JP2011099370A - Engine cooling system and method for controlling the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine cooling system and a method for controlling the same, improving the combustibility of an engine. <P>SOLUTION: This cooling system for the engine 1 includes: a first cooling water passage L1 including the water jacket of an engine body 11 and circulating therein a coolant; and a second cooling water passage L2 including an EGR cooler 19 and circulating therein the coolant. An EGR valve 20 regulating intake volume supplied from the EGR cooler 19 to a combustion chamber 111 is provided on an EGR passage 18 for connecting the EGR cooler 19 to the combustion chamber 111 of the engine 1. When coolant temperature reaches a temperature threshold T1 or higher, an engine control unit 3 opens a cutoff valve 15, and allows the first cooling water passage L1 to communicate with the second cooling water passage L2. When the cutoff valve 15 is displaced from a closed sate to an open state, the operation of the EGR valve 20 is stopped, fixing the opening the EGR valve then. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an engine cooling system and a control method thereof.

  As a conventional technique related to a cooling system for a vehicle engine, there is one provided with a heater core for heating a vehicle interior (see, for example, Patent Document 1). This includes a first cooling water path through which cooling water circulates between the exhaust heat recovery unit and the heater core, and a second cooling water path through which cooling water circulates between the exhaust heat recovery unit and the water jacket of the engine. I have.

  And when it determines with cooling water being comparatively low temperature based on the detected value by the water temperature sensor provided in the 1st cooling water path | route, in the location which connects a 1st cooling water path | route and a 2nd cooling water path | route The three-way valve provided is operated, and the cooling water is circulated in the first cooling water path without circulating the cooling water in the second cooling water path.

Further, when the cooling water temperature rises, the three-way valve is operated to circulate the cooling water also in the second cooling water path.
By doing so, the cooling water in the water jacket is not circulated to the heater core when the cooling water is warmed, so that excessive cooling of the engine can be prevented. Moreover, since a large amount of cooling water is not circulated through the heater core when the cooling water is heated, the heating effect of the heater core can be enhanced.

JP 2008-208716 A

In recent years, vehicles equipped with an EGR (Exhaust Gas Recirculation) cooler have become widespread in engine cooling systems. The EGR cooler has an exhaust gas passage from the engine body inside, and the engine coolant passes through the passage to exchange heat between the exhaust gas and the coolant. The gas is cooling. The cooled exhaust gas is introduced into the intake side of the engine body as intake air. In this way, a part of the exhaust gas is returned to the intake system and mixed with the air-fuel mixture, thereby lowering the combustion temperature and reducing the amount of NO _x generated by the exhaust gas.

  Normally, an EGR valve is provided on a passage connecting the EGR cooler and the intake side of the engine, and the opening degree of the EGR valve is controlled based on the amount of fuel injected into the combustion chamber. Thus, the amount of intake air supplied from the EGR cooler to the combustion chamber is adjusted according to the state of the vehicle at that time.

However, as described above, in the engine cooling system, when there is a change in the circulation path of the cooling water, the temperature of the cooling water flowing into the EGR cooler may change rapidly. At this time, fluctuations in the coolant temperature affect the cooling performance of the EGR cooler, leading to fluctuations in the intake air temperature introduced from the EGR cooler into the combustion chamber of the engine. As a result, the engine combustibility is deteriorated and the emission is adversely affected.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an engine cooling system and a control method thereof that can improve the combustibility of the engine.

  In order to solve the above-described problem, the structural features of the engine cooling system according to claim 1 include a first cooling water path through which cooling water circulates including a water jacket of the engine, A cooling water circulates including an EGR cooler for cooling the exhaust, and a second cooling water path formed so as to merge with the first cooling water path on the downstream side of the EGR cooler, the first cooling water path and the second cooling water path A cooling water pumping means capable of circulating the cooling water in the cooling water path and a passage connecting the EGR cooler and the combustion chamber of the engine are provided on the passage of the cooling water from the EGR cooler by increasing or decreasing the opening degree. A flow rate adjusting means for adjusting the amount of gas supplied to the vehicle, an EGR control means for controlling the opening of the flow rate adjusting means based on the state of the vehicle, a first cooling water path, An on-off valve that intermittently connects between the jacket and the merging point to the second cooling water path, water temperature detection means for detecting the cooling water temperature of at least one of the first cooling water path or the second cooling water path, In an engine cooling system comprising an on-off valve control means for controlling the operation of the on-off valve based on the coolant temperature detected by the water temperature detecting means, the EGR control means changes the on-off valve from the closed state to the open state. In the case of displacement, the opening degree control of the flow rate adjusting means is stopped.

  The structural feature of the invention according to claim 2 is that, in the engine cooling system of claim 1, when the on-off valve is displaced from the closed state to the open state, the opening degree of the flow rate adjusting means is adjusted at that time. When the cooling water temperature detected by the water temperature detecting means is stabilized after the opening and closing valve is fixed, the opening degree control of the flow rate adjusting means is resumed.

  The structural feature of the invention according to claim 3 is that the engine cooling system of claim 1 opens and closes when the coolant temperature detected by the coolant temperature detecting means is less than the first threshold value or less than the first threshold value. When the valve is closed and the cooling water temperature detected by the water temperature detection means is equal to or higher than the first threshold value or higher than the first threshold value, the on-off valve is opened and the cooling water temperature detected by the water temperature detection means is When the second threshold value, which is lower than the first threshold value by a predetermined temperature, is reached, the opening degree control of the flow rate adjusting means is stopped and the flow rate adjusting means is fully closed and fixed.

  The structural feature of the invention according to claim 4 is that in the engine cooling system according to claim 3, the cooling water detected by the water temperature detecting means while the flow rate adjusting means is displaced toward the fully closed state. When the temperature reaches the first threshold value, the flow rate adjustment means is fixed at that time, and after the on-off valve is opened, the flow rate is determined when the coolant temperature detected by the water temperature detection means is stable. It is to restart the opening degree control of the adjusting means.

  The structural feature of the invention according to claim 5 is the engine cooling system according to claim 3 or 4, wherein the second cooling water path is provided on the downstream side of the junction with the first cooling water path. And an exhaust heat recovery unit provided on the upstream side of the heater core, and the water temperature detecting means is a first provided in the water jacket or between the water jacket on the first cooling water path and the on-off valve. 1 water temperature sensor and a second water temperature sensor provided between the junction of the first cooling water path on the second cooling water path and the heater core, and the on-off valve is controlled by the first water temperature sensor. The cooling water temperature detected when the detected cooling water temperature and the cooling water temperature detected by the second water temperature sensor are both less than the first threshold value or less than the first threshold value and detected by the first water temperature sensor. And at least one of the cooling water temperature detected by the second temperature sensor is to be opened when higher than the first threshold value or more or the first threshold value.

The structural feature of the invention according to claim 6 is the engine cooling system according to claim 5, wherein the cooling water pumping means is a water pump formed on the downstream side of the heater core on the second cooling water path, Between the confluence on the second cooling water path and the upstream side of the water pump, it is shared as a part of the first cooling water path, and the water pump uses the water jacket and the exhaust heat recovery device for the sucked cooling water. It is discharging toward both sides.

  According to a seventh aspect of the present invention, the cooling system includes a first cooling water path through which cooling water circulates including a water jacket of the engine, and exhaust from the engine. A cooling water circulates including an EGR cooler to be cooled, and is formed so as to merge with the first cooling water path on the downstream side of the EGR cooler, and the first cooling water path and the second cooling water. A cooling water pumping means capable of circulating the cooling water in the path and a passage connecting the EGR cooler and the combustion chamber of the engine are provided from the EGR cooler to the combustion chamber by increasing or decreasing the opening degree. A flow rate adjusting means for adjusting the amount of gas to be generated, an on-off valve provided on the first cooling water path and intermittently connecting between the water jacket and the junction point to the second cooling water path, Water temperature detecting means for detecting the cooling water temperature of at least one of the water path and the second cooling water path, and controls the operation of the on-off valve based on the cooling water temperature detected by the water temperature detecting means. In addition, in the engine cooling method for controlling the opening degree of the flow rate adjusting means based on the state of the vehicle, the opening degree control of the flow rate adjusting means is stopped when the on-off valve is displaced from the closed state to the open state. That is.

  According to the engine cooling system of the first aspect, when the on-off valve is displaced from the closed state to the open state, the cooling water is the first cooling water by stopping the opening degree control of the flow rate adjusting means. Even if the temperature of the cooling water flowing from the path toward the second cooling water path and passing through the EGR cooler fluctuates, the fluctuation of the intake air temperature introduced from the EGR cooler to the combustion chamber of the engine can be minimized. .

  That is, when the opening control of the flow rate adjusting means is executed when the cooling water flows from the first cooling water path toward the second cooling water path, the influence of the fluctuation of the cooling water temperature and the flow rate adjusting means The effects of the opening degree control may be superimposed on each other, and the intake air temperature introduced into the combustion chamber may vary greatly.

  However, when the cooling water flows from the first cooling water path toward the second cooling water path, the opening degree control of the flow rate adjusting means is stopped, so that only the influence of the fluctuation of the cooling water temperature on the intake air temperature is affected. Therefore, the fluctuation of the intake air temperature introduced into the combustion chamber can be minimized, and the combustion property of the engine can be improved.

According to the engine cooling system of the second aspect, when the on-off valve is displaced from the closed state to the open state, the opening degree of the flow rate adjusting means is fixed at that time, so that the EGR cooler and the combustion chamber are fixed. Therefore, the intake air amount supplied to the combustion chamber is not changed, the influence of the opening degree control of the flow rate adjusting means on the intake air temperature is completely eliminated, and the fluctuation of the intake air temperature introduced into the combustion chamber can be minimized.
In addition, when the cooling water temperature detected by the water temperature detecting means is stabilized after the on-off valve is opened, the intake air temperature introduced into the combustion chamber is reduced by resuming the opening degree control of the flow rate adjusting means. The opening degree control of the flow rate adjusting means can be smoothly resumed without fluctuation.

According to the engine cooling system of the third aspect, when the cooling water temperature detected by the water temperature detecting means is equal to or higher than the first threshold or higher than the first threshold, the on-off valve is opened, and the water temperature detecting means When the coolant temperature detected by the above reaches a second threshold value that is lower than the first threshold value by a predetermined temperature, the opening control of the flow rate adjusting means is stopped, and the flow rate adjusting means is fully closed and fixed. Before the on-off valve is opened, the supply of intake air from the EGR cooler to the combustion chamber can be stopped, and the fluctuation of the intake air temperature introduced into the combustion chamber can be reliably prevented.

  According to the engine cooling system of the fourth aspect, when the coolant temperature detected by the water temperature detecting means reaches the first threshold value while the flow rate adjusting means is displaced toward the fully closed state, The opening degree of the flow rate adjusting means is fixed at that time, and the opening degree control of the flow rate adjusting means is resumed when the cooling water temperature detected by the water temperature detecting means is stabilized after the on-off valve is opened. Thus, when the coolant temperature in the engine rises in the middle of the displacement of the flow rate adjusting means, the cooling water circulation in the engine is prioritized and executed with respect to the closing operation of the flow rate adjusting means. Boiling of cooling water can be prevented.

  According to the engine cooling system of the fifth aspect, the on-off valve has the cooling water temperature detected by the first water temperature sensor included in the first cooling water path and the second cooling water path included in the second cooling water path. The cooling water temperature detected by the two water temperature sensors is closed when both are less than the first threshold value or below the first threshold value, and the cooling water temperature detected by the first water temperature sensor and the second water temperature sensor detect the cooling water temperature. The valve is opened when at least one of the cooling water temperatures is equal to or higher than the first threshold value or higher than the first threshold value, so that the cooling water in the water jacket can be heated quickly and the heating effect by the heater core is improved. Can be made.

  That is, the on-off valve is closed when the cooling water temperature detected by the first water temperature sensor and the cooling water temperature detected by the second water temperature sensor are both less than the first threshold value or less than the first threshold value. Thus, the cooling water in the water jacket is prevented from flowing out to the second cooling water path, and the cooling water in the water jacket can be warmed early by the combustion heat in the engine. Moreover, since the low-temperature cooling water in a water jacket does not reach a heater core, the heating effect by a heater core can also be improved.

  On the other hand, the opening / closing valve is opened when at least one of the cooling water temperature detected by the first water temperature sensor and the cooling water temperature detected by the second water temperature sensor is equal to or higher than the first threshold value or higher than the first threshold value. By being valved, the cooling water in the water jacket and the cooling water in the heater core are mixed, and the cooling water circulating through both can be heated quickly.

  According to the engine cooling system of the sixth aspect, the cooling water pumping means is a water pump formed on the second cooling water path, and the merging point on the second cooling water path and the upstream side of the water pump. Is shared as a part of the first cooling water path, and the water pump discharges the sucked cooling water toward both the water jacket and the exhaust heat recovery device, thereby allowing one pump to The cooling water in the first cooling water path and the second cooling water path can be circulated.

  According to the engine cooling system control method of the seventh aspect, when the on-off valve is displaced from the closed state to the open state, the cooling water is first controlled by stopping the opening degree control of the flow rate adjusting means. Even when the temperature of the cooling water flowing from the cooling water path toward the second cooling water path and passing through the EGR cooler fluctuates, the fluctuation of the intake air temperature introduced from the EGR cooler into the combustion chamber of the engine is minimized. Can do.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a simplified diagram showing an engine cooling system according to Embodiment 1 of the present invention; The figure which showed the state when the shut-off valve is in an open state in the cooling system shown in FIG. The figure which showed the flowchart showing the control method of the engine cooling system shown in FIG. The figure which showed the first half of the flowchart showing the control method of the cooling system of the engine by Embodiment 2. The figure which showed the second half of the flowchart showing the control method of the engine cooling system by Embodiment 2 The figure which showed the time chart showing the operating state of each structure at the time of performing the control method of the engine cooling system shown in FIG. 4 and FIG. The figure which showed the time chart showing the operating state of each structure when a cooling water temperature reaches the threshold value which makes a shut-off valve an open state in the middle of the displacement of an EGR valve toward a fully closed state A simplified diagram showing an engine cooling system according to a third embodiment.

<Embodiment 1>
An engine cooling system according to Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 shows an engine body 11 constituting a vehicle engine 1, a cooling system for the engine 1, and an engine control unit 3 for controlling them (corresponding to the on-off valve control means and the EGR control means of the present invention). . The engine body 11 is formed by a cylinder block including a combustion chamber 111, a cylinder head, and other auxiliary machines, and has a water jacket (not shown) in which coolant, which is cooling water, circulates. . The engine body 11 is controlled in rotation by the intake air amount, fuel injection amount, and the like adjusted by the engine control unit 3 (indicated by S1 in FIG. 1).

The heater core 12 is a heater that sends warm air into the passenger compartment. A water channel through which the coolant passes is formed inside the heater core 12. Air is blown around the water channel by a blower, and heat is exchanged between the air and the coolant to heat the air. The heater core 12 is selected between an operating state and a non-operating state when the occupant operates a switch in the passenger compartment. The heater core 12 is electrically connected to the engine control unit 3 and inputs a signal indicating a target hot air temperature to the engine control unit 3 (indicated by S2 in FIG. 1).
The heater core 12 and the engine main body 11 are connected by a pipe line, and a loop-shaped first cooling water passage L1 (the first cooling water of the present invention) between the water jacket of the engine main body 11 and the heater core 12 is circulated. Corresponding to the route) is formed.

  The exhaust heat recovery unit 13 is disposed on an exhaust gas passage from the engine body 11 and has a water passage through which coolant passes. The exhaust heat recovery device 13 heats the coolant by exchanging heat between the exhaust gas and the coolant. The exhaust heat recovery unit 13 and the heater core 12 are connected by a pipe line, and a loop-shaped second cooling water passage L2 in which coolant circulates between the exhaust heat recovery unit 13 and the heater core 12 (second cooling according to the present invention). (Corresponding to the water pathway) is formed. As shown in FIG. 1, the exhaust heat recovery device 13 is formed on the upstream side of the heater core 12 in the second cooling water passage L <b> 2.

  The first cooling water passage L1 joins the second cooling water passage L2 at the connection portion P1 (corresponding to the joining point of the present invention) located between the water jacket and the heater core 12. In other words, the second cooling water passage L2 joins the first cooling water passage L1 on the downstream side of the exhaust heat recovery device 13 and on the upstream side of the heater core 12.

  In the second cooling water passage L2, an electric pump 14 (corresponding to the cooling water pumping means and the water pump of the present invention) is provided on the downstream side of the heater core 12. The electric pump 14 is a fluid pressure pump that is driven by an electric motor (not shown). The operation of the electric pump 14 is controlled by the engine control unit 3 described above (indicated by S3 in FIG. 1).

In the second cooling water passage L2, the connection portion P1 and the upstream side of the electric pump 14 are shared as a part of the first cooling water passage L1, and the electric pump 14 removes the sucked coolant from the engine body 11. The coolant is discharged toward both the water jacket and the exhaust heat recovery unit 13, and the coolant is circulated in the first cooling water passage L1 and the second cooling water passage L2.

  A shutoff valve 15 (corresponding to the on-off valve of the present invention) is provided in the connection path L11 located between the engine body 11 and the connection portion P1 on the first coolant passage L1. The shut-off valve 15 is not particularly limited to a specific type, type, and operating principle, but a rotary valve, a needle valve, or the like is applicable. A signal indicating the open / close state of the shut-off valve 15 is input to the engine control unit 3, and the engine control unit 3 controls the open / close valve 15 to open / close between the water jacket and the connection portion P1. (Indicated by S4 in FIG. 1).

  A first temperature sensor D1 (corresponding to the water temperature detecting means and the first water temperature sensor of the present invention) is provided between the engine body 11 and the shutoff valve 15 on the connection path L11. The first temperature sensor D1 is a temperature sensor that detects the coolant temperature in the connection path L11, and a signal indicating the detected temperature is input to the engine control unit 3 (indicated by S5 in FIG. 1). The first temperature sensor D1 does not necessarily have to be provided on the connection path L11, and may be provided in the water jacket of the engine body 11.

  Furthermore, a second temperature sensor D2 (corresponding to the water temperature detecting means and the second water temperature sensor of the present invention) is provided in the introduction path L21 formed between the connecting portion P1 and the heater core 12 on the second cooling water passage L2. ) Is provided. The second temperature sensor D2 is a temperature sensor that detects the coolant temperature in the introduction path L21. Like the first temperature sensor D1, a signal indicating the detected temperature is input to the engine control unit 3 (S6 in FIG. 1). Show).

  From the combustion chamber 111 of the engine body 11, an exhaust passage 16 through which exhaust gas is discharged is drawn out and connected to an exhaust port (not shown). An intake passage 17 extends from an air cleaner (not shown) into the combustion chamber 111, and combustion air is supplied into the combustion chamber 111 through the intake passage 17. Intermediate portions of the exhaust passage 16 and the intake passage 17 are connected to each other by an EGR passage 18.

On the EGR passage 18, an EGR (Exhaust Gas Recirculation) cooler 19 and an EGR valve 20 (corresponding to the flow rate adjusting means of the present invention) are formed in series with each other. The EGR cooler 19 has an exhaust gas passage from the combustion chamber 111 formed therein, and is formed so that the coolant of the second cooling water passage L2 can circulate around the exhaust gas passage. As shown in FIG. 1, the EGR cooler 19 is provided on the upstream side of the exhaust heat recovery unit 13 on the second cooling water passage L2.

  A part of the exhaust gas discharged to the exhaust passage 16 reaches the EGR cooler 19 via the EGR passage 18. The EGR cooler 19 cools the exhaust gas by exchanging heat between the exhaust gas and the coolant. The cooled exhaust gas is supplied to the combustion chamber 111 as intake air via the EGR valve 20 on the EGR passage 18.

  The EGR valve 20 is formed to change its opening degree by operating a stepping motor (not shown). The engine control unit 3 to which the opening degree signal from the EGR valve 20 is input adjusts the opening degree of the EGR valve 20 based on the rotational speed of the engine body 11, the fuel injection amount into the combustion chamber 111, and the intake air amount. (Indicated by S7 in FIG. 1). By increasing or decreasing the opening degree of the EGR valve 20, it is possible to adjust the amount of intake air that is cooled by the EGR cooler 19 and supplied to the combustion chamber 111. Hereinafter, adjustment of the opening degree of the EGR valve 20 by the engine control unit 3 is referred to as opening degree control.

  Further, one end of a cooling path L3 is connected between the engine body 11 and the first temperature sensor D1 on the connection path L11. The other end of the cooling path L3 is connected to a common path L12 for the first cooling water passage L1 and the second cooling water passage L2. A known radiator 21 is provided on the cooling path L3. Further, a known thermostat 22 is disposed at a connection portion between the cooling path L3 and the common path L12. The thermostat 22 is closed when the temperature of the coolant is low, and is opened when the coolant temperature reaches a predetermined value, thereby connecting the cooling path L3 and the common path L12.

  The first cooling water passage L1, the second cooling water passage L2, the cooling passage L3, the water jacket of the engine body 11, the heater core 12, the exhaust heat recovery device 13, the electric pump 14, the shutoff valve 15, the EGR cooler 19, and the EGR valve. 20, a cooling system of the engine 1 is formed by the radiator 21, the thermostat 22, the first temperature sensor D1, and the second temperature sensor D2. For the present invention, the cooling system of the engine 1 does not necessarily require all of the above-described configurations, and may be formed by appropriately selecting the necessary configurations.

  Next, an operation method of the cooling system of the engine 1 will be described. As shown in FIG. 1, for example, when the engine 1 is started, the coolant is at a low temperature, and both the detected values by the first temperature sensor D1 and the second temperature sensor D2 are set to a predetermined temperature threshold value T1 (the first threshold value of the present invention). If it is less than that, the engine control unit 3 closes the shut-off valve 15.

  Therefore, the coolant pumped by the electric pump 14 does not flow through the first cooling water passage L1, but circulates only through the second cooling water passage L2 (indicated by solid arrows in FIG. 1). Since the coolant in the water jacket of the engine body 11 does not flow out of the engine body 11, it is heated early by the combustion heat in the engine body 11.

  The coolant that circulates through the second cooling water passage L <b> 2 is discharged from the electric pump 14, cools the exhaust gas in the EGR cooler 19, is heated, and is sent to the exhaust heat recovery unit 13. The coolant is further heated in the exhaust heat recovery device 13 and then reaches the heater core 12. The coolant that has heated the air for blowing in the heater core 12 (the coolant itself is cooled in the heater core 12) is sucked again by the electric pump 14 through the common path L12 and then discharged toward the EGR cooler 19. .

  When the coolant in the water jacket is heated by the operation of the engine body 11, the detected value of the coolant temperature by the first temperature sensor D1 becomes equal to or higher than the temperature threshold value T1. Further, since the coolant circulating in the second coolant passage L2 is also heated by the EGR cooler 19 and the exhaust heat recovery device 13, the detected value of the coolant temperature by the second temperature sensor D2 becomes equal to or higher than the temperature threshold T1.

  When at least one of the detected values by the first temperature sensor D1 and the second temperature sensor D2 becomes equal to or higher than the temperature threshold value T1, the engine control unit 3 opens the shut-off valve 15, and as shown in FIG. The water jacket of the main body 11 and the heater core 12 are communicated. Therefore, the coolant pumped by the electric pump 14 circulates from the engine body 11 to the first cooling water passage L1 in addition to the second cooling water passage L2 (indicated by a thick arrow in FIG. 2). ).

The coolant circulating in the first coolant passage L1 is heated in the water jacket of the engine body 11 and then sent to the heater core 12 via the connection path L11 and the introduction path L21. The coolant cooled in the heater core 12 is sucked by the electric pump 14 through the common path L12 and discharged again toward the engine body 11 and the EGR cooler 19.
Further, when the temperature of the coolant in the common path L12 rises and the thermostat 22 opens, the coolant flows out from the engine body 11 to the cooling path L3 and is cooled by the radiator 21 (in FIG. Show).

  Next, a method for controlling the cooling system of the engine 1 by the engine control unit 3 will be described with reference to FIG. First, when the engine control unit 3 is initialized, the opening degree control of the EGR valve 20 is executed based on the rotation speed of the engine body 11, the fuel injection amount into the combustion chamber 111, and the intake air amount (step S301). .

  At the same time, the engine control unit 3 also performs operation control of the shutoff valve 15 (step S302). As described above, the operation control of the shutoff valve 15 means that the shutoff valve 15 is closed when both the detected values by the first temperature sensor D1 and the second temperature sensor D2 are less than the temperature threshold value T1, and the first temperature is detected. This is open / close control that opens the shutoff valve 15 when at least one of the detection values of the sensor D1 and the second temperature sensor D2 is equal to or higher than the temperature threshold T1.

  Next, it is determined whether or not the cutoff valve 15 is operating (displaced) from the closed state to the open state (step S303). When it is determined that the shut-off valve 15 is not displaced from the closed state to the open state, this control is terminated. When it is determined that the shutoff valve 15 is being displaced from the closed state toward the open state, the opening control of the EGR valve 20 is stopped and the opening at that time is fixed (step S304). Therefore, the intake air amount supplied from the EGR cooler 19 to the combustion chamber 111 is also fixed at this time and does not fluctuate.

  Thereafter, it is determined whether or not the displacement of the shutoff valve 15 toward the open state is completed (step S305). If it is determined that the shutoff valve 15 is still being displaced toward the open state, the operation of the EGR valve 20 is stopped (step S304). If it is determined that the displacement of the shut-off valve 15 to the open state has been completed, it is determined whether or not the coolant temperature detected by the first temperature sensor D1 and the second temperature sensor D2 is stable (step S306). . Although not limited to this method, for example, when the time derivative of the detected coolant temperature is less than a predetermined value, the coolant temperature may be assumed to be stable.

In step S306, the coolant temperature may be stabilized when both of the coolant temperatures detected by the first temperature sensor D1 and the second temperature sensor D2 satisfy the condition, or the first temperature sensor D1 and The coolant temperature may be stabilized when at least one of the coolant temperatures detected by the second temperature sensor D2 satisfies the condition.
When it is determined that the coolant temperature is not stable, the operation of the EGR valve 20 is continuously stopped (step S304). When it is determined that the coolant temperature is stable, the opening degree control of the EGR valve 20 is resumed (step S307).

  According to the present embodiment, when the shutoff valve 15 is displaced from the closed state to the open state, the coolant is stopped from the first cooling water passage L1 and the second cooling water by stopping the opening degree control of the EGR valve 20. Even if the coolant temperature flowing into the passage L2 and passing through the EGR cooler 19 varies, the variation in the intake air temperature introduced from the EGR cooler 19 into the combustion chamber 111 of the engine body 11 can be minimized.

  That is, when the opening degree control of the EGR valve 20 is executed when the coolant flows from the first cooling water passage L1 toward the second cooling water passage L2, the influence of the variation in the coolant temperature and the EGR valve 20 are controlled. The effects of the opening degree control may be superimposed on each other, and the intake air temperature introduced into the combustion chamber 111 may vary greatly.

  However, when the coolant flows from the first cooling water passage L1 toward the second cooling water passage L2, the opening degree control of the EGR valve 20 is stopped, so that only the influence of the fluctuation of the coolant temperature on the intake air temperature is affected. Therefore, fluctuations in the intake air temperature introduced into the combustion chamber 111 can be minimized, and the combustibility of the engine body 11 can be improved.

  Further, when the shutoff valve 15 is displaced from the closed state to the open state, the opening amount of the EGR valve 20 is fixed so that the intake air amount supplied from the EGR cooler 19 to the combustion chamber 111 does not fluctuate. Further, the influence of the opening degree control of the EGR valve 20 on the intake air temperature can be eliminated, and the fluctuation of the intake air temperature introduced into the combustion chamber 111 can be minimized.

  Further, after the shutoff valve 15 is opened, when the coolant temperature detected by the first temperature sensor D1 and the second temperature sensor D2 is stabilized, the opening degree control of the EGR valve 20 is resumed, thereby causing combustion. The opening control of the EGR valve 20 can be smoothly restarted without changing the temperature of the intake air introduced into the chamber 111.

  Further, the shutoff valve 15 includes a coolant temperature detected by the first temperature sensor D1 included in the first cooling water passage L1 and a coolant detected by the second temperature sensor D2 included in the second cooling water passage L2. The valve is closed when both temperatures are lower than the temperature threshold T1, and at least one of the coolant temperature detected by the first temperature sensor D1 and the coolant temperature detected by the second temperature sensor D2 is equal to or higher than the temperature threshold T1. When the valve is opened at this time, the coolant in the water jacket can be heated quickly, and the heating effect by the heater core 12 can be improved.

  That is, when the coolant temperature detected by the first temperature sensor D1 and the coolant temperature detected by the second temperature sensor D2 are both less than the temperature threshold T1, the water jacket is closed by closing the shutoff valve 15. The coolant in the water jacket is prevented from flowing out into the second coolant passage L2, and the coolant in the water jacket can be quickly heated by the combustion heat in the engine body 11. Further, since the low-temperature coolant in the water jacket does not reach the heater core 12, the heating effect by the heater core 12 can be improved.

  On the other hand, the shutoff valve 15 is opened when at least one of the coolant temperature detected by the first temperature sensor D1 and the coolant temperature detected by the second temperature sensor D2 is equal to or higher than the temperature threshold T1. Thus, the coolant in the water jacket and the coolant in the heater core 12 are mixed, and the coolant circulating through both can be heated quickly.

  In addition, an electric pump 14 is provided on the second cooling water passage L2 as a cooling water pumping means, and the first cooling water passage L1 is provided between the connection portion P1 on the second cooling water passage L2 and the upstream side of the electric pump 14. The electric pump 14 discharges the sucked coolant toward both the water jacket and the exhaust heat recovery unit 13, thereby allowing the first cooling water passage L <b> 1 and the second cooling water passage L <b> 1 and the second coolant pump to be discharged by one pump. The coolant in the cooling water passage L2 can be circulated.

<Embodiment 2>
Next, Embodiment 2 of the present invention will be described based on FIGS. The present embodiment is a control method different from the first embodiment for the cooling system of the engine 1 shown in FIG. FIG. 6 is a time chart showing the operating states of the EGR valve 20 and the shutoff valve 15 when the closing operation of the EGR valve 20 is completed before the coolant temperature reaches the temperature threshold T1. FIG. 7 is a time chart showing the operating states of the EGR valve 20 and the shutoff valve 15 when the coolant temperature reaches the temperature threshold T1 while the EGR valve 20 is in the closing operation.

First, when the engine control unit 3 is initialized, the opening degree control of the EGR valve 20 is executed (step S401, indicated by a in FIG. 6 and e in FIG. 7). At the same time, the engine control unit 3 also performs operation control of the shutoff valve 15 (step S402).
Next, it is determined whether or not the shutoff valve 15 is in a closed state (step S403). When it is determined that the shutoff valve 15 is not closed, this control is terminated. When it is determined that the shutoff valve 15 is in the closed state, it is determined whether or not the coolant temperature thw1 detected by the first temperature sensor D1 is equal to or higher than the temperature threshold T2 (corresponding to the second threshold of the present invention). Determination is made (step S404). The temperature threshold T2 is set to a temperature that is lower than the temperature threshold T1 described above by a predetermined temperature.

  When it is determined that the coolant temperature thw1 detected by the first temperature sensor D1 is lower than the temperature threshold T2, whether or not the coolant temperature thw2 detected by the second temperature sensor D2 is equal to or higher than the temperature threshold T2 is determined. Determination is made (step S405). When it is determined that the coolant temperature thw2 detected by the second temperature sensor D2 is lower than the temperature threshold value T2, this control flow ends.

  When it is determined that the coolant temperature thw1 detected by the first temperature sensor D1 is equal to or higher than the temperature threshold T2, or the coolant temperature thw2 detected by the second temperature sensor D2 is determined to be equal to or higher than the temperature threshold T2. In this case, the opening control of the EGR valve 20 is stopped, and the closing operation of the EGR valve 20 is started toward the fully closed state (step S406, indicated by b in FIG. 6 and f in FIG. 7).

  Thereafter, it is determined whether or not the closing operation of the EGR valve 20 has been completed and the EGR valve 20 has been completely closed (step S501 in FIG. 5). When it is determined that the closing operation of the EGR valve 20 is completed, the EGR valve 20 is fixed in a completely closed state, and the coolant temperature thw1 detected by the first temperature sensor D1 is equal to or higher than the temperature threshold T1 described above. It is determined whether or not there is (step S509). When the EGR valve 20 is fixed in a closed state, the supply of intake air from the EGR cooler 19 to the combustion chamber 111 is stopped.

  When it is determined that the coolant temperature thw1 detected by the first temperature sensor D1 is lower than the temperature threshold T1, whether or not the coolant temperature thw2 detected by the second temperature sensor D2 is equal to or higher than the temperature threshold T1. Determination is made (step S510). When it is determined that the coolant temperature thw2 detected by the second temperature sensor D2 is less than the temperature threshold T1, the process returns to step S509, and the coolant temperature thw1 detected by the first temperature sensor D1 is again set as the temperature threshold. It is determined whether or not T1 or more.

  When it is determined that the coolant temperature thw1 detected by the first temperature sensor D1 is equal to or higher than the temperature threshold T1, or the coolant temperature thw2 detected by the second temperature sensor D2 is determined to be equal to or higher than the temperature threshold T1. In this case, the shutoff valve 15 starts to be displaced from the closed state to the open state (step S511, indicated by c in FIG. 6).

  Thereafter, it is determined whether or not the displacement of the shut-off valve 15 toward the open state has been completed (step S512). If it is still determined that the shut-off valve 15 is being displaced toward the open state, The displacement is continued (step S511). When it is determined that the displacement of the shutoff valve 15 to the open state is completed, it is determined whether or not the coolant temperatures thw1 and thw2 detected by the first temperature sensor D1 and the second temperature sensor D2 are stable ( Step S513).

Also in step S513, as described above, when both the coolant temperatures thw1 and thw2 detected by the first temperature sensor D1 and the second temperature sensor D2 satisfy the conditions, the coolant temperature may be stabilized. The coolant temperature may be stabilized when at least one of the coolant temperatures thw1 and thw2 detected by the first temperature sensor D1 and the second temperature sensor D2 satisfies the condition.
When it is determined that the coolant temperature is not stable, the open state of the shutoff valve 15 is continued (step S511). When it is determined that the coolant temperature is stable, the opening degree control of the EGR valve 20 is resumed (step S508, indicated by d in FIG. 6).

On the other hand, if it is determined in step S501 that the EGR valve 20 is in the closing operation toward the fully closed state, whether or not the coolant temperature thw1 detected by the first temperature sensor D1 is equal to or higher than the temperature threshold T1. Is determined (step S502).
When it is determined that the coolant temperature thw1 detected by the first temperature sensor D1 is lower than the temperature threshold T1, whether or not the coolant temperature thw2 detected by the second temperature sensor D2 is equal to or higher than the temperature threshold T1. Determination is made (step S503). When it is determined that the coolant temperature thw2 detected by the second temperature sensor D2 is lower than the temperature threshold value T1, the process returns to step S501, and it is determined again whether or not the closing operation of the EGR valve 20 is completed. .

  While the EGR valve 20 is in the closing operation toward the fully closed state, when it is determined that the coolant temperature thw1 detected by the first temperature sensor D1 is equal to or higher than the temperature threshold value T1, or detected by the second temperature sensor D2. If it is determined that the coolant temperature thw2 is equal to or higher than the temperature threshold value T1, the EGR valve 20 is deactivated, and the opening at that time is fixed (step S504). Therefore, the intake air amount supplied from the EGR cooler 19 to the combustion chamber 111 is also fixed at this time and does not fluctuate. At the same time, displacement of the shut-off valve 15 from the closed state to the open state is started (step S505, indicated by g in FIG. 7).

  Thereafter, it is determined whether or not the displacement of the shut-off valve 15 toward the open state has been completed (step S506). If it is still determined that the shut-off valve 15 is being displaced toward the open state, the EGR valve 20 The operation stop (step S504) and the displacement of the shut-off valve 15 (step S505) are continued. When it is determined that the displacement of the shutoff valve 15 to the open state is completed, it is determined whether or not the coolant temperatures thw1 and thw2 detected by the first temperature sensor D1 and the second temperature sensor D2 are stable ( Step S507).

  Also in step S507, as described above, when both the coolant temperatures thw1 and thw2 detected by the first temperature sensor D1 and the second temperature sensor D2 satisfy the conditions, the coolant temperature may be stabilized. The coolant temperature may be stabilized when at least one of the coolant temperatures thw1 and thw2 detected by the first temperature sensor D1 and the second temperature sensor D2 satisfies the condition.

  When it is determined that the coolant temperature is not stable, the operation stop of the EGR valve 20 (step S504) and the displacement of the shutoff valve 15 (step S505) are continued. When it is determined that the coolant temperature is stable, the opening degree control of the EGR valve 20 is resumed (step S508, indicated by h in FIG. 7).

According to the present embodiment, the engine control unit 3 opens the shut-off valve 15 when the coolant temperatures thw1, thw2 detected by the first temperature sensor D1 or the second temperature sensor D2 are equal to or higher than the temperature threshold T1. When the coolant temperatures thw1 and thw2 detected by the first temperature sensor D1 or the second temperature sensor D2 reach a temperature threshold T2 lower than the temperature threshold T1 by a predetermined temperature, the opening control of the EGR valve 20 is stopped. By closing the EGR valve 20 and fixing it, the opening control of the EGR valve 20 is stopped before the shutoff valve 15 is opened, and the intake air is supplied from the EGR cooler 19 to the combustion chamber 111. The intake air temperature introduced into the combustion chamber 111 can be reliably prevented from changing.

  Further, when the coolant temperatures thw1 and thw2 detected by the first temperature sensor D1 or the second temperature sensor D2 reach the temperature threshold value T1 while the EGR valve 20 is displaced toward the fully closed state, at that time When the coolant temperature in the engine body 11 rises during the displacement of the EGR valve 20 by fixing the opening of the EGR valve 20 and opening the shut-off valve 15 in FIG. On the other hand, since coolant circulation in the engine body 11 is preferentially executed, boiling of the coolant in the engine body 11 can be prevented.

  Further, when the coolant temperatures thw1 and thw2 detected by the first temperature sensor D1 or the second temperature sensor D2 reach the temperature threshold value T1 while the EGR valve 20 is displaced toward the fully closed state, at that time By fixing the opening degree of the EGR valve 20 at the time, the intake air amount supplied from the EGR cooler 19 to the combustion chamber 111 does not fluctuate, the influence of the opening degree control of the EGR valve 20 on the intake air temperature is completely eliminated, and the combustion is performed. Variations in the intake air temperature introduced into the chamber 111 can be minimized.

  Further, after the shutoff valve 15 is opened, when the coolant temperatures thw1 and thw2 detected by the first temperature sensor D1 and the second temperature sensor D2 are stabilized, the opening degree control of the EGR valve 20 is resumed. Thus, the opening degree control of the EGR valve 20 can be smoothly restarted without changing the temperature of the intake air introduced into the combustion chamber 111.

<Embodiment 3>
Next, a cooling system of the engine 1A according to the third embodiment will be described based on FIG. In FIG. 8, the same components as those in the first embodiment are denoted by the same reference numerals as those in FIG. As shown in FIG. 8, the cooling system of the engine 1A according to the present embodiment includes the heater core 12, the exhaust heat recovery device 13, and the second temperature sensor D2 as compared with the cooling system according to the first embodiment. Absent.

  In the cooling system according to the present embodiment, when it is determined that the coolant temperature thw1 detected by the first temperature sensor D1 is lower than the temperature threshold T1, the shutoff valve 15 is closed and the coolant temperature is set to the temperature threshold T1. When it determines with it being above, the cutoff valve 15 is displaced from a closed state to an open state.

  When it is determined that the coolant temperature thw1 detected by the first temperature sensor D1 is equal to or higher than the temperature threshold value T2, the opening control of the EGR valve 20 is stopped and the closing operation of the EGR valve 20 is started. Since the other points of the cooling system according to the present embodiment are the same as those of the cooling system according to the first embodiment, description thereof will be omitted.

<Other embodiments>
The present invention is not limited to the above-described embodiments, and can be modified or expanded as follows.
The means for circulating the coolant through the first cooling water passage L1 and the second cooling water passage L2 is not limited to the electric pump 14, and a water pump driven by the engine 1 may be used.
Further, a water pump for circulating the coolant may be provided in each of the first cooling water passage L1 and the second cooling water passage L2.
Further, the control means for controlling the opening / closing operation of the shutoff valve 15 and the control means for executing the opening degree control of the EGR valve 20 may be provided separately.

  In the above-described embodiment, the shutoff valve 15 is opened when at least one of the detection values thw1 and thw2 detected by the first temperature sensor D1 and the second temperature sensor D2 is equal to or higher than the temperature threshold T1. However, when one of the detection values thw1 and thw2 detected by the first temperature sensor D1 and the second temperature sensor D2 is less than the temperature threshold T1, the shutoff valve 15 is closed, and the first temperature sensor D1 and the first temperature sensor D1 The shutoff valve 15 may be opened when both the detection values thw1 and thw2 detected by the two temperature sensor D2 are equal to or higher than the temperature threshold T1.

  In the second embodiment described above, the EGR valve 20 is closed when at least one of the detection values thw1 and thw2 detected by the first temperature sensor D1 and the second temperature sensor D2 is equal to or higher than the temperature threshold T2. However, when one of the detection values thw1 and thw2 detected by the first temperature sensor D1 and the second temperature sensor D2 is less than the temperature threshold value T2, the EGR valve 20 is brought into the opening control state, and the first temperature The EGR valve 20 may be closed when both the detected values thw1 and thw2 detected by the sensor D1 and the second temperature sensor D2 are equal to or higher than the temperature threshold T2.

Further, when the detection values thw1 and thw2 detected by the first temperature sensor D1 or the second temperature sensor D2 are higher than the temperature threshold value T1 (not including the case where the temperature threshold values T1 and T2 are equal), the shutoff valve 15 is opened. Also good.
Further, even when the EGR valve 20 is closed when the detection values thw1 and thw2 detected by the first temperature sensor D1 or the second temperature sensor D2 are higher than the temperature threshold T2 (not including the case where the temperature is equal to the temperature thresholds T1 and T2). Good.

  Further, a cooling system in which the first temperature sensor D1 is not provided in the first cooling water passage L1 and the second temperature sensor D2 is provided in the second cooling water passage L2 may be used. In this case, when the coolant temperature thw2 detected by the second temperature sensor D2 is less than the temperature threshold T1, the shutoff valve 15 is closed, and when it is determined that the coolant temperature thw2 is equal to or higher than the temperature threshold T1, The valve 15 is displaced from the closed state to the open state. When it is determined that the coolant temperature thw2 detected by the second temperature sensor D2 is equal to or higher than the temperature threshold T2, the opening control of the EGR valve 20 is stopped and the closing operation of the EGR valve 20 is started.

  In the drawings, 1, 1A is an engine, 3 is an engine control unit (open / close valve control means, EGR control means), 12 is a heater core, 13 is an exhaust heat recovery device, 14 is an electric pump (cooling water pressure feeding means, water pump), 15 is a shut-off valve (open / close valve), 18 is an EGR passage, 19 is an EGR cooler, 20 is an EGR valve (flow rate adjusting means), 111 is a combustion chamber, and D1 is a first temperature sensor (water temperature detecting means and first water temperature sensor). , D2 is a second temperature sensor (water temperature detecting means, second water temperature sensor), L1 is a first cooling water passage (first cooling water passage), L2 is a second cooling water passage (second cooling water passage), and P1 is The connection part (merging point) is shown.

Claims (7)

A first coolant path through which coolant circulates including the water jacket of the engine;
A second cooling water path formed so that cooling water circulates including an EGR cooler that cools the exhaust from the engine and merges with the first cooling water path on the downstream side of the EGR cooler;
Cooling water pumping means capable of circulating cooling water in the first cooling water path and the second cooling water path;
A flow rate adjusting means which is provided on a passage connecting the EGR cooler and the combustion chamber of the engine and adjusts an amount of gas supplied from the EGR cooler to the combustion chamber by increasing or decreasing an opening;
EGR control means for controlling the opening degree of the flow rate adjusting means based on the state of the vehicle;
An on-off valve provided on the first cooling water path and intermittently connecting between the water jacket and a junction to the second cooling water path;
Water temperature detecting means for detecting a cooling water temperature of at least one of the first cooling water path or the second cooling water path;
On-off valve control means for controlling the operation of the on-off valve based on the cooling water temperature detected by the water temperature detection means;
In the engine cooling system with
The EGR control means includes
When the on-off valve is displaced from the closed state to the open state, the opening control of the flow rate adjusting means is stopped. The EGR control means includes
When the on-off valve is displaced from the closed state to the open state, the opening of the flow rate adjusting means is fixed at that time,
2. The engine according to claim 1, wherein when the cooling water temperature detected by the water temperature detecting means is stabilized after the on-off valve is opened, the opening degree control of the flow rate adjusting means is resumed. Cooling system. The on-off valve control means includes
When the cooling water temperature detected by the water temperature detection means is less than a first threshold value or less than the first threshold value, the on-off valve is closed, and the cooling water temperature detected by the water temperature detection means is the first temperature. When the threshold value is greater than or equal to the first threshold value, the on-off valve is opened,
The EGR control means includes
When the coolant temperature detected by the water temperature detecting means reaches a second threshold value that is lower than the first threshold value by a predetermined temperature, the opening control of the flow rate adjusting means is stopped and the flow rate adjusting means is fully closed. 2. The engine cooling system according to claim 1, wherein the engine cooling system is fixed in a state. The EGR control means includes
When the cooling water temperature detected by the water temperature detecting means reaches the first threshold value while the flow rate adjusting means is being displaced toward the fully closed state, the opening degree of the flow rate adjusting means is increased at that time. Fixed,
The engine according to claim 3, wherein when the cooling water temperature detected by the water temperature detecting means is stabilized after the on-off valve is opened, the opening degree control of the flow rate adjusting means is resumed. Cooling system. The second cooling water path is
A heater core provided on the downstream side of the junction with the first cooling water path;
An exhaust heat recovery device provided upstream of the heater core;
Have
The water temperature detecting means is
A first water temperature sensor provided between the water jacket and the on-off valve in the water jacket or on the first cooling water path;
A second water temperature sensor provided between a confluence of the first cooling water path on the second cooling water path and the heater core;
Have
The on-off valve is
When the cooling water temperature detected by the first water temperature sensor and the cooling water temperature detected by the second water temperature sensor are both less than the first threshold value or less than the first threshold value, the valve is closed.
The valve is opened when at least one of the cooling water temperature detected by the first water temperature sensor and the cooling water temperature detected by the second water temperature sensor is equal to or higher than the first threshold or higher than the first threshold. 5. The engine cooling system according to claim 3, wherein the engine cooling system. The cooling water pumping means is
A water pump formed on the downstream side of the heater core on the second cooling water path;
Between the junction point on the second cooling water path and the upstream side of the water pump, it is shared as a part of the first cooling water path,
The water pump is
6. The engine cooling system according to claim 5, wherein the sucked cooling water is discharged toward both the water jacket and the exhaust heat recovery unit. The cooling system is
A first coolant path through which coolant circulates including the water jacket of the engine;
A second cooling water path formed so that cooling water circulates including an EGR cooler that cools the exhaust from the engine and merges with the first cooling water path on the downstream side of the EGR cooler;
Cooling water pumping means capable of circulating cooling water in the first cooling water path and the second cooling water path;
A flow rate adjusting means which is provided on a passage connecting the EGR cooler and the combustion chamber of the engine and adjusts an amount of gas supplied from the EGR cooler to the combustion chamber by increasing or decreasing an opening;
An on-off valve provided on the first cooling water path and intermittently connecting between the water jacket and a junction to the second cooling water path;
Water temperature detecting means for detecting a cooling water temperature of at least one of the first cooling water path or the second cooling water path;
With
In a method for controlling an engine cooling system, the operation of the on-off valve is controlled based on the coolant temperature detected by the water temperature detecting means, and the opening degree of the flow rate adjusting means is controlled based on the state of the vehicle. ,
A control method for an engine cooling system, wherein when the on-off valve is displaced from a closed state to an open state, the opening control of the flow rate adjusting means is stopped.

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