JP2542619B2 - Engine valve gear - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an engine valve operating system, and more particularly to an engine valve operating system in which a cam for opening and closing a valve is properly used according to the engine speed. Regarding

<< Prior Art >> Conventionally, as a valve operating device of this kind, for example, the actual open sho 61-58.
Some are disclosed in Japanese Patent No. 605. This valve gear is an engine having two intake valves for each cylinder, and has a low speed cam having a low speed cam profile on a cam shaft and a high speed cam profile including the low speed cam. The low-speed cam forms a high-speed cam, and the low-speed cam slides on a low-speed rocker arm that transmits the movement of the low-speed cam to both intake valves. A high-speed rocker arm for transmitting the movement thereof to the low-speed rocker arm is provided, and the low-speed rocker arm and the high-speed rocker arm are engaged or disengaged in accordance with the engine speed to interlock or An operation switching means for switching the opening / closing operation characteristics of the valve in the non-interlocked state is provided.

This operation switching means is of a hydraulic type, and is provided in a hydraulic chamber formed in the high-speed rocker arm, and is slidably provided in this hydraulic chamber so that when the pressure in the hydraulic chamber becomes high, it is directed to the lateral low-speed rocker arm. With a protruding plunger,
Plunger fitting holes formed in the low-speed rocker arm according to the position of the plunger when both the high-speed rocker arm and the low-speed rocker arm are in contact with the base circle of each cam, and this fitting A receiver provided in the hole and used to push the plunger back toward the hydraulic chamber with a return spring when the pressure in the hydraulic chamber is low.

The high-speed rocker arm and the rocker shaft are provided with an oil supply passage that connects the hydraulic chamber and the oil passage in the rocker shaft and supplies lubricating oil flowing in the oil passage into the hydraulic chamber as working oil. The oil supply passage is always communicated with the oil passage in the rocker shaft via an annular groove formed on the inner peripheral surface of the boss portion.

Further, the pressure of the lubricating oil supplied into the oil passage of the rocker shaft is adjusted by the pressure adjusting means in accordance with the number of revolutions of the engine. At low pressure, the operation switching means is switched to the non-interlocking state and the intake valve is driven by the low speed cam, while in the high engine speed range, the lubricating oil supply oil pressure is increased to switch the operation switching means to the interlocking side. The intake valve is driven by a high-speed cam, so that the intake valve is opened and closed at the opening and closing timing according to the engine speed.

<Problems to be Solved by the Invention> By the way, in the above-mentioned conventional valve operating device, since the hydraulic chamber of the operation switching means is always communicated with the oil passage in the rocker shaft, the oil pressure in the oil passage is always in the hydraulic state. It is working indoors. Therefore, when the engine speed shifts from the low-speed rotation range to the high-speed rotation range, or when the high-speed rotation range changes to the low-speed rotation range, the oil pressure in the oil passage changes from low pressure to high pressure by the hydraulic pressure adjusting means, or Adjusted from high pressure to low pressure,
The switching means is switched to the interlocking state or the non-interlocking state regardless of the rotational position of the cam shaft.

At this time, if the rising of the switching operation is started when the intake valve in which the high-speed rocker arm and the low-speed rocker arm are in contact with the cam base circle of each cam is not lifted, the plan of the high-speed rocker arm is planned. Since the position of the jar and the position of the fitting hole of the low speed rocker arm match, and because the diameter of the base circle is the same, they do not cause a trouble by smoothly shifting to the interlocking state or the non-interlocking state. If the rising of the switching operation is started during the lift of the intake valve in which the high-speed rocker arm and the low-speed rocker arm are in contact with the portion other than the cam base circle, there is a problem that a problem occurs.

That is, since the valve lift curve of the low speed cam is included in the valve lift curve of the high speed cam, when the low speed rocker arm and the high speed rocker arm are not linked, they move relative to each other during the valve lift. . Therefore, when switching from the non-interlocking state to the interlocking state, if the switching operation starts immediately after the high-speed rocker arm starts to lift, the plunger does not fully fit in the fitting hole and the high-speed rocker arm does not fit. The engagement between the arm and the low speed rocker arm may be incomplete, which may cause a switching operation failure. Then, the plunger is pushed back in the middle of the lift, the low-speed rocker arm is separated from the high-speed rocker arm, and falls on the low-speed cam to generate a tapping sound.

Also, when shifting from the linked state to the non-linked state,
If the switching operation rises during the lift, the low-speed rocker arm is disengaged from the high-speed rocker arm, and at the same time, the low-speed rocker arm falls onto the low-speed cam to generate a tapping sound.

The present invention has been made in view of the above circumstances, and an object thereof is to properly switch the cam for opening and closing the valve in accordance with the engine speed, and accordingly, the switching operation failure and the accompanying malfunction thereof. An object of the present invention is to provide a valve operating device for an engine that can prevent the generation of hammering noise as much as possible.

<< Means for Solving Problems >> In order to solve the above problems, the present invention forms a high speed cam and a low speed cam having different lift amounts on a cam shaft, and the low speed cam has a valve. A low-speed rocker arm swingably supported on a rocker shaft by being hung between and is provided adjacent to the low-speed rocker arm on the side, and one end of the high-speed cam of the cam shaft is provided. A high-speed rocker arm pivotally supported on the rocker shaft by abutting the rocker shaft is provided, and the high-speed rocker arm and the low-speed rocker arm on the side of the high-speed rocker arm are engaged with each other according to the engine speed. In a valve operating system for an engine provided with an operation switching means for disconnecting and switching the opening / closing operation characteristic of the valve, the cam lift curves of the low speed cam and the high speed cam are calculated as follows. The valve opening timing is earlier, and the initial portions of both lift curves after valve opening are set to be close to each other.

<Operation> According to the present invention having the above-described configuration, in the high rotation range of the engine, the operation switching means engages the low speed rocker arm and the high speed rocker arm to drive the valve to open and close by the high speed cam, and to rotate at a low speed. In the region, the operation switching means disengages the low-speed rocker arm from the high-speed rocker arm to drive the valve to open and close by the low-speed cam. At this time, since the cam lift curves of the low speed cam and the high speed cam are close to each other in the initial portion after the valve is opened, when the low speed rocker arm and the high speed rocker arm are disengaged from each other in the initial portion. However, relative movement to them hardly occurs. For this reason,
Even if the switching operation of the operation switching means rises due to the initial portion thereof, the switching operation is smoothly and reliably performed and no malfunction occurs, and the low speed rocker arm and the high speed rocker arm are engaged. The low-speed rocker arm does not drop onto the low-speed cam even when the is released.

Also, the valve opening timing of the high speed cam is set earlier than the valve opening timing of the low speed cam so that the overlap period of the intake / exhaust valve at the time of high engine rotation is longer than that at the time of low engine rotation. It is possible to improve the charging efficiency of intake air at high rotation speed.

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

1 to 4 show an embodiment in which the engine valve operating system of the present invention is applied to the intake valve side of a three-valve system engine, and FIG. 1 is a side sectional view showing the overall structure thereof. FIG. 2 is a side sectional view of the main part, and FIG. 3 is a plan view of the intake valve side.

In the figure, 1 is an intake valve, and two intake valves 1 are provided for each cylinder. Reference numeral 2 is an exhaust valve, and one exhaust valve 2 is provided for each cylinder. Numeral 3 is a cam shaft. The cam shaft 3 has three intake valve driving cams 4a, 4b, 5 and 1 per cylinder.
Two exhaust valve driving cams 6 are provided.

Two of the three intake valve driving cams 4a, 4b, 5 are low speed cams 4a, 4b having a low speed cam profile.
The other one is the high-speed cam 5 having a high-speed cam profile with a larger lift than the low-speed cam. The low-speed cams 4a and 4b are arranged at both ends of each cylinder. A cam 5 for high speed and a cam 6 for driving the exhaust valve are arranged between the two.

Rocker shafts 7 and 8 are provided above the cam shaft 3 along both sides thereof, and the rocker shaft 7 on the exhaust valve 2 side is provided with an exhaust valve driving cam 6 of the cam shaft 3 and an exhaust valve 2. A rocker arm 24 for driving the exhaust valve is provided swingably between the rocker arm 2 and the valve stem 2a. Further, on the rocker shaft 8 on the intake valve 1 side, three rocker arms 9, 10, 11 for driving the intake valve are swingably arranged on the rocker shaft 8.

The two rocker arms provided on both sides are low-speed rocker arms 9 and 10, and the arm portions 9a and 10a at one of the rocking ends of the rocker arms 9 and 10a via the roller 12 of the low-speed cam 4a of the cam shaft 3.
・ While making rolling contact with 4b, the arm portions 9b, 10b at the other swinging end are in contact with the valve stem 1a, 1a of the intake valve 1.1 through the hydraulic lash adjuster 13,
The cams 4a and 4b for low speed and the intake valves 1.1 are provided so as to be extended substantially linearly. The low speed rocker arms 9 and 10 are formed symmetrically.

On the other hand, the rocker arm that is in contact with the side surfaces of these two low-speed rocker arms 9 and 10 and is provided between them is a high-speed rocker arm 11, and this high-speed rocker arm 11 is located on the side of one of the camshafts 3 thereof. The arm portion 11a at the swinging end is in sliding contact with the high speed cam 5 of the cam shaft 3 by the slipper 14.

As shown in FIG. 3, the high-speed rocker arm 11 and the low-speed rocker arm 9/10 are provided with a low-speed rocker arm 9/10 and a high-speed rocker arm 11 depending on the engine speed. Intake valve 1.1
A hydraulic operation switching means 15 for switching the opening / closing operation characteristic of is provided.

The operation switching means 15 includes a hydraulic chamber 16 integrally formed in the arm portion 11b of the valve shaft of the rocker arm 11 for high speed,
A plunger 17 that is slidably provided in the hydraulic chamber 16 and laterally projects toward the low speed rocker arms 9 and 10 when the pressure in the hydraulic chamber 16 becomes high, and a high speed rocker arm 11 The low-speed rocker arms 9 and 10 corresponding to the positions of the plungers 17 when the low-speed rocker arms 9 and 10 are in contact with the base circles of the cams 4a, 4b, and 5 respectively. The fitting hole 18 of the plunger 17 formed in each of the above, and the plunger provided in the fitting hole 18 when the pressure in the hydraulic chamber 16 is low.
The receiver 20 and the like push back 17 to the hydraulic chamber 16 side with a return spring 19.

As shown in FIG. 2, the hydraulic chamber 16 is connected to an oil passage 8a in the rocker shaft 8 through an oil supply passage 21 formed in the rocker shaft 8 and the high-speed rocker arm 11, and Through the oil supply passage 21, the lubricating oil pumped into the oil passage 8a is supplied as hydraulic oil.

In addition, the oil passage 8a in the rocker shaft 8 has a fifth
As shown in the figure, the lubricating oil in the oil pan 26 is pumped and supplied by the oil pump 27, and the return passage from the oil passage 8a of the rocker shaft 8 to the oil pan 26 has the above-mentioned structure. A solenoid valve 28 for adjusting the pressure in the oil passage 8a is provided. Note that the oil pump 27 is driven to rotate by the crankshaft of the engine, so that the discharge pressure thereof rises to a high pressure when the engine rotates at a high speed, and the discharge pressure thereof decreases when the engine rotates at a low speed. Although the pressure becomes low, the pressure in the oil passage 8a is controlled by controlling the opening degree of the solenoid valve 28.
When the engine speed is lower than the set speed, the low pressure leans to a substantially constant value, and when the engine speed is higher than the set speed, the high pressure leans to a substantially constant value.

By the way, the low-speed cams 4a and 4a and the high-speed cam 5 described above.
As shown in FIG. 4, the cam lift curves (valve opening / closing operation characteristics) are set to be equal to or extremely close to each other for at least the first half of the predetermined period T from the start of valve opening to the maximum lift. To be done. That is, (a) in FIG. 4 shows the cam lift curve of the high speed cam 5, (b)
Shows the cam lift curves of the low speed cams 4a and 4b, respectively. The cam lift curves (a) and (b) have slightly different valve opening timings, and the high speed cam 5 has the low speed cams 4a and 4b.
Although the valve opening timing is earlier than b, low speed cams 4a and 4b
From immediately after the start of the lift up to immediately before the maximum lift of the low speed cams 4a and 4b, they are matched for as long as possible.

Here, the opening timing differs, because it is better to advance the opening timing of the intake valves 1 and 1 to increase the overlap period in order to improve the intake charging efficiency at high engine speeds. However, within the practical engine speed range, the difference in valve lift amount is more important than the difference in valve lift timing.
In this embodiment, the valve lift is regarded as important.

Therefore, in the engine valve operating system thus configured,
In the high speed rotation range of the engine, the oil passage of the rocker shaft 8
The pressure of the lubricating oil pumped into 8a is made high, and this highly hydraulic lubricating oil is supplied as hydraulic oil into the hydraulic chamber 16 of the rocker arm 11 for high speed through the oil supply passage 21. Then, the plunger 17 is fitted into the fitting hole 18 of the low speed rocker arm 9/10, the high speed rocker arm 11 engages with the low speed rocker arm 9/10, and they are integrated and brought into an interlocking state. The intake valves 1.1 are opened and closed by the high speed cam 5.

On the other hand, when the engine is running at low speed, the rocker shaft 8
The pressure of the lubricating oil that is pressure-fed to the oil passage 8a therein is made low, so that the pressure in the hydraulic chamber 16 also drops. Then, the plunger 17 is pushed back into the hydraulic chamber 16 by the return spring 19 of the receiver 20, whereby the high speed rocker arm 11 is disengaged from the low speed rocker arm 9. The valve 1.1 is opened and closed by the low speed cams 4a and 4b. At this time, the low-speed rocker arms 9 and 10 and the high-speed rocker arm 11 have the low-speed cams 4a and 4b and the high-speed cam 5 respectively.
Although it is slidably contacted with and swings independently, in this embodiment, the cam lift curves of the high speed cam 5 and the low speed cams 4a and 4b are matched on the valve lift start side. During the period when the curves are matched, the low-speed rocker arms 9 and 10 and the high-speed rocker arm 11 move in exactly the same way, and relative movement does not occur between them, and there is a deviation in the valve lift curve. The low-speed rocker arms 9 and 10 and the high-speed rocker arms 11 toward the latter half
There will be relative movement between and.

On the other hand, the pressure of the lubricating oil supplied to the oil passage 8a in the rocker shaft 8, that is, the pressure in the pressure chamber 16 does not depend on the rotation direction of the cam shaft 3, that is, the low-speed rocker arm 9.
Regardless of whether the high speed rocker arm 11 and the high speed rocker arm 11 are lifted or not lifted, depending on the engine speed, a low pressure that causes the operation switching means 15 to be in the non-interlocking state in the low speed rotation range and an operation in the high speed range Since the pressure is adjusted to a high pressure that brings the switching means 15 into an interlocking state, the low-speed rocker arm 9/10
And operation switching means during lift between high-speed rocker arm 11 and
The switching operation of 15 may start up.

However, as described above, the low-speed cams 4a and 4b and the high-speed cam 5 have the same valve lift curves on the lift start side for a predetermined period. Even when the switching operation of the operation switching means 15 is started up, relative movement between the low speed rocker arms 9 and 10 and the high speed rocker arm 11 has not occurred, so that the shaft of the plunger 17 and the fitting hole 18 is not moved. Since the cores match, the switching from the non-interlocking state to the interlocking state and the switching from the interlocking state to the non-interlocking state are both performed smoothly and reliably.

Therefore, the rocker arm 11 for high speed and the rocker arm 9 for low speed immediately after the intake valve 1.1 is lifted are started.
It becomes possible to prevent malfunctions as much as possible when switching between the linked state and the non-linked state with 10. In addition, even if the low-speed rocker arms 9 and 10 are switched to the non-interlocking state immediately after the start of the lift, the low-speed rocker arms 9 and 10 do not move.
It is possible to prevent the hammering sound from being generated as much as possible without dropping onto the 4b, and to prevent the durability of the operation switching means 15 and the like from being deteriorated as much as possible.

The graph of FIG. 6 shows the characteristics of the hydraulic pressure supplied in the hydraulic chamber 16 at the time of ON operation when switching from the non-interlocking state to the interlocking state, and the graph of FIG. 7 shows the characteristics of the switching from the interlocking state to the non-interlocking state. The characteristics of the supplied hydraulic pressure in the hydraulic chamber 16 at the time of OFF operation are shown, but as shown by the solid lines in these graphs, when switching to the interlocking state, the opening of the solenoid valve 28 can be instantaneously greatly reduced. Rocker shaft 8
The hydraulic pressure inside the hydraulic chamber 16 and the hydraulic chamber 16 can be quickly increased to a high pressure higher than the set pressure value P2 on the high pressure side by the effect of the so-called water hammer action. Conversely, when switching to the non-interlocking state, the solenoid valve 28 is opened. The pressure in the hydraulic chamber 16 can be quickly increased by opening the valve to a large degree instantaneously.
It can be reduced to a low pressure below P1.

Therefore, by doing so, the moving speed of the plunger 17 can be increased, and the defective switching operation can be further prevented. Even in this case, the high pressure of the set pressure value P2 or higher and the low pressure of the set pressure value P1 or lower are set for a short period of time, so that there is no possibility that the lubricity of the valve mechanism may be affected.

<Effect> In summary, according to the present invention, in the high rotation range of the engine, the operation switching means engages the low speed rocker arm and the high speed rocker arm to open / close the valve by the high speed cam to drive the valve in the low rotation range. Then, the operation switching means disengages the low-speed rocker arm and the high-speed rocker arm to open / close the valve by the low-speed cam. At this time, since the cam lift curves of the low speed cam and the high speed cam are close to each other in the initial portion after the valve is opened, when the low speed rocker arm and the high speed rocker arm are disengaged from each other in the initial portion. However, relative movement to them hardly occurs. Therefore, even if the switching operation of the operation switching means rises due to the initial portion thereof, the switching operation is smoothly and surely performed and no malfunction occurs, and the low-speed rocker arm and the high-speed rocker arm are Even when the engagement is released, the low speed rocker arm does not drop onto the low speed cam.

Also, the valve opening timing of the high speed cam is set earlier than the valve opening timing of the low speed cam so that the overlap period of the intake / exhaust valve at the time of high engine rotation is longer than that at the time of low engine rotation. It is possible to improve the charging efficiency of intake air at high rotation speed.

[Brief description of drawings]

1 to 3 show an embodiment in which the engine valve operating system of the present invention is applied to the intake valve side of a three-valve system engine, and FIG. 1 is a side sectional view showing the overall configuration of the present invention. 2 is a sectional view of the main part in FIG. 1, FIG. 3 is a plan view of the intake valve side, and FIG. 4 is a low speed cam and a high speed cam adopted in the present invention. FIG. 5 is a diagram showing an example of a valve lift curve, FIG. 5 is a diagram showing an example of a lubricating oil pressure-feeding device, and FIG. 6 is a graph diagram showing an example of characteristics of hydraulic pressure supplied to a hydraulic chamber when switching to a linked state. FIG. 7 is a graph showing an example of the characteristics of the hydraulic pressure supplied to the hydraulic chamber when switching to the non-interlocked state. 1 …… (Intake) valve, 3 …… Cam shaft 4a ・ 4b …… Low speed cam, 5 …… High speed cam 8 …… Rocker shaft, 9 ・ 10 …… Low speed rocker arm 11 …… High speed rocker arm , 15 …… Operation switching means

Claims (1)

(57) [Claims] Claims: 1. A high speed cam and a low speed cam, each having a different lift amount, are formed on a cam shaft, and the low speed cam is suspended between a valve and a low speed cam so as to be swingably supported by a rocker shaft. Rocker arm for the high speed rocker, which is adjacent to the side of the low speed rocker arm, one end of which abuts against the high speed cam of the cam shaft and is pivotally supported on the rocker shaft. An engine provided with an arm, and the high-speed rocker arm and the low-speed rocker arm on the side of the arm are provided with operation switching means for engaging and disengaging them according to the engine speed to switch the opening / closing operation characteristics of the valve. In the valve operating device of the above, the cam lift curves of the low speed cam and the high speed cam are as follows.
Further, the engine valve operating device is characterized in that the initial portions of both lift curves after valve opening are set to be close to each other.