JPH08284630A - Variable valve timing lift device and retarder device for engine - Google Patents

Abstract

PURPOSE: To control changeover of a valve without influencing on lubrication of a rocker arm and make the size of parts small. CONSTITUTION: A first rocker arm 23 swinging by a first cam 21 and lifting an exhaust valve 22 and a second rocker arm 26 swinging by a second cam 25 are connected together or disconnected from each other by advancing or retreating movement. This device is provided with a control oil pressure chamber 44 connected to a control oil pressure circuit 47 separated from a rocker arm lubricating circuit partitioned off with cam brackets 40 and receiving a changeover pin 27 capably of being advanced and retreated, a load receiving pin 56 provided on the first rocker arm 23 and energized on the second rocker arm 26 side, and a load transmitting pin 62 pushing the load receiving pin 56 by advance of the changeover pin 27 provided on the second rocker arm 26 so as to engage with the first rocker arm 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable valve timing / lift device and a retarder device for a diesel engine or the like.

[0002]

2. Description of the Related Art It is known that a valve operating system is provided with a variable mechanism in order to change a valve lift curve (timing lift) according to engine operating conditions. For example, as shown in FIG. 9, in Japanese Patent Laid-Open No. 59-231118, rocker arms 1 and 2 for respectively lifting a pair of intake valves (or exhaust valves) are connected or disconnected by controlling the plunger 3 to move back and forth. A configuration is disclosed. The plunger 3 is provided on one of the rocker arms 2 and protrudes toward the other rocker arm 1 side when the hydraulic pressure is supplied to the hydraulic action chamber 4 thereof, and pushes the guide pin 5 provided coaxially to the hole 6 thereof. The locker arms 1 and 2 are integrally connected to each other.

On the other hand, as an auxiliary braking mechanism (retarder) for an engine, a configuration is known in which a braking force is obtained by releasing a compression pressure in a cylinder. As shown in FIG. 10, in the conventional retarder of this type, a piston 12 is provided at the head of the exhaust valve 11, and the piston 12 is connected to the hydraulic circuit 1.
By pushing with a high hydraulic pressure appropriately supplied via 3, the exhaust valve 11 is lifted small before the lift (exhaust stroke) by the rocker arm 14 and a large engine braking force is generated.

[0004]

By the way, in the variable valve operating device of FIG. 9, the rocker arm lubrication circuit 8 formed in the rocker shaft 7 is used to supply the hydraulic pressure to the hydraulic working chamber 4. However, there was a problem in that the lubricating pressure fluctuates due to the switching pressure, and the rocker arm lubricating function deteriorates. If it is attempted to obtain the switching control hydraulic pressure after securing this lubricating pressure, the overall hydraulic pressure rises, leading to excessive oil consumption. Further, since the plunger 3 has both a switching function that operates under control hydraulic pressure and a load transmitting function that transmits a large rocking force of the rocker arms 1 and 2, the pin diameter is set to withstand the large bending moment. It is necessary to increase the size, which hinders the miniaturization and weight reduction of parts, and there is a problem that it is difficult to achieve compatibility with the optimum response surface of hydraulic control.

In addition, in the retarder of FIG. 10, since the block 15 having the hydraulic circuit 13 is installed, a large space is required in the upper part of the cylinder head (inside the cylinder head cover), and high hydraulic pressure causes a change in temperature. Since it is affected, there is a problem that it is difficult to achieve highly reliable control.

In view of the above circumstances, therefore, the present invention enables switching control without adversely affecting rocker arm lubrication.
The invention was also devised to provide a variable valve timing / lift device for an engine, which enables miniaturization of parts. It was created to provide a space-saving and highly reliable retarder device.

[0007]

SUMMARY OF THE INVENTION According to the present invention, a variable valve timing of an engine for controlling switching of an intake valve or an exhaust valve by connecting / disconnecting a plurality of rocker arms swinging by respective cams by advancing / retreating motions of a switching pin. In the lift device, a control hydraulic chamber for advancing and retracting the switching pin is divided into a fixed system separated from the rocker arm and connected to a control hydraulic circuit separate from the rocker arm lubrication circuit. Further, according to the present invention, a first rocker arm that swings by a first cam to appropriately lift an intake valve or an exhaust valve and a second rocker arm that swings by a second cam are connected by a forward / backward movement of a switching pin. In the variable valve timing / lift device of the engine to be released, a control hydraulic chamber that is partitioned into a fixed system that is isolated from the rocker arm and that is connected to a control hydraulic circuit that is separate from the rocker arm lubrication circuit and that houses the switching pin in a retractable manner. The load receiving pin provided on the first rocker arm and urged to the second rocker arm side, and the load receiving pin provided on the second rocker arm that pushes the load receiving pin due to the advance of the switching pin engages with the first rocker arm. And a load transmission pin for integrally connecting the rocker arm. The present invention has a first rocker arm that swings by a first cam having a predetermined exhaust stroke profile to appropriately lift the exhaust valve, and a compression pressure release profile that is provided in parallel with the first rocker arm. The second rocker arm that swings by the second cam, the switching pin that moves forward and backward by the supply of control hydraulic pressure, and the switching pin that is partitioned by the cam bracket and is connected to a control hydraulic circuit that is separate from the rocker arm lubrication circuit The control hydraulic chamber to be housed in, the load receiving pin provided on the first rocker arm and biased to the second rocker arm side, and the load receiving pin pushed by the advance of the switching pin provided on the second rocker arm. And a load transmission pin that engages with the first rocker arm and integrally connects the rocker arms.

[0008]

With the above structure, when the control oil pressure is supplied to the control oil pressure chamber by the control oil pressure circuit separate from the rocker arm lubrication circuit, the switching pin moves out of the fixed system to connect a pair of rocker arms to the intake valve. Alternatively, the timing / lift of the exhaust valve is switched. Further, due to the configuration including the load receiving pin and the load transmitting pin, when the switching pin moves out of the fixed system by the hydraulic pressure supply to the control hydraulic chamber, the load transmitting pin pushes the load receiving pin to move the first rocker arm and the first rocker arm. The second rocker arm is integrally connected. The first rocker arm swings according to the profile of the second cam to lift the intake valve or the exhaust valve appropriately. Also, with the configuration including the first rocker arm that lifts the exhaust valve, when hydraulic pressure is supplied to the control hydraulic chamber, the switching pin advances from the cam bracket and pushes the load receiving pin via the load transmitting pin. , A load transfer pin integrally connects the first rocker arm and the second rocker arm. The first rocker arm lifts the exhaust valve according to the profile of the second cam, releasing the compression pressure in the cylinder and generating the engine braking force.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

1 to 3 show an embodiment of a variable valve timing lift device for an engine according to the present invention. This device includes a first rocker arm 23 that swings by a first cam 21 to appropriately lift an exhaust valve 22.
And a second rocker arm 26 swinging by a second cam 25 provided on the cam shaft 24 common to the first cam 21. These rocker arms 23, 26 are appropriately moved by the forward / backward movement of the switching pin 27. It is configured to connect and disconnect. The first cam 21 is formed with an exhaust stroke profile for normal combustion, and the second cam 25 is formed with a compression pressure release profile that releases the compression pressure prior to the exhaust stroke. That is, as shown in FIG. 7, the cams 21 and 25 have the same basic circular portion, and the large diameter portion 28 of the second cam 25 is the center of the large diameter portion 29 of the first cam 21. The center angle β is smaller than the angle α (for example, β = about 30 °) and is formed low (to a short radius). The end 30 of the large diameter portion 28 of the second cam 25 has a predetermined angle θ (for example, about 30 degrees) from the start end 31 of the large diameter portion 29 of the first cam 21 to the upstream side in the rotation direction A.
50 °) apart. As shown in FIGS. 1 and 3, the exhaust valve 22 is provided in a pair in each cylinder 32, and the head portion thereof has a bridge 33 and a valve clearance adjusting screw 34.
It is engaged with the one end portion 35 of the first rocker arm 23 via. Further, a pair of intake valves 36 is provided at a position facing the exhaust valve 22 of the cylinder 32, and a rocker arm 37 and a cam 38 for appropriately lifting the intake valves 36 are provided. Further, a fuel injection valve 39 is arranged in the center of the cylinder 32.

Next, the switching pin 27 is a cylindrical pin body 2
7a and a brim portion 27b formed at the tip thereof, and is provided on a protruding portion 41 formed on the cam bracket 40. The cam bracket 40 is fixed to the cylinder head 42 with bolts 43 to pivotally support the cam shaft 24, is formed as a half-divided structure that is vertically divided at the axial center position of the cam shaft 24, and is fitted to the cam shaft 24. The bearing member 65 is provided in the portion to be used. The protrusion 41 is formed at a predetermined height on the upper surface of the upper cam bracket 42a, and a control hydraulic chamber 44 is defined inside the protrusion 41. The control hydraulic chamber 44 is formed of a substantially cylindrical hole extending parallel to the cam shaft 24, has a diameter substantially the same as that of the pin body 27a of the switching pin 27,
In addition, the rocker arm 2 is formed to be appropriately longer than its length.
It is opened on the 3 and 26 side. That is, the switching pin 27 is slidably accommodated and a predetermined control hydraulic pressure is supplied between the switching pin 27 and the base end of the pin body 27a, so that the switching pin 27 is appropriately advanced to the rocker arms 23, 26 side. It is like this. A control hydraulic circuit 47, which is formed separately from a rocker arm lubrication circuit 46 partitioned in a rocker shaft 45, is connected to the control hydraulic chamber 44, and a switching control valve (not shown) is operated by a switch operation or the like. It operates to supply and discharge a predetermined hydraulic pressure. The control hydraulic circuit 47 includes the protrusion 41.
The upper cam bracket 40a may be formed so as to be connected to the upper end of the upper cam bracket 40a.

The other end 48 of the first rocker arm 23 is provided with a roller 49 for engaging the first cam 21. The roller 49 is supported by a roller shaft 50 parallel to the rocker shaft 45. An oil passage 53 for guiding lubricating oil from the rocker arm lubricating circuit 46 to the roller shaft 50 is formed in the arm 52 from the shaft portion 51 of the first rocker arm 23 to the other end portion 48. And the other end 48
A bulging portion 54 having a shape substantially similar to that of the protruding portion 41 of the cam bracket 40 is formed on the upper portion of the roller shaft 50.
The bulging portion 54 is formed with a guide hole 55 that opens toward the cam bracket 40. The guide hole 55 is for the roller 49
Is formed so as to be coaxial with the control hydraulic chamber 44 when it is in sliding contact with the basic circular portion of the first cam 21 (state of FIG. 1). The load receiving pin 5 is inserted into the guide hole 55.
6 is provided slidably. The load receiving pin 56 is
The switching pin 27 has an outer diameter substantially equal to that of the flange portion 27b, and a concave portion 57 that is open to the side opposite to the cam bracket 40 side is formed in the axial center portion thereof. A return spring 58 is provided in the recess 57, and the load receiving pin 56 is switched to the switching pin 2
It is urged to the 7 side. A small hole 59 for venting air is formed on the wall surface of the bulging portion 54 on the side opposite to the opening of the guide hole 55.

The second rocker arm 26 is provided so as to be axially sandwiched between the cam bracket 40 and the first rocker arm 23, and is swingably supported by the rocker shaft 45. Arm 60 of the second rocker arm 26
Has a shape substantially similar to the arm 52 of the first rocker arm 23, a roller 61 engaging with the second cam 25 is provided at the lower part of the swing end, and a load transmission pin is provided at the upper part of the swing end. A sliding hole 63 is formed to slidably hold the 62. In the sliding hole 63, the roller 61 is the second cam 2
It is formed at a position coaxial with the control hydraulic chamber 44 and the guide hole 55 when it is in sliding contact with the basic circular portion of No. 5. The load transmission pin 62 is made of a thick-walled cylindrical body, has the same diameter as the flange portion 27b of the switching pin 27 and the load receiving pin 56, and slides so that both ends thereof come into contact with the pins 27, 56 as appropriate. It is formed longer than the hole 63. That is, in the load transmission pin 62, the switching pin 27 has the control hydraulic chamber 4
4, the load receiving pin 56 contacts the load receiving pin 56 at the opening end of the guide hole 55 (FIG. 1), and the switching pin 27
When is moved out of the control hydraulic chamber 44, the load receiving pin 56 is pushed to partially fit in the guide hole 55 (FIG. 2).

Further, in this embodiment, a lost motion mechanism 71 for appropriately pressing the second rocker arm 26 against the second cam 25 is provided. The lost motion mechanism 71 urges the plunger 72 that engages with the arm portion 60 of the second rocker arm 26, the bracket member 73 that holds the plunger 72 in a substantially horizontal state, and the plunger 72 in the protruding direction. It is composed of a lost motion spring 74. Plunger 72
It is formed of a cylindrical body having a hemispherical tip portion 72a and the other end of which is opened, and the tip portion 72a comes into contact with a projecting piece 75 formed at the upper end of the arm portion 60. The bracket member 73 is integrally formed with a rocker shaft bracket (not shown) for fixedly supporting the rocker shaft 45, and is located above the cam bracket 40.
It extends diagonally from 9 to above the shaft portion 64 of the second rocker arm 26. A holder portion 76 for holding the plunger 72 is formed at this extended end. The holder portion 76 is formed with a sliding hole 77 for accommodating the plunger 72 in a retractable manner. The lost motion spring 74 is stretched between the inner wall of the holder portion 76, which is the bottom surface of the sliding hole 77, and the inner wall of the tip portion 72a of the plunger 72. The bracket member 73
The base portion 79 is provided between the shaft portion of the rocker arm 37 for the intake valve 36 of the adjacent cylinder and the shaft portion 64 of the second rocker arm 26 with both axial ends in contact with each other ( (See FIG. 1). A bolt hole 78 for bolting the bracket member 73 to the rocker shaft 45 (or rocker shaft bracket body) is formed on the upper surface of the base 79.

Next, the operation of this embodiment will be described.

During normal operation of the engine, the control oil pressure chamber 44 is in a low pressure state where high pressure control oil pressure is not supplied. In this state, the pin body 27a of the switching pin 27 is recessed in the control hydraulic chamber 44, and one end of the load transmission pin 26 is slidable into the sliding hole 6
It projects from 3 and is in contact with the collar portion 27b. The other end of the load transmission pin 26 is in contact with the load receiving pin 56 at the position of the end surface of the bulging portion 54 of the first rocker arm 23 (FIG. 1). Therefore, the rocker arms 23 and 26 are independent of each other and swing according to the profile of the respective cams 21 and 25. That is, the exhaust valve 22 is opened by the first rocker arm 23 at a predetermined timing and lift to form an exhaust stroke in normal combustion of the engine. Further, the pins 27, 62, 56 slide on each other in the substantially radial direction at their end faces. The second rocker arm 26 has its roller 61 constantly pressed against the second cam 25 by the urging force of the lost motion spring 74, as shown in FIG.

When a large auxiliary brake is required, the control hydraulic circuit 47 supplies a predetermined high hydraulic pressure to the control hydraulic chamber 44. By this hydraulic pressure supply, each pin 2
In the state where 7, 62, 56 are coaxial, the switching pin 27 advances to the rocker arms 26, 23 side and pushes the load transmission pin 62 to move the other end side to the first rocker arm 23.
It is inserted into the guide hole 55 of (FIG. 2). Thus, the first rocker arm 23 and the second rocker arm 26 are integrally connected via the load transmission pin 62, and the first rocker arm 23 also follows the second cam 25 like the second rocker arm 26. Rock. Due to this swing, as shown in FIGS. 6 and 8, the exhaust valve 22 is slightly lifted prior to the normal exhaust stroke, and the compression pressure is released from the cylinder 32. That is, it functions as a retarder device that causes the engine to perform negative work. Ideally, this release should be near the top dead center of the piston,
Since the load applied to the rocker arms 23 and 26 becomes large when the compression pressure is high, in this embodiment, the rocker arms 23 and 26 are released after the combustion (expansion) stroke has slightly entered. As shown in FIG. 5, the second rocker arm 26 also swings according to the profile of the first cam 21, but this swing is received by the lost motion mechanism 71, and the second rocker arm 23 and the first rocker arm 23. Hold so that the movement is similar.

When the auxiliary brake is no longer necessary, the high pressure oil is drained from the control hydraulic chamber 44, and the load transmission pin 62
Is separated from the guide hole 55 by the urging force of the return spring 57 acting via the load receiving pin 56. The switching pin 27 is pushed by the load transmission pin 62,
The pin body 27a sinks into the control hydraulic chamber 44, and the collar 27b
Returns to the state of being in contact with the opening-side end surface of the protruding portion 41. With this, the connection between the rocker arms 23 and 26 is released, and thereafter,
The exhaust valve 22 is lifted only by the first rocker arm 23 that swings by the first cam 21.

As described above, the control hydraulic chamber 44 is provided above the cam bracket 40, which is a fixed system, and the switching pin 27 is provided by supplying / stopping the hydraulic pressure of the independent control hydraulic circuit 47.
Therefore, the reliability of rocker arm lubrication can be secured without any deterioration of the lubrication function or increase of the lubrication oil pressure due to the timing / lift switching control of the exhaust valve 22. The amount of oil in the control hydraulic circuit may be a minimum required amount, the oil feeding loss does not become excessive, and the switching control can be performed under the optimum hydraulic pressure condition, so that highly reliable switching control is achieved. Then, the switching pin 27 is operated by hydraulic pressure supply and only pushes the load transmission pin 62 in the axial direction.
A radial load (bending force) accompanying the rocking of 3, 26 does not act at all. Therefore, the pin body 27a can be made small and lightweight, and the pin diameter can be optimized for hydraulic control. The sliding contact between the switching pin 27 and the load transmission pin 62 is appropriately maintained by the collar portion 27b. Further, since the forward / backward movement of the switching pin 27 is determined only by the control hydraulic chamber 44 and the return spring 57, it is possible to easily optimize the balance between the residual pressure of the control hydraulic chamber 44 and the return spring 57 when the switching is OFF. Further, since the load transmission pin 62 is hollow, it can contribute to weight reduction of the parts, and the interior of the load transmission pin 62 can be made into a lubricating oil atmosphere so that the pins can smoothly slide at both ends of the load transmission pin 62. . This lubricating oil may be derived from the rocker arm lubrication circuit 46.

Since the variable valve timing / lift device is applied to the exhaust valve 22 and the rocker arms 23 and 26 are used to lift the exhaust valve 22 to release the compression pressure, the exhaust valve 22 is driven by high hydraulic pressure. Compared to the conventional retarder mechanism that directly pushes the cylinder, it does not require a large space inside the cylinder head cover, and because it is mechanical, the amount of oil used for switching control is small, so it is affected by temperature changes etc. There is no. That is, a space-saving and highly reliable engine retarder device is achieved, and a desired large auxiliary braking force can be obtained. For example, by adding this retarder device, the absorption horsepower can be increased by 40% compared with the absorption horsepower of the exhaust brake alone.

Also, the second rocker arm 26 causes the lost cam mechanism 7 to constantly follow the second cam 25.
Since No. 1 is provided, the swinging force of the second rocker arm 26 does not act on the valve spring (not shown) of the exhaust valve 22, and there is no need to change the design of the structure or the like. The plunger 72 and the lost motion spring 74 are provided in the upper part of the second rocker arm 26 in a substantially horizontal direction so as to obtain a biasing force against rocking around the rocker shaft 45. It does not require a lot of space above, and avoids high engine height. Furthermore, the bracket member 7
Since 3 is formed integrally with the rocker shaft bracket and its member strength is utilized, an increase in weight can be avoided and an excessive increase in the number of parts does not occur.

In this embodiment, the control oil pressure chamber 44 of the switching pin 27 is provided in the cam bracket 40, but it may be provided in another fixing member. Although the exhaust valve 22 is the valve to be switched, it may be applied to the intake valve 36. That is, by forming the cam with an appropriate profile and moving the switching pin 27 back and forth according to the load / rotation range of the engine, engine startability, stability in the low rotation range, and high output / low in the high rotation range are achieved. Fuel consumption can be improved. Further, the control hydraulic chamber 44 of the present invention can be applied regardless of the configuration of each pin, and has extremely effective effects of ensuring the reliability of rocker arm lubrication and improving the reliability of the switching control system. is there.

[0023]

In summary, according to the present invention, the following excellent effects are exhibited.

(1) According to the first aspect of the present invention, highly reliable valve switching control is achieved without affecting the rocker arm lubrication function.

(2) According to the second aspect of the invention, it is possible to further reduce the size and weight of the parts and optimize the hydraulic control.

(3) According to the configuration of claim 3, a space-saving and highly reliable retarder device can be obtained.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of the present invention.

FIG. 2 is a plan view for explaining the operation of the switching pin of FIG.

FIG. 3 is a side view of FIG.

FIG. 4 is a side view for explaining the operation of the rocker arm of FIG.

FIG. 5 is a side view for explaining another operation of the rocker arm of FIG.

FIG. 6 is a valve lift diagram for explaining the operation of the present invention.

FIG. 7 is a profile view of the cam of FIG.

FIG. 8 is a cycle diagram of the engine for explaining the operation of the present invention.

FIG. 9 is a plan view showing a conventional variable valve timing lift device.

FIG. 10 is a side view showing a conventional retarder device.

[Explanation of symbols]

 21 First Cam 22 Exhaust Valve 23 First Rocker Arm 25 Second Cam 26 Second Rocker Arm 27 Switching Pin 36 Intake Valve 40 Cam Bracket (Fixed System) 44 Control Hydraulic Chamber 46 Rocker Arm Lubrication Circuit 47 Control Hydraulic Circuit 56 Load Receiving pin 62 Load transmitting pin 71 Lost motion mechanism

Claims (3)

[Claims] 1. A variable valve timing lift device for an engine, wherein a plurality of rocker arms swinging by respective cams are connected / disconnected by forward / backward movements of a switching pin to control switching of an intake valve or an exhaust valve. A variable valve timing / lift device for an engine, characterized in that a control hydraulic chamber for appropriately advancing and retreating is divided into a fixed system separated from the rocker arm and is connected to a control hydraulic circuit separate from a rocker arm lubrication circuit. 2. A first rocker arm which swings by a first cam to appropriately lift an intake valve or an exhaust valve and a second rocker arm which swings by a second cam are connected by a forward / backward movement of a switching pin. -In the variable valve timing lift device of the engine to be released, a control hydraulic chamber that is partitioned into a fixed system that is isolated from the rocker arm and that is connected to a control hydraulic circuit that is separate from the rocker arm lubrication circuit and that accommodates the switching pin in a retractable manner. A load receiving pin provided on the first rocker arm and urged to the second rocker arm side; and a push pin that pushes the load receiving pin by advancing the switching pin provided on the second rocker arm. Variable valve timing of an engine, comprising: a load transmission pin that engages with the rocker arm of・ Lift device. 3. A first rocker arm that swings by a first cam having a predetermined exhaust stroke profile to appropriately lift the exhaust valve, and a compression pressure release profile that is provided in parallel with the first rocker arm. The second rocker arm that swings by the second cam, the switching pin that moves forward and backward by the supply of control hydraulic pressure, and the switching pin that is partitioned by the bracket of the cam and is connected to a control hydraulic circuit separate from the rocker arm lubrication circuit. And a control hydraulic chamber that houses the
A load receiving pin provided on the first rocker arm and biased toward the second rocker arm and a first rocker arm that pushes the load receiving pin by advancing the switching pin provided on the second rocker arm. And a load transmission pin for engaging these rocker arms integrally with each other, and a retarder device for an engine.