Engine cooling system abnormality detection device

Abstract

To provide an abnormality detection device for an engine cooling system, which can accurately determine whether the cooling system is normal or abnormal.SOLUTION: An engine cooling system is configured to circulate cooling water between an engine water jacket and a radiator and to circulate the cooling water while making the same bypass the radiator by means of a flow passage selector valve. An abnormality detection device for the engine cooling system comprises a first water temperature sensor that detects a first temperature of the cooling water at the outlet of the water jacket, a second water temperature sensor that is provided between the flow passage selector valve and the inlet of the radiator and detects a second temperature of the cooling water, and a controller that determines an abnormality in the cooling system on the basis of a temperature difference between the first temperature and the second temperature. The controller prohibits determination of an abnormality in the cooling system based on the temperature difference for a predetermined period of time, when detects a state in which the first temperature of the cooling water in the water jacket does not rise to a temperature at which the cooling water is to be radiated and cooled in the radiator.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a cooling system having a flow path switching valve provided in a coolant circuit of an internal combustion engine, and more particularly to an abnormality detection device for the cooling system that can determine an abnormality in the cooling system. [Background technology]

[0002] A conventional cooling system has a coolant circuit between an engine and a radiator, and coolant introduced into the coolant circuit is circulated by a water pump to cool the coolant heated by the engine by dissipating heat in the radiator. The coolant circuit also has a radiator flow path that passes through the radiator, as well as a bypass flow path that diverts the coolant away from the radiator. A flow path switching valve is provided at the branch point between the radiator flow path and the bypass flow path, and when the coolant temperature reaches a predetermined warm-up temperature, the flow path switching valve switches from the bypass flow path to the radiator flow path.

[0003] A control device for an engine cooling system having a cooling device with the above-described configuration is described in Patent Document 1. The cooling device of the control device for an engine cooling system described in Patent Document 1 is a control device that, since the pressure of the cooling water increases as the engine speed increases, when the engine speed increases or is expected to increase, switches an electronically controlled branch valve provided between the engine and the radiator to pass water through the radiator and reduce the pressure in the cooling water circuit. According to the invention of Patent Document 1, by appropriately controlling the opening of the branch valve according to the engine speed, it is possible to suppress an increase in the water pressure of the cooling water.

[0004] In the cooling device described in Patent Document 1, if a flow path switching valve such as a branch valve malfunctions, for example by failing to open or close, the coolant may pass through the radiator flow path even during warm-up operation, making it difficult for the coolant temperature to increase. Conversely, the coolant may pass through the bypass flow path even during cooling operation, restricting cooling by the radiator and making it difficult for the coolant temperature to decrease, which may impede engine cooling.

[0005] An example of a coolant circuit diagnostic device that addresses this issue is described in Patent Document 2. In the diagnostic device described in Patent Document 2, a flow path switching valve such as a thermostat switches between a radiator flow path and a bypass flow path, and water temperature sensors are provided in the radiator flow path, before and after the flow path switching valve. The diagnostic device calculates the rate of change in temperature difference between the water temperature sensors before and after the flow path switching valve over a predetermined period of time, and if the rate of change in temperature difference from when the engine starts until the coolant temperature reaches the warm-up temperature is equal to or greater than a predetermined threshold, it determines that the flow path switching valve is functioning normally. Conversely, if the rate of change in temperature difference is less than the predetermined threshold, it determines that the flow path switching valve is malfunctioning. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-234605 [Patent Document 2] Japanese Patent Publication No. 2020-122474 Summary of the Invention [Problem to be solved by the invention]

[0007] As described in the above patent documents, by installing water temperature sensors before and after the flow path switching valve, or near the radiator and near the engine, it is possible to determine whether the function of the cooling water circuit is abnormal from the water temperature difference.

[0008] On the other hand, in addition to switching the flow path of the coolant circuit, another means for improving warm-up efficiency is to use a grille shutter installed behind the wind inlet of the front grille, etc. When the grille shutter is closed, the wind from the vehicle is blocked, which suppresses cooling of the radiator and coolant circuit by the wind from the vehicle, thereby improving warm-up efficiency.

[0009] However, in a vehicle equipped with a grille shutter, when determining whether the cooling system is functioning normally based on the difference in water temperature detected by multiple water temperature sensors, while closing the grille shutter can promote warm-up, the temperature difference between the water temperature sensors becomes small, and in such a case, the cooling system may be determined to be abnormal even when it is functioning normally.In particular, if, in addition to the control described in Patent Document 1 to prevent a rise in water pressure in the cooling water circuit, control is performed intentionally to drive the water pump and forcibly circulate the cooling water, for example, to remove foreign matter from the cooling water circuit, the temperature difference between the water temperature sensors becomes small, and the cooling system may be determined to be abnormal even when it is functioning normally.

[0010] This invention has been made with an eye on the above-mentioned technical problems, and aims to provide an abnormality detection device for an engine cooling system that can accurately determine whether the cooling system is normal or abnormal. [Means for solving the problem]

[0011] In order to achieve the above object, the present invention provides an abnormality detection device for an engine cooling system configured to circulate coolant between a water jacket and a radiator of an engine and to circulate the coolant by bypassing the radiator using a flow path switching valve, the abnormality detection device comprising: a first water temperature sensor that detects a first temperature of the coolant at an outlet of the water jacket; a second water temperature sensor that is provided between the flow path switching valve and the inlet of the radiator and detects a second temperature of the coolant; and a controller that determines an abnormality in the flow path switching valve based on a temperature difference between the first temperature and the second temperature, the controller detecting a state in which the first temperature of the coolant in the water jacket has not risen to a temperature at which the coolant should be cooled by heat dissipation in the radiator, and determining an abnormality in the flow path switching valve based on a state in which the first temperature of the coolant has risen to a temperature at which the coolant should be cooled by heat dissipation in the radiator. The first condition is that the temperature difference is small and the temperature is not changed. Completion of forced flow of the cooling water into the radiator The second condition is that the water supply is completed after the first condition and the second condition are both met. The present invention is characterized in that, for a predetermined time, determination of an abnormality in the flow path switching valve based on the temperature difference is prohibited. [Effects of the Invention]

[0012] According to the engine cooling system abnormality detection device of the present invention, , radiator A state in which the cooling water should be circulated by bypassing the cooling water is detected as a low cooling water temperature. In this case, for a predetermined time after the detection, determination of an abnormality in the cooling device based on the temperature difference between the first temperature and the second temperature is prohibited. Therefore, the low cooling water temperature to the radiator In the state where the cooling water is not flowing, even if the flow path switching valve is switched for a purpose other than cooling, such as removing foreign matter, and the temperature difference becomes similar to the temperature difference in the abnormal state, the determination of an abnormality is prevented from occurring because the determination of an abnormality is prohibited. Also, even if the temperature of the cooling water rises, the prohibition of the determination is not immediately lifted, but the prohibition of the determination is maintained for a predetermined time. to the radiatorEven after the product begins to circulate, the temperature difference may not accurately represent the temperature difference at the locations where each sensor is installed for a certain period of time due to factors such as heat capacity, so erroneous judgments based on such errors can be avoided. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram for explaining the configuration of an embodiment of the present invention. [Figure 2] 4 is a flowchart illustrating an example of control executed in the embodiment of the present invention. [Figure 3] 3 is a flowchart illustrating an example of a precondition in the control example of FIG. 2. [Figure 4] 3 is a flowchart illustrating an example of a pre-calculation condition for a count value in the control example of FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0014] A cooling device according to an embodiment of the present invention will be specifically described with reference to the drawings. Note that the embodiment described below is merely an example of how the present invention can be implemented, and is not intended to limit the present invention.

[0015] FIG. 1 is a schematic diagram for explaining the configuration of an embodiment of the present invention. An internal combustion engine (hereinafter referred to as engine) 1 is, as an example, a gasoline engine that outputs power by burning a mixture of gasoline and air.

[0016] The engine 1 includes a cylinder block 3 in which cylinders 2 are formed. A water jacket 4 is provided within the cylinder block 3 and around the cylinders 2, and cooling water is poured into this water jacket 4.

[0017] The radiator 5 and the water jacket 4 are connected by a coolant circuit 6. The coolant circuit 6 is configured as a circulation circuit in which the water jacket 4, an upstream flow path 7, a radiator flow path 8, a bypass flow path 9, and a downstream flow path 10 are mainly connected to each other.

[0018] The upstream flow path 7 is a flow path extending from the outlet of the water jacket 4 to an upstream branching portion 11 that branches into a radiator flow path 8 and a bypass flow path 9.

[0019] The radiator flow path 8 is a flow path that extends from an upstream branch point 11 through the radiator 5 to a downstream branch point 12 where the cooling water flows and joins with the bypass flow path 9. The cooling water flowing through the radiator flow path 8 is cooled by heat exchange with the outside air while passing through the inside of the radiator 5, and then flows into the downstream flow path 10.

[0020] The bypass flow path 9 connects the upstream flow path 7 and the downstream flow path 10, and is a flow path that diverts the cooling water from the radiator 5.

[0021] The downstream flow path 10 is a flow path from the downstream branch portion 12 to the inlet portion of the water jacket 4, and a water pump 13 that is driven by the power of the engine 1 to pump the cooling water is provided in the downstream flow path 10. Note that the water pump 13 may be a pump that is driven by a power other than that of the engine 1.

[0022] The cooling water pumped by the water pump 13 flows into the water jacket 4 and cools the cylinder 2. The upstream branch section 11 is provided with a flow path switching valve 14 that switches the flow path for the cooling water between the radiator flow path 8 and the bypass flow path 9.

[0023] The flow path switching valve 14 may be a three-way valve such as a conventionally known electronic control valve or thermostat, and can selectively switch the coolant from the upstream flow path 7 to one of the radiator flow path 8 and the bypass flow path 9. For example, during warm-up operation, the coolant is selected to flow through the bypass flow path 9 to avoid cooling the coolant by the radiator 5. Conversely, when the temperature of the coolant becomes high and it is determined that cooling is necessary, the coolant is selected to flow through the radiator flow path 8.

[0024] In addition, the flow path switching valve 14 may be a multi-function valve that allows cooling water to flow into both the radiator flow path 8 and the bypass flow path 9 simultaneously when the pressure in the cooling water circuit 6 is released due to an increase in pressure, or that can appropriately adjust the ratio of the flow rates of the radiator flow path 8 and the bypass flow path 9 by changing the angle of a ball valve portion (not shown) built into the flow path switching valve 14.

[0025] A first water temperature sensor 15 that detects the temperature T1 of the cooling water (hereinafter referred to as the first temperature) is provided in the upstream flow path 7 near the outlet of the water jacket 4. Therefore, the first water temperature sensor 15 detects the temperature of the cooling water immediately after it flows out of the water jacket 4 (i.e., essentially the engine temperature).

[0026] A second water temperature sensor 16 that detects the temperature T2 of the cooling water (hereinafter referred to as the second temperature) is provided in the radiator flow path 8 near the inlet of the radiator 5, and the second water temperature sensor 16 detects the temperature of the cooling water before it is cooled by the radiator 5. Therefore, the second water temperature sensor 16 can be used to determine whether or not the cooling water is flowing into the radiator 5.

[0027] Furthermore, there is provided an electronic control unit (hereinafter referred to as ECU) 17 that controls the engine 1. The ECU 17 corresponds to a controller in the embodiment of the present invention, and is mainly configured with a microcomputer including an arithmetic unit and a memory, and is configured to perform calculations using data input from various sensors and pre-stored data, and to output the results of the calculations as control command signals.

[0028] The ECU 17 shown in FIG. 1 includes at least a temperature determination unit 18, a temperature difference detection unit 19, and an abnormal temperature difference timer counter 20 as functional components.

[0029] The temperature determination unit 18 is a functional component that determines whether the temperature of the coolant has risen to a temperature at which it can be cooled by the radiator 5, and makes this determination by comparing the first temperature T1 with a predetermined threshold value.

[0030] The temperature difference detection unit 19 has the function of detecting the temperature difference ΔT (=T1-T2) between the first water temperature sensor 15 that detects the first temperature T1 of the coolant and the second water temperature sensor 16 that detects the second temperature T2.

[0031] The abnormal temperature difference timer counter 20 is a functional means for counting the duration of the state in which the temperature difference ΔT detected by the temperature difference detection unit 19 remains within a predetermined range (less than the predetermined temperature difference). This abnormal temperature difference timer counter 20 starts counting time when it detects that the temperature difference ΔT remains within the predetermined range (less than the predetermined temperature difference), and when the count value exceeds a predetermined time, it confirms that the temperature difference ΔT is a temperature difference due to an abnormality. If the count value does not reach the predetermined time, i.e., if the temperature difference ΔT increases and exceeds the predetermined range before the predetermined time has elapsed, it is highly likely that the temperature difference is due to a temporary factor or disturbance, and therefore it does not confirm that the temperature difference is due to an abnormality. In this case, the count value is reset.

[0032] As described above, the cooling water circuit 6 is composed of a radiator flow path 8 that circulates between the engine 1 and the radiator 5, and a bypass flow path 9 that bypasses the radiator 5 and circulates.

[0033] Bypass flow road 9 When water flows through the bypass flow path, for example, in a state where the temperature of the cooling water is maintained high by warm-up operation because the engine water temperature has not yet become high, when the flow path switching valve 14 is operated to allow water to flow through the bypass flow path 9, the second temperature T2 detected by the second water temperature sensor 16 provided between the flow path switching valve 14 and the inlet portion of the radiator 5 is lower than the first temperature T1 detected by the first water temperature sensor 15 provided near the outlet portion of the water jacket 4 because the cooling water does not flow (T2 < T1). That is, when water flows through the bypass flow path 9, if the flow path switching valve 14 is operating normally, a temperature difference ΔT between the first temperature T1 and the second temperature T2 occurs. When water flows through the bypass flow path 9, for example, in a state where the temperature of the cooling water is maintained high by warm-up operation because the engine water temperature has not yet become high, when the flow path switching valve 14 is operated to allow water to flow through the bypass flow path 9, the second temperature T2 detected by the second water temperature sensor 16 provided between the flow path switching valve 14 and the inlet portion of the radiator 5 is lower than the first temperature T1 detected by the first water temperature sensor 15 provided near the outlet portion of the water jacket 4 because the cooling water does not flow (T2 < T1). That is, when water flows through the bypass flow path 9, if the flow path switching valve 14 is operating normally, a temperature difference ΔT between the first temperature T1 and the second temperature T2 occurs.

[0034] On the other hand, when water flows through the bypass flow path 9 and an abnormality occurs in the flow path switching valve 14, the cooling water also flows through the radiator flow path 8, and the second temperature T2 near the inlet portion of the radiator 5 becomes the same temperature as or close to the first temperature T1 near the outlet portion of the water jacket 4 (T2 ≒ T1).

[0035] Normally, the water pump 13 is intentionally driven to perform forced circulation control in order to prevent a rise in water pressure in the coolant circuit 6 or to remove foreign matter from the coolant circuit 6. Specifically, the flow path switching valve 14 is opened to forcibly circulate the coolant through the radiator flow path 8, or to simultaneously circulate the coolant through the radiator flow path 8 and the bypass flow path 9. This control prevents a rise in water pressure (excessive rise in pressure) by releasing pressure in the radiator 5, or enables forced circulation to remove foreign matter.

[0036] However, when determining whether the function of the coolant circuit 6 is abnormal from the temperature difference ΔT between the first temperature T1 and the second temperature T2, the temperature difference ΔT between the first temperature T1 and the second temperature T2 may be small, and the coolant circuit 6 may be determined to be abnormal even if it is functioning normally.

[0037] In order to prevent such an erroneous determination of an abnormality in the coolant circuit 6, the cooling device in the embodiment of the present invention described above is configured to execute the control described below.

[0038] Figures 2 to 4 are flowcharts for explaining an example of this control, which is repeatedly executed by the ECU 17 while the engine 1 is operating. The control shown in the flowchart in Figure 2 is an example of coolant circuit function determination control that determines whether the function of the coolant circuit 6 is normal or abnormal, and this coolant circuit function determination control will first be described in detail with reference to the flowchart. Figures 3 and 4, which will be described later, show the application of the present invention to the coolant circuit function determination control of Figure 2.

[0039] When the engine 1 is running, the water pump 13 is driven in accordance with the rotation speed of the engine 1, and the coolant circulates through the coolant circuit 6. In the example of the coolant circuit function determination control shown in Fig. 2, first, it is determined whether or not preconditions are met when executing the coolant circuit function determination (step S1). These preconditions are verified before executing the coolant circuit function determination, and specific condition items of the preconditions in the embodiment of the present invention will be described later with reference to Fig. 3. If the determination in step S1 is negative, the routine shown in Fig. 2 is temporarily terminated without performing any particular control.

[0040] On the other hand, if the result of step S1 is affirmative (if all the prerequisite conditions are met), a cooling water circuit function determination is performed (steps S2 and S3). Or The control for making the judgment may be performed using a conventionally known method or means. In an example of the coolant circuit function judgment shown in Fig. 2, when the temperature difference ΔT between the first temperature T1 of the coolant near the outlet of the water jacket 4 and the second temperature T2 of the coolant near the inlet of the radiator 5, detected by each of the water temperature sensors 15, 16 of the temperature difference detection unit 19, is equal to or higher than a predetermined temperature, it is judged as normal function, and when it is lower than the predetermined temperature, it is judged as abnormal function, and the respective judgment times are counted.

[0041] In step S3, which counts the abnormality determination time, the count value may be changed by taking into consideration factors other than the behavior time of the temperature difference ΔT. An example of the pre-calculation condition for the count value proposed in the embodiment of the present invention will be specifically described later with reference to FIG.

[0042] In the coolant circuit function determination, if the temperature difference ΔT is equal to or greater than a predetermined temperature, that is, if the coolant circuit is determined to be functioning normally, and the normality determination time is counted in step S2, it is determined whether the normality determination time is equal to or greater than a predetermined value (step S4). If the determination in step S4 is negative, the routine shown in FIG. 2 is temporarily terminated without further determination.

[0043] On the other hand, if the answer to step S4 is affirmative, that is, if the temperature difference ΔT is equal to or greater than the predetermined temperature and the normal judgment time is equal to or greater than the predetermined value in the coolant circuit function judgment, a normal judgment is made in step S5 that "the coolant circuit 6 is operating normally," and this routine is terminated.

[0044] On the other hand, if the temperature difference ΔT is less than the predetermined temperature in the coolant circuit function determination, that is, if the coolant circuit function is abnormal, it is determined whether the time counted in step S3 is equal to or greater than a predetermined value (step S6). If the determination in step S6 is negative, the routine shown in FIG. 2 is temporarily terminated.

[0045] On the other hand, if the answer to step S3 is affirmative, that is, if the temperature difference ΔT is less than the predetermined temperature and the abnormality determination time is equal to or greater than the predetermined value in the cooling water circuit function determination, an abnormality determination is made in step S7, that is, "the cooling water circuit 6 is operating abnormally," and this routine is terminated.

[0046] Next, the preconditions in step S1 of the flowchart shown in Fig. 2 will be described with reference to Fig. 3. In one example of the preconditions shown in Fig. 3, it is first determined whether the first water temperature sensor 15 and the second water temperature sensor 16 are both operating normally (step S101). This determination may be made in the same manner as in the conventional method, and for example, it may be determined based on the detection signal whether a signal is detecting the temperature of the cooling water input to the ECU 17.

[0047] If it is determined in step S101 that both the first water temperature sensor 15 and the second water temperature sensor 16 are operating normally, it is then determined whether a predetermined time has elapsed since the foreign matter removal process for the flow path switching valve 14 was completed (step S102). The foreign matter removal process involves intentionally opening the flow path switching valve 14 by a foreign matter removal processor (not shown) of the ECU 17 or forcibly driving the water pump 13 in order to remove foreign matter such as metal fragments flowing within or around the flow path switching valve 14. In step S102, it is determined whether a predetermined time has elapsed since the foreign matter removal process was completed, and this determination can be made by detecting a process completion signal from the foreign matter removal processor.

[0048] It is also determined whether or not the flow path switching valve 14 has failed (step S103). This is to determine whether or not a failure has occurred due to a broken wire or an electrical factor in the shaft or ball valve built into the flow path switching valve 14, and can be determined, for example, by a signal from a diagnosis unit.

[0049] Furthermore, it is determined whether a predetermined time has elapsed since the end of the forced driving of the water pump 13 (step S104). This forced driving is not limited to the forced driving of the water pump 13 under the control of the foreign matter removal processing unit described in step S102, but is also a control to forcibly drive the water pump 13 to circulate the coolant circuit 6 for reasons such as checking the operation of the cooling system or releasing pressure in the radiator 5. Pressure release in the radiator 5 may be forcibly performed even when the coolant is bypassing the radiator 5 and flowing through the radiator 5 because the coolant temperature at the outlet of the water jacket 4 is low. Therefore, in this case, the temperature difference ΔT between the first temperature T1 and the second temperature T2, which is large in the normal operating state of the cooling system based on the coolant temperature, becomes small. Step In S104 is for determining whether a predetermined time has elapsed since the forced driving of the water pump 13 was completed, and this can be determined by detecting a signal indicating the completion of the forced driving.

[0050] If all of the following determinations are true: the first water temperature sensor 15 and the second water temperature sensor 16 are normal; a predetermined time has elapsed since the completion of the foreign matter removal process; the flow path switching valve 14 is energized; and a predetermined time has elapsed since the end (completion) of the forced drive, the preconditions for the control of the coolant circuit function determination are true. In this case, an instruction to start the control of the coolant circuit function determination is issued (steps S2 and S3). In other words, the forced drive is executed in a state where the coolant temperature at the outlet of the water jacket 4 is low and the coolant should flow bypassing the radiator 5. Therefore, the state in which the forced drive is executed and terminates is when the coolant temperature at the outlet of the water jacket 4 is lower than a predetermined value. Therefore, in step S104, it is determined that the coolant temperature at the outlet of the water jacket 4 has not risen to a temperature at which the radiator 5 should dissipate heat.

[0051] On the other hand, if a negative judgment is made in any of steps S101 to S104, such as when an abnormality is detected in the first water temperature sensor 15 and the second water temperature sensor 16, or when less than a predetermined time has elapsed since the completion of the foreign matter removal process, the routine shown in FIG. 3 is temporarily terminated without any particular control being performed, and the coolant circuit function judgment is not performed.

[0052] The preconditions in the embodiment of the present invention are not limited to the conditions listed in steps S101 to S104, and other conditions may be added or deleted as appropriate, such as determining whether the engine water temperature at start-up is a predetermined value or whether the diagnosis is at or above the operating voltage. The order in which these preconditions are determined is not particularly limited, and they may be determined simultaneously in parallel.

[0053] Next, an example of a pre-calculation condition for the count value in the calculation of the abnormality determination time in step S3 of the flowchart shown in Fig. 2 will be described with reference to Fig. 4. In the example of the pre-calculation condition for the count value shown in Fig. 4, first, it is determined whether a predetermined time has elapsed since the completion of the water injection control to the radiator 5 (step S301).

[0054] The control of water injection into the radiator 5 is performed by intentionally causing the coolant to flow into the radiator flow path 8 when the coolant is flowing through the bypass flow path. For example, a sudden rise in the temperature of the coolant due to an increase in the rotation speed of the engine 1 is detected by the temperature determination unit 18. Specifically, the first temperature T1 of the coolant near the outlet of the water jacket 4 is compared with a predetermined threshold value to determine whether the temperature of the coolant has risen to a temperature at which the coolant can be cooled by the radiator 5. If it is determined that the temperature has risen, a coolant circuit pressure release unit (not shown) of the ECU 17 intentionally opens the flow path switching valve 14 to execute control to prevent an increase in pressure in the coolant circuit 6.

[0055] In step S301, as the pressure in the cooling water circuit 6 increases, the flow path switching valve 14 is opened to start pouring water into the radiator 5, and it is determined whether a predetermined time has passed since the completion of the water pouring. This can be determined by detecting a signal indicating the completion of the water pouring from the cooling water circuit pressure release section.

[0056] If a predetermined time has elapsed since the completion of water injection into the radiator 5, that is, if the result of step S301 is affirmative Target If so, it is determined whether or not the temperature difference ΔT between the first water temperature sensor 15 and the second water temperature sensor 16 is within a predetermined range (step S302). That is, it is determined whether or not the temperature difference ΔT detected by the temperature difference detection unit 19 is within a predetermined range (less than the predetermined temperature difference) after a predetermined time has elapsed since the completion of pouring water into the radiator 5.

[0057] Step S302 is executed by the abnormal temperature difference timer counter 20, and if the answer is affirmative in step S302, i.e., if the temperature difference ΔT is within a predetermined range, it is determined that the temperature difference is abnormal, and the timer counter measures the length of the abnormal temperature difference period (step S303, count up).

[0058] Conversely, if the temperature difference ΔT is not within the predetermined range (greater than the predetermined temperature difference), it is determined to be a normal temperature difference, and the timer counter that measures the length of the abnormal temperature difference period is reset (step 304). The timer counter that measures the length of the abnormal temperature difference period in step S302 described above is executed for a predetermined time.

[0059] If it is within a predetermined time from the completion of water filling of the radiator 5, that is, if the answer is negative in step S301, the measurement of the abnormal temperature difference period is terminated and the timer count value for the abnormal temperature difference period is held (step 305).

[0060] Next, the count values for the abnormal temperature difference period in steps S303 to S305 are integrated so that the count values can be applied to the calculation of the abnormality determination time (step S306). After the count values are applied to the calculation of the abnormality determination time in step S306, the process moves on to determining whether the abnormality determination time for the cooling water circuit function determination is equal to or greater than a predetermined value (FIG. 2, step S6). In other words, the abnormality / normality determination is not made based on a temporary or instantaneous temperature difference, but is made based on a stable temperature difference over a certain period of time.

[0061] In the embodiment of the present invention, the conditions before calculating the count value of the abnormality determination time are not limited to the conditions listed in step S301, and other conditions may be added or deleted as appropriate, such as determining whether there is a warm-up history, determining whether the amount of change in engine water temperature over one second is within a predetermined range, or determining whether the amount of change in the differential value between the first water temperature sensor 15 and the second water temperature sensor 16 over one second is within a predetermined range. Furthermore, the order in which these prerequisite conditions are determined is not particularly limited, and they may be determined simultaneously in parallel.

[0062] In the past, the temperature difference ΔT was likely to decrease when the flow path switching valve 14 was opened in the coolant circuit 6, so even if the flow path switching valve 14 was intentionally opened, an erroneous abnormality was detected, indicating that the flow path switching valve 14 was operating abnormally. However, in this invention, if a predetermined time has passed since the completion of water injection into the radiator 5, the count of the abnormal temperature difference period can be reset and the count value of the abnormality determination time for the subsequent coolant circuit function determination can be lowered, so that an abnormality in the function of the flow path switching valve 14 can be accurately determined.

[0063] In particular, as described above, when a grille shutter is provided behind the front grille and the grille shutter is closed, the temperature difference ΔT between the first water temperature sensor 15 and the second water temperature sensor 16 becomes even smaller, making it easier to make an erroneous determination of the abnormality described above. Therefore, in the preconditions set before the coolant circuit function determination, if the water pump 13 is forcibly driven for a foreign object removal process or the like, the preconditions are not established and the coolant circuit function determination is not made until a predetermined time has elapsed. This prevents an erroneous determination of an abnormality in the coolant circuit 6 from occurring and makes it possible to accurately determine an abnormality in the function of the coolant circuit 6.

[0064] The present invention is not limited to the above-described embodiment, and can be modified as appropriate within the scope of the object of the present invention. For example, there may be a plurality of bypass flow paths 9 that bypass the radiator 5. The flow path switching valve 14 may also be provided in the downstream branch portion 12. In this case, a water temperature sensor may be newly provided to determine whether the coolant circuit 6 is normal or abnormal.

[0065] Furthermore, the control of the present invention is not limited to the configuration of the flowchart described above. For example, the preconditions in step S1 and the conditions before calculating the count value based on the abnormality determination time in step S3 may be determined in parallel. In short, it is sufficient that the flow path switching valve function determination is not performed when the temperature difference ΔT between the first water temperature sensor 15 and the second water temperature sensor 16 is within a predetermined range and intentional forced circulation of the coolant circuit 6 is being performed. [Explanation of symbols]

[0066] 1 engine 2 cylinders 3 Cylinder block 4 Water Jacket 5 Radiator 6 Cooling water circuit 7 Upstream channel 8 Radiator flow path 9 Bypass flow path 10 Downstream flow path 11 Upstream branch 12 Downstream branch 13 Water pump 14 Flow path switching valve 15 No. 1 water temperature sensor 16 Second water temperature sensor 17 Electronic Control Unit (ECU) 18 Temperature judgment section 19 Temperature difference detection unit 20 Abnormal temperature difference timer counter T1 1st temperature T2 2nd temperature

Claims

[Claim 1] An abnormality detection device for an engine cooling device configured to circulate cooling water between a water jacket and a radiator of an engine and to circulate the cooling water by bypassing the radiator using a flow path switching valve, a first water temperature sensor that detects a first temperature of the cooling water at an outlet of the water jacket; a second water temperature sensor provided between the flow path switching valve and an inlet of the radiator to detect a second temperature of the cooling water; a controller for determining whether or not there is an abnormality in the flow path switching valve based on a temperature difference between the first temperature and the second temperature, The controller detecting a state in which the first temperature of the coolant in the water jacket has not risen to a temperature at which the coolant should be cooled by heat dissipation in the radiator; a first condition being that the first temperature of the cooling water has not risen to a temperature at which the cooling water should be cooled by heat dissipation in the radiator and that the temperature difference is small; a second condition being that the forced flow of the cooling water through the radiator for a purpose other than cooling has been completed; An abnormality detection device for an engine cooling system, characterized in that when both the first condition and the second condition are met, determination of an abnormality in the flow path switching valve based on the temperature difference is prohibited for a predetermined time after the completion of water flow.

Images