JP2964940B2 - Variable valve mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable valve mechanism capable of changing an intake period and an exhaust period of an intake / exhaust valve according to an operating state of an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, in order to increase the torque of an internal combustion engine at low and medium speeds and increase the output at high speed, a variable valve mechanism in which intake and exhaust periods of intake and exhaust valves are changed. Are known (Japanese Patent Laid-Open No. 6-18532,
No. 3905). Such a variable valve mechanism is provided with a cam lobe having a cam portion for opening and closing a valve member (an intake valve and an exhaust valve) on a camshaft that is rotationally driven from a crankshaft of an internal combustion engine, or for one rotation of the camshaft. It has a complicated configuration provided with a transmission mechanism for changing the rotation speed during one rotation of the cam lobe. And the camshaft of these variable valve mechanisms is
As described above, since the camshaft receives a large rotational force from the crankshaft, considering the weight reduction and cost reduction of the valve operating mechanism, the outer diameter only near the part receiving the rotational force is increased, and the rigidity of the camshaft itself is increased. In addition, when the valve mechanism is made to bear on the internal combustion engine main body, the vicinity of the camshaft where the rotational force is transmitted is supported by the internal combustion engine main body, so that the entire camshaft can be reduced in deflection and deflection. preferable.

[0003] When the valve mechanism is mounted on the main body of the internal combustion engine in consideration of such points, the number of processing steps of the internal combustion engine is increased due to the difference in the outer diameter of the camshaft, and the transmission mechanism and the cam lobe are provided on the outer periphery of the camshaft. There is a concern that the mounting of parts may make it difficult to set bearing locations. Also, when considering a single camshaft, in the machining from a material due to a difference in outer diameter, production efficiency is deteriorated due to wasted material and an increase in machining time.

Further, since a cam lobe or the like is externally fitted on the outer periphery of the cam shaft, it is necessary to grind the outer diameter of the camshaft so that the outer diameter is accurate. In this case, however, the cylindrical grinder 35 shown in FIG. As shown, a work (a member such as a cam shaft) 33
Center holes are provided in both end surfaces of the headstock 36, and a fixed immovable rotation center line is formed at both centers of the headstock sensor 36a of the headstock 36 and the tailstock center 37a of the tailstock 37.
It is necessary to carry out cylindrical grinding for moving in parallel, and also in this point, the production efficiency is deteriorated.

As a method for increasing the production efficiency of the camshaft, as shown in FIG. 5, a metal steel pipe 30 having a uniform diameter is drawn from a head press-fit portion 30a at one end to a lower end 30b by drawing.
, And each spline projection 30c and the journal 30d into which the sleeve is fitted.
Is formed by cross rolling, and thereafter the outer peripheral surface of the journal portion 30d is polished to increase the accuracy (Camshaft) (JP-A-6-335742).

[0006]

However, since the drive shaft having the above-described structure is formed in such a shape that its diameter is gradually reduced from one end 30a to the other end 30b, the center of rotation such as cylindrical grinding is used when polishing. A coreless grinding that does not need to make a wire and can increase production efficiency, that is, a work (a member such as a camshaft) as shown in a coreless grinding machine 40 in FIG.
33 is supported by the work supporting plate 41 and the adjusting grindstone 42, and is simultaneously turned and guided on the guide plate shapes 43, 43 along the direction of the work axis, and the method of polishing by the grinding grindstone 44 cannot be performed. It must be made. For this reason, the number of processing steps increases, work efficiency deteriorates, and processing costs increase. Further, in the drive shaft 30, since the diameter of each of the journal portions 30d is also gradually reduced, the inner diameters of the bearing portions that support the respective journal portions are all different. For this reason, the number of processing steps for the bearing portion of the cylinder head that supports each journal portion 30d is increased, so that not only the processing cost is increased but also the production efficiency is poor.

The present invention has been made in view of the above points, and in an internal combustion engine having a complicated variable valve mechanism, the workability of a bearing portion and a camshaft of an internal combustion engine main body is improved to improve work efficiency. And a variable valve mechanism that reduces the machining cost.

[0008]

According to the present invention, there is provided a first rotating shaft member driven to rotate in conjunction with a crankshaft of an internal combustion engine, and an outer periphery of the first rotating shaft member. A second rotating shaft member that is rotatably fitted to the outer periphery of the first rotating shaft member and that opens and closes the valve member by a cam portion; A transmission mechanism for shifting the transmission speed to the second rotation shaft member, a first bearing surface provided on the first rotation shaft member and supported by the internal combustion engine via a first bearing, and A second bearing surface provided on a shaft member and supported by the internal combustion engine via a second bearing formed to have the same diameter as the first bearing, wherein the second rotating shaft of the first rotating shaft member is provided. member fitted over the portion of the outer diameter and the second inner diameter substantially <br/> like properly of the rotating shaft member, wherein 1 in the center line and the second bearing surface of the bearing surface
The core wires coincide with each other, and the
The first bearing and the second bearing have the same height .

According to a second aspect of the present invention, in the first rotary shaft member, a shaft end including the first bearing surface and a shaft portion to which the second rotary shaft member is fitted are formed as separate products. Ru der those in.

According to a third aspect of the present invention, the end of the shaft is fitted to the end of the shaft, and the end of the shaft is stopped by a stop means. In particular, the detent means for attaching the shaft and the shaft end is
Press-fitting is preferred. In claim 4 , the transmission mechanism is different from the first rotation center axis of the first rotation shaft member,
And a bearing member having a bearing portion having a second rotation center axis parallel to the first rotation center axis; and a first bearing supported by the bearing portion and connected to the first rotation shaft member.
An intermediate rotating member that rotates with the rotation of the rotating shaft member and transmits this rotating force to the second rotating shaft member is provided.

In a fifth aspect , a plurality of the second rotating shaft members are externally fitted to the shaft portion of the first rotating shaft member,
The plurality of second rotating shaft members are each provided with a second bearing surface having the same diameter as the first bearing surface. The rotation of the crankshaft causes the first rotation shaft member to rotate. The transmission mechanism changes the speed of rotation of the first rotating shaft member according to the operating state of the internal combustion engine and transmits the rotation to the second rotating shaft member. The second rotating shaft member controls opening and closing of the valve member in accordance with the rotation, and shortens the valve opening period when the internal combustion engine is running at a low speed and lengthens the valve opening period when the engine is at a high speed. The first rotating shaft member is rotatably supported by the internal combustion engine via a bearing surface of a first bearing provided on the shaft member, and the second rotating shaft member is provided on the shaft member and has a bearing of the first bearing. The engine is rotatably supported by the internal combustion engine via a second bearing surface having the same diameter as the surface.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below. FIG. 1 shows an internal combustion engine (hereinafter referred to as “engine”) according to the present invention.
The outline of the variable valve mechanism is described below.
FIG. 2 is an assembly perspective view of a valve operating mechanism that controls opening of an intake valve of one cylinder (for example, a first cylinder) in a multi-cylinder engine including two intake valves and two exhaust valves. 2 shows a partially cutaway front view of the cam shaft 2 of FIG.

Referring to FIG. 1, a variable valve mechanism 1 includes a hollow shaft-shaped cam lobe (second rotary shaft member) 3 at a predetermined position on a shaft portion 21 of a cam shaft (first rotary shaft member) 2. The cam lobe 3 is fitted outside (Fig. 2).
The three cam parts 3a, 3b are formed integrally. A guide groove 3c is formed on the outer end surface of the cam portion 3a of the cam lobe 3 in the radial direction from the base end to the vicinity of the protrusion tip. The cylindrical portion 3d connecting the cam portions 3a and 3b at both ends of the cam lobe 3 has a bearing surface (second bearing surface) as described later.
It is said. A hole 21a is formed in the shaft portion 21 in the diametric direction near the guide groove 3c.

An annular eccentric spacer (shaft support) 4 is fitted on the shaft 21 so as to be relatively rotatable. The rotation center of the shaft hole of the eccentric spacer 4 is eccentric from the rotation center of the shaft portion 21 by a predetermined amount. The control gear 5 is integrally provided on one end surface of the eccentric spacer 4. The control gear (shaft support member) 5 has a slightly larger diameter than the cam lobe 3. The harmonic ring (intermediate rotating member) 6 has an annular shape, is fitted around the eccentric spacer 4 so as to be relatively rotatable, and is rotatable about the rotation center of the eccentric spacer 4. Holes 6a and 6b are formed in the harmonic ring 6 on both sides on one diameter in the axial direction, and one hole 6a is connected to the other hole 6b.
The harmonic ring has a larger diameter, and a part of the circumference is open to the shaft hole of the harmonic ring 6. In addition, harmonic ring 6
Is smaller in diameter than the control gear 5.

The camshaft-side slider 7 is shaped so as to be relatively rotatably fitted into the hole 6a of the harmonic ring 6, and one side is fitted into the hole 6a and the other side is fitted into the hole 21a of the shaft portion 21. The base end of the shaft 8 is supported by the shaft 8 to which the harmonic ring 6 is slidable in the radial direction. The cam lobe-side slider 9 is rotatably fitted and supported in a hole 6b of the harmonic ring 6 via a shaft 9a provided on one end surface, and is supported by the guide groove 3 of the cam 3a.
c is slidably fitted in the radial direction. Thus, the camshaft 2 and the cam lobe 3 are relatively rotatably connected via the shaft 8, the camshaft-side slider 7, the harmonic ring 6, the eccentric spacer 4, the camlobe-side slider 9, and the guide groove 3c.

The control shaft (control rotary shaft member) 10 has substantially the same length as the camshaft 2 and is disposed directly above and parallel to the camshaft 2. The control shaft 11 is provided with a small gear 11 that meshes with the control gear 5. A drive shaft of an actuator 12 having a built-in angle sensor is connected to one end of the control shaft 10. As the actuator 12, for example, an electric motor is used. The actuator 12 is a cylinder head (not shown) of the engine.
Fixed to

The electronic control unit 13 controls the engine speed Ne input from the engine speed sensor and the throttle opening θ input from the throttle position sensor (TPS).
Operation information such as th is input, and the actuator 12 is driven according to the operation state of the engine. The actuator 1
2 is not limited to an electric motor, but may be a hydraulic motor.

Each of the cam portions 3a and 3b of the cam lobe 3 presses against the rollers of the rocker arms 14 and 15, respectively, and presses the intake valve 1
6, 17 are opened and closed. The intake valves 16 and 17 are, for example, poppet valves. Thus, the variable valve mechanism 1 that opens and closes the intake valve of one cylinder of the multi-cylinder engine is configured. A valve mechanism for opening and closing the exhaust valve of the cylinder is similarly configured.

Therefore, in the case of a four-cylinder engine, the valve train shown in FIG. 1 is provided for each cylinder along the longitudinal direction for four cylinders. Of course, the valve operating mechanism for driving the exhaust valve is similarly configured. The camshaft 2 is connected to a crank pulley (not shown) fixed to a crankshaft of the engine via a cam pulley 18 fixed to a shaft end 22 and a belt 19, and rotates in synchronization with the crankshaft. Driven.

As shown in FIG. 2, the camshaft 2 has a shaft portion 21 for mounting the cam lobe 3 and a shaft end portion 22 having a larger diameter than the shaft portion 21 and for mounting the cam sprocket 18. It is configured.
The shaft portion 21 and the shaft end portion 22 are separately formed, respectively, and are fixed and integrated later to form the camshaft 2.

The shaft portion 21 is made of a thick-walled pipe (steel pipe).
Is formed. The shaft portion 21 is provided with an annular groove 21b along the circumferential direction at the outer fitting position of each eccentric spacer 4 (FIG. 1) along the longitudinal direction on the outer peripheral surface, and a small groove is provided on the bottom surface of each annular groove 21b. Holes 21c are provided in the radial direction and circumferentially at 180 ° intervals. These small holes 21c and annular grooves 21b serve as oil passages, and supply oil supplied into the shaft portion 21 between the outer peripheral surface of the shaft portion 21 and the inner peripheral surface of the eccentric spacer 4. Further, the shaft portion 21 has a shaft 8 that supports the camshaft-side slider 7 in the diametric direction near each annular groove 21b.
The hole 21a into which (FIG. 1) fits is provided therethrough.
Each of the annular grooves 21b is a reduced diameter portion formed locally on the outer peripheral surface of the shaft portion 21.

The shaft end 22 is made of a casting or a steel material. As shown in FIGS. 2 and 3, the shaft end 22 has a cylindrical shape, a bearing surface (first bearing surface) 22 a formed on one side of an outer peripheral surface, and the shaft portion 2 on one side end surface.
A hole 22b is formed at one end of the first hole, and a large-diameter screw hole 22c for fixing the cam pulley 18 (FIG. 1) is formed at the center of the other end surface. And bearing surface 2
The outer diameter of 2a and the outer diameter of the cylindrical portion (second bearing surface) 3d of the cam lobe 3 (FIG. 1) provided for each cylinder are formed to be the same diameter (FIG. 2).

As shown in FIG. 2, the bearing surface 22a and the cylindrical portion 3d are provided with a cylinder head (internal combustion engine main body).
The bearings 50a and the cam cap 50b are formed in cooperation with each other. For this reason, the bearing hole for bearing the camshaft 2 and the cam lobe 3 can be machined in one stroke by using a hole machining means (drill or the like) having the same diameter, so that the workability is improved. Then, the bearing surface 22a, an annular groove 22e is provided along the circumferential direction, radially on the bottom of the annular groove 22e stoma 2 2 f (3) are drilled. A plurality of positioning holes 22d for positioning and attaching the cam pulley 18 in FIG. 1 are formed around the screw hole 22c.

The camshaft 2 is divided into a shaft portion 21 and a shaft end portion 22 having a larger diameter than the shaft portion 21.
By integrating later, a material suitable for the size of the shaft portion 21 and the shaft end portion 22 can be selected, and the machining allowance can be set to a minimum. Shaft part 21
And the shaft end 22 are integrated after the outermost diameter of the shaft 21 is polished. The outermost diameter polishing of the shaft portion 21 can be performed by centerless grinding (centerless polishing) which does not require setting of a rotation center axis over the entire length of the shaft portion 21 while feeding the shaft 21 in the axial direction. Thereby, workability of the camshaft 2 is improved. Also,
In particular, when the shaft portion 21 and the shaft end portion 22 are integrated by press-fitting, the shaft portion 21 is formed by centerless grinding.
Since the entire portion including the press-fitted portion to the shaft end 22 is polished, the press-fitted portion does not need to be newly provided with another process, and the workability is also improved in this respect. Furthermore, since the shaft portion 21 can be polished using a centerless grinding machine which is relatively more compact than a cylindrical grinding machine, there is an advantage that the installation place of the machine can be reduced.

Next, the shaft portion 21 and the shaft end portion 22
And are integrated. That is, one end of the shaft portion 21 is pressed into the hole 22b of the shaft end portion 22. After the end of the shaft portion 21 is press-fitted into the hole 22b, small holes 22f, 21f are integrally formed in the bottom surface of the annular groove 22e provided on the bearing surface 22a of the shaft end 22 in the radial direction. Then, the lock pin 23 is driven into these holes 22f, 21f.
At this time, the annular groove 22e engages the lock pin 23 with the small hole 21.
f, 22f when the lock pin 23 is generated.
It absorbs the swelling of the surface of the bearing surface 22a in the vicinity,
The generation of a convex portion on the surface of the bearing surface 22a is prevented. Thereby, the shaft portion 21 and the shaft end portion 22 are firmly fixed and integrated.

Further, small holes 22g, 21g penetrating the shaft end 22 and the shaft portion 21 are formed on the bottom surface of the annular groove 22e of the shaft end 22 at intervals of 180 ° in the radial direction and the circumferential direction. It is laid in existence. These small holes 21g and 22g and the annular groove 22e serve as an oil passage, and supply oil supplied into the shaft portion 21 between the bearing surface 22a of the shaft end portion 22 and the bearing formed on the cylinder head. I do. The lock pin 23 is
The head is slightly immersed in the hole 22f in the driven state, so that the flow of oil in the annular groove 22e is improved and interference with the bearing of the cylinder head is prevented.

The integration of the shaft portion 21 and the shaft end portion 22 (rotation prevention means) may be performed only by press-fitting or by simply hitting the lock pin. The press-fitting is performed as described above, and the lock pin 23 is further driven and fixed. You may. Or,
It may be fixed by brazing, friction welding, plasma welding or the like. The integration of the shaft portion 21 and the shaft end portion 22 employs any one of these welding, press-fitting, and pin-fixing to avoid thermal deformation of the outermost-diameter polished portion of the shaft portion 21 and a process after the integration. Less.

The shaft portion 21 and the shaft end portion 22
In the case where is formed by a different member, press-fitting or pinning fixation is adopted for these integration. This allows
Inexpensive materials can be used for the portions that do not require quenching. The outer diameter machining of the shaft end 22 is performed after the shaft 21 and the shaft end 22 are integrated.
This is performed based on the outer diameter of Thereby, accuracy at the time of shaft assembly is obtained, and when used as the camshaft 2,
Since straightness is ensured, it does not lead to an increase in engine friction.

FIG. 4 shows another embodiment of a fixed portion between the shaft portion and the shaft end constituting the camshaft 2. In FIG. 4, the shaft portion 25 corresponds to the shaft portion 21 (FIG. 2), and has a screw hole 25h formed by engraving a screw on the inner surface at one open end. This screw hole 25h is for attaching the cam pulley 18 (FIG. 1). on the other hand,
The shaft end 26 has a hole 26b formed at the center thereof and has a pressed cylindrical shape. The inner diameter of the shaft end 26 is such that one end of the shaft 25 can be press-fitted. The other is the shaft end 22
It is the same as (FIG. 2).

Then, one end of the shaft portion 25 is pressed into the hole 26b of the shaft end portion 26 over the entire length of the hole 26b and fixed. As a result, the press-fit length between the shaft portion 25 and the shaft end portion 26 becomes longer, and the lock pin becomes unnecessary. Of course, a lock pin may be driven in and fixed. Further, the shaft portion 25 and the shaft end portion 26 may be fixed by welding as described above. Holes 2 around the screw holes 25h are formed on the end surfaces of the shaft end portions 26 and 25.
7, 28 are drilled. The hole 27 is for the cam pulley 18
The hole 28 is a hole for driving a detent member (corresponding to the lock pin 23 in FIG. 3) for detent between the shaft portion 25 and the shaft end 26.

Returning to FIG. 1, the camshaft 2 is disposed horizontally along a longitudinal direction on a cylinder head (not shown) of the engine, and bearing portions (not shown) provided at both ends of the cylinder head. It is rotatably supported on Shaft end 2
2, a bearing surface 22a is rotatably supported by a bearing portion provided on the cylinder head and a cam cap (both not shown).

The shaft portion 21 has a cylindrical portion (bearing surface) 3d of each cam lobe 3 rotatably supported by a bearing provided on the cylinder head and a cam cap. Each bearing of the cylinder head is provided between two intake valves 16 and 17 of each cylinder of the cylinder head. The control shaft 11 is disposed directly above the camshaft 2 and in parallel with the camshaft 2.

The cam lobe 3 is supported on the bearing of the cylinder head by a guide for connecting the shaft 21 of the cam shaft 2 and the cam lobe 3 to one side of the cam 3a of the cam lobe 3 so as to be relatively rotatable. The groove 3c, the eccentric spacer 4, the control gear 5, the harmonic ring 6, the camshaft-side slider 7, the cam-lobe-side slider 9, and the like are arranged, and it is difficult to provide a bearing for supporting the shaft 21 in terms of space. thing. It is preferable to support the cam lobe 3 to which a load is applied at the time of opening the valve, and in consideration of the weight reduction of the camshaft 2, in particular, the vicinity of the portion receiving the rotational force from the crankshaft (the bearing surface 22 a in this embodiment). When the outer diameter dimension of the other member (the shaft portion 21) is largely different from that of the other member (shaft portion 21), in order to improve the workability of the bearing hole on the cylinder head side,
This is because it is easy to make the outer diameter dimension of the part receiving the rotational force coincide with that of the part receiving the rotational force.

Lubrication between the bearing portion of the cylinder head and the cylindrical portion (bearing surface) 3d of the cam lobe 3 is performed by supplying oil from the bearing portion side of the cylinder head. Also, the inner peripheral surface of the cylindrical portion 3d of the cam lobe 3 and the shaft portion 21
Lubrication between the bearing portion of the cylinder head and the bearing surface of the cylindrical portion 3d of the cam lobe 3 is caused by a portion of the oil supplied to the small hole formed in the cylindrical portion 3d. (Not shown).

Next, the operation of the variable valve mechanism 1 will be described.
As shown by arrows A to D in FIG. 1, the rotation of the camshaft 2 is transmitted from the shaft 8 to the camshaft-side slider 7 → the harmonic ring 6 → the camlobe-side slider 9 → the guide groove 3 c of the camlobe 3 → the camlobe 3. , The cam lobe 3 rotates. With the rotation of the cam lobe 3, the cam portions 3a, 3b
Drives the intake valves 16, 17 to open and close via the rocker arms 14, 15. When the engine is in a steady operation state, the eccentric spacer 4 is fixed without rotating and serves to separate the rotation center of the camshaft 2 and the cam lobe 3 from the rotation center of the harmonic ring 6. As a result, the camshaft 2 becomes 1
The primary sine wave acceleration / deceleration can be alternately transmitted to the cam lobe 3 during rotation.

The phase of the eccentricity of the eccentric spacer 4 with respect to the center of the camshaft 2 is changed by the actuator 12 via the control shaft 10, the gear 11, and the control gear 5, and the phase of the primary sine wave acceleration / deceleration of the cam lobe 3 is controlled. I do. That is, when the eccentric spacer 4 is eccentric to the opposite side (upper side in the drawing) to the rocker arm 14, while the camshaft 2 rotates 90 °, the harmonic ring 6 is delayed by a first predetermined angle (for example, β). The cam lobe 3 is delayed by a second predetermined angle (for example, α (> β)) larger than the first predetermined angle (β).

When the engine is running at a low speed, the electronic control unit 13 drives the actuator 12 to eccentrically move the rotation center of the eccentric spacer 4 upward with respect to the rotation center of the camshaft 2 in a direction opposite to the rocker arm 14. Let it. As a result, the cam lobe 3 is delayed by a second predetermined angle (α) with respect to the rotation of the camshaft 2 near the opening position of the intake valve 16, and conversely near the valve closing position by the second predetermined angle (α)
Just go on. As a result, the valve opening period can be shortened.

The electronic control unit 13 drives the actuator 12 to move the rotation center of the eccentric spacer 4 in the same direction (downward) as the rocker arm 14 with respect to the rotation center of the camshaft 2 when the engine is in a high-speed operation state. Eccentric. Accordingly, the cam lobe 3 advances by the second predetermined angle (α) with respect to the rotation of the camshaft 2 near the opening position of the intake valve 16, and conversely, near the valve closing position, the second predetermined angle (α)
Only late. As a result, the valve opening period can be lengthened, and the output of the engine can be increased.

The assembled camshaft according to the present invention is shown in FIG.
The present invention is not limited to the case where the present invention is applied to a variable valve mechanism of an eccentric mechanism of the type shown in FIG. 1, but can be applied to other types of variable valve mechanisms such as a viscous coupling type variable valve mechanism. It is. The variable valve mechanism of this viscous coupling type is, for example, a valve drive system for an internal combustion engine (International Publication No. WO95 / 0801).
Is disclosed.

[0040]

According to the present invention as described in the foregoing, in the claim 1, the inner diameter of the outer diameter of the portion where the second rotating shaft member of the first rotating shaft member is fitted the second rotating shaft member There's like almost
And a center line of the first bearing surface and a center line of the second bearing surface.
Coincide with each other, and the first
Since the height of the bearing and the height of the second bearing are the same , the rotation of the second rotary shaft member does not fluctuate, and a load is applied to the connection portion between the second bearing surface and the transmission member. Is prevented, and the durability is improved.

According to the second aspect, the camshaft is formed separately from the shaft portion and the shaft end portion, and is integrated later, whereby the camshaft can be formed of different materials, thereby reducing the material cost. In addition, an inexpensive material can be set in the quenching unnecessary portion, and furthermore, the cutting allowance can be set to a minimum, and the processing cost and material cost can be reduced. Further, the accuracy at the time of shaft assembly is obtained, and the straightness of the camshaft is ensured, so that engine friction is reduced and engine performance is stabilized.

[0042]

According to the third aspect of the present invention , the shaft portion and the shaft end portion are fitted and fixed, and the rotation preventing means is provided.
Both can be reliably fixed. When the rotation preventing means is press-fitted, the press-fit portion for press-fitting the shaft portion and the shaft end portion can be simultaneously polished when the outer diameter of the shaft portion is centerlessly ground, so that the press-fit portion (fitting portion) It is not necessary to separately perform special precision processing, and the workability of the camshaft can be improved.

In the fourth aspect , the transmission mechanism for transmitting the rotation of the first rotary shaft member to the second rotary shaft member is constituted by an eccentric mechanism, so that the configuration of the variable valve mechanism becomes relatively simple, and the reliability is improved. Improvement, cost reduction, etc. are achieved.

[Brief description of the drawings]

FIG. 1 is an assembled perspective view of a main part of a variable valve mechanism according to the present invention.

FIG. 2 is a partially cutaway front view of a camshaft of the variable valve mechanism of FIG. 1;

3 is a cross-sectional view of the camshaft of FIG. 2 taken along the line III-III.

FIG. 4 is a sectional view showing another embodiment of the camshaft of FIG. 2;

FIG. 5 is a front view showing a part of a conventional drive shaft (cam shaft) in cross section.

FIG. 6 is an explanatory diagram of a case where a workpiece is ground by a cylindrical grinding machine.

7A and 7B are explanatory views of a case where a work is ground by a centerless grinding machine, and FIG. 7A is a plan view thereof and FIG.
Shows a side view of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Variable valve mechanism 2 Cam shaft 3 Cam lobe 3a, 3b Cam part 3d Cylindrical part (bearing surface) 4 Eccentric spacer 5 Control gear 6 Harmonic ring 7 Cam shaft side slider 9 Cam lobe side slider 10 Control shaft 11 Gear 12 Actuator 13 Electronic control Apparatus 14, 15 Rocker arm 16, 17 Intake valve 18 Cam pulley 19 Belt 21, 25 Shaft portion 22, 26 Shaft end 21b Annular groove 21c 22a, 26a Bearing surface 23 Lock pin

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Masahiko Kubo 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation (56) References JP-A-6-335742 (JP, A) JP JP-A-7-301106 (JP, A) JP-A-4-183905 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F01L 1/04 F01L 13/00 301

Claims (5)

(57) [Claims] A first rotating shaft member rotatably driven in conjunction with a crankshaft of the internal combustion engine; and a first rotatable member fitted around an outer periphery of the first rotating shaft member so as to be relatively rotatable;
A second rotating shaft member for driving the opening and closing of the valve member by the cam portion; and a second rotating shaft member provided on the outer periphery of the first rotating shaft member so as to be relatively rotatable;
A transmission mechanism for changing the speed of rotation of the first rotation shaft member and transmitting the rotation to the second rotation shaft member; a first mechanism provided on the first rotation shaft member and supported by the internal combustion engine via a first bearing A first bearing surface provided on the second rotating shaft member and supported by the internal combustion engine via a second bearing formed to have the same diameter as the first bearing; outer diameter and front Symbol inner diameter substantially equal properly the second rotating shaft member portion the second rotating shaft member of the shaft member is fitted, before
The center line of the first bearing surface coincides with the center line of the second bearing surface.
And the first bearing provided in the internal combustion engine.
A variable valve mechanism, wherein the heights of the second bearings are the same . Wherein said first rotation shaft material, that a shaft portion of the second rotating shaft member and the shaft end portion including said first bearing surface is fitted is configured separately article The variable valve mechanism according to claim 1, wherein: 3. The variable valve mechanism according to claim 2 , wherein said shaft end is fitted to an end of said shaft, and is prevented from rotating by a rotation preventing means. Wherein said transmission mechanism is different from the first rotation center axis of the first rotating shaft member and the shaft support member having a shaft support having a first central axis of rotation parallel to the second rotation center axis line And, while being supported by the shaft support portion, connected to the first rotation shaft member and rotated with the rotation of the first rotation shaft member,
The variable valve mechanism according to any one of claims 1 to 3 , further comprising an intermediate rotation member that transmits the rotation force to the second rotation shaft member. Wherein a plurality of the second rotating shaft member is fitted on the shaft portion of the first rotating shaft member, the plurality of the second rotating shaft member respectively, the same diameter as the first bearing surface The variable valve mechanism according to claim 4 , further comprising a second bearing surface formed on the second bearing surface.