JP2019027388A - Abnormality detection device of thermostat - Google Patents

Abstract

To detect abnormality caused by fastening of a thermostat, differently from abnormality of a radiator.SOLUTION: An abnormality detection device is applied to a thermostat disposed in a cooling system of a vehicle. A refrigerant passage of the cooling system includes first to third passages. The first passage passes a radiator, and the second passages bypasses the radiator. The third passage passes a heat exchanger, and connects an inlet-side merging portion and an outlet-side merging portion of the first passage and the second passage. The thermostat is disposed on the outlet-side merging portion of the first and second passages, adjusts a flow rate ratio of a refrigerant from the first passage and a refrigerant from the second passage, and allows the refrigerant to flow out to the third passage. The abnormality detection device reduces the flow rate of the refrigerant circulated in the third passage in comparison with that in a normal operation, during a fuel cut operation of an engine, determines whether the thermostat generates hunting or not when the flow rate of the refrigerant is reduced, and determines the existence of abnormality in the thermostat when it determines that the hunting is not generated.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an abnormality detection device for a thermostat arranged in a cooling system of a vehicle.

  For example, a configuration of an engine cooling system is known in which a thermostat that automatically opens and closes according to a cooling water temperature is installed in a cooling water passage between a cooling water passage in an engine and a radiator. In such an engine cooling system, the thermostat closes the cooling water passage through the radiator and stops the flow of cooling water into the radiator until the warm-up of the engine is completed. Thereby, the cooling water can be quickly raised to an appropriate temperature range. When the cooling water reaches an appropriate temperature range, the thermostat is automatically opened, and the cooling water is introduced into the radiator and adjusted to an appropriate temperature.

  However, in such an engine cooling system, when an open failure occurs that adheres to the thermostat on the open side, the temperature rise of the cooling water at the start of the engine is hindered, and the engine warm-up may be delayed. On the other hand, when a closed failure that adheres to the thermostat occurs on the thermostat, the cooling water temperature rises excessively because the cooling water is not circulated to the radiator side even after the engine cooling water exceeds the appropriate temperature. The engine may overheat.

  As a countermeasure, for example, Patent Document 1 discloses a thermostat abnormality detection method. For example, when the thermostat has an open failure, the cooling water temperature exhibits a behavior different from that in a normal state in a temperature range that is closed if the thermostat is normal. Therefore, in patent document 1, the open failure of a thermostat is detected by comparing the cooling water temperature detected by the refrigerant temperature sensor in this temperature region with the behavior of the cooling water temperature when the thermostat is normal in this temperature region. Further, when the thermostat is closed, the cooling water temperature exhibits a behavior different from the normal behavior in a temperature range that is open if the thermostat is normal. Therefore, in patent document 1, the closed failure of a thermostat is detected by comparing the cooling water temperature detected in this temperature range with the behavior of the cooling water temperature in the temperature range when the thermostat is normal.

Japanese Patent Laid-Open No. 10-184433 JP 11-148420 A

  In the method of detecting an abnormality based on the comparison between the detected value of the engine cooling water temperature and the behavior of the cooling water temperature at normal time as in Patent Document 1, the abnormality of the cooling water temperature is due to the abnormality of the radiator, It cannot be determined whether it is due to an abnormality in the thermostat.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an improved abnormality detecting device for a thermostat that can detect an abnormality caused by the fixing of a thermostat separately from an abnormality of a radiator.

  In order to achieve the above object, the present invention is an abnormality detection device for a thermostat, and is applied to a thermostat arranged in a refrigerant passage of a cooling system of a vehicle. The cooling system includes a radiator, a heat exchanger, and a refrigerant passage that circulates a refrigerant through the radiator and the heat exchanger. The refrigerant passage includes a first passage, a second passage, and a third passage. The first passage is a refrigerant passage through the radiator. The second passage is a refrigerant passage that is arranged in parallel to the first passage and bypasses the radiator. A 3rd channel | path is a channel | path of a refrigerant | coolant which goes through via a heat exchanger, Comprising: It is a channel | path which connects the confluence | merging part by the side of the entrance of a 1st channel | path and a 2nd channel | path, and the confluence | merging part by the side of an exit.

  The thermostat is installed at the junction on the outlet side of the first passage and the second passage, and adjusts the flow rate ratio between the flow rate of the refrigerant flowing from the first passage and the flow rate of the refrigerant flowing from the second passage, The refrigerant is allowed to flow into the third passage.

  The abnormality detection device determines whether or not the thermostat hunts when the refrigerant flow rate is decreased by reducing the flow rate of the refrigerant flowing through the third passage during the fuel cut operation of the engine, compared to during normal operation. However, when it is determined that the thermostat is not hunting, the thermostat is determined to be abnormal.

  When the flow rate of the refrigerant is decreased, hunting is performed if the thermostat is normal, but the thermostat is not hunted if it is fixed. According to the present invention, the presence or absence of a thermostat abnormality is determined based on the presence or absence of thermostat hunting when the refrigerant flow rate is decreased. Therefore, it is possible to reliably detect the abnormality of the thermostat in distinction from the abnormality of the radiator.

It is a figure which shows typically the structure of the cooling system of embodiment of this invention. It is a figure for demonstrating the fluctuation | variation of the flow rate ratio of the cooling water which flows out from a normal thermostat when the flow rate of cooling water is decreased. It is a flowchart for demonstrating the control in embodiment of this invention. It is a figure for demonstrating the detection method of the amplitude of the temperature change of the cooling water in control of embodiment of this invention. It is a figure for demonstrating the detection method of the amplitude of the temperature change of the cooling water in control of embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof is simplified or omitted.

  FIG. 1 is a diagram schematically showing a configuration of a cooling system in an embodiment of the present invention. The cooling system shown in FIG. 1 is mounted on a vehicle and functions as an engine cooling system, for example. The cooling system of FIG. 1 includes a refrigerant passage configured by a first passage C1, a second passage C2, and a third passage C3. Cooling water as a refrigerant circulates in the refrigerant passage. However, the refrigerant is not limited to water.

  The refrigerant passage branches into a first passage C1 and a second passage C2 at the outlet side end portion of the third passage C3, and enters the third passage C3 at the outlet side end portions of the first passage C1 and the second passage C2. It is configured to merge. In other words, the inlet-side joining portion of the first passage C1 and the second passage C2 and the outlet-side joining portion are connected by the third passage C3.

  The first passage C <b> 1 passes through the radiator 10. The radiator 10 is a radiator for an engine, for example. The second passage C <b> 2 is a passage that is installed in parallel with the first passage C <b> 1 and bypasses the radiator 10.

  A water pump (hereinafter also referred to as “W / P”) 12 is installed in the third passage C3. The third passage C <b> 3 is a passage through the heat exchanger 14. In FIG. 1, the flow of gas cooled by heat exchange with the refrigerant in the heat exchanger 14 is indicated by broken lines.

  A thermostat 20 is installed at the junction of the first passage C1 and the second passage C2 to the third passage C3. The thermostat 20 has a valve body 22 therein. The valve body 22 is in the valve closing position until the cooling water temperature at the junction reaches a predetermined temperature, and closes the first passage C1 side. In other words, until the cooling water temperature reaches a predetermined temperature, the circulation of the cooling water to the radiator 10 side is stopped, thereby warming up early. On the other hand, after the temperature of the cooling water reaches a predetermined temperature, the valve body 22 opens the first passage C1 side to an opening degree corresponding to the temperature. Thereby, the flow rate ratio between the flow rate of the cooling water diverted to the radiator 10 side and the flow rate of the cooling water diverted to the second passage C2 is adjusted according to the cooling water temperature. As a result, the cooling water whose temperature is adjusted flows out into the third passage C3.

  A plurality of sensors are arranged in the cooling system of FIG. For example, the refrigerant temperature sensor 30 is installed in the third passage C3. The refrigerant temperature sensor 30 detects the temperature of the cooling water flowing through the third passage C3 and transmits the detection signal to the control device 40. In addition, a gas temperature sensor 32 and a supercharging pressure sensor 34 are installed in the gas passage of the engine, and the gas temperature and the supercharging pressure are detected, respectively, and the detection signals are transmitted to the control device. .

  The cooling system in FIG. 1 includes a control device 40. The control device 40 is an ECU (Electronic Control Unit) and has at least an input / output interface, a ROM, a RAM, and a CPU. The input / output interface takes in sensor signals from various sensors attached to the engine and the vehicle, including the refrigerant temperature sensor 30, the gas temperature sensor 32, and the supercharging pressure sensor 34, and outputs an operation signal to an actuator provided in the engine. To be provided. Various control data including various control programs and maps for controlling the engine are stored in the ROM. The CPU reads and executes the control program from the ROM, and generates an operation signal based on the acquired sensor signal.

  In the present embodiment, the control device 40 functions as an abnormality detection device for the thermostat 20 that detects a closed failure in which the thermostat 20 is fixed on the valve closing side and an open failure in which the thermostat 20 is fixed on the valve opening side. Hereinafter, control for realizing the function of the thermostat 20 included in the control device 40 as an abnormality detection device will be described.

  FIG. 2 is a diagram for explaining fluctuations in the flow rate ratio of the cooling water flowing through the normal thermostat 20 when the flow rate of the cooling water is decreased. When the flow rate of the cooling water flowing through the refrigerant passage is reduced and the flow rate of the cooling water is reduced, if the thermostat 20 is normal, hunting that repeatedly opens and closes the valve body 22 occurs. Therefore, as shown in FIG. 2, the flow rate ratio of the cooling water repeatedly fluctuates in a short cycle. On the other hand, when the thermostat 20 has a closed failure or an open failure, the thermostat 20 does not hunt, and therefore the flow rate ratio does not change.

  Therefore, in the present embodiment, the presence or absence of hunting of the thermostat 20 when the flow rate of the cooling water is decreased is detected to detect an abnormality in the open or closed failure of the thermostat 20. The abnormality detection control of the thermostat 20 is executed at a timing during the fuel cut operation that does not require the cooling water temperature control because it is necessary to temporarily reduce the flow rate of the cooling water and to reduce it compared to the normal operation. .

  The presence or absence of hunting of the thermostat 20 is determined based on the temperature change of the cooling water flowing out from the thermostat 20. Here, as shown in FIG. 2, when hunting occurs in the thermostat 20, the cooling water from the first passage C <b> 1 side that has passed through the radiator 10 and the cooling from the second passage C <b> 2 side that bypasses the radiator 10 are performed. The flow ratio with water fluctuates in a short cycle. Therefore, the cooling water temperature downstream of the thermostat 20 also varies greatly in a short cycle. Therefore, a change in the cooling water temperature downstream of the thermostat 20 is detected by the refrigerant temperature sensor 30, and an amplitude of the detected change in the cooling water temperature is calculated. The calculated amplitude is compared with the reference value, and if the amplitude is smaller than the reference value, it is determined that the thermostat 20 is not hunted, and if it is equal to or greater than the reference value, it is determined that hunting is present.

  FIG. 3 is a flowchart for illustrating a control routine executed by control device 40 in the present embodiment. The routine of FIG. 3 is repeatedly executed at predetermined intervals while the engine is operating. In this routine, first, in step S102, it is determined whether or not the engine is currently in a fuel cut operation. If it is determined that the fuel cut operation is not being performed, the current process is temporarily terminated.

  If it is determined in step S102 that the fuel cut operation is being performed, the process proceeds to step S104, where the W / P command duty ratio is reduced. The W / P command duty ratio is a control command value for the driving power of W / P12. By reducing the W / P command duty ratio, the flow rate of cooling water flowing through the refrigerant passage is the flow rate during normal operation. Decrease more.

  Next, it progresses to step S106, the data of the outlet temperature of the thermostat 20 are acquired, and the amplitude of a cooling water temperature change is calculated. Data on the outlet temperature of the thermostat 20 is acquired by the refrigerant temperature sensor 30.

  4 and 5 are diagrams for explaining a method of calculating the amplitude of the change in cooling water temperature. As shown in FIG. 4, the period in which exMX is 1 is a period in which the cooling water temperature is rising, and the maximum cooling water temperature MXfnl_i is acquired during this period.

  FIG. 5 shows an example of a more specific amplitude calculation program. As shown in FIG. 5, when exMX is 1, it is determined whether or not the state quantity_n, which is the detected value of the cooling water temperature this time (that is, n times), is larger than the currently stored maximum value MX_n. If it is larger, the maximum value MX_n is updated to the state quantity_n, and the process returns. On the other hand, when the state quantity_n is equal to or lower than the stored maximum value MX_n, the maximum cooling water temperature MXfnl_i is set to the maximum value MX_n. Thereafter, exMX is set to 0, and acquisition of the maximum cooling water temperature MXfnl_i this time (that is, i times) ends.

  As shown in FIG. 4, the period in which exMX is 0 is a period in which the cooling water temperature is decreasing, and the minimum cooling water temperature MNfnl_i is acquired during this period. More specifically, as shown in FIG. 5, when exMN is 0, the state quantity_n that is the detected value of the cooling water temperature this time (that is, n times) is smaller than the currently stored minimum value MN_n. If it is smaller, the minimum value MN_n is updated to the state quantity_n, and the process is returned. On the other hand, when the state quantity_n is equal to or greater than the stored minimum value MN_n, the minimum cooling water temperature MNfnl_i is set to the minimum value MN_n. After that, exMX is set to 1, and acquisition of the minimum cooling water temperature MNfnl_i this time (that is, i times) ends. Thereafter, the value of the temperature difference between the maximum cooling water temperature MXfnl_i and the minimum cooling water temperature MNfnl_i is calculated as the current amplitude (i.e., i times).

  Note that the above-described calculation of the amplitude is repeatedly executed for the acquired data for a certain period of change in the outlet temperature of the thermostat 20, and the entire amplitude in the data for the certain period is calculated.

  Next, it progresses to step S108 and a determination counter is calculated. The determination counter is a counter that counts the number of times that an amplitude smaller than the reference value is calculated in step S106. That is, in step S108, the determination counter is calculated by adding the number of amplitudes where amplitude <reference value among all the amplitudes calculated in step S106 to the current value of the determination counter. The reference value here is a determination value set in advance based on a temperature difference that can occur even when the thermostat 20 is not hunting, or data on a temperature difference that occurs when hunting occurs.

  Next, the process proceeds to step S110, where it is determined whether or not the determination counter calculated in step S108 is greater than the reference number. The reference number is a number that is set as appropriate in consideration of necessary determination accuracy and the like.

  If it is determined in step S110 that the determination counter is larger than the reference number, the process proceeds to step S112, where it is determined that the thermostat 20 is firmly fixed, and the current process is temporarily terminated.

  On the other hand, if it is determined in step S110 that the determination counter is equal to or smaller than the reference number, the process proceeds to step S114, where it is determined whether or not the accumulated time exceeds the reference time. If it is determined in step S114 that the reference time has not been exceeded, the process ends as it is.

  On the other hand, if it is determined in step S114 that the integration time exceeds the reference time, the determination counter is set to 0 in step S116, and after the integration time is set to 0 in step S118, the current process ends. To do.

  As described above, according to the present embodiment, when the circulation of the cooling water to the thermostat 20 is reduced, the abnormality determination of the thermostat 20 is performed based on whether or not the thermostat 20 causes hunting. . Therefore, the abnormality determination can be performed based on the behavior of the cooling water temperature change caused only by the fixing of the thermostat 20, so that the abnormality of the thermostat 20 is distinguished from the abnormality of the radiator 10, and the abnormality of the thermostat 20 is reliably detected. be able to.

  In the flowchart of FIG. 3, the number of times that an amplitude smaller than a reference value is calculated from the coolant temperature data near the outlet of the thermostat 20 when the coolant flow rate is reduced is counted, and the count value is a value within the reference time. Only when the number of times becomes the reference number or more, it is determined that the amplitude of the cooling water temperature is below the reference value and that hunting is not occurring. This is to ensure high determination accuracy, but the determination method of whether or not the amplitude of the coolant temperature change is smaller than the reference value is not limited to this. For example, the average value of the amplitude for a certain period is smaller than the reference value. Accordingly, other configurations such as a configuration in which the amplitude of the cooling water temperature change is recognized to be smaller than the reference value may be used.

  Further, in the present embodiment, the case has been described in which the presence or absence of hunting of the thermostat 20 is determined based on the amplitude of the change in the coolant temperature near the outlet of the thermostat 20. However, in the present invention, the determination of the presence or absence of hunting of the thermostat 20 is not limited to the determination based on the amplitude of the change in the coolant temperature, and may be performed using, for example, the cycle of the coolant temperature change. In this case, it can be determined that there is no hunting, that is, the thermostat 20 is stuck, because the cycle of the cooling water temperature change is larger than the reference value.

  Further, the influence of hunting of the thermostat 20 appears not only in the temperature of the refrigerant but also in the supercharging pressure or the like due to the outlet temperature of the heat exchanger 14 to be cooled by the refrigerant and the change in the outlet temperature of the heat exchanger 14. . Therefore, for example, hunting of the thermostat 20 may be detected based on the amplitude or cycle of the temperature change at the outlet of the heat exchanger 14 and the amplitude or cycle of the supercharging pressure fluctuation. More specifically, it can be configured that it is determined that there is no hunting, that is, the thermostat 20 is stuck, when these amplitudes are smaller than the reference value or the period is larger than the reference value.

  Similarly, hunting of the thermostat 20 may be detected by a change in the rotational speed of the W / P 12. That is, when the refrigerant temperature changes due to hunting, the viscosity of the refrigerant changes, and the rotation speed of the W / P 12 changes accordingly. Therefore, hunting of the thermostat 20 can be detected based on the amplitude (that is, the rotational speed difference) or the period of the change in the rotational speed of the W / P 12. More specifically, it is determined that there is no hunting, that is, the thermostat 20 is stuck, because the amplitude of the rotation speed change of the W / P 12 is smaller than the reference value or the rotation speed change period is larger than the reference value. can do.

  In the above embodiment, when referring to the number of each element, quantity, quantity, range, etc., the reference is made unless otherwise specified or the number is clearly specified in principle. The invention is not limited to the numbers. Further, the structure and the like described in this embodiment are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle.

10 Radiator 12 W / P
DESCRIPTION OF SYMBOLS 14 Heat exchanger 20 Thermostat 22 Valve body 30 Refrigerant temperature sensor 32 Gas temperature sensor 34 Supercharging pressure sensor 40 Control apparatus C1 1st channel | path C2 2nd channel | path C3 3rd channel | path

Claims (1)

With radiator,
A heat exchanger,
A refrigerant passage for circulating refrigerant through the radiator and the heat exchanger;
A thermostat abnormality detecting device disposed in the refrigerant passage of a vehicle cooling system comprising:
The refrigerant passage is
A first passage which is a passage of a refrigerant passing through the radiator;
A second passage that is arranged in parallel with the first passage and is a refrigerant passage that bypasses the radiator;
A refrigerant passage passing through the heat exchanger, the third passage connecting the merging portion on the inlet side and the merging portion on the outlet side of the first passage and the second passage;
With
The thermostat is installed at a confluence portion on the outlet side of the first passage and the second passage, and a flow rate ratio between a flow rate of the refrigerant flowing from the first passage and a flow rate of the refrigerant flowing from the second passage. To adjust the flow of the refrigerant to the third passage,
The abnormality detection device is:
During the fuel cut operation of the engine, the flow rate of the refrigerant flowing through the third passage is decreased from that during normal operation,
Determining whether or not the thermostat hunts when the flow rate of the refrigerant is reduced;
When it is determined that the thermostat is not hunting, it is determined that the thermostat is abnormal.
A thermostat abnormality detection device configured as described above.

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