JP3424361B2 - Variable valve train for internal combustion engine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a variable valve operating system for an internal combustion engine, which is capable of switching valve lift characteristics by selectively utilizing cams having different profiles.

[0002]

2. Description of the Related Art Generally, a valve drive system for an internal combustion engine transmits a cam lift to an intake valve and an exhaust valve via a rocker arm and a swing arm, and controls an intake valve and an exhaust valve urged in a closing direction by a valve spring. Although it is configured to be pushed open, preferable valve lift characteristics are different in a low speed range and a high speed range or a low load range and a high load range of the engine, for example, so that the valve lift characteristics can be switched according to operating conditions. Have been proposed.

As an example thereof, Japanese Patent Laid-Open No. 63-10 is used.
In Japanese Patent No. 6309 and Japanese Patent Laid-Open No. 63-167016, two types of cams having different profiles are provided side by side, and the main rocker arm and the sub rocker arm that follow each are switched to a connected state or a detached state as necessary. It is known to have such a configuration.

In this device, a low speed cam and a high speed cam having different profiles are formed side by side on the cam shaft, and the rocker shaft provided in parallel with the cam shaft is driven by the low speed cam. A main rocker arm that rocks and a sub rocker arm that rocks following the high-speed cam are arranged adjacent to each other and are rockable. The intake valve or the exhaust valve is opened and closed by the tip of the main rocker arm.
A connecting mechanism is provided between both rocker arms, which is operated by an oil pressure supplied from the outside to selectively connect or disconnect the sub rocker arm and the main rocker arm. In the device of the above publication, the connecting mechanism is
It is composed of an engagement pin that slides in parallel with the rocker shaft by hydraulic pressure. When the engagement pin projects from the side surface of the main rocker arm and fits into the engagement hole on the side surface of the sub rocker arm, they both swing together. ing. In other words, when both rocker arms are connected in this way, the swing of the sub-rocker arm that follows the high-speed cam is transmitted to the intake / exhaust valve via the main rocker arm, and as a result, the intake / exhaust valve acts as a cam lift for the high-speed cam. Open and close along. Also, when the engagement pin is retracted and both rocker arms are disengaged, the swing of the sub rocker arm is not transmitted to the intake and exhaust valves, and as a result, the intake and exhaust valves are moved by the swing of the main rocker arm that is driven by the low-speed cam. It will be opened and closed.

In this type of variable valve operating device, a connecting mechanism including an engaging pin and the like is switched and controlled by hydraulic pressure. Normally, an engine lubrication hydraulic pressure is used as a hydraulic pressure source to control the hydraulic pressure by an electromagnetic valve. By selectively switching between supply and release, a valve lift characteristic according to operating conditions is obtained. Further, when this type of variable valve operating device is applied to both the intake valve side and the exhaust valve side, it is common to share the hydraulic control mechanism consisting of a solenoid valve and the like and switch at the same time. is there. FIG. 8 shows the torque characteristics when switching between the low speed type cam and the high speed type cam in both the intake valve and the exhaust valve in this way. The characteristics of the low speed type cam and the high speed type cam are shown. By switching the cams in the vicinity of the number of revolutions at which the characteristic intersects, it is possible to obtain a characteristic that the two are continuous.

[0006]

As described above, in the case where the low speed type cam and the high speed type cam are switched by the hydraulic pressure as described above, some cause is caused during traveling while the hydraulic pressure is being supplied to the connecting mechanism. If, for example, the hydraulic pressure drops due to an excessive increase in the oil temperature, sudden switching of the cam occurs regardless of the driver's intention. For example, if both rocker arms are connected to each other when the hydraulic pressure is supplied and the high speed cam is operated, the low speed cam suddenly switches to the low speed cam when the hydraulic pressure drops for some reason. In such a case, conventionally, the timing of switching on the intake valve side and the timing of switching on the exhaust valve side completely match, and therefore,
Very large torque changes occur. For example, T in FIG.
The torque will change rapidly from 1 point to T2,
The drivability is adversely affected.

[0007]

Therefore, according to the present invention, when there is a fluctuation in hydraulic pressure that the driver does not expect, the cam switching on the intake valve side and the cam switching on the exhaust valve side are slightly shifted. The torque is changed stepwise. That is, according to the present invention, a low-speed cam and a high-speed cam having different profiles are formed side by side, a rocker shaft is swingably supported, and the low-speed cam swings following the low-speed cam. A main rocker arm, a sub-rocker arm that is disposed adjacent to the main rocker arm, is swingably supported by the rocker shaft or another axis parallel to the main rocker arm, and that swings following a high-speed cam. An intake valve and an exhaust valve that are driven to open and close by the main rocker arm, and a connecting mechanism that operates by an oil pressure supplied from the outside to selectively connect or disconnect the sub rocker arm and the main rocker arm, and an intake valve side And a hydraulic control mechanism common to both the exhaust valve side coupling mechanism and the exhaust valve side coupling mechanism. Oil pressure value at the time of operation is set to slightly different values in the intake valve side and exhaust valve side. Especially when supplying hydraulic pressure, the auxiliary rocker arm and the main rocker
The arm is in the connected state and is disengaged when the hydraulic pressure is released.
While the connection mechanism is configured so that
The operation of switching to the disengaged state is
The hydraulic pressure value is set so that the
It

According to the second aspect of the present invention, the connecting mechanism includes a connecting lever which is swingably arranged on the main rocker arm and whose upper end is engageable with an engaging step on the lower surface of the sub rocker arm, and the connecting lever. The return spring biases the lever in the disengagement direction, and the hydraulic plunger presses the coupling lever in the engagement direction. The spring force of the return spring is set between the intake valve side and the exhaust valve side. Is characterized by different.

[0009]

According to the third aspect of the present invention, the hydraulic control mechanism is configured to selectively introduce the lubricating hydraulic pressure of the internal combustion engine to the coupling mechanism, and the check valve in the oil jet mechanism for cooling the piston of the internal combustion engine. With the valve opening pressure in between,
The intake valve side oil pressure value is set to a low pressure side and the exhaust valve side oil pressure value is set to a high pressure side.

[0011]

When a predetermined hydraulic pressure is supplied to the connecting mechanism by the hydraulic control mechanism, connection and disconnection of the main and sub rocker arms are switched. In other words , both are in the connected state when the hydraulic pressure is supplied, and are in the disconnected state when the hydraulic pressure is released. When both are connected, the main and sub rocker arms are swung following the high speed cam, and the intake valve and the exhaust valve are opened and closed along the cam lift of the high speed cam. When both are in the disengaged state, the sub-rocker arm is in the free state, so that the intake valve and the exhaust valve are driven by the main rocker arm that follows the low-speed cam, and the valve lift characteristic follows the cam lift of the low-speed cam.
When switching is performed by such a hydraulic control mechanism, the hydraulic pressure applied to the coupling mechanism is relatively large and changes abruptly, so that the switching operation is performed substantially simultaneously on the intake valve side and the exhaust valve side. Be seen.

With the hydraulic pressure being supplied to the connecting mechanism,
When hydraulic pressure is gradually lowered for some reason, when it reaches a predetermined hydraulic pressure value, regardless of the operating conditions, resulting in changeover operation from the connected state to the disengaged state. At this time, the switching is performed at different timings on the intake valve side and the exhaust valve side. That is, the respective switching timings are slightly deviated from each other, and as a result, the torque changes gradually. Specifically, when supplying hydraulic pressure, the high-speed cam
At the time of removal, the low speed cam drives the intake and exhaust valves, respectively. So
Then, the hydraulic pressure gradually decreases for some reason.
Then, the high-speed type cam switches to the low-speed type cam.
In this case, the exhaust valve side is switched first and the intake valve side is switched off later.
Convert. One of the intake and exhaust valves is
The torque reduction when switching to the
Since the exhaust valve is smaller, it causes an unexpectedly large torque drop.
There is no messing.

According to the second aspect of the present invention, by making the spring force of the return spring different, the hydraulic pressure value when switching the intake valve side and the hydraulic pressure value when switching the exhaust valve side are set to different values.

[0014]

According to the third aspect of the invention, the lubricating oil pressure of the internal combustion engine is used as the working oil pressure, and the lubricating oil oil is sprayed onto the piston through the piston cooling oil jet mechanism. This piston cooling oil jet mechanism is equipped with a check valve,
When the oil pressure becomes lower than the valve opening pressure, the check valve is closed and the oil jet supply is stopped. Therefore, if the lubricating oil pressure gradually decreases for some reason, the oil jet supply is stopped after the exhaust valve side is switched to the low-speed cam, and the oil pressure decrease is suppressed. Then, the switching on the intake valve side is executed only when the hydraulic pressure further decreases.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows the structure of a variable valve operating system for an internal combustion engine according to the present invention. In this embodiment, a pair of intake valves 1 and a pair of exhaust valves 2 are provided for each cylinder. A variable valve mechanism is provided on each of the intake side and the exhaust side.

2 to 5 show the variable valve mechanism on the intake side as an example, the exhaust side has basically the same structure. As shown in FIGS. 2 to 5, a pair of main rocker arms 4 are swingably supported at one end by a rocker shaft 3, and a sub rocker arm 5 is provided so as to be sandwiched between the pair of main rocker arms 4. ing. This sub rocker arm 5 is a pair of main rocker arms 4
It is swingably supported by a sub-rocker shaft 6 provided between the two. The main rocker arm 4 has a cam follower roller 7 on its upper surface, and the swing ends 4a press the stem end of the intake valve 1 (or the exhaust valve 2). Incidentally, the pair of main rocker arms 4 are, as shown in FIGS.
They are one with each other. In addition, the sub rocker arm 5
The main rocker arm 4 is formed to be shorter than the main rocker arm 4, and a cam follower portion 8 is provided on the upper surface of the tip portion thereof.

On the camshaft 9 arranged above the rocker shaft 3, a pair of low speed type cams 10 having a small valve lift that come into contact with the cam follower rollers 7 of the main rocker arm 4 and a cam follower portion 8 of the sub rocker arm 5 are slid. The high-speed cam 11 having a large valve lift amount that is in contact with the high-speed cam 11 is formed side by side. As shown in FIG. 4, the sub rocker arm 5 is urged to rotate upward by the lost motion spring 12, and even if the sub rocker arm 5 is disengaged from the main rocker arm 4, the sub rocker arm 5 is not slidably contacted with the high speed cam 11. It is designed to be kept.

A connecting lever 13 is provided below the auxiliary rocker arm 5 as a connecting mechanism for selectively connecting the main and auxiliary rocker arms 4 and 5. The connecting lever 13 is rotatably supported by a pin 14 provided on the main rocker arm 4, and an upper end portion 13 a thereof can be engaged with an engaging step portion 15 on the lower surface of the sub rocker arm 5. The connecting lever 13 is constantly urged in the disengagement direction by the return spring 16 that is pressed against the protrusion 13c (see FIG. 3) via the spring seat 16A, and faces the lower end 13b. A hydraulic plunger 17 is arranged, and when the plunger 17 is projected, it is rotated in the engaging direction. Hydraulic cylinder 1 into which the plunger 17 is slidably fitted
A hydraulic pressure can be supplied to the hydraulic pump 8 through an oil hole 19 in the main rocker arm 4 and a hydraulic pressure supply passage 20 (see FIG. 4) in the rocker shaft 3.

Therefore, in the above structure, when the hydraulic pressure is supplied to the hydraulic cylinder 18 via the hydraulic pressure supply passage 20, the connecting lever 13 rotates in the engaging direction and engages with the engaging stepped portion 15 of the sub rocker arm 5. As a result, when the sub rocker arm 5 is pressed downward by the high speed type cam 11, the main rocker arm 4 is integrally operated, and the intake and exhaust valves 1 and 2 are opened and closed along the profile of the high speed type cam 11. Like When the hydraulic pressure is released, the connecting lever 13 is rotated by the return spring 16 in the engagement releasing direction, and the upper end portion 13 a is separated from the engagement step portion 15. Therefore, the sub rocker arm 5 is separated from the main rocker arm 4, and the intake and exhaust valves 1 and 2 open and close along the profile of the low-speed cam 10 via the main rocker arm 4.

Here, as described above, the connecting lever 13 is
The hydraulic pressure value that is the boundary for switching to the engaged state or the disengaged state is set to different values on the intake valve 1 side and the exhaust valve 2 side. Specifically, compared with the exhaust valve 2 side, the intake valve 1
The switching is performed with a lower hydraulic pressure on the side. The setting of the hydraulic pressure is realized, for example, by making the spring force of the return spring 16 for urging the connecting lever 13 different between the intake valve 1 side and the exhaust valve 2 side. In addition, it is possible to change the operating hydraulic pressure depending on the pressure receiving area of the hydraulic plunger 17, etc. However, when changing the spring force of the return spring 16,
There is an advantage that various working hydraulic pressures can be easily realized only by selecting the return spring 16.

Instead of the connecting lever 13, a known sliding type connecting pin can be used as a connecting mechanism.

The hydraulic control mechanism for controlling the above-mentioned connecting mechanism has a common structure on the intake valve 1 side and the exhaust valve 2 side. That is, as shown in FIG. 1, the engine lubricating oil pressure is simultaneously supplied from the oil pump 22 to the respective oil pressure supply passages 20 in the rocker shaft 3 on the intake side and the exhaust side via the electromagnetic valve 23. . The solenoid valve 23 is
Based on the detection signals of the rotation speed sensor 25 for detecting the rotation speed of the internal combustion engine and the air flow meter 26 for detecting the intake air amount corresponding to the load of the internal combustion engine, the control unit 24 using the microcomputer system outputs O
N-OFF control is performed.

Next, the operation of the above embodiment will be described.

First, when the engine is in the low speed range, the solenoid valve 23 is controlled to the hydraulic pressure release side. As a result, the hydraulic pressure in the hydraulic pressure supply passage 20 becomes a low pressure state, and the connecting lever 13
Becomes the disengagement position, so that the intake / exhaust valves 1, 2 open and close along the profile of the low-speed cam 10 as described above. When the engine is in the high speed range, the solenoid valve 23 is controlled to the hydraulic pressure supply side. As a result, the hydraulic pressure supply passage 20
Since the hydraulic pressure inside is in a high pressure state and the connecting lever 13 is in the engaging position, the intake and exhaust valves 1 and 2 open and close along the profile of the high speed type cam 11 as described above. It should be noted that each cam 1 is determined not by the engine speed alone but by the engine speed and load.
The operating conditions suitable for 0 and 11 may be set.
When the hydraulic pressure is actively controlled by switching the solenoid valve 23 in this way, the hydraulic pressure in the hydraulic pressure supply passage 20 changes relatively large and abruptly, so the return spring 16 on the intake valve side and the exhaust valve side is changed. The difference in spring force has little effect, and the cams 10 and 11 are switched substantially at the same time on both sides.

When the engine is in the high speed range and the connecting lever 13 is controlled to the engagement position, the hydraulic pressure supply passage 2
If the hydraulic pressure in 0 gradually decreases for some reason,
At a predetermined stage of decrease to a hydraulic coupling lever 13 is returned to the disengaged position from the engaging position, thus switched from a high speed type cam 11 to the low speed type cam 10. However,
In the above configuration, since the spring force of the return spring 16 is slightly different between the intake valve side and the exhaust valve side, the respective switching does not occur at the same time, but occurs with some time difference. Specifically, first, switching is performed on the side of the exhaust valve 2 as the hydraulic pressure decreases, and the exhaust valve 2 opens and closes along the profile of the low-speed cam 10. Then, when the hydraulic pressure further decreases, the intake valve 1 side is switched,
The intake valve 1 is driven by the low speed type cam 10. Therefore, FIG.
As shown in FIG. 5, if the engine is operated at the point T1 by the high speed cam 11, the exhaust valve 2 is switched to reduce the torque to the intermediate point T3, and the intake valve 1 is switched to change the torque of the engine T2. It will be reduced to the point. That is, a torque decrease that the driver does not expect occurs in a stepwise manner, and the shock can be remarkably reduced as compared with the case where the torque rapidly decreases from the T1 point to the T2 point. In particular, since the exhaust valve 2 side is switched first, the initial torque decrease is smaller than when the intake valve 1 is switched first, and the driver's discomfort is reduced.

Next, an embodiment in which the internal combustion engine is equipped with an oil jet mechanism for cooling the piston will be described. In an engine with a high heat load on the piston, such as an internal combustion engine with a supercharger, an oil jet mechanism that blows lubricating oil onto the lower surface of the piston to cool it may be provided.
FIG. 6 shows the oil jet mechanism 32 arranged below the cylinder bore of the cylinder block 31. The oil gallery 33 of the cylinder block 31 to the check valve 3 is shown.
The lubricating oil introduced through the nozzle 4 is jetted from the nozzle 35 toward the piston (not shown). The valve opening pressure of the check valve 34 is set by the coil spring 36, and when the valve opening pressure is equal to or lower than the valve opening pressure, the ejection of the lubricating oil is stopped. The oil gallery 33 is
It is always in communication with the discharge side of the oil pump 22 described above.

As shown in FIG. 7, the valve opening pressure P1 of the check valve 34 is sandwiched, and the switching operation oil pressure value P2 on the intake valve 1 side is set on the lower pressure side than this, and the valve opening pressure P1 is set. The switching operation hydraulic pressure value P3 on the exhaust valve 2 side is higher than P1.
Is set.

Therefore, if the hydraulic pressure gradually decreases for some reason during operation of the high speed cam 11, the exhaust valve 2 first switches to the low speed cam 10, and then the check valve 3
4 is closed and the lubricating oil jetting of the oil jet mechanism 32 is stopped. The stop of the oil jet suppresses the decrease of the lubricating oil pressure. In spite of this, the intake valve 1 is switched to the low-speed cam 10 only when the hydraulic pressure further decreases. In other words, the switching on the intake valve 1 side, which greatly affects the drivability, is avoided as much as possible. Even when the intake valve 1 is switched to the low-speed cam 10, the exhaust valve 2 is already the low-speed cam 10. Therefore, as described above, a large torque fluctuation does not occur and drivability is improved. Minimal impact.

[0031]

As is apparent from the above description, according to the variable valve operating system for an internal combustion engine according to the present invention, when the hydraulic pressure is reduced due to, for example, an increase in the oil temperature, the cam which the driver does not expect Even if the switching occurs, the switching is executed at slightly different timings on the intake valve side and the exhaust valve side, so that it is possible to prevent the sudden torque fluctuation from occurring and suppress the influence on the drivability. In particular, intake valves that have a great impact on drivability
Since the side will switch later, the driver feels uncomfortable.
Layer becomes smaller.

Further, according to the second aspect of the invention, since the switching operation hydraulic pressure values on the intake valve side and the exhaust valve side are set to different values only by changing the spring force of the return spring, it can be realized very easily.

[0033]

Further, according to the third aspect of the invention, when the oil pressure is lowered, the lubricating oil jet of the piston cooling oil jet mechanism is stopped before the intake valve side is switched, so that the oil pressure reduction is suppressed. Therefore, the cam switching on the intake valve side, which greatly affects the drivability, can be avoided as much as possible.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing a structure of a variable valve operating device according to the present invention.

FIG. 2 is a plan view showing a main part of a variable valve mechanism on the intake side.

FIG. 3 is a cross-sectional view showing a rocker arm by cutting out a part thereof.

FIG. 4 is a sectional view taken along the line AA of FIG.

5 is a sectional view taken along the line AA of FIG. 3 showing only the main rocker arm.

FIG. 6 is a sectional view showing the configuration of an oil jet mechanism.

FIG. 7 is a characteristic diagram showing the relationship between the valve opening pressure of the check valve and the switching hydraulic pressure of the variable valve operating device.

FIG. 8 is a characteristic diagram showing torque characteristics of an internal combustion engine by a low speed cam and a high speed cam.

[Explanation of symbols]

1 ... Intake valve 2 ... Exhaust valve 4 ... Main rocker arm 5 ... Deputy rocker arm 10 ... Low speed type cam 11 ... High-speed cam 13 ... Connection lever 16 ... Return spring 17 ... Hydraulic Plunger 23 ... Solenoid valve

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-7-238817 (JP, A) JP-A-3-43610 (JP, A) JP-A-2-275008 (JP, A) JP-A-4- 17705 (JP, A) JP-A 4-1406 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F01L 13/00 301

Claims (3)

(57) [Claims] 1. A cam shaft formed by arranging a low speed type cam and a high speed type cam having different profiles side by side, and a rocker shaft swingably supported by the main shaft which swings following the low speed type cam. The rocker arm and the main rocker arm are arranged adjacent to the rocker arm, and are rockably supported by the rocker shaft or another axis parallel to the rocker shaft,
And a sub-rocker arm that swings following the high-speed cam,
An intake valve and an exhaust valve that are driven to open and close by the main rocker arm, and a connecting mechanism that operates by an oil pressure supplied from the outside to selectively connect or disconnect the sub rocker arm and the main rocker arm, and an intake valve side and a common hydraulic control mechanism for both the coupling mechanism of the exhaust valve side, Ri Na comprises a hydraulic value when the coupling mechanism is switching operation is slightly different values at the intake valve side and exhaust valve side In the set variable valve device of the internal combustion engine , the sub-rocker arm and the main rocker arm are connected when hydraulic pressure is supplied.
State so that when the hydraulic pressure is released,
The connection mechanism is configured and the disconnection
The replacement operation uses a lower oil pressure at the intake valve than at the exhaust valve side.
A variable valve operating system for an internal combustion engine , wherein a hydraulic pressure value is set so as to be performed . 2. The connecting mechanism, wherein the connecting mechanism is swingably arranged on the main rocker arm, and an upper end portion thereof is engageable with an engaging step portion on a lower surface of the sub rocker arm; and a connecting lever releasing direction of the connecting lever. And a hydraulic plunger that presses the connecting lever in the engaging direction, and the spring force of the return spring is
2. The variable valve operating system for an internal combustion engine according to claim 1, wherein the intake valve side and the exhaust valve side are different. 3. The hydraulic control mechanism is configured to selectively introduce the lubricating hydraulic pressure of the internal combustion engine to the connecting mechanism, and to sandwich the check valve opening pressure in the piston cooling oil jet mechanism of the internal combustion engine. The hydraulic pressure value on the intake valve side is set on the low pressure side, and the hydraulic pressure value on the exhaust valve side is set on the high pressure side.
1. A variable valve operating device for an internal combustion engine according to 1 .