JPH0673301U - Engine valve actuation - Google Patents

Abstract

(57) [Summary] [Purpose] A valve lift characteristic of at least 3 in the low, medium and high rpm range
In an engine valve actuating device for switching to a stage, high-precision machining of a linkage switching portion is not required, thereby reducing cost and downsizing. [Structure] Low speed cams 21 and 21 each having one end linked to a valve V
Rocker arm 1 driven by, and medium and high speed cams 22,
First and second free cam followers 2 driven by 23
A and 2B, the first and second free cam followers 2A and 2B have hydraulically actuated plungers 31A and 31A, respectively.
31B includes the first and second lost motion mechanisms 25.
The first and second positions for engaging the A and 25B functions and the second position for engaging the first and second free cam followers 2A and 2B and stopping the function of the lost motion mechanism are oscillated. The second lever members 7A and 7B are supported and provided on the rocker arm 1.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an engine valve actuating device, and more particularly to an engine valve actuating device capable of switching valve lift characteristics in at least three stages between low engine speed and high engine speed.

[0002]

[Prior art]

 Conventionally, in order to achieve both high torque characteristics at low and medium speed operation and improved output at high speed operation, the lift characteristics of the intake valve or exhaust valve are made different according to the operating state, which results in intake and exhaust It is known to control the timing or the amount of intake and exhaust. For example, in the one disclosed in Japanese Utility Model Laid-Open No. 63-82009, the valve lift characteristic is switched to the third stage.

This type includes a cam that rotates in synchronization with a crankshaft, a pair of valves installed in an intake hole or an exhaust hole of a combustion chamber, and a rocker arm as a transmission member that transmits the lift of the cam to the valve. A valve mechanism for an internal combustion engine having, wherein the cam is composed of two or more cams each having a different shape corresponding to a rotational speed range of the engine, and the rocker arms are arranged adjacent to each other by 4 or more. And a switching means for selecting connection or non-connection between the adjacent rocker arms.

As the switching means, four adjacent rocker arms are provided with fitting holes in a direction parallel to the rocker shaft at rocking portions separated from the rocker shaft by a predetermined distance. The plunger is fitted in this fitting hole.When the plunger is fitted in the fitting hole or pulled out from the fitting hole in response to the hydraulic pressure, adjacent rocker arms are connected or the connection is released. It is supposed to be.

[0005]

[Problems to be solved by the device]

 However, in such a conventional one, when the plurality of plungers fitted in the respective fitting holes are coaxially aligned with each other, the plunger that receives hydraulic pressure pushes the mating plunger while pushing the mating plunger. Since it is configured to fit into the mating hole of the mating member, it is required that the machining accuracy of the mating hole of the plunger and each rocker arm be extremely high, which is one of the causes of cost increase. This is because if the machining accuracy is lowered and both clearances are allowed to be large, the operating hydraulic pressure is not guaranteed first, and further, wear and noise are generated due to the one-sided contact between the fitting hole and the plunger, and the force is accurate. This is not preferable because it is not transmitted to the user.

Further, since the four rocker arms are adjacent to each other, it is unavoidable that the arm rows are enlarged, the mountability on the engine is not good, and the moment of inertia of the entire valve train increases. It was

The object of the present invention is to solve the above-mentioned problems of the related art, to improve the transmission rigidity, to reduce the cost without the need for high-precision machining, and to make the valve operating device of an engine compact and capable of reducing the moment of inertia. To provide.

[0008]

[Means for Solving the Problems]

 In order to achieve such an object, the present invention has a cam follower portion that is swingably supported by a rocker shaft so that its tip is linked to a plurality of intake valves or exhaust valves and that abuts on a first cam at both ends. A rocker arm, a plurality of free cam followers that are swingably supported at the center of the rocker arm and are driven by a plurality of cams, a plurality of lost motion mechanisms provided for the plurality of free cam followers, and the rocker arm. A plurality of linking members supported and swingable between a first position that activates the functions of the plurality of lost motion mechanisms and a second position that stops the functions of the lost motion mechanisms; and a plurality of linking members of the plurality of linking members. A plurality of linkage switching means for respectively switching to the first position and the second position.

[0009]

[Action]

 According to the present invention, each linkage member supported by the rocker arm is moved to the first position for exhibiting the lost motion function by each linkage switching means so that the rocker arm and the plurality of free cam followers are connected to each other. The rocker arm and the free cam follower are respectively coupled by being released and moving to the second position that stops the function of the lost motion mechanism. Thus, the lift characteristic of the first cam is obtained when the rocker arm and the multiple free cam followers are disconnected, and the lift characteristic of one of the multiple cams is obtained when the rocker arm and the multiple free cam followers are connected. As a result, at least three lift characteristics can be obtained.

[0010]

【Example】

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIGS. 1 to 4 show an engine equipped with two valves V (both intake valves and exhaust valves, which are shown as intake valves) having the same function for one cylinder. An example when the present invention is applied is shown.

Explaining this, each cylinder is provided with a single rocker arm 1 corresponding to two intake valves V. The base end of the rocker arm 1 is swingably supported by the cylinder head via a hollow main rocker shaft 3 common to each cylinder, and the bifurcated ends of the rocker arm 1 abut the stem top of the intake valve V.

Then, as shown in FIG. 3, a tip 1C made of a wear resistant material is provided at the tip end portion of the rocker arm 1 that abuts on the stem top of the intake valve V. By doing so, the entire rocker arm 1 can be made of a lightweight member such as aluminum, and the equivalent inertial mass can be reduced and processing can be facilitated.

Further, the rocker arm 1 is formed in a substantially bifurcated shape in a plan view, and the rocker arm 1 is provided with first and second free cam followers 2A and 2B substantially above the center thereof. The base ends of the first and second free cam followers 2A and 2B are rotatably supported by the rocker arm 1 via a sub-rocker shaft 16. The sub-rocker shaft 16 is rotatably fitted in the holes 17A, 17B formed in the free cam followers 2A, 2B, and is press-fitted and supported in the holes of the support walls 18, 18 and 19 formed in the rocker arm 1.

The free cam followers 2A and 2B do not have a portion that comes into contact with the intake valve V, and the tips of the free cam followers 2A and 2B are in sliding contact with the middle speed cam 22 as the second cam and the high speed cam 23 as the third cam, respectively. The cam follower portions 2AA and 2BA are formed so as to project in an arc shape.

2, both ends of the rocker arm 1 are provided with rollers 11, 11 as a cam follower portion with which the low speed cams 21, 21 as a first cam abut. The rollers 11, 11 are rotatably supported by a bearing shaft 12 inserted in a through hole 13 provided in the rocker arm 1 via a needle bearing 14.

In the rocker arm 1, a space 1A for accommodating the tip portions of the free cam followers 2A and 2B and a lever member described later is formed by cutting until the rocker shaft 3 is exposed. The distance from the valve shaft of the valve V can be shortened, that is, the rocker arm 1 can be made compact.

Further, columnar recesses 27A and 27B for accommodating the first and second lost motion mechanisms 25A and 25B are formed below the first and second free cam followers 2A and 2B, respectively. ing. The base ends of the coiled lost motion springs 26A and 26B are supported by the bottom surfaces of the recesses 27A and 27B, respectively, and the tips thereof are slidably fitted in the recesses 27A and 27B, and have a bottomed cylindrical sprinker retainer. 29A and 29B are energized. The heads of the spring retainers 29A and 29B are in contact with the rocker shaft 3 in the above-described exposed state. Although only the second lost motion mechanism 25B is shown in FIG. 3, both have the same configuration. Therefore, the first lost motion mechanism 25A is omitted in the drawing together with its components 26A to 29A.

Further, the first and second free cam followers 2A, 2B described above are provided with stepped portions 2AB, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B, 2B. 2BB and inclined portions 2AC and 2BC connected to this are formed respectively. Further, on the lower side of the rocker arm 1, first and second lever members 7A and 7B are provided as linking members which are swingably supported by a pin 6 on the side of the rocker shaft 3.

The lower ends of the first and second lever members 7 A and 7 B respectively have one ends of the first and second return springs 8 A and 8 B respectively wound around both ends of the pin 6. The return springs 8A and 8B are locked and are urged by the return springs 8A and 8B in a direction to release the engagement with the first and second free cam followers 2A and 2B.

On the other hand, at the lower ends of the first and second lever members 7A and 7B, the first and second actuating plungers of the first and second hydraulic drive units 30A and 30B provided on the rocker arm 1 are provided. 31A and 31B are in contact with each other. That is, the first and second actuating plungers 31A and 31B described above are slidably fitted in the rocker arm 1 in the direction orthogonal to the axis of the main rocker shaft 3 described above, respectively. Second recesses 32A and 32B are formed respectively, and first and second hydraulic chambers 34A are provided between the first and second actuating plungers 31A and 31B and the first and second recesses 32A and 32B. 34B respectively.

A tube 41 having a crescent-shaped cross section is press-fitted into the hollow portion of the main rocker shaft 3, and first and second oil galleries 42A and 42B are formed in the axial direction.

In the rocker arm 1, a central portion communicates with the first hydraulic chamber 34 A, one end is closed by a blind plug 45, and the other end is formed with a first through hole 43 A penetrating a bearing surface for the main rocker shaft 3. Has been done. The first through hole 43A communicates with the first oil gallery 42A through a through hole 44A that is opened at the same time in the main rocker shaft 3 and the tube 41. Further, the rocker arm 1 is formed with a second through hole 43B having one end opened to the second hydraulic chamber 34B and the other end penetrating a bearing surface for the main rocker shaft 3.

The second oil gallery 42B communicates with the through hole 43B of the rocker arm 1 through the through hole 44B formed in the main rocker shaft 3. Thus, the first and second lever members 7A and 7B respectively have the first and second return springs 8A and 8B, which are respectively operated by the operating oil pressures guided to the first and second hydraulic chambers 34A and 34B. First and second link switching means are configured.

The discharge hydraulic pressure of the engine oil pump 52 is guided to the first and second oil gallery 42A, 42B via the first and second switching valves 51A, 51B shown in FIG. 5 during a predetermined operation. . The control unit 53, which electronically controls the operation of the switching valves 51A and 51B, inputs an engine speed signal, a cooling water temperature signal, a lubricating oil temperature signal, a supercharging intake supercharging pressure signal, a throttle valve opening signal, and the like. Then, based on these detected values, it is possible to smoothly switch the lift characteristics by the first cam 21 to the third cam 23, which will be described later, while suppressing the rapid fluctuation of the engine torque.

The low speed cams 21 and 21 and the medium speed cam 22 and the high speed cam 23 between them are integrally formed on a common cam shaft, respectively, and are required from low engine speed to high engine speed. Different shapes (including similar shapes with different sizes) are formed to satisfy the valve lift characteristics. That is, the high-speed cam 23 has a profile larger than the medium-speed cam 22 and the medium-speed cam 22 has a profile larger than at least one of the valve lift amount and the valve opening period as compared with the low-speed cam 21. Here, the valve lift amount and the valve opening period are both increased.

In the present embodiment having the above-described configuration, during low speed operation of the engine, the rocker arm 1 swings according to the profile of the low speed cam 21 to open / close each intake valve V. At this time, the first free cam follower 2A is swung by the medium speed cam 22 and the second free cam follower 2B is swung by the high speed cam 23, respectively, but the lever members 7A, 7B are biased by the return springs 8A, 8B. Are in the positions shown in FIGS. 4 and 3, respectively, and are in the linked state in the first position where the first and second lost motion mechanisms 25A and 25B perform their respective functions. Therefore, even if there is an input from the first and second free cam followers 2A and 2B, only the lost motion springs 26A and 26B are bent and the movement of the rocker arm 1 is not hindered.

Next, at the time of medium speed operation of the engine, the first switching valve 51A is operated by a command from the control unit 53, and the operating hydraulic pressure is passed through the first oil gallery 42A and the passages 44A, 43A to the first hydraulic chamber 34A. Be led to. Then, the first actuating plunger 31A swings the first lever member 7A against the first return spring 8A and engages with the first free cam follower 2A in the same manner as in the case described later, thereby engaging the rocker arm 1 and the first rocker arm 1A. The free cam followers 2A are integrally connected.

Further, when the second switching valve 51B operates during high-speed operation of the engine and the operating oil pressure is guided to the second oil pressure chamber 34B via the second oil gallery 42B and the passages 44B and 43B, the second operation plunger is operated. 31B swings the second lever member 7B against the second return spring 8B to bring it to the second position shown by the broken line in FIG. In this state, the end portion of the second lever member 7B engages with the stepped portion 2BB of the second free cam follower 2B, so that the rocker arm 1 and the second free cam follower 2B are connected to each other to form a main rocker shaft. It will swing around 3.

Here, the high-speed cam 23 is formed such that the medium-speed cam 22 and the medium-speed cam 22 are both larger in valve opening and valve lift than the low-speed cam 21. Therefore, when swinging together with the first free cam follower 2A, the roller 11 of the rocker arm 1 rises from the low speed cam 21 and follows the profile of the medium speed cam 22, and also the second free cam follower 2B. During the integrated swing, both the first free cam follower 2A and the roller 11 of the rocker arm 1 float up from the middle and low speed cams 22 and 21, and each intake valve V is driven to open and close according to the profile of the high speed cam 23, Both the opening degree and the valve lift amount increase. At this high speed, the first switching valve 51A may be located at any position.

On the other hand, when the engine moves from the high / medium speed range to the low speed range again, the hydraulic pressure introduced to the hydraulic chambers 34A, 34B is reduced by the operation of the switching valves 51A, 51B, and the elastic return of the return springs 8A, 8B is restored. The force moves the lever members 7A, 7B and the actuating plungers 31A, 31B to their original positions, and the locker arm 1 is released from the restraint.

As a result, the torque characteristic based on the profile of the low speed cam 21 and the torque characteristic based on the profile of the medium and high speed cams 22 and 23 are combined, and the torque can be increased from the low rotation range to the high rotation range. .

By the way, in the above-mentioned embodiment, even if the hydraulic pressure is not sufficiently generated and the lever members 7A and 7B are not sufficiently moved from the first position to the second position. Since the lever members 7A and 7B swing while the ends of the lever members 7A and 7B slide on the inclined portions 2AC and 2BC of the free cam followers 2A and 2B, the collision between the roller 11 and the low speed cam 21 is reduced. Therefore, the generation of abnormal noise is reduced.

Further, in this embodiment, as shown in FIG. 1, the intermediate point G between the two intake valves V and the points E _F and E _R at which both ends of the rocker arm 1 intersect the central axis of the rocker shaft are connected. Since the load points C _F and C _R of the first and second free cam followers 2A and 2B are arranged inside the curved line segments, the rocker arm 1 can be prevented from collapsing and high-speed operation is possible.

[0035]

[Effect of device]

 As is clear from the above description, according to the present invention, it is not necessary to form a fitting hole and the machining accuracy thereof may be lower than that of a conventional one in which a plunger is inserted into a fitting hole and connected. The cost can be reduced. Further, the free cam follower, the linking member, etc. can be arranged close to the center of the rocker shaft, and the equivalent inertial mass can be reduced. Furthermore, since a plurality of free cam followers are supported by the arm with a one-piece structure, it is more compact in the width direction compared to the conventional model, and is easy to mount on the engine. Further, since the rigidity can be maintained high, the lift force can be accurately transmitted.

[0036]

[Brief description of drawings]

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

FIG. 2 is a vertical sectional view taken along the line II-II in FIG.

3 is a cross-sectional view taken along the line III-III in FIG. 2, showing a state where the rocker arm and the second free cam follower are disconnected from each other.

FIG. 4 is a partial cross-sectional view taken along the line IV-IV in FIG.

FIG. 5 is a hydraulic circuit diagram of an embodiment of the present invention.

[Explanation of symbols]

 1 Rocker Arm 2A, 2B Free Cam Follower 3 Main Rocker Shaft 7A, 7B Lever Member (Linking Member) 11 Roller 16 Sub Rocker Shaft 25A, 25B Lost Motion Mechanism 31A, 31B Operation Plunger

Claims (2)

[Scope of utility model registration request] 1. A rocker arm having a cam follower portion, which is rockably supported by a rocker shaft so that its tip is linked to a plurality of intake valves or exhaust valves, and abuts against a first cam at both ends, and a central portion of the rocker arm. A plurality of free cam followers that are swingably supported by a plurality of cams, respectively, a plurality of lost motion mechanisms provided for the plurality of free cam followers, and a plurality of lost motion mechanisms supported by the rocker arm. A plurality of linking members swingable between a first position that exerts the function of the above and a second position that stops the function of the lost motion mechanism, and a plurality of linking members that move the plurality of linking members to the first position and the second position. A valve operating device for an engine, comprising: a plurality of linkage switching means for performing switching, respectively. 2. The load points of the plurality of free cam followers are inside a line segment that connects the intermediate points of the plurality of intake valves or the exhaust valves and the points where both ends of the rocker arm intersect with the central axis of the rocker shaft. The valve actuating device for an engine according to claim 1, wherein