JPH0321726B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a variable control device for changing the operating characteristics of an intake valve region or an exhaust valve stepwise in accordance with the rotational speed of an internal combustion engine.

<Prior art> In order to supply the air-fuel mixture to the combustion chamber and discharge the combustion gas according to a predetermined cycle,
A combustion chamber of a cycle engine includes an intake valve and an exhaust valve, and both of these valves are normally biased in the closing direction by a valve spring provided so as to surround a valve stem. Furthermore, both of these valves are forcibly pushed open against the biasing force of the valve spring mentioned above by a cam that is integrally installed on a camshaft that is connected and driven from the engine's crankshaft using a belt, pulley, etc. It is made possible to do so.

On the other hand, multiple intake valves or exhaust valves are provided for each cylinder, and one intake valve or exhaust valve is operated during low-speed operation, and all valves are operated during high-speed operation, and at the same time, the operation timing of these valves is adjusted according to the rotation of the engine. A technique for improving the filling efficiency of the air-fuel mixture into the combustion chamber over a wide operating range by changing the speed according to the speed is disclosed, for example, in Japanese Patent Application Laid-Open No. 1983-1991 by the present applicant.
It has been proposed in publications such as Publication No. 19911.

By the way, it is conceivable to use lubricating oil pumped by an oil pump connected to the crankshaft of the engine as a power generation source for driving such a variable valve operating characteristic control device. As is well known, this lubricating oil pressure increases almost in proportion to the increase in engine rotational speed, so the actuator that uses this lubricating oil operates by turning off the oil pressure at low speeds and turning it on at high speeds. It is thought that it is common to define it as an action. Therefore, it is considered preferable that the operation of the variable valve operating characteristic control device be made compatible with low speed ranges when the oil pressure is turned off, and compatible with high speed ranges when the oil pressure is turned on.

<Problems to be Solved by the Invention> However, due to a malfunction in the hydraulic circuit or hydraulic-related control equipment, sufficient hydraulic pressure is not applied even in the engine's high-speed rotation range, causing the switching device to become inoperable. If a situation arises in which the engine is operated in a low-speed range mode, the ignition timing and air-fuel ratio balance may deviate significantly from the appropriate values, causing engine malfunction.

In view of the problems of the prior art, the main object of the present invention is to provide an internal combustion engine that can maintain a relatively stable operating state even when an abnormality occurs in a hydraulic circuit or hydraulic-related control equipment. An object of the present invention is to provide a variable valve operating characteristic control device for an engine.

<Means for Solving the Problems> According to the present invention, this purpose is achieved by installing a valve at the intake port or exhaust port of the combustion chamber, which is normally biased to close by a spring means, and which is synchronized with the crankshaft. The valve operating characteristics of the intake valve or exhaust valve, which is driven to open by a rotating cam, are divided into a first state that is suitable for low-speed operation of the engine and a second state that is suitable for high-speed operation of the engine.
This is a variable valve operating characteristic control device for an internal combustion engine for selectively switching stepwise between the following states by hydraulic drive: and an accumulator, wherein the first state is selected when hydraulic pressure is applied to the variable control device, and the second state is selected when hydraulic pressure is not applied to the variable control device. This is achieved by providing a variable valve operating characteristic control device for an internal combustion engine.

<Function> In this way, by accumulating pressure in the accumulator so as to maintain a predetermined pressure at all times, it is possible to supply the necessary hydraulic pressure regardless of the engine rotation speed, and it is possible to supply the necessary hydraulic pressure regardless of the engine rotation speed. The valve operating characteristic variable control device can be operated even if the valve operating characteristic variable control device is used. When the hydraulic pressure to the variable control device is completely cut off, the valve actuation timing suitable for the high speed range is selected.

<Examples> Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1, the internal combustion engine body (not shown) is provided with a pair of intake valves 1a, 1b. A pair of low-speed cams 3a, 3b and a single high-speed cam 4 having an oval cross section are integrally provided on a camshaft 2 that is synchronously driven at a speed of
The opening/closing operation is performed by the first to third rocker arms 5 to 7 as transmission members that engage with these cams 3a, 3b, and 4 to perform rocking motion. The internal combustion engine is also equipped with a pair of exhaust valves (not shown), which are driven to open and close in the same manner as the intake valves 1a and 1b described above.

The first to third rocker arms 5 to 7 are pivotally supported adjacent to each other so as to be swingable on a rocker shaft 8 fixed below the camshaft 2 in parallel to the camshaft 2. The third rocker arms 5 and 7 have basically the same shape, their bases are pivotally supported by the rocker shaft 8, and their respective free ends extend above the intake valves 1a and 1b. At the free end portions of both the rocker arms 5 and 7, each intake valve 1a,
Tappet screws 9a and 9b abutting the upper end of 1b are screwed so as to be movable forward and backward, respectively, and the tappet screws are prevented from loosening by lock nuts 10a and 10b.

The second rocker arm 6 is pivotally supported on the rocker shaft 8 between the first and third rocker arms 5 and 7. This second rocker arm 6 extends slightly from the rocker shaft 8 towards the middle of both intake valves 1a, 1b, and as clearly shown in FIG. A cam slipper 6a is formed which slides in contact with the cam slipper 6a, and the upper end surface of a lifter 12 which slides into a guide hole 11a formed in the cylinder head 11 is in contact with the lower surface of the end of the cam slipper 6a. A coil spring 13 is compressed between the inner surface of the lifter 12 and the bottom surface of the guide hole 11a.
2 is constantly biased upward, which causes the 2nd
A cam slipper 6a of the rocker arm 6 is always in sliding contact with the high-speed cam 4.

As mentioned above, the camshaft 2 is rotatably supported above the engine body, and the low-speed cams 3a and 3 correspond to the first and third rocker arms 5 and 7.
b and a high-speed cam 4 corresponding to the second rocker arm 6 are integrally connected. As clearly shown in FIG. 3, low speed cams 3a and 3b
has a relatively small lifting height and is formed in a cam profile suitable for low-speed engine motion, and its outer peripheral surface is in sliding contact with cam slippers 5a and 7a formed on the upper surfaces of the first and third rocker arms 5 and 7. It's like getting. Furthermore, the high-speed cam 4 is formed with a cam profile suitable for high-speed operation that has a larger lift over a wider angle than the low-speed cams 3a and 3b, and as described above, the second rocker arm 6 Its outer peripheral surface is in sliding contact with the cam slipper 6a. The lifter 12 is omitted from illustration in FIG.

These first to third rocker arms 5 to 7 are integrally swung by a switching device 14, which will be described later, which is installed in a hole drilled through the center of each rocker arm 5 to 7 and parallel to the rocker shaft 8. It is possible to switch between a state in which it can move and a state in which it can be relatively displaced.

On the other hand, retainers 15a and 15b are provided above the intake valves 1a and 1b, respectively, and the valves surrounding the stems of the intake valves 1a and 1b are provided between the retainers 15a and 15b and the engine body. Springs 16a and 16b are interposed to bias both valves 1a and 1b in the closing direction, that is, upward in FIG. 3.

As best shown in Figures 4 and 5, the first
A first guide hole 17 that opens toward the second rocker arm 6 side is bored in the rocker arm 5 in parallel to the rocker shaft 8. A reduced diameter portion 18 is formed on the bottom side of the first guide hole 17, and a stepped portion 19 is formed accordingly.

The second locking arm 6 has a first locking arm 5.
A second guide hole 20 communicating with the first guide hole 17 of
is drilled through both sides.

A third guide hole 21 communicating with the second guide hole 20 is bored in the third rocker arm 7 . The bottom side of the third guide hole 21 is connected to the first guide hole 1
Similar to 7, a step portion 22 and a small diameter portion 23 are formed.

Inside these first to third guide holes 17, 20, 21, there is a first piston 25 that can move between a position where the first and second rocker arms 5, 6 are connected and a position where the connection is released. A second piston 26 that is movable between a position where the second and third rocker arms 6, 7 are connected and a position where the connection is released, a stopper 27 that defines the moving distance of both pistons 25, 26, and both pistons 25, 26. A coil spring 28 that always biases the terminal toward the connected position is attached.

The stopper 27 slides into the first guide hole 17, and when pressed together with both pistons 25 and 26 by the coil spring 28, one end of the stopper 27 comes into contact with the stepped portion 19 of the first guide hole 17. A hydraulic chamber 29 is defined between the bottom surface of the first guide hole 17 and the end surface of the stopper 27. Furthermore, a pair of passages 30 and 31 are bored inside the rock shaft 8, which communicate with a hydraulic pressure supply device to be described later.
The rocking state of the first rocker arm 5 can be controlled via an oil passage 32 bored to communicate with the hydraulic chamber 29 of the first rocker arm 5 and a communication hole 33 bored in the peripheral wall of the rocker shaft 8. Regardless, the hydraulic oil supplied from one hydraulic oil supply passage 30 can always be introduced into the hydraulic chamber 29. The pivot portions of the rocker arms 5 to 7 are lubricated by the lubricating oil supplied from the other lubricating oil supply passage 31.

The first piston 25 has a second axial dimension.
The length is made equal to the entire length of the guide hole 20, and is adapted to be able to slide into the first guide hole 17 and the second guide hole 20.

The axial dimension of the second piston 26 is such that when one end thereof comes into contact with the stepped portion 22 in the third guide hole 21, the other end does not protrude from the side surface of the third rocker arm 7 facing the second rocker arm 6. It is set. and one end of the second piston 26 and the third
The aforementioned coil spring 28 is compressed between the guide hole 21 and the bottom of the small diameter portion 23 .

FIG. 6 schematically shows a hydraulic pressure supply path for the above embodiment. For example, lubricating oil discharged from a lubricating oil pump 40 connected to the crankshaft of an engine is adjusted to a predetermined pressure by a relief valve 41. After that, it is branched in the middle, and one side is supplied to the hydraulic oil supply passage 30 in the rock shaft 8 via the check valve 42 and the solenoid valve 43, and the other side is supplied to the lubricating oil supply passage 3.
1. And a check valve 42 and a solenoid valve 43
An accumulator 44 is provided in the middle between the pump 40 and the pump 40 to store hydraulic pressure, so that a somewhat stable hydraulic pressure can be supplied to the hydraulic oil supply passage 30 regardless of the operating status of the pump 40. .

On the other hand, the operation of the pump 40 and the solenoid valve 43 is controlled by a control signal from a control circuit 45. The engine rotation speed Ne, the crankshaft rotation angle Tw, the accumulator internal pressure P, etc. are input to the control circuit 45, and the operation of the switching device 14 is controlled according to predetermined conditions set inside the control circuit. ing.

Next, the operation of the apparatus described above will be explained.

4 to 6, in the middle and low speed range of the engine, by energizing the solenoid valve 43, the hydraulic oil supply passage 30 and the communication hole 3 of the rocker shaft 8 are
3 and oil passage 32 to the hydraulic chamber 29 of the switching device 14, and each piston 25, 26 resists the biasing force of the coil spring 28 and moves into each guide hole 17, 29 as shown in FIG. 20 so that each rocker arm 5-7 is capable of relative angular displacement with respect to each other.

In such a disconnected state of the switching device 14, the first and third rocker arms 5, 7 swing in response to sliding contact with the low-speed cams 3a, 3b due to the rotational operation of the camshaft 2, Both intake valves 1a and 1b are driven to open and close by delaying their opening timing and advancing their closing timing, and also by reducing their lift amount. At this time, the second rocker arm 6 swings due to sliding contact with the high-speed cam 4, but the sliding movement is caused by both intake valves 1
This has no effect on the operations of a and 1b. That is,
The valve operating characteristic corresponding to the low speed range is selected while the solenoid valve 43 is excited and hydraulic pressure is supplied to the switching device 14.

On the other hand, lubricating oil is constantly pumped into the fluid passage 31, and the rocker shaft 8 and each rocker arm 5 to 7 are lubricated through an oil hole (not shown).During high-speed engine movement, the solenoid valve 43 must be demagnetized. As a result, the hydraulic pressure in the hydraulic chamber 29 of the switching device 14 is discharged. As a result, as shown in FIG. 5, the second piston 26
8 and moves to the second rocker arm 6 side,
The first piston 25 is pushed by the second piston 26 and moves toward the first rocker arm 5 side. As a result,
The first and second pistons 25 and 26 move together until one end of the stopper 27 comes into contact with the stepped portion 19, the first piston 25 connects the first and second rocker arms 5 and 6, and the second piston 26 connects the first and second rocker arms 5 and 6. 2
and third rocker arms 6, 7 are connected.

As described above, the first to third rocker arms 5
- 7 are connected to each other by the switching device 14, the amount of swing of the second rocker arm 6 in sliding contact with the high-speed cam 4 is the largest, so the first and third rocker arms 5, 7 are It swings together with the second rocker arm 6. Therefore, both intake valves 1a, 1
According to the cam profile of the high-speed cam 4, the valve opening timing is advanced and the valve closing timing is delayed, and the lift amount is also increased, and the cam 4 is driven to open and close at the same time. That is, the valve operating characteristic corresponding to the high speed range is selected in a state in which the solenoid valve 43 is demagnetized and no hydraulic pressure is supplied to the switching device 14.

If the intake and exhaust valves operate according to the operating characteristics corresponding to the high speed range at low speeds, the valve opening will become excessive relative to the air-fuel mixture flow rate, resulting in a decrease in charging efficiency in the combustion chamber. Although there is a lack of torque, there is relatively little actual damage to driving.

On the other hand, if the operating characteristics of the intake and exhaust valves remain the same as in the low speed range at high speeds, the air-fuel mixture will not be sufficiently drawn into the combustion chamber, resulting in noticeable rotational problems. Therefore, by controlling the switching device as described above, even if hydraulic pressure no longer acts on the switching device 14 due to a malfunction in the hydraulic system, actual damage to the vehicle during running can be relatively small. Since the valve operating characteristics are switched to those suitable for high-speed ranges, it is possible to continue operating the engine in a relatively stable state.

The pump 40 is used for supplying lubricating oil,
The hydraulic oil supply and the hydraulic oil supply are provided separately, and the accumulator 4
It is also possible to automatically start and stop the operation depending on the pressure accumulation status of accumulator 4.
Depending on the capacity of the accumulator 44, lubricating oil may also be supplied via the accumulator 44. By doing so, it can be expected to reduce power loss due to constant operation of the pump.

In the above embodiment, a case has been described in which the operating characteristics of both valves are switched using a 3-split rocker arm, but the present invention is configured such that a 2-split rocker arm is used to stop one valve at a predetermined rotational speed. It is equally applicable to a variable valve operating characteristic control device.

<Effects of the Invention> As described above, according to the present invention, a stable supply of hydraulic oil is always achieved through the action of the accumulator, and even when a malfunction occurs in the hydraulic system, stable operation of the engine can be continued and Since the switching device operates in the high-speed range side where there is less actual damage, it is possible to achieve a great effect in improving the reliability of the variable valve operating characteristic control device.

[Brief explanation of the drawing]

FIG. 1 is a top view of a valve train having a variable valve operating characteristic control device constructed based on the present invention.
FIG. 2 is a sectional view taken along the - line in FIG. 1. FIG. 3 is a view taken along the arrows in FIG.
Figure 4 shows the difference in Figure 3 during low speed operation.
It is a sectional view along a line. FIG. 5 is a cross-sectional view similar to FIG. 4 showing the state of high-speed operation. FIG. 6 shows an embodiment of the hydraulic circuit. 1a, 1b...Intake valve, 2...Camshaft, 3a,
3b...Low speed cam, 4...High speed cam, 5...
1st Rotsuka arm, 6... 2nd Rotsuka arm, 7
...3rd rocker arm, 5a, 6a, 7a... cam slipper, 8... rocker shaft, 9a, 9b
... Tappet screw, 10a, 10b ... Lock nut, 11 ... Cylinder head, 11a ... Guide hole, 12 ... Lifter, 13 ... Coil spring, 1
4...Switching device, 15a, 15b...Retainer,
16a, 16b... Valve spring, 17...
1st guide hole, 18... Small diameter part, 19... Step part,
20...Second guide hole, 21...Third guide hole,
22...Step part, 23...Small diameter part, 25...First piston, 26...Second piston, 27...Stopper, 28...Coil spring, 29...Hydraulic chamber, 30
...Hydraulic oil supply passage, 31...Lubricating oil supply passage,
32... Oil path, 33... Communication hole, 40... Lubricating oil pump, 41... Relief valve, 42... Check valve,
43... Solenoid valve, 44... Accumulator, 45
...control circuit.

Claims (1)

[Scope of Claims] 1. An intake valve or an exhaust valve that is installed in an intake port or an exhaust port of a combustion chamber, is always biased to close by a spring means, and is driven to open by a cam that rotates in synchronization with a crankshaft. Variable control of valve operating characteristics of an internal combustion engine for selectively switching valve operating characteristics in stages by hydraulic drive between a first state suitable for low-speed operation of the engine and a second state suitable for high-speed engine operation. The device includes a hydraulic pressure generating pump and an accumulator that accumulates hydraulic oil pumped from the pump at a predetermined pressure, and is in the first state when hydraulic pressure is applied to the variable control device. A variable valve operating characteristic control device for an internal combustion engine, wherein each of the second states is selected in a state in which no hydraulic pressure is applied. 2. The variable valve operating characteristic control device for an internal combustion engine according to claim 1, wherein the oil pressure generating pump stops when the internal pressure of the accumulator reaches a predetermined value. 3. The means for intermittent the hydraulic pressure is a solenoid valve,
The variable valve operating characteristic control device for an internal combustion engine according to claim 1 or 2, wherein a side corresponding to a low speed range is selected in an excited state, and a side corresponding to a high speed range is selected in a demagnetized state.