JPH0343444B2 - - Google Patents

Description

[Detailed Description of the Invention] A. Purpose of the Invention (1) Industrial Field of Application The present invention provides a system in which a plurality of cam followers including a cam follower provided with a hydraulic tappet that contacts an intake valve or an exhaust valve responds to the rotation of a camshaft. It has a switching pen which is arranged adjacently so as to be able to operate in mutually different manners and moves between a position where the cam follower is connected and a position where the cam follower is disconnected in response to switching between high oil pressure and low oil pressure to the hydraulic chamber. A connection switching mechanism is provided between the cam followers, and between the hydraulic pressure supply path common to the hydraulic chamber and the hydraulic tappet of the connection switching mechanism and the hydraulic pressure supply source, high hydraulic pressure and low hydraulic pressure are switched and supplied to the hydraulic pressure supply path. The present invention relates to a valve train for an internal combustion engine that is provided with a hydraulic pressure switching means.

(2) Conventional technology Conventionally, such a valve train has been developed, for example, in
It is known from the publication No. 81510.

(3) Problems to be Solved by the Invention In the above-mentioned conventional technology, hydraulic pressure is supplied to the hydraulic tappet and the connection switching mechanism from a common hydraulic supply path. When the oil pressure of the road changes, the oil pressure supplied to the hydraulic tappet also changes, which may cause abnormal operation of the hydraulic tappet depending on the conditions.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a valve operating system for an internal combustion engine that stabilizes the hydraulic pressure supplied to a connection switching mechanism and a hydraulic tappet.

B. Structure of the Invention (1) Means for Solving the Problems According to the present invention, the hydraulic pressure switching means includes a first relief valve that releases the hydraulic pressure when the hydraulic pressure exceeds a relatively high set pressure. a first oil passage that has a hydraulic pressure supply line and communicates with the hydraulic pressure supply passage; a second oil passage that has a second relief valve that releases the hydraulic pressure when the hydraulic pressure exceeds a relatively low set pressure; The hydraulic tappet is equipped with a switching valve capable of switching between a state in which the oil pressure is communicated with the hydraulic pressure supply passage through the first oil passage and a state in which the hydraulic pressure from the hydraulic pressure supply source is throttled and the hydraulic pressure is communicated with the hydraulic pressure supply passage through the second oil passage. The cam follower with
The oil passage connecting the hydraulic supply passage and the hydraulic tappet is
A switching pin of the connection switching mechanism is provided to narrow the middle of the oil passage, and the switching pin is configured to increase the degree of narrowing at a position when high oil pressure is supplied to the hydraulic chamber.

(2) Effect According to the above configuration, when high hydraulic pressure is supplied to the hydraulic pressure supply path, the upper limit of the high hydraulic pressure is determined by the first relief valve, and when low hydraulic pressure is supplied to the hydraulic pressure supply path, the upper limit of the high hydraulic pressure is determined by the second relief valve. Since the upper limit of the hydraulic pressure is determined, the hydraulic pressure acting on the hydraulic chamber of the connection switching mechanism can be stabilized, and the operation of the connection switching mechanism can be stabilized. Moreover, the hydraulic pressure acting on the hydraulic tappet can be made almost constant by changing the degree of restriction in accordance with the movement of the switching pin, and the operation of the hydraulic tappet can be stabilized.

(3) Embodiment An embodiment of the present invention will be described below with reference to the drawings. First, in FIGS. 1 and 2, a pair of intake valves 1, 1 provided in the engine body E are A low-speed cam 4, a high-speed cam 5, and a low-speed cam 4 that are integrally provided on a camshaft 2 that is rotatably driven at a reduction ratio of 1/2, and a cam follower that is pivotally supported on a rocker shaft 6 that is parallel to the camshaft 2. The first, second, and third rocker arms 7, 8, and 9 and the connection switching mechanism 10 provided between each of the rocker arms 7 to 9 are operated to open and close.

The camshaft 2 is rotatably disposed above the engine body E, the low-speed cams 4 are integrated into the camshaft 2 at positions corresponding to both the intake valves 1, 1, and the high-speed cam 5 is integrated with the camshaft 2 at positions corresponding to both the intake valves 1, 1. It is integrated into the camshaft 2 between the low speed cams 4, 4. Both low-speed cams 4, 4 each have a high portion 4a having a relatively small amount of protrusion along the radial direction of the camshaft 2, and a base circular portion 4b. Further, the high-speed cam 5 has a protrusion amount along the radial direction of the camshaft 2 that is equal to the height of the high portion 4.
It has a high part 5a which is larger than 4a and has a center angle range wider than that of the high part 4a, and a base circular part 5b.

The rocker shaft 6 is fixedly arranged below the camshaft 2. This locker shaft 6 includes a first locker arm 7 that is interlocked and connected to one intake valve 1, a third locker arm 9 that is interlocked and connected to the other intake valve 1, and a locker arm 9 that is interlocked and connected to the other intake valve 1. The second rocker arm 8 located in
are adjacent to each other and are respectively pivotally supported. Further, a cam slipper 11 that slides on the low-speed cam 4 is provided on the top of the first rocker arm 7, a cam slipper 12 that slides on the high-speed cam 5 is provided on the top of the second rocker arm 8, and a cam slipper 12 that slides on the high-speed cam 5 is provided on the top of the third rocker arm 9. is a cam slipper 13 that comes into sliding contact with the low-speed cam 4
is provided.

On the other hand, a flange 14 is provided on the upper part of both the intake valves 1, 1, and a valve spring 16 is interposed between the flange 14 and the engine body E. 1 is biased toward the valve closing direction, that is, upward. Further, the first and third rocker arms 7, 9 are each provided with a hydraulic tappet T at the tip thereof, each having a discharge hole 18 at the upper end. It comes into contact with the intake valves 1,1.

Referring also to FIG. 3, the second rocker arm 8
is slightly extended from the lock shaft 6 toward both intake valves 1, 1, and this second lock shaft arm 8
is a spring biasing means 19 provided between the engine body E
is elastically biased in the direction of sliding contact with the high-speed cam 5.

The spring biasing means 19 includes a bottomed cylindrical lifter 20 whose closed end is in contact with the second rocker arm 8, and a lifter spring 21 interposed between the lifter 20 and the engine body E. is slid into a bottomed hole 22 bored in the engine body E.

In FIG. 4, a connection switching mechanism 10 is provided between each rocker arm 7 to 9 for switching between connection and disconnection.

The connection switching mechanism 10 includes a first switching pin 23 that can connect the third and second rocker arms 9 and 8;
A second switching pin 24 that can connect the second and first rocker arms 8 and 7, and a third switching pin 25 that restricts the movement of the first and second switching pins 23 and 24.
and a return spring 26 that urges each of the switching pins 23 to 25 toward the disconnection side.

A first guide hole 27 parallel to the rocker shaft 6 is bored in the third rocker arm 9, and the end of the first guide hole 27 on the opposite side from the third rocker arm 8 is closed with a closing member 28. . The first switching pin 23 is slidably engaged with the first guide hole 27 , and a hydraulic chamber 29 is defined between the closing member 28 and the first switching pin 23 within the first guide hole 27 .
Further, a communication passage 30 communicating with the hydraulic chamber 29 is bored in the third rocker arm 9, and a hydraulic pressure supply passage 31 is provided in the rocker shaft 6. Moreover, the communication path 30 and the hydraulic supply path 31 are connected to the rock shaft 6.
The third rocker arm 9 is always in communication through a communication hole 32 formed in the side wall of the rocker arm 9, regardless of the swinging state of the third rocker arm 9.

In the second rocker arm 8, a second guide hole 33 having the same diameter as the first guide hole 27 is bored between both sides of the second rocker arm 8 in parallel with the rocker shaft 6. A second switching pin 24 having a length spanning the entire length of the second switching pin 24 is slidably engaged.

A third guide hole 34 having the same diameter as the second guide hole 33 is bored in the first rocker arm 7 in parallel with the rocker shaft 6, and the third guide hole 34 is located on the opposite side of the second rocker arm 8. The end portion of is closed with a closing member 35. A third switching pin 25 is slidably connected to the third guide hole 34.
A shaft portion 36 coaxially connected to the switching pin 25 is movably inserted into a guide hole 37 formed in the closing member 35 . Moreover, the closing member 35 surrounds the shaft portion 36.
A return spring 26 is interposed between the third switching pin 25 and the third switching pin 25 . The return spring 26 urges the switching pins 23 to 25 that are in contact with each other toward the connection release side, that is, toward the hydraulic chamber 29 side.

When relatively low pressure, for example, 1 kg/cm ² hydraulic pressure is supplied to the hydraulic chamber 29, each switching pin 23 to 25
is moved toward the connection release side by the spring force of the return spring 26, and in this state, the contact surfaces of the first and second switching pins 23, 24 are at the position corresponding to between the third and second rocker arms 9, 8. The contact surfaces of the second and third switching pins 24 and 25 are
It is located at a corresponding position between the rocker arms 8 and 7, and the rocker arms 7 to 9 are not connected. Further, when a relatively high pressure, for example, 3 kg/ ^cm2 , is supplied to the hydraulic chamber 29, each of the switching pins 23 to 25 moves in a direction away from the hydraulic chamber 29 against the spring force of the return spring 26, and the first The switching pin 23 slides into the second guide hole 33, the second switching pin 24 slides into the third guide hole 34, and the rocker arms 7 to 9 are connected.

On the outer peripheral surface of the third switching pin 25, a first annular orifice 40 having a relatively large cross-sectional area of a flow path formed between the third switching pin 25 and the inner surface of the third guide hole 34;
A second annular orifice 41 with a relatively small cross-sectional area of the flow path formed between the inner surface of the guide hole 34
are provided at intervals in the axial direction. Also the first
An oil passage 42 having one end communicating with the hydraulic tappet T and the other end opening into the third guide hole 34 is bored in the rocker arm 7, and one end is connected to the third guide hole 34 at a position corresponding to the oil passage 42. An oil passage 43 opened at 34 is bored, and the other end of this oil passage 43 is connected to a communication hole 4 bored in the side wall of the rock shaft 6.
4, it is constantly connected to the hydraulic pressure supply path 31. Moreover, the opening ends of the oil passages 42 and 43 toward the inner surface of the third guide hole 34 are connected to each other through the first annular orifice 40 when the third switching pin 25 is in the disconnected state due to low oil pressure acting on the hydraulic chamber 29. and communicate with each other, hydraulic chamber 2
They are arranged so that they communicate with each other via the second annular orifice 41 when the third switching pin 25 moves to the connecting position due to high hydraulic pressure acting on the switching pin 9 .

On the outer circumferential surface of the first switching pin 23, a first annular orifice 45 with a relatively large cross-sectional area of a flow path formed between the first switching pin 23 and the inner surface of the first guide hole 27 is provided.
A second annular orifice 46 with a relatively small cross-sectional area of the flow path formed between it and the inner surface of the guide hole 27
are provided at intervals in the axial direction. Also the third
The rocker arm 9 is provided with an oil passage 47 which has one end communicating with the hydraulic tappet T and the other end opening into the inner surface of the first guide hole 27 . At the same time, an oil passage 48 whose other end communicates with the communication passage 30 is bored. Moreover, the first guide hole 2 of the oil passages 47 and 48
7 are in communication with each other via the first annular orifice 45 when low hydraulic pressure acts on the hydraulic chamber 29 and the first switching pin 23 is in the disconnected position, and the high hydraulic pressure is applied to the hydraulic chamber 29. When the first switching pin 23 moves to the connecting position due to the action of the first switching pin 23, the first switching pin 23 is arranged to communicate with each other via the second annular orifice 46.

The hydraulic pressure supply path 31 in the rock shaft 6 is connected to a hydraulic pump 51 as a hydraulic pressure supply source via a hydraulic pressure switching means 50. This hydraulic switching means 50
is a high-speed position where the first oil passage 52 communicates with the hydraulic pump 51, a throttle 54, and a The switching valve 55 connects the hydraulic pump 51 and the first oil passage 52 via the second oil passage 53 and is capable of switching the low speed position. It switches from position to high speed position. Moreover, a first relief valve 56 is connected in the middle of the first oil passage 52 to release the oil pressure when the oil pressure in the oil passage 52 reaches a relatively high pressure, for example, 3 kg/cm ² or more.
A second relief valve 57 is connected in the middle of the second oil passage 53 to release the oil pressure when the oil pressure in the oil passage 53 reaches a relatively low pressure, for example, 1 kg/cm ² or more.

Next, the operation of this embodiment will be explained. When the engine is operating at low speed, the switching valve 55 is in the switching position shown in FIG. 53 and 1st
It is supplied to the hydraulic pressure supply path 31 via the oil path 52. As a result, the upper limit of the oil pressure supplied from the oil pressure supply path 31 to the oil pressure chamber 29 is set by the second relief valve 57, and becomes almost constant regardless of the increase in rotation speed, as shown by straight line A in FIG. . Further, since the first and third switching pins 23, 25 are in the disconnection position, the hydraulic pressure supplied from the hydraulic pressure supply path 31 to each hydraulic tappet T, T is applied to the first annular orifice 40, 45.
The pressure is reduced and becomes constant as shown by straight line B. In this state, each of the switching pins 23 to 25 of the connection switching mechanism 10 is at the connection release position, and each of the rocker arms 7 to 9 is not connected. Therefore, the intake valves 1, 1, which are interlocked and connected to the first and third rocker arms 7, 9, open and close at a timing and lift amount depending on the shape of the low-speed cams 4, 4.

When the engine is operating at high speed, the switching valve 55 is switched to the high speed position, and the first oil passage 52 is communicated with the hydraulic pump 51 without going through the throttle 54. This allows the first
The oil pressure supplied to the oil passage 52 should increase as the rotation speed increases, as shown by the broken line, but the first
It is kept constant as shown by straight line C by the action of the relief valve 56. Also, at this time, as the first and third switching pins 23, 25 move to the connected position, the hydraulic pressure in the supply oil passage 31 is supplied to each hydraulic tappet T, T via the second annular orifice 41, 46. Therefore, the second annular orifice 41,
The degree of aperture due to 46 is the first annular orifice 40,4
5, the hydraulic pressure supplied to each hydraulic tappet T, T can be kept constant as shown by straight line B in FIG. Therefore, the operation of the connection switching mechanism 10 is stabilized during high-speed running, and the hydraulic pressure supplied to each hydraulic tappet T, T is stabilized, so that the operation of the hydraulic tappets T, T can be stabilized.

When high hydraulic pressure is supplied to the hydraulic chamber 29 in this way, the first to third rocker arms 7 to 9 are connected, and the intake valves 1 and 1 are opened and closed at timing and lift amount according to the shape of the high-speed cam 5. .

The present invention is applicable not only to the intake valves shown in the above embodiments but also to exhaust valves.

C. Effects of the Invention As described above, according to the present invention, the hydraulic pressure switching means has a first relief valve that releases the hydraulic pressure when the hydraulic pressure exceeds a relatively high set pressure, and the hydraulic pressure switching means is connected to the hydraulic pressure supply path. A first oil passage that communicates with the oil pressure, and a second oil passage that releases the oil pressure when the oil pressure reaches a relatively low set pressure or higher.
A second oil passage having a relief valve, a condition in which a hydraulic pressure supply source is communicated with the hydraulic pressure supply passage through the first oil passage, and a state in which the hydraulic pressure from the hydraulic pressure supply source is throttled and communicated with the hydraulic pressure supply passage through the second oil passage. The cam follower is equipped with a switching valve that can switch between a closed state and a hydraulic tappet, and has an oil passage connecting the hydraulic pressure supply passage and the hydraulic tappet. The switching pin is
Since the configuration is configured to increase the degree of restriction at the position when high oil pressure is supplied to the hydraulic chamber, almost constant high and low oil pressures are supplied to the hydraulic chamber of the connection switching mechanism, and the connection switching mechanism The operation of the hydraulic tappet can be stabilized, and the hydraulic pressure supplied to the hydraulic tappet can be kept almost constant regardless of the rotational speed, thereby stabilizing the operation of the hydraulic tappet.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a plan view, FIG. 2 is a cross-sectional view taken along the line -- in FIG. 1, FIG. 3 is a cross-sectional view taken along the line -- in FIG. 1, and FIG. is a sectional view taken along the line -- in FIG. 2, and FIG. 5 is a diagram showing changes in the supplied oil pressure. 1... Intake valve, 2... Camshaft, 7, 8,
9...Lotsuka arm as a cam follower, 10
...Connection switching mechanism, 23, 24, 25...Switching pin, 29...Hydraulic pressure chamber, 31...Hydraulic pressure supply path, 4
2, 43, 47, 48...oil passage, 50...hydraulic switching means, 51...hydraulic pump as a hydraulic pressure supply source, 52...first oil passage, 53...second oil passage, 54
... throttle, 55 ... switching valve, 56 ... first relief valve, 57 ... second relief valve, T ... hydraulic tappet.

Claims (1)

[Claims] 1 A plurality of cam followers, including a cam follower provided with a hydraulic tappet that contacts the intake valve or exhaust valve, are arranged adjacent to each other so that they can operate in different manners depending on the rotation of the camshaft, and the positions and connections for connecting the cam followers are determined. A connection switching mechanism having a switching pen that moves between the release position and the release position in response to switching between high and low oil pressure to the hydraulic chamber is provided between the cam followers, and a connection switching mechanism that is common to the hydraulic chamber and hydraulic tappet of the connection switching mechanism is provided. In a valve train for an internal combustion engine, a hydraulic pressure switching means is provided between a hydraulic pressure supply path and a hydraulic pressure supply source for switching and supplying high hydraulic pressure and low hydraulic pressure to the hydraulic pressure supply path. a first oil passage communicating with the hydraulic pressure supply passage and having a first relief valve that releases the hydraulic pressure when the hydraulic pressure exceeds a relatively low set pressure; the second to release the hydraulic pressure to
A second oil passage having a relief valve, a condition in which a hydraulic pressure supply source is communicated with the hydraulic pressure supply passage through the first oil passage, and a state in which the hydraulic pressure from the hydraulic pressure supply source is throttled and communicated with the hydraulic pressure supply passage through the second oil passage. The cam follower is equipped with a switching valve that can switch between a closed state and a hydraulic tappet, and has an oil passage connecting the hydraulic pressure supply passage and the hydraulic tappet. The switching pin is
A valve train for an internal combustion engine, characterized in that it is configured to increase the degree of restriction at a position when high hydraulic pressure is supplied to a hydraulic chamber.