JP7259054B2 - engine cooling system - Google Patents

Description

The present invention relates to an engine cooling device.

Conventional cooling devices of this type have a thermostat in the cooling water passage that connects the engine and the radiator. It is set to a characteristic that gradually opens and closes between The circulation state of cooling water between the engine and the radiator is adjusted according to the opening and closing of the thermostat, and the engine is kept within a predetermined temperature range.

On the other hand, in view of the fact that more precise water temperature control is required in order to meet the recent demands for exhaust gas regulations and fuel efficiency improvement, for example, electronically controlled engine cooling as described in Patent Document 1 The device has been put into practical use. In this cooling device, the flow rate of cooling water flowing between the engine and the radiator can be adjusted by a channel switching valve. Based on the deviation, the engine coolant temperature is maintained at the target temperature by controlling the opening of the flow path switching valve. In such an electronically controlled cooling device, the opening and closing speed of the flow path switching valve can be arbitrarily set with respect to the water temperature deviation. A characteristic may be imparted that causes the valve to open and close relatively slowly.

JP 2014-169661 A

However, in the cooling device of Patent Document 1, the temperature of cooling water flowing through the engine greatly deviates from the target water temperature under the following circumstances.
As described above, the degree of opening of the flow path switching valve is controlled based on the water temperature deviation. The switching valve is closed. At this time, the cooling water circulates through the water jacket of the engine without being cooled by the radiator, and as indicated by A in FIG. 4, the water temperature T gradually rises due to the heat received from the engine. Also, at this time, the cooling water stays in the radiator and is cooled by the running wind, and the temperature gradually drops.

When the cooling water temperature rises and the water temperature T>target water temperature tgtT as indicated by B in FIG. 4, the flow path switching valve is controlled to open side. In the case of the characteristic that the flow path switching valve is gently opened and closed with respect to the water temperature deviation, the opening side control at this time is also performed gently as indicated by C in FIG. However, since the low-temperature cooling water cooled in the radiator flows into the water jacket, the water temperature T changes from rising to falling and rapidly drops as indicated by D in FIG. The flow path switching valve is closed again in response to the reduction in the water temperature deviation accompanying this temperature drop. can not be suppressed, and the water temperature T greatly deviates from the target water temperature tgtT to the low temperature side as indicated by the dashed line Fa in FIG.
Such an inappropriate cooling water temperature drop occurs every time the flow path switching valve is switched, causing problems such as an increase in the oil viscosity of the engine and poor vaporization of the fuel, resulting in deterioration of fuel efficiency and exhaust gas characteristics.

The present invention has been made to solve such problems, and its object is to prevent a sudden drop in cooling water temperature when the flow path switching valve is controlled from the closed side to the open side. To provide an engine cooling device capable of keeping an engine in a good temperature range.

In order to achieve the above object, the engine cooling device of the present invention comprises a flow rate adjusting section for adjusting the flow rate of cooling water circulating between the engine and the radiator, and a water temperature detecting section for detecting the temperature of the cooling water flowing through the engine. A detection unit, a target water temperature calculation unit that calculates the target water temperature of the cooling water based on the operating state of the engine, and a water temperature deviation based on the water temperature detected by the water temperature detection unit and the target water temperature calculated by the target water temperature calculation unit. , a first storage unit that stores the relationship between the preset water temperature deviation and the target opening of the flow rate adjustment unit for achieving the target water temperature, and stored in the first storage unit Based on the relationship, the target opening calculation unit calculates the target opening from the water temperature deviation calculated by the deviation calculation unit, and the flow rate adjustment unit based on the change state of the target opening calculated by the target opening calculation unit The control speed of the flow rate adjusting unit is calculated based on the water temperature deviation calculated by the opening/closing direction determination unit that determines the opening/closing direction and the deviation calculation unit. A control speed calculator that calculates a higher control speed than when the determined opening/closing direction is the open side, a target opening calculated by the target opening calculator, and a control speed calculated by the control speed calculator. A valve control unit that controls the opening of the flow rate adjustment unit, and a water temperature deviation correction unit that calculates the corrected water temperature deviation based on at least the proportional term and the integral term of the basic water temperature deviation, with the water temperature deviation as the basic water temperature deviation. The first storage unit stores the relationship between the corrected water temperature deviation and the target opening, the target opening calculation unit calculates the target opening based on the corrected water temperature deviation, and the opening/closing direction determination unit The opening/closing direction is determined based on the target opening calculated based on the corrected water temperature deviation, the control speed calculation unit calculates the control speed based on the basic water temperature deviation, and the valve control unit calculates based on the corrected water temperature deviation. It is characterized by controlling the opening of the flow rate adjusting unit based on the target opening .

As another aspect, a second storage unit that stores a relationship between a preset water temperature deviation and a control speed on the open side of the flow rate adjustment unit, and an unrestricted value that is a control speed that is equal to or higher than the response speed of the flow rate adjustment unit. Further, when the opening/closing direction determined by the opening/closing direction determination unit is the open side, the control speed calculation unit calculates the control speed from the water temperature deviation based on the relationship stored in the second storage unit. When the opening/closing direction is the closing side, the non-limiting value stored in the second storage section may be used as the control speed regardless of the water temperature deviation.

According to the engine cooling device of the present invention, it is possible to avoid a sudden drop in the cooling water temperature when the flow path switching valve is controlled from the closed side to the open side, and to keep the engine in a good temperature range.

1 is an overall configuration diagram showing an engine cooling device according to an embodiment; FIG. 3 is a control block diagram showing the configuration of an ECU; FIG. 4 is a flow chart showing a water temperature control routine executed by an ECU; 4 is a time chart comparing cooling water temperature control states between the embodiment and the technology of Patent Document 1;

An embodiment of an engine cooling device embodying the present invention will be described below.
The engine 1 of this embodiment is mounted on a passenger car as a driving power source, and is cooled by a water-cooled cooling device 2 . As shown in FIG. 1, cooling water discharged from a water pump 4 flows through a water jacket 3 formed in the engine 1. After that, an outflow passage 5 is connected to one side of the engine 1 from the water jacket 3. It is designed to flow inside. One ends of the main water channel 6 , the sub water channel 7 and the bypass water channel 8 are connected to the outflow channel 5 , and the other end of the bypass water channel 8 is connected to the suction side of the water pump 4 .

A radiator 9 is interposed in the main water channel 6 , and the other end of the main water channel 6 is connected to the suction side of the water pump 4 . The sub-waterway 7 is bifurcated and is provided with an EGR valve 10 for recirculating the exhaust gas to the intake side and a throttle device 11 for adjusting the amount of intake air. is also connected to a location on the water pump 4 side.

Therefore, the cooling water guided from the outflow passage 5 to the main water passage 6 is cooled by the running wind while flowing through the radiator 9, and is returned to the water pump 4 after being lowered in temperature. The cooling water guided from the outflow passage 5 to the sub-water passage 7 flows through the EGR valve 10 and the throttle device 11 , cools these devices 9 and 10 , increases the temperature, and is returned to the water pump 4 . Also, the cooling water guided from the outflow channel 5 to the bypass water channel 8 is returned to the water pump 4 at the same temperature.

A channel switching valve 12 is disposed in the outflow channel 5, and the channel of the cooling water is continuously adjusted by the channel switching valve 12. As shown in FIG. Specifically, the inlet port of the flow path switching valve 12 communicates with the inside of the outflow path 5, and the outlet port of the flow path switching valve 12 communicates with the main water path 6 and the sub water path 7, respectively. The flow path switching valve 12 is configured as a rotary type in which a rotor incorporated therein is rotated by driving a motor 13 . The opening ratios of the main water channel 6 side and the sub water channel 7 side are continuously adjusted according to the rotor angle θ, thereby changing the flow rate of the cooling water guided from the outflow channel 5 to the main water channel 6 and the sub water channel 7. .

In the following description, the adjustment state of the opening ratio by the flow path switching valve 12 will be expressed mainly based on the opening area on the main water passage 6 side, in other words, the opening degree A of the radiator 9 . For example, a state in which the main water passage 6 side is fully closed is expressed as a radiator opening degree A=0%, and the flow of cooling water to the radiator 9 is stopped at this time. A state in which the main water passage 6 side is fully opened is expressed as radiator opening A=100%, and the flow rate of cooling water flowing through the radiator 9 is maximized at this time.

When the cooling water flow path is continuously adjusted in this way, the flow rate of the cooling water flowing between the engine 1 and the radiator 9 is adjusted as a result. functions as the flow rate adjusting section of the present invention.

The operating state of the cooling device 2 is controlled by an ECU 15 (electronic control unit). The ECU 15 includes an input/output interface 15a, a storage device 15b (ROM, RAM, etc.) containing many control programs, a central processing unit 15c (CPU), and a timer counter 15d. On the input side of the ECU 15, a position sensor 16 for detecting the rotor angle of the flow path switching valve 12, a first water temperature sensor 17 for detecting the temperature of cooling water flowing out from the engine 1 into the outflow path 5 as the engine temperature T, and Various sensors such as a second water temperature sensor 18 for detecting the temperature of the cooling water after passing through the radiator 9 are connected.

Various devices such as a motor 13 for driving the flow path switching valve 12 are connected to the output side of the ECU 15 . In this embodiment, the engine temperature T corresponds to the temperature of cooling water flowing through the engine 1 of the present invention, and the first water temperature sensor 17 that detects this engine temperature T functions as the water temperature detector of the present invention.

Next, the configuration of the ECU 15 will be described based on the control block diagram of FIG.
A target water temperature calculation unit 21 of the ECU 15 calculates a target water temperature tgtT of the cooling water based on the operating state of the engine 1 and inputs it to the deviation calculation unit 22 together with the engine temperature T detected by the first water temperature sensor 17 .

The deviation calculation unit 22 calculates a basic water temperature deviation ΔTbase as the difference between the target water temperature tgtT and the engine temperature T, and inputs it to the PI control unit 23 . Based on the basic water temperature deviation ΔTbase, the P-term setting unit 23a of the PI control unit 23 sets a proportional term, and the I-term setting unit 23b sets an integral term. The corrected water temperature deviation ΔT based on is calculated.

In this embodiment, the PI control section 23 functions as the water temperature deviation correction section of the present invention. The PI control may be replaced with PD control or PID control, or the PI control unit 23 may be omitted and the basic water temperature deviation ΔTbase may be treated as the corrected water temperature deviation ΔT.

The post-correction water temperature deviation ΔT is input to the target opening calculator 24, and the target radiator opening tgtA is calculated based on the post-correction water temperature deviation ΔT. For this calculation process, the storage device 15b of the ECU 15 stores in advance a control map that defines the relationship between the corrected water temperature deviation ΔT and the target radiator opening tgtA. Table 1 below shows an example of the control map, and is set to characteristics that increase the target radiator opening degree tgtA as the post-correction water temperature deviation ΔT increases as a whole. For example, when the post-correction water temperature deviation ΔT=0° C., the target radiator opening tgtA=0% is calculated, and when the post-correction water temperature deviation ΔT=10° C., the target radiator opening tgtA=100% is calculated.

In this embodiment, the storage device 15b that stores the control map of Table 1 functions as the first storage section of the present invention.

The target radiator opening degree tgtA is input to the opening/closing direction determination unit 25, and the opening/closing direction determination unit 25 determines the change direction of the target radiator opening degree tgtA based on the deviation of the target radiator opening degree tgtA calculated in the current and previous control cycles. In other words, the opening/closing direction of the flow path switching valve 12 is determined. In the present embodiment, the deviation between the current value and the previous value of the target radiator opening tgtA corresponds to the state of change of the target opening of the present invention.

On the other hand, the determination result of the opening/closing direction determining section 25 is input to the switching section 26 a of the control speed calculating section 26 together with the basic water temperature deviation ΔTbase calculated by the deviation calculating section 22 . The switching unit 26a is switched to the opening side speed calculation unit 26b when the determination result of the opening/closing direction determination unit 25 is on the open side, and is switched to the closing side speed calculation unit 26c when the determination result is on the close side. The basic water temperature deviation ΔTbase is input to the speed calculation units 26b and 26c on the switched side, and the control speed θspd of the flow path switching valve 12 is calculated based on the basic water temperature deviation ΔTbase.

For this calculation process, the storage device 15b of the ECU 15 stores in advance a control map defining the relationship between the basic water temperature deviation ΔTbase and the control speed θspd corresponding to each of the speed calculators 26b and 26c. Table 2 below shows an example of a control map applied to the opening side speed calculation section 26b, and Table 3 below shows an example of a control map applied to the closing side speed calculation section 26c.

In this embodiment, the storage device 15b that stores Table 2 and the control map of Table 2 functions as the second storage unit of the present invention.

As shown in Table 2, when the flow path switching valve 12 is controlled to open, the greater the basic water temperature deviation ΔTbase, the higher the control speed θspd calculated. This map characteristic is based on the knowledge that the more the engine temperature T deviates from the target water temperature tgtT, the more rapid the rotor angle control of the flow path switching valve 12 is required. However, the control speed θspd to the opening side set in Table 2 is relatively low, and the flow path switching valve 12 has a response speed that can sufficiently follow the maximum control speed θspd=8 (%/sec). It is manufactured as a specification with

While the target radiator opening degree tgtA obtained from the post-correction water temperature deviation ΔT is applied to the determination processing of the opening/closing direction of the flow path switching valve 12 and the control of the radiator opening degree A, which will be described later, the control speed θspd is calculated. The application of the basic water temperature deviation ΔTbase to the treatment is based on the following findings. As will be described later, the actual radiator opening A and thus the rotor angle θ of the passage switching valve 12 are feedback-controlled based on the target radiator opening tgtA. Therefore, by applying the target radiator opening degree tgtA based on the corrected water temperature deviation ΔT that reflects the PI control, it is possible to accurately control the radiator opening degree A, and the flow controlled based on the rotor angle θ. It is also possible to accurately determine the opening/closing direction of the path switching valve 12 .

On the other hand, the control speed .theta.spd must be controlled according to the state of deviation of the engine temperature T from the target water temperature tgtT at that time, as described above. Therefore, it is preferable to set based on the basic water temperature deviation ΔTbase, which is the deviation between the actual target water temperature tgtT and the engine temperature T, rather than the post-correction water temperature deviation ΔT including the delay element due to the I control. The flow path switching valve 12 can be driven at the speed θspd.

On the other hand, as shown in Table 3, when the flow path switching valve 12 is controlled to the closed side, the control speed θspd=200 (%/sec), which is much higher than the control speed θspd in the case of the open side control, is basic. It is uniformly calculated regardless of the magnitude of the water temperature deviation ΔTbase. This control speed θspd is a value equal to or higher than the response speed of the flow path switching valve 12, which corresponds to the non-limiting value of the present invention, and the flow path switching valve 12 is inevitably driven at the maximum speed. As described above, the reason why the flow path switching valve 12 is driven based on the relatively higher control speed θspd on the closing side compared to the opening side is to solve the problem of the technique of Patent Document 1. This point will be detailed later based on a time chart.

The control speed θspd calculated by the open side or closed side speed calculators 26b and 26c of the control speed calculator 26 is input to the valve controller 27 together with the target radiator opening tgtA calculated by the target opening calculator 24. . Although not shown, the storage device 15b of the ECU 15 stores a control map that defines the relationship between the radiator opening A and the rotor angle θ of the flow path switching valve 12. By referring to this map, valve control is performed. A unit 27 calculates a target rotor angle tgtθ from the target radiator opening tgtA. Based on the deviation between the target rotor angle tgtθ and the actual rotor angle θ detected by the position sensor 16, feedback control is executed while maintaining the opening/closing speed of the flow path switching valve 12 at the control speed θspd.

Next, the control contents of the above ECU 15 will be explained based on the flow chart of FIG.
First, in step 1, detection information is read from each sensor, in subsequent step 2, a basic water temperature deviation ΔTbase is calculated, and in step 3, a corrected water temperature deviation ΔT is calculated. The process of step 2 is executed by the deviation calculator 22 and the process of step 3 is executed by the PI controller 23 . After that, in step 4, the target radiator opening tgtA is calculated based on the control map of Table 1, and in step 5, the change direction of the target radiator opening tgtA is determined. The process of step 4 is executed by the target opening calculation section 24 , and the process of step 5 is executed by the opening/closing direction determination section 25 .

When the change direction determined in step 5 is the open side, the process proceeds from step 6 to step 7, and based on the control map of Table 2, the open side control speed θspd is calculated. Further, when the change direction is the closing side, the process proceeds from step 6 to step 8, and the closing side control speed θspd is calculated based on the control map of Table 3. After that, in step 9, the flow path switching valve 12 is feedback-controlled based on the target radiator opening degree tgtA and the control speed θspd. The processing of step 6 is executed by the switching section 26a of the control speed calculation section 26, the processing of step 7 is executed by the opening side speed calculation section 26b, the processing of step 8 is executed by the closing side speed calculation section 26c, and the processing of step 10 is executed by the closing side speed calculation section 26c. is executed by the valve control unit 27 .

Next, the cooling water temperature control status based on the processing of the ECU 15 will be described with reference to the time chart of FIG.
In order to facilitate understanding, the figure shows a case where the target water temperature tgtT is kept constant. % is calculated, and the main water channel 6 side is fully closed by the channel switching valve 12 . Therefore, the coolant circulates through the water jacket 3 of the engine 1 through the bypass water passage 8 or the sub-water passage 7 without being cooled by the radiator 9, and as shown by A in FIG. T gradually rises. Also, at this time, the cooling water stays in the radiator 9 and is cooled by the running wind, and the temperature gradually drops.

When engine temperature T>target water temperature tgtT as indicated by B in FIG. The control speed .theta.spd of the flow path switching valve 12 at this time is set based on Table 2, and the flow path switching valve 12 is controlled to the opening side relatively slowly as indicated by C in FIG. However, since the low-temperature cooling water cooled in the radiator 9 flows into the water jacket 3, the engine temperature T changes from an increase to a decrease and rapidly decreases as indicated by D in FIG.

The passage switching valve 12 is closed-side controlled based on the target radiator opening degree tgtA calculated from Table 1 in response to the reduction of the corrected water temperature deviation ΔT accompanying this temperature drop. The control speed θspd of the flow path switching valve 12 at this time is set based on Table 3, and the flow path switching valve 12 is quickly controlled to the closing side as indicated by the solid line Eb in FIG. Therefore, the decrease in the engine temperature T is quickly suppressed, and as indicated by the solid line Fb in FIG. 4, the engine temperature T starts to rise without deviating from the target water temperature tgtT to the low temperature side. A decrease in the engine temperature T that greatly deviates from the target water temperature tgtT causes an increase in oil viscosity and poor vaporization of fuel. , its fuel economy and emission characteristics can be improved.

The significance of the cooling control of the engine 1 of this embodiment can also be understood as follows. When electronically controlled cooling devices were first put into practical use, they were often provided with the characteristics of opening and closing the flow path switching valves relatively slowly, simulating the characteristics of a thermostat. At that time, it was important to prevent overheating of the engine, so from this point of view, in order to suppress a sudden increase in the engine temperature T, the control speed was increased when the flow path switching valve was opened rather than when it was closed. was considered to be a priority. However, with any control characteristic, it is not possible to avoid the sudden drop in cooling water temperature as described with reference to FIG.

Such a problem is caused by the phenomenon that the low-temperature cooling water in the radiator 9 flows into the water jacket 3 due to the opening control of the flow path switching valve 12 described above. The inherent characteristic of the engine 1 is that the cooling of the radiator 9 causes the water temperature to drop more rapidly than the water temperature rise. On the other hand, in order to satisfy recent demands for fuel economy and exhaust gas characteristics, it is more important to prevent overcooling of the engine 1 than to prevent overheating of the engine 1, which causes an increase in oil viscosity and poor vaporization of fuel. .

As described above, it can be seen that there is a demand for cooling control that prioritizes prevention of overcooling of the engine 1 from the standpoint of both the inherent characteristics of the engine 1 and the requirements related to fuel efficiency and exhaust gas characteristics. Such a request can be achieved by cooling control in which the control speed θspd when the flow path switching valve 12 is closed is increased compared to when the flow path switching valve 12 is open, as in the present embodiment, and as a result, the above-described effects can be achieved. of.

On the other hand, the target opening degree calculation unit 24 calculates the target radiator opening degree tgtA from the corrected water temperature deviation ΔT based on the control map of Table 1 stored in the storage device 15b. Therefore, not only the PI control based on the corrected water temperature deviation ΔT but also the feedback control of the rotor angle θ of the flow path switching valve 12 reflecting the characteristics of the control map is performed. For example, the control map in Table 1 has the characteristic that the target radiator opening degree tgtA sharply increases with an increase in the post-correction water temperature deviation ΔT, so an increase in the engine temperature T can be reliably suppressed. Since the contents of the feedback control can be arbitrarily changed based on the setting of the map characteristics in this way, the engine 1 can be kept in a better temperature range.

Although the description of the embodiment is finished above, the aspect of the present invention is not limited to this embodiment. For example, in the above embodiment, the cooling device 2 is used for the engine 1 mounted on a passenger car, but the present invention is not limited to this. For example, it may be embodied in a cooling device for an engine mounted on a motorcycle or an ATV (All Terrain Vehicle). Moreover, the configuration of the water passages of the cooling device 2 shown in FIG. 1 is not limited to this, and can be arbitrarily changed.

1 engine 9 radiator 12 flow path switching valve (flow control unit)
15b storage device (first storage unit, second storage unit)
17 first water temperature sensor (water temperature detector)
21 target water temperature calculator 22 deviation calculator 23 PI controller (water temperature deviation corrector)
24 target opening calculation unit 25 opening/closing direction determination unit 26 control speed calculation unit 27 valve control unit

Claims (2)

a flow rate adjustment unit that adjusts the flow rate of cooling water circulating between the engine and the radiator;
a water temperature detection unit that detects the temperature of cooling water flowing through the engine;
a target water temperature calculation unit that calculates a target water temperature of cooling water based on the operating state of the engine;
a deviation calculator for calculating a water temperature deviation based on the water temperature detected by the water temperature detector and the target water temperature calculated by the target water temperature calculator;
a first storage unit that stores a relationship between a preset water temperature deviation and a target opening degree of the flow rate adjustment unit for achieving the target water temperature;
a target opening calculation unit that calculates the target opening from the water temperature deviation calculated by the deviation calculation unit based on the relationship stored in the first storage unit;
an opening/closing direction determination unit that determines the opening/closing direction of the flow rate adjustment unit based on the change state of the target opening calculated by the target opening calculation unit;
The control speed of the flow rate adjusting unit is calculated based on the water temperature deviation calculated by the deviation calculating unit, and when the opening/closing direction determined by the opening/closing direction determination unit is the closed side, the determined opening/closing direction is the open side. a control speed calculator that calculates a higher control speed than in the case of
a valve control unit that controls the opening of the flow rate adjusting unit based on the target opening calculated by the target opening calculating unit and the control speed calculated by the control speed calculating unit ;
a water temperature deviation correction unit for calculating a corrected water temperature deviation based on at least a proportional term and an integral term of the basic water temperature deviation, with the water temperature deviation as a basic water temperature deviation;
with
The first storage unit stores a relationship between the corrected water temperature deviation and the target opening,
The target opening degree calculation unit calculates the target opening degree based on the corrected water temperature deviation,
The opening/closing direction determination unit determines the opening/closing direction based on the target opening calculated based on the corrected water temperature deviation,
The control speed calculation unit calculates the control speed based on the basic water temperature deviation,
The valve control unit controls the opening of the flow rate adjusting unit based on the target opening calculated based on the corrected water temperature deviation.
An engine cooling device characterized by: A second storage unit that stores a relationship between a preset water temperature deviation and a control speed on the open side of the flow rate adjusting unit, and an unrestricted value that is a control speed equal to or higher than the response speed of the flow rate adjusting unit,
The control speed calculation unit calculates the control speed from the water temperature deviation based on the relationship stored in the second storage unit when the opening/closing direction determined by the opening/closing direction determination unit is the open side, 2. The engine according to claim 1, wherein, when the determined opening/closing direction is the closing side, the non-limiting value stored in the second storage unit is set as the control speed regardless of the water temperature deviation. Cooling system.

Images