JP2000008935A - Movement confirmation method of variable valve timing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To confirm the movement of a variable valve timing device by a simple constitution surely. SOLUTION: In an intake valve 14 and exhaust valve 15 provided on the top of the cylinder 12 of a vehicular engine 10, the timing and lift amount of a valve opening is switched by a low speed time and a high speed time by a variable valve timing device 26 provided with cam switch mechanisms 24, 25. ECU 11 utilizes the change of a suction pressure PM detected by PM sensors 18, 19 provided on the intake manifold 16 or exhaust manifold 17 to confirm the motion by the variable valve timing device 26. When the intake valve 14 is opened, PM reflects the pressure change in a cylinder 12 and changes. When the lift amount is big, the slant droped at the change time becomes large and a change width is also becomes big. A switch motion state can be confirmed by the timing, slant or change width for starting and finishing the change.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for confirming the operation of a variable valve timing device which is employed in an automobile engine or the like and changes the opening / closing timing of an intake valve and an exhaust valve of an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, in automobile engines and the like,
The valve timing and the valve lift amount are changed according to the load state of the engine to increase the engine output and improve idle stability. FIG. 6 and FIG.
1 shows a schematic configuration of a typical variable valve timing device. FIG. 6 shows an external configuration of a main part, and FIG. 7 shows a cross-sectional configuration of the main part.

The valves 1a and 1b are intake valves or exhaust valves provided at the head of one cylinder of the engine. In order to increase the diameter of the valve and reduce the weight, the two valves 1a and 1b are paired,
It operates as one intake valve or one exhaust valve. The two valves 1a and 1b are connected by a T-shaped lever 2, and are displaced in the axial direction according to either the high speed cam 3 or the low speed cam 4. Switching between the high-speed cam 3 and the low-speed cam 4 is performed by selecting the high-speed rocker arm 5 or the low-speed rocker arm 6 with the hydraulic piston 7.
The selected cam is driven by the cam shaft 8.

FIG. 7A shows a state in which hydraulic pressure is applied to a hydraulic piston 7 to drive a high-speed cam via a high-speed rocker arm 5. FIG. 7B shows a state in which the high-speed cam 3 is not driven and the low-speed cam 4 is driven without applying hydraulic pressure to the hydraulic piston 7. The high-speed cam 3 and the low-speed cam 4 operate at different timings of the intake valve and the exhaust valve, and the valve overlap timing at which the exhaust valve and the intake valve are overlapped and open at low speed. And the speed is changed differently.

The prior art relating to the variable valve timing device is disclosed in Japanese Patent Application Laid-Open Nos. Hei 6-317116 and Hei 7-3011.
44, JP-A-9-88864, JP-A-9-287496, and the like. In Japanese Patent Application Laid-Open No. 6-317116, a self-diagnosis of a control
It measures by measuring the combustion pressure inside the cylinder. JP 7
In the prior art of −301144, the intake pressure is used for highly accurate calculation of the intake air amount required for smooth engine control. In the prior art of Japanese Patent Application Laid-Open No. 9-88643, the operating state of the engine is determined from the intake air flow rate to diagnose whether the variable valve timing device is normal or abnormal. In the prior art of Japanese Patent Application Laid-Open No. 9-287496, the fuel injection amount is controlled based on the intake pressure, the engine rotation speed, and the valve timing according to the operation state of the variable valve timing device.

[0006]

In a variable valve timing device provided in an automobile engine or the like, FIG.
As shown in FIG. 7, switching between a plurality of high-speed cams 3 and low-speed cams 4 is performed by moving a hydraulic piston 7 in and out by hydraulic control. Hydraulic piston 7
Has a role of connecting the high-speed rocker arm 5 to the T-shaped lever 2. This connecting operation is performed when the engine is rotating at a high speed, so that the hydraulic piston 7
Problems such as not entering the high-speed rocker arm 5 as shown in FIG. 7A or not coming out as shown in FIG. Therefore, it is necessary to confirm whether or not the hydraulic piston 7 is actually displaced by the hydraulic control.

[0007] Of the above prior art, Japanese Patent Laid-Open No. 6-317
116 and JP-A-9-88643, a diagnosis is made on the variable valve timing device. JP-A-6-317
In 116, it is necessary to detect the combustion pressure by mounting it on the washer of the spark plug or by providing an in-cylinder pressure sensor that directly faces the inside of the cylinder and detects the combustion pressure. It is desired that the engine is as small and efficient as possible, and it is very difficult to install an indoor pressure sensor.

In the prior art of Japanese Patent Application Laid-Open No. 9-88643, it is not necessary to detect the combustion pressure, and the intake pressure is detected to diagnose the variable valve timing device. The detection of the intake pressure can be easily performed with less restrictions than the detection of the combustion pressure. However, in order to diagnose the variable valve timing device, it is necessary to calculate the intake air flow rate.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for confirming the operation of a variable valve timing device, which can directly confirm the switching operation of the variable valve timing device from the detection result of the intake pressure.

[0010]

SUMMARY OF THE INVENTION The present invention confirms the operation of a variable valve timing apparatus provided in an internal combustion engine and capable of changing the operation timing of an intake valve and an exhaust valve by switching a plurality of cams. In the method, a pressure detector is installed in the intake side or the exhaust side manifold, and based on the fluctuation state of the pressure detected by the pressure detector, the operation state of the valve is determined, and the variable valve timing device is This is a method for confirming the operation of the variable valve timing device, characterized by confirming the operation.

According to the present invention, the operation of the variable valve timing device for changing the operation timing of the intake valve and the exhaust valve by switching a plurality of cams is performed by installing an air pressure detector in the intake side or exhaust side manifold. Then, the determination is made based on the fluctuation state of the detected atmospheric pressure. Since the air pressure in the manifold fluctuates in accordance with the operation state of the intake valve or the exhaust valve, the operation of the variable valve timing device can be easily confirmed based on the fluctuation state of the air pressure.

Further, the present invention is characterized in that a change start point is obtained from the change state of the atmospheric pressure, and it is determined that the operation of the valve starts at the change start point.

According to the present invention, the start of the operation of the valve by the variable valve timing device is determined as the start point of the fluctuation state of the atmospheric pressure. When the variable valve timing device switches the cam, the operation timing of the valve also changes, so the start point of the change in the atmospheric pressure in the manifold also changes, and the state of the switching operation of the variable valve timing device can be confirmed from the start point of the change. .

Further, the present invention is characterized in that a gradient of the fluctuation is obtained from the fluctuation state of the atmospheric pressure, and the lift amount of the valve is determined based on the gradient of the fluctuation.

According to the present invention, the lift amount of the valve is determined from the gradient of the pressure change in the manifold. The lift amount of the valve changes by switching the cam by the variable valve timing device, and if the lift amount of the valve increases, the change in the pressure in the cylinder affects the inside of the manifold,
The gradient of the change in the atmospheric pressure in the manifold increases. If the lift amount changes due to the cam switching by the variable valve timing device, the gradient of the fluctuation of the atmospheric pressure changes, and the operation of cam switching by the variable valve timing can be confirmed.

Further, the present invention is characterized in that a fluctuation range is obtained from the fluctuation state of the atmospheric pressure, and the lift amount of the valve is determined based on the fluctuation range.

According to the present invention, the lift amount of the valve is determined on the basis of the fluctuation range obtained from the fluctuation state of the atmospheric pressure. The lift amount of the valve changes due to switching of the cam by the variable valve timing device, and the greater the lift amount, the greater the range of fluctuation. Therefore, the operation of cam switching by the variable valve timing device can be confirmed from the range of fluctuation.

In the present invention, the air pressure detector is provided on the intake side. According to the present invention, the operation of the variable valve timing device is confirmed by detecting the air pressure on the intake side. On the intake side, the air pressure tends to fluctuate reflecting the opening and closing of the intake valve, and the switching of the cam by the variable valve timing device can be easily and accurately confirmed.

In the present invention, the vehicle engine includes a plurality of cylinders, and the air pressure detector is provided for each cylinder.

According to the present invention, the pressure in the manifold is detected for each cylinder of an internal combustion engine having a plurality of cylinders, and the switching operation of the variable valve timing device is detected based on the fluctuation. As a result, the operation of the variable valve timing device can be accurately confirmed for each cylinder.

[0021]

FIG. 1 shows a configuration related to control of a vehicle engine 10 mounted on an automobile as an embodiment of the present invention. The vehicle engine 10 is operated under the control of an electronic control unit (hereinafter abbreviated as “ECU”) 11. The vehicle engine 10 has a plurality of cylinders 12, and reciprocates a piston 13 in the cylinder 12 to generate a rotation output on a crankshaft. In response to the displacement of the piston 13 in the cylinder 12, the intake valve 14 and the exhaust valve 15 operate. For example, as shown in FIG. 6, the intake valve 14 and the exhaust valve 15 are provided in a pair, and the double overhead camshaft abbreviates “DOHC”.
The camshafts are separately driven. Further, the intake valve 14 and the exhaust valve 15
And a variable valve timing device as shown in FIG.
The rotation speed of the vehicle engine 10 is controlled so as to have different opening / closing timings and lift amounts between a low speed and a high speed.

An air-fuel mixture in which air is mixed with fuel is supplied from an intake valve 14 through an exhaust manifold 16. From the exhaust valve 15, the cylinder 12
The exhaust gas whose combustion has been completed is discharged into the exhaust manifold 17. A PM sensor 1 as a pressure detector is provided in the intake manifold 16 and the exhaust manifold 17.
8, 19 are provided respectively.

The ECU 11 uses the detection outputs of the PM sensors 18 and 19 to calculate the intake air amount as disclosed in, for example, JP-A-7-301144.
The fuel injection amount is calculated as disclosed in US Pat. The crank angle representing the angular displacement of the crankshaft is also input from the vehicle engine 10 to the ECU 11. The crank angle indicates an angle with respect to the top dead center of the piston 13 (may be abbreviated as “TDC” from Top Dead Center). The crank angle is displaced by 180 ° from the top dead center, and the piston 13 is moved to the bottom dead center (“BDC” from Bottom Dead Center).
During the reciprocating movement from the bottom dead center to the top dead center.
Controls so that the operation as a four-cycle internal combustion engine is appropriately performed. If the intake valve 14 is opened and the exhaust valve 13 is closed when the piston 13 moves from the top dead center to the bottom dead center in the cylinder 12, the fuel in the cylinder 12 is mixed with air. An inhalation step of inhaling air can be performed. If the piston 13 is moved from the bottom dead center to the top dead center with the intake valve 14 and the exhaust valve 15 closed, a compression process of the air-fuel mixture sucked into the cylinder 12 can be performed. When the compressed air-fuel mixture is ignited by the ignition plug 20, the air-fuel mixture starts burning,
While the combustion gas is expanding, the piston 13 is pressed to the bottom dead center side, and an expansion step of generating power by rotating the crankshaft can be performed. If the exhaust valve 15 is opened, an exhaust process of discharging the combustion gas in the cylinder 13 to the outside while the piston 13 moves from the bottom dead center to the top dead center can be performed. The ECU 11 controls the ignition timing of the ignition plug 20 and controls the fuel injection device 21 provided in the intake manifold 16 to inject fuel. The angular displacement of the crankshaft is detected by the angle sensor 22, and the detection result is given to the ECU 11. In order to control the operation of the vehicle engine 10, outputs from the throttle opening sensor 23 and the like are also supplied to the ECU 11.

Intake valve 14 and exhaust valve 15
Are provided with cam switching mechanisms 24 and 25 for switching cams when the rotational speed of the vehicle engine 10 is low and high, respectively. The structure of the cam switching mechanisms 24 and 25 can be the same as in FIGS. The variable valve timing device 26 constituted by the cam switching mechanisms 24 and 25 is switched by the ECU 11 according to the rotation speed of the vehicle engine 10 detected by the angle sensor 22. The ECU 11 can perform a self-diagnosis operation of checking whether or not the cam switching mechanisms 24 and 25 are actually operating by the variable valve timing mechanism 26 based on the outputs of the PM sensors 18 and 19.

FIG. 2 shows the relationship between the lift, which is the operating state of the exhaust valve 14, and the process of the piston 13. FIG.
2A shows a change in the lift of the intake valve 14 due to the operation of the low-speed cam, and FIG. 2B shows a change in the lift of the intake valve 14 due to the operation of the high-speed cam. In the low-speed operation shown in (a), for example, the lift of the intake valve 14 starts after passing TDC, and the lift ends before BDC. In the high-speed operation shown in (b), the lift of the intake valve 14 starts before the TDC, and the lift of the intake valve 14 ends later than the BDC. Also, the lift amount is higher at high speed than at low speed.

FIG. 3 shows a change in the intake pressure (hereinafter sometimes abbreviated as "PM") detected by a PM sensor 18 provided in the intake manifold 16 in accordance with the lift of the intake valve 14 shown in FIG. . FIG. 3A shows a change at a low speed detected corresponding to FIG. 2A, and FIG. 3B shows a change at a high speed detected corresponding to FIG. 2B. . The change in PM shown in FIG. 3 starts to change in response to the start of the lift shown in FIG. 2, and ends in response to the end of the lift. When the intake valve 14 is opened, the lift start point and the end point of the intake valve 14 can be determined from the start point and the end point of the pulsation of the PM because the internal pressure of the cylinder 12 is affected. Since the lift start point and the lift end point are changed by switching of the variable valve timing device 26, the operation state of the variable valve timing device 26 can be confirmed based on the lift start point and the lift end point.

From FIGS. 2 and 3, it can be seen that the lift amount of the intake valve 14 can also be determined based on the inclination of the decrease in PM in the intake process. That is, when the lift amount is large, a sharp change is made close to the change in the cylinder internal pressure. When the lift amount is small, the air resistance received by the air-fuel mixture sucked into the cylinder 12 through the intake valve 14 increases, and the slope of the decrease in PM decreases.

FIG. 4 shows a procedure for confirming the operation state of the variable valve timing device 26 based on the inclination at the time when the PM change state shown in FIG. The procedure is started from step a1, and in step a2, a change in PM accompanying the lift of the intake valve 14 is detected. In step a3, the inclination of PM decrease is detected. In step a4, the detected slope value is compared with a reference value. If the inclination is not smaller than the reference value, it is determined in step a5 that the high-speed cam having a large lift amount is operating. If the inclination is smaller than the reference value in step a4, it is determined in step a6 that the low-speed cam having a small lift amount is operating. After the determination in step a5 or step a6, step a7
To end the procedure.

FIG. 3 also shows that the lift amount can be determined from the fluctuation range of the PM. That is, the larger the lift amount, the closer to the change in the internal pressure of the cylinder 12, so that P
This is because the fluctuation range of M becomes large. FIG. 5 shows a procedure for confirming the operation state of the variable valve timing device 26 based on the magnitude of the lift amount. The procedure starts from step b1, and in step b2, a change in PM accompanying the lift of the intake valve 14 is detected. In step b3, the maximum value of the change in the lift amount is detected as the fluctuation width of PM. In step b4, it is determined whether or not the fluctuation width is smaller than the reference value. If it is determined that the fluctuation width is not smaller than the reference value, it is determined in step b5 that the high-speed cam is operating.
When it is determined in step b4 that the fluctuation width is smaller than the reference value, it is confirmed in step b6 that the operation of the low-speed cam is performed. When the checking operation in step b5 or step b6 ends, the procedure ends in step b7.

The ECU 11 shown in FIG. 1 controls the operating state of the vehicle engine 10 based on the engine speed calculated based on the output from the angle sensor 22 and the throttle opening detected by the throttle opening sensor 23, and the PM sensor 1
8 and 19, the intake valve 14
It is also possible to determine which cam is currently reflected in the lift timing and lift amount of the exhaust valve 15. If the throttle opening and the engine speed are determined, PM should take a certain value. The time during which the intake valve 14 and the exhaust valve 15 are open is long,
In addition, when the lift amount increases, the resistance of gas passing through the intake valve 14 and the exhaust valve 15 decreases, so that the PM value increases even with the same throttle opening and engine speed. A map 27 indicating the relationship between the operating state and the PM is prepared for each cam, and by comparing with a value actually detected by the PM sensors 18 and 19, it is determined which cam is currently used. be able to.

Since the valve timing and the lift amount directly affect the engine characteristics, if a cam different from the cam designated by the ECU 11 by controlling the variable valve timing device 26 is used, the fuel injection amount, ignition timing, etc. Deviates from the optimal conditions. If the operation state of the valve can be determined based on the change state of the PM detected from the PM sensors 18 and 19, the occurrence of a failure can be prevented at a lower cost than using other mechanical sensors or the like. Also,
If it is detected that the operation of the variable valve timing device 26 is inappropriate, the hydraulic control for returning to the normal state is executed, or an operation abnormality is notified to indicate that repair or inspection is necessary. Such control is also possible.

[0032]

As described above, according to the present invention, the switching operation of the variable valve timing device capable of changing the operation timing of the intake valve or the exhaust valve is described.
By disposing an air pressure detector in the intake side or the exhaust side manifold, it is possible to easily and surely check the fluctuation state of the air pressure.

Further, according to the present invention, the operation start point of the valve can be determined from the start point of the fluctuation of the atmospheric pressure, and the operation of the variable valve timing device can be confirmed from the difference in the operation start point.

Further, according to the present invention, it is possible to determine the lift amount of the valve based on the gradient of the fluctuation of the atmospheric pressure, and confirm the operation of the variable valve timing device.

Further, according to the present invention, the operation of the variable valve timing device can be confirmed by judging the lift amount of the valve from the fluctuation width of the atmospheric pressure.

Further, according to the present invention, it is possible to detect a change in air pressure on the intake side and easily determine switching of the operating state of the valve due to the operation of the variable valve timing device.

Further, according to the present invention, the operation of the variable valve timing device can be confirmed for each cylinder of the internal combustion engine.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration for implementing an embodiment of the present invention.

FIG. 2 is a graph showing a change in lift of an intake valve 14 switched by a variable valve timing device 26 of FIG.

FIG. 3 is a graph showing a change in intake pressure (PM) that changes in response to a change in the lift in FIG. 1;

FIG. 4 is a flowchart showing a procedure for confirming the operation of the variable valve timing device according to the inclination of the PM decrease in FIG. 3;

FIG. 5 is a flowchart showing a procedure for confirming the operation of the variable valve timing device 26 based on the PM change width in FIG.

FIG. 6 is a partial perspective view showing an example of a mechanism for switching the valve to be driven by the high-speed cam 3 or the low-speed cam 4.

FIG. 7 is a sectional view showing an operation state of the mechanism of FIG. 6;

[Explanation of symbols]

 Reference Signs List 10 Vehicle engine 11 ECU 12 Cylinder 13 Piston 14 Intake valve 15 Exhaust valve 16 Intake manifold 17 Exhaust manifold 18, 19 PM sensor 22 Angle sensor 24, 25 Cam switching mechanism 26 Variable valve timing device 27 Map

Claims (6)

[Claims] 1. A method for confirming an operation of a variable valve timing device provided in an internal combustion engine and capable of changing an operation timing of an intake valve and an exhaust valve by switching a plurality of cams, comprising: Alternatively, an air pressure detector is installed in the exhaust side manifold, and based on the fluctuation state of the air pressure detected by the air pressure detector, the operation state of the valve is determined, and the operation of the variable valve timing device is confirmed. To check the operation of the variable valve timing device. 2. The method according to claim 1, wherein a start point of the change is determined from the change state of the atmospheric pressure, and it is determined that the operation of the valve starts at the start point of the change. 3. The method according to claim 1, wherein a slope of the variation is obtained from the variation state of the atmospheric pressure, and a lift amount of the valve is determined based on the slope of the variation. 4. The method according to claim 1, wherein a variation range is obtained from the variation state of the atmospheric pressure, and a lift amount of the valve is determined based on the variation range. 5. The method according to claim 1, wherein the air pressure detector is provided on an intake side. 6. The operation check of the variable valve timing device according to claim 1, wherein the vehicle engine includes a plurality of cylinders, and the air pressure detector is provided for each cylinder. Method.