WO2024185105A1

WO2024185105A1 - Internal combustion engine variable valve diagnostic method and device

Info

Publication number: WO2024185105A1
Application number: PCT/JP2023/008942
Authority: WO
Inventors: 雅英小林; 裕也石井
Original assignee: 日産自動車株式会社
Priority date: 2023-03-09
Filing date: 2023-03-09
Publication date: 2024-09-12

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

Variable valve diagnosis method and device for internal combustion engine

This invention relates to fault diagnosis of variable valves included in the cooling water system of an internal combustion engine, and more specifically, to technology for avoiding misdiagnosis due to fluctuations in the cooling water temperature.

Patent Document 1 describes how, in a fault diagnosis in which the actual water temperature detected by a sensor is compared with an estimated water temperature to diagnose a thermostat fault, the diagnosis is prohibited for a predetermined time after the electric cooling water pump starts operating, thereby preventing misdiagnosis due to the movement of the cooling water.

Instead of a thermostat, a variable valve that adjusts the flow of coolant to multiple devices is sometimes installed in the cooling water system of an internal combustion engine. With such variable valves, there are various types of devices through which coolant flowed before the variable valve was activated and devices through which coolant flowed after activation, and if the diagnostic inhibition time is constant, there is a risk of misdiagnosis.

JP 2007-056722 A

The present invention provides a variable valve diagnosis method for an internal combustion engine that includes a water jacket, a water pump, and a variable valve that adjusts the flow of cooling water to a plurality of devices, the method diagnosing the variable valve by comparing an actual water temperature with an estimated water temperature, and temporarily prohibiting the diagnosis after the variable valve is operated, the method comprising:
The diagnosis inhibition time is set according to a combination of a device to which cooling water was supplied before the variable valve was operated and a device to which cooling water is supplied after the variable valve is operated.

By setting the prohibition time according to each combination in this way, misdiagnosis can be more reliably eliminated.

FIG. 2 is a circuit diagram of a cooling water system according to an embodiment. FIG. 1 is an explanatory diagram illustrating a schematic configuration of a rotary type variable valve. FIG. 2 is a functional block diagram of a diagnostic device according to an embodiment. 6 is a flowchart showing a process flow leading up to the start of diagnosis. 4 is a time chart showing the behavior associated with the operation of the variable valve.

Below, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows the circuit configuration of a cooling water circulation system of an internal combustion engine for a vehicle according to one embodiment. In the present 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 provided with a water jacket 1 through which cooling water flows over both the cylinder block and the cylinder head. At the inlet of the water jacket 1 of the internal combustion engine, a water pump 2 is provided which is mechanically driven by, for example, the output of the internal combustion engine. An electric water pump may also be used.

In the flow path 3 on the outlet side of the water jacket 1, a variable valve 7 is provided to adjust or switch the flow of cooling water to the three

flow paths

4, 5, and 6. The variable valve 7 is composed of an electric rotary valve. Flow path 4 is provided with a heater (heater core) 8 for the air conditioning system as a first heat exchange device. Flow path 5 is provided with an oil cooler 9 as a second heat exchange device that exchanges heat between the lubricating oil of the internal combustion engine and the cooling water. Flow path 6 is provided with a radiator 10 as a third heat exchange device that is disposed at the front end of the vehicle and exchanges heat between the outside air and the cooling water. In terms of the cooling water capacity of these three heat exchange devices, the radiator 10 has the largest capacity, and the oil cooler 9 has the smallest capacity.

The three

flow paths

4, 5, and 6 merge into one flow path at the inlet 11 of the water pump 2, and are configured so that the cooling water returns from the inlet 11 to the water pump 2.

A water temperature sensor 12 that detects the coolant temperature is disposed at the outlet of the water jacket 1. Note that in the present invention, the location of the water temperature sensor 12 is not necessarily limited to the outlet of the water jacket 1, but may be located on the inlet side of the water jacket 1 or upstream of the water pump 2.

The operating position of the rotary variable valve 7 is controlled by the controller 13. In addition to the detection signal of the water temperature sensor 12, various signals necessary for controlling the flow of cooling water are input to the controller 13. The controller 13 also performs a fault diagnosis of the variable valve 7 by comparing the actual water temperature with the estimated water temperature. Any suitable known method can be used for this fault diagnosis.

FIG. 2 is an explanatory diagram showing a schematic configuration of a rotary type variable valve 7. The variable valve 7 comprises a substantially cylindrical housing 21 with a cylindrical surface 21a on its inner circumference, a disk-shaped or columnar valve body 22 rotatably housed within the cylindrical surface 21a of the housing 21, and a motor (i.e., actuator) (not shown) that moves the valve body 22 in the rotational direction to change its angular position. The flow path 3 on the outlet side of the water jacket 1 is connected to the end face of the housing 21 (not shown in FIG. 2) and guides cooling water into the housing 21.

Ports

4A, 5A, and 6A, which are the ends of the

flow paths

4, 5, and 6, are opened on the cylindrical surface 21a of the housing 21. Port 4A, which guides cooling water to the heater 8, and port 5A, which guides cooling water to the oil cooler 9, are located approximately 90° apart from each other. The valve body 22 has a half-moon-shaped cutout 24 for the heater/oil cooler, and it is possible to introduce cooling water into one or both of

ports

4A and 5A through this cutout 24. Port 6A, which guides cooling water to the radiator 10, is located 180° away from port 4A for the heater 8 in terms of phase, and it is possible to introduce cooling water through a radiator cutout 25, which occupies a relatively small angular range provided in the valve body 22. The cutout 24 for the heater/oil cooler and the cutout 25 for the radiator are located at different axial positions and are not connected to each other. Port 6A, which guides cooling water to radiator 10, is located in the axial position corresponding to radiator cutout 25 and does not communicate with heater/oil cooler cutout 24.

The variable valve 7 of this embodiment can take the eight forms listed below depending on the angular position (rotational position) of the valve body 22. Note that "open" means that the corresponding port is open and cooling water is introduced. Flow paths not listed below as "open" are closed.

First state: A state in which no fluid flows through any of the

flow paths

4, 5, and 6 (a so-called zero flow state)
Second state: All flow paths open Third state: Heater flow path 4 open (opening degree varies depending on water temperature)
Fourth state: oil cooler flow passage 5 open (opening degree varies depending on water temperature), heater flow passage 4 fully open Fifth state: oil cooler flow passage 5 fully open, radiator flow passage 6 open (opening degree varies depending on water temperature)
Sixth state: oil cooler flow passage 5 fully open, heater flow passage 4 slightly open, radiator flow passage 6 fully open Seventh state: oil cooler flow passage 5 fully open, heater flow passage 4 fully open, radiator flow passage 6 open (opening degree varies depending on water temperature)
Eighth state: Oil cooler passage 5 open (opening degree varies depending on water temperature)
The above "varies the opening degree depending on the water temperature" means that the opening degree of the port is adjusted by slightly changing the angular position of the variable valve 7 according to the cooling water temperature. In the fourth to seventh states, cooling water is supplied to multiple heat exchange devices in parallel.

The valve body 22 of the variable valve 7 can operate in both the clockwise and counterclockwise directions in FIG. 2. For example, after a cold start of the internal combustion engine, the angular position of the valve body 22 changes in the clockwise direction as the coolant temperature rises, and the flow path can be changed from "first state → third state → fourth state → seventh state."

In addition, when the outside air temperature is high and the heat of the heater 8 for the air conditioning system is not required, the flow path can be changed from "first state → eighth state → fifth state" by changing the angular position of the valve body 22 in the counterclockwise direction as the coolant temperature rises. Even when the outside air temperature is high, when the defroster is in use, coolant can be supplied to the heater 8 by changing from "fifth state → sixth state".

The second state, "full flow passages open," is a state in which all ports are fully open, for example, due to a drop in cooling water pressure.

When the variable valve 7 is operated (in other words, the angle position is changed) and the flow path through which the coolant is supplied changes, the coolant in the heat exchange device through which the coolant had not flowed is pushed out and returns to the vicinity of the water temperature sensor 12 via the water pump 2. For example, when the state in which the coolant was not supplied to the radiator 10 changes to the state in which the coolant is supplied to the radiator 10 due to an increase in the coolant temperature, the relatively low-temperature coolant in the radiator 10 is pushed out and returns to the water pump 2. This causes the temperature detected by the water temperature sensor 12 to temporarily fluctuate, which may result in an erroneous diagnosis of a fault based on a comparison between the actual temperature (detected temperature) and the estimated temperature. For this reason, an appropriate delay time TD is provided between the operation of the variable valve 7 and the time when the fault diagnosis is permitted. This delay time TD is set according to the combination of the heat exchange device (including the zero-flow state) to which the coolant was supplied before the operation of the variable valve 7 and the heat exchange device to which the coolant is supplied after the operation of the variable valve 7.

In a preferred embodiment, as shown in Table 1 below, a delay time TD is predefined to be applied to each of a number of combinations of state changes that can occur with the operation of the variable valve 7. Table 1 lists the delay times TD in order of length, from the shortest delay time TD1 to the longest delay time TD9. That is, "TD1<TD2<>TD3<TD4<TD5<TD6<TD7<TD8<TD9". The right column of Table 1 lists representative state changes corresponding to each delay time TD.

Basically, the greater the increase in the total capacity of one or more heat exchange devices to which cooling water is supplied after the variable valve 7 is activated compared to the total capacity of one or more heat exchange devices to which cooling water was supplied before the variable valve 7 was activated, the longer the delay time TD is given.

FIG. 3 shows a functional block diagram of a diagnostic device of one embodiment configured by the controller 13. In addition, "MCV" in the figure means 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 angular position of the variable valve 7 based on the target angle of the variable valve 7, a pre-MCV transition state calculation unit 32 that determines the state of the flow path before the angular position of the variable valve 7 is changed based on the actual angle of the variable valve 7, a post-MCV transition state calculation unit 33 that determines the state of the flow path after the angular position of the variable valve 7 is changed based on the actual angle after operation, a delay time selection unit 34 that selects a delay time TD based on these pre-transition states and post-transition states, an elapsed time determination unit 35 that determines whether this delay time TD has elapsed, and a diagnosis unit 36 that diagnoses the variable valve 7. The diagnosis unit 36 starts diagnosing the variable valve 7 in response to a diagnosis permission signal output by the elapsed time determination unit 35 as the delay time TD elapses.

FIG. 4 is a flow chart showing the flow of processing up to the start of diagnosis executed by the controller 13. In step 1, it is determined whether or not there is an instruction to change the angular position of the variable valve 7. If the result is NO, the process proceeds to step 5. If there is an instruction to change the angular position, the process proceeds to step 2, where the state of the flow path before the change in the angular position of the variable valve 7 is stored. Next, in step 3, it is determined whether the change in the flow path has actually been completed, and the process waits until the change in the flow path is completed. When the change in the flow path (in other words, the operation of the variable valve 7) is completed, the process proceeds to step 4, where the timer counting the elapsed time is reset. In other words, the counting of the elapsed time is started. 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 the operation and the flow path after the 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 the process waits until the delay time TD has elapsed. When the delay time TD has elapsed, the process proceeds to step 7, where the diagnosis is permitted.

FIG. 5 is a time chart showing the behavior of the variable valve 7 as it is operated, showing the changes in (a) the variable valve target angle, (b) the actual variable valve angle, (c) the cooling water temperature, (d) the time elapsed after transition, and (e) the diagnosis permission flag.

As shown in (a), the target angle changes in steps in response to the request, 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 change in flow path is completed, a timer begins counting the elapsed time CT. Diagnosis is prohibited until this elapsed time CT reaches the delay time TD set in accordance with the combination of state changes. When the elapsed time reaches the delay time TD, the diagnosis permission flag shown in (d) turns ON and diagnosis is permitted. Note that diagnosis is performed even before the change in flow path.

As shown in (c), the coolant temperature temporarily drops when the flow path is changed, but by prohibiting diagnosis during the delay time TD, erroneous diagnosis due to this temporary drop in coolant temperature is suppressed. Fluctuations in coolant temperature caused by such changes in flow path differ 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 erroneous diagnosis can be suppressed while ensuring diagnostic time.

In the above embodiment, the delay time TD is preset in stages from TD1 to TD9, and any one of the delay times TD1 to TD9 is selectively applied, simplifying the control.

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 other types of variable valves are used. In addition, the device may also include a tank-shaped device that is not intended for heat exchange.

Claims

A variable valve diagnosis method for an internal combustion engine including a water jacket, a water pump, and a variable valve for adjusting a flow of cooling water to a plurality of devices, the method comprising: comparing an actual water temperature with an estimated water temperature to diagnose the variable valve; and temporarily prohibiting the diagnosis after the variable valve is operated, the method comprising:
setting a diagnosis prohibition time according to a combination of a device to which cooling water was supplied before the variable valve was activated and a device to which cooling water is supplied after the variable valve is activated;
A method for diagnosing a variable valve in an internal combustion engine.
the variable valve has a zero flow state in which no cooling water is supplied to any device;
the prohibition time when the variable device is activated from a zero flow state is set according to a device to which cooling water is supplied after the activation;
The variable valve diagnostic method for an internal combustion engine according to claim 1 .
the prohibition time is set longer as the total capacity of one or more devices to which cooling water is supplied after the operation increases significantly compared to the total capacity of one or more devices to which cooling water was supplied before the operation;
The variable valve diagnostic method for an internal combustion engine according to claim 1 .
The device is a heat exchange device including a radiator, an oil cooler, and a heater.
The variable valve diagnostic method for an internal combustion engine according to claim 1 .
The variable valve is an electric rotary valve.
The variable valve diagnostic method for an internal combustion engine according to claim 1 .
A prohibition time to be applied to each of a plurality of possible combinations including a mode in which cooling water is supplied to a plurality of devices in parallel is previously determined.
The variable valve diagnostic method for an internal combustion engine according to claim 1 .
Water jacket and
Water pump and
A variable valve for adjusting the flow of cooling water to multiple devices;
A variable valve diagnostic device for an internal combustion engine, which diagnoses a variable valve by comparing an actual water temperature with an estimated water temperature, and temporarily prohibits the diagnosis after the variable valve is operated,
setting a diagnosis prohibition time according to a combination of a device to which cooling water was supplied before the variable valve was activated and a device to which cooling water is supplied after the variable valve is activated;
Variable valve diagnostic device for internal combustion engines.