JP2018048562A - Cooling device for direct-injection engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cooling device for a direct-injection engine capable of optimizing cooling of fuel by supplying cooling water to a fuel cooler without excess and shortage and of preventing failure caused by an inappropriate fuel temperature.SOLUTION: Request heat radiation amount Qb to an intercooler 22 is calculated, and based on necessary cooling water amount required to achieve the request heat radiation amount Qb, a drive duty of a water pump 38 is set (S1). When a determination that a fuel temperature Tfd in a delivery pipe 13 exceeds a determination value Tfd0 so as to require cooling is made (S3), request heat radiation amount Qa to a fuel cooler 29 is calculated, and necessary cooling water amount required to achieve the request heat radiation amount Qa is calculated (S5). Based on the necessary cooling water amount, the drive duty of the water pump 38 is calculated, and increase correction of the drive duty in Step S1 only by the drive duty is performed (S6). Corresponding to a ratio of the necessary cooling water amount between the fuel cooler 29 and the intercooler 22, an opening of the flow control valve 37 is set (S7).SELECTED DRAWING: Figure 2

Description

  The present invention relates to a direct-injection engine cooling apparatus, and more particularly, to a direct-injection engine cooling apparatus including a fuel cooler that cools fuel supplied to an in-cylinder injector.

In a direct injection engine that injects fuel into a cylinder, since the injector is disposed so as to face the cylinder, combustion heat in the cylinder is directly transmitted to the injector. As a result, the temperature of the injector rises and the magnetic field reproducibility of the solenoid decreases, and an error occurs in the fuel injection amount, resulting in variations in the air-fuel ratio between the cylinders.
In view of such a problem, measures for cooling the fuel supplied to the injector have been proposed. For example, in the technique described in Patent Document 1, a water jacket is provided in a delivery pipe that distributes and supplies fuel to the injectors of each cylinder, and a fuel cooler is configured such that cooling water supplied from a water pump is circulated through the water jacket. doing. The fuel cooler cools the fuel in the delivery pipe, thereby suppressing the temperature rise of the injector.

JP-A-5-202821

  Since the fuel cooler described in Patent Document 1 simply has a configuration in which cooling water is circulated through the water jacket, the cooling action received by the fuel in the delivery pipe is uniform regardless of the operating state of the engine and the like. However, the combustion heat in the cylinder of the engine changes every moment according to the operating state and the like, and accordingly, the temperature rise of the injector, and hence the heat radiation amount of the fuel cooler required for suppressing the temperature rise also increases or decreases. According to the technique of Patent Document 1, in order to avoid insufficient cooling due to insufficient cooling water supply, assuming that the temperature rise of the injector is the most severe, the amount of cooling water supplied to the fuel cooler (releasing the fuel cooler) Amount of heat) must be set.

For this reason, for example, even in an engine operating state that does not require cooling of the injector, the water pump is driven to supply sufficient cooling water to the fuel cooler. If it exists, a drive loss etc. will arise.
The present invention has been made in order to solve such problems. The object of the present invention is to supply cooling water to a fuel cooler that cools the fuel and suppresses the rise in the temperature of the injector. Accordingly, an object of the present invention is to provide a cooling device for a direct injection engine that can optimize the cooling of the fuel and prevent various problems caused by an inappropriate fuel temperature.

  In order to achieve the above object, a cooling device for a direct injection engine according to the present invention is disposed in a fuel path of an injector that injects fuel into a cylinder, and cools the fuel supplied to the injector by circulation of cooling water. The fuel cooler, flow rate adjusting means capable of adjusting the flow rate of cooling water supplied to the fuel cooler, and the fuel cooler required for cooling the fuel supplied to the injector based on the operating state of the direct injection engine. And a cooling control means for controlling the flow rate adjusting means on the basis of the required heat release amount calculated by the heat release amount calculation means (claim 1). .

According to the direct-injection engine cooling apparatus configured as described above, since the flow rate adjusting means is controlled based on the required heat dissipation amount of the fuel cooler for cooling the fuel, the cooling water is supplied to the fuel cooler without excess or deficiency. Cooling is optimized.
As another aspect, the flow rate adjusting means is at least one of a water pump that discharges cooling water supplied to the fuel cooler or a flow rate control valve that controls a flow rate of cooling water discharged from the water pump, It is preferable that the cooling control means controls the rotational speed of the water pump or the opening degree of the flow rate control valve based on the required heat radiation amount to the fuel cooler.

According to this aspect, the rotational speed of the water pump and the opening degree of the flow control valve are controlled based on the heat radiation amount required for the fuel cooler.
As another aspect, the direct injection engine is provided with a water-cooled intercooler of a turbocharger, and the flow rate adjusting means discharges the cooling water, and the cooling water discharged from the water pump is supplied to the fuel cooler side. And the intercooler side can be distributed at an arbitrary ratio, and the cooling control means is configured to control the rotational speed of the water pump and the flow rate control based on the heat radiation amount required for the fuel cooler and the intercooler. It is preferable to control the distribution ratio of the cooling water by the valve.

According to this aspect, since the water pump rotation speed and the distribution ratio of the cooling water by the flow rate control valve are controlled based on the heat radiation required for the fuel cooler and the intercooler, in addition to the cooling of the fuel by the fuel cooler, The intake air cooling by the intercooler is also optimized.
As another aspect, the heat dissipation amount calculating means is based on a difference between an actual heat amount of fuel supplied to the injector and a heat amount of fuel at a preset target temperature while the direct injection engine is stopped. Calculate the required heat dissipation amount to the fuel cooler, and subtract the amount of heat lost by fuel injection into the cylinder from the difference between the actual heat amount and the heat amount at the target temperature during operation of the direct injection engine. It is preferable to calculate a required heat radiation amount to the fuel cooler (claim 4).

According to this aspect, it is possible to calculate an appropriate required heat radiation amount regardless of whether the engine is operating or stopped.
As another aspect, the engine further comprises an idle stop control means for automatically stopping the direct injection engine based on establishment of a predetermined stop condition, and then automatically starting the direct injection engine based on establishment of a predetermined start condition. Preferably, the calorific value calculating means calculates a required heat radiation amount to the fuel cooler based on a difference between the actual calorific value and the calorific value at the target temperature during the automatic stop of the direct injection engine by the idle stop control means. (Claim 5).

According to this aspect, it is possible to calculate an appropriate required heat radiation amount even during the automatic stop of the direct injection engine by the idle stop control means.
As another aspect, the cooling control means is configured such that the temperature of the fuel supplied to the injector is equal to or lower than a first determination value set in advance, or the second determination in which the fuel injection amount of the injector is set in advance. It is preferable that supply of the cooling water to the fuel cooler is stopped by the flow rate adjusting means when any of the cases where the value is exceeded (Claim 6).

  According to this aspect, when the temperature of the fuel supplied to the injector is equal to or lower than the first determination value, it is considered that cooling of the fuel by the fuel cooler is unnecessary, and the fuel injection amount of the injector exceeds the second determination value. In this case, the temperature of the fuel is significantly lowered due to the fuel injection into the cylinder, so that the cooling by the fuel cooler is considered unnecessary, and in any case, the supply of the cooling water to the fuel cooler is stopped.

  According to the cooling device for a direct injection engine of the present invention, the cooling water is supplied to the fuel cooler that cools the fuel and suppresses the rise in the temperature of the injector, thereby optimizing the cooling of the fuel and improper fuel. Various problems due to temperature can be prevented in advance.

It is a whole lineblock diagram showing the direct injection gasoline engine to which the cooling device of an embodiment was applied. It is a flowchart which shows a cooling control routine at the time of engine operation which ECU performs during operation of an engine. It is a flowchart which shows the cooling control routine at the time of an engine stop which ECU performs during an automatic stop of an engine.

Hereinafter, an embodiment in which the present invention is embodied in a cooling device for a direct injection gasoline engine will be described.
FIG. 1 is an overall configuration diagram showing a direct injection gasoline engine to which the cooling device of the present embodiment is applied.
A direct injection engine 1 (hereinafter simply referred to as an engine) of the present embodiment is mounted on a vehicle (not shown) as a driving power source. Pistons 4 are disposed in the cylinders 3 of the respective cylinders formed in the cylinder block 2 of the engine 1, and the pistons 4 slide in the cylinders 3 according to the rotation of the crankshaft 5. The intake valve 6 and the exhaust valve 7 of each cylinder are driven in synchronization with the rotation of the crankshaft 5, thereby opening and closing the intake port 8 and the exhaust port 9 at a predetermined crank angle.

  Each cylinder of the engine 1 is provided with a spark plug 10 and an injector 11 so as to face the cylinder, and the spark plug 10 is ignited by driving an igniter 12. The injectors 11 of the respective cylinders are connected to a common delivery pipe 13, and fuel (gasoline) pressurized by a high-pressure pump 15 is supplied into the delivery pipe 13 through a fuel path 14. Distribution and supply to the injectors 11 of the cylinders.

A surge tank 18 is connected to the intake port 8 of each cylinder via an intake manifold 17, and a downstream end of an intake passage 19 is connected to the surge tank 18. An air cleaner 20, a compressor 21 a of a turbocharger 21, an intercooler 22, and a throttle valve 23 are provided in the intake passage 19 from the upstream side.
The exhaust port 9 of each cylinder is connected to an upstream end of an exhaust passage 25 via an exhaust manifold 24. The exhaust passage 25 is provided with a turbine 21b of the turbocharger 21, a catalyst device 26, and a silencer (not shown). Yes.

  During the operation of the engine 1, the intake air introduced from the air cleaner 20 into the intake passage 19 is pressurized by the compressor 21 a of the turbocharger 21, cooled by the intercooler 22, adjusted in flow rate by the throttle valve 23, and further surge tank 18 is distributed to each cylinder by the intake manifold 17 and introduced into the cylinder of the engine 1 when the intake valve 6 is opened. During intake in the cylinder, fuel is injected from the injector 11 at a predetermined crank angle and ignited by the spark plug 10, and the crankshaft 5 is rotationally driven via the piston 4 by the generated combustion pressure.

The exhaust gas after combustion in the cylinder of each cylinder is discharged to the exhaust port 9 when the exhaust valve 7 is opened, collected by the exhaust manifold 24, guided to the exhaust passage 25, and driving the turbine 21 b of the turbocharger 21. It is discharged to the outside through the catalyst device 26 and the silencer.
On the other hand, in the cooling device of the present embodiment, the fuel supplied to the injector 11, the intercooler 22, and the bearing portion 21c of the turbocharger 21 are targets for cooling, and a cooling circuit 28 (circulating cooling water for cooling them) ( Hereinafter referred to as an auxiliary machine cooling circuit). The auxiliary machine cooling circuit 28 is formed in a separate system from a known engine cooling circuit that circulates cooling water to and from the radiator in order to cool the engine 1.

  As described in [Background Art], the cooling of the fuel to the injector 11 is aimed at suppressing the temperature rise of the injector 11 due to the heat received from the cylinder. For this purpose, the fuel is distributed to the injector 11 of each cylinder. The supplied delivery pipe 13 is provided with a fuel cooler 29. The water jacket 29a of the fuel cooler 29 is formed so as to surround the periphery of the delivery pipe 13, and the fuel in the delivery pipe 13 is cooled by the cooling water flowing through the water jacket 29a via the accessory cooling circuit 28 described above. Then, the cooled fuel is injected into the cylinder through the injector 11, thereby suppressing the temperature rise of the injector 11.

Cooling of the fuel by the fuel cooler 29 is, of course, necessary during operation of the engine 1 in which combustion occurs in the cylinder. Even during automatic stop of the engine 1 in idle stop control, which will be described later, it is possible to receive heat from the engine 1. Since the temperature of the fuel in the delivery pipe 13 rises, cooling is necessary.
The intercooler 22 is configured as a water-cooled type, and the intake air flowing through the intercooler 22 in another path is cooled by the cooling water flowing through the intercooler 22 via the auxiliary machine cooling circuit 28. In addition, since the circulation of the intake air in the intercooler 22 is interrupted while the engine is stopped, the cooling is unnecessary.

  As is well known, the compressor 21a and the turbine 21b of the turbocharger 21 are rotatably supported coaxially by a bearing portion 21c, and the bearing portion 21c is lubricated and cooled by supplying engine oil during engine operation. The turbocharger 21 of this embodiment further has a cooling function of the bearing portion 21c using cooling water. For this reason, although not shown, a water jacket is formed in the vicinity of the bearing portion 21c, and this water jacket is supplemented. The bearing water 21c is cooled by the circulation of the cooling water passing through the machine cooling circuit 28.

  The purpose of cooling the bearing portion 21c with the cooling water is to prevent seizure of the bearing portion 21c when the supply of engine oil is stopped by stopping the engine. For this reason, the cooling of the bearing portion 21c with the cooling water is required immediately after the engine is stopped. Especially, immediately after the high load operation, the bearing is opposed to the engine body or the turbine 21b due to a large amount of heat transmitted from the engine body or the turbine 21b. Since the temperature of the part 21c rises, sufficient cooling with cooling water is required.

Auxiliary equipment cooling circuit 28 is formed to allow the coolant to flow through the fuel cooler 29, the intercooler 22 and the bearing portion 21c of the turbocharger 21 according to the situation, and the configuration thereof will be described below.
The radiator 31 of the auxiliary machine cooling circuit 28 is installed in, for example, the engine room of the vehicle together with the radiator of the engine cooling circuit, and dissipates the cooling water flowing through the interior to the outside air by running air or fan blowing. Yes.

  The auxiliary machine cooling circuit 28 includes a first water passage 32 that connects the outlet of the radiator 31 and the fuel cooler 29, a second water passage 33 that connects the fuel cooler 29 and the bearing portion 21 c of the turbocharger 21, and a bearing portion of the turbocharger 21. A third water passage 34 that connects 21c and the inlet of the radiator 31, a fourth water passage 35 that connects the intercooler 22 with a flow rate control valve 37 (flow rate adjusting means) interposed in the middle of the first water passage 32, and an intercooler. 22 and a fifth water channel 36 connecting the middle part of the second water channel 33. A check valve 39 is interposed on the second water passage 33 to prevent the backflow of cooling water from the turbocharger 21 side to the fuel cooler 29 side.

  An electric water pump 38 (flow rate adjusting means) driven by a motor (not shown) is interposed from the flow rate control valve 37 of the first water channel 32 to the radiator 31 side, and the cooling water discharged from the water pump 38 is It circulates in the auxiliary machine cooling circuit 28. The rotational speed of the water pump 38 is increased or decreased by the duty control of the motor, and the discharge amount of the cooling water from the water pump 38 and the circulation amount of the cooling water in the auxiliary machine cooling circuit 28 can be arbitrarily adjusted accordingly. ing.

  The flow control valve 37 has a function capable of distributing the cooling water from the water pump 38 to the fuel cooler 29 side and the intercooler 22 side at an arbitrary ratio (100: 0 to 0: 100). In the following description, the opening degree of the flow rate control valve 37 when supplying cooling water to both the fuel cooler 29 and the intercooler 22 is an intermediate position, and the opening degree when supplying cooling water only to the fuel cooler 29 is the fuel cooler position. (100: 0), an opening when supplying cooling water only to the intercooler 22 is expressed as an intercooler position (0: 100).

  In addition, the installation location and function of the flow control valve 37 are not limited to the above. For example, the flow control valve 37 is provided on the downstream side of the fuel cooler 29 side and the intercooler 22 side from the branch location of the first water channel 32 and the fourth water channel 35. A flow rate control valve (flow rate adjusting means) capable of adjusting the opening degree of the water channels 32 and 35 may be provided. Even in this case, the distribution ratio of the cooling water to the fuel cooler 29 and the intercooler 22 can be arbitrarily adjusted according to the opening degree of both flow control valves.

  With the configuration of the auxiliary machine cooling circuit 28 described above, the cooling water discharged from the water pump 38 flows into the flow control valve 37 through the first water channel 32. When the flow control valve 37 is in the intermediate position, the cooling water is distributed at a predetermined ratio to both the fuel cooler 29 side and the intercooler 22 side, supplied to the fuel cooler 29 via the first water channel 32, and the fourth water channel 35. And supplied to the intercooler 22.

  The cooling water after cooling the fuel in the water jacket 29a of the fuel cooler 29 flows through the second water passage 33, while the cooling water after cooling the intake air in the intercooler 22 flows through the fifth water passage 36, and After joining, it flows into the bearing portion 21c of the turbocharger 21. The cooling water after cooling the bearing portion 21c is returned to the radiator 31 through the third water passage 34, and is discharged from the water pump 38 again after the temperature is lowered due to heat radiation to the outside air. Repeat within.

When the flow control valve 37 is in the fuel cooler position, the cooling water is supplied to the fuel cooler 29 via the first water passage 32 to cool the fuel, and the bearing 21 c of the turbocharger 21 is cooled via the second water passage 33. Then, it flows into the radiator 31 through the third water channel 34.
When the flow control valve 37 is in the intercooler position, the cooling water is supplied to the intercooler 22 through the first water passage 32 and the fourth water passage 35 to cool the intake air, and the turbocharger passes through the fifth water passage 36 and the second water passage 33. The bearing 21 c of 21 is cooled, and then returned to the radiator 31 through the third water channel 34.

  An ECU 41 (engine control unit) provided with an input / output device (not shown), a storage device (ROM, RAM, etc.) used for storing control programs, control maps, a central processing unit (CPU), a timer counter, etc. ) Is installed, and comprehensive control of the engine 1 is performed. On the input side of the ECU 41, an intake air temperature sensor 42 for detecting the intake air temperature Ta of the engine 1, an intake air amount sensor 43 for detecting the intake air amount Ga, a fuel temperature sensor 44 for detecting the fuel temperature Tfd in the delivery pipe 13, and a delivery pipe Various sensors such as a fuel pressure sensor 45 for detecting the fuel pressure Pfd in the engine 13, an oil temperature sensor 46 for detecting the outlet oil temperature To of the turbocharger 21, and an IC downstream temperature sensor 47 for detecting the IC downstream temperature Tb after flowing through the intercooler. Is connected.

Also, various devices such as the injector 11, the igniter 12 of the spark plug 10, the flow control valve 37 of the auxiliary machine cooling circuit 28, and the water pump 38 are connected to the output side of the ECU 41.
The ECU 41 determines an ignition timing, a fuel injection amount, and the like based on detection information from each sensor, and operates the engine 1 by drivingly controlling an igniter and an injector based on the determined target value.

The ECU 41 executes idle stop control (idle stop control means). As is well known, the control automatically stops the engine 1 when a predetermined stop condition such as a brake operation is satisfied when the vehicle is temporarily stopped such as waiting for a signal, and the engine 1 when a predetermined start condition such as stop of the brake operation is satisfied. Is automatically started.
Further, the ECU 41 cools the coolant that circulates through the auxiliary machine cooling circuit 28 according to the operating state of the engine 1 through the fuel cooler 29, the intercooler 22, and the bearing portion 21 c of the turbocharger 21 as appropriate.

  As described in [Problems to be Solved by the Invention], the technique disclosed in Patent Document 1 does not consider the amount of cooling water supplied to the fuel cooler 29, which is one of the objects to be cooled. There has been a problem that the temperature rise of the injector 11 cannot be suppressed due to insufficient supply of water, or conversely, the power consumption of the motor driving the water pump 38 is wasted due to excessive supply of cooling water.

  In view of the demand for such a cooling device, in this embodiment, after selecting devices that require cooling in accordance with the operating state of the engine 1, an appropriate amount of cooling water that is not excessive or insufficient is distributed to those devices. To achieve this, the rotational speed of the water pump 38 (the pump discharge amount, in other words, the circulation amount of the cooling water in the auxiliary machine cooling circuit 28) and the opening of the flow control valve 37 (the fuel cooler 29 side and the intercooler 22 side) The cooling water distribution ratio). Hereinafter, specific control by the ECU 41 will be described, but prior to that, what kind of knowledge the control is based on will be described.

Basically, a device that needs to be cooled is selected based on the operating state of the engine 1, and the flow rate of the cooling water to each selected device is controlled based on the required heat radiation amount to each device.
First, a device that needs to be cooled is different between the operation of the engine 1 and the automatic stop by the idle stop control.

  As described above, during the operation of the engine 1, the fuel cooler 29 needs to be cooled in order to suppress the temperature rise of the injector 11, and the intercooler 22 needs to be cooled in order to cool the intake air. However, since the bearing portion 21c of the turbocharger 21 is lubricated and cooled by engine oil and cooled by the intake air flowing through the compressor 21a, the requirement for heat damage is somewhat relaxed compared to the automatic stop by the idle stop control. Is done.

Accordingly, the flow rate control valve 37 at this time is switched to the intermediate position (exceptionally there is an intercooler position as in the flowchart described later), and the cooling water is supplied to both the fuel cooler 29 and the intercooler 22. At this time, the cooling water also flows through the bearing portion 21c of the turbocharger 21 located on the downstream side, but this is not intended for the main purpose.
Further, while the engine 1 is automatically stopped, it is still necessary to cool the fuel by the fuel cooler 29. However, since the intake air does not flow through the intercooler 22, cooling is unnecessary. On the other hand, since the supply of engine oil to the bearing portion 21c of the turbocharger 21 and the intake air flow of the compressor 21a are stopped, cooling with cooling water is necessary.

Therefore, the flow control valve 37 at this time is switched to the fuel cooler position, and the cooling water is distributed only to the fuel cooler 29 (there is an exceptional supply stop as shown in the flowchart described later), and inevitably the downstream turbo Cooling water also flows through the bearing portion 21c of the charger 21.
On the other hand, the required heat dissipation amount to each device is calculated based on the following viewpoints, and the water pump 38 and the flow rate control valve 37 are controlled based on the flow rate of cooling water that can achieve this required heat dissipation amount.

First, the amount of heat required for the fuel cooler 29 can be basically expressed as a divergence between the actual heat amount of the fuel in the delivery pipe 13 and the heat amount of the fuel at a preset target temperature. The deviation is eliminated by achieving the required heat dissipation by cooling.
However, during operation of the engine 1, relatively high temperature fuel flows out from the delivery pipe 13 due to fuel injection into the cylinder, and relatively low temperature fuel flows into the delivery pipe 13. As a result, a phenomenon in which heat is taken away from the fuel in the delivery pipe 13 occurs, and the required heat radiation amount is reduced by the temperature drop.

Therefore, the required heat radiation amount Qa to the fuel cooler 29 during engine operation is expressed by the following equation (1).
Qa = {C1 * (Tfd-Tfdtgt) * C2 * Vd} -C2 * q * (Tfd-Tft) (1)
Here, C1 is a constant, Tfd is the fuel temperature in the delivery pipe 13 detected by the fuel temperature sensor 44, Tfdtgt is the target temperature of the fuel, C2 is the specific heat of the fuel, Vd is the internal volume of the delivery pipe 13, and q is the injector 11. , Tft is the fuel temperature in the fuel tank. In addition, since it is necessary to add a sensor in the fuel tank to detect the fuel temperature Tft in the tank, the intake air temperature Ta (that is, the outside air temperature) detected by the intake air temperature sensor 42 may be simply applied.

Further, during the automatic engine stop when the fuel injection into the cylinder is stopped as described above, the fuel does not enter or leave the delivery pipe 13, so that the required heat radiation amount Qa to the fuel cooler 29 is expressed by the following equation (2 ).
Qa = C1 × (Tfd−Tfdtgt) × C2 × Vd (2)
The injection quantity q of the injector 11 is expressed by the following equation (3).

q = C3 × Pfd × Pw (3)
Here, C3 is a constant, Pfd is the fuel pressure in the delivery pipe 13 detected by the fuel pressure sensor 45, and Pw is an injection pulse when the ECU 41 drives the injector 11 under engine control.
Further, the required heat radiation amount Qb to the intercooler 22 is expressed by the following equation (4).

Qb = C4 × (Tb−Tbtgt) × Ga (4)
Here, C4 is a constant, Tb is the IC downstream temperature Tb detected by the IC downstream temperature sensor 47, Tbtgt is the target downstream temperature, and Ga is the intake air amount detected by the intake air amount sensor 43.
The target downstream temperature Tbtgt is a target value of the IC downstream temperature Tb when the amount of cooling water flowing to the intercooler 22 is controlled by engine control. However, the target downstream temperature Tbtgt is not limited to this and is a fixed value set in advance. Also good.

Further, the required heat radiation amount Qc to the bearing portion 21c of the turbocharger 21 is expressed by the following equation (5).
Qc = C5 x (To-Totgt) (5)
Here, C5 is a constant, To is the outlet oil temperature of the turbocharger 21 detected by the oil temperature sensor 46, and Totgt is the target oil temperature.

The target oil temperature Totgt is a control value that takes into account the engine oil temperature and the load state in engine control.
Based on the required heat dissipation amounts Qa, Qb, and Qc calculated for each device in this way, the amount of cooling water to be circulated through each device can be specified, and the rotational speed and flow rate of the water pump 38 to achieve the circulated amount. The opening degree of the control valve 37 is controlled.

Next, specific control by the ECU 41 will be described.
First, the cooling control executed during the operation of the engine 1 will be described.
FIG. 2 is a flowchart showing an engine operation cooling control routine executed by the ECU 41 during operation of the engine 1. The ECU 41 executes the routine at predetermined control intervals while the engine 1 is operating.

  First, in step S1, a required heat dissipation amount Qb to the intercooler 22 is calculated according to the above equation (4), and a cooling water amount (required cooling water amount) to be supplied to the intercooler 22 to achieve the required heat dissipation amount Qb is calculated. The drive duty of the water pump 38 that can achieve the required amount of cooling water is set. In the subsequent step S2, it is determined whether or not the IC downstream temperature Tb of the intercooler 22 is higher than the target downstream temperature Tbtgt by a preset determination value Tb0 (Tb ≧ Tbtgt + Tb0).

The process of step S <b> 2 aims to determine whether or not a part of the cooling water can be used for cooling the fuel cooler 29. When the determination in step S2 is No (negative), it is determined that there is a margin in cooling the intake air by the intercooler 22 and there is room for some cooling water to be used for cooling the fuel cooler 29, and the process proceeds to step S3.
In step S3, it is determined whether or not the fuel temperature Tfd in the delivery pipe 13 exceeds a predetermined determination value Tfd0 (first determination value) (Tfd> Tfd0). The process of step S3 aims to determine whether or not the fuel cooler 29 needs to cool the fuel. When the determination in step S3 is Yes, it is considered that cooling by the fuel cooler 29 is necessary, and the process proceeds to step S4.

  In step S4, it is determined whether or not the injection amount q of the injector 11 obtained by the above equation (3) exceeds a preset determination value q0 (second determination value) (q> q0). The process of step S4 determines whether or not the temperature drop of the fuel in the delivery pipe 13 due to fuel injection into the cylinder is significant (that is, whether or not the influence of the right side of the above equation (1) is large). With the goal. When the determination in step S4 is No, it is considered that cooling by the fuel cooler 29 is necessary because the temperature drop of the fuel due to fuel injection is small, and the process proceeds to step S5.

  In step S5, the required heat dissipation amount Qa to the fuel cooler 29 is calculated according to the above equation (1) (heat dissipation amount calculating means), and the required amount of cooling water to be supplied to the fuel cooler 29 to achieve the required heat dissipation amount Qa is calculated. calculate. In the subsequent step S6, the drive duty of the water pump 38 that can achieve the required amount of cooling water to the fuel cooler 29 calculated in step S5 is calculated, and the drive duty calculated in step S1 is increased and corrected by the drive duty. (Cooling control means).

  In the following step S7, the flow control valve 37 is set to a predetermined opening at the intermediate position so as to correspond to the ratio of the required cooling water amount to the fuel cooler 29 and the required cooling water amount to the intercooler 22 (cooling control means). . Specifically, the opening degree of the flow control valve 37 is set so that the cooling water supplied from the water pump 38 is distributed between the fuel cooler 29 side and the intercooler 22 side in the ratio of the required cooling water amount, and then the routine is executed. finish.

  The above is the basic control contents during the operation of the engine 1, and the amount of cooling water necessary for cooling both the fuel cooler 29 and the intercooler 22 is required from the viewpoint that the fuel cooler 29 and the intercooler 22 need to be cooled. Is discharged from the water pump 38 based on the setting of the drive duty in step S6, and the cooling water is distributed to the fuel cooler 29 and the intercooler 22 at a ratio based on the opening setting of the flow control valve 37 in step S7.

Therefore, both the fuel cooler 29 and the intercooler 22 achieve the desired cooling, and the fuel in the delivery pipe 13 and the intake air supplied to the engine 1 can be cooled. For this reason, the temperature rise of the injector 11 can be suppressed by fuel cooling to prevent variations in the fuel injection amount between the cylinders, and good engine performance can be maintained by cooling the intake air.
On the other hand, if the determination in step S2 is Yes, it can be considered that there is no room for cooling the intake air by the intercooler 22, so the process proceeds to step S8 in order to spend all the cooling water for cooling the intercooler 22.

On the other hand, if the determination in step S3 is No, the fuel temperature Tfd in the delivery pipe 13 is low and it can be considered that cooling of the fuel is unnecessary, so the routine proceeds to step S8.
On the other hand, if the determination in step S4 is Yes, the temperature of the fuel in the delivery pipe 13 is significantly lowered due to fuel injection into the cylinder, and it can be considered that cooling by the fuel cooler 29 is unnecessary. .

In step S8, the opening degree of the flow control valve 37 is set to the intercooler position, and then the routine is terminated.
Therefore, in any of the above steps S2 to S4, the cooling water is not supplied to the fuel cooler 29, and the fuel cooling by the fuel cooler 29 is not executed. The water pump 38 discharges cooling water corresponding to the required amount of cooling water for the intercooler 22, and the cooling water is supplied only to the intercooler 22 and used for cooling the intake air to the engine 1. This prevents an increase in power consumption of the motor that drives the water pump 38.

Next, the cooling control executed during the automatic stop of the engine 1 by the idle stop control will be described.
FIG. 3 is a flowchart showing an engine stop cooling control routine executed by the ECU 41 while the engine 1 is automatically stopped. The ECU 41 executes the routine at predetermined control intervals while the engine 1 is automatically stopped.

  First, in step S11, the opening degree of the flow control valve 37 is set to the fuel cooler position (cooling control means), and in the subsequent step S12, the fuel temperature Tfd in the delivery pipe 13 is set in advance as in step S3. It is determined whether Tfd0 is exceeded (Tfd> Tfd0). When the determination in step S12 is Yes, it is considered that cooling by the fuel cooler 29 is necessary, and the process proceeds to step S13.

  In step S13, the required heat dissipation amount Qa to the fuel cooler 29 is calculated according to the above equation (1) (heat dissipation amount calculating means), and the required heat dissipation amount Qc to the bearing portion 21c of the turbocharger 21 is calculated according to the above equation (5). To do. Then, the required amount of cooling water to be supplied to the fuel cooler 29 in order to achieve the required heat dissipation amount Qa is calculated, and the required amount of cooling water to be supplied to the bearing portion 21c of the turbocharger 21 in order to achieve the required heat dissipation amount Qc is calculated. Calculate and add both calculated values.

In the subsequent step S14, the drive duty of the water pump 38 that can achieve the required amount of cooling water added in step S13 is set (cooling control means), and then the routine is terminated.
The above is the basic control contents during the automatic stop of the engine 1, and in this case, the cooling of both the fuel cooler 29 and the bearing portion 21c of the turbocharger 21 is necessary in view of the necessity of cooling. The amount of cooling water required for the discharge is discharged from the water pump 38 based on the drive duty setting in step S14, and the cooling water is distributed only to the fuel cooler 29 side based on the opening degree setting of the flow control valve 37 in step S11. The

  Therefore, both the fuel cooler 29 and the bearing portion 21c of the turbocharger 21 achieve the desired cooling, and the fuel in the delivery pipe 13 and the bearing portion 21c can be cooled. By cooling the fuel while the engine is automatically stopped, the temperature rise of the injector 11 can be suppressed after the engine is started, thereby preventing variations in the fuel injection amount between the cylinders. Further, the bearing 21c of the turbocharger 21 when the engine is automatically stopped can be prevented. Seizure can be prevented.

  On the other hand, if the determination in step S12 is No, it is determined that fuel cooling is unnecessary, and the process proceeds to step S15. In step S15, it is determined whether or not the outlet oil temperature To of the turbocharger 21 exceeds a preset determination value To0 (To> To0). It is determined whether or not the load operation integration time Tload (correlated with the engine heat generation amount) exceeds a preset determination value Tload0 (Tload> Tload0).

  The processing in steps S15 and S16 is intended to determine whether or not the bearing portion 21c of the turbocharger 21 requires cooling with cooling water. Even if it is determined in step S12 that cooling of the fuel is unnecessary, if cooling of the bearing portion 21c of the turbocharger 21 is required, it is necessary to supply cooling water to the turbocharger 21 via the fuel cooler 29. Therefore, when the determination of Yes is made in either step S15 or step S16, the process proceeds to step S13, and the cooling of the fuel cooler 29 and the bearing portion 21c of the turbocharger 21 is executed as described above.

  If NO is determined in both steps S15 and S16, the drive duty of the water pump 38 is set to 0 in step S17, and then the routine is terminated. In this case, cooling of the fuel by the fuel cooler 29 is unnecessary, and cooling of the bearing portion 21c of the turbocharger 21 is also unnecessary. Therefore, the water pump 38 is stopped and the cooling water circulating in the auxiliary machine cooling circuit 28 is circulated. Is stopped. This prevents an increase in power consumption of the motor that drives the water pump 38.

By the way, even if the cooling is executed based on the determination in step S12 at the beginning of the automatic engine stop, the processing in step S17 is executed when the fuel temperature Tfd and the outlet oil temperature To are gradually lowered and the cooling becomes unnecessary. When this timing precedes the automatic start of the engine 1 for starting the vehicle, the cooling is stopped during the automatic stop of the engine.
In the present embodiment, the cooling control is executed during the automatic stop of the engine 1 by the idle stop control. However, the present invention is not limited to this, and the cooling control may be executed when the engine is stopped normally. Even in this case, it is necessary to prevent seizure of the bearing portion 21c of the turbocharger 21, and when the engine is started without time after the engine is stopped, if the fuel is cooled while the engine is stopped, After the engine is started, the temperature rise of the injector 11 can be suppressed. If cooling is not required while the engine is stopped, the water pump 38 is stopped based on the processing in step S17, so that no problem occurs.

  Further, at the time when the process is shifted from step S12 to step S13 because fuel cooling is required, it is not determined whether or not the bearing 21c of the turbocharger 21 needs to be cooled, but nevertheless, the required amount of cooling water to the fuel cooler 29 is reached. The addition of the required amount of cooling water to the bearing portion 21c of the turbocharger 21 is based on the viewpoint that the bearing portion 21c of the turbocharger 21 also needs to be cooled in a situation where the fuel cooler 29 needs to be cooled. However, the present invention is not limited to this. For example, when only cooling of the fuel is required (when the condition of Step S12 is satisfied and the conditions of Steps S15 and S16 are not satisfied), only the necessary cooling water amount to the fuel cooler 29 is obtained. Based on this, the drive duty of the water pump 38 may be set.

  As described above, in the cooling device for the direct injection engine 1 according to the present embodiment, the water jacket 29 a is formed on the delivery pipe 13 of the engine 1 to configure the fuel cooler 29, and the cooling water from the water pump 38 is supplied to the fuel cooler 29. By supplying, the fuel in the delivery pipe 13 is cooled. Then, for the fuel cooling at this time, a heat dissipation amount Qa required for the fuel cooler 29 is calculated, and a necessary cooling water amount to be supplied to the fuel cooler 29 is calculated based on the required heat dissipation amount Qa. The water pump 38 and the flow rate control valve 37 are controlled so as to achieve the above.

  Thus, since the water pump 38 and the flow rate control valve 37 are controlled based on the heat radiation amount Qa required for the fuel cooler 29 for cooling the fuel, the cooling water is supplied to the fuel cooler 29 without excess or deficiency. Cooling can be optimized. Therefore, it is possible to prevent problems caused by an inappropriate fuel temperature, such as an increase in the temperature of the injector 11 due to insufficient cooling of the fuel or an increase in power consumption of the motor driving the water pump 38.

  Also, the required heat dissipation amount Qa of the fuel cooler 29 is basically the difference between the actual heat amount of the fuel and the heat amount at the target temperature, and during the automatic stop of the engine 1, the above equation (2) The required heat dissipation amount Qa is calculated according to On the other hand, while the engine 1 is in operation, paying attention to the fact that there is a quantity of heat deprived from the fuel in the delivery pipe 13 by fuel injection into the cylinder, the demand is released according to the above formula (1) considering this quantity of heat. The amount of heat Qa is calculated.

Therefore, it is possible to calculate an appropriate required heat release amount during both operation and automatic stop of the engine 1, and further optimize the cooling of the fuel.
If the fuel temperature Tfd in the delivery pipe 13 is equal to or lower than the determination value Tfd0 during the operation of the engine 1, it is considered that the fuel cooler 29 does not need to cool the fuel (step S3), and the injection amount q of the injector 11 is determined. When the value q0 is exceeded, it is considered that the temperature of the fuel in the delivery pipe 13 due to fuel injection into the cylinder is so great that cooling by the fuel cooler 29 is unnecessary (step S4). The supply of cooling water to is stopped (step S8). Therefore, an increase in power consumption of the motor that drives the water pump 38 can be prevented.

  Further, during the operation of the engine 1, not only the required heat dissipation amount of the fuel cooler 29 but also the required heat dissipation amount of the intercooler 22 is calculated, and the respective required cooling water amounts are calculated, and are necessary to achieve those required cooling water amounts. The drive duty of the water pump 38 and the opening degree of the flow control valve 37 are set. Therefore, in addition to the fuel cooling by the fuel cooler 29, the cooling of the intake air by the intercooler 22 can be optimized.

This is the end of the description of the embodiment, but the aspect of the present invention is not limited to this embodiment. For example, in the above embodiment, the cooling device for the direct injection gasoline engine 1 is embodied. However, the type of the engine is not limited to this, and may be applied to, for example, a diesel engine.
Moreover, in the said embodiment, although the fuel supplied to the injector 11, the intercooler 22, and the bearing part 21c of the turbocharger 21 were made into the cooling object, it is not restricted to this. For example, after applying the present invention to the direct injection engine 1 that does not include the turbocharger 21, the control of the above embodiment may be executed only for the fuel cooler 29 provided in the delivery pipe 13.

  Further, the position where the fuel cooler 29 is provided is not limited to the delivery pipe 13. For example, the fuel cooler 29 is disposed in the fuel path 14 on the inlet side of the high pressure pump 15 to cool the fuel flowing into the high pressure pump 15. You may do it. Even in this case, the same effect can be obtained by executing the control of the above embodiment.

DESCRIPTION OF SYMBOLS 1 Direct injection engine 11 Injector 14 Fuel path 21 Turbocharger 22 Intercooler 29 Fuel cooler 37 Flow control valve (flow rate adjustment means)
38 Water pump (flow rate adjusting means)
41 ECU (heat dissipation amount calculation means, cooling control means, idle stop control means)

Claims (6)

A fuel cooler that is disposed in a fuel path of an injector that injects fuel into the cylinder, and that cools the fuel supplied to the injector by circulation of cooling water;
A flow rate adjusting means capable of adjusting a flow rate of cooling water supplied to the fuel cooler;
A heat dissipation amount calculating means for calculating a heat dissipation amount required for the fuel cooler for cooling the fuel supplied to the injector based on an operating state of the direct injection engine;
A cooling apparatus for a direct injection engine, comprising: cooling control means for controlling the flow rate adjusting means based on the required heat radiation amount calculated by the heat radiation amount calculating means. The flow rate adjusting means is at least one of a water pump that discharges cooling water supplied to the fuel cooler or a flow rate control valve that controls the flow rate of cooling water discharged from the water pump,
2. The cooling device for a direct injection engine according to claim 1, wherein the cooling control unit controls a rotation speed of the water pump or an opening degree of the flow control valve based on a required heat radiation amount to the fuel cooler. . The direct injection engine is provided with a water-cooled intercooler for cooling the intake air pressurized by a turbocharger compressor,
The heat dissipation amount calculating means calculates a heat dissipation amount required for the water-cooled intercooler for cooling the intake air,
The flow rate adjusting means is a water pump that discharges cooling water, and a flow rate control valve that can distribute the cooling water discharged from the water pump to the fuel cooler side and the water-cooled intercooler side at an arbitrary ratio,
The cooling control means controls the distribution rate of cooling water by the rotational speed of the water pump and the flow control valve based on the amount of heat radiation required for the fuel cooler and the intercooler. The direct-injection engine cooling device according to 2. The heat dissipation amount calculating means is configured to supply the fuel cooler with a difference between an actual heat amount of fuel supplied to the injector and a heat amount of fuel at a preset target temperature while the direct injection engine is stopped. The required heat release amount is calculated, and during operation of the direct injection engine, the amount of heat taken by fuel injection into the cylinder is subtracted from the difference between the actual heat amount and the heat amount at the target temperature, and the fuel cooler is subtracted. 4. The direct-injection engine cooling device according to any one of claims 1 to 3, wherein the required heat radiation amount is calculated. Idle stop control means for automatically stopping the direct injection engine based on establishment of a predetermined stop condition, and then automatically starting the direct injection engine based on establishment of a predetermined start condition;
The heat dissipation amount calculating means calculates a required heat dissipation amount to the fuel cooler based on a difference between the actual heat amount and the heat amount at the target temperature during the automatic stop of the direct injection engine by the idle stop control means. The cooling device for a direct injection engine according to claim 4. When the temperature of the fuel supplied to the injector is equal to or lower than a first determination value set in advance, or the fuel injection amount of the injector exceeds a second determination value set in advance. 6. The direct injection engine cooling according to claim 1, wherein the supply of the cooling water to the fuel cooler is stopped by the flow rate adjusting means when any of the cases is satisfied. apparatus.

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