JP7192173B2 - engine cooling system - Google Patents

Description

The present invention relates to an engine cooling device having a water pump rotationally driven by an engine.

2. Description of the Related Art An engine provided in a vehicle or the like is configured such that cooling water is pressure-fed to an engine body and accessories by a water pump rotationally driven by the engine. Also, a flow control valve capable of opening and closing the flow control valve is provided in the path through which the cooling water flows, and the flow rate of the cooling water is changed by opening and closing the flow control valve.

In an engine equipped with a flow control valve, failure of the flow control valve may prevent an appropriate amount of cooling water from being supplied to the engine body. Desired. On the other hand, in Patent Document 1, a temperature sensor that detects the temperature of the cooling water is provided in the path through which the cooling water flows, and the flow control valve malfunctions based on the change in the temperature of the cooling water detected by the temperature sensor. There is disclosed a configuration for determining whether or not

JP 2004-76647 A

Even when the flow rate of the cooling water changes, the temperature of the cooling water changes only gradually, and the responsiveness of the temperature change of the cooling water to the change of the cooling water flow rate is low. From this, in the configuration of Patent Document 1, that is, the configuration that determines whether or not the flow control valve is out of order based on the change in the temperature of the cooling water, even if the flow control valve is out of order, this failure is detected. The problem is that it cannot be detected immediately. If the detection of a failure of the flow control valve is delayed, the temperature of the engine body will rise excessively due to the delay in responding to this failure, causing damage, or the temperature of the engine body will become excessively low, causing damage to the engine itself. Combustion may become unstable.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an engine cooling system capable of quickly and accurately determining whether or not a flow control valve has failed. do.

In order to solve the above problems, the present invention provides an engine cooling device, comprising: a cooling water path for circulating cooling water through an engine body; a valve body capable of opening and closing the cooling water path; A flow control valve comprising a driving unit that duty-drives the valve body so that the body opens and closes at a predetermined frequency, a pressure sensor that detects the pressure of cooling water flowing through the cooling water path, and the flow control valve. wherein when a predetermined failure determination condition is established, the opening/closing frequency of the valve body of the flow control valve is higher than when the failure determination condition is not met. It controls the driving part so that the valve body is opened and closed, and determines whether or not the flow control valve is out of order based on the detected value of the pressure sensor when the valve body is opened and closed. .

When the flow rate of cooling water flowing through the cooling water path changes, the pressure of the cooling water in the cooling water path changes earlier than its temperature. On the other hand, in the present invention, it is determined whether or not the flow control valve is out of order based on the pressure change of the cooling water caused by the opening and closing of the flow control valve. As a result, it is possible to quickly determine whether or not the flow control valve is out of order.

Moreover, in the present invention, when it is determined whether or not the failure determination execution condition is satisfied and the flow control valve is in failure, the valve body is driven to open and close while the drive frequency of the valve body is increased. Therefore, it is possible to prevent a large change in the flow rate of cooling water due to the opening and closing drive of the valve body for failure determination, and prevent failure of the flow control valve while optimizing the amount of cooling water supplied to the engine body. can judge.

In the above configuration, preferably, the control means permits opening of the valve body when the temperature of the cooling water is equal to or higher than a predetermined set temperature, and allows the opening of the valve body when the temperature of the cooling water is lower than the set temperature. Opening and closing of the valve body is permitted only when failure determination execution conditions are satisfied (claim 2).

In this configuration, when the temperature of the cooling water is equal to or higher than the set temperature and the temperature of the engine body is high, the opening of the valve body is permitted and the engine body can be cooled by the cooling water. It can prevent the temperature of the main body from becoming excessively high. In addition, when the temperature of the cooling water is lower than the set temperature, the temperature of the engine body is low, and the failure judgment execution condition is not satisfied, opening and closing of the valve body is prohibited, and the circulation of the cooling water is stopped. , the cooling of the engine body by the cooling water can be avoided, and the warm-up of the engine body can be promoted. Even when the temperature of the cooling water is lower than the set temperature and the failure determination execution condition is established, the opening/closing frequency of the valve body is increased as described above, and the cooling water is Since the change in the flow rate of the valve is kept small, it is possible to prevent the engine body from being excessively cooled due to the opening and closing of the valve. As a result, it is possible to appropriately determine the failure of the flow control valve at a timing during warm-up of the engine body, that is, at an early timing after the engine is started, while promoting warm-up of the engine body.

In the above configuration, preferably, the control means never determines whether the temperature of the cooling water is less than the set temperature and whether the flow control valve has failed since the engine was started. Sometimes, it is determined that the failure determination execution condition is established (claim 3).

According to this configuration, it is possible to determine whether or not the flow control valve has failed when the warm-up has not been completed after the engine has started, that is, at an early timing after the engine has started. , it is also possible to accelerate the warm-up of the engine body as described above.

In the above configuration, preferably, when the temperature of the cooling water is equal to or higher than the set temperature, the control means controls the valve body so that the wall temperature of the combustion chamber formed in the engine body reaches a preset target temperature. is opened and closed (claim 4).

According to this configuration, the wall temperature of the combustion chamber can be controlled to an appropriate temperature by opening and closing the flow control valve.

As described above, according to the engine cooling system of the present invention, it is possible to quickly and accurately determine whether or not the flow control valve has failed.

1 is a system diagram schematically showing the overall configuration of an engine to which the present invention is applied; FIG. 1 is a circuit diagram schematically showing the overall configuration of an engine cooling device; FIG. FIG. 3 is a schematic cross-sectional view showing the essential parts of the engine body; It is a schematic sectional drawing of a flow control valve. FIG. 4 is a diagram showing changes in the degree of opening of a flow control valve and accompanying changes in the pressure of cooling water; 3 is a block diagram showing a control system of the engine; FIG. 4 is a flow chart showing a procedure for initial failure determination of a flow control valve. 4 is a flow chart showing a procedure for normal failure determination of a flow control valve; FIG. 5 is a diagram showing the opening degree of the flow control valve at the time of initial failure determination performed during engine warm-up;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(1) Entire Configuration of Engine FIG. 1 is a diagram showing a preferred embodiment of a vehicle engine (hereinafter simply referred to as engine) to which the control device of the present invention is applied. The engine shown in FIG. 1 is a four-cycle gasoline direct-injection engine mounted on a vehicle as a power source for running. It has an exhaust passage 40 through which exhaust gas discharged from the engine body 1 flows, and an external EGR device 50 that recirculates part of the exhaust gas flowing through the exhaust passage 40 to the intake passage 30 .

The engine body 1 includes a cylinder block 3 in which a cylinder 2 is formed, a cylinder head 4 attached to the upper surface of the cylinder block 3 so as to block the cylinder 2 from above, and a reciprocatingly slidable insertion into the cylinder 2. and a piston 5 that is The engine body 1 is typically of a multi-cylinder type having a plurality of (for example, four) cylinders 2, but for the sake of simplification, only one cylinder 2 will be described here.

A combustion chamber 6 is defined above the piston 5, and fuel containing gasoline as a main component is supplied to the combustion chamber 6 by injection from an injector 15, which will be described later. The supplied fuel burns while being mixed with air in the combustion chamber 6, and the piston 5 reciprocates vertically by receiving the expansion force due to the combustion.

A crankshaft 7 that is an output shaft of the engine body 1 is provided below the piston 5 . The crankshaft 7 is connected to the piston 5 via a connecting rod 8 and is driven to rotate about the central axis in accordance with the reciprocating motion (vertical motion) of the piston 5 .

A crank angle sensor SN1 is assembled to the cylinder block 3 . Crank angle sensor SN1 detects the rotation angle (crank angle) of crankshaft 7 and the rotation speed of crankshaft 7 (engine rotation speed).

The cylinder head 4 has an intake port 9 for introducing air supplied from an intake passage 30 into the combustion chamber 6, and an exhaust port 10 for introducing exhaust gas generated in the combustion chamber 6 to an exhaust passage 40. , an intake valve 11 for opening and closing the opening of the intake port 9 on the combustion chamber 6 side, and an exhaust valve 12 for opening and closing the opening of the exhaust port 10 on the combustion chamber 6 side. The intake valve 11 and the exhaust valve 12 are driven to open and close in conjunction with the rotation of the crankshaft 7 by a valve mechanism including a pair of camshafts arranged in the cylinder head 4 .

The cylinder head 4 has an injector 15 for injecting fuel (gasoline) into the combustion chamber 6 and a spark plug 16 for igniting a mixture of the fuel and intake air injected from the injector 15 into the combustion chamber 6. is provided.

The intake passage 30 is connected to one side surface of the cylinder head 4 so as to communicate with the intake port 9 . The intake passage 30 includes, in order from the upstream side thereof, an air cleaner 31 that removes foreign matter from the intake air, a throttle valve 32 that can be opened and closed to adjust the flow rate of the intake air, a supercharger 33 that compresses and delivers the intake air, and a supercharger. An intercooler 35 for cooling the intake air compressed by the feeder 33 and a surge tank 36 are provided. An airflow sensor SN2 for detecting the flow rate of intake air is provided in the intake passage 30 between the air cleaner 31 and the throttle valve 32 .

The supercharger 33 is a mechanical supercharger mechanically linked to the engine body 1 via an electromagnetic clutch 34 . As the supercharger 33, any known supercharger such as Lysholm type, Roots type, or centrifugal type can be used.

A bypass passage 38 for bypassing the supercharger 33 is provided in the intake passage 30 . The bypass passage 38 connects the surge tank 36 and an EGR passage 51 (to be described later) to each other. A bypass valve 39 that can be opened and closed is provided in the bypass passage 38 .

The exhaust passage 40 is connected to the other side surface of the cylinder head 4 so as to communicate with the exhaust port 10 . A catalytic converter 41 is provided in the exhaust passage 40 . The catalytic converter 41 includes a three-way catalyst 41a for purifying harmful components (HC, CO, NOx) contained in the exhaust gas flowing through the exhaust passage 40, and particulate matter (PM) contained in the exhaust gas. A GPF (gasoline particulate filter) 41b for collecting is incorporated.

The external EGR device 50 has an EGR passage 51 that connects the exhaust passage 40 and the intake passage 30 , an EGR valve 53 that opens and closes the EGR passage 51 , and an EGR cooler 52 provided in the EGR passage 51 . The EGR passage 51 connects a portion of the exhaust passage 40 downstream of the catalytic converter 41 and a portion of the intake passage 30 between the throttle valve 32 and the supercharger 33 . The EGR cooler 52 cools the exhaust gas recirculated from the exhaust passage 40 to the intake passage 30 through the EGR passage 51 by heat exchange.

The geometric compression ratio of the cylinder 2, that is, the ratio of the volume of the combustion chamber 6 when the piston 5 is at the top dead center to the volume of the combustion chamber 6 when the piston 5 is at the bottom dead center, is 13 or more and 30 or less. , preferably set to a high compression ratio of 14 or more and 18 or less.

In the present embodiment, SPCCI combustion, in which part of the air-fuel mixture is subjected to compression ignition, is performed in a low-speed region where the engine speed is equal to or lower than a predetermined speed. Thus, the geometric compression ratio of cylinder 2 is set to a relatively high value as described above.

SPCCI combustion is partial compression ignition combustion in which SI combustion and CI combustion are combined. SI combustion is a combustion mode in which a spark generated by the spark plug 16 ignites an air-fuel mixture, and flame propagation that spreads the combustion area from the ignition point to the surroundings forces the air-fuel mixture to burn. CI combustion is a combustion mode in which an air-fuel mixture is combusted by self-ignition under an environment of sufficiently high temperature and high pressure due to compression of the piston 5 or the like. SPCCI combustion, which is a combination of these SI combustion and CI combustion, involves SI combustion of part of the air-fuel mixture in the combustion chamber 6 by spark ignition performed in an environment just before the air-fuel mixture self-ignites. This is a combustion mode in which another air-fuel mixture in the combustion chamber 6 is later CI-burned by self-ignition (due to further increase in temperature and pressure accompanying SI combustion). That is, in the low speed region, fuel and air are mixed in advance, a part of this air-fuel mixture is forcibly burned by ignition from the ignition plug 16, and the remaining air-fuel mixture is compressed by the thermal energy of this combustion. Ignite. “SPCCI” is an abbreviation for “Spark Controlled Compression Ignition”. On the other hand, in the present embodiment, general SI combustion is performed in a high speed region where the engine speed is higher than in the low speed region.

(2) Overall Configuration of Cooling Device FIG. 2 is a circuit diagram showing the overall configuration of the cooling device 60 for the engine. As shown in the figure, the cooling device 60 includes a water pump (W/P) 61, a radiator (RAD) 71, and a plurality of cooling water paths 62 to 66 (main cooling water path 62) for circulating cooling water. , an EGR cooling water path 63, an ATF cooling water path 64, a communication path 65, and a valve path 66).

The water pump 61 is a pump for discharging cooling water and is attached to one side surface of the cylinder block 3 . The water pump 61 is rotationally driven by the engine body 1 . Specifically, the water pump 61 is connected to the crankshaft 7 via a belt, and is rotationally driven by the crankshaft 7 to discharge cooling water.

The radiator 71 is a heat exchanger for cooling cooling water, and when the cooling water passes through the radiator 71, it is cooled by the running wind of the vehicle or the like.

(main cooling water path)
As indicated by solid arrows in FIG. 2 , the main cooling water path 62 passes the cooling water discharged from the water pump 61 through a block-side water jacket 62 a formed in the cylinder block 3 and a combustion chamber formed in the cylinder head 4 . This is a route for circulation back to the water pump 61 via the side water jacket 62b and the radiator 71. FIG.

As shown in FIG. 3, the combustion chamber side water jacket 62b is a water jacket formed in the vicinity of the combustion chamber 6 of the cylinder head 4 and around the valve seat portions of the intake port 9 and the exhaust port 10. be.

A position between the radiator 71 and the water pump 61 in the main cooling water path 62, more specifically, downstream of the radiator 71 and upstream of the water pump 61 with respect to the flow direction of the cooling water indicated by the solid-line arrow in FIG. A first thermostat valve 72 is provided at a position on the side.

The first thermostat valve 72 is a valve body 72a (hereinafter referred to as a TS valve body 72a) that opens and closes the main cooling water path 62, and the temperature of the cooling water passing through the TS valve body 72a exceeds a predetermined valve opening temperature. A TS valve main body 72a is provided which opens (is fully opened) at times and closes (is fully closed) when the temperature of the cooling water is lower than the valve opening temperature. The first thermostat valve 72 is a variable thermostat valve capable of changing the valve opening temperature, and includes a thermostat heater 72b for changing the valve opening temperature. The thermostat heater 72b generates heat when energized. The greater the amount of electricity supplied to the thermostat heater 72b, the lower the valve opening temperature. That is, when the amount of power supplied to the thermostat heater 72b is large and the temperature of the thermostat heater 72b is high, the temperature of the cooling water is lower than when the amount of power supplied to the thermostat heater 72b is small and the temperature of the thermostat heater 72b is low. The TS valve main body 72a is opened at the timing. The amount of power supplied to the thermostat heater 72b is controlled by the PCM 100, which will be described later.

When the coolant temperature is equal to or higher than the valve opening temperature and the first thermostat valve 72 (TS valve body 72a) is open, the coolant flows through the main coolant passage 62 and is driven by the radiator 71. Cooled. On the other hand, when the first thermostat valve 72 is closed, the flow of cooling water through the main cooling water path 62 is stopped, and cooling of the cooling water by the radiator 71 is stopped.

The main cooling water path 62 is provided with a first water temperature sensor SN3 and a second water temperature sensor SN4 that detect the temperature of the cooling water flowing through it. The first water temperature sensor SN3 is positioned between the water pump 61 and the cylinder block 3, more specifically, downstream of the water pump 61 and from the cylinder block 3 in the flow direction of the cooling water indicated by the solid arrow in FIG. is provided at a position on the upstream side, and detects the temperature of cooling water passing through this position. The second water temperature sensor SN4 is positioned between the cylinder head 4 and the radiator 71, more specifically, downstream of the cylinder head 4 and upstream of the radiator 71 with respect to the cooling water flow direction indicated by the solid arrow in FIG. It is provided at a position on the side, and detects the temperature of cooling water passing through this position. Hereinafter, the temperature of the cooling water detected by the first water temperature sensor SN3 will be referred to as the engine water temperature. Here, the temperature of the cooling water passing through the TS valve main body 72a of the first thermostat valve 72 is substantially the same as the engine water temperature detected by the first water temperature sensor SN3, and the first thermostat valve 72 is adjusted according to this engine water temperature. Open and close.

(EGR cooling water path)
The EGR cooling water path 63 is a path that bypasses part of the main cooling water path 62 .

As indicated by the dashed-dotted line arrow in FIG. 2 , part of the cooling water flowing through the block-side water jacket 62 a included in the main cooling water path 62 is introduced into the EGR cooling water path 63 . The cooling water introduced into the EGR cooling water path 63 from the block side water jacket 62a passes through the EGR cooler (EGR/C) 52, the heater core 74 for air conditioning, and the exhaust port side water jacket 63b formed in the cylinder head 4. and return to the water pump 61.

As shown in FIG. 3, the exhaust port-side water jacket 63b is a water jacket formed around the exhaust port 10 at a position downstream (downstream in the flow direction of the exhaust gas) of the combustion chamber-side water jacket 62b. be.

Thus, in the present embodiment, a part of the main cooling water passage 62 including the block-side water jacket 62a and the EGR cooling water passage 63 allow the water pump 61 and A path 160 is formed for circulating cooling water via the engine body 1 . In the present embodiment, the cooling water flow path 160 formed by a part of the main cooling water path 62 including the block-side water jacket 62a and the EGR cooling water path 63 is referred to as the "cooling water path" in the claims. Equivalent to.

The position between the cylinder head 4 and the water pump 61 in the EGR cooling water path 63, more specifically, the position downstream of the cylinder head 4 and the water pump 61 with respect to the flow direction of the cooling water indicated by the dashed-dotted arrow in FIG. A flow control valve (S/V) 75 is interposed at a position on the upstream side.

FIG. 4 is a schematic cross-sectional view of the flow control valve 75. As shown in FIG. FIG. 5 shows the degree of opening of the flow control valve 75 (the upper graph in FIG. 4) and the pressure of the cooling water in the EGR cooling water path 63 detected by a pressure sensor SN5 (described later) (in FIG. 4). lower graph). Note that the lower graph in FIG. 4 schematically shows changes in the pressure of the cooling water.

The flow control valve 75 is a solenoid type opening/closing valve, and includes a valve body 75a that opens and closes the EGR cooling water path 63, and a driving portion 75b that receives electric power to drive the valve body 75a. The flow control valve 75 is of a normally open type, and the valve body 75a is fully opened when the power supply to the driving portion 75b is stopped.

The driving portion 75b duty-drives the valve body 75a so that it opens and closes at a predetermined frequency. That is, the flow control valve 75 is a DUTY control valve, and as shown in FIG. 5, the valve body 75a is driven to repeat full opening and full closing. Then, one energization is performed for a period (one cycle) T obtained by combining one energization stop period, that is, the valve opening period T1 of the valve body 75a, and one energization period, that is, the valve closing period T2 of the valve body 75a. The flow rate of the cooling water passing through the valve main body 75a is changed by changing the period, that is, the DUTY ratio, which is the ratio of one valve closing period T2. The electric power supplied to the driving portion 75b of the flow control valve 75 is controlled by the CSV control device 110 provided together with the flow control valve 75 and the PCM 100 which will be described later. The CSV control device 110 receives a command from the PCM 100, which will be described later, and supplies power to the driving section 75b at the commanded period and the commanded DUTY ratio. Hereinafter, the ratio of the energization period, that is, the valve closing period T2 to one period T of the flow control valve 75 is simply referred to as the DUTY ratio of the flow control valve 75 as appropriate.

As described above, since the flow control valve 75 is of the normally open type, when the DUTY ratio of the flow control valve 75 is set to 0% and the power supply to the driving portion 75b is stopped, the valve body 75a of the flow control valve 75 is fully open. On the other hand, when the duty ratio of the flow control valve 75 is set to 100% and electric power is continuously supplied to the driving portion 75b, the valve main body 75a is kept fully closed.

Specifically, the drive unit 75b includes a coil 171 that receives power supply to generate an electromagnetic force; a drive pin 174 connected to the movable core 173 and moving integrally therewith; a retainer 175 attached to the tip of the drive pin 174; and a spring 176 that is The valve body 75a is connected to the drive pin 174 and moves integrally with the drive pin 174 and the movable core 173 . The spring 176 is arranged to bias the retainer 175 in the upward direction in FIG. 4 and in the direction in which the valve body 75a opens. When power is supplied to the coil 171, the movable core 173 is attracted to the fixed core 172 as shown in FIG. 4, and the valve body 75a is fully closed. On the other hand, when the power supply to the coil 171 is stopped, the biasing force of the spring 176 moves the retainer 175 and the valve body 75a upward in FIG. 4, and the valve body 75a is fully opened.

The EGR cooling water path 63 is provided with a pressure sensor SN5 for detecting the pressure of the cooling water flowing therethrough. The pressure sensor SN5 is positioned between the cylinder head 4 and the flow control valve 75, more specifically, downstream of the cylinder head 4 in the flow direction of the cooling water indicated by the dashed-dotted arrow in FIG. , and detects the pressure of cooling water passing through this position.

The EGR cooling water path 63 is connected to the main cooling water path 62 via a communication path 65 at a position between the heater core 74 and the flow control valve 75 . Specifically, the cylinder head 4 is formed with a communication path 65 that connects the combustion chamber side water jacket 62b and the exhaust port side water jacket 63b. In the cylinder head 4 , the EGR cooling water path 63 and the main cooling water path 62 are connected by this communication path 65 .

The valve path 66 is a path that connects the combustion chamber side water jacket 62b and a portion of the EGR cooling water path 63 between the heater core 74 and the exhaust port side water jacket 63b. A part of the cooling water in the combustion chamber side water jacket 62 b passes through the valve path 66 and joins the EGR cooling water path 63 via the throttle valve (ETB) 32 and the bypass valve (ABV) 39 .

(Cooling water path for ATF)
The ATF cooling water path 64 is a path that bypasses part of the main cooling water path 62 separately from the EGR cooling water path 63 , and connects the block-side water jacket 62 a and the water pump 61 . As indicated by the dashed arrows in FIG. 2, part of the cooling water in the block-side water jacket 62a is diverted from the main cooling water path 62 to the ATF warmer (ATF/W) 76 and the oil cooler (O/C). ) 77 and then returns to the water pump 61 . The ATF warmer 76 is a device for warming ATF (automatic transmission fluid), that is, the liquid used in the transmission, and the oil cooler 77 is a device for cooling lubricating oil supplied to the engine body 1 and the like.

In the ATF cooling water path 64, a second thermostat valve (T/S ) 78 are interposed. The second thermostat valve 78 is a thermostat valve with a fixed opening temperature.

(3) Control System FIG. 6 is a block diagram showing the engine control system. A PCM 100 shown in this figure is a microprocessor for overall control of the engine and the like, and is composed of a well-known CPU, ROM, RAM and the like.

Detection signals from various sensors are input to the PCM 100 . For example, the PCM 100 is electrically connected to the aforementioned crank angle sensor SN1, airflow sensor SN2, first water temperature sensor SN3, second water temperature sensor SN4, and pressure sensor SN5. Information detected by these sensors (that is, crank angle, engine speed, intake flow rate, engine water temperature, cooling water temperature at the outlet of the cylinder head 4, and cooling water pressure) is sequentially input to the PCM 100 . The vehicle is also provided with an accelerator pedal sensor SN6 that detects the opening of an accelerator pedal operated by the driver of the vehicle.

The PCM 100 controls each section of the engine while executing various determinations and calculations based on input information from each sensor. The PCM 100 includes an injector 15, a spark plug 16, a throttle valve 32, an electromagnetic clutch 34, a bypass valve 39, an EGR valve 53, a water pump 61, a thermostat heater 72b (first thermostat valve 72), and a CSV controller 110 (flow control valve 75). ), etc., and outputs control signals to each of these devices based on the results of the above calculations and the like.

The PCM 100 functionally includes a combustion control unit 101, a cooling water control unit 102, and a failure determination unit 103 by executing a predetermined program. The PCM 100 corresponds to "control means" in the claims.

(combustion controller)
The combustion control unit 101 is a control module that controls combustion of the air-fuel mixture in the combustion chamber 6 . The combustion control unit 101 controls each part of the engine (injector 15, spark plug 16, etc.) so that the engine output becomes an appropriate value according to the driver's request. Specifically, the combustion control unit 101 calculates a required output, which is a required value of the engine output, based on the opening of the accelerator pedal detected by the accelerator pedal sensor SN6, the engine speed, and the like, and based on this required output, , the amount of air and the amount of fuel to be introduced into the combustion chamber 6 are calculated. Then, the throttle valve 32 and the injector 15 are driven so that the calculated air amount and fuel amount are introduced into the combustion chamber 6 . Further, the combustion control unit 101 changes the ignition timing of the spark plug 16, the opening degree of the EGR valve 53, etc. so that SPCCI combustion is realized in the low speed region and SI combustion is realized in the high speed region.

(cooling water controller)
The cooling water control unit 102 is a control module that controls the cooling device 60 . Here, control of the first thermostat valve 72 and the flow control valve 75 performed by the cooling water control unit 102 will be described.

The cooling water control unit 102 determines the opening temperature of the first thermostat valve 72 and changes the amount of electricity supplied to the thermostat heater 72b of the first thermostat valve 72 .

The cooling water control unit 102 switches the opening temperature of the first thermostat valve 72 between the first temperature and the second temperature, which is lower than the first temperature, according to the wall temperature of the combustion chamber 6 . Specifically, when the wall temperature of the combustion chamber 6 is less than the predetermined reference wall temperature, the cooling water control unit 102 sets the valve opening temperature of the first thermostat valve 72 to the first temperature, The amount of electricity supplied to the thermostat heater 72b is adjusted so that the temperature corresponds to this temperature. On the other hand, when the wall temperature of the combustion chamber 6 is equal to or higher than the reference wall temperature, the cooling water control unit 102 sets the valve opening temperature of the first thermostat valve 72 to the second temperature, and the temperature of the thermostat heater 72b corresponds to this. The amount of power supplied to the thermostat heater 72b is adjusted so that the temperature becomes the same. As a result, when the engine water temperature is less than the first temperature and the warm-up of the engine body 1 is not completed, the supply of the coolant cooled by the radiator 71 to the engine body 1 is prohibited. 1 is accelerated to warm up. On the other hand, when the engine water temperature rises to the first temperature or higher and the warm-up of the engine body 1 is completed, the cooling liquid cooled by the radiator 71 is started to be supplied to the engine body 1, and the engine is cooled by the cooling water. Cooling of the main body 1 is started. However, when the wall temperature of the combustion chamber 6 is equal to or higher than the reference wall temperature, the first thermostat valve 72 is opened and cooled by the radiator 71 if the engine water temperature is equal to or higher than the second temperature even if the temperature is lower than the first temperature. Then, the cooling water is supplied to the engine body 1 .

The first temperature and the second temperature are preset and stored in the PCM 100 . For example, the first temperature is set to approximately 90°C, and the second temperature is set to approximately 80°C. The reference wall temperature is a temperature at which SPCCI combustion is appropriately achieved, and is set to the wall temperature of the combustion chamber 6 when the engine coolant temperature is approximately 120°C, for example, 116°C.

An estimated value is used for the wall temperature of the combustion chamber 6 that serves as a reference for switching the opening temperature of the first thermostat valve 72 . The cooling water control unit 102 estimates the wall temperature of the combustion chamber 6 based on the cooling water temperature detected by the second water temperature sensor SN4.

The cooling water control unit 102 determines the duty ratio of the flow control valve 75 and issues a command to the CSV control device 110 so that the flow control valve 75 (valve body 75a) is opened and closed at this duty ratio.

When the engine water temperature is less than the first temperature and the warm-up of the engine body 1 is not completed, the cooling water control unit 102 prohibits the flow control valve 75 from opening and sets its duty ratio to 100%. The flow control valve 75 is kept fully closed. Thus, in this embodiment, when the engine water temperature is lower than the first temperature, the flow control valve 75 is prohibited from opening, and the first temperature is the "set temperature" in the claims. Equivalent to.

On the other hand, when the engine water temperature is equal to or higher than the first temperature, the flow control valve 75 is allowed to open and close, and the cooling water control unit 102 controls the flow rate so that the wall temperature of the combustion chamber 6 reaches the target wall temperature, which is its target value. Determine the duty ratio of the control valve 75 . An estimated value is also used for the wall temperature of the combustion chamber 6 . The target wall temperature is preset and stored in the cooling water control unit 102 . In this embodiment, the target temperature is set to a temperature equal to or lower than the reference wall temperature.

Specifically, when the wall temperature of the combustion chamber 6 is higher than the target wall temperature, the cooling water control unit 102 reduces the DUTY ratio of the flow control valve 75 to lengthen the valve opening period T1 of the flow control valve 75. do. As the valve opening period T1 of the flow control valve 75 becomes longer, the flow rate of the cooling water flowing through the block-side water jacket 62a and the exhaust port-side water jacket 63b included in the EGR cooling water path 63 in which the flow control valve 75 is arranged. will increase. As a result, the cooling of the engine body 1 is promoted and the wall temperature of the combustion chamber 6 is lowered. On the other hand, when the wall temperature of the combustion chamber 6 is lower than the target wall temperature, the cooling water control unit 102 increases the DUTY ratio of the flow control valve 75, shortens the valve opening period T1 of the flow control valve 75, The flow rate of cooling water flowing through the block side water jacket 62a and the exhaust port side water jacket 63b is reduced. As a result, the cooling of the engine body 1 is suppressed and the wall temperature of the combustion chamber 6 rises.

Here, as described above, the valve opening temperature of the second thermostat valve 78 is fixed, and the second thermostat valve 78 opens when the engine coolant temperature reaches or exceeds a predetermined temperature regardless of the operating state of the engine. The opening temperature of the second thermostat valve 78 is set to a temperature lower than the first temperature, eg, 50.degree.

With the above configuration, when the engine is started with the engine water temperature lower than the valve opening temperature of the second thermostat valve 78, that is, when the engine is cold started, the first and second Thermostat valve 78 and flow control valve 75 are all kept closed. As a result, cooling of the engine body 1 by cooling water is not performed, and warming up of the engine body 1 is promoted. When the warm-up of the engine body 1 progresses and the engine water temperature reaches or exceeds the opening temperature of the second thermostat valve 78, the second thermostat valve 78 opens. As a result, the cooling water flows through the ATF cooling water path 64, and the cooling water heated in the block-side water jacket 62a is introduced into the ATF warmer 76 to warm the ATF. When the temperature of the coolant further rises to the first temperature or higher, that is, when the engine body 1 is completely warmed up, the second thermostat valve 78 opens. As a result, cooling of the cooling water by the radiator 71 is started as described above, and cooling of the engine body 1 by this cooled cooling water is started. When the cooling water reaches the first temperature or higher, the flow control valve 75 is permitted to open, and the flow control valve 75 is opened and closed so that the wall temperature of the combustion chamber 6 reaches the target wall temperature.

(Determination of flow control valve failure)
The failure determination unit 103 is a control module that determines whether or not the flow control valve 75 is out of order. A procedure for failure determination of the flow control valve 75 performed by the failure determination unit 103 will be described with reference to the flowcharts of FIGS. 7 and 8. FIG. FIG. 7 shows a procedure for failure determination (initial failure determination) that is first performed after the engine is started, and FIG. shows the procedure.

First, in step S1, the failure determination unit 103 reads the detection values of each sensor. The failure determination unit 103 reads the engine speed detected by the crank angle sensor SN1, the coolant temperature detected by the first coolant temperature sensor SN3, that is, the engine water temperature, the coolant pressure detected by the pressure sensor SN5, and the like.

Next, in step S2, the failure determination unit 103 sets the driving frequency of the flow control valve 75, that is, the opening/closing frequency of the flow control valve 75, to the first frequency F1 (the opening/closing period T of the flow control valve 75 is set to 1/1). F1) to command the CSV controller 110 to accomplish this. That is, the CSV control device 110 is configured to be able to change the opening/closing frequency of the flow control valve 75, and receives a command from the failure determination section 103 to change it. The first frequency F1 is preset and stored in the failure determination unit 103 . For example, the first frequency F1 is 0.5 Hz (one cycle T1=2 seconds).

Next, in step S3, the failure determination unit 103 determines whether or not the basic condition is satisfied. When the basic condition is not established, the failure determination unit 103 terminates the process without performing failure determination after step S4 (returns to step S1). On the other hand, when the basic condition is satisfied, the failure determination section 103 proceeds to step S4. In this embodiment, the basic condition is established when the engine speed is equal to or higher than a predetermined speed lower than the idling speed, the engine has been started, and each sensor has not failed. is determined.

In step S4, the failure determination unit 103 determines whether or not the initial failure determination of the flow control valve 75 has not been completed. That is, it is determined whether or not the failure determination of the flow control valve 75 has been performed even once since the engine was started.

If the determination in step S4 is NO and the initial failure determination of the flow control valve 75 has been completed, the flow proceeds to step S21 of the flowchart shown in FIG. On the other hand, if the determination in step S4 is YES and the initial failure determination of the flow control valve 75 has not been completed, the process proceeds to step S5.

In step S5, the failure determination unit 103 determines whether or not the engine water temperature is equal to or higher than the first temperature.

If the determination in step S5 is NO and the engine water temperature is equal to or higher than the first temperature, that is, if the engine main body 1 has been warmed up, the process proceeds to step S7.

On the other hand, if the determination in step S5 is YES, the engine water temperature is less than the first temperature, and the engine body 1 has not been warmed up, the process proceeds to step S6.

In step S6, the failure determination unit 103 sets the opening/closing wave number of the flow control valve 75 to the second frequency F2. The second frequency F2 is set to a value higher than the first frequency F1. For example, the second frequency F2 is set to four times the first frequency F1. Then, the failure determination unit 103 controls the CSV control device 110 so that the flow control valve 75 is driven at the second frequency F2 (so that the opening/closing period T of the valve main body 75a of the flow control valve 75 becomes 1/F2). give a command to

Furthermore, in step S6, the failure determination unit 103 drives the flow control valve 75 to open and close at the second frequency F2. In this embodiment, the flow control valve 75 is opened and closed only for two cycles. Specifically, as described above, when the engine water temperature is lower than the first temperature (when the determination in step S5 is YES), the flow control valve 75 is basically kept fully closed. On the other hand, when the process proceeds to step S6, as shown by the solid line in FIG. 9, the flow control valve 75 is fully opened→fully closed→fully opened→fully closed, and then fully closed again. The DUTY ratio of the flow control valve 75 during this open/close drive is a value excluding 0% and 100%. For example, this DUTY ratio is set to 50%. After step S6, the process proceeds to step S7.

In step S7, the failure determination unit 103 determines whether or not the current engine speed is less than a preset reference speed. The reference rotation speed is preset and stored in the PCM 100 . The reference rotation speed is set to, for example, about 2000 rpm.

When the determination in step S7 is YES and the engine speed is less than the reference speed, the process proceeds to step S8.

In step S8, the failure determination unit 103 calculates the amount of increase in the pressure of the cooling water in the EGR cooling water path 63 due to the closing of the flow control valve 75, and sets it to the determination amount used in step S10, which will be described later. do. When the flow control valve 75 is closed, the cooling water is dammed by the flow control valve 75 . At this time, the cooling water in the EGR cooling water path 63 collides with the flow control valve 75, piping, etc. due to its inertia, and a so-called water hammer phenomenon occurs. Accordingly, as shown in FIG. 5, when the flow control valve 75 is closed (at time t1, etc.), the pressure in the EGR cooling water path 63 rapidly increases from P1 to P2. In step S8, the amount of pressure increase is calculated.

Here, when step S6 is performed in accordance with the determination in step S5 being YES, when a command to change the flow control valve 75 from the open state to the closed state is issued by the execution of step S6. (When a command to change the energization of the flow rate control valve 75 from 0% to 100%) is calculated. Specifically, the failure determination unit 103 detects the pressure detected by the pressure sensor SN5 at the timing when the valve closing command is issued to the flow control valve 75, and the pressure sensor SN5 at the timing immediately before the valve closing command is issued. A value obtained by subtracting the pressure detected by is calculated as the amount of increase in the pressure. Then, this calculated value is determined as the determination amount.

On the other hand, if the determination in step S5 is NO and the process proceeds to step S8, the cooling water control unit 102 changes the DUTY ratio of the flow control valve 75 from 0% to 100%. and greater than 0%, the flow control valve 75 is changed (commanded) from the open state to the closed state. Accordingly, when the determination is made, the failure determination unit 103 calculates the amount of pressure increase of the cooling water accompanying the closing of the flow control valve 75 based on the detection value of the pressure sensor SN5, and obtains the calculated value. Decide on a judgment amount. If the determination in step S5 is NO and the process proceeds to step S8, the flow control valve 75 may be kept fully open or fully closed. In this case, the process is terminated as it is (returns to step S1). After step S8, the process proceeds to step S10.

On the other hand, when the determination in step S7 is YES and the engine speed is equal to or higher than the reference speed, the process proceeds to step S9.

In step S9, the failure determination unit 103 calculates the amount of decrease in the pressure of the cooling water in the EGR cooling water path 63 due to the opening of the flow control valve 75, and sets it as the determination amount used in step S10. As shown in FIG. 5, when the flow control valve 75 opens (at time t11, etc.), the flow area of the cooling water increases, and the pressure of the cooling water in the EGR cooling water path 63 changes from P11 to P1. descend. In step S9, the amount of pressure drop is calculated. Specifically, from the pressure detected by the pressure sensor SN5 at the timing when the flow control valve 75 is closed, the timing after the flow control valve 75 is opened (when the flow control valve 75 is subsequently closed) The pressure detected by the pressure sensor SN5 at the timing before closing the valve is subtracted to calculate the pressure decrease amount. Then, this calculated value is determined as the determination amount.

Here, when the determination in step S5 is YES and step S6 is executed, the flow control valve 75 is changed from the closed state to the open state by the execution of step S6. Calculate the amount of pressure drop.

On the other hand, when the determination in step S5 is NO and the process proceeds to step S9, the cooling water control unit 102 changes the DUTY ratio of the flow control valve 75 from 100% to another value, or 100%. and greater than 0%, the flow control valve 75 is changed from the closed state to the open state. From this, when the determination is made, the failure determination unit 103 calculates the amount of pressure drop of the cooling water accompanying the opening of the flow control valve 75 based on the detection value of the pressure sensor SN5, and the calculated value is Decide on a judgment amount. If the determination in step S5 is NO and the process proceeds to step S9, the flow control valve 75 may be kept fully open or fully closed. In this case, the process is terminated as it is (returns to step S1). After step S9, the process proceeds to step S10.

In step S10, the failure determination unit 103 determines whether or not the determination amount (pressure increase amount or pressure decrease amount) determined in step S8 or step S9 is larger than a preset determination threshold value. If the determination is YES and the determination amount is larger than the determination threshold, the process proceeds to step S11, and the failure determination unit 103 determines that the flow control valve 75 is normal. On the other hand, if this determination is NO and the determination amount is equal to or less than the determination threshold value, the process proceeds to step S12, and the failure determination unit 103 determines that the flow control valve 75 is abnormal, that is, is out of order. The determination threshold value is preset to a value greater than 0 and stored in the failure determination unit 103 . That is, when the flow control valve 75 normally opens and closes as described above, the water hammer phenomenon occurs and the pressure of the cooling water rises, or the flow area increases and the pressure drops. These changes do not occur when the flow control valve 75 does not open and close normally. Therefore, in the present embodiment, when the determination amount is equal to or less than the determination threshold, it is determined that the flow control valve 75 is not opening and closing normally.

Note that even if the opening/closing frequency of the flow control valve 75 is set to the second frequency F2 in step S5, this opening/closing frequency is set to the first frequency when the processing of steps S6 to S12 ends and the process returns to step S1. It is returned to frequency F1.

Thus, in this embodiment, even when the engine water temperature is lower than the first temperature, the opening/closing command is issued to the flow control valve 75, and the flow rate is controlled based on the pressure change of the cooling water at this time. Failure determination of the control valve 75 is performed. Then, when the engine water temperature is lower than the first temperature and the failure determination has not been performed for the first time, the opening/closing frequency of the flow control valve 75 is increased. Here, in the present embodiment, the condition that the engine water temperature is lower than the first temperature and the first failure determination has not been performed corresponds to the "failure determination execution condition" in the claims.

In addition, when the engine speed is less than the reference speed in the first failure determination, it is determined whether the flow control valve 75 is out of order based on the amount of increase in pressure of the cooling water when the valve closing command is issued to the flow control valve 75. determine whether or not On the other hand, when the engine rotation speed is equal to or higher than the reference rotation speed in the first failure determination, the flow control valve 75 is determined to be out of order based on the amount of cooling water pressure drop when the valve closing command is issued to the flow control valve 75. determine whether or not

Next, the processing after step S21 that proceeds when the determination in step S4 is NO will be described.

In step S<b>21 , the failure determination unit 103 determines whether or not a valve closing command has been issued to the flow control valve 75 as in step S<b>6 . If the determination is NO and the closing command is not issued to the flow control valve 75, the process is terminated (returns to step S1). On the other hand, if this determination is YES and a valve closing command has been issued to the flow control valve 75, the process proceeds to step S22. In step S22, similar to step S7, the failure determination unit 103 determines that the pressure of the cooling water in the EGR cooling water path 63 rises due to the closing of the flow control valve 75, based on the detection value of the pressure sensor SN5. Calculate the amount and set it as the judgment amount. After step S22, the process proceeds to step S23. In step S23, the failure determination unit 103 determines whether or not the determination amount is greater than the determination threshold, as in step S10.

If the determination in step S23 is YES and the determination amount is greater than the determination threshold value, the process ends (returns to step S1). That is, the result of the initial failure determination is maintained. On the other hand, if the determination in step S23 is NO and the determination amount is equal to or less than the determination threshold, the process proceeds to step S24. In step S24, the abnormality counter is counted up. The abnormality counter is a counter that is incremented by 1 when the determination in step S23 is NO, and is reset to 0 when the engine stops. After step S24, the process proceeds to step S25.

In step S25, the failure determination unit 103 determines whether or not the abnormality counter is greater than the preset number of times of abnormality determination. If the determination in step S25 is YES and the abnormality counter is larger than the number of times of abnormality determination, the failure determination unit 103 proceeds to step S26, determines that the flow control valve 75 is abnormal, and terminates the process (step return to S1). On the other hand, if the determination in step S25 is NO and the abnormality counter is equal to or less than the number of times of abnormality determination, the failure determination unit 103 ends the process (returns to step S1). It should be noted that the number of abnormality determinations is preset to a value greater than 0 and stored in the failure determination unit 103 .

In this way, after the initial failure determination is completed, the flow control valve 75 fails based on the amount of pressure increase of the cooling water when the valve closing command is issued to the flow control valve 75 regardless of the engine speed. It is determined that the flow control valve 75 is abnormal when the number of times the pressure rise amount becomes equal to or less than the determination threshold is greater than the number of times of abnormality determination.

(4) Operation, etc. As described above, in the present embodiment, the flow control valve 75 malfunctions based on a change in the pressure of the cooling water in the EGR cooling water path 63 when the flow control valve 75 is opened or closed (at the time of the open/close command). It is determined whether or not As shown in FIG. 5, the cooling water pressure changes sensitively as the flow control valve 75 is opened and closed. Therefore, according to the present embodiment, whether or not the flow control valve 75 is out of order is determined based on the pressure change of the cooling water, so that this determination can be performed quickly and accurately. .

Here, if the flow control valve 75 is out of order, the amount of cooling water supplied to the engine body 1 cannot be controlled appropriately. It is necessary to determine whether On the other hand, after the engine is started, it is necessary to warm up the engine body 1, so the flow control valve 75 is closed to prevent the cooling water from being supplied to the engine body 1 through the EGR cooling water path 63. Prohibition is preferable.

On the other hand, in this embodiment, when the engine water temperature is lower than the first temperature, the flow control valve 75 is kept fully closed except when the failure determination of the flow control valve 75 is performed for the first time. When the engine water temperature is lower than the first temperature and the engine has not yet warmed up for the first failure determination, the opening/closing frequency F of the flow control valve 75 is set to the second frequency F2, and the opening/closing frequency at other times is The flow control valve 75 is driven to open and close while being higher than F1. In other words, the flow control valve 75 is opened and closed while the engine is being warmed up, and the open/close frequency at that time is increased to keep the valve opening time of the flow control valve 75 short. Therefore, it is possible to accelerate the warm-up of the engine while determining the failure of the flow control valve 75 at an early timing after the engine is started.

Further, in the present embodiment, when the engine coolant temperature is equal to or higher than the first temperature and the engine has been warmed up, opening and closing of the flow control valve 75 is permitted. The temperature of the engine body 1 can be made appropriate.

In particular, in this embodiment, the duty ratio of the flow control valve 75 is set so that the wall temperature of the combustion chamber 6 becomes the target wall temperature, and the flow control valve 75 is set so that the wall temperature of the combustion chamber 6 becomes the target wall temperature. 75 is opened and closed. Therefore, the wall temperature of the combustion chamber 6 can be more reliably set to a temperature suitable for combustion. In particular, in SPCCI combustion, it is necessary to compressively ignite part of the air-fuel mixture, and it is required to control the wall temperature of the combustion chamber 6 with high accuracy. In contrast, according to the present embodiment, the wall temperature of the combustion chamber 6 can be accurately controlled to an appropriate temperature, and appropriate SPCCI combustion can be achieved.

(5) Modification In the above embodiment, the wall temperature of the combustion chamber 6 is estimated based on the information from the second water temperature sensor SN4. is not limited to For example, the engine body 1 may be provided with a sensor that directly detects the wall temperature of the combustion chamber 6 .

Specific numerical values such as the first temperature and the second temperature shown in the above embodiment are merely examples. These temperatures can be changed as appropriate according to the specific configurations of the engine body 1 and the cooling device 60 .

In the above embodiment, an example in which the cooling device 60 is applied to an engine capable of partial compression ignition combustion (SPCCI combustion) has been described, but the combustion mode of the engine to which the cooling device 60 is applied is not limited to this. For example, the cooling device 60 can also be applied to an engine that is controlled so that the combustion mode in the entire operating range is SI combustion.

Reference Signs List 1 engine body 6 combustion chamber 60 cooling device 61 water pump 75 flow control valve 75a valve body of flow control valve 75b drive unit of flow control valve 100 PCM (control means)
160 Cooling water path SN5 Pressure sensor

Claims (4)

An engine cooling device,
a cooling water path for circulating cooling water through the engine body;
a flow control valve comprising: a valve body capable of opening and closing the cooling water path; and a driving section duty-driving the valve body so that the valve body opens and closes at a predetermined frequency;
a pressure sensor that detects the pressure of cooling water flowing through the cooling water path;
and a control means for controlling the flow control valve,
The control means controls the opening/closing frequency of the valve body of the flow control valve so that, when a predetermined failure determination condition is satisfied, the valve body is opened and closed in a state in which the switching frequency is higher than when the failure determination condition is not satisfied. An engine cooling device, comprising: controlling the drive unit, and determining whether or not the flow control valve is out of order based on the value detected by the pressure sensor when the valve body is opened or closed. In the engine cooling device according to claim 1,
The control means is
allowing the valve body to open when the temperature of the cooling water is equal to or higher than a predetermined set temperature;
An engine cooling system according to claim 1, wherein when the temperature of the cooling water is lower than the set temperature, opening and closing of the valve body is permitted only when the failure determination execution condition is satisfied. In the engine cooling device according to claim 2,
The control means performs the failure determination when the temperature of the cooling water is less than the set temperature and determination whether the flow control valve has failed has not been performed once since the engine was started. An engine cooling device, characterized in that it determines that a condition is established. In the engine cooling device according to claim 2 or 3,
When the temperature of the cooling water is equal to or higher than the set temperature, the control means opens and closes the valve body so that the wall temperature of a combustion chamber formed in the engine body reaches a preset target temperature. engine cooling system.

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