JPH0315006B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a valve timing control device for an internal combustion engine having a valve timing switching mechanism.

There are some systems in which the valve timing of an internal combustion engine is changed according to its operating conditions. In a typical example, valve timing is set in two stages, one for low speeds and one for high speeds, and operating condition factors such as throttle valve opening and engine speed are detected to drive the control circuit. The control circuit is constituted by a microcomputer system, and is adapted to obtain valve timing in accordance with operating conditions according to a program stored in its memory.

An object of the present invention is to provide a safety device that prevents the system from running out of control when an abnormality occurs in the computer during valve timing switching using such program control. In order to achieve this object, the present invention is provided with a monitoring means for detecting normal or abnormal operation of the computer, and when a signal indicating abnormal operation of the computer is received from the monitoring means, the valve timing switching motor is controlled by the computer. A circuit is provided that simultaneously disables the operation and drives the motor so that the valve timing becomes one of the two valve timings, for example, the low-speed valve timing.

To explain with reference to the drawings below, in Fig. 1,
1 is an air cleaner, 3 is a throttle valve, 5 is a surge tank, and 8 is an intake manifold. 10 is the main body of a so-called DOHC type engine, in which a pulley 14 on a crankshaft 12 is connected by a belt 16 to a pulley 20 on an intake camshaft 18 and a pulley 24 on an exhaust camshaft 22.
Note that 25, 25', and 25'' are idlers.A valve timing control member 28 is attached to the intake camshaft 18.
This member 28 is connected to a crank 31 via a link 30. The crank 31 is connected to the output shaft of a drive motor 32. motor 3
2, the crank 31 rotates, and this rotational motion is transmitted to the valve timing control member 28 via the link 30, which rotates clockwise or counterclockwise. Therefore, the intake camshaft 1
The relative angular position of 8 to the exhaust camshaft 22 changes, and the valve timing changes in two stages.
For convenience of explanation later, it is assumed that the position where the valve timing control member 28 has rotated the most clockwise in the figure (corresponding to one dead center of the crank 31) provides valve timing suitable for low speeds, and this will be hereinafter referred to as this position. This is called slow valve timing. Further, the position where the valve timing control member 28 has rotated the most in the counterclockwise direction in the figure (corresponding to another dead center of the crank 31) provides valve timing suitable for high-speed operation, and this is referred to as high-speed valve timing. to be called.

A control circuit 36 functions as a programmable microcomputer, and receives signals from a sensor 38 such as a throttle positioner that detects the opening degree of the throttle valve 3 and an engine rotation speed sensor 40. In response to these signals, the control circuit 36 forms a drive signal for the valve timing switching motor 32.

FIG. 2 is a block diagram showing the configuration of the control circuit 36. The throttle valve opening sensor 38 applies a signal to the input/output port 46 via the A/D converter 44, and the rotational speed sensor 40 directly applies a signal to the input/output port 46. The motor drive circuit 48 is a relay coil 48
1. Relay contact 482 and power transistor 4
83 and a backflow prevention diode 484. The power supply (+B) is connected to the collector of the transistor through the coil 481 and to the motor 3 through the contact 482.
Connected to 2.

50 is a logic circuit that controls the operation of the motor drive circuit depending on whether the computer is operating normally or abnormally, and includes one OR gate 501 and two AND gates.
Gates 502, 503 and two inverters 50
It consists of 4,505. The output of the OR gate 501 is connected to the base of the transistor 483, one input of the gate is connected to the output of the AND gate 502, and the other input is connected to the output of the AND gate 503.
One input of AND gate 502 is connected to input/output port 46 .

54 is a sensor that detects two valve timings to be switched by the valve timing control member 28, and includes a rotating contact 541 and a fixed contact 5.
42,543,544. The rotating contact 541 is fixed to the output shaft of the motor 32. An intermediate stationary contact 54 in contact with a constantly rotating contact 541
3 is grounded. Fixed contacts 542 and 544, which detect whether the camshaft 18 is in the low speed position or the high speed position, have their tips disposed at positions diametrically opposed to the rotating contact 541. The rotating contact has a notch 541' at one location on its circumference, and this notch 54
1' is a low-speed valve timing detection contact 54 when the valve timing control member 28 comes to the low-speed valve timing position, which is the most clockwise rotated position in FIG.
Come to the tip of 2. In addition, the notch 541'
When the valve timing control member 28 reaches the high-speed valve timing position rotated most counterclockwise in FIG. 1, the high-speed valve timing detection contact 54 is activated.
Come to the tip of 4.

Fixed contacts 542 and 544 as angular position detection sensor members of the camshaft 18 are connected to the voltage connection circuit 6.
Connected to 0. This voltage connection circuit 60 includes voltage dividing resistors 601 and 60 that supply voltage Vc to the valve timing position detection contacts 542 and 544, respectively.
1', 602, 602' and backflow prevention diode 6
03,604 and noise prevention capacitor 605,6
It consists of 06. Each partial pressure point is buffer 62,
64 to the input/output port 46, and applies a position detection signal for the camshaft 16 as described below.

The input/output port 46 is a CPU 66, ROM 68, RAM 7 as components of the microcomputer.
0 via a bus 72. 74 is a clock generation circuit. The ROM 68 stores a program for driving the motor 32 to switch between high-speed valve timing and low-speed valve timing depending on engine operating conditions.

62 is a means for monitoring the operating state of the microcomputer provided according to the present invention, which always outputs a High signal when the microcomputer is normal;
This circuit outputs a low signal when an abnormality occurs. A retriggerable multivibrator can be used as such a circuit. Since the CPU 66 outputs a pulse signal at predetermined time intervals during its normal operation, the multivibrator 62 is constantly triggered and its output is always High. When an abnormality occurs, no such pulse signal is generated, so no trigger occurs and the output becomes Low. Monitoring circuit 62 is connected to the other input of AND gate 502 and to the first input of AND gate 503 via inverter 504 . The second input of the AND gate 503 is connected via an inverter 505 to a line leading to a contact 542, which is a sensor member that detects that the camshaft 18 is in a low-speed valve timing state.

To describe the operation of the present invention, during normal operation of the computer, the output port 46 outputs pulse signals at predetermined intervals as shown in FIG.
The retriggerable multivibrator as No. 2 continues to output a high signal as shown in the letter "m".
It is applied to one input of AND gate 502 and to inverter 504 . Low at inverter 504
Since the output of AND gate 503 is inverted, Low always appears at the output of AND gate 503. from multivibrator
When the computer is operating normally and the high signal continues to be output, the computer performs valve timing switching operations as described below. This operation is stored in memory or ROM 68. A simplified diagram of this program structure is shown in FIG. 4. That is, 70 indicates the start of the program,
At 72, it is determined whether or not the valve timing is in the operating range for high speed operation based on the signal from the throttle valve opening sensor 38 and the signal from the engine speed sensor 40. If Yes, that is, if it is recognized that the operation should be performed at high-speed valve timing, the line from the sensor member 544 that checks whether the camshaft 18 is located in the high-speed valve timing state at 74 is High.
Detect whether or not. If camshaft 18
If the contact point 544 is not at the high speed position, the tip of the contact point 544 does not reach the notch 541', and a Low signal is input to the input/output port 46. In this case, the process branches to No, and the CPU 66 outputs a High signal to the AND gate 502 via the input/output port 46 at 76 . As mentioned above, since the multivibrator 62 outputs a high signal during normal operation of the computer, the AND gate 502 applies a high output to the OR gate 501. Thus, OR gate 501 is
It outputs High and turns on the transistor 483.
When the transistor 483 is turned on, the relay coil 481 is excited, the contact 482 is turned on, and the motor 32 is driven. The crank 31 rotates, and thus the camshaft 18 rotates counterclockwise. When the crank reaches the dead center, that is, the camshaft 18
comes to the high speed position, the notch 5 of the rotating contact 541
41' comes at the tip of contact 544. Then, a High signal is output, and it is judged as Yes at 74 in FIG.
Apply the signal. Therefore, the AND gate is Low
The output of
stops.

The flow of the program when switching the valve timing to high speed has been described above, but the same applies when switching to low speed. That is, if the determination is No at 72, that is, the engine is in the region where it should be operated at low speed valve timing, the camshaft 18 is determined at 80.
A sensor member 5 that detects that the is in the low speed position
Check whether the 42 line is High. If No is detected, the motor is driven at 76. If the valve timing has already been switched to low speed, 80 is Yes.
If so, the process goes to 78 and the drive of the motor 32 is stopped.

If there is an abnormality in the operation of the computer as described above, the supply of pulse signals from the CPU 66 to the multivibrator 62 is interrupted as shown at l' in FIG. 3.
Therefore, the multivibrator applies a low signal like m' to the AND gate 502, and as a result,
AND gate 502 outputs a low signal regardless of other input signals. Therefore, the valve timing switching operation by the computer is not performed.
The low signal from the multivibrator is inverted to high by the inverter 504 and then passed to the AND gate 503.
is applied to one input of If the valve timing is not at the low speed valve timing at this time, the line connected to the sensor member 542 will be
A low output is applied to the inverter 505, and an inverted high signal is applied to the AND gate 503. Therefore, AND gate 503 is turned on,
A high signal is applied to the OR gate 501. Thus, OR gate 501 causes transistor 483
is turned on and the motor 32 is rotated. When the camshaft 18 is rotated to the low speed valve timing position, the tip of the contact 542 comes to the notch 541' and applies a High signal to the inverter 505. Therefore, the low signal from the inverter
It is applied to AND gate 503 and turns it off. Therefore, the motor 32 is stopped and the valve timing is maintained at low speed.

As described above, according to the present invention, it is possible to detect whether the computer's operation is normal or abnormal, and if it is determined to be abnormal, the valve timing is maintained at one of the two valve timings, for example, for low speed, thereby preventing runaway when the computer is abnormal. It can be held down.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the internal combustion engine of the present invention, FIG. 2 is a block diagram of the control circuit in FIG. 1, FIG. 3 is a timing chart explaining the operation of the computer operation monitoring circuit, and FIG. FIG. 3 is a flowchart showing processing performed by a computer. 3...Throttle valve, 8...Intake manifold,
DESCRIPTION OF SYMBOLS 10...Engine body, 18...Intake camshaft, 28...Valve timing control member, 30...
...Link, 31...Crank, 32...Motor,
36... Control circuit, 40... Rotation speed sensor, 48
... Motor drive circuit, 54 ... Camshaft position detection sensor, 62 ... Monitoring circuit.

Claims (1)

[Scope of Claims] 1. A valve timing control member that is connected to a camshaft of an internal combustion engine and is rotatable between a plurality of angular positions; a position detection means for detecting the angular position of the valve timing control member; and a valve timing control member. an electric drive means for imparting a rotational motion to the engine; an operating condition detection means for detecting engine operating conditions; a signal for receiving a signal from the operating condition detection means and outputting a signal for operating the electric drive means; A control means for rotating a valve timing control member to a valve timing position detected by a sensor, a monitoring means for detecting whether the control means is operating normally or abnormally, and a control means for controlling the control means when an abnormality in the control means is detected by the monitoring means. means for disabling the actuation signal from the electrical drive means; and means for disabling the actuation signal from the electrical drive means such that when the disabling means is actuated, the valve timing control member assumes a selected one of the plurality of angular positions. A valve timing control device for an internal combustion engine, comprising a second control means for outputting an actuation signal.