JPH0480202B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device capable of performing multi-stage valve timing control according to engine operating conditions.

There are various types of variable valve timing mechanisms, such as one proposed by the present applicant in which a pair of slits are provided adjacent to an inner sleeve on the camshaft side and an outer sleeve on the timing pulley side. The pair of slits extend in directions that are inclined to each other, and a roller bearing is installed within the slits. The roller bearing is supported by a cylindrical moving body that is movable in the camshaft direction.
The rotary drive motor is connected to the movable body through a rotary motion-to-linear motion conversion means consisting of a threaded portion on its output shaft and a nut that engages with the threaded portion. Depending on the direction of rotation of the motor controlled by the control circuit, the roller bearing moves in the direction of the camshaft within the intersecting slits, causing relative rotation of the pair of sleeves. As a result, the valve timing changes in two stages between the maximum rotational position of the motor in one direction and the maximum rotational position in the other direction.

If equipped with a variable valve timing mechanism,
Valve timing is not constant and changes depending on the engine operating condition. That is, the variable valve timing mechanism includes a drive means such as an electric motor that receives a control signal from a control circuit, and the drive motor controls the valve timing to a desired valve timing based on the valve timing control signal from the control circuit. However, if the buckling voltage falls below the specified value, the electric motor will not be able to obtain sufficient driving force, and the valve timing set by the control circuit will not be obtained, which may cause the valve timing to fluctuate.

An object of the present invention is to prevent fluctuations in valve timing regardless of a decrease in battery voltage.

To achieve this object, the valve timing control device for an internal combustion engine of the present invention includes a variable valve timing mechanism and a control circuit, and the variable valve timing mechanism includes an electric drive means receiving a control signal from the control circuit. , a transmission means for transmitting the motion of the output shaft of the electric drive means in a direction parallel to the axis of the camshaft, and a transmission means connected to the transmission means and rotatably provided coaxially with the camshaft and connected to the crankshaft. a relative angle control means for controlling valve timing as a relative angular position of a rotationally driven member relative to the camshaft; The valve timing by the relative angle control means is controlled in multiple stages, and the control circuit includes means for determining whether or not the power supply voltage is at least a predetermined value; means for forming a control signal to the electric drive means so as to obtain valve timing according to the operating conditions of the electric drive means; means for forming a control signal to the drive means.

In the operation of the present invention, when the battery voltage decreases, the valve timing is controlled to the most delayed side. In other words, when the valve timing is on the most delayed side, the effective compression ratio is the smallest, so even if the battery voltage is low, the valve timing can be reliably controlled and ultimately maintained at this valve timing. This makes it possible to prevent fluctuations in valve timing.

Referring to the accompanying drawings, 1 is a cylinder block, 2 is a cylinder head, 3 is a cylinder head cover, 4 is an intake pipe, 6 is a throttle valve,
8 is an exhaust pipe. 10 is a crankshaft connected to a piston 14 via a connecting rod 12. A cam 20 is formed on the camshaft 18, and the cam 2
0 is connected to the intake valve 2 via the rocker arms 22 and 23.
4. Acts on the exhaust valve 25 against the valve spring 26. A timing pulley 28 as a rotation ratio driving member is positioned at one end of the camshaft 18 so as to be relatively rotatable, and is wound around a pulley 32 on the crankshaft 10 via a timing belt 30. The timing pulley 28 and the camshaft 18 are connected by a variable valve timing mechanism 34 according to the present invention.

The configuration of the variable valve timing mechanism 34 is shown in FIG. Variable valve timing mechanism 34
According to the present invention, the motor-driven drive means receives a control signal from a control circuit 60, which will be described later, and the transmission means transmits the movement of the output shaft of the motor-driven drive means in a direction parallel to the axis of the camshaft. , valve timing as a relative angular position with respect to the camshaft of a rotating driven member (timing pulley 28 in the embodiment) connected to the transmission means, rotatably provided coaxially with the camshaft, and connected to the crankshaft; and relative angle control means for controlling the angle. First, the relative angle control means will be explained. An inner sleeve 36 is fixed to one end of the camshaft 18 with a bolt 37. The timing pulley 28 is mounted on the inner sleeve 36 by a bearing 39. An outer sleeve 38 extends coaxially with the inner sleeve 36 from the boss portion of the timing pulley 28 . Inner sleeve 36 and outer sleeve 38 have adjacent slits 40 and 42. As shown in FIG. 3, one of them 40 is straight, while the other 42 is slanted, so that they cross each other. Slits 40 and 4
Bearings 44 and 46 are located within 2, respectively. The bearings 44 and 46 are 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 camshaft.
The inner sleeve 36, bolt 37, bearing 39, outer sleeve 38, slit 40, 4
2, the bearings 44, 46, and the moving body 48 constitute the relative angle control means of the present invention.

Reference numeral 50 denotes a step motor as an electric drive means, which is connected to the movable body 48 via a transmission means.

This transmission means is constructed as a so-called recirculating pole screw. That is, motor 5
An external thread is cut on the output shaft 50' of 0, and a nut 5
2 has an endless internal thread, and a ball 54 is located between these threads. A guide rod 51 extending from the housing of the motor 50 is fitted into a camshaft guide groove 52' formed in the nut 52. Due to this structure, the output shaft 5 of the motor 50
It will be clear that the rotational movement of 0' is converted into a linear movement of the nut 52. The nut 52 is connected to the movable body 48 via a bearing 55, and the bearings 44 and 46 are driven in the camshaft direction.

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

The rotation of the crankshaft 10 is controlled by the timing pulley 3.
2. It is transmitted to the timing pulley 28 via the timing belt 30. The rotation of the timing pulley 28 is transmitted to the shaft portion 48' via a roller bearing 46 located within a slit 42 of an outer sleeve 38 integral with the timing pulley 28. The rotation of the shaft portion 48' is transmitted to the inner sleeve 36 from the roller bearing 44 located in the slit 40, and the rotation of the cam shaft 1 is transmitted to the inner sleeve 36.
8 is rotationally driven. When the cam 20 on the camshaft 18 reaches the peak, it pushes the stems of the valves 24, 25 via the rocker arms 22, 23, and opens the valves 24, 25 against the valve spring 26.

When the step motor 50 is driven, its output shaft 50' rotates and the nut 52 moves in the direction A or B in FIG. Therefore, the roller bearing 44 provided on the shaft of the movable body 48 that moves together with the nut 52
and 46 also have respective slits 40 and 42 in the same direction.
move within. Since the slits 40 and 42 cross each other as shown in FIG.
The linear motion in the camshaft direction is converted into relative rotation between the inner sleeve 36 and the outer sleeve 38 in the direction C or D in FIG. 3. Therefore,
Outer sleeve 38 on the driving side of the camshaft 18 connected to inner sleeve 36 on the driven side
That is, the timing pulley 28 and the crankshaft 10
The phase relative to changes. Therefore, valve 2
The valve timing, which is the crank angle position when the cam 20 acts on the valves 4 and 25, is variable. The valve timing is determined according to the position of the movable body 48 in the camshaft direction, in other words, according to the rotation angle of the step motor 50 from the reference position.

It is clear that the above-mentioned structure allows valve timing to be continuously changed according to the rotation of the motor 50, but the present invention focuses on this and changes the rotation angle of the step motor according to the engine operating conditions. We are trying to control valve timing in multiple stages, and the principle is as follows. In other words, valve timing is determined by engine operating conditions, such as engine speed N _e , intake pipe pressure P _b representing the load, water temperature THW, etc. For example, N _e and P _b
Regarding, as shown in Figure 4, the contour lines v ₁ , v ₂ ,...
It changes according to. The contour lines shown in Figure 4 are stored in the computer memory as a table, and a point in the table is calculated as the target valve timing position based on the rotational speed N _e , intake pipe pressure P _b, etc. actually measured during engine operation. The deviation between this target value and the actual valve timing position is calculated, and the step motor 50 is rotated by the number of steps corresponding to the deviation, whereby the valve timing can always be maintained at the target value. can.
In this case, when the voltage of battery B is low, there is a risk of malfunction even if the above-mentioned control is performed. Therefore, in the present invention, the battery voltage is constantly monitored to see if it is above a predetermined value, and if it is true, the above-mentioned control is performed, but if it is not, this control is not performed and the valve timing is set to a fixed value, for example, the most delayed. The timing is set accordingly. A configuration for realizing such rotational control of the step motor will be described below.

A control circuit 60 performs such valve timing control and functions 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
Detect. The rotation speed sensor 64 generates a pulse signal depending on the position of a detection piece 64' provided on the crankshaft. Further, a water temperature sensor 66 is provided at the cylinder block 1 to detect the cooling water temperature.

The control circuit 60 includes these sensor groups 62, 64,
The signal from 66 is processed to form a drive signal for step motor 50.

FIG. 5 schematically shows the control circuit 60 as a block diagram. The input/output port 68 receives signals from the intake pipe pressure sensor 62, 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 a latch circuit 72 and a gate 74. Although not shown, the step motor 50 has a plurality of excitation coils, and rotates in a predetermined direction step by step by sequentially selecting the excitation coils to be magnetized. The gate 74 has the role of selecting a part of the excitation coils to be magnetized from among the plurality of excitation coils. The latch circuit 72 also receives instructions from the microcomputer regarding the direction in which the step motor 50 should rotate and the number of steps it should rotate, and has the role of outputting an opening/closing command for the gate 74 according to a predetermined sequence to execute the instructions. . The detailed structure of the step motor 50 is not related to the features of the present invention, so it will not be described in detail here, but if necessary, please refer to Japanese Patent Application No. 56-8147 filed by the present applicant. Please refer to the description and drawings attached to the application (see Publication No. 124047).

Input/output ports 68 and 70 are connected by bus 80 to microprocessing unit 82, which is a component of a microcomputer system.
(MPU), read-only memory 84 (ROM), and random access memory 86 (RAM). 88 is a clock signal generator (CLOCK). The ROM 84 stores a routine in the form of a program that implements the valve timing switching control of the present invention as outlined above. MPU82
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 explained step by step below.

In FIG. 6, 94 indicates the start of this routine, which is an interrupt routine executed at predetermined time intervals.

This interrupt interval is set to a time sufficient for the step motor 50 to fully implement the command after receiving the command to rotate one step.

When this time interrupt request is received by the MPU 82, this interrupt routine is executed and first the step ON flag is determined, and if No, the routine advances to 98. At step 98, the MPU 82 takes in the voltage data of the battery B stored in a predetermined area of the RAM 86, and determines whether the voltage is larger than a predetermined value, for example, 10V.
If Yes, consider it normal and proceed to 102. At 102, a valve timing target value Vstep is calculated. That is, the MPU 82 receives the intake pipe pressure from the pressure sensor 62 stored in a predetermined area of the RAM 86.
P _b data and rotation speed from rotation speed sensor 64
N _e data, as well as the water temperature from the water temperature sensor 66
Import THW data. The ROM84 contains the fourth
The contour line data as shown in the figure is recorded as a table, and the MPU 82 uses the actually measured pressure P _b and rotation speed.
From the data of _Ne , the target valve timing at that time is calculated as, for example, the rotation angle Vstep of the step motor from the reference position. Then, necessary corrections are made according to the water temperature THW at that time.

In the next step 104, the MPU 82 takes in the current rotational angular position Vposit of the step motor stored in a predetermined area of the RAM 86, and subtracts it from the target value Vstep calculated as described above. This 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.

In 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 process branches to 108 and returns to the main routine. If No, it is considered that the valve timing is deviated from the target value, and after setting the step ON flag to 1, the program enters step 110. In 110, it is determined whether STEP>0. If Yes, it is recognized that the step motor 50 should be corrected in the direction of forward rotation, and the rotation direction indicator flag DIR is set at 112.
Set to “0”. If no, it is recognized that the step motor 50 should be corrected in the reverse direction, and 114
Set the rotation direction display flag DIR to "1".

In this case, the number of steps STEP that the step motor should rotate, calculated in 104, is negative, so
116 takes the absolute value and converts it to a positive sign.

In the next step 118, it is determined whether DIR is 1 or not. If Yes, the step motor 50 should be reversed, and the reversal process is performed in step 120. The MPU 82 writes a digital signal to the output port 70 to reverse the step motor by one step from the current position. This written content is held in a latch circuit 72, and the gate 74 is opened and closed according to the content of the latch circuit 72, and each excitation coil of the step motor 50 is excited so as to be reversed by one step from the current position.

If the determination in step 118 is No, the step motor 50 should rotate in the normal direction, and the normal rotation process is performed in 122. That is, a digital signal appears at the output port 70 to rotate the step motor 50 one step forward from the current position, the latch circuit 72 holds its contents, and the gate 74 is opened and closed to rotate the step motor one step forward from the current position. .

Next time the interrupt is started, the 96 will step
Since the ON flag is 1, it is judged as Yes and 130
, and here subtract 1 from STEP.
STEP. At 132, it is determined whether STEP=0 or not, and if it is not 0, the process branches to No, and the processing from 118 onwards is performed.

When the step motor rotates by the number of steps corresponding to the deviation calculated in step 104, the determination result in step 132 becomes Yes, and the process proceeds to step 134. 134 has MPU8
2 sends a command to the output port 70 to stop the step motor 50 at that position, the latch 72 holds its contents, and the gate 74 stops the step motor 50 at that position.
is driven to hold it in that position.

136 indicates the reset of the step ON flag.

If it is determined in step 98 that the battery voltage is below a predetermined value, the process branches to No. Next, at 140, the target value Vstep of the valve timing is set to 0, that is, the valve timing on the delayed side when the movable body 48 has moved to the leftmost position in FIG. Therefore, by executing the routine 104 and below, the step motor 50 is reversed by the number of steps to that position.

As described above, in the present invention, the valve timing can be optimally set by driving the step motor according to the engine operating conditions, and such control is not performed when the battery voltage is low.
By setting the value to a fixed value on the delay side, it is possible to prevent error movement and prevent deterioration of engine performance.

[Brief explanation of drawings]

FIG. 1 is an overall schematic diagram of an internal combustion engine according to the present invention. FIG. 2 is a detailed sectional view of the variable valve timing mechanism in the camshaft direction. FIG. 3 is a view taken in the direction of the arrow in FIG.
The figure is a diagram showing the required characteristics of valve timing for the combination of engine speed and intake pipe pressure.
FIG. 5 is a block diagram of the control circuit, and FIG. 6 is a flowchart showing the software configuration of the present invention. 10... Crankshaft, 18... Camshaft, 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. Consisting of a variable valve timing mechanism and a control circuit, the variable valve timing mechanism includes an electric drive means that receives a control signal from the control circuit, and controls the movement of the output shaft of the electric drive means. Relative to the camshaft of a transmission means that transmits transmission in a direction parallel to the axis of the camshaft, and a rotating driven member that is connected to the transmission means, is rotatably provided coaxially with the camshaft, and is connected to the crankshaft. and a relative angle control means for controlling valve timing as an angular position, and the electric drive means controls the valve timing by the relative angle control means in multiple stages via the transmission means in response to a control signal from the control circuit. The control circuit includes means for determining whether the power supply voltage is at least a predetermined value, and a means for determining whether the power supply voltage is at least the predetermined value, and a means for determining valve timing according to engine operating conditions when the power supply voltage is determined to be at least the predetermined value. means for forming a control signal to the electric drive means at the same time; and means for forming a control signal to the electric drive means so as to obtain the most delayed valve timing when the power supply voltage is determined to be below a predetermined value. A valve timing control device for an internal combustion engine consisting of: