JPH0245002B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable valve control device for an internal combustion engine that adjusts the opening/closing timing and lift amount of intake and exhaust valves in accordance with the rotational speed of the internal combustion engine.

In this type of variable valve control device, a camshaft is provided with a high-speed cam and a low-speed cam, and a cam follower connected to a valve lifter is selectively brought into sliding contact with both cams depending on the engine speed. By adjusting the opening/closing timing and lift amount of the intake and exhaust valves to suit high-speed rotation, it is possible to improve engine output and reduce fuel consumption.

By the way, if the engine is started immediately before the key switch is turned off, the engine will stop with the cam follower moved to the high-speed cam side, and the next time the engine is started, it will start smoothly. fuel is wasted.

In particular, when hydraulic pressure is used to move the cam follower, the hydraulic pressure is low during idling immediately after starting the engine, so the output of the hydraulic cylinder is not large enough, making it impossible to move the cam follower. As a result, the engine does not run smoothly and fuel is wasted.

The present invention aims to solve the above-mentioned problems by equipping a variable valve control device with a mechanism that automatically moves the cam follower to the low-speed cam side even if it is on the high-speed cam side when the engine is stopped. The goal is to achieve the following objectives.

To explain the structure of the present invention, a high-speed cam 12 and a low-speed cam 11 are provided on a camshaft C of an internal combustion engine. Valve lifter means 2 changes the opening/closing timing and lift amount of the exhaust valve, and electricity is supplied from an on-vehicle battery 9 via a key switch 8, and the valve lifter means 2 changes to the high-speed cam 1 according to the rotational speed of the internal combustion engine.
In a variable valve control device for an internal combustion engine, the variable valve control device for an internal combustion engine is equipped with a switching means 6 for selectively moving the key switch 8 into contact with the low-speed cam 11. A delay means 73 directly supplies power from the on-vehicle battery 9 to the switching means 6, and when the delay means 73 is activated, the valve lifter means 2 is unconditionally moved to come into contact with the low speed cam 11 with respect to the switching means 6. The selection signal control means 7 outputs a signal.

According to this configuration, for example, even if the key switch 8 is turned off immediately after starting the engine, power is supplied to the switching means 6 for a certain period of time, and the output signal from the selection signal control means 7 disables the valve lifter means 2. The low-speed cam 11 is moved back according to the conditions, and the next engine start can be performed smoothly.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure and operation of the present invention will be explained below with reference to illustrated embodiments.

Figure 1 shows the overall configuration of the variable valve control device. In the figure, 11 and 12 are low-speed cams and high-speed cams, respectively, which are formed on the camshaft C, and are adapted to the low-speed rotation and high-speed rotation of the engine, respectively. It has a profile that allows the valve lift amount and valve opening/closing timing of the intake or exhaust valve to be obtained. 2 is a valve lifter mechanism, 31 is a hydraulic cylinder that switches the valve lifter mechanism 2 to one of the cams 11 and 12, 32 is a four-way switching electromagnetic valve that switches the oil flow to reciprocate the hydraulic cylinder 31, and 33 is a hydraulic pressure linked to the engine. a pump; 6 is a switching circuit that outputs a switching signal to the electromagnetic valve 32 according to the engine speed; 7 is a switching circuit that detects the failure of the key switch and delays the failure of the battery power supply; a selection signal control circuit for outputting a switching signal to the low-speed cam 11;
is the key switch, and 9 is the battery.

The figure shows the valve lifter mechanism 2 viewed from above. A cylindrical rocker shaft 21 is provided parallel to the camshaft C, and a bush 2 is attached to the outer periphery of the shaft.
3 is fitted rotatably and slidably in the axial direction. A cam follower 22 and an arm 24 are located at radially symmetrical positions of the bush 23, respectively.
The cam follower 22 and arm 24 can swing around the rocker shaft 21. A cylindrical valve lifter 25 is disposed at the tip of the arm 24 so as to be movable in the vertical direction, and the tip of the arm 24 is brought into contact with the upper end surface of the valve lifter 25. On the other hand, the cam follower 22 is brought into sliding contact with the high-speed cam 12 provided on the camshaft C.

When the camshaft C and the cam 12 attached thereto rotate as the engine rotates, the cam follower 22 moves up and down according to the profile of the cam 12. This up and down movement is transmitted to the valve lifter 25 by the arm 24, and the lifter It opens and closes an intake valve or an exhaust valve (not shown) connected to 25.

The bush 23 has a built-in ball 27 which is biased toward the axial center by a spring member 26.
By fitting the ball 24 into grooves 21a and 21b provided on the outer peripheral surface of the rocker shaft 21,
The bushes 23 are positioned at positions corresponding to the low-speed cam 11 and the high-speed cam 12, respectively.

A rod 311 extending from the hydraulic cylinder 31 is inserted into the rocker shaft 21.
Spring members 28a and 28b are provided around 1. These spring members 28a and 28b are connected to the rod 311.
One end is fixed to the retainer 312a, 312b fixed to the rod 311, and the opposite end is a ring 313a, 313 provided so as to be slidable along the rod 311.
It is locked to b. A pin 29 is passed through the side wall of the bush 23, and the shaft 2
1, and its tip is located between the rings 313a and 313b.

When the rod 311 of the hydraulic cylinder 31 moves to the left, the spring member 28a expands.
b is compressed, and as a result, the bush 23 receives a force to the left via the pin 29. When this force becomes larger than the spring force of the spring member 26 that positions the bush 23, the bush 23, the cam follower 22 integrally connected thereto, and the arm 24
quickly moves to the left, the ball 27 fits into the groove 21a, and the bush 23 is positioned at a position corresponding to the low speed cam 11. This movement is performed at a portion where the profiles of the high-speed cam 12 and the low-speed cam 11 match.

The solenoid valve 32 includes a pressure oil supply pipe 33a through which oil fed by a hydraulic pump 33 flows, and an oil pan 34.
A return pipe 33b that returns oil to the hydraulic cylinder 31
Oil guide pipes 32a and 32b are connected thereto. Further, the solenoid valve 32 is connected to the output signal line 6 of the switching circuit 6.
a and 6b, and are connected to both ends of a solenoid valve coil (not shown).

When a current output from the signal line 6a toward the signal line 6b is generated from the switching circuit 6, the solenoid valve 32 brings the supply pipe 33a and the oil guide pipe 32a into conduction, and the return pipe 33b and the oil guide pipe 32b, respectively. As a result, the rod 311 of the hydraulic cylinder 31 moves to the right,
High speed cam 12 is selected. When the switching circuit 6 generates a current output in the opposite direction to the above, the solenoid valve 3
2 connects the supply pipe 33a and the oil guide pipe 32b and the return pipe 33b and the oil guide pipe 32a, respectively, and as a result, the rod 311 of the hydraulic cylinder 31 moves to the left and the low speed cam 11 is selected.

41 and 42 are gears and coils that constitute the rotation speed sensor. Each tooth of the gear 41 is magnetized, and as the gear rotates, the magnetized teeth sequentially approach the coil 42, and a voltage is induced in the coil 42. , this pulse voltage is input to the switching circuit 6 via the signal line 42a.

5 is an oil temperature detection sensor using a thermistor, which shows a resistance value proportional to the oil temperature, and its output is connected to the signal line 5a.
The signal is input to the switching circuit 6 at .

The battery 9 is connected to the selection signal control circuit 7 and one end of the key switch 8 by a signal line 9a.

The other end of the key switch 8 is connected to the control circuit 7 through a signal line 8a.

Furthermore, the switching circuit 6 and the control circuit 7 are connected to the signal line 7
They are connected by a and 7b.

FIG. 2 shows an example of the switching circuit 6. 60 in the diagram
1 is a waveform shaping circuit, 602 is an F/V conversion circuit, 6
03, 604, 605 are comparison circuits, and the circuit 60
When the input voltage is higher than the reference value, the output of circuit 3, 605 becomes "1" level, and when the input voltage is lower than the reference value, the output of circuit 604 becomes "1" level. Reference numerals 610 and 611 are low-pass filters, and 613 and 616 are R-S flip-flops composed of NOR gates. The flip-flop 616 is for inhibiting the output of an erroneous signal when the power is turned on. 606 is an oscillation circuit, 60
7, 614, 615, and 617 are binary counters, and the counter 607 frequency-divides the output of the oscillation circuit 606 inputted to the terminal C and outputs a clock pulse from the terminal Q. Counter 614, 615, 617
So, when the input of terminal R is at the "1" level, the output of the terminal Q connected to the terminal C becomes the "0" level, the input of the terminal R becomes the "0" level, and a predetermined number of pulses are input to the terminal CE. Then the output of terminal Q becomes "1"
level.

618 is an initial reset circuit which outputs a reset pulse when the power is turned on. 619 is a transistor
The driver circuit consists of Tr1, Tr2, Tr3, Tr4, Tr5, and Tr6, and the coil 3 of the switching solenoid valve 32
The solenoid valve 32 is actuated by issuing a current output to 21.

When the engine starts and the oil temperature rises, the resistance value of the oil temperature sensor 5 decreases, and the signal voltage input through the signal line 5a increases, and the comparator circuit 60
5 outputs a "1" level signal and AND gates 608 and 609 open. When the engine speed increases in this state, the coil 42 of the rotation speed sensor
The frequency of the pulse appearing on the signal line 42a connected to the signal line 42a increases, the output voltage of the converter 602 increases, and the comparison circuit 603 outputs a "1" level signal. The flip-flop 613 is set by this signal and its output goes to the "1" level, and the OR gate 621 outputs the counter 61.
A pulse with a predetermined width set in step 5 is output. Flip-flop 616 is set at the same time as flip-flop 613. While the pulse is being output from the OR gate 621, the transistors Tr1, Tr2, and Tr3 of the driver circuit 619 are turned on, and the solenoid valve coil 321 is connected from the signal line 6a to the signal line 6b.
Current flows towards. As a result, the oil passage is switched as described above, the rod 311 (see FIG. 1) moves to the right, and the high speed cam 12 is selected.

When the engine speed decreases, the converter 602
The output voltage becomes smaller, and the comparator circuit 604 outputs a "1" level signal. This signal is AND
It is input to the flip-flop 613 via the gate 609 and the OR gate 612.
13 is reset, its output becomes "0" level, and the counter 61 is output from the AND gate 620.
A pulse with a predetermined width set in step 4 is output. While this pulse is being output, the driver circuit 619
transistors Tr4, Tr5, and Tr6 turn on,
The solenoid valve coil is now connected from signal line 6b to signal line 6.
The current flows towards a, the oil path is switched again, the cylinder rod 311 moves to the left, and the low speed cam 1
1 is selected.

FIG. 3 shows a circuit example of the selection signal control circuit 7.
In the figure, 71 is a relay, 72 is a constant voltage power supply circuit, and 73
is a CR delay circuit that performs a delay operation when the input changes to the "0" level. 74 is a relay driver circuit, and 75 is a switching circuit.

The signal line 7b is the power supply line to the switching circuit 6 (see Figure 2), and the signal line 7a is the OR line of the switching circuit 6.
It is connected to gate 612.

When the key switch 8 (see FIG. 1) is turned on, battery voltage is applied to the switching circuit 75 via the signal line 8a, whereby the circuit 75 is activated and the output of the signal line 7a becomes the "0" level. At the same time, the driver circuit 74 is activated via the delay circuit 73, the relay 71 is excited, and the battery power on the signal line 9a is input to the power supply circuit 72 via the contact of the relay 71, where the voltage is converted and the signal is It is supplied to the switching circuit 6 by line 7b.

When the key switch 8 is turned off, the battery voltage appearing on the signal line 8a disappears and the switching circuit 7
5 is immediately turned off. On the other hand, the signal line 8a
Even after the battery voltage disappears, the driver circuit 74 continues to operate for a while due to the delay circuit 73.
Battery power is supplied to the switching circuit 6 through the signal line 7b. Since the switching circuit 75 is in the OFF state, the levels of the signal line 7a and the signal line 7b are equal, and the signal line 7a is at the "1" level while the battery power is supplied. During this time, the signal line 7a
The flip-flop 613 of the switching circuit 6 shown in FIG. 2 is unconditionally reset by the "1" level signal of the AND gate 6.
20 outputs a pulse, and a current flows through the electromagnetic coil 321 from the signal line 6b to the signal line 6a,
The oil passage is switched by the switching solenoid valve 32 (see Fig. 1), and the cylinder rod 311 moves to the left.
While the engine is rotating due to inertia, the cam follower 22 is brought into sliding contact with the low speed cam 11.

As described above, in the variable valve control device of the present invention, when the key switch is turned off, the cam follower is brought into sliding contact with the low-speed cam regardless of the engine speed immediately before turning off, so that the engine can be started smoothly the next time. , and there is no wastage of fuel.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the overall configuration of the present invention, FIG. 2 is a circuit diagram of a switching circuit, and FIG. 3 is a circuit diagram of a selection signal control circuit. C...Camshaft, 11...Low speed cam, 1
2...High-speed cam, 2...Valve lifter mechanism (valve lifter means), 22...Cam follower, 23
...Button, 24...Arm, 25...Valve lifter, 31...Hydraulic cylinder, 32...Switching solenoid valve, 33...Hydraulic pump, 41...Gear (engine speed sensor), 42...Coil (engine rotation speed sensor), 6... switching circuit (switching means), 7
...Selection signal control circuit (selection signal control means), 7
3...Delay circuit (delay means), 8...Key switch, 9...Vehicle battery.

Claims (1)

[Claims] 1. A high-speed cam and a low-speed cam provided on the camshaft of an internal combustion engine, and a valve lifter means that comes into contact with one of these cams and operates by following the cam surface to change the opening/closing timing and lift amount of the intake and exhaust valves. and a switching means that is supplied with power from an on-vehicle battery via a key switch and selectively moves the valve lifter means into contact with the high-speed cam or the low-speed cam depending on the rotational speed of the internal combustion engine. In the variable valve control device, a delay means detects failure of the key switch and directly supplies power from the on-vehicle battery to the switching means for a certain period of time after the failure, and the switching means when the delay means is activated. A variable valve control device for an internal combustion engine, comprising selection signal control means for outputting a signal for unconditionally moving the valve lifter means into contact with a low-speed cam.