JP2703978B2 - Valve train of internal combustion engine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve train for an internal combustion engine, and more particularly to a valve train for changing the operating state of an intake valve or an exhaust valve in a stepwise manner according to the rotational speed of the engine. The present invention relates to a valve operating mechanism for an internal combustion engine including a valve operating state changing unit.

<Conventional technology> Conventionally, a plurality of intake valves or exhaust valves are provided for each cylinder in order to optimize the intake and exhaust efficiency over a wide operating range, and the number of operating valves is switched according to the engine speed. There have been proposed various valve operating mechanisms of an internal combustion engine in which the operation timing of a sliding valve is changed. For example, Japanese Patent Application Laid-Open No. 61-19911 by the applicant of the present application discloses that a low-speed cam and a high-speed cam each having a shape corresponding to a low-speed operation and a high-speed operation of an engine are provided on a cam shaft that rotates in synchronization with the rotation of the engine. The first and second rocker arms slidably contacting the low-speed cam and the third rocker arm slidably contacting the high-speed cam are adjacently supported on the rocker shaft so as to be relatively angularly displaceable, and each rocker arm is relatively angularly displaced. A valve operating state switching device for an internal combustion engine provided with a connecting means capable of switching between a state and an integrally connected state is disclosed.

This connecting means has a piston which slides into a guide hole provided in each rocker arm, and operates the piston by hydraulic pressure in a state where the base circle of the cam slides on the cam slipper surface of each rocker arm and each guide hole is aligned. By doing so, each rocker arm is connected or disconnected. The operating oil pressure of the piston is selectively switched and supplied by a switching valve according to the rotation speed of the engine. However, if the switching valve is not used for a long period of time, there is a possibility that a stuck state may occur and the switching valve may not operate normally when it is desired to actually operate the switching valve. Further, when abnormal wear occurs on the cam slipper surface of the rocker arm or the like, the swing angle of the rocker arm may change, and the guide holes may be eccentric to hinder normal operation of the piston. On the other hand, the applicant of the present application has
No. 7909 proposes a valve operating state switching device for an internal combustion engine provided with means for detecting a malfunction of a piston.

<Problems to be Solved by the Invention> An object of the present invention is to provide a valve operating state switching device with a normal operation in order to be able to take a prompt action in the event of an abnormal situation. It is an object of the present invention to provide a valve operating mechanism of an internal combustion engine capable of confirming an operation state of the device.

<Means for Solving the Problems> According to the present invention, such an object is achieved according to an intake valve or an exhaust valve driven to be opened and closed by a cam that rotates synchronously with a crankshaft and a first operating state of the engine. A valve operating state changing means for selectively changing the valve operating state by the action of a fluid pressure, wherein the valve operating state changing means selectively changes the valve operating state by an action of a fluid pressure. The present invention is attained by providing a valve operating mechanism for an internal combustion engine, characterized by having a check means for operating the valve operating state changing means to check the operating state.

<Operation> With this configuration, the normal operation is previously performed by operating the valve operation state changing unit by the confirmation unit separately from the normal operation of switching the valve operation state in accordance with the first operation state. It is possible to confirm and detect an abnormal operation.

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

As shown in FIG. 1, a pair of intake valves 1a and 1b provided in the internal combustion engine main body is a half of a crankshaft (not shown).
A pair of low-speed cams 3a, 3b and a single high-speed cam 4 integrally provided on the camshaft 2 synchronously driven at the speed described above, and swings by engaging with these cams 3a, 3b, 4. Opening and closing operations are performed by the first to third rocker arms 5 to 7 as cam followers. The internal combustion engine is provided with a pair of exhaust valves (not shown), and is driven to open and close similarly to the above-described intake valves 1a and 1b.

The first to third rocker arms 5 to 7 are swingably supported adjacent to each other on a rocker shaft 8 fixed and provided in parallel below the camshaft 2. The first and third rocker arms 5, 7 have basically the same shape, the base of which is pivotally supported by the rocker shaft 8 and the free end extends above both intake valves 1a, 1b. At the free ends of both rocker arms 5, 7,
Tappet screws 9a and 9b abutting on the upper ends of the intake valves 1a and 1b are screwed so as to be prevented from loosening by lock nuts 10a and 10b, respectively, and to be able to advance and retreat. Cam slippers 5a and 7a are formed on the upper surfaces of the first and third rocker arms 5 and 7, respectively, to be in sliding contact with the low speed cams 3a and 3b.

The base of the second rocker arm 6 is supported by a rocker shaft 8 between the first and third rocker arms 5 and 7. The free end of the second rocker arm 6 is a rocker shaft 8.
From the intake valves 1a and 1b, and a cam slipper that slides on the high-speed cam 4 on its upper surface.
6a is formed, and the upper surface of a lifter (not shown) fixed to the cylinder head side is in contact with the lower surface. The lifter urges the second rocker arm 6 upward by a built-in coil spring as a lost motion spring so that the cam slipper 6a always slides on the high-speed cam 4.

The camshaft 2 is rotatably supported above the engine body,
Low-speed cams 3 corresponding to the first and third rocker arms 5 and 7
a, 3b and a high-speed cam 4 corresponding to the second rocker arm 6 are integrally connected. As best shown in FIG. 2, the low speed cams 3a and 3b have a relatively small head and are formed into a cam profile having an oval cross section adapted to a low speed operation of the engine. The high-speed cam 4 has a larger head over a wider angle than the low-speed cams 3a, 3b, and is formed in a cam profile having an oval cross section suitable for high-speed operation.

The first to third rocker arms 5 to 7 can be switched between a state in which they can be swung integrally and a state in which they can be relatively displaced by a connecting device 11 built in the central portion thereof. In addition, retainers 12a and 12b are provided above the intake valves 1a and 1b, respectively, and valve springs are interposed between the intake valves 1a and 1b so as to surround the stems of the intake valves 1a and 1b. 16a, 1
6b urges both valves 1a, 1b in the valve closing direction, that is, upward in FIG.

3 and 4, the first rocker arm 5 is provided with a first guide hole 14 opened toward the second rocker arm 6 in parallel with the rocker shaft 8. At the bottom side of the first guide hole 14, a step with the small diameter portion 15
16 are formed. The second rocker arm 6 has a second guide hole communicating with the first guide hole 14 of the first rocker arm 5.
17 are penetrated. The third rocker arm 7 is provided with a third guide hole 18 communicating with the second guide hole 17.
A step portion 19 is formed in the third guide hole 18, and a small-diameter through hole 20 is formed in the bottom wall concentrically with the third guide hole 18.

Inside the first to third guide holes 14, 17, 18, a first piston 21 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 22 movable between a position where the second and third rocker arms 6 and 7 are connected and a position where the connection is released.
And a stopper 23 that regulates the movement of the pistons 21 and 22 are in sliding contact with each other. A coil spring 24 that urges the pistons 21 and 22 toward the uncoupling position is mounted on the stopper 23.

The first piston 21 has an axial dimension such that one end thereof abuts the step 19 in the first guide hole 14 and the other end does not protrude from the first guide hole 14. The second piston 22
It has an axial dimension equal to the entire length of the guide hole 17. The stopper 23 includes a guide rod 23a that passes through the through hole 24.
A plurality of axial grooves 23b are provided on the outer peripheral surface of the tip portion of the guide rod 23a.
When the stopper 23 is located at the connection release position side, the third
The guide hole 18 communicates with the outside.

The bottom of the first guide hole 14 and the first piston 21
A hydraulic chamber 25 is defined between the end face and the hydraulic chamber 25. A pair of passages 26 and 27 communicating with a hydraulic supply device (not shown) are formed in the rocker shaft 8, and an oil passage 28 provided in the first rocker arm 5 and a peripheral wall of the rocker shaft 8 are formed. The hydraulic oil supplied from one hydraulic oil supply passage 26 can be always introduced into the hydraulic chamber 25 through the communication hole 29 regardless of the swing state of the first rocker arm 5. Have been.

An oil passage 30 is provided in the third rocker arm 7, and a communication hole 31 is formed in a corresponding position on the peripheral wall of the rocker shaft 8, regardless of the swing state of the third rocker arm 7. , The fluid passage 27 through the oil passage 30 and the communication hole 31
And the third guide hole 18 can communicate with each other.
The oil passage 30 is opened at a position where the second piston 22 communicates with the third guide hole 18 when the second piston 22 is located at the uncoupling position (fourth position).
Figure).

FIG. 5 schematically shows a hydraulic pressure supply path for the above embodiment. One hydraulic oil supply passage 26 is connected via an electromagnetic valve 32 to, for example, a lubricating oil pump 33 that is connected to a crankshaft of the engine and supplies lubricating oil at a predetermined pressure. The solenoid valve 32 is electrically connected to the control device 34 and opens and closes according to an instruction from the control device. The other fluid passage
27 is connected to a lubricating oil pump 33 via an orifice 35. And, in the two passages 26, 27 and the discharge passage of the pump 33,
Oil pressure sensors 36 to 38 are provided, respectively, so that the oil pressure can be constantly monitored.

Next, the operation of the above-described embodiment will be described with reference to FIGS.

In the middle and low speed range of the engine, the solenoid valve 32 is closed, and no hydraulic pressure is supplied to the hydraulic chamber 25 of the coupling device 11, so that each piston 21,
Reference numeral 22 is aligned with the guide holes 14 and 17 by the urging force of the coil spring 24 as shown in FIG. Therefore, the rocker arms 5 to 7 can be displaced relative to each other. That is, when the camshaft 2 rotates, the first and third rocker arms 5 and 7 are slidably contacted with the low speed cams 3a and 3b to swing and open and close the two intake valves 1a and 1b. At this time, the second rocker arm 6 slidably contacts the high-speed cam 4 and swings, but its operation does not affect the operation of both the intake valves 1a and 1b.

On the other hand, lubricating oil is constantly pumped into the fluid passage 27,
The rocker shaft 8 and each of the rocker arms 5 to 7 are lubricated through oil holes (not shown), and the rocker shaft 8
Communication hole 31, oil passage 30 of third rocker arm 7, and guide rod 23
Lubricating oil is discharged into the engine through the axial groove 23b of a. In this state, the command pressure P2 of the hydraulic pressure sensor 37 provided in the hydraulic oil supply passage 26 is 0, and the original pressure P3 indicates the highest pressure.

During high-speed operation of the engine, the solenoid valve is
By opening the valve 32, the connecting device is connected from the hydraulic oil supply passage 26 through the communication hole 29 of the rocker shaft 8 and the oil passage 28.
Operating hydraulic pressure is supplied to the 11 hydraulic chambers 25. As a result, as shown in FIG.
Moves toward the second rocker arm 6 against the urging force of
The piston 22 is pushed by the first piston 21 and moves to the third rocker arm 7 side. As a result, the first and second pistons 21 and 22 move together until the stopper 23 contacts the step portion 19,
First and second rocker arms 5, 6 are provided by first piston 21.
Are connected, and the second and third rocker arms 6, 7 are connected by the second piston 22.

In the state where the first to third rocker arms 5 to 7 are connected to each other by the connecting device 11 as described above, the swing amount of the second rocker arm 6 that slides on the high-speed cam 4 is the largest. And the third rocker arms 5 and 7 swing together with the second rocker arm 6. Therefore, both intake valves 1a, 1b
Are driven to open and close according to the cam profile of the high-speed cam 4.

On the other hand, since the oil passage 30 of the third rocker arm 7 is closed by the movement of the second piston 22, the lubricating oil supplied to the fluid passage 27 is supplied between the rocker arms 5 to 7 and the rocker shaft 8 and between the pistons 21. , 22 and each of the guide holes 14, 20, 21 only flows. Therefore, the indicated pressures of the oil pressure sensors 36 to 38 of the two passages 26 and 27 become substantially equal, or the pressure P1 of the fluid passage 27 becomes the lowest (P1 ≦ P2 = P3).

At this time, if there is a malfunction in both pistons 21 and 22, the oil passage
Since the lubricating oil 30 flowing in the fluid passage 27 side is discharged from the axial groove 23b because the 30 is kept open, the pressure P1 in the fluid passage 27 does not fluctuate significantly. The malfunction can be known. Conversely, the operation on the return side of the pistons 21 and 22 can be recognized as a malfunction by monitoring the change in the pressure P1 on the fluid passage 27 side.

In this way, a change in the pressure P1 in the fluid passage 27, or a change in the pressure P1 in the fluid passage 27 and the pressure P2 in the hydraulic oil supply passage 26, or a change in the differential pressure between the pressure P1 in the fluid passage 27 and the original pressure P3, The operation status of 21, 22 can be grasped. And the solenoid valve
Piston malfunction due to malfunction of 32 is due to hydraulic oil supply passage
It can be known by monitoring the pressure P2 of 26.

According to the present invention, in addition to the case where the valve operating state is switched at the predetermined rotation speed set between the low-speed rotation range and the high-speed rotation range of the engine as described above, the predetermined operating conditions set in advance Below, the control device 34 operates the solenoid valve 32 for a fixed short time, and switches to the high-speed operation state during the low-speed operation of the engine and to the low-speed operation state during the high-speed operation. The normal operation of the piston can be confirmed in advance by detecting changes in the oil pressures P1, P2, and P3 from the respective oil pressure sensors 36 to 38.

Such predetermined operating conditions include, for example, when operating the coupling device 11 to switch the valve operating state without deteriorating the operation of the engine, such as during deceleration that does not require output, during idle operation, during gear shifting of the transmission, or It is preferable to be in a neutral state, at the time of braking operation, within a certain delay time immediately after the ignition is turned off, and the like. In addition to these conditions, the operation of the piston can be confirmed by operating the coupling device 11 only once every fixed traveling distance or operation time. Therefore, various information A is input to the control device 34 from a neutral switch, a gear switch, a clutch switch, a brake switch, an ignition switch, an odometer, and the like provided in the transmission. In addition, if the driver
To operate the coupling device 11 only once in a short time to confirm the operation status.

When an abnormality is detected by such a checking operation, the control device 34 controls the engine output by shifting the ignition timing (θig), cutting off the fuel supply, or forcibly returning the throttle (θth). Thus, the engine can be maintained at the allowable rotation speed to prevent damage. At the same time, the control device 34 turns on the warning light 40 to notify the driver of the occurrence of the abnormality. Further, after detecting the abnormality, the operation of the switching valve 32 is limited so as to maintain the valve operating mechanism of each cylinder in the low-speed operation state, and the low-speed running of the engine can be ensured.

The hydraulic circuit for monitoring the operation status of the piston is not limited to the above-described one, but branches the two passages 26 and 27 downstream of the solenoid valve 32 to know the operation of the piston based on the differential pressure between the pressures P1 and P2 in both passages. be able to. Furthermore, air pressure may be applied to the fluid passage side, and the pressure before and after the orifice provided in the fluid passage may be monitored, and the operation of the piston may be controlled by a change in the flow rate of fluid such as lubricating oil and air flowing through the fluid passage. It is also possible to detect. Further, since the pressure and the flow rate change proportionally, the number of inactive pistons can be known from the change ratio.

Further, as means for detecting malfunction of the piston,
It is conceivable to use an electrical means for directly grasping the operation of the piston using an electromagnetic proximity sensor or the like, or indirectly grasping the operation timing of a rocker arm or the like driven by a cam. In this case, it can be used for a limit switch or the like having a mechanical contact in place of the non-contact type proximity sensor.

In addition, as a drive means of the switching piston, not only the above-mentioned hydraulic drive but also an electric or mechanical device can be used. The rocker arm support structure may be not only the end pivot but also a center pivot, and the transmission member may be a direct bucket lifter. Further, the opening position of the fluid passage is not limited to the above embodiment, but may be a position opened at the time of connection. In the above embodiment, the operation timing of both the two valves is switched by the three-piece rocker arm.
Valve trains with various types of valve operating state change devices, including a valve train configured to drive a two-piece rocker arm with a single cam and at one of the valves to stop at a predetermined rotational speed The same can be applied to

<Effects of the Invention> As described above, according to the present invention, the operation of the piston is monitored by operating the coupling device for a short period of time under the predetermined operating conditions. To ensure normal operation, and to have a self-diagnosis function for detecting an abnormal operation of changing the valve operation state in advance, thereby improving the usability of the valve operation state switching device of the internal combustion engine. Is big.

[Brief description of the drawings]

FIG. 1 is a top view of a valve mechanism having a valve operating state switching device configured according to the present invention. FIG. 2 is a view taken in the direction of the arrow II in FIG. FIG. 3 is a cross-sectional view taken along the line IV-IV in FIG. 2 during low-speed operation. FIG. 4 is a sectional view similar to FIG. 3, showing a high-speed operation. FIG. 5 shows an embodiment of the hydraulic circuit. 1a, 1b: intake valve, 2: cam shaft 3a, 3b: low speed cam 4: high speed cam, 5: first rocker arm 6: second rocker arm, 7: third rocker arm 5a, 6a, 7a: cam slipper 8: Rocker shaft 9a, 9b: Tappet screw 10a, 10b: Lock nut 11: Connecting device, 12a, 12b: Retainer 13a, 13b: Valve spring 14: First guide hole, 15: Small diameter portion 16: Step portion, 17: Second Guide hole 18 ... Third guide hole, 19 ... Stepped portion 20 ... Through hole, 21 ... First piston 22 ... Second piston, 23 ... Stopper 23a ... Guide rod, 23b ... Axial groove 24 ... Coil spring, 25 ... Hydraulic pressure Chamber 26 ... Hydraulic oil supply passage, 27 ... Fluid passage 28 ... Oil passage, 29 ... Communication hole 30 ... Oil passage, 31 ... Communication hole 32 ... Solenoid valve, 33 ... Lubricant oil pump 34 ... Control device, 35 ... Orifice 36 ~ 38… Hydraulic sensor 39… Manual switch, 40… Warning light

Claims (5)

(57) [Claims] An intake valve or an exhaust valve driven to be opened and closed by a cam rotating in synchronization with a crankshaft, and a valve operation for selectively changing a valve operation state by the action of a fluid pressure according to a first operation state of the engine. A valve operating mechanism for an internal combustion engine, comprising: a state changing unit; and a checking unit configured to operate the valve operating state changing unit for a predetermined time in a second operating state different from the first operating state and to confirm the operating state. A valve train for an internal combustion engine, comprising: 2. A valve operating mechanism for an internal combustion engine according to claim 1, wherein said checking means further comprises monitoring means capable of detecting an operating state of said valve operating state changing means. 3. A valve mechanism for an internal combustion engine according to claim 2, wherein said monitoring means has a warning means for notifying an abnormality recognized in the operation of said valve operating state changing means. . 4. The system according to claim 1, wherein the confirmation means switches to a high-speed operation state during low-speed operation of the engine and returns to a low-speed operation state after a lapse of a predetermined time. 3. The valve operating mechanism for an internal combustion engine according to claim 1, wherein the valve operating state changing means is operated so as to return to an operating state. 5. The valve operating mechanism for an internal combustion engine according to claim 1, wherein said confirmation means can be manually operated.