JPH0583723B2 - - 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 sleeper on the camshaft side and an outer sleeper 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 should change depending on the operating condition of the engine. 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 timing based on the valve timing control signal from the control circuit. However, at startup, the battery voltage drops due to the load on the starter during cranking, so the motor is unable to obtain the desired driving force, and even if the control circuit attempts to control the valve timing, the valve timing cannot be adjusted. It could not be controlled to the desired value, and there was a risk that controllability would deteriorate.

This invention aims to prevent fluctuations in valve timing during startup in an internal combustion engine equipped with a variable valve timing mechanism, and its solution is to prohibit valve timing control during startup when battery voltage drops.

The valve timing control device 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 that receives a control signal from the control circuit, and an output shaft of the electric drive means. a transmission means for transmitting motion in a direction parallel to the axis of the camshaft; a transmission means connected to the transmission means and rotatably provided coaxially with the camshaft;
and a relative angle control means for controlling the valve timing as a relative angular position of a rotary driven member connected to the crankshaft with respect to the camshaft, and the electric drive means controls the electric drive means in response to a control signal from the control circuit. The control circuit controls the valve timing by the relative angle control means in multiple stages through means, and the control circuit includes means for detecting the engine rotation speed, and a rotation speed considerably lower than the idle rotation speed but higher than the cranking rotation speed. means for determining whether or not the rotation speed is at least a predetermined value; and a control signal for the variable valve timing mechanism so that the valve timing becomes a predetermined value determined according to operating conditions when the rotation speed is determined to be at least the predetermined value. and means for forming a control signal to the variable valve timing mechanism so that the valve timing is maintained at a fixed value regardless of engine operating conditions when the rotational speed is determined to be below a predetermined value.

In the operation of the present invention, when the engine is started, the engine speed is detected, and when the engine speed is below a predetermined value, the valve timing is fixed at a certain value.

When the engine speed exceeds a predetermined value, the valve timing is controlled in multiple stages according to the operating state.

In the present invention, when the engine speed is lower than a predetermined value, variable valve timing control is prohibited and the valve timing is fixed at a certain value, so when the battery voltage is low, such as during cranking at a low engine speed. This has the effect of preventing deterioration of controllability due to insufficient driving force of the electric drive means, which may occur if the electric drive means is operated without valve timing control being performed during the operation. .

Referring to the attached 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. A crankshaft 10 is 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 is located 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 as a rotationally driven member and the camshaft 18 are connected by a variable valve timing mechanism 34 according to the present invention.

The configuration of the valve timing control device 34 is shown in FIG. Variable valve timing mechanism 34
According to the present invention, the electric 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 electric drive means in a direction parallel to the axis of the camshaft. , connected to the transmission means and rotatably provided coaxially with the camshaft,
It is comprised of a relative angle control means for controlling valve timing as a relative angular position of a rotary driven member (timing pulley 28 as described above in the embodiment) connected to the crankshaft with respect to the camshaft. First, the relative angle control means will be explained. An under sleeve 36 is fixed to one end of the camshaft 18 with a bolt 37. The timing pulley 28 has a bearing 3 on this inner sleeve 36.
Attached by 9. timing pulley 28
An outer sleeve 38 extends coaxially with the inner sleeve 36 from the boss portion thereof.
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. Bearings 44 and 46 are located within the slits 40 and 42, respectively. The bearings 44 and 46 are connected to a shaft portion 4 that integrally extends in the radial direction from a cylindrical moving body 48 that reciprocates along the direction of the camshaft.
8'. In the above embodiment, the inner sleeve 36, bolt 37, bearing 39, outer sleeve 38, slits 40, 42, bearings 44, 46, and 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 ball screw. That is, an external thread is cut on the output shaft 50' of the motor 50, an endless internal thread is cut on the nut 52, and a ball 54 is located between these threads. A guide rod 51 extending from the housing of the motor 50 is fitted with a guide groove 52' in the direction of a camshaft formed in a nut 52. It will be clear that with such a structure, the rotational movement of the output shaft 50' of the motor 50 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, and variable valve timing mechanism 3 of the present invention
The timing belt 30 including timing belt 4 is housed therein.

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 intersect with each other as shown in the third slit, the linear movement of the bearings 44 and 46 in the camshaft direction is limited to the inner sleeve 3.
6 and the outer sleeve 38, C or D in FIG.
Converted to relative rotation in direction. Therefore, the phase of the camshaft 18 connected to the inner sleeve 36 on the driven side with respect to the outer sleeve 38 on the driving side, that is, the timing pulley 28 and the crankshaft 10 changes. Therefore, the valve 24,
The valve timing, which is the crank angle position when the cam 20 acts on the valve 25, is variable. The valve timing is determined by the moving body 48 in the camshaft direction.
In other words, it is determined 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 depends on engine operating conditions,
For example, it is determined by the engine speed N _e , the intake pipe _pressure P _b representing the load, the water temperature THW, etc.
Regarding P _b , 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 valve timing is set, the deviation between this target value and the actual valve timing position is calculated, and the step motor 50 is rotated by steps corresponding to the deviation, thereby constantly maintaining the valve timing at the target value. be. Also, when starting the engine, since the cranking speed is low, precise control cannot be achieved. Since it is difficult to initialize the valve timing at startup, such valve timing is initialized when the engine is stopped, and when the engine speed is low at startup, no valve timing control as described above is performed. If not, the valve timing is maintained at its initialized value.

A control circuit 60 performs valve timing control according to the present invention by driving the variable valve timing mechanism 34, and 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 _Pb . 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 port 68 is connected to an intake pipe pressure sensor 62, a rotation speed sensor 64, and a water temperature sensor 6.
Receives signal from 6. The output port 70 is connected to the stator coil of the step motor 50 via a latch circuit 72 and a gate 74. 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 a signal from the microcomputer to rotate the step motor 50 one step in a predetermined direction, and holds the command until the step motor completes rotation. The detailed structure of the staple 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 the patent application filed by the applicant in
Please refer to the description and drawings attached to the application in No. 8147 (see JP-A-57-124047).

90 is a relay that controls the operation of the control circuit, and has a contact 90-1 that supplies power B to the control circuit. Further, the excitation coil 90-2 is connected to the output port 70. The relay 90, as described later,
It is turned ON while the engine is running, and turned OFF when initialization is performed after the engine has stopped.

Input port 68 and output port 70 are bus 80
A microprocessing unit 82, which is a component of a microcomputer system by
(MPU), read-only memory 84 (ROM), and random access memory 86 (RAM). 88 is a clock signal generator (CLOCK). The ROM 84 stores software in the form of a program that implements the valve timing switching control of the present invention as outlined above. MPU
82 according to the storage contents of the ROM 84,
Valve timing control including initialization processing of the present invention is executed. This program is shown as a flowchart in FIG. 6, and this flowchart will be explained step by step below.

In FIG. 6, 100 indicates that this routine is a time interrupt routine that is executed at predetermined time intervals. When the MPU receives an interrupt request, the next 1
In step 02, the controller checks the RAM 86 area that records whether the engine's ignition switch is on or off, and determines whether the ignition switch is on or not. If Yes, the process goes to 103 and it is determined whether the engine speed is higher than the engine speed during cranking and considerably lower than the idling speed, for example, 400 rpm. When higher than 400 rpm, the engine is determined to be running and goes to 104 to perform normal valve timing control. That is, based on the engine operating status signals from the water temperature sensor 66, rotational speed sensor 64, and pressure sensor 62, a target valve timing value at that time is calculated using a table, and the calculated target value is compared with the actually measured valve timing. The deviation is calculated, and the step motor 50 is rotated by the number of steps corresponding to the deviation in the direction to eliminate the deviation. In step 104, the excitation coil 50-
1, . . 50-n (the current state of the latch circuit 72), the latch 72 is set to the next state which causes the step motor 50 to rotate one step in the direction of eliminating the deviation, Then, the magnetization state of the excitation coils 50-1,...50-n is 1.
The step motor 50 is changed to execute step rotation, and the step motor 50 is changed to perform step rotation.
executes the one-step rotation. This process is repeated every time the routine shown in FIG. 5 is performed, and finally the deviation becomes 0, and the valve timing is controlled according to the engine operating conditions. 106 indicates resetting the INI flag.

If the ignition switch is not turned on at 102 (No), it is determined that the engine is stopped, and the next 10
In step 8, the initialization flag INI is tested. Since this flag INI is held at "0" at 106 during operation, the determination result at 104 immediately after the stop is No, and the process branches to 109. At 109, the initialization flag INI is set. Next, at step 110, the setting position of the valve timing at startup (this valve timing is on the most delayed side, but for convenience, at this time, the step motor is rotated as forward as possible and the movable body 48 is moved to the far right in Fig. 2). The deviation STEP with respect to the rotation angle V _ppsit of the step motor at the valve timing at the time when the ignition switch is determined to be OFF is calculated with respect to the rotation angle MAX of the step motor in the state (2). In the next 112, what was calculated in this 110 is 20
The addition of steps is called STEP. That is, 11
It is theoretically possible to drive the moving body 48, that is, the roller bearings 44 and 46, from the valve timing position at stop to the valve timing position at start by rotating the step motor by the number of steps calculated in Look at it and add only 20 steps. Therefore, this value of 20 is merely an example and has no limiting meaning. In the next step 114, the MPU 82 outputs a digital signal to the output port 70 that causes the step motor to rotate forward by one step, and the content thereof is held by the latch 72. The gate 74 is turned on and off according to the contents of the latch 72, and as a result, each excitation coil 50-1, ..., 50-n of the step motor 50 is driven so that the step motor 50 rotates one step in the forward direction. be done.

When the next interrupt starts, the judgment result at 108 is Yes because INI=1, and the next 11
In step 6, the current STEP minus 1 is set as STEP. At step 118, it is determined whether or not this STEP is 0. If it is determined not to be 0 (No), the program proceeds to step 114 and causes the step motor 50 to rotate one step as before.

When the moving body 48 rotates by the number of steps set in step 112, the movable body 48 is positioned to the far right in FIG. 2 until it hits the stopper, and at this time the valve timing becomes the most retarded side. When the initialization process is completed in this way, the determination in 118 is STEP = 0 (Yes)
Then, proceed to step 120. The MPU 82 sends a signal to the output port 70 to demagnetize the excitation coil of the relay 90 and turns off the contact 90-1.
Therefore, the power supply to the control circuit 60 is canceled.

At the next restart, the ignition switch is turned, the determination in step 102 is Yes, and the process proceeds to step 103.
In this case, when cranking, the engine speed is
If it is less than 400r.pm, the judgment will be No and the process will return to the main routine without doing anything. The valve timing at this time is a value on the retarded side set by the initialization process of 102 or less. Therefore, startability is ensured, and even if the battery voltage drops due to the load on the starter during cranking,
Valve timing never goes out of order.

[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 cross-sectional view of the variable valve timing mechanism in the camshaft direction, Fig. 3 is a directional view of Fig. 2, and Fig. 4 shows the required characteristics of valve timing for combinations 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 a control circuit that controls the movement of the output shaft of the electric drive means. a transmission means for transmitting transmission in a direction parallel to the axis of the camshaft; a transmission means connected to the transmission means and rotatably provided coaxially with the camshaft;
a relative angle control means for controlling valve timing as a relative angular position of a rotary driven member connected to a crankshaft with respect to a camshaft; The control circuit controls the valve timing by the relative angle control means in multiple stages through means, and the control circuit includes means for detecting the engine rotation speed, and a rotation speed considerably lower than the idle rotation speed but higher than the cranking rotation speed. means for determining whether or not the rotation speed is at least a predetermined value; and a control signal for a variable valve timing mechanism so that the valve timing becomes a predetermined value determined according to operating conditions when the rotation speed is determined to be at least the predetermined value. and means for forming a control signal to a variable valve timing mechanism so that a fixed valve timing is maintained regardless of engine operating conditions when the rotational speed is determined to be below a predetermined value. valve timing control device.