JPH063125B2 - Valve timing control device for internal combustion engine - Google Patents

Description

The present invention relates to an apparatus capable of performing multi-step valve timing control according to engine operating conditions.

There are various types of variable valve timing mechanisms. For example, there is a variable valve timing mechanism provided with a pair of slits in proximity to the inner sleeve on the camshaft side and the outer sleeve on the timing pulley side according to the applicant's proposal. The pair of slits extend in directions inclining to each other and a roller bearing is installed in the slit. The roller bearing is carried by a cylindrical moving body that is movable in the cam shaft direction.
The rotary drive motor is connected to the movable body via a rotary motion-linear motion conversion means including a screw portion on the output shaft and a nut engaged with the screw portion. Depending on the direction of rotation of the motor controlled by the control circuit, the roller bearing moves in the direction of the cam axis in the cross slit, which causes relative rotation of the pair of sleeves. As a result, the valve timing is
The motor changes in two steps between the rotation limit position in one direction and the rotation limit position in the other direction.

In the prior art, the valve timing obtained by the variable valve timing mechanism was only two stages. However, it is difficult to obtain the optimum valve timing according to the operating conditions of the engine simply by changing the valve timing in two steps. An object of the present invention is to improve such a conventional technique and to enable precise control of valve timing in multiple stages.

A valve timing control device for an internal combustion engine according to the present invention comprises a variable valve timing mechanism and a control circuit, and the variable valve timing mechanism includes a step motor driven by a control signal from the control circuit and a rotational movement of the step motor. Motion-linear motion conversion means for converting the linear motion into a linear motion along the axis of the cam shaft, and a rotary driven member that is rotatably provided coaxially with the cam shaft and coupled to the crank shaft in response to the linear motion. Of the diagonal angle control means for controlling the valve timing as a relative angular position with respect to the cam shaft, the relative angle control means being provided coaxially with the cam shaft on a rotary driven member connected to the crank shaft. An outer sleeve to be connected, an inner sleeve arranged coaxially with the outer sleeve and connected to a cam shaft, the outer sleeve and the sleeve. A pair of slits formed in the inner sleeve so as to intersect each other, a roller bearing located in the slits, and a reciprocating movement in a direction along the axis of the cam shaft by being connected to the rotary motion-linear motion converting means. The step motor controls the valve timing by the relative angle control means in multiple stages via the rotational movement-linear movement conversion means in response to a control signal from the control circuit. The control circuit stores a valve timing representative value, which is obtained by the relative angle control means and is determined as a relative angular position of the rotary driven member with respect to the cam shaft, according to each operating condition of the engine, A valve timing in which the valve timing representative value corresponding to a specific operating condition is stored in the storage means while the engine is operating. Means for calculating as the target value, means for detecting the actual measured value of the valve timing representative value during the operation of the engine, and the deviation between the calculated target value of the valve timing representative value and the actually measured valve timing representative value. And a means for supplying control signals to the step motor by the number of pulses corresponding to the deviation.

In the operation of the present invention, the target value of the valve timing according to the operating condition detected by the engine is calculated from the value stored in the storage means, and the deviation of this target value from the measured value is calculated, and this deviation is eliminated. The step motor is controlled so that As a result, it is possible to precisely control the valve timing in multiple stages according to the operating conditions of the engine. Referring to the attached drawings, 1 is a cylinder block, 2 is a cylinder head, 3 is a cylinder head cover,
Reference numeral 4 is an intake pipe, 6 is a throttle valve, and 8 is an exhaust pipe. 1
Reference numeral 0 denotes a crankshaft, which is connected to a piston 14 via a connecting rod 12. A cam 20 is formed on the cam shaft 18, and the cam 20 acts on the intake valve 24 and the exhaust valve 25 via the rocker arms 22 and 23 against the valve spring 26. A timing pulley 28, which serves as a rotationally driven member, is located at one end of the cam shaft 18, and is wound around a pulley 32 on the crank shaft 10 via a timing belt 30. The timing pulley 28 and the cam shaft 18 are connected by the variable valve timing mechanism 34 according to the present invention.

The structure of the variable valve timing mechanism 34 is shown in FIG. According to the present invention, the variable valve timing mechanism 34 includes a step motor that receives a control signal from a control circuit described later, and a rotary motion-straight line that converts the rotary motion of the step motor into a linear motion along the axis of the cam shaft. As a relative angular position with respect to the cam shaft, the motion converting means and the rotationally driven member (timing pulley 28 in the embodiment) rotatably provided coaxially with the cam shaft and coupled to the crank shaft in response to the linear motion. And a relative angle control means for controlling the valve timing. First, the relative angle control means will be described. The inner sleeve 36 is fixed to the cam shaft 18 by the bolt 37 once. The timing pulley 28 is mounted on the inner sleeve 36 by the bearing 3
Mounted by 9. An outer sleeve 38 extends integrally from the boss portion of the timing pulley 28 so as to be coaxial with the inner sleeve 36. Inner sleeve 36
And the outer sleeve 38 are in close proximity to the slits 40 and 4
2 is provided. As shown in FIG. 3, one side 40 is straight but the other side 42 is inclined, and as a result, they are in a relationship of intersecting with each other. Bearings 44 and 46 are located in the slits 40 and 42, respectively. Bearings 44 and 46
Are axially supported on a shaft portion 48 'that integrally extends in the radial direction from a cylindrical moving body 48 that reciprocates along the direction of the cam shaft. The inner sleeve 36, the bolt 37, the bearing 39, the outer sleeve 38, the slits 40 and 42, the bearings 44 and 46, and the moving body 48 described above constitute the relative angle control means of the present invention.

Reference numeral 50 is a step motor, which is connected to the moving body 48 via a rotary motion-linear motion conversion means. This rotational movement-
The linear motion converting means is constructed as a so-called recirculating ball screw. That is, the output shaft of the motor 50
Externally threaded on 50 ', endlessly internal threaded on nut 52, and ball 54 is located between these threads. A guide rod 51 extending from the housing of the motor 50 is fitted in a cam shaft direction guide groove 52 'formed in a nut 52. With this structure, the output shaft 5 of the motor 50
It will be apparent that the rotational movement of 0'is converted into a linear movement of the nut 52. The nut 52 is connected to the moving body 48 via a bearing 55, and the bearings 44 and 46 are driven in the cam shaft direction.

Reference numeral 56 denotes a case, which is temporarily fixed to the hub portion of the timing pulley 28 by a bolt 57 and is rotatably connected to the motor housing by a bearing 58 at the other end. A timing belt cover 59 accommodates the timing belt 30 including the variable valve timing mechanism 34 of the present invention.

The rotation of the crankshaft 10 is transmitted to the timing pulley 28 via the timing pulley 32 and the timing belt 30. The rotation of the timing pulley 28 is transmitted to the shaft portion 48 'through a roller bearing 46 located in the slit 42 of the outer sleeve 38 which is integral with the timing pulley 28. Shaft 4
The rotation of 8'is transmitted to the inner sleeve 36 from the roller bearing 44 positioned in the slit 40, and the cam shaft 18
Is driven to rotate. When the cam 20 on the cam shaft 18 reaches the mountain, the valve 2 is moved through the rocker arms 22 and 23.
The stems of Nos. 4 and 25 are pushed and the valves 24 and 25 are opened against the valve spring 26. Step motor 50
Is driven, its output shaft 50 'rotates and the nut 52 moves in the A or B direction in FIG. Therefore, the roller bearings 44 and 46 provided on the shaft of the moving body 48 that moves together with the nut 52 also move in the respective slits 40 and 42 in the same direction. Since the slits 40 and 42 intersect each other as shown in FIG. 3, the linear movement of the bearings 44 and 46 in the cam axis direction causes the relative rotation of the inner sleeve 46 and the outer sleeve 38 in the C or D direction of FIG. Is converted to. Therefore, the inner sleeve 36 that is the driven side
The outer sleeve 38 on the drive side of the cam shaft 18 connected to the above, that is, the timing pulley 28 and the crank shaft 10
The phase for changes. Therefore, the valves 24 and 25
The valve timing, which is the crank angle position when the cam 20 acts on the valve, becomes variable. The valve timing is determined according to the position of the moving body 48 in the cam axis direction, in other words, according to the rotation angle of the step motor 50 from the origin position.

Although it is clear that the valve timing that continuously changes according to the rotation of the motor 50 can be taken by the above-described structure, the present invention pays attention to this and changes the rotation angle of the step motor according to the engine operating condition, The valve timing is controlled in multiple stages, and the principle is as follows. That is, the valve timing is determined by the operating conditions of the engine, for example, the engine speed N _e , the intake pipe pressure P _b representing the load, the water temperature THW, etc. For example, regarding N _e and P _b , the contour lines are as shown in FIG. It changes according to V ₁ , V ₂ , ... The present invention aims to control the valve timing so as to exactly match FIG. That is, contour lines as shown in FIG. 4 are stored as a table in the memory of the computer, and the number of revolutions N _e actually measured during the operation of the engine,
One point in the table is calculated and set as the target valve timing position from the intake pipe pressure P _b, etc., and the deviation between this target value and the actual valve timing position is calculated, and the step motor 50 is rotated by a step corresponding to the deviation. Let
As a result, the valve timing is always maintained at the target value. A configuration for realizing such rotation control of the step motor will be described below.

Reference numeral 60 denotes a control circuit for performing valve timing control according to the present invention, which has a function as a microcomputer. Signals from various operating condition detection sensor groups are input to the control circuit 60. The intake pipe pressure sensor 62 is provided in the intake pipe 4 and detects the intake pipe pressure P _b . The rotation speed sensor 64 generates a pulse signal according to the position of the detection piece 64 'provided on the crankshaft. A water temperature sensor 66 is provided at the cylinder block 1 to detect the cooling water temperature.

The control circuit 60 processes signals from these sensor groups 62, 64, 66 and forms a drive signal for the step motor 50.

FIG. 5 shows a schematic block diagram of the control circuit 60. The input / output port 68 is the intake pipe pressure sensor 62,
It receives signals from the rotation speed sensor 64 and the water temperature sensor 66. The output port 70 is connected to the stator coil of the step motor 50 via the latch circuit 72 and the gate 74. Although not shown, the step motor 50 has a plurality of exciting coils and sequentially selects the exciting coils to be magnetized to rotate in a predetermined direction for each step. Gate 7
4 has a role of selecting a part of the exciting coils to be magnetized from such a plurality of exciting coils. The latch circuit 72 also has a function of receiving a command from the microcomputer for a signal for rotating the step motor in a predetermined direction by one step and holding the command until the rotation of the step motor is completed. Incidentally, regarding the detailed structure of the step motor 50,
It will not be described in detail here because it is irrelevant to the features of the present invention. Please refer to the attached description and drawings.

The input / output ports 68 and 70 are connected by a bus 80 to the components of a microcomputer system, such as a micro processing unit 82 (MPU) and a read-on memory 84.
(ROM), connected to random access memory 86 (RAM). Reference numeral 88 is a clock signal generator (CLOCK). ROM8
A routine for realizing the valve timing switching control of the present invention as outlined above is stored in a program 4 in the form of a program. The MPU 82 performs valve timing control according to the stored contents of the ROM 84. This program is shown as a flowchart in FIG. 6, and this flowchart will be described step by step below.

In FIG. 6, reference numeral 96 indicates the start of this routine, which is an interrupt routine executed at predetermined time intervals. This time interval is set to a time sufficient to complete the step motor 50 after receiving a command to rotate the step motor 50 one step. When this interrupt request is input to the MPU 82, it is determined at 95 whether the step ON flag is 1 or not. This flag is a flag that is set during the control of the valve timing, that is, during the rotation of the step motor, and is initially 0. Therefore, 9
The determination in 8 is N ₀ , and subsequently in 100, the target value V _step of the valve timing under each operating condition is calculated. That, MPU 82 is speed N _e of the data from the intake pipe pressure P _b of the data and the rotational speed sensor 64 from the pressure sensor 62 that is stored in a predetermined area of the RAM 86, even water temperature THW from the water temperature sensor 66 Capture data. The contour data as shown in FIG. 4 is stored in the ROM 84 as a table, and the MPU 82 determines the target valve timing at that time from the measured pressure P _b and rotation speed N _e data, for example, from the reference position of the step motor. Calculate as rotation angle V _step .
Then, make the necessary corrections according to the water temperature THW at that time.

At the next step 104, the MPU 82 takes in the current rotational angle position V _posit of the step motor stored in the predetermined area of the _{RAM 86} and subtracts it from the target value V _step calculated as described above. The subtraction result STEP represents the deviation of the valve timing from the target value as the number of steps in which the step motor should rotate.

At 106, it is determined whether STEP = 0. If Yes, it is recognized that the valve timing has not deviated from the target value, and the routine branches to 108 and returns to the main routine. If No, it is considered that the valve timing has deviated from the target value,
After the step 0N flag is set at 109, step 110 is entered. At 110, it is determined whether STEP> 0. If Yes, it is recognized that the step motor 50 should be corrected to rotate in the normal direction, and at 112, the rotation direction flag is displayed.
Set DIR to “0”. On the other hand, if No, it is recognized that the step motor 50 should be corrected in the reverse direction, and the rotation direction indicating flag DIR is set to "1" at 114. In this case 10
Since the step number STEP to rotate the step motor calculated in step 4 is negative, the absolute value is taken and converted to a positive sign in step 116.

In the next step 118, it is determined whether DIR is 1 or not. If Yes, the step motor 50 should be rotated in the reverse direction, and the reverse rotation process is performed at 120. MPU82 is output port 70
A digital signal for reversing the step motor by one step from the current position is written in. The written content is held by the latch circuit 72, the gate 74 is opened and closed according to the content of the latch circuit 72, and each exciting coil of the step motor 50 is excited so as to reverse one step from the current position.

If the determination at 118 is No, the step motor 50 should rotate in the normal direction, and the normal rotation process is performed at 122. That is,
A digital signal that causes the step motor 50 to rotate forward one step from the current position appears at the output port 70, the latch circuit 72 holds the content, and the gate starts to rotate the step motor forward one step.

When the interrupt is next started, the step ON flag is 1 in 98, so that it is determined to be Yes, and the process proceeds to 130, where one obtained by subtracting 1 from STEP is set as STEP. At 132
It is judged whether or not STEP = 0, and if it is not 0, it branches to No.
The following processing is performed.

When the step motor is rotated by the number of steps matching the deviation calculated in 104, the determination result in 132 is Yes.
And proceed to 134. At 134, the MPU 82 sends a command to the output port 70 to stop the step motor at that position, the latch 72 holds its contents, and the gate 74 is driven to hold the step motor 50 at that position. 136 indicates the resetting of the step ON flag.

As described above, in the present invention, the valve timing can be precisely controlled by the step motor according to the operating conditions, and the output can be improved while maintaining the high fuel consumption rate.

[Brief description of drawings]

FIG. 1 is an overall schematic view of an internal combustion engine according to the present invention, FIG. 2 is a detailed sectional view of a variable valve timing mechanism in a cam axis direction, FIG. 3 is a view in the direction of arrow III in FIG. 2, and FIG. FIG. 5 is a diagram showing required characteristics of valve timing with respect to a combination of rotation speed and intake pipe pressure, FIG. 5 is a block diagram of a control circuit, and FIG. 6 is a flow chart showing a software configuration of the present invention. 10 ... Crank shaft, 18 ... Cam shaft, 24 ... Intake valve, 25
... Exhaust valve, 34 ... Variable valve timing mechanism, 36 ... Inner sleeve, 38 ... Outer sleeve, 40, 42 ... Slit, 44, 46 ... Roller bearing, 50 ... Step motor, 60 ... Control circuit, 62 ... Pressure sensor, 64 …
Rotation speed sensor, 66 ... Water temperature sensor.

Claims (1)

[Claims] 1. A variable valve timing mechanism and a control circuit, wherein the variable valve timing mechanism drives a step motor driven by a control signal from the control circuit, and rotates the step motor along the axis of the cam shaft. And a relative angle with respect to the cam shaft of the rotationally driven member which is converted into a linear motion and linearly moving conversion means, and which receives the linear motion and is rotatably provided coaxially with the cam shaft and connected to the crank shaft. A relative angle control means for controlling the valve timing as a position, the relative angle control means being provided coaxially with the cam shaft, and an outer sleeve connected to a rotary driven member connected to the crankshaft; An inner sleeve coaxially arranged with the outer sleeve and connected to the cam shaft, and an inner sleeve and an inner sleeve so as to intersect with each other. A pair of slits formed, a roller bearing positioned in the slit, and a rotary motion-linear motion conversion means are connected to carry the roller bearing so as to be capable of reciprocating in a direction along the axis of the cam shaft. The step motor controls the valve timing by the relative angle control means in multiple stages via the rotary motion-linear motion conversion means in response to a control signal from the control circuit, and the control circuit comprises: Storage means for storing the valve timing representative value determined by the relative angle control means, which is determined as the relative angular position of the rotary driven member with respect to the cam shaft, in accordance with each operating condition of the engine, and its specification during operation of the engine. A valve timing representative value corresponding to the operating condition of is calculated as a target value from the valve timing value stored in the storage means. A stage, means for detecting an actual measured value of the valve timing representative value during operation of the engine, means for calculating a deviation between the calculated target value of the valve timing representative value and the actually measured valve timing representative value, A valve timing control device for an internal combustion engine, comprising: means for supplying a control signal to the step motor by the number of pulses corresponding to the deviation.