CN114270022B

CN114270022B - Cooling device for engine

Info

Publication number: CN114270022B
Application number: CN201980099679.5A
Authority: CN
Inventors: 菅原秀行
Original assignee: Mikuni Corp
Current assignee: Mikuni Corp
Priority date: 2019-08-29
Filing date: 2019-08-29
Publication date: 2023-11-21
Anticipated expiration: 2039-08-29
Also published as: CN114270022A; WO2021038776A1; JPWO2021038776A1; DE112019007670T5; JP7259054B2

Abstract

Comprising the following steps: a flow rate adjustment unit (12) that adjusts the flow rate of cooling water circulating between the engine (1) and the radiator (9); a water temperature detection unit (17) that detects the temperature of cooling water flowing through the engine; a target water temperature calculation unit (21) that calculates a target water temperature of the cooling water; a deviation calculation unit (22) that calculates a water temperature deviation based on the water temperature and the target water temperature; a target opening calculating unit (24) for calculating a target opening of the flow rate adjusting unit (12) for achieving the target water temperature based on the water temperature deviation; an opening/closing direction determination unit (25) that determines the opening/closing direction of the flow rate adjustment unit (12) on the basis of the state of change in the target opening; a control speed calculation unit (26) that calculates the control speed of the flow rate adjustment unit (12) on the basis of the water temperature deviation, and that calculates a higher control speed when the flow rate adjustment unit (12) is on the closed side than when it is on the open side; a valve control unit (27) controls the opening of the flow rate adjustment unit (12) based on the target opening and the control speed.

Description

Cooling device for engine

Technical Field

The present invention relates to a cooling device for an engine.

Background

In such a conventional cooling device, a thermostat is provided in a cooling water passage connecting an engine and a radiator, and the thermostat is set to have the following characteristics: the wax is gradually opened and closed between the full open state and the full closed state by thermal expansion, for example, in a temperature range of about 80 to 90 ℃. The state of flow of cooling water between the engine and the radiator is adjusted according to the opening and closing of the thermostat, so that the engine is maintained in a predetermined temperature range.

On the other hand, in view of the demand for more careful water temperature control in order to cope with the recent demands for exhaust gas restriction, fuel efficiency improvement, and the like, for example, the cooling device of an electronically controlled engine described in patent document 1 has been put into practical use. The cooling device is capable of adjusting the flow rate of cooling water flowing between the engine and the radiator by the flow path switching valve, and controlling the opening degree of the flow path switching valve so as to maintain the cooling water of the engine at a target water temperature, for example, in accordance with a deviation between the target water temperature set based on the operation state of the engine and the water temperature detected by the water temperature sensor. In the electronically controlled cooling device, since the opening/closing speed of the flow path switching valve with respect to the water temperature deviation can be arbitrarily set, for example, characteristics of a conventional thermostat may be simulated, and characteristics of slowly opening/closing the flow path switching valve with respect to the water temperature deviation may be provided.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2014-169661

Disclosure of Invention

Technical problem to be solved by the invention

However, in the cooling device of patent document 1, the cooling water temperature flowing through the engine in the following condition is greatly deviated from the target water temperature.

As described above, the opening degree of the flow path switching valve is controlled in accordance with the water temperature deviation, and for example, when the water temperature is greater than the target water temperature, the temperature is reduced by controlling the opening side of the flow path switching valve, and when the water temperature is less than or equal to the target water temperature, the flow path switching valve is closed. At this time, the cooling water circulates in the water jacket of the engine without being cooled by the radiator, and as shown in fig. 4 a, the water temperature T gradually rises due to the heat received from the engine. At this time, the cooling water is retained in the radiator, and the temperature is gradually lowered by cooling with the running wind.

When the water temperature T > the target water temperature tgtT as shown in fig. 4B is changed due to the temperature rise of the cooling water, the flow path switching valve is controlled to open. In the case of the characteristic that the flow path switching valve is opened and closed slowly with respect to the water temperature deviation, the opening control at this time is also performed slowly as shown in fig. 4C. However, since the low-temperature cooling water cooled in the radiator flows into the water jacket, the water temperature T is changed from rising to falling as shown by D in fig. 4, and is abruptly reduced. The flow path switching valve is closed again in response to the reduction of the water temperature deviation accompanying the temperature decrease, but the closing-side control at this time is also performed gradually as indicated by the broken line Ea in fig. 4, and therefore the decrease in the cooling water temperature cannot be sufficiently suppressed, and the water temperature T is greatly deviated from the target water temperature tgt to the low temperature side as indicated by the broken line Fa in fig. 4.

The above-described improper cooling water temperature decrease occurs every time the flow path switching valve is switched, and the problems of fuel efficiency and exhaust characteristics are deteriorated due to an increase in the oil viscosity of the engine and defective vaporization of fuel.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a cooling device for an engine that can prevent a rapid decrease in cooling water temperature when an opening control is performed on a flow path switching valve from closing the valve, and can maintain the engine in a good temperature range.

Technical proposal adopted for solving the technical problems

In order to achieve the above object, a cooling device for an engine according to the present invention includes: a flow rate adjustment unit that adjusts a 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 the cooling water based on an operation state of the engine; a deviation calculating section that calculates a water temperature deviation based on the water temperature detected by the water temperature detecting section and the target water temperature calculated by the target water temperature calculating section; a target opening degree calculation unit that calculates a target opening degree of the flow rate adjustment unit for achieving the target water temperature, based on the water temperature deviation calculated by the deviation calculation unit; an opening/closing direction determination unit that determines the opening/closing direction of the flow rate adjustment unit based on the state of change of the target opening degree calculated by the target opening degree calculation unit; a control speed calculation unit that calculates a control speed of the flow rate adjustment unit based on the water temperature deviation calculated by the deviation calculation unit, and calculates a control speed higher than that in the case where the opening/closing direction is determined to be on the opening side when the opening/closing direction determination unit determines that the opening/closing direction is on the closing side; and a valve control unit that controls the opening of the flow rate adjustment unit based on the target opening calculated by the target opening calculation unit and the control speed calculated by the control speed calculation unit.

As another aspect, the vehicle control device may further include a first storage unit that stores a relationship between a preset water temperature deviation and a target opening degree, and the target opening degree calculation unit may calculate the target opening degree from the water temperature deviation based on the relationship stored in the first storage unit.

As another aspect, the present invention may further include a water temperature deviation correcting unit that calculates a corrected water temperature deviation based on at least a proportional term and an integral term of the basic water temperature deviation, wherein the first storage unit stores a relationship between the corrected water temperature deviation and a target opening, the target opening calculating unit calculates the target opening based on the corrected water temperature deviation, the opening/closing direction determining unit determines the opening/closing direction based on the target opening calculated based on the corrected water temperature deviation, the control speed calculating unit calculates the control speed based on the basic water temperature deviation, and 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.

As another aspect, the control device may further include a second storage unit that stores a non-limiting value, which is a control speed equal to or higher than a preset relationship between the water temperature deviation and the control speed of the opening side of the flow rate adjustment unit and a response speed of the flow rate adjustment unit, wherein the control speed calculation unit calculates the control speed based on 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 opening side, and sets the non-limiting value stored in the second storage unit as the control speed regardless of the water temperature deviation when the determined opening/closing direction is the closing side.

Effects of the invention

According to the cooling device for an engine of the present invention, it is possible to prevent the rapid decrease in the cooling water temperature when the flow path switching valve is opened from the closing of the valve, and to maintain the engine in a good temperature range.

Drawings

Fig. 1 is an overall configuration diagram showing a cooling device of an engine according to an embodiment.

Fig. 2 is a control block diagram showing the structure of the ECU.

Fig. 3 is a flowchart showing a water temperature control routine executed by the ECU.

Fig. 4 is a timing chart comparing the control states of the cooling water temperature in the technique of the embodiment and patent document 1.

Detailed Description

An embodiment of a cooling device for an engine embodying the present invention will be described below.

The engine 1 of the present 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, the cooling water discharged from the water pump 4 flows through the water jacket 3 formed in the engine 1, and then flows out from the water jacket 3 into the outflow passage 5 connected to one side of the engine 1. One end of a main water passage 6, an auxiliary water passage 7, and a bypass water passage 8 are connected to the outflow passage 5, respectively, and the other end of the bypass water passage 8 is connected to the suction side of the water pump 4.

A radiator 9 is provided in the main water passage 6, and the other end of the main water passage 6 is connected to the suction side of the water pump 4. The sub-waterways 7 are branched into two, and are provided with an EGR valve 10 for circulating exhaust gas to the intake side and a throttle device 11 for adjusting the intake air amount, and the other end of each sub-waterway 7 is connected to the main waterway 6 at a position closer to the water pump 4 than the radiator 9.

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 returns to the water pump 4 after the temperature is lowered. The cooling water led 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 returns to the water pump 4. The cooling water guided from the outflow path 5 to the bypass water path 8 is returned to the water pump 4 directly at such a temperature.

A flow path switching valve 12 is disposed in the outflow path 5, and the flow path of the cooling water is continuously regulated by the flow path switching valve 12. 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 waterway 6 and the sub waterway 7, respectively. The flow path switching valve 12 is configured to rotate a built-in rotor 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, and thereby 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 is changed.

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

When the flow path of the cooling water 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, and therefore, in the present embodiment, the flow path switching valve 12 functions as the flow rate adjusting portion of the present invention.

The operation state of the cooling device 2 is controlled by an ECU15 (electronic control unit), and the ECU15 includes an input/output interface 15a, a storage device 15b (ROM, RAM, etc.) having a plurality of control programs incorporated therein, a central processing unit 15C (CPU), a timer 15d, and the like. Various sensors such as 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 the cooling water flowing out from the engine 1 into the outflow path 5 as an engine temperature T, and a second water temperature sensor 18 for detecting the temperature of the cooling water passing through the radiator 9 are connected to the input side of the ECU 15.

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 the present embodiment, the engine temperature T corresponds to the temperature of the cooling water flowing through the engine 1 of the present invention, and the first water temperature sensor 17 that detects the engine temperature T functions as the water temperature detection unit of the present invention.

Next, the configuration of the ECU15 will be described based on the control block diagram of fig. 2.

The target water temperature calculation unit 21 of the ECU15 calculates a target water temperature tgt of the cooling water based on the operation state of the engine 1, and inputs the target water temperature tgt to the deviation calculation unit 22 together with the engine temperature T detected by the first water temperature sensor 17.

The deviation calculating unit 22 calculates a basic water temperature deviation Δtbase as a difference between the target water temperature tgtT and the engine temperature T, and inputs the basic water temperature deviation Δtbase 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, the I term setting unit 23b sets an integral term, and the addition unit 23c adds the feedback terms to calculate the corrected water temperature deviation Δt based on PI control.

In the present embodiment, the PI control unit 23 functions as a water temperature deviation correction unit according to the present invention. In addition, instead of PI control, PD control or PID control may be provided, and 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 corrected water temperature deviation Δt is input to the target opening calculating unit 24, and the target radiator opening tgtA is calculated based on the corrected water temperature deviation Δt. For the above calculation processing, a control map that predefines the relationship between the corrected water temperature deviation Δt and the target radiator opening tgtA is stored in the memory device 15b of the ECU 15. Table 1 below shows an example of the control map, and is set to have a characteristic that the target radiator opening tgtA increases together with an increase in the corrected water temperature deviation Δt. For example, the target radiator opening tgta=0% is calculated when the corrected water temperature deviation Δt=0 ℃, and the target radiator opening tgta=100% is calculated when the corrected water temperature deviation Δt=10 ℃.

In the present embodiment, the storage device 15b storing the control map of table 1 functions as the first storage unit of the present invention.

TABLE 1

(Table 1)

ΔT(℃)	0	1	2	3	4	5	6	7	8	9	10
												tgtA(％)	0	0	1	3	6	13	22	34	51	73	100

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

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

For the calculation processing described above, a control map in which the relationship between the basic water temperature deviation Δtbase and the control speed θspd is predetermined is stored in the memory device 15b of the ECU15 in association with each of the speed calculation units 26b and 26c. Table 2 below shows an example of the control map applied to the open-side speed calculation unit 26b, and table 3 below shows an example of the control map applied to the closed-side speed calculation unit 26c.

In the present embodiment, the storage device 15b storing the control maps of table 2 and table 2 functions as the second storage unit of the present invention.

TABLE 2

(Table 2)

TABLE 3

(Table 3)

As shown in table 2, when the flow path switching valve 12 is controlled to be on the open side, the control speed θspd is calculated to be higher as the basic water temperature deviation Δtbase is larger. The above mapping characteristics are based on the following insight: the more the engine temperature T deviates from the target water temperature tgtT, the more rapid rotor angle control of the flow path switching valve 12 is required. However, the control speed θspd on the open side set in table 2 is relatively low, and the flow path switching valve 12 is manufactured to the following specifications: has a response speed that can sufficiently follow the maximum control speed θspd=8 (%/sec).

The basic water temperature deviation Δtbase is applied to the calculation process of the control speed θspd with respect to the target radiator opening tgtA obtained from the corrected water temperature deviation Δt applied to the judgment process of the opening and closing direction of the flow path switching valve 12 and the control of the radiator opening a described later, based on the following findings. As will be described later, the actual radiator opening a and the rotor angle θ of the flow path switching valve 12 are feedback-controlled based on the target radiator opening tgtA. Therefore, by applying the target radiator opening tgtA based on the corrected water temperature deviation Δt reflecting the PI control, it is possible to realize accurate control of the radiator opening a, and also to accurately determine the opening and closing direction of the flow path switching valve 12 controlled based on the rotor angle θ.

In contrast, the control speed θspd needs to be controlled in accordance with the state of deviation of the engine temperature T from the target water temperature tgt at that time as described above. Therefore, the flow path switching valve 12 can be driven at an appropriate control speed θspd by setting the basic water temperature deviation Δtbase, which is the deviation between the actual target water temperature tgt and the engine temperature T, more preferably than the corrected water temperature deviation Δt including the delay element based on the I control.

On the other hand, as shown in table 3, when the flow path switching valve 12 is controlled to be closed side, the control speed θspd=200 (%/sec) significantly higher than the control speed θspd at the time of the open side control is uniformly calculated regardless of the magnitude of the basic water temperature deviation Δtbase. The control speed θspd is a value equal to or greater than the response speed of the flow path switching valve 12 corresponding to the non-limiting value of the present invention, and the flow path switching valve 12 is necessarily driven at the maximum speed. The driving of the flow path switching valve 12 on the closing side based on the relatively higher control speed θspd than on the opening side as described above is to solve the problem carried by the technology of patent document 1, and this will be described in detail below based on a timing chart.

The control speed θspd calculated by the open-side speed calculation portion 26b or the close-side speed calculation portion 26c of the control speed calculation portion 26 is input to the valve control portion 27 together with the target radiator opening tgtA calculated by the target opening calculation portion 24. Although not shown, the memory device 15b of the ECU15 stores a control map defining the relationship between the radiator opening a and the rotor angle θ of the flow path switching valve 12, and the valve control unit 27 calculates the target rotor angle tgt θ from the target radiator opening tgt a by referring to the map. Further, feedback control is performed based on a deviation between the target rotor angle tgt θ and the actual rotor angle θ detected by the position sensor 16 while maintaining the opening/closing speed of the flow path switching valve 12 at the control speed θspd.

Next, the control contents of the ECU15 described above will be described based on the flowchart of fig. 3.

First, in step 1, detection information is read from each sensor, a basic water temperature deviation Δtbase is calculated in the next step 2, and a corrected water temperature deviation Δt is calculated in step 3. The process of step 2 is executed by the deviation calculating section 22, and the process of step 3 is executed by the PI control section 23. Then, the target radiator opening tgtA is calculated based on the control map of table 1 in step 4, and the direction of change of the target radiator opening tgtA is determined in step 5. The processing of step 4 is executed by the target opening degree calculating unit 24, and the processing of step 5 is executed by the opening/closing direction determining unit 25.

When the change direction determined in step 5 is on, the process proceeds from step 6 to step 7, and the on-side control speed θspd is calculated based on the control map of table 2. When the change direction is on the closed side, the routine proceeds from step 6 to step 8, and the control speed θspd on the closed side is calculated based on the control map of table 3. Then, in step 9, the flow path switching valve 12 is feedback-controlled based on the target radiator opening tgtA and the control speed θspd. The processing of step 6 is performed by the switching unit 26a of the control speed calculating unit 26, the processing of step 7 is performed by the open side speed calculating unit 26b, the processing of step 8 is performed by the closed side speed calculating unit 26c, and the processing of step 10 is performed by the valve control unit 27.

Next, a control state of the cooling water temperature by the processing of the ECU15 will be described based on the timing chart of fig. 4.

In the above-described figures, for ease of understanding, the target water temperature tgtT is shown to be constant, and for example, when the engine temperature T is equal to or lower than the target water temperature tgtT, the target radiator opening tgta=0% is calculated based on table 1, and the main water passage 6 is fully closed by the flow path switching valve 12. Therefore, the cooling water circulates in the water jacket 3 of the engine 1 via the bypass water passage 8 or the sub water passage 7 in a state not cooled by the radiator 9, and as shown in fig. 4 a, the engine temperature T gradually rises due to receiving heat from the engine 1. At this time, the cooling water is retained in the radiator 9, and the temperature is gradually lowered by cooling with the running wind.

When the engine temperature T > the target water temperature tgt as shown in fig. 4B due to the temperature rise of the cooling water, the flow path switching valve 12 is controlled to open based on the target radiator opening tgtA calculated from table 1. The control speed θspd 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 be opened gradually as shown in fig. 4C. However, since the low-temperature cooling water cooled in the radiator 9 flows into the water jacket 3, the engine temperature T is changed from rising to falling as shown by D in fig. 4, and is drastically reduced.

In response to the reduction of the corrected water temperature deviation Δt accompanying the above-described temperature decrease, the flow path switching valve 12 is closed-side controlled based on the target radiator opening tgtA calculated from table 1. 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 rapidly controlled to be closed as indicated by a solid line Eb in fig. 4. Therefore, the decrease in the engine temperature T is quickly suppressed, and the engine temperature T is changed to rise in a state that is less likely to be deviated from the target water temperature tgtT toward the low temperature measurement as indicated by the solid line Fb in fig. 4. The decrease in the engine temperature T greatly departing from the target water temperature tgtT causes an increase in the oil viscosity and defective vaporization of the fuel, and this can be prevented from being the case, but the engine 1 is not kept in a good temperature range, so that the fuel efficiency and the exhaust characteristics can be improved.

The meaning of the cooling device of the engine 1 of the present embodiment can be understood as follows. In the first place of the electronic control type cooling device being put into practical use, characteristics of a thermostat are often simulated to impart characteristics of slowly opening and closing a flow path switching valve. Further, since importance is attached to preventing the engine from overheating at that time, from this point of view, it is considered that the control speed at the time of opening the valve should be increased more preferentially than at the time of closing the flow path switching valve, so that the abrupt increase in the engine temperature T is suppressed. However, any control characteristic cannot avoid a sharp decrease in the cooling water temperature as described based on fig. 4.

The above-described failure is caused by a phenomenon in which low-temperature cooling water in the radiator 9 flows into the water jacket 3 by the open-side control of the flow path switching valve 12, and in addition, the original characteristics of the engine 1 as follows are also affected: the water temperature drop due to cooling in the radiator 9 occurs more rapidly than the water temperature rise due to heat received from the engine 1. On the other hand, in order to meet the recent demands concerning fuel efficiency and exhaust characteristics, it is more important to prevent supercooling of the engine 1, which is a factor of an increase in the viscosity of oil and vaporization failure of fuel, than to prevent overheating of the engine 1.

From the viewpoints of both the original characteristics of the engine 1 and the requirements relating to the fuel efficiency and the exhaust characteristics as described above, it is apparent that cooling control is required to prevent supercooling of the engine 1 with priority. The above-described requirement can be achieved by the cooling control in which the control speed θspd at the time of closing the valve is increased compared with the valve opening time of the flow path switching valve 12 as in the present embodiment, and as a result, the above-described operational effects can be achieved.

On the other hand, the target opening degree calculating 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 15 b. Therefore, the feedback control is performed on the rotor angle θ of the flow path switching valve 12 in response to the control map in addition to the PI control based on the corrected water temperature deviation Δt. For example, in the control map of table 1, the target radiator opening tgtA is rapidly increased with respect to the increase in the corrected water temperature deviation Δt, so that the increase in the engine temperature T can be reliably suppressed. Since the content of the feedback control can be arbitrarily changed based on the map characteristic as described above, the engine 1 can be maintained in a more favorable temperature region.

The embodiments described above have been described, but the embodiments of the present invention are not limited to the above embodiments. For example, in the above embodiment, the cooling device 2 mounted on the engine 1 of the passenger car is embodied, but the present invention is not limited to this. For example, the present invention may be embodied as an engine cooling device mounted on a motorcycle or ATV (All Terrain Vehicle: ATV). The configuration of the water path of the cooling device 2 shown in fig. 1 is not limited to this, and can be arbitrarily changed.

(symbol description)

1. Engine with a motor

9. Radiator

12. Flow path switching valve (flow regulating part)

15b storage device (first storage portion, second storage portion)

17. First water temperature sensor (Water temperature detecting part)

21. Target water temperature calculating unit

22. Deviation calculating part

23 PI control unit (Water temperature deviation correction unit)

24. Target opening degree calculating unit

25. Opening/closing direction judging unit

26. Control speed calculation unit

27. And a valve control unit.

Claims

1. A cooling device of an engine, comprising:

a flow rate adjustment unit that adjusts a flow rate of cooling water circulating between the engine and the radiator;

a water temperature detection unit that detects a 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 an operation state of the engine;

a deviation calculating unit that calculates a water temperature deviation based on the water temperature detected by the water temperature detecting unit and the target water temperature calculated by the target water temperature calculating unit;

a target opening degree calculation unit that calculates a target opening degree of the flow rate adjustment unit for achieving the target water temperature, based on the water temperature deviation calculated by the deviation calculation unit;

an opening/closing direction determination unit that determines an opening/closing direction of the flow rate adjustment unit based on the state of change of the target opening degree calculated by the target opening degree calculation unit;

a control speed calculation unit that calculates a control speed of the flow rate adjustment unit based on the water temperature deviation calculated by the deviation calculation unit, and calculates a control speed higher than that in the case where the opening/closing direction determined by the opening/closing direction determination unit is on the opening side; and

and a valve control unit that controls the opening of the flow rate adjustment unit based on the target opening calculated by the target opening calculation unit and the control speed calculated by the control speed calculation unit.

2. The cooling device of an engine according to claim 1, wherein,

further comprising a first storage unit for storing a relationship between a preset water temperature deviation and a target opening degree,

the target opening degree calculation unit calculates the target opening degree from the water temperature deviation based on the relationship stored in the first storage unit.

3. The cooling apparatus of an engine according to claim 2, wherein,

further comprising a water temperature deviation correction unit that calculates a corrected water temperature deviation based on at least a proportional term and an integral term of the basic water temperature deviation, using the water temperature deviation as the basic water temperature deviation,

the first storage unit stores a relationship between the corrected water temperature deviation and the target opening degree,

the target opening degree calculating section calculates the target opening degree based on the corrected water temperature deviation,

the opening/closing direction determination unit determines an opening/closing direction based on the target opening degree calculated from the corrected water temperature deviation,

the control speed calculation section calculates the control speed based on the basic water temperature deviation,

the valve control unit controls the opening of the flow rate adjustment unit based on a target opening calculated from the corrected water temperature deviation.

4. A cooling device for an engine according to any one of claims 1 to 3, characterized in that,

further comprising a second storage unit for storing a non-limiting value, which is a control speed equal to or higher than a response speed of the flow rate adjustment unit, in relation to a preset water temperature deviation and a control speed on an open side of the flow rate adjustment 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 on the opening side, and sets the unrestricted value stored in the second storage unit as the control speed regardless of the water temperature deviation when the opening/closing direction determined by the opening/closing direction determination unit is on the closing side.