WO2021131191A1

WO2021131191A1 - Variable valve mechanism

Info

Publication number: WO2021131191A1
Application number: PCT/JP2020/035966
Authority: WO
Inventors: 寿恭佐藤; 悟高雄; 剛松浦; 祥典中尾; 健介木本
Original assignee: 川崎重工業株式会社
Priority date: 2019-12-25
Filing date: 2020-09-24
Publication date: 2021-07-01
Also published as: JP2021102947A

Abstract

This variable valve mechanism is for changing the lift characteristics of a valve which opens/closes an intake port or an exhaust port of an engine, wherein said mechanism comprises: a cam which rotates in conjunction with rotation of a crankshaft of the engine; a swing arm which, when pressed by the rotating cam, swings about a swing axis that is parallel to the rotational axis of the cam, and actuates the valve in accordance with the swing angle; a swing support which swingably supports the swing arm about the swing axis; and a movement device which linearly moves the swing support together with the swing arm in a direction orthogonal to the valve axial line. The swing arm has a flat surface extending along the longitudinal direction of the swing arm, and the cam contacts the flat surface during a single rotation.

Description

Variable valve mechanism

The present invention relates to a variable valve mechanism of an engine.

Conventionally, a variable valve mechanism that changes the lift characteristics of a valve that opens and closes an engine intake or exhaust port, that is, the valve opening / closing timing and opening / closing amount, etc. has been proposed.

For example, Patent Document 1 discloses a variable valve mechanism of an internal combustion engine including a control cam for moving a swing arm (rocker arm) provided between a drive cam and a valve stem. A control cam is rotatably arranged on the base end side of the swing arm, and a fulcrum portion of the base end of the swing arm is rotatably attached to a portion away from the rotation center of the control cam. The tip of the swing arm is in contact with a cap provided at the upper end of the valve stem. The control cam is rotated by a predetermined angle by the driving means. By rotating the control cam by a drive means by a predetermined angle, the position of the swing arm with respect to the drive cam changes, and as a result, the contact position between the swing arm and the drive cam changes, and the valve opening / closing timing and opening / closing amount change. To do.

Jikkenhei 3-5906 Gazette

In the above-mentioned variable valve mechanism, when the control cam is rotated to change the lift characteristics of the valve, the fulcrum portion, which is the swing center of the swing arm, rotates and moves around the rotation axis of the control cam. In such a configuration in which the swing center of the swing arm rotates, the contact surface pressure between the drive cam and the swing arm and the lift characteristics of the valve control the distance between the rotation center of the control cam and the fulcrum. It depends on many parameters such as the angle at which the cam is rotated, the positions of the swing arm and the control cam with respect to the rotation center of the drive cam, and the shape of the contact surface of the swing arm with the drive cam. Therefore, at the design stage, it is very important to study how to design the valve so that the desired valve lift characteristics can be changed while keeping the contact surface pressure between the drive cam and the swing arm within an allowable range. It takes time.

Therefore, an object of the present invention is to provide a variable valve mechanism for an engine that can reduce the labor required for design.

In order to solve the above problems, the variable valve mechanism according to one aspect of the present invention is a variable valve mechanism that changes the lift characteristics of a valve that opens and closes an intake or exhaust port of an engine. A cam that rotates in conjunction with the rotation of the crank shaft of the engine and a cam that is pressed by the rotating cam to swing around a swing shaft parallel to the rotation shaft of the cam, and the swing angle according to the swing angle. A swing arm that operates the valve, a swing support that swingably supports the swing arm around the swing shaft, and a swing support together with the swing arm in a direction orthogonal to the valve axis. The swing arm has a flat surface extending along the longitudinal direction of the swing arm, and the cam has the flat surface during one rotation. Contact with.

According to the above configuration, the moving device linearly moves the swing axis of the swing arm in the direction orthogonal to the valve axis. Therefore, it is only necessary to consider the simple linear movement of the swing arm, and it is possible to reduce the design parameters related to the position and shape of each component of the variable valve mechanism. Therefore, it becomes easy to design a valve capable of changing the lift characteristics of a desired valve while keeping the contact surface pressure between the cam and the swing arm within an allowable range, and the labor required for the design can be reduced.

According to the present invention, it is possible to provide a variable valve mechanism of an engine that can reduce the labor required for design.

It is schematic cross-sectional view which showed the variable valve mechanism which concerns on 1st Embodiment and its periphery. It is an enlarged view of the swing arm of the variable valve mechanism which concerns on 1st Embodiment and the vicinity thereof. It is an enlarged cross-sectional view of the surface of the swing arm facing a cam. It is a graph which shows the relationship between a cam rotation angle and a valve lift amount. It is an enlarged view of the swing arm of the variable valve mechanism which concerns on 2nd Embodiment and the vicinity thereof. It is an enlarged view of the swing arm of the variable valve mechanism which concerns on 3rd Embodiment and the vicinity thereof. It is an enlarged view of the swing arm of the variable valve mechanism which concerns on 4th Embodiment and the vicinity thereof. It is an enlarged view of the swing arm of the variable valve mechanism which concerns on 5th Embodiment and the vicinity thereof. It is an enlarged view of the swing arm of the variable valve mechanism which concerns on 6th Embodiment and the vicinity thereof. It is an enlarged view of the swing arm of the variable valve mechanism which concerns on 7th Embodiment and the vicinity thereof. It is an enlarged view of the swing arm of the variable valve mechanism which concerns on 8th Embodiment and the vicinity thereof. It is an enlarged view of the swing arm of the variable valve mechanism which concerns on 9th Embodiment and the vicinity thereof. It is an enlarged view of the swing arm of the variable valve mechanism which concerns on the tenth embodiment, and the vicinity thereof. It is the schematic sectional drawing which showed the variable valve mechanism which concerns on eleventh embodiment and its periphery.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In each figure, the same or similar configurations are designated by the same reference numerals, and duplicate description will be omitted.

(First Embodiment)
FIG. 1 is a schematic cross-sectional view showing the variable valve mechanism 20A on the exhaust side of the engine and its periphery according to the first embodiment. First, the configuration of the engine in which the variable valve mechanism 20A according to the first embodiment is adopted will be described.

The engine described in this embodiment is a double overhead camshaft type (DOHC type) engine. The cylinder head 2 of the engine is provided with an intake port (not shown) and an exhaust port 4 connected to the combustion chamber 3. Further, the cylinder head 2 is provided with an intake valve (not shown) and an exhaust valve 10 for opening / closing the combustion chamber 3, respectively, for the intake port and the exhaust port 4. The engine includes a variable valve mechanism on the intake side and a variable valve mechanism 20A on the exhaust side that open and close the intake valve and the exhaust valve 10.

Such an engine is installed in, for example, a motorcycle. In the following, for convenience of explanation, the concept of the direction used in the embodiment shall be generally in line with the passenger of the motorcycle equipped with the engine. Specifically, the upper side of the paper in FIG. 1 is the “upper side” of the engine. The lower side of the paper in FIG. 1 is defined as the "lower side" of the engine, the right side of the paper in FIG. 1 is defined as the "front side" of the engine, and the left side of the paper in FIG. 1 is defined as the "rear side" of the engine. However, the back side of the paper in FIG. 1 is defined as the "left side" of the engine, and the front side of the paper in FIG. 1 is defined as the "right side" of the engine. It should be noted that the downward direction in the direction concept of the embodiment defined in this way does not have to coincide with the vertical downward direction, the downward direction may be inclined with respect to the vertical downward direction, or the vertical upward direction may be used. They may match. For example, the valve axis C2 described later may be inclined with respect to the vertical direction.

Further, since the valve and the variable valve mechanism have substantially the same structure on the intake side and the exhaust side, the exhaust side will be described as a representative below. Further, in the following, the "exhaust valve 10" and the "exhaust port 4" will be simply referred to as "valve 10" and "port 4", respectively.

The valve 10 includes a valve body 11 having a flange portion 11a for opening and closing the port 4 and a stem portion 11b extending upward from the flange portion 11a. A spring retainer 13 is attached to the upper end of the stem portion 11b via a cotter (not shown). A spring seat 15 is attached to the upper surface of the cylinder head 2. A valve spring 17 is interposed between the spring seat 15 and the spring retainer 13. The valve body 11 is urged upward by the valve spring 17. As a result, the flange portion 11a comes into contact with the peripheral edge portion (valve seat) 4a of the port 4, and the port 4 is closed.

A tappet 18 is attached to the upper end portion of the stem portion 11b (base end portion; the end portion opposite to the end portion provided with the flange portion 11a) via a shim (not shown). When the variable valve mechanism 20A pushes down the tappet 18, the flange portion 11a is separated from the valve seat 4a and the port 4 is opened.

The variable valve mechanism 20A changes the lift characteristics of the valve 10. Specifically, the variable valve mechanism 20A changes the maximum lift amount, opening / closing timing, and opening time of the valve 10. The variable valve mechanism 20A includes a cam 21, a swing arm 31, a swing support 41, and a moving device 43.

The cam 21 rotates in conjunction with the rotation of the engine crankshaft (not shown). Specifically, a cam shaft 22 (rotation shaft) to which the cam 21 is fixed is arranged above the valve 10. The cam shaft 22 extends horizontally in the left-right direction. The cam shaft 22 is connected to the crank shaft via a rotation transmission mechanism (not shown) such as a chain, and rotates in conjunction with the crank shaft. In this way, the cam 21 fixed to the cam shaft 22 rotates together with the cam shaft 22.

In the present embodiment, the cam shaft 22 is orthogonal to the axis C2 of the valve 10 (that is, a straight line extending the center line of the stem portion 11b). More specifically, the axis C1 of the camshaft 22 is located on the axis C2 of the valve 10 when viewed from the direction along the axis C1. However, the axis C1 of the cam shaft 22 does not have to be located on the axis C2 of the valve 10 when viewed from the direction along the axis C1, and is located forward or rearward of the axis C2 of the valve 10. You may.

The outer peripheral surface of the cam 21 around the axis C1 is a perfect circular base circle 21a at a certain distance from the axis C1 of the cam shaft 22 and a cam ridge portion that bulges outward in the radial direction from the base circle 21a. 21b is included.

The swing arm 31 is provided between the cam 21 and the valve 10. The swing arm 31 extends in a direction orthogonal to a direction parallel to the axis C1 of the cam shaft 22 (that is, a direction perpendicular to the axis C1). Further, when the base circular portion 21a of the cam 21 faces the upper surface 32 of the swing arm 31, that is, when the swing arm 31 is not pressed by the cam 21, the swing arm 31 is aligned with the axis C2 of the valve 10. It extends in the orthogonal direction. That is, the swing arm 31 extends in the front-rear direction. However, the swing arm 31 does not have to extend in the direction orthogonal to the axis C2 of the valve 10 when the base circular portion 21a of the cam 21 faces the upper surface 32 of the swing arm 31, and the swing arm 31 does not have to extend in the direction orthogonal to the axis C2 of the valve 10. On the other hand, it may extend in a direction that intersects diagonally.

The outer peripheral surface (at least the cam ridge 21b) of the cam 21 comes into contact with the upper surface 32 of the swing arm 31, and the upper surface of the tappet 18 (hereinafter referred to as “tappet surface”) 18a touches the lower surface 33 of the swing arm 31. Contact. The tappet surface 18a is a plane orthogonal to the valve axis C2. The shapes of the upper surface 32 and the lower surface 33 of the swing arm 31 will be described in detail later. By being pressed by the rotating cam 21, the swing arm 31 swings so as to change the extending direction of the swing arm 31 with respect to the valve axis C2 when viewed from the direction along the axis C1.

The swing support 41 is a member that swingably supports the swing arm 31 around a swing shaft 42 parallel to the cam shaft 22 (axis C1) of the cam 21. Specifically, the swing support 41 is located in front of the valve axis C2 when viewed from the direction along the axis C1. Then, one end portion (in this example, the front end portion) of the swing arm 31 in the extending direction is swingably connected to the swing support 41 via the swing shaft 42. The swing shaft 42 may be integrally formed with the swing arm 31 or the swing support 41. The swing arm 31 is pressed by the rotating cam 21 and swings around the swing shaft 42 (axis C3). Then, the valve 10 operates according to the swing angle of the swing arm 31.

The moving device 43 linearly moves the swing support 41 together with the swing arm 31 in a direction orthogonal to the valve axis C2 and orthogonal to a direction parallel to the axis C1 of the cam shaft 22. That is, the moving device 43 positions the swing support 41 in the front-rear direction, and thus positions the swing shaft 42.

The moving device 43 includes a fixing member 43a provided at a position fixed to the axis C1 of the cam shaft 22, and a movable portion 43b that moves (displaces) linearly with respect to the fixing member 43a. The moving device 43 linearly moves the movable portion 43b in a direction orthogonal to the valve axis C2 (in this example, the front-rear direction) with respect to the fixing member 43a. The fixing member 43a may be fixedly arranged with respect to the axis C1 of the cam shaft 22. In other words, the relative positional relationship between the fixing member 43a and the axis C1 of the cam shaft 22 may be fixed. The fixing member 43a is fixed to, for example, one of a cylinder head 2, a cylinder head cover covering the upper portion of the cylinder head 2, and a casing covering the cylinder head 2. A swing support 41 is attached to the movable portion 43b. For example, the movable portion 43b is formed in a rod shape extending in the front-rear direction, the front end portion of the rod is supported by the fixing member 43a, and the swing support 41 is fixed to the rear end portion of the rod.

For example, the moving device 43 is a hydraulic linear actuator using a hydraulic control valve and a hydraulic cylinder. However, the moving device 43 does not have to be a hydraulic type, and may have any configuration of, for example, a mechanical type, a motor type, or an electromagnet type. Further, the moving device 43 may be configured to include a linear motion mechanism using a link mechanism, a worm gear, a rack and pinion, or the like.

When the moving device 43 changes the position of the swing support 41, the lift characteristic of the valve 10 operated by the variable valve mechanism 20A changes. For example, when the position of the swing support 41 is changed, at least the distance from the contact point between the cam 21 and the swing arm 31 to the swing shaft 42 is changed. As a result, the range of the swing angle of the swing arm 31 changes, and the maximum lift amount of the valve 10 (that is, the maximum value of the distance from the valve seat 4a to the flange portion 11a when the cam 21 makes one rotation) changes. To do.

For example, when the moving device 43 changes the position of the swing support 41 from a predetermined distal region to a proximal region closer to the cam 21 than the distal region, the maximum lift amount of the valve 10 increases. In addition, in FIG. 1 and each figure shown below, the rocking arm 31 and the rocking support 41 when the rocking support 41 is in the distal region are shown by solid lines, and when the rocking support 41 is in the proximal region. The swing arm 31 and the swing support 41 are indicated by a two-dot chain line.

Further, in the present embodiment, when the moving device 43 changes the position of the swing support 41, not only the maximum lift amount of the valve 10 changes, but also the opening / closing timing and opening time of the valve 10 change. This will be described in detail with reference to FIG.

FIG. 2 is an enlarged view of the swing arm 31 of the variable valve mechanism 20A and its vicinity. The upper surface 32 of the swing arm 31 includes a flat surface 32a and an inclined surface 32b. The flat surface 32a is a plane extending along the longitudinal direction of the swing arm 31. That is, when the base circular portion 21a of the cam 21 faces the upper surface 32 of the swing arm 31, the flat surface 32a extends in a direction orthogonal to the axis C1 of the cam shaft 22 and orthogonal to the axis C2 of the valve 10. There is. The cam 21 comes into contact with the flat surface 32a while the cam 21 makes one rotation.

The inclined surface 32b is inclined with respect to the flat surface 32a. The flat surface 32a and the inclined surface 32b are formed adjacent to each other in the front-rear direction. In the present embodiment, the inclined surface 32b is located in front of the flat surface 32a. In other words, the inclined surface 32b is arranged at a position closer to the swing shaft 42 than the flat surface 32a. One side end portion (rear end portion in this example) of the inclined surface 32b in the longitudinal direction of the swing arm 31 is one side end portion (front end portion in this example) of the flat surface 32a in the longitudinal direction of the swing arm 31. )It is connected to the.

In the present embodiment, the inclined surface 32b is a flat surface 32a so that the upper surface 32 of the swing arm 31 (the surface of the swing arm facing the cam 21) is formed in a concave shape by the inclined surface 32b and the flat surface 32a. It is inclined with respect to. In other words, the inclined surface 32b is inclined toward the cam 21 side (upper side) toward the direction away from the flat surface 32a.

FIG. 3 is an enlarged cross-sectional view of a part of the upper surface 32 of the swing arm 31. The inclined surface 32b has a curved surface portion 32b ₁ _{connected to the flat surface 32a and a flat surface portion 32b 2} connected to the end portion _{of the curved surface portion 32b 1} on the opposite side of the flat surface 32a. The curved surface portion 32b ₁ is curved so that the inclination with respect to the flat surface 32a when viewed from the direction along the axis C1 gradually increases as the distance from the flat surface 32a increases. The curved surface portion 32b ₁ is smoothly connected to the flat surface portion 32b _2. In other words, the inclination of the front end portion of _{the curved surface portion 32b 1} and the inclination of the rear end portion of the _{flat surface portion 32b 2 when} viewed from the direction along the axis C1 are the same. The inclined surface 32b may _{not have both the curved surface portion 32b 1} and the flat surface portion 32b _2. For example, the inclined surface 32b may have only _one of the curved surface portion 32b 1 and the flat surface portion 32b _2. Good.

Returning to FIG. 2, the swing arm 31 has a bulging portion that bulges toward the tappet 18. In other words, the lower surface 33 of the swing arm 31 includes a bulging surface 33a that is convexly curved downward when viewed along the axis C1. The bulging surface 33a comes into contact with the tappet surface 18a. However, when the swing arm 31 does not press the tappet 18, that is, when the base circle portion 21a of the cam 21 is at a position facing the swing arm 31, the bulging surface 33a is not in contact with the tappet surface 18a. May be good.

The moving device 43 moves the swing arm 31 within a range in which the bulging portion (bulging surface 33a) overlaps the tappet surface 18a when viewed along the valve axis C2.

Further, in the present embodiment, the moving device 43 moves the position of the swing support 41 between the distal region and the proximal region. In the present embodiment, in the distal region, when the swing support 41 is in the distal region, the cam 21 contacts the flat surface 32a while the cam 21 makes one rotation, but contacts the inclined surface 32b. It is an area that does not. The proximal region is a region that contacts both the flat surface 32a and the inclined surface 32b during one rotation of the cam 21 when the swing support 41 is in the proximal region. The "distal region" in the present embodiment corresponds to the "first region" in the present invention, and the "proximal region" in the present embodiment corresponds to the "second region" in the present invention.

In the present embodiment, the swing support 41 is closer to the cam 21 when it is in the proximal region than when it is in the distal region. That is, when the swing support 41 is in the proximal region, the swing shaft 42 is closer to the cam 21 and the maximum lift amount of the valve 10 is larger than when the swing support 41 is in the distal region. ..

Next, the operation of the variable valve mechanism 20A will be described with reference to FIGS. 2 and 4. Hereinafter, as shown by an arrow in the cam 21 of FIG. 2, the cam 21 will be described as rotating counterclockwise when viewed to the left along the axis C1. FIG. 4 is a graph in which the rotation angle θ of the cam 21 is on the horizontal axis and the lift amount of the valve 10 (that is, the distance from the valve seat 4a to the flange portion 11a) is on the vertical axis. In FIG. 4, the relationship between the rotation angle θ and the lift amount when the swing support 41 is in the distal region is shown by a solid line, and the relationship between the rotation angle θ and the lift amount when the swing support 41 is in the proximal region is shown by a solid line. It is shown by a two-dot chain line.

First, the operation of the variable valve mechanism 20A when the swing support 41 is in the distal region will be described. When the base circular portion 21a of the cam 21 is in a position facing the swing arm 31, the cam 21 does not push down the swing arm 31 (0 ° ≤ θ <θ _a , θ _b <θ <in FIG. 4). See 360 ° range). Since the swing arm 31 does not push down the valve body 11, the valve 10 is in a state where the port 4 is closed. When the base circle portion 21a of the cam 21 is at a position facing the swing arm 31, the base circle portion 21a does not have to be in contact with the swing arm 31.

When the cam 21 rotates and the cam peak portion 21b of the cam 21 begins to come into contact with the flat surface 32a of the swing arm 31 (θ = θ _{a in} FIG. 4), the cam 21 valves via the swing arm 31. The main body 11 is pushed down, whereby the flange portion 11a is separated from the valve seat 4a to open the port 4. Then, as the cam 21 rotates, the swing arm 31 swings around the swing shaft 42, and the amount of pushing down of the tappet 18 by the swing arm 31, that is, the lift amount of the valve body 11 gradually increases. After that, after the time when the lift amount becomes maximum, the cam ridge portion 21b gradually decreases until the time when the cam ridge portion 21b does not come into contact with the flat surface 32a (θ = θ _{b in FIG. 4).}

When the swing support 41 is in the distal region, the cam 21 contacts the flat surface 32a during one rotation, but not the inclined surface 32b.

When the moving device 43 linearly moves the swing support 41, the position of the swing support 41 is changed from the distal region to the proximal region. When the swing support 41 is moved, the bulge surface 33a slides on the tappet surface 18a as the swing arm 31 moves. Therefore, the contact position with the bulging portion (bulging surface 33a) on the tappet surface 18a is also changed. That is, in the present embodiment, when the position of the swing support 41 is changed, the distance from the contact point between the cam 21 and the swing arm 31 to the swing shaft 42 is changed, but the tappet 18 and the swing arm are changed. The distance from the contact point with 31 to the swing shaft 42 is generally maintained.

Even when the swing support 41 is in the proximal region, the basic operation of opening and closing the valve 10 is the same as when the swing support 41 is in the distal region. That is, when the base circular portion 21a of the cam 21 is in a position facing the swing arm 31, the cam 21 is in a state where the valve 10 is closed at the port 4 (0 ° ≤ θ <θ _a in FIG. 4). See the range θ _c <θ <360 °). Then, when the cam 21 rotates and the cam peak portion 21b of the cam 21 begins to come into contact with the flat surface 32a of the swing arm 31 (θ = θ _{a in} FIG. 4), the cam 21 passes through the swing arm 31. The valve body 11 is pushed down, whereby the flange portion 11a is separated from the valve seat 4a to open the port 4. Then, as the cam 21 rotates, the swing arm 31 swings around the swing shaft 42, and the amount of pushing down of the tappet 18 by the swing arm 31, that is, the lift amount of the valve body 11 gradually increases. ..

However, when the swing support 41 is in the proximal region, the cam ridge 21b of the cam 21 comes into contact with not only the flat surface 32a but also the inclined surface 32b during one rotation. That is, the cam ridge portion 21b comes into contact with the inclined surface 32b after coming into contact with the flat surface 32a. After that, after the time when the lift amount becomes maximum, the cam ridge portion 21b gradually decreases until the time when the cam ridge portion 21b does not come into contact with the inclined surface 32b (θ = θ _{c in FIG. 4).}

In this way, the cam ridge 21b begins to come into contact with the flat surface 32a at the same position regardless of whether the swing support 41 is in the distal region or the proximal region. Therefore, the timing of opening the valve 10 is the same as shown in FIG. 4 before and after the position change of the swing support 41. On the other hand, when the swing support 41 is in the proximal region, the cam ridge 21b comes into contact with the inclined surface 32b, so that the swing arm 31 is in the cam ridge as compared with when the swing support 41 is in the distal region. The time for being pressed by the portion 21b becomes longer. That is, the closing timing of the valve 10 when the swing support 41 is in the proximal region can be delayed as compared with when the swing support 41 is in the distal region.

When the cam 21 rotates clockwise in the figure, as a matter of course, only the opening timing of the valve 10 is variable. That is, the timing of opening the valve 10 when the swing support 41 is in the proximal region is earlier than when the swing support 41 is in the distal region. Further, before and after the position change of the swing support 41, the timing of closing the valve 10 is the same.

As described above, according to the variable valve mechanism 20A according to the present embodiment, the moving device 43 linearly moves the swing shaft 42 of the swing arm 31 in the direction orthogonal to the valve axis C2. Therefore, it is only necessary to consider the simple linear movement of the swing arm 31, and it is possible to reduce the design parameters related to the position and shape of each component of the variable valve mechanism 20A. Therefore, it becomes easy to design a valve 10 that can change the desired lift characteristic of the valve 10 while keeping the contact surface pressure between the cam 21 and the swing arm 31 within an allowable range, and the labor required for the design can be reduced. ..

Further, in the present embodiment, when the swing support 41 is in the distal region, the cam 21 contacts the flat surface 32a during one rotation, does not contact the inclined surface 32b, and the swing support 41 is close to it. When in the position region, the cam 21 comes into contact with both the flat surface 32a and the inclined surface 32b during one revolution. In this way, the closing timing (or opening timing) of the valve 10 can be changed depending on whether the cam 21 contacts the inclined surface 32b or not. Therefore, in the variable valve mechanism 20A of the present embodiment, the open phase (open timing) and the closed phase (close timing) of the valve 10 can be designed separately, and the opening / closing timing (operating angle) of the valve 10 can be designed separately. ) Can be easily changed.

Further, in the present embodiment, the upper surface 32 of the swing arm 31 is formed in a concave shape by the inclined surface 32b and the flat surface 32a, and the curved surface portion 32b _{1 on the} inclined surface 32b increases as the distance from the flat surface 32a increases. It is curved so that the inclination with respect to the flat surface 32a when viewed from the direction along the axis C1 gradually increases. Therefore, for example, as compared with the case where the upper surface 32 of the swing arm 31 is formed in a convex shape, when the cam 21 comes into contact with both the flat surface 32a and the inclined surface 32b during one rotation, the cam 21 is particularly effective. Can reduce the contact surface pressure between the cam 21 and the swing arm 31 when the cam 21 is in contact with the curved surface portion 32b _1.

Further, in the present embodiment, since the swing arm 31 is provided between the cam 21 and the valve 10, an overhead cam type variable valve mechanism having a simple configuration can be realized.

Further, in the present embodiment, the cam shaft 22 which is the rotation axis of the cam 21 is orthogonal to the valve axis C2. Therefore, the portion of the swing arm 31 that is pressed by the cam 21 and the portion of the swing arm 31 that presses the valve 10 can be brought close to each other. Therefore, when the swing arm 31 is pressed by the cam 21, the force that acts on the swing arm 31 to bend the swing arm 31 can be reduced. Therefore, it is possible to design the swing arm 31 with the required strength suppressed.

Further, in the present embodiment, as the swing arm 31 moves, the contact position of the tappet 18 with the bulging portion on the plane is also changed. As a result, while maintaining the distance from the contact position of the swing arm 31 with the tappet 18 to the swing shaft 42 of the swing arm 31, the swing arm 31 is moved from the contact position with the cam 21 of the swing arm 31. The distance to the swing shaft 42 can be changed. Therefore, the lever ratio when the swing arm 31 is moved (that is, the distance from the contact position of the swing arm 31 with the tappet 18 to the swing shaft 42 of the swing arm 31 and the cam 21 of the swing arm 31). The change in the maximum lift amount of the valve 10 with respect to the moving distance of the swing arm 31 can be increased by increasing the change (ratio from the contact position with the swing arm 31 to the swing shaft 42). it can.

(Second Embodiment)
Next, the variable valve mechanism 20B according to the second embodiment will be described with reference to FIG. FIG. 5 is an enlarged view of the swing arm 31 of the variable valve mechanism 20B according to the second embodiment and its vicinity. In the present embodiment as well, as in the first embodiment, the "distal region" and the "proximal region" correspond to the "first region" and the "second region" in the present invention, respectively, and will be described later. The same applies to the 7th to 11th embodiments.

In the present embodiment, the inclined surface 32b is inclined with respect to the flat surface 32a so that the upper surface 32 of the swing arm 31 is formed in a convex shape by the inclined surface 32b and the flat surface 32a. In other words, the inclined surface 32b is inclined toward the tappet 18 side (lower side) toward the direction away from the flat surface 32a. Therefore, in the present embodiment, for example, when the cam 21 rotates counterclockwise in the drawing, the closing timing of the valve 10 when the swing support 41 is in the proximal region is set to the distal region. Instead of delaying, you can accelerate it compared to one time.

In this embodiment as well, the same effect as in the first embodiment can be obtained.

(Third Embodiment)
Next, the variable valve mechanism 20C according to the third embodiment will be described with reference to FIG. FIG. 6 is an enlarged view of the swing arm 31 of the variable valve mechanism 20C according to the third embodiment and its vicinity.

In the present embodiment, unlike the first embodiment, the upper surface 32 of the swing arm 31 includes an inclined surface 32c located behind the flat surface 32a instead of the inclined surface 32b located in front of the flat surface 32a. That is, the inclined surface 32c is arranged at a position farther from the swing shaft 42 than the flat surface 32a. The inclined surface 32c is inclined with respect to the flat surface 32a so that the upper surface 32 of the swing arm 31 is formed in a concave shape by the inclined surface 32c and the flat surface 32a. In other words, the inclined surface 32c is inclined toward the cam 21 side (upper side) toward the direction away from the flat surface 32a.

Also in this embodiment, the moving device 43 moves the position of the swing support 41 between the distal region and the proximal region. In this embodiment, as shown by the solid line in FIG. 6, when the swing support 41 is in the distal region, the cam 21 comes into contact with both the flat surface 32a and the inclined surface 32c during one rotation. Further, as shown by the alternate long and short dash line in FIG. 6, when the swing support 41 is in the proximal region, the cam 21 comes into contact with the flat surface 32a during one rotation of the cam 21, but the inclined surface 32c Does not touch. The "distal region" in the present embodiment corresponds to the "second region" in the present invention, and the "proximal region" in the present embodiment corresponds to the "first region" in the present invention. The same applies to the embodiments.
Therefore, the opening timing of the valve 10 (the closing timing when the cam 21 rotates clockwise in the drawing) can be changed depending on whether the cam 21 contacts the inclined surface 32c or not.

(Fourth Embodiment)
Next, the variable valve mechanism 20D according to the fourth embodiment will be described with reference to FIG. 7. FIG. 7 is an enlarged view of the swing arm 31 of the variable valve mechanism 20D according to the fourth embodiment and its vicinity.

In the present embodiment, unlike the third embodiment, the inclined surface 32c is inclined with respect to the flat surface 32a so that the upper surface 32 of the swing arm 31 is formed to be convex by the inclined surface 32c and the flat surface 32a. doing. In other words, the inclined surface 32c is inclined toward the tappet 18 side (lower side) toward the direction away from the flat surface 32a.

(Fifth Embodiment)
Next, the variable valve mechanism 20E according to the fifth embodiment will be described with reference to FIG. FIG. 8 is an enlarged view of the swing arm 31 of the variable valve mechanism 20E according to the fifth embodiment and its vicinity.

This embodiment is a combination of the first embodiment and the fourth embodiment. Specifically, the upper surface 32 of the swing arm 31 has a flat surface 32a, an inclined surface (first inclined surface) 32b located in front of the flat surface 32a, and an inclined surface (first inclined surface) located behind the flat surface 32a. 2 inclined surface) 32c and the like. The first inclined surface 32b is inclined toward the cam 21 side (upper side) toward the direction away from the flat surface 32a, and the second inclined surface 32c is inclined toward the tappet 18 side (lower side) toward the direction away from the flat surface 32a. ).

When the swing support 41 is in the distal region, the cam 21 contacts both the flat surface 32a and the second inclined surface 32c during one revolution, but not the first inclined surface 32b (FIG. 8). See solid line). When the swing support 41 is in the proximal region, the cam 21 contacts both the flat surface 32a and the first inclined surface 32b during one rotation, but not the second inclined surface 32c (FIG. 8). See two-dot chain line).

In the present embodiment, the "distal region" (or "proximal region") can correspond to both the "first region" and the "second region" in the present invention. When the swing support 41 is in the distal region, it contacts the flat surface 32a during one revolution of the cam 21 and not the first inclined surface 32b, and the swing support 41 is in the proximal region. During one rotation of the cam 21, it comes into contact with both the flat surface 32a and the first inclined surface 32b. That is, when the "distal region" corresponds to the "first region" of the present invention and the "proximal region" corresponds to the "second region" of the present invention, the "first inclined surface 32b" corresponds to the present invention. Corresponds to the "sloping surface" of. Further, when the swing support 41 is in the proximal region, the cam 21 contacts the flat surface 32a during one rotation and does not contact the second inclined surface 32c, and the swing support 41 is in the distal region. At this time, the cam 21 comes into contact with both the flat surface 32a and the second inclined surface 32c during one rotation. That is, when the "proximal region" corresponds to the "first region" of the present invention and the "distal region" corresponds to the "second region" of the present invention, the "second inclined surface 32c" corresponds to the present invention. Corresponds to the "sloping surface" of.

(Sixth Embodiment)
Next, the variable valve mechanism 20F according to the sixth embodiment will be described with reference to FIG. FIG. 9 is an enlarged view of the swing arm 31 of the variable valve mechanism 20F according to the sixth embodiment and its vicinity.

In the present embodiment, the upper surface 32 of the swing arm 31 does not include an inclined surface with which the cam 21 contacts. That is, the maximum lift amount of the valve 10 changes before and after the position change of the swing support 41, but the opening / closing timing of the valve 10 does not change.

(7th Embodiment)
Next, the variable valve mechanism 20G according to the seventh embodiment will be described with reference to FIG. FIG. 10 is an enlarged view of the swing arm 31 of the variable valve mechanism 20G according to the seventh embodiment and its vicinity.

In this embodiment, the shape of the swing arm 31 is the same as that in the first embodiment. In the present embodiment, the variable valve mechanism 20G further comprises an urging member 51 that applies an urging force in the direction of pressing the swing arm 31 against the cam 21, and a support member 52 that supports one end of the urging member 51. Further prepare.

The support member 52 is arranged above the swing arm 31. The support member 52 is fixedly arranged with respect to the axis C1 of the cam shaft 22, for example. The support member 52 is fixed to, for example, one of a cylinder head 2, a cylinder head cover that covers the upper portion of the cylinder head 2, and a casing that covers the cylinder head 2.

The urging member 51 is provided between the swing arm 31 and the support member 52. For example, the urging member 51 is a coil spring. The upper end portion 51a of the urging member 51 is connected to the support member 52, and the lower end portion 51b of the urging member 51 is connected to the swing arm 31. Since the swing arm 31 is pressed against the cam 21 by the urging member 51, it is possible to prevent the swing arm 31 from separating from the cam 21 while the cam 21 makes one rotation. That is, even when the base circular portion 21a of the cam 21 is in a position facing the swing arm 31, the swing arm 31 is maintained in contact with the cam 1. At this time, the tappet surface 18a does not have to be in contact with the swing arm 31.

In this embodiment as well, the same effect as in the first embodiment can be obtained. Further, by applying an urging force in the direction in which the urging member 51 presses the swing arm 31 against the cam 21, the dynamic characteristics of the valve 10 such as jumping and bouncing and the contact surface pressure of the cam 21 and the like with respect to the swing arm 31 are applied. Can be adjusted.

(8th Embodiment)
Next, the variable valve mechanism 20H according to the eighth embodiment will be described with reference to FIG. FIG. 11 is an enlarged view of the swing arm 31 of the variable valve mechanism 20H according to the eighth embodiment and its vicinity.

In the present embodiment, the mounting position of the support member 54 that supports the urging member 51 is different from that in the seventh embodiment. In this embodiment, the support member 54 is fixed to the swing support 41. The support member 54 includes a first extending portion 54a extending upward from the swing support 41 and a second extending portion 54b extending from the upper end portion of the first extending portion 54a toward the cam 21.

The urging member 51 is provided between the swing arm 31 and the second extending portion 54b of the support member 54. The upper end portion 51a of the urging member 51 is connected to the second extending portion 54b of the support member 54, and the lower end portion 51b of the urging member 51 is connected to the swing arm 31.

In this embodiment as well, the same effect as in the seventh embodiment can be obtained. Further, in the present embodiment, the swing support 44 and the support member 54 move integrally. In this way, since the urging member 51 moves linearly in the direction orthogonal to the valve axis C2 integrally with the swing support 41, the urging member when the moving device 43 changes the position of the swing support 41. The change in the urging force of 51 can be suppressed.

The urging member 51 that applies an urging force in the direction of pressing the swing arm 31 against the cam 21 is not limited to that shown in the seventh and eighth embodiments. For example, the urging member 51 may be provided below the swing arm 31 instead of above it. Further, the urging member 51 does not have to be a coil spring, but may be a torsion spring, a leaf spring, or the like.

(9th Embodiment)
Next, the variable valve mechanism 20I according to the ninth embodiment will be described with reference to FIG. FIG. 12 is an enlarged view of the swing arm 31 of the variable valve mechanism 20I according to the ninth embodiment and its vicinity.

In the present embodiment, unlike the first embodiment, the tappet surface 18a bulges toward the tappet 18 instead of the swing arm 31 bulging toward the tappet 18. Specifically, the lower surface 33 of the swing arm 31 includes a flat surface 33b parallel to the flat surface 32a. Further, the tappet surface 18a is curved upward in a convex shape when viewed along the axis C1.

In this way, when the moving device 43 moves the swing support 41, the flat surface 33b slides on the convex tappet surface 18a as the swing arm 31 moves. As the swing arm 31 moves, the distance from the contact position of the swing arm 31 with the tappet 18 to the swing shaft 42 of the swing arm 31 changes.

The change in the lever ratio after the position change of the swing support 41 with respect to the lever ratio before the position change of the swing support 41 is smaller than that in the first embodiment, but this embodiment is also the same as in the first embodiment. The effect can be obtained.

(10th Embodiment)
Next, the variable valve mechanism 20J according to the tenth embodiment will be described with reference to FIG. FIG. 13 is an enlarged view of the swing arm 31 of the variable valve mechanism 20J according to the tenth embodiment and its vicinity.

In the present embodiment, unlike the first embodiment, the swing arm 31 is composed of a tip end side arm portion 31a and a proximal end side arm portion 31b. The tip end side arm portion 31a is a portion of the swing arm 31 on the side far from the swing support 41. A flat surface 32a is arranged on the upper surface of the tip end side arm portion 31a, and a bulging surface 33a is arranged on the lower surface of the tip end side arm portion 31a. The base end side arm portion 31b is a portion of the swing arm 31 on the side close to the swing support 41. An inclined surface 32b is arranged on the upper surface of the base end side arm portion 31b.

The tip side arm portion 31a extends in the direction along the flat surface 32a. That is, the tip end side arm portion 31a extends in a direction orthogonal to the axis C2 of the valve 10 when viewed from the direction along the axis C1. On the other hand, the base end side arm portion 31b extends in a direction along the inclined surface 32b from the end portion of the tip end side arm portion 31a on the side close to the swing support 41. That is, the tip end side arm portion 31a extends in a direction inclined with respect to a direction orthogonal to the axis C2 of the valve 10 when viewed from the direction along the axis C1. The front end portion of the tip end side arm portion 31a is swingably supported around the swing shaft 42 by the swing support 41. The moving direction of the swing support 41 by the moving device 43 is the same as that of the first embodiment.

(11th Embodiment)
Next, the variable valve mechanism 20K according to the eleventh embodiment will be described with reference to FIG. FIG. 14 is a schematic cross-sectional view showing the variable valve mechanism 20K of the engine and its periphery according to the eleventh embodiment.

The variable valve mechanism 20K of this embodiment is applied to an overhead valve type (OHV type) engine instead of a double overhead camshaft type (DOHC type) engine. That is, the cam 21 and the cam shaft 22 are arranged on the side surface of the cylinder. The variable valve mechanism 20K has a rocker arm 71 that abuts on the tappet surface 18a and presses downward, a support member 72 that swingably supports the rocker arm 71, and a push whose upper end is engaged with the rocker arm 71. A rod 73 is provided. The push rod 73 has a flat transmission surface 73a at the lower end.

A swing arm 31 is provided between the transmission surface 73a and the cam 21. That is, in the first embodiment, the swing arm 31 directly pushes down the tappet surface 18a, whereas in the present embodiment, the swing arm 31 pushes up the transmission surface 73a of the push rod 73 and passes through the rocker arm 71. Push down the tappet surface 18a.

Since the structures of the swing arm 31, the swing support 41, the moving device 43, and the like are the same as those in the first embodiment, the description thereof will be omitted. In the present embodiment, unlike the first embodiment, the cam 21 is arranged below the swing arm 31, and the swing arm 31 extends forward from the swing support 41, so that the swing arm 31 swings. Regarding the directions in the description of the dynamic support 41 and the moving device 43, "front" and "rear" are read as "rear" and "front", respectively.

(Other embodiments)
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

For example, in the above embodiment, the variable valve mechanism on the exhaust side has been described as a representative, but the present invention can also be applied to the variable valve mechanism on the intake side. In this case, with respect to the concept of direction used in the above embodiment, "front" and "rear" may be read as "rear" and "front", respectively.

Further, the configurations of the first to eleventh embodiments and the modifications thereof can be combined as appropriate. Further, the variable valve mechanism of the present invention may be applied to a single overhead camshaft type (SOHC type) engine.

2: Cylinder head 3: Combustion chamber 4: Port 10:

Valves

20A, 20B, 20C, 20D, 20E, 20F, 20G, 20H, 20I, 20J, 20K: Variable valve mechanism 21: Cam 22: Cam shaft (rotation shaft) )
31: Swing arm 32a: Flat surface 32b: Inclined surface 32b ₁ : Curved surface 32c: Inclined surface 32d: Inclined surface 32e: Inclined surface 33a: Swelling surface 41: Swing support 42: Swing shaft 43: Moving device

Claims

A variable valve mechanism that changes the lift characteristics of a valve that opens and closes the intake or exhaust ports of an engine.
A cam that rotates in conjunction with the rotation of the crankshaft of the engine,
A swing arm that is pressed by the rotating cam to swing around a swing axis parallel to the rotation axis of the cam and operates the valve according to the swing angle.
A swing support that swingably supports the swing arm around the swing shaft,
A moving device for linearly moving the swing support together with the swing arm in a direction orthogonal to the valve axis is provided.
A variable valve mechanism in which the swing arm has a flat surface extending along the longitudinal direction of the swing arm, and the cam comes into contact with the flat surface during one rotation.
The moving device changes the position of the swing support between the first region and the second region.
The swing arm is connected to one end of the flat surface in the longitudinal direction of the swing arm and has an inclined surface inclined with respect to the flat surface.
When the swing support is in the first region, the cam contacts the flat surface during one revolution and does not contact the inclined surface.
The variable valve mechanism according to claim 1, wherein when the swing support is in the second region, the cam comes into contact with both the flat surface and the inclined surface during one rotation.
The inclined surface is inclined with respect to the flat surface so that the surface of the swing arm facing the cam is formed in a concave shape by the inclined surface and the flat surface.
The inclined surface has a curved surface portion connected to the flat surface, and has a curved surface portion.
The variable valve mechanism according to claim 2, wherein the curved surface portion is curved so that the inclination with respect to the flat surface gradually increases as the distance from the flat surface increases.
The variable valve operating mechanism according to any one of claims 1 to 3, further comprising an urging member that applies an urging force in a direction of pressing the swing arm against the cam.
The variable valve mechanism according to claim 4, wherein the moving device linearly moves the urging member in a direction orthogonal to the valve axis, integrally with the swing arm and the swing support.
The variable valve mechanism according to any one of claims 1 to 5, wherein the swing arm is provided between the cam and the valve.
The variable valve mechanism according to claim 6, wherein the rotation axis of the cam is orthogonal to the valve axis.
A tappet having a plane orthogonal to the valve axis is attached to the base end of the valve.
The swing arm has a bulging portion that bulges toward the tappet and comes into contact with the tappet.
The variable valve mechanism according to claim 6 or 7, wherein the moving device moves the swing arm within a range in which the bulging portion overlaps the plane when viewed along the valve axis.