Method and apparatus for diagnosing variable valves in an internal combustion engine

Abstract

In the present invention, a cooling water system of an internal combustion engine is configured so that a variable valve (7) formed of an electric rotary valve adjusts the supply of cooling water to a heater (8), an oil cooler (9), and a radiator (10). A controller (13) performs failure diagnosis of the variable valve (7) by comparing an actual water temperature detected by a water temperature sensor (12) with an estimated water temperature. Water temperature temporarily fluctuates when the variable valve (7) operates and a flow path is changed; therefore, diagnosis is temporarily prohibited to prevent a misdiagnosis. An optimal delay time (TD1-TD9) is selected in accordance with the combination of a pre-change flow path and a post-change flow path.

Description

Technical Field

[0001] This invention relates to the fault diagnosis of a variable valve included in the cooling water system of an internal combustion engine, and more particularly to a technique for avoiding misdiagnosis due to fluctuations in the cooling water temperature.

Background Art

[0002] Patent Document 1 describes that in a fault diagnosis for diagnosing a failure of a thermostat by comparing the actual water temperature detected by a sensor with the estimated water temperature, after starting the operation of an electric cooling water pump, the diagnosis is prohibited for a predetermined time to prevent misdiagnosis due to the movement of the cooling water.

[0003] In the cooling water system of an internal combustion engine, instead of a thermostat, a variable valve for adjusting the flow of cooling water to a plurality of devices may be provided. In such a variable valve, there are various modes as devices through which cooling water flows before the operation of the variable valve and devices into which cooling water flows after the operation. If the diagnosis prohibition time is constant, there is a risk of misdiagnosis.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] This invention provides a variable valve diagnosis method for an internal combustion engine, which includes a water jacket, a water pump, and a variable valve for adjusting the flow of cooling water to a plurality of devices. The method diagnoses the variable valve by comparing the actual water temperature with the estimated water temperature, and temporarily prohibits this diagnosis after the operation of the variable valve. The diagnosis prohibition time is set according to the combination of the device to which cooling water is supplied before the operation of the variable valve and the device to which cooling water is supplied after the operation.

[0006] By setting prohibition periods according to each combination in this way, misdiagnosis can be eliminated more reliably. [Brief explanation of the drawing]

[0007] [Figure 1] Circuit diagram of a cooling water system in one embodiment. [Figure 2] A schematic diagram illustrating the configuration of a rotary variable valve. [Figure 3] A functional block diagram of a diagnostic device according to one embodiment. [Figure 4] A flowchart showing the process leading up to the start of diagnosis. [Figure 5] A time chart showing the behavior associated with the operation of a variable valve. [Modes for carrying out the invention]

[0008] An embodiment of this invention will be described in detail below with reference to the drawings. Figure 1 shows the circuit configuration of a cooling water circulation system for an internal combustion engine of a vehicle according to one embodiment. In this invention, the term "cooling water" is not limited to "water" but broadly includes so-called coolants and liquid-phase refrigerants. The internal combustion engine may be a gasoline engine or a diesel engine, and is equipped with a water jacket 1 through which cooling water flows across both the cylinder block and the cylinder head. A water pump 2, which is mechanically driven by the output of the internal combustion engine, for example, is provided at the inlet of the water jacket 1 of the internal combustion engine. An electric water pump may also be used.

[0009] The outlet passage 3 of the water jacket 1 is equipped with a variable valve 7 that adjusts or switches the flow of coolant to three passages 4, 5, and 6. The variable valve 7 is made of an electric rotary valve. Passage 4 is equipped with a heater (heater core) 8 for the air conditioning system as the first heat exchange device. Passage 5 is equipped with an oil cooler 9 that performs heat exchange between the lubricating oil of the internal combustion engine and the coolant as the second heat exchange device. Passage 6 is equipped with a radiator 10 that is located at the front end of the vehicle and performs heat exchange between the outside air and the coolant as the third heat exchange device. Of these three heat exchange devices, the radiator 10 has the largest coolant capacity, and the oil cooler 9 has the smallest.

[0010] The three flow paths 4, 5, and 6 merge into a single flow path at the inlet section 11 of the water pump 2, and are configured to return cooling water from the inlet section 11 to the water pump 2.

[0011] A water temperature sensor 12 for detecting the cooling water temperature is positioned at the outlet of the water jacket 1. In this invention, the position of the water temperature sensor 12 is not necessarily limited to the outlet of the water jacket 1, but may also be located on the inlet side of the water jacket 1 or upstream of the water pump 2.

[0012] The operating position of the rotary variable valve 7 is controlled by the controller 13. The controller 13 receives various signals necessary for controlling the flow of the cooling water, in addition to the detection signal from the water temperature sensor 12. The controller 13 also diagnoses a malfunction in the variable valve 7 by comparing the actual water temperature with the estimated water temperature. A known and appropriate method can be used for this malfunction diagnosis.

[0013] Figure 2 is a schematic diagram illustrating the configuration of the rotary variable valve 7. The variable valve 7 comprises a substantially cylindrical housing 21 having a cylindrical surface 21a on its inner circumference, a disc-shaped or cylindrical valve body 22 rotatably housed within the cylindrical surface 21a of the housing 21, and a motor (i.e., actuator) (not shown) that rotates the valve body 22 to change its angular position. The outlet-side flow path 3 of the water jacket 1 is connected to the end face of the housing 21 (not shown in Figure 2) and guides cooling water into the interior of the housing 21.

[0014] Ports 4A, 5A, and 6A, which are the ends of the flow paths 4, 5, and 6, are opened in the cylindrical surface 21a of the housing 21. Port 4A, which leads coolant to the heater 8, and port 5A, which leads coolant to the oil cooler 9, are located approximately 90° apart from each other. The valve body 22 is equipped with a crescent-shaped notch 24 for the heater / oil cooler, and coolant can be introduced into one or both of ports 4A and 5A through this notch 24. Port 6A, which leads coolant to the radiator 10, is located 180° apart in phase from port 4A for the heater 8, and coolant can be introduced through a radiator notch 25 provided in the valve body 22, which occupies a relatively small angular range. The heater / oil cooler notch 24 and the radiator notch 25 are located in different axial positions and are not in communication with each other. Port 6A, which leads coolant to the radiator 10, is located in an axial position corresponding to the radiator notch 25 and does not communicate with the heater / oil cooler notch 24.

[0015] In this embodiment, the variable valve 7 can take on one of the eight states listed below, depending on the angular position (rotational position) of the valve body 22. "Open" means that the corresponding port is open and cooling water is introduced. Flow paths not described as "open" below are closed.

[0016] First state: No flow in any of the channels 4, 5, or 6 (so-called zero-flow state) Second state: All flow channels open Third state: Heater channel 4 open (opening degree varies depending on water temperature) State 4: The flow path 5 for the oil cooler is open (the opening degree varies according to the water temperature), and the flow path 4 for the heater is fully open. State 5: The flow path 5 for the oil cooler is fully open, and the flow path 6 for the radiator is open (the opening degree varies according to the water temperature). State 6: The flow path 5 for the oil cooler is fully open, the flow path 4 for the heater is slightly open, and the flow path 6 for the radiator is fully open. State 7: The flow path 5 for the oil cooler is fully open, the flow path 4 for the heater is fully open, and the flow path 6 for the radiator is open (the opening degree varies according to the water temperature). State 8: The flow path 5 for the oil cooler is open (the opening degree varies according to the water temperature). The above-mentioned "the opening degree varies according to the water temperature" means that the opening degree of the port is adjusted by the slight change of the angular position of the variable valve 7 according to the cooling water temperature. In states 4 to 7, the cooling water is supplied in parallel to a plurality of heat exchange devices.

[0017] The valve body 22 of the variable valve 7 can operate both in the clockwise direction and the counterclockwise direction in FIG. 2. For example, after the cold start of the internal combustion engine, as the cooling water temperature rises, the angular position of the valve body 22 changes in the clockwise direction, so that the flow path can be changed as "State 1 → State 3 → State 4 → State 7".

[0018] Also, when the heat quantity of the heater 8 for the air conditioner is not required at a high outside air temperature, as the cooling water temperature rises, the angular position of the valve body 22 is changed in the counterclockwise direction, so that the flow path can be changed as "State 1 → State 8 → State 5". Note that even at a high outside air temperature, when the defroster is used, the cooling water is supplied to the heater 8 by changing as "State 5 → State 6". [[ID=XX]]

[0019] [[ID=XX]] [[ID=XX]] The "fully open all flow paths" in State 2 is, for example, a mode in which all ports are fully open due to the decrease in the cooling water pressure.

[0020] When the variable valve 7 operates (in other words, changes the angular position) and the flow path through which the cooling water is supplied changes, the cooling water in the heat exchange device where the cooling water has not flowed until then is pushed out and returns to the vicinity of the water temperature sensor 12 via the water pump 2. For example, when the supply of the cooling water to the radiator 10 changes from a state where the cooling water is not supplied to the radiator 10 due to an increase in the cooling water temperature to a state where the cooling water is supplied to the radiator 10, the relatively low-temperature cooling water in the radiator 10 is pushed out and returns to the water pump 2. As a result, the detected temperature of the water temperature sensor 12 fluctuates temporarily, and misdiagnosis may occur in the failure diagnosis by comparing the actual temperature (detected temperature) with the estimated temperature. Therefore, after the variable valve 7 operates, an appropriate delay time TD is given until the failure diagnosis is permitted. And this delay time TD is set according to the combination of the heat exchange device (including the zero flow state) where the cooling water was supplied before the operation of the variable valve 7 and the heat exchange device where the cooling water is supplied after the operation.

[0021] In a preferred embodiment, as shown in Table 1 below, for a plurality of combinations of state changes that may occur with the operation of the variable valve 7, the delay time TD applied to each is predetermined. Table 1 summarizes the lengths of the delay times TD in ascending order from the minimum delay time TD1 to the maximum delay time TD9. That is, "TD1 < TD2 < TD3 < TD4 < TD5 < TD6 < TD7 < TD8 < TD9". In the right column of Table 1, representative state changes corresponding to each delay time TD are described.

[0022]

Table 1

[0023] Figure 3 shows a functional block diagram of a diagnostic device of one embodiment, which is composed of a controller 13. In the figure, "MCV" refers to the variable valve 7. As shown in the figure, the diagnostic device of one embodiment includes an MCV transition instruction detection unit 31 that detects whether there is an instruction to change the angle position of the variable valve 7 based on the target angle of the variable valve 7; an MCV pre-transition state calculation unit 32 that determines the state of the flow path before the angle position change of the variable valve 7 based on the actual angle of the variable valve 7; an MCV post-transition state calculation unit 33 that determines the state of the flow path after the angle position change of the variable valve 7 based on the actual angle after operation; a delay time selection unit 34 that selects a delay time TD based on these pre-transition and post-transition states; an elapsed time determination unit 35 that determines whether the delay time TD has elapsed; and a diagnostic unit 36 ​​that diagnoses the variable valve 7. The diagnostic unit 36 ​​starts diagnosing the variable valve 7 when a diagnostic permission signal is output by the elapsed time determination unit 35 as the delay time TD elapses.

[0024] Figure 4 is a flowchart showing the process flow from the controller 13 to the start of the diagnosis. In step 1, it is determined whether there is an instruction to change the angle position of the variable valve 7. If NO, proceed to step 5. If there is an instruction to change the angle position, proceed to step 2 and store the state of the flow path before the angle position change of the variable valve 7. Next, in step 3, it is determined whether the change in the flow path has actually been completed and waits until the change in the flow path is completed. Once the change in the flow path (in other words, the operation of the variable valve 7) is completed, proceed to step 4 and reset the timer that is counting the elapsed time. In other words, start counting the elapsed time. Next, in step 5, as shown in Table 1, a delay time TD corresponding to the state change due to the operation of the variable valve 7 (in other words, the combination of the flow path before operation and the flow path after operation) is selected. Next, in step 6, it is determined whether the elapsed time is equal to or greater than the delay time TD and waits until the delay time TD has elapsed. Once the delay time TD has elapsed, proceed to step 7 and allow the diagnosis.

[0025] Figure 5 is a time chart showing the behavior associated with the operation of the variable valve 7, and shows the changes in (a) variable valve target angle, (b) variable valve actual angle, (c) coolant temperature, (d) elapsed time after transition, and (e) diagnostic permission flag.

[0026] As shown in (a), the target angle changes stepwise as required, but the actual angle of the variable valve 7, whose valve body 22 is driven by the motor, changes gradually as shown in (b). When the actual angle reaches the target angle at time t1 and the flow path change is complete, the timer starts counting the elapsed time CT. Diagnosis is prohibited until this elapsed time CT reaches the delay time TD, which is set according to the combination of state changes. Once the elapsed time reaches the delay time TD ( e The diagnostic permission flag shown in () is turned ON, and the diagnosis is permitted. Note that the diagnosis is also performed before the flow path is changed.

[0027] As shown in (c), the coolant temperature temporarily decreases when the flow path is changed, but by prohibiting diagnosis during the delay time TD, misdiagnosis due to this temporary decrease in coolant temperature is suppressed. The fluctuation in coolant temperature associated with such changes in the flow path differs depending on the combination of the flow path before and after the change. In the above embodiment, the optimal delay times TD1 to TD9 are selected according to the combination of the flow path before and after the change, so that misdiagnosis can be suppressed while ensuring sufficient diagnostic time.

[0028] In the above embodiment, the delay time TD is predetermined in steps from TD1 to TD9, and any of the delay times TD1 to TD9 is selectively applied, thus simplifying the control.

[0029] Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment and various modifications are possible. For example, in the above embodiment, an electric rotary valve is used as the variable valve, but the present invention can also be applied when using other types of variable valves. Furthermore, the device may also include, for example, a tank-shaped device that is not intended for heat exchange.

Claims

1. A variable valve diagnostic method for an internal combustion engine comprises a water jacket, a water pump, and a variable valve that adjusts the flow of cooling water to multiple devices, and diagnoses the variable valve by comparing the actual water temperature with the estimated water temperature, and temporarily prohibits this diagnosis after the variable valve has been activated. Depending on the combination of devices to which coolant was supplied before the operation of the above-mentioned variable valve and devices to which coolant is supplied after the operation, a diagnostic prohibition time is set. Diagnostic method for variable valves in internal combustion engines.

2. The above variable valve has a zero-flow state in which no cooling water is supplied to any device. The above-mentioned prohibition time when the variable valve is activated from a zero-flow state is set according to the device to which cooling water is supplied after activation. The method for diagnosing variable valves in an internal combustion engine according to claim 1.

3. The longer the prohibition time is set, the greater the increase in the total capacity of one or more devices to which coolant is supplied after operation, compared to the total capacity of one or more devices to which coolant was supplied before operation. The method for diagnosing variable valves in an internal combustion engine according to claim 1.

4. The above device consists of a heat exchange device including a radiator, an oil cooler, and a heater. The method for diagnosing variable valves in an internal combustion engine according to claim 1.

5. The above variable valve consists of an electrically operated rotary valve. The method for diagnosing variable valves in an internal combustion engine according to claim 1.

6. For each of the multiple possible combinations, including the configuration in which cooling water is supplied to multiple devices in parallel, a predetermined prohibition time is set for each. The method for diagnosing variable valves in an internal combustion engine according to claim 1.

7. Water jacket and, Water pump and A variable valve that adjusts the flow of cooling water to multiple devices, A variable valve diagnostic device for an internal combustion engine, which compares the actual water temperature with the estimated water temperature to diagnose the variable valve, and temporarily prohibits this diagnosis after the variable valve has been operated, Depending on the combination of devices to which coolant was supplied before the operation of the above-mentioned variable valve and devices to which coolant is supplied after the operation, a diagnostic prohibition time is set. A variable valve diagnostic device for internal combustion engines.

Images