JPS631728A - Intake and exhaust valve lift control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent engine operation in a dangerous operation range by stopping lift control and limiting the number of engine revolutions when the engine has been distinguished to be in operating condition under which the lift control can not be normally performed on the basis of power source voltage or engine temperature. CONSTITUTION:A varying mechanism 80 which varys the lift characteristics of a suction and exhaust valve by variably controlling the oscillatory supporting point of a rocker arm through a lift control cam is provided, and driven by a driving means 81. The driving means 81 is controlled by a controlling means 84 according to deviation between an actual lift position detected by a position detecting means 83 and a target lift position based on operating condition. In addition to that, a distinguishing means 87 to previously distinguish whether an engine is or not in operating condition under which the lift control can be normally performed on the basis of outputs fed from a detecting means 85 for power source voltage and a detecting means 86 for engine temperature is provided. When the operating condition has been distinguished to be abnormal, a control stopping means 88 stops the lift control, and moreover a limiting means 89 for the number of revolutions limits the number of engine revolutions.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) This invention allows the opening/closing timing of intake and exhaust valves, the valve lift amount, or both to be variable according to operating conditions ffi! The present invention relates to an intake/exhaust valve lift control device for an internal combustion engine.

(Prior technology) Intake/exhaust valve lift that variably controls the opening/closing of the intake/exhaust valves and the amount of valve opening according to the engine operating conditions so that valve overlap and fresh air filling efficiency are always optimally achieved. Various control devices have been proposed in the past, one of which is shown in Figures 4 and 5 (Japanese Patent Laid-Open No. 60-261
(See No. 09).

The one shown is an example of an overhook cam type, in which the rocker arm 4 swings according to the cam profile formed on the circumferential surface of the intake valve cam 1, and the intake valve 2 is moved against the valve spring 3. However, instead of fixing the rocking fulcrum of the rocker arm 4, a lever 6 (-'416 A) that rolls into contact with the back surface 4A of the rocker arm 4 is fixed to the bracket 2 door (silling head). The rocker arm 4 is supported by a support 7α on a support 7α, and the inclination angle of this lever 6 is variably controlled by a lift control cam 8, thereby making the rocking fulcrum of the rocker arm 4 a variable fulcrum. Note that 9 is a hydraulic pivot that maintains the valve clearance at zero.

That is, six lattice-shaped cam surfaces 8A to 8F are formed on the surface of the 97F control cam 8, and the distances from the axis are different. For example, cam surface 8F (the cam with the longest distance from the axis) In the illustrated state supported by
The back side 4A of the mouth/z arm rolls to the left from the X1 point and makes contact with the 4fi, but since the distance between this variable swing fulcrum and the valve head 2A of the intake valve 2 is long, This results in a lift characteristic that has a long valve opening time and a high valve lift amount.

On the other hand, according to the cam surface 8A (the cam surface with the smallest distance from the shaft center), the lever 6 is pushed upward one degree from the illustrated state and tilted, so that the back surface 4A of the rocker arm is connected to the lever 6. The device that makes rolling contact will now roll with Xa.

In other words, the rolling contact device shifts to the right in the figure, and the distance between the swing fulcrum and the valve head 2A becomes shorter, so LA in Figure 7
Lift characteristics having a short valve opening time and a low valve lift amount are obtained.

Next, a cam control shaft 11 is connected to the lift control cam 8 via a coil spring 10 as an elastic member, and by rotating the cam control shaft 11, the elastic energy stored in the coil spring 10 is utilized. Then, in the base circle region of the cam 1 where a large valve spring load does not occur, the IJ7 control cam 8 is driven to predetermined cam surfaces 88 to 8F.

A 72 actuator 15 such as a step motor is used as a driving means for the cam control shaft 11.
The control unit 25+ rotates the cam control shaft 11 by a predetermined angle so as to achieve the target device determined according to the operating state. Note that 177) is increased by clockwise rotation of the actuator 15, and for convenience of explanation below, increasing the lift will be referred to as 97 to-up, and conversely, decreasing the lift will be referred to as lift-down.

Next, IJ7 executed in the control unit 25
The operation contents of top-up and lift-down control (lift control) will be explained based on the flowchart in Fig. 10. Lift control includes determining the operating state (steps 41 to 50), setting the target device (steps 51 to 55), and It is broadly divided into drive control to the target device (steps 56 to 70), and the value of 7 lags (Fpos) set according to the following operating conditions (
The actuator 15 is driven so that the target position 1i and the value of the flag (Vpos) indicating the actual position of the cam control shaft 11 correspond as shown in the table below.

Here, the values 1 to 4 of the 7-lag F pos are basically set as shown in FIG. 6 in accordance with the engine speed NE and the throttle valve opening C■. In addition, the values 1 to 6 of the 7-lag V pos are determined by the rotation devices θ1 to θ6 (e
The cam surfaces 8F to 8A correspond in the order of 1 to θ6. ) is a value obtained by converting the output value of the bontensimeter (the actual device of the cam control shaft) into a digital value.

That is, if the value of F pos and the value of V pos do not correspond as shown in the table above, the actuator 1 is
5 is driven (steps 56-69). In addition, it is determined whether the lift is up or down based on the value of the 7 lag Fth, and the lift 7 is adjusted by rotating the 7 cutter 15 clockwise.
) or rotating to the left (lift down).

In addition, the driving letter written in the table above! ! ! For detection of I~■, the 9th
As shown in the figure, various sensors M17 to M21 (rotation speed sensor 17, throttle valve opening sensor 18, neutral switch 20, clutch switch 21) are provided, and the control unit (control unit) 25 is based on these detection signals. The seven cutuators 15 are driven and controlled via the drive circuit 23.

Also, four cam surfaces are sufficient for the four operating states I to ■, but if the lift changes significantly between the idle state I and the starting state ■, it may be necessary to change IJ7. Impact can be prevented by making gradual changes. Therefore, the lift when the value of V pos is 2 or 3 is not used.

(Problem to be solved by the invention) By the way, in such a device, the intake and exhaust valve lift variable fi
The matching between the load torque of the VT and the driving torque of the 7-cut unit (drive means) is performed with the aim of achieving a normally used operating state, so when the normal operating state is removed, the matching between the load torque and the driving torque is also lost, and the 1J7 An operating condition occurs in which the variable @ structure cannot operate normally.

For example, the viscosity of the oil used to lubricate the IJ7 variable mechanism depends on the engine temperature, so when the temperature is so low that the load torque, which increases with the viscosity, exceeds the drive torque of the IJ7 variable mechanism, the IJ7 torque becomes too low. It becomes impossible to drive the variable mechanism.

In addition, if the power supply voltage that determines the drive torque of the actuator drops abnormally, this drive torque will be lower than the load torque of the variable lift mechanism, and the same < 17
7) It becomes impossible to drive the variable mechanism.

First, the valve train 82 structure has a rotation speed range (safe operation range) in which the engine can be operated safely, and it changes depending on the valve speed. This is because the installation of the valve spring 3, which changes depending on the valve position, is no longer able to close the intake valve 2 according to the cam profile when the rotation speed exceeds a predetermined number determined by the load and spring constant. This is because bounce occurs in the intake valve 2, causing the valve closing timing to deviate significantly from the designed value. FIG. 11 shows the safe operation range with respect to engine speed NE and valve lift. The engine speed at the boundary with the dangerous operation area is the smallest when the valve position is at Ll.

Therefore, there will be an operating state in which IJ7 control cannot be performed, so measures must be taken in advance to prevent the engine from being operated in a dangerous operating range. For example, in order to operate the engine within the safe operating area in the figure, it is determined whether the operating state is such that lift control can be performed prior to starting the stop control, and the operating state in which lift control cannot be performed is determined. If the upper limit of the allowable engine speed is limited so that the engine speed does not exceed N1 when it is determined that the engine speed is It is possible to avoid driving in a dangerous driving area.

This invention was made by focusing on the problems of the conventional example, and it is possible to determine whether or not the operating state is such that lift control can be performed prior to lift control, and to determine whether or not the operating state is such that lift control can be performed. It is an object of the present invention to provide a valve lift control device which stops lift control when it is determined that this is the case, and also limits the engine speed.

(Means for solving problems) The present invention is constructed as shown in FIG.

To explain the components of the conventional example first, 80 is a mechanism that makes the intake/exhaust valve 7F characteristic variable, and this lift variable 8! A control system that controls the mechanism 80 is a control system that controls the mechanism 80.
a means 81 for driving this mechanism 80; a means 83 for detecting the actual lift device; and a drive control for the driving means 81 so that the detected actual lift device becomes a target lift device according to the operating state. 84.

Note that the operating state (for example, engine speed and throttle valve opening) is detected by means 82 for detecting the operating state.

In the intake/exhaust valve lift control device for an internal combustion engine configured in this manner, the present invention determines in advance whether or not the operating state is such that lift control of the control means 84 can be normally performed based on the power supply voltage or the engine temperature signal. means 87 for stopping the lift control when it is determined that the operating state is such that the lift control cannot be performed normally; A means 89 for restricting the position is provided.

Note that 85 is means for detecting power supply voltage, and 86 is means for detecting engine temperature.

(Function) With this configuration, 117 points can be changed! Operating conditions in which the relative balance between the dead load torque and the actuator drive torque are disrupted and lift control cannot be performed are when the power supply voltage is abnormally low or at extremely low temperatures. This is determined based on the power supply voltage signal and engine temperature signal, and in this case, lift control is stopped and the engine speed is reduced to 5! limited.

For this reason, since lift control cannot be performed, the valve lift is fixed at either position, and even if the engine speed increases in such a condition, the engine speed is Since the number is limited, this allows safe driving.

This will be explained below using examples.

(Embodiment) FIG. 2 is a block diagram of an embodiment of the present invention.
To begin with the parts similar to the conventional example, 15 is an actuator (for example, a DC motor) that rotationally drives the cam control shaft of the variable intake and exhaust valve lift mechanism, and 23 is an actuator 21.
This is the drive circuit.

In addition, the sensors include a potentiometer 1 meter 19 that detects the actual device of the cam control shaft, a rotation speed sensor 17 that detects the engine rotation speed NE, a throttle valve opening sensor 18 and a neutral switch 20 that detect the throttle valve opening CV. , a clutch switch 21, and signals from these sensors are input to a control unit 25. 22 is an A/D converter.

The control unit 25 drives and controls the seven actuators 15 so that the actual device of the cam control shaft becomes a target device set according to the operating state. This is also carried out in the conventional example, and first we will outline this drive control, that is, the lift control to the target device based on FIG. 3 CB). 50), set the 7-lag F pos to instruct the optimum lift for the determined operating condition (steps 51 to 5).
5) If the value of 7 lag V pos indicating the actual device of the cam control shaft and the value of k F pos do not correspond as shown in the table above, the actuator 15 is rotated clockwise or counterclockwise until they correspond (step 56 ~70). Here, steps 41 to 50 are operating state determination means, and steps 51 to 50 are operating state determination means.
Reference numeral 55 denotes a target device setting means, and steps 56 to 70 function as drive control means, and these means constitute the means 84 shown in FIG. 1 as a whole.

In addition, recently in such cases, the control unit 25
As shown in Figure 2, I: ROM 26, RA
M27, input/output boat 28. Clock 29. CPU3
The flowchart shown in tlS3 (B) also represents the operations executed within the CPU 31.

Next, the characteristic part of this invention is that it is determined based on the power supply voltage or engine temperature signal whether the operating state is such that lift control can be performed normally, and that lift control cannot be performed normally. When it is determined that the engine is in operation, the speed control is stopped and the engine speed is limited.

That is, steps 101 to 107 in FIG. 3(A), which are executed prior to the steps in FIG. 3(B), are newly provided. The rush is a characteristic part of this invention, and step 101.
102 corresponds to the function of means 87 in FIG.
104 corresponds to the function of means 88 in the figure, and step 103, 1
05 corresponds to the function of means 89 in the figure.

First, whether 117 engine control can be performed normally depends on the power supply voltage Vo or engine temperature Tw and their reference value V.
Determined by comparison with a(1,7w6).

In other words, a case in which the 97-tooth control cannot be performed normally is a case in which the relative balance between the load torque of the variable lift FI structure and the drive torque of the 7-cut unit is disrupted.
Specifically, there are cases where the drive torque is less than the load torque and cases where the load torque exceeds the drive torque. The former occurs when the drive torque is lower than the load torque due to an abnormal drop in the power supply voltage Ve, which determines the drive torque of the actuator, and the latter occurs when the drive torque is lower than the load torque due to an abnormal drop in the engine temperature Tw. This occurs when the load torque increases even if the torque is sufficient.

Therefore, if Va≦VBO or Tw≦Tl1IO, it is determined that the lift control cannot be performed normally (steps 101 and 102).

Note that the sensor 32 that detects the power supply voltage Va and the engine temperature T
A sensor 33 for detecting w is provided as shown in FIG. For example, the voltage signal in the control circuit 35 is used as the power supply voltage signal, and the oil temperature or cooling water temperature is used as the engine temperature signal. Note that for convenience, only one of the two may be detected.

When it is determined that the operating state is such that lift control cannot be performed normally, an EM double signal (7 control impossible signal) is output, and the drive of the actuator 15 is stopped (steps 103 and 104). Since it is not possible to change the lift even if the lift control is performed, the subsequent lift control is stopped.

Also, since the '77) control is stopped, there is a possibility that the engine will be operated in a dangerous operating range, so to avoid this, the engine speed is limited (step 103).
, 105), in this example, control is performed to limit the fuel supply amount so as not to exceed the lowest rotational speed Nl among the rotational speeds at the boundary with the dangerous driving region shown in the tlS11 diagram. That is, 35 in FIG. 2 is a fuel supply amount control circuit, and when the EM multiplied signal is output, the fuel supply amount is controlled within this range by setting the upper limit value of the engine speed to N1.

As shown in FIG. 11, the rotation speed at the boundary with the dangerous operation area changes depending on the valve lift.
By changing the upper limit value of the engine speed according to 7F, a wide operating range can be secured. *Also, to limit the number of revolutions, methods such as cutting fuel or cutting off the ignition signal may be used.In short, the upper limit of the number of revolutions can be set to prevent driving into a dangerous driving range. It is sufficient if it is possible to reduce the

Therefore, to explain the effect when configured in this way, for example, if the power supply voltage (8) drops abnormally immediately after starting, or if the engine temperature drops abnormally due to the cold region, the engine may not lift normally. In operating conditions where control cannot be performed, the 177 engine is fixed to one device (for example, the Ll device), and in such cases, changes in operating conditions may cause the rotational speed to rise and enter a dangerous operating range. Conceivable.

On the other hand, in this embodiment, before entering the 1J7 engine control, the power supply voltage Va or the engine temperature Tw is compared with the respective reference value VBo+Tw (1, and Ve≦VBO
Or, if Tw≦Tll1o, it is determined that the lift cannot be changed even if lift control is entered, and therefore the 97-toe control cannot be performed normally, and as a result, the actuator 15 cannot be driven. The amount of fuel supplied to the engine is limited so that the engine is stopped and the engine speed does not exceed N1 (steps 101 to 105).
).

In other words, the variable lift mechanism and actuator itself
Although this is not always the case, there may be a situation where upper lift control is apparently impossible, and even if top control is started, it is not possible to variably control the lift depending on the operating condition. Therefore, the control is stopped without entering lift control to ensure safe operation of the engine.

And of driving! According to the first sequence, the power supply voltage Va recovers to the extent that it exceeds V2O.
After exceeding wo, the EM double signal is canceled (step 1
01, 102, 106), the restriction on the engine speed is lifted and lift control is started (step 10).
7.41 and later), lift control is a control that matches the value of 7 lag F pos set according to the operating condition and the value of 7 lag V pos indicating the actual cam control shaft device as shown in the table above. The actuator is driven in the same manner as in the conventional example (steps 41 to 70) until the values of , F pos and V pos reach the correspondence shown in the table above (steps 41 to 70), thereby improving engine stability in the low speed range and reducing output in the high speed range. You can improve your performance.

(Effects of the Invention) As explained above, in this invention, it is determined whether the operating state is such that lift control can be performed normally based on the power supply voltage or engine temperature signal, and lift control cannot be performed normally. When it is determined that the engine is in an operating state, lift control is stopped and the engine speed is limited, so the engine will not be operated in a dangerous operating range in operating states where 97-tooth control is not possible. Able to operate the engine safely.

[Brief explanation of drawings]

FIG. 1 is a conceptual block diagram of the present invention, FIG. 2 is a block diagram of an embodiment of the present invention, and FIG. 3 (A). FIG. 3(B) is a flowchart explaining the operation contents of this embodiment. Fig. 4 is a vertical cross-sectional view of a conventional intake/exhaust valve lift variable mechanism;
Figure 5 is a plan view, and Figure 6 is a diagram explaining each operating range based on the relationship between engine speed and throttle valve opening, f:t.
FIG. S7 is a diagram similarly showing the lift characteristics, and FIG. 8 is a diagram similarly showing the output characteristics of the potentiometer. FIG. 9 is a block diagram of the engine in the conventional example, FIG. 10 is a flowchart illustrating the operation in the conventional example, and FIG. 11 is a diagram showing the safe operation range with respect to engine speed and valve gear. 1... Intake valve cam, 2... Intake valve, 3... Valve spring, 4... Rocker arm, 4A... Rocker arm back, 6... Lever, 8... Lift 1 control cam,
8A-8F...Cam surface, 10...Coil spring, 11
...Cam control axis, 15...Actuator, 17.
... Rotation speed sensor, 18 ... Throttle valve opening sensor, 19
... Potentiometer, 20 ... Neutral switch, 21 ... Clutch switch, 22 ... A/D
Converter, 23... Drive circuit, 25... Control unit, 26... ROM, 27... RAM, 28
...I10 boat, 29...clock, 31...
CPU, 35...Fuel supply amount control circuit, 80...
Intake/exhaust valve lift variable mechanism, 81...driving means, 82.
... Operating state detection means, 83 ... Device detection means, 84
. . . Control means, 85 . . . Power supply voltage detection means, 86.
... Engine temperature detection means, 87 ... Discrimination means, 88 ...
- Control stop means, 89... Rotation speed limiting means. Patent Applicant: Nissan Motor Co., Ltd. Figure 2 2!5 Figure 4 Figure 5 Figure 6 Figure 7 Crank %l/' - Figure 8 Power At, 'I Rotation angle of the shaft Figure 9

Claims (1)

[Claims] A mechanism for varying the lift characteristics of the intake and exhaust valves, a means for driving the variable lift mechanism, a means for detecting an actual lift device, and a target lift device according to the operating state of the detected actual lift device. In the intake/exhaust valve lift control device for an internal combustion engine, which includes means for driving and controlling the driving means, the control means is in an operating state in which lift control of the control means can be normally performed based on a power supply voltage or an engine temperature signal. a means for determining whether or not lift control is being performed normally; a means for stopping lift control when it is determined that the operating state is such that lift control cannot be performed normally; and a means for stopping engine rotation when it is determined that the operating state is such that the What is claimed is: 1. An intake and exhaust valve lift control device for an internal combustion engine, comprising: means for limiting.