicle 12
furthermore comprises a cab 14, a front axle 16 and a
rear axle 22 driven by the internal combustion engine 20.
A frame 24 serves a carrier element for the individual
components of the working vehicle 12.
To dissipate the heat developed during operation of the
internal combustion engine 20, the cooling system 10
comprises a heat exchanger 28 through which coolant flows
and over which air flows, and the air delivery means 32
generating the air flow, in the form of a fan. Both the
heat exchanger 28 and the fan 32 may be arranged at the
front of the internal combustion engine 20 in the travel
direction of the working machine 12. The fan 32 may also
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be arranged between the internal combustion engine 20 and
the heat exchanger 32.
In the exemplary embodiment shown and described here, the
fan 32 may be driven about a rotation axis D by a
hydraulic motor 30, which in turn may be supplied by a
hydraulic pump 26 driven by the internal combustion
engine 20. According to the invention, it is proposed
that the fan 32 can be driven by the hydraulic motor 30
both in the one rotation direction and in the opposite
rotation direction as required. In figure 1, the air flow
generated by the fan 32 is depicted by arrows which
represent a flow direction of the air flow from the
environment through the heat exchanger 28 and into the
engine bay 18. The fan 32 is thus set and driven in the
rotation direction in which, at least when the internal
combustion engine 20 is at operating temperature, an air
flow is generated which acts as a cooling air flow from
the environment into the engine bay 18.
In figure 2, the fan 32 is set and driven in the opposite
rotation direction, so that an air flow is generated out
of the engine bay 18, through the heat exchanger 28 and
into the environment. In this rotation direction, here
called the opposite direction, the fan 32 is set
according to the invention immediately after the cold
start and during the subsequent warm-up phase of the
internal combustion engine 20. The term "cold start" in
the context of this application means a state in which a
temperature level of the internal combustion engine 20,
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CA 02908153 2015-1()-09
which is represented for example by the coolant
temperature or the engine oil temperature, lies
significantly below the operating temperature of the
internal combustion engine 20, wherein the operating
temperature is usually characterized by a coolant
temperature between 80 C and 100 C or an engine oil
temperature between 90 C and 110 C.
To perform the method according to the invention, first a
coolant temperature sensor, an engine oil temperature
sensor and an external temperature sensor present on the
agricultural working vehicle 12 detect whether a cold
start state exists. If a cold start state exists, after
the cold start of the internal combustion engine 20, the
fan 32 is set and driven in the opposite direction of
rotation so that an air flow is generated from the engine
bay 18, through the heat exchanger 28 and into the
environment. Since the exhaust manifold quickly becomes
hot after a cold start of the internal combustion engine
20, this heats the engine bay 18 rapidly relative to the
ambient temperature. On performance of the method
according to the invention, this increased temperature is
used to heat the coolant present in the heat exchanger 28
before the coolant thermostat has reached its switching
temperature and opened the flow through the main cooling
circuit. When the internal combustion engine 20 has
reached its operating temperature, the rotation direction
of the fan is reversed, and it is set and driven in the
rotation direction in which an air flow is generated
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which acts as a cooling air flow out of the environment
into the engine bay 18.
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List of Reference Numerals
Cooling system
12 Agricultural working vehicle
5 14 Cab
16 Front axle
18 Engine bay
Internal combustion engine
22 Rear axle
10 24 Frame
26 Hydraulic pump
28 Heat exchanger
Hydraulic motor
32 Fan
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Representative Drawing