JP2016003578A - Engine cooling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine cooling device capable of suitably suppressing a water temperature fluctuation after opening a radiator pathway.SOLUTION: The engine cooling device includes a radiator pathway 16, as a pathway for making cooling water passing through the inside of an engine recirculate in the engine, going through a radiator 19, and a bypass pathway 17 bypassing the radiator 19. The engine cooling device, having an electronic thermostat 21 for opening/closing the radiator pathway 16, forcibly opens the electronic thermostat 21 when an engine discharged water temperature as the temperature of the cooling water passing through the inside of the engine is equal to or higher than a specified valve opening temperature. In starting the forcible opening, when there is a big difference between the temperature of the cooling water inside the radiator 19 and the engine discharged water temperature, the opening speed of the electronic thermostat 21 is set to be lower than when there is a small difference between the temperatures.

Description

  The present invention includes a radiator path for circulating cooling water via a radiator and a bypass path for circulating cooling water without passing through a radiator as a path for returning the cooling water that has passed through the engine to the engine. The present invention relates to an engine cooling device.

  Conventionally, an apparatus described in Patent Document 1 is known as an engine cooling apparatus including the above-described radiator path and bypass path. The engine cooling device described in the same document includes an electronic thermostat having a built-in heater that forcibly heats the thermowax in response to energization, as an on-off valve that opens and closes the radiator path.

  The energization control of the heater in such an electronic thermostat is performed based on the temperature of the cooling water that has passed through the engine (hereinafter referred to as the engine outlet water temperature THW) and the engine load KL. Specifically, on the condition that the engine outlet water temperature THW is equal to or higher than the specified valve opening temperature α and the engine load KL is equal to or higher than the specified valve opening load β, the heater is energized to open the electronic thermostat. By letting the valve to flow and cooling water to flow through the radiator path, engine overheating is suppressed and knocking is suppressed. Energization of the heater is continued until the above condition is not satisfied due to a decrease in the engine outlet water temperature THW or the engine load KL.

JP 2012-184893 A

  If the radiator path is closed for a long time, the temperature of the cooling water remaining in the radiator (hereinafter referred to as the radiator water temperature THR) is reduced due to heat radiation to the outside air, and the engine outlet water temperature THW The difference becomes larger. In this state, when the radiator path is opened at once, a large amount of cooling water in the relatively low-temperature radiator 19 flows into the cooling water in the bypass path that passes through the engine and circulates. The water temperature THW decreases rapidly. As a result, when the engine outlet water temperature THW decreases until it becomes lower than the valve opening temperature α, the heater is deenergized and the radiator path is closed again. When the radiator path is closed, the engine outlet water temperature THW rises again to the valve opening temperature α or higher due to heat received from the engine. Thereafter, until the engine water temperature THW and the radiator water temperature THR become uniform, the engine water temperature THW rises and falls across the valve opening temperature α, and the opening and closing of the electronic thermostat is repeated. The engine operation becomes unstable due to such fluctuations in the engine outlet water temperature THW.

  The present invention has been made in view of such circumstances, and a problem to be solved is to provide an engine cooling device that can suitably suppress fluctuations in water temperature after opening a radiator path.

  An engine cooling device that solves the above-mentioned problems is a path for circulating cooling water that has passed through the inside of the engine to the engine, and a radiator path that circulates cooling water through the radiator, and cooling water that does not go through the radiator. And a bypass path for refluxing. The engine cooling system also regulates the flow of cooling water through the radiator path when the valve is closed, and allows an on-off valve that is open when the valve is open. The engine outlet temperature is the temperature of the cooling water that has passed through the engine. The valve is opened when the valve opening temperature is higher than.

  If there is a large difference between the water temperature inside the radiator, which is the temperature of the cooling water inside the radiator, and the engine outlet water temperature, if the radiator path is suddenly opened, a large inflow of cooling water inside the radiator, which is relatively cool, causes a large inflow of engine water. The water temperature drops rapidly, causing water temperature fluctuations. On the other hand, in the engine cooling device, when the difference between the water temperature in the radiator and the engine outlet water temperature when the opening / closing valve is open is large, the opening speed of the opening / closing valve is lower than when the temperature difference is small. It will be lost. Therefore, at this time, the inflow amount of the cooling water inside the radiator immediately after the opening of the on-off valve is reduced. On the other hand, even if the opening speed of the on-off valve is reduced, there is no change in the total circulation amount of the cooling water, so that a relatively large amount of cooling water flows through the bypass path at this time. Even if some of the internal cooling water flows in, the temperature drop remains relatively small. Therefore, according to the engine cooling device, a decrease in the engine water temperature when the radiator path is opened in a state where the difference between the water temperature in the radiator and the engine water temperature is large, and the subsequent water temperature fluctuation can be suppressed.

  In order to more reliably suppress fluctuations in the water temperature after opening the radiator path, it is desirable to suppress the inflow of cooling water from the inside of the radiator until the temperature difference becomes sufficiently small. Therefore, when the temperature difference at the start of opening of the on-off valve is large, the valve opening speed is decreased until the temperature difference is not more than a specified value when the temperature difference is small. It is good to do so.

  On the other hand, if the valve opening speed of the on-off valve is decreased, it takes time to increase the flow rate of the cooling water in the radiator path, so that the response speed of the cooling water temperature control decreases. For this reason, when the temperature difference at the start of opening of the on-off valve is large, it is desirable that the decrease rate of the valve opening speed with respect to the small temperature difference is reduced in accordance with the reduction of the temperature difference.

  Further, if it is attempted to obtain the difference between the engine water temperature and the radiator water temperature by actual measurement, an additional temperature sensor for detecting the radiator water temperature is required. On the other hand, if the difference between these temperatures is estimated and calculated based on the elapsed time from the previous opening of the on-off valve, the outside air temperature, and the vehicle speed, the additional installation of such a sensor becomes unnecessary, and the above engine cooling The apparatus can have a simpler configuration.

  As an on-off valve for such an engine cooling device, for example, an electronic thermostat equipped with a heater for forcibly heating thermowax can be employed. Further, when such an electronic thermostat is employed as an on-off valve, the heater may be energized by periodically turning on and off the heater. Here, in the energization control, when the period from when the energization of the heater is turned on to when the energization once turned off is turned on again is defined as the energization cycle, the heater within the energization period with respect to the energization cycle If the ratio of the time during which the energization is turned on is changed, the heating speed of the thermowax by the heater, and thus the valve opening speed of the electronic thermostat can be changed. Therefore, when an electronic thermostat is employed as the on-off valve, the valve opening speed may be changed by changing such a time ratio. Incidentally, it is possible to change the valve opening speed of the electronic thermostat by changing the voltage applied to the heater, but in such a case, a voltage raising / lowering circuit such as a DC / DC converter is required. On the other hand, if the valve opening speed is changed by changing the ratio, the valve opening speed can be changed simply by switching the heater energization on and off, thereby simplifying the configuration of the engine cooling device. Can do.

1 is a schematic diagram schematically showing the configuration of an embodiment of an engine cooling device. The time chart which shows transition of the cooling water temperature at the time of forced valve opening of an electronic thermostat when a valve opening interval is long in the conventional engine cooling device, and heater energization condition. The flowchart which shows the process sequence of the temperature difference counter calculation routine performed with the engine cooling device of FIG. The graph which shows the relationship between the addition value of the temperature difference counter calculated by the same temperature difference counter calculation routine, outside air temperature, and vehicle speed. The flowchart which shows the process sequence of the thermo valve opening control routine performed with the engine cooling device of FIG. The graph which shows the relationship between the duty ratio of the heater computed by the thermo valve opening control routine, the temperature difference counter, and the cooling water temperature (engine outlet temperature). (A)-(d) The time chart which shows the electricity supply mode of the heater performed through the process of the thermo valve opening control routine. The time chart which shows an example of the embodiment of the thermo valve opening control in the engine cooling device of FIG.

Hereinafter, an embodiment of an engine cooling device will be described in detail with reference to FIGS.
As shown in FIG. 1, the engine cooling device is configured to recirculate the water jacket 12 formed inside the cylinder block 10 and the cylinder head 11 of the engine and the cooling water that has passed through the water jacket 12 to the water jacket 12. Cooling water passage 13. The cooling water channel 13 is provided in the vicinity of the cooling water inlet of the water jacket 12 and includes a water pump 14 for circulating the cooling water through the water jacket 12 and the cooling water channel 13. The cooling water channel 13 is installed in the vicinity of the cooling water outlet of the water jacket 12 and detects the temperature of the cooling water that has passed through the water jacket 12 (hereinafter referred to as engine outlet temperature THW). Have

  The middle of the cooling water passage 13 is branched into three paths, namely, a radiator path 16, a bypass path 17, and a heater path 18. The radiator path 16 is provided with a radiator 19 for cooling the cooling water by running air or forced air blowing by a fan. The heater path 18 is provided with a heater radiator 20 for heating the air to the passenger compartment with the heat of the cooling water.

  An electronic thermostat 21 as an on-off valve that opens and closes the radiator path 16 is installed at a portion of the cooling water path 13 where the radiator path 16 and the bypass path 17 merge. The electronic thermostat 21 has a valve body 22, a spring 23, a thermo wax part 24, and a heater 25. When the valve body 22 is closed, the radiator passage 16 is closed and the flow passage area of the radiator passage 16 is enlarged in accordance with the increase in the opening degree. The spring 23 biases the valve body 22 toward the valve closing side. The thermo wax part 24 presses the valve body 22 to the valve opening side by volume expansion due to melting of the thermo wax provided inside. The heater 25 generates heat in response to energization and forcibly heats the thermowax unit 24.

  Energization of the heater 25 of the electronic thermostat 21 is controlled by an electronic control unit 26 that controls the engine. The electronic control unit 26 includes a central processing unit (CPU) that performs various arithmetic processes related to engine control, a read-only memory (ROM) that stores programs and data for engine control, CPU calculation results, and sensor detection results. Is provided with a readable / writable memory (RAM) in which the information is temporarily stored. In addition to the water temperature sensor 15, the electronic control unit 26 detects various sensors for detecting the operating status of the engine and the vehicle, such as a crank angle sensor 27, an accelerator pedal sensor 28, an outside air temperature sensor 29, and a vehicle speed sensor 30. A signal is being input. And the electronic control unit 26 performs energization control of the heater 25 based on the detection result of these sensors.

  In such an engine cooling device, the electronic control unit 26 starts energization of the heater 25 of the electronic thermostat 21 when the forced valve opening condition of the electronic thermostat 21 is satisfied. The forced valve opening condition is satisfied when the engine outlet water temperature THW is equal to or higher than the specified valve opening temperature α and the engine load KL is equal to or higher than the specified valve opening load β.

  In the electronic thermostat 21, when energization to the heater 25 is started, the thermowax unit 24 is heated by the heat generated by the heater 25 and its volume expands. And by the press by the volume expansion, the valve body 22 opens against the urging | biasing force of the spring 23, and the radiator path | route 16 is opened. As a result, a part of the cooling water flowing out from the water jacket 12 is sent to the radiator 19 and cooled by the radiator 19. As a result, the engine outlet water temperature THW and, consequently, the engine temperature decreases, and the occurrence of knocking due to overheating of the engine is suppressed.

  In a cold environment such as winter, if the radiator path 16 continues to be closed, the temperature of the cooling water inside the radiator 19 (hereinafter referred to as the radiator water temperature THR) decreases due to heat radiation to the outside air. In this state, if the electronic thermostat 21 is suddenly opened, fluctuation (hunting) of the engine outlet water temperature THW occurs.

  FIG. 2 shows changes in the engine outlet water temperature THW and the energization state of the heater 25 in such a case. In the example of the figure, the state where the electronic thermostat 21 is closed continues for a long time, and the engine outlet water temperature THW exceeds the valve opening temperature α at the time t1 when the difference between the engine outlet water temperature THW and the radiator water temperature THR increases, and the heater 25 Energization to is started.

  After the start of energization, when the temperature of the thermowax 24 is sufficiently increased by the heating of the heater 25, the valve body 22 of the electronic thermostat 21 is opened. Thereby, when the radiator path 16 is opened, the cooling water inside the radiator 19 having a relatively low temperature flows into the cooling water circulating through the water jacket 12, and the engine outlet temperature THW is lowered. At this time, if the difference between the engine outlet water temperature THW and the radiator inner water temperature THR is sufficiently large, the engine outlet water temperature THW decreases until it falls below the valve opening temperature α, and as a result, the energization of the heater 25 is stopped (time t2). .

  When the energization of the heater 25 is stopped, the temperature of the thermowax unit 24 decreases, and the valve body 22 of the electronic thermostat 21 is eventually closed, and the radiator path 16 is closed. Then, the engine outlet water temperature THW starts to rise due to heat received from the engine. When the engine outlet water temperature THW exceeds the valve opening temperature α at time t3, energization to the heater 25 is resumed. Thereafter, the engine water temperature THW is repeatedly raised and lowered by energizing and stopping the heater 25 until the engine water temperature THW and the radiator water temperature are equalized.

  Therefore, in the engine cooling device of the present embodiment, when the difference between the engine outlet water temperature THW and the radiator water temperature THR at the start of valve opening of the electronic thermostat 21 (hereinafter referred to as temperature difference ΔTH) is large, the temperature difference ΔTH is The energization of the heater 25 is controlled so that the valve opening speed of the electronic thermostat 21 is smaller than when it is small. As a result, a decrease in the engine water temperature THW after the opening of the electronic thermostat 21 is moderated, thereby suppressing fluctuations in the engine water temperature THW.

  In the engine cooling device of the present embodiment, the temperature difference counter DT is used as the index value of the temperature difference ΔTH. The value of the temperature difference counter DT is calculated according to the elapsed time from the previous opening of the electronic thermostat 21, the outside air temperature THA, and the vehicle speed SPD.

  FIG. 3 shows a processing procedure of a temperature difference counter calculation routine for calculating the temperature difference counter DT. The electronic control unit 26 repeatedly executes the process of the routine at regular control cycles during engine operation.

  When the processing of this routine is started, first, in step S100, it is determined whether or not the condition for forced opening of the electronic thermostat 21 is satisfied. If the forced valve opening condition is satisfied (S100: YES), the process of this routine is terminated after the value of the temperature difference counter DT is decreased by the subtraction value DEC set as a constant in step S110. Is done. In the temperature difference counter DT, “0” is set as the lower limit value.

  On the other hand, if the forced valve opening condition is not satisfied (S100: NO), the outside air temperature THA and the vehicle speed SPD are read in step S120. In subsequent step S130, based on the outside air temperature THA and the vehicle speed SPD, an addition value INC of the temperature difference counter DT in the current control cycle is calculated. Then, in the next step S140, after the value of the temperature difference counter DT is increased by the added value INC, the process of this routine is terminated.

  As shown in FIG. 4, the value of the added value INC is set to a larger value as the outside air temperature THA is lower or the vehicle speed SPD is higher. Such an added value INC corresponds to the rate of decrease in the water temperature in the radiator. The radiator 19 is more easily cooled as the outside air temperature THA is lower, and more easily cooled by the traveling wind as the vehicle speed SPD is higher. For this reason, it is considered that the lower the outside air temperature THA and the higher the vehicle speed SPD, the higher the rate of decrease of the radiator water temperature THR, and the setting of the added value INC is in accordance with this. Therefore, the value of the temperature difference counter DT during the period when the forced valve opening condition is not satisfied is the amount of decrease in the radiator water temperature THR after the forced valve opening condition is not satisfied and the radiator passage 16 is closed, and thus the current temperature. The value corresponds to the difference ΔTH.

  On the other hand, the subtraction value DEC corresponds to the reduction speed of the temperature difference ΔTH after the radiator path 16 is opened. In the present embodiment, the subtraction value DEC is a constant, but may be a variable corresponding to the current value of the temperature difference counter DT or the outside air temperature THA, for example.

  In the engine cooling device of this embodiment, the valve opening speed of the electronic thermostat 21 is changed according to the temperature difference ΔTH by controlling the power supplied to the heater 25 according to the value of the temperature difference counter DT. ing. In the engine cooling device of this embodiment, energization control of the heater 25 is performed by periodically turning on and off energization. Here, in the energization control, a period from when the energization of the heater 25 is turned on to when the energization once turned off is turned on again is defined as an energization cycle. And the valve opening speed of the electronic thermostat 21 at this time is changed by changing the ratio of the period in which the energization is turned on within the energization period to the energization period.

  FIG. 5 shows a processing procedure of a thermo valve opening control routine for controlling the valve opening speed of the electronic thermostat 21. The electronic control unit 26 repeatedly executes the process of the routine at regular control cycles during engine operation.

  When this routine is started, first, in step S200, it is determined whether or not a forced valve opening condition for the electronic thermostat 21 is satisfied. In the present embodiment, the forced opening condition of the electronic thermostat 21 is that the engine load KL (load factor) is not less than a specified value and the engine outlet water temperature THW is not less than a specified value.

  Here, if the forced valve opening condition is satisfied (S200: YES), in step S210 to step S230, an operation of an elapsed time counter ET that represents an elapsed time from the start of the current energization cycle is performed. That is, first, in step S210, “1” is added to the value of the elapsed time counter ET, and in the subsequent step S220, it is determined whether or not the value of the elapsed time counter ET after the addition has reached the upper limit value MAX. . The upper limit value MAX is set by dividing the heater energization cycle by the control cycle of this routine. When the elapsed time counter ET reaches the upper limit MAX, the current energization cycle ends. Means.

  If the value of the elapsed time counter ET has reached the upper limit value MAX (S220: YES), the value of the elapsed time counter ET is reset to “0”, and the process proceeds to step S240. On the other hand, if the value of the elapsed time counter ET has not reached the upper limit value MAX (S220: NO), the process proceeds to step S240 while maintaining the value of the elapsed time counter ET added in step S210.

  When the process proceeds to step S240, the outside air temperature THA, the engine outlet water temperature THW, and the temperature difference counter DT are read in step S240. In subsequent step S250, the energization duty ratio DUTY is calculated based on the outside air temperature THA, the engine outlet water temperature THW, and the temperature difference counter DT. The energization duty ratio DUTY represents a ratio of a period in which energization within the same energization period is on with respect to the energization period, and its value is set in a range from “0” to “1”.

  When the energization duty ratio DUTY is calculated, it is determined in subsequent step S260 whether or not the elapsed time counter ET is less than a product value (= DUTY × MAX) of the energization duty ratio DUTY and the upper limit value MAX. If the elapsed time counter ET is less than the multiplication value (S260: YES), the energization of the heater 25 is turned on (implemented) in step S270. If the elapsed time counter ET is equal to or greater than the multiplication value (S260: NO), step In S280, energization of the heater 25 is turned off (stopped). Thereafter, the processing of this routine is terminated.

  If the forced valve opening condition is not satisfied (S200: NO), the value of the elapsed time counter ET is reset to “0” in step S290, and the energization of the heater 25 is turned off in step S280. Then, the process of this routine is terminated.

  FIG. 6 shows the relationship between the temperature difference counter DT and the engine outlet water temperature THW and the energization duty ratio DUTY. As shown in the figure, the energization duty ratio DUTY is set to a smaller value as the value of the temperature difference counter DT increases, that is, as the difference between the engine outlet water temperature THW and the radiator water temperature THR increases. The energization duty ratio DUTY is set to a larger value as the engine outlet water temperature THW is higher. Although not shown in the figure, the energization duty ratio DUTY is set to a larger value as the outside air temperature THA is higher.

  FIG. 7 shows how the heater 25 is energized by the process of the thermo valve opening control routine. As shown in FIG. 7A, the elapsed time counter ET repeats a monotonous increase from “0” to the upper limit value MAX for each energization cycle of the heater 25.

  Here, a case is considered where a smaller value D1 and a larger value D2 are set in the energization duty ratio DUTY. As shown in FIG. 7B, when a smaller value D1 is set in the energization duty ratio DUTY, the value of the elapsed time counter ET is multiplied by the value D1 and the upper limit value MAX from the start of each energization cycle. The energization of the heater 25 is turned on for a period until the value (= D1 × MAX) is reached. When the value of the elapsed time counter ET reaches the multiplication value of the value D1 and the upper limit value MAX, the energization of the heater 25 is turned off until the energization cycle ends. On the other hand, as shown in FIG. 7C, when a larger value D2 is set in the energization duty ratio DUTY, the value of the elapsed time counter ET becomes the value D2 and the upper limit value MAX from the start of each energization cycle. Until the multiplication value (= D2 × MAX) is reached, the energization of the heater 25 is turned on, and then the energization is turned off until the end of the energization cycle. Thus, as the value of the duty ratio DUTY increases, the period during which the energization is turned on within the energization cycle (the energization on time) becomes longer. As shown in FIG. 7D, when “1” is set to the value of the energization duty ratio DUTY, the heater 25 is energized continuously.

  When the energization on-time within the energization cycle is lengthened, the amount of heat generated by the heater 25 per unit time is increased, and the temperature of the thermowax 24 is rapidly increased. Therefore, if other conditions are the same, the valve opening speed of the electronic thermostat 21 increases as the value of the duty ratio DUTY increases. On the other hand, as described above, the energization duty ratio DUTY is set to a smaller value as the difference between the engine outlet water temperature THW and the radiator water temperature THR is larger and the value of the temperature difference counter DT is larger. Therefore, in the engine cooling device of the present embodiment, when the temperature difference ΔTH at the start of valve opening of the electronic thermostat 21 is large, the valve opening speed of the electronic thermostat 21 is made lower than when the temperature difference ΔTH is small.

Next, the effect of the above-described thermo valve opening control routine processing on the operation of the engine cooling device of the present embodiment will be described.
FIG. 8 shows an example of an embodiment of thermo valve opening control. In the figure, the forced valve opening request condition is satisfied in each of the period from time t10 to time t11, the period from time t12 to time t13, and the period from time t14 to time t15. In the figure, the transition of the temperature difference counter DT, the duty ratio DUTY, and the opening of the electronic thermostat 21 (thermo opening) when the electronic thermostat 21 is forcibly opened during these three periods. It is shown.

  The time from the time t11 at which the first forced valve opening in FIG. 9 ends to the time t12 at which the second forced valve opening is started is relatively short. The temperature difference ΔTH is not so large. At such time t12, the elapsed time from the end of the previous forced valve opening is short, and the value of the temperature difference counter DT is not so large. Therefore, in the second forced valve opening, a relatively large value is set as the energization duty ratio DUTY of the heater 25 at the start of the valve opening. As a result, the valve opening speed of the electronic thermostat 21 at this time increases, and the radiator path 16 is opened relatively quickly. At this time, since the temperature difference ΔTH is small, the radiator passage 16 is quickly opened, and even if a large amount of cooling water flows from the inside of the radiator 19 into the cooling water flowing through the bypass passage 17, the engine outlet water temperature THW decreases. Will be limited.

  On the other hand, the time from the time t13 at which the second forced valve opening ends in FIG. 9 to the time t14 at which the third forced valve opening is started is long, and at the time t14 at which the third forced valve opening is started, The temperature difference ΔTH is considerably large. At such time t14, the elapsed time from the end of the previous forced valve opening is long, and the value of the temperature difference counter DT is large. Therefore, at the start of the third forced valve opening, a relatively small value is set for the energization duty ratio DUTY of the heater 25. As a result, the valve opening speed of the electronic thermostat 21 at this time becomes low, and the radiator path 16 is gently opened. Therefore, the inflow amount of the cooling water from the inside of the radiator 19 immediately after the opening of the electronic thermostat 21 is reduced.

  On the other hand, even if the valve opening speed of the electronic thermostat 21 is reduced, there is no change in the total circulation amount of the cooling water. Therefore, a relatively large amount of cooling water flows through the bypass path 17 at this time. Even if a relatively low temperature cooling water flows in from the inside, the temperature drop remains relatively small. For this reason, even when the temperature difference ΔTH at the start of valve opening is large, the decrease in the engine water temperature THW when the radiator passage 16 is opened, and the subsequent fluctuation in the engine water temperature THW can be suppressed.

  Here, if the state in which the valve opening speed is kept low is continued even after the valve opening is started, the time until the radiator passage 16 is completely opened becomes long, so that the response speed of the cooling water temperature control is greatly reduced. . In that respect, in the engine cooling device of the present embodiment, after the valve opening of the electronic thermostat 21 is started, the value of the temperature difference counter DT is gradually decreased in accordance with the reduction of the temperature difference ΔTH. That is, when the temperature difference ΔTH at the start of opening of the electronic thermostat 21 is large, the rate of decrease in the valve opening speed with respect to when the temperature difference ΔTH is small is reduced according to the reduction of the temperature difference ΔTH after the valve opening is started. ing. Therefore, even when the temperature difference ΔTH at the start of valve opening is large and the valve opening speed immediately after that is kept low, the valve opening speed of the electronic thermostat 21 can be increased if the temperature difference ΔTH is reduced thereafter. Become. Therefore, a decrease in the response speed of the cooling water temperature control as described above can be suppressed.

  Strictly speaking, the value of the energization duty ratio DUTY depends on an increase in response to a decrease in the temperature difference ΔTH after the opening of the electronic thermostat 21 and a decrease in the engine outlet water temperature THW after the opening of the valve. All the declines are reflected at the same time. Therefore, in practice, the valve opening speed of the electronic thermostat 21 once increases after the start of the valve opening and then gradually decreases.

  On the other hand, in order to more reliably suppress fluctuations in the engine outlet water temperature THW after the radiator passage 16 is opened, it is necessary to suppress the inflow of cooling water from the inside of the radiator 19 until the temperature difference ΔTH becomes sufficiently small. desirable. In this respect, in the present embodiment, the valve opening speed of the electronic thermostat 21 according to the temperature difference ΔTH at the start of valve opening is suppressed until the value of the temperature difference counter DT becomes “0”, that is, the temperature difference ΔTH is “ It can be continued until “0” is reached.

  Incidentally, in the engine cooling device of the present embodiment, the value of the duty ratio DUTY is reduced as the engine outlet water temperature THW is lower. This is due to the progress of the decrease in the engine outlet water temperature THW due to the forced opening of the electronic thermostat 21. This is because the thermo opening is gradually reduced according to the above. The lower the outside air temperature THA, the smaller the value of the duty ratio DUTY. However, the lower the outside air temperature THA, the higher the cooling efficiency of the radiator 19 and the cooling water flowing through the radiator path 16. This is because the cooling water can be sufficiently cooled even if the amount is small.

According to the engine cooling device of the present embodiment described above, the following effects can be obtained.
(1) In the engine cooling device of the present embodiment, when the electronic thermostat 21 is opened, if the temperature difference between the cooling water that has passed through the engine and the cooling water inside the radiator 19 is large, the temperature difference is The valve opening speed of the electronic thermostat 21 is made smaller than when it is small. Therefore, fluctuations in the engine outlet water temperature THW after opening the radiator path 16 can be suitably suppressed.

  (2) In the engine cooling device of this embodiment, when the temperature difference ΔTH at the start of valve opening of the electronic thermostat 21 is large, the decrease in the valve opening speed with respect to when the temperature difference ΔTH is small is This is repeated until ΔTH becomes “0”. Therefore, fluctuations in the engine outlet water temperature THW after the radiator passage 16 is opened can be more reliably suppressed.

  (3) In the engine cooling device of the present embodiment, when the temperature difference ΔTH at the start of valve opening of the electronic thermostat 21 is large, the amount of decrease in the valve opening speed relative to when the temperature difference ΔTH is small is The temperature is decreased according to the reduction of the temperature difference ΔTH. Therefore, it is possible to suppress a decrease in the response speed of the cooling water temperature control that accompanies the suppression of fluctuations in the engine outlet water temperature THW.

  (4) In the engine cooling device of the present embodiment, the energization of the heater 25 is intermittently turned on / off, and the ratio of the energization on time of the same period to the on / off period of the energization (the energization duty ratio DUTY) is changed. Thus, the valve opening speed of the electronic thermostat 21 is changed. Therefore, it is possible to change the valve opening speed of the electronic thermostat 21 only by switching on / off the energization of the heater 25, and it is possible to suppress the complexity of the configuration of the engine cooling device accompanying the variable valve opening speed. it can.

  (5) In the engine cooling device of the present embodiment, since the duty ratio DUTY of the heater 25 is set according to the current values of the engine outlet water temperature THW and the outside air temperature THA, the controllability of the cooling water temperature control is improved. Can do.

  (6) In the engine cooling device of the present embodiment, the temperature difference counter DT calculated according to the elapsed time from the previous valve opening of the electronic thermostat 21, the outside air temperature THA and the vehicle speed SPD is passed through the inside of the engine. It is used as an index value of the temperature difference between water and the cooling water inside the radiator 19. In other words, in the present embodiment, the temperature difference is estimated and obtained based on the elapsed time from the previous valve opening of the electronic thermostat 21, the outside air temperature THA, and the vehicle speed SPD instead of actual measurement. Therefore, additional installation of a sensor for detecting the water temperature in the radiator is not required, and the engine cooling device capable of suppressing the water temperature fluctuation can be simplified.

In addition, the said embodiment can also be changed and implemented as follows.
In the above embodiment, the temperature difference ΔTH is estimated and obtained based on the elapsed time from the previous opening of the electronic thermostat 21, the outside air temperature THA, and the vehicle speed SPD, but a sensor for detecting the water temperature in the radiator is installed. Then, the temperature difference ΔTH may be obtained by actual measurement.

  In the above embodiment, when the temperature difference ΔTH at the start of valve opening of the electronic thermostat 21 is large, the valve opening speed decreases when the temperature difference ΔTH is small. I went until. Such a decrease in the valve opening speed may be terminated when the temperature difference ΔTH is reduced to such an extent that the engine outlet water temperature THW does not fluctuate. That is, the temperature difference ΔTH at which the engine outlet water temperature THW does not fluctuate even when the radiator path 16 is rapidly opened is set as the specified value X, and the temperature difference when the temperature difference ΔTH at the start of opening of the electronic thermostat 21 is large is set. The valve opening speed may be decreased when the difference ΔTH is small until the temperature difference ΔTH becomes equal to or less than the specified value X after the valve opening is started.

  In the above embodiment, when the temperature difference ΔTH at the start of valve opening of the electronic thermostat 21 is large, the amount of decrease in the valve opening speed relative to when the temperature difference ΔTH is small is used to reduce the temperature difference ΔTH after the valve opening is started. It was made smaller accordingly. If there is no problem in the responsiveness of the cooling water temperature control, the above-described reduction rate of the valve opening speed set at the start of the valve opening may be maintained as it is regardless of the decrease in the temperature difference ΔTH after the valve opening is started. In this case, the value of the temperature difference counter DT is held at the value at the start of valve opening even after the electronic thermostat 21 starts to open, and is reset to “0” when the forced valve opening condition is not satisfied. It will be.

  In the embodiment described above, the energization of the heater 25 is periodically turned on / off, and the ratio of the energization on time within the same period to the on / off period of the energization is changed, thereby opening the electronic thermostat 21. The speed was changing. The valve opening speed of the electronic thermostat 21 can be changed by other methods such as adjustment of the supply voltage of the heater 25, and the valve opening speed of the electronic thermostat 21 may be changed by such a method. .

  In the above embodiment, the electronic thermostat 21 is employed as an opening / closing valve for opening / closing the radiator path 16. However, the radiator path 16 may be formed by using another opening / closing valve such as an electromagnetically driven valve or a step motor driven valve. May be opened and closed.

  DESCRIPTION OF SYMBOLS 10 ... Cylinder block (engine), 11 ... Cylinder head (engine), 12 ... Water jacket, 13 ... Cooling water path, 14 ... Water pump, 15 ... Water temperature sensor, 16 ... Radiator path, 17 ... Bypass path, 18 ... Heater path , 19 ... Radiator, 20 ... Heater radiator, 21 ... Electronic thermostat, 22 ... Valve body, 23 ... Spring, 24 ... Thermo wax unit, 25 ... Heater, 26 ... Electronic control unit, 27 ... Crank angle sensor, 28 ... Accelerator pedal Sensor, 29 ... outside air temperature sensor, 30 ... vehicle speed sensor.

Claims (6)

As a path for returning the cooling water that has passed through the engine to the engine, a radiator path for returning the cooling water via a radiator and a bypass path for returning the cooling water without passing through the radiator are provided. And an on-off valve that shuts off the flow of the cooling water through the radiator path when the valve is closed and allows the cooling water when the valve is opened, and defines an engine outlet temperature that is a temperature of the cooling water that has passed through the engine. In the engine cooling device that opens the on-off valve when the valve opening temperature is higher than
When the difference between the water temperature in the radiator, which is the temperature of the cooling water inside the radiator, and the engine outlet water temperature is large at the start of the opening of the valve, the same opening / closing valve is used compared to when the temperature difference is small. The valve opening speed is reduced,
An engine cooling device characterized by that. When the temperature difference at the start of opening of the on-off valve is large, the valve opening speed is decreased with respect to when the temperature difference is small until the temperature difference becomes a specified value or less.
The engine cooling device according to claim 1. When the temperature difference at the start of opening of the on-off valve is large, the range of decrease in the valve opening speed relative to when the temperature difference is small is the reduction of the temperature difference after the opening of the on-off valve is started. Reduced according to
The engine cooling device according to claim 1 or 2, wherein The temperature difference is obtained by estimation based on the elapsed time from the previous opening of the on-off valve, the outside air temperature, and the vehicle speed.
The engine cooling apparatus according to any one of claims 1 to 3, wherein the engine cooling apparatus is provided. The on-off valve is an electronic thermostat equipped with a heater for forcibly heating the thermo wax.
The engine cooling device according to any one of claims 1 to 4, wherein the engine cooling device is provided. The energization control of the heater is performed by periodically turning on and off the energization,
In the energization control, when the period from when the energization of the heater is turned on to when the energization that is once turned off is turned on again is defined as an energization cycle, By changing the ratio of the period during which energization is turned on, the valve opening speed of the electronic thermostat is changed,
The engine cooling device according to claim 5, wherein