KR20090103686A - Variable valve gear for an internal combustion engine - Google Patents

Abstract

PURPOSE: A variable valve drive device of an internal combustion engine is provided to suppress unnecessary displacement of a bearing member and to prevent the end surface of the bearing member from moving to the direction in which the bearing member is drawn out. CONSTITUTION: A variable valve drive device of an internal combustion engine comprises a cylinder head(2), a cam drive shaft(10), a cam lobe(16), and a variable valve device. The cylinder head has an intake valve and an exhaust valve. The cam drive shaft is supported by the cylinder head to rotate. The cam lobe is supported by the cam drive shaft to rotate. The cam lobe has a cam driving the valve. The variable valve device controls the eccentricity of an eccentric shaft member and varies the opening period of the valve.

Description

Variable valve gear for internal combustion engines {VARIABLE VALVE GEAR FOR AN INTERNAL COMBUSTION ENGINE}

TECHNICAL FIELD The present invention relates to a variable valve gear for an internal combustion engine that varies the opening period of a valve.

In relation to reciprocating engines (internal combustion engines) mounted in automobiles, in order to appropriately control the valve characteristics of the intake and exhaust valves, variable valve gears for varying the valve opening period of the valve in accordance with the operating state of the engine have been developed. .

Most of the variable valve gears in this manner have a cam lobe rotatably fitted to the outer circumferential surface of the cam shaft (cam drive shaft) supported by the cylinder head, as disclosed in Japanese Patent Publication No. 10-280925. And a valve opening period variable mechanism for varying the rotational speed of the camshaft to transmit rotation to the cam lobe. Many valve opening period variable mechanisms have a drive arm fixed at a point adjacent to the cam lobe on the outer circumferential surface of the camshaft, and an eccentric shaft is fitted to the outer circumferential surface of the camshaft so as to be eccentrically rotatable at a point adjacent to the drive arm, and the harmonic ring (middle Rotating member) has an Oldham coupling structure, which is rotatably fitted to the outer circumferential surface of the eccentric shaft. Specifically, the constant speed rotation of the camshaft output from the drive arm is transmitted to the harmonic ring using the transmission member on the inlet side, and the constant speed rotation is changed to an inconstant speed rotation in which the speed is changed at a predetermined cycle, and the rotation is made on the outlet side. It employs a structure for driving the valve by transferring from the boss portion protruding from the outer periphery of the cam lobe end to the cam lobe using the transmission member. In order to phase shift the axial position of the eccentric shaft from the axial position of the cam shaft, the delay or advancement of the rotational phase of the cam lobe relative to the rotation angle of the cam shaft is adjusted to vary the valve opening period.

In order to place the valve opening period variable mechanism in a confined area between each adjacent cylinder of the cylinder head, the mechanism is arranged side by side with the side at a point where the boss portion protruding from the end outer circumferential surface of the cam lobe is adjacent to the side of the driving arm and the harmonic ring Has a structure in which the harmonic ring is transmitted by an eccentric shaft having an outer diameter slightly larger than the cam shaft located inside the input gear portion of the variable mechanism.

As disclosed in Japanese Patent Document, the valve opening period variable mechanism is provided with a bearing portion such as a needle bearing between the outer circumferential surface of the eccentric shaft and the inner circumferential surface of the harmonic ring for smooth rotation of the harmonic ring.

The bearing portion can be displaced in the disengaging direction, specifically the cam lobe side, due to the change in the behavior of the harmonic ring (resulting in the change in the eccentric direction).

The displacement of the bearing part makes it impossible to support the harmonic ring. In addition, displacement results in abnormal wear. The bearing portion is disposed at a point eccentric with the cam shaft to support the harmonic ring, and the boss portion of the cam lobe is disposed adjacent the drive arm coaxially with the cam shaft. Because of this arrangement, the end face of the bearing portion repeatedly faces the end face of the drive arm and the end face of the boss portion of the cam lobe during rotation of the harmonic ring. In particular, the boss portion of the cam lobe is disposed outside the driving arm, so that the entirety of the end face of the boss portion completely shifts outward from the bearing portion and returns to the inside of the bearing portion. For this reason, even if minutely, when the end of the bearing portion protrudes from between the eccentric shaft and the harmonic ring, abnormal wear occurs when the edge of the bearing portion and the corner of the end face of the boss portion interfere with each other when the boss portion passes through the bearing portion.

By adopting a structure in which the bearing portion is fixed between the harmonic ring and the eccentric shaft by press fitting or a structure in which a stopper is separately installed between the harmonic ring and the eccentric shaft, the bearing portion can be prevented from coming out.

However, in the case of press-fitting, it is difficult to reliably prevent the axial movement of the bearing portion due to the high elastic strain of the harmonic ring.

If a stopper is used, the bearing part must be made short in bearing length to reduce the space for installing the stopper (deterioration of the bearing part strength). As a result, satisfactory support strength of the harmonic ring cannot be ensured, which causes other problems.

Possible methods for preventing abnormal wear include the end face of the drive arm and the end face of the cam lobe being equal to each other so that the boss portion smoothly passes between the end face of the bearing portion and the end face of the drive arm. Since the drive arm and the cam lobe are separate parts and move differently, it is impossible to completely fit the end faces of these parts together without steps or gaps. Therefore, it is difficult to prevent abnormal wear.

The present invention has been made in light of the above-mentioned issues. SUMMARY OF THE INVENTION An object of the present invention is to provide a variable valve gear for an internal combustion engine that restricts the movement of the bearing part in the direction of the bearing part having a simple structure that does not require machining on the bearing part and the intermediate rotating member and prevents interference between the end of the bearing part and the cam lobe. will be.

A variable valve gear for an internal combustion engine according to the present invention includes a cylinder head having an intake or exhaust valve; A cam drive shaft rotatably supported by the cylinder head; A cam lobe rotatably supported by the cam drive shaft and having a cam for driving the valve; And an eccentric with a drive arm fixed adjacent to one end of the cam lobe to the cam drive shaft, the cam drive shaft being pivotally supported at a position opposite the cam lobe with respect to the drive arm and having an outer circumferential surface eccentric with the axial center of the cam drive shaft. This adjustable eccentric shaft member and an intermediate rotation member rotatably supported through a bearing member and connected to the drive arm around the outer circumferential surface of the eccentric shaft member, cam rotation of the cam drive shaft through the drive arm and the intermediate rotation member. And a variable valve mechanism capable of transmitting to the lobe and adjusting the eccentricity of the eccentric shaft member to vary the opening period of the valve. The drive arm includes an end face that overlaps with the end face of the bearing member regardless of the rotational position of the drive arm relative to the chamfer shaft member when projecting along the axis of the cam drive shaft. The end face protrudes more toward the bearing member than the end face of the cam lobe.

According to this structure, the drive arm is surely facing one of the end faces of the bearing member irrespective of the rotational position of the drive arm with respect to the eccentric shaft member. Thus, the end face of the bearing member restricts movement in the direction in which the bearing member exits and suppresses unnecessary displacement of the bearing member. Even when the end of the bearing member slightly protrudes, it simply hits the end face of the drive arm and is reliably prevented from interfering with other parts of the cam lobe. It is also possible to achieve the object as a simple structure without requiring modifications to the bearing member and the intermediate rotating member.

In a preferred aspect of the invention, the drive arm has a stationary ring fixed to the cam drive shaft and an arm portion extending from the outer periphery of the stationary ring in the radially outward direction and transmitting torque to the intermediate rotating member. The bearing side end face of the fixed ring overlaps the end face of the bearing member at the drive arm.

According to this structure, the bearing member is restricted to move in the exiting direction because of the end face of the fixing ring of the drive arm. Even when the end of the bearing member slightly protrudes, it only hits the end face of the fixing ring of the drive arm, and the interference between the cam lobe and the drive arm can be reliably prevented. In addition, the object can be achieved with a simple structure in which the shape of the fixing ring is simply changed.

In another preferred aspect, the cam lobe has a boss portion to which the torque of the intermediate rotating member is transmitted at a point that deviates from the axis of the cam lobe. The boss portion extends toward the intermediate rotating member. The cam lobe is in contact with the cam lobe side end face of the stationary ring of the drive arm and has a contact surface that determines the axial position of the cam lobe relative to the drive arm. The fixed ring of the drive arm has an axial length longer than the axial length between the contact surface of the cam lobe and the tip side surface of the boss portion.

According to this structure, the contact surface of the cam lobe and the cam lobe side end surface of the driving arm come into contact with each other, whereby the axial position and the axial length of the cam lobe and the driving arm are determined. This makes it possible to accurately set the amount of protrusion of the end face of the fixing ring of the drive arm from the end face of the boss portion of the cam lobe. As a result, the end face of the boss portion and the intermediate rotating member are arranged as close as possible to each other so that the force can be smoothly transmitted from the intermediate rotating member to the boss portion.

Further scope of applicability of the present invention will become apparent from the detailed description below. However, it will be apparent to those skilled in the art that modifications and variations within the spirit and scope of the present invention from this detailed description are obvious, and therefore, the detailed description and specific examples are given by way of example only, although they represent preferred embodiments of the present invention. It must be understood.

The invention will be understood in more detail from the accompanying drawings and the following detailed description given by way of illustration only and not as a limitation of the invention.

According to the invention, the drive arm is reliably faced to any of the end faces of the bearing member irrespective of the rotational position of the drive arm relative to the eccentric shaft member, so that the end face of the bearing member moves in the direction in which the bearing member exits. There is provided a variable valve gear for an internal combustion engine which is regulated to do so and unnecessary displacement of the bearing member is suppressed.

1 is a cross-sectional view showing a variable valve gear for an internal combustion engine according to an embodiment of the present invention.

Figure 2 is an exploded perspective view showing the structure of the main part of the variable valve gear.

FIG. 3 is an enlarged cross-sectional view of a portion surrounded by circle A in FIG. 1; FIG.

4 (a) to 4 (d) are explanatory views showing the trajectory of the drive arm and the boss portion moving on the end face of the bearing portion of the variable valve gear.

5 (a) to 5 (c) are explanatory views of the operating characteristics of the variable valve gear.

6 is a diagram for explaining changes in valve opening periods obtained in accordance with operating characteristics.

<Explanation of symbols for major symbols in the drawings>

2: cylinder head

8: intake valve (valve)

10: intake cam shaft (cam drive shaft)

15: variable valve gear

16: cam robe

19: boss

28: valve opening period variable mechanism

31: drive arm

The invention will be explained based on the embodiment shown in Figs.

1 is a sectional view showing an internal combustion engine provided with, for example, a variable valve gear in an intake valve operating system of an engine. In Fig. 1, reference numeral 1 denotes a cylinder block of an internal combustion engine, for example, a cylinder block (shown only in Fig. 1) of a four-cylinder reciprocating gasoline engine (hereinafter referred to as an engine). Reference numeral 2 denotes a cylinder head attached to the head of the cylinder block 1.

First, the basic structure of the engine will be described. In the cylinder block 1, four cylinders 4 (Fig. 1 shows only a part of the cylinders) are formed so as to be arranged in series in the front-rear direction of the engine. In each cylinder 4, the piston 5 is accommodated so that reciprocation is possible, respectively. Although not shown, the piston 5 is connected to the crankshaft via a connecting rod.

The combustion chamber 6 is formed in the lower surface of the cylinder head 2 corresponding to the cylinder 4. In the combustion chamber 6, a pair of intake ports 7 and a pair of exhaust ports not shown are formed. In addition, the combustion chamber 6 accommodates two intake valves 8 (corresponding to the valves herein) for opening and closing the intake port 7 and two exhaust valves not shown for opening and closing the exhaust port. The intake valve 8 and the exhaust valve are both normally closed valves closed by a valve spring 9. Although not shown, a spark plug is arranged in the combustion chamber 6 so that a predetermined combustion cycle (four strokes including an intake stroke, a compression stroke, an explosion stroke and an exhaust stroke) is repeated.

In the upper part of the cylinder head 2, the intake cam shaft 10 (corresponding to the cam drive shaft of this application) and the exhaust cam shaft (not shown) are arranged along the direction in which the cylinder 4 is aligned. The intake camshaft 10 and the exhaust camshaft are connected to the crankshaft end part not shown through the timing chain member etc. which are not shown in figure. The intake camshaft 10 and the exhaust camshaft are rotationally driven by the shaft output output from the crankshaft.

As shown in Fig. 1, a variable valve gear 15 is mounted on the intake camshaft 10 of the engine. The variable valve gear 15 has a variable structure which varies the opening period of the intake valve 8 by changing the constant speed rotation of the camshaft to inconstant speed rotation. The variable structure is a cam lobe 16 rotatably fitted to the outer circumferential surface of the intake cam shaft 10 for each cylinder 4 and an eccentric rotation valve opening period variable mechanism 28 mounted on the cam lobe 16. It is composed.

2 is an exploded perspective view of the cam lobe 16 and the valve opening period varying mechanism 28 for one cylinder.

Each part of the variable structure will be described with reference to this particular cylinder with reference to FIG. The cam lobe 16 has a cylindrical main body 17 rotatably fitted to the outer circumferential surface of the intake camshaft 10, a pair (plural) cam portions 18 and a cam portion (formed on the outer circumferential surface of the main body 17). It has a boss portion 19 protruding from the outer peripheral portion of one end of the main body 17 positioned adjacent to 18). The outer circumferential surface between the cam portions 18 is rotatably supported by a bearing located between the intake valves 8 (shown in FIG. 1 only).

The boss portion 19 is formed of a triangular plate as shown by the dashed-dotted line in FIGS. 2 and 4 (a) to 4 (d). Specifically, the boss portion 19 has a base portion 19x protruding from the outer circumference portion of the end face of the main body 17 to the end portion, specifically forward, and having a top portion 19y of the tip portion of the main body 17. It is formed of a triangular piece of block extending in the radial direction.

The cam face of each cam portion 18 is in direct contact with a valve lifter 8a mounted to a receiving portion of the intake valve 8, for example, the base end of the intake valve 8, so that the intake valve 8 is cam portion. 18 can be driven.

The valve opening period variable mechanism 28 includes an inconstant speed mechanism 30 and a period setting unit 40 for setting the valve opening period. The inconstant speed mechanism 30 is a mechanism for transmitting the rotation to the cam lobe 16 by changing the constant speed rotation of the intake camshaft 10 to inconstant speed rotation. Specifically, the inconstant speed mechanism 30 is formed by Oldham coupling.

That is, as shown in Figs. 1 and 2, the coupling is a drive arm 31, a drive arm 31 disposed on the intake camshaft adjacent to the end face of the end portion on the boss portion 19 side of the cam lobe 16; An eccentric shaft 33 rotatably fitted to the outer circumferential surface of the intake camshaft 10 adjacent to the arm 31 and a harmonic ring 32 functioning as an intermediate rotation member fitted to the outer circumferential surface of the eccentric shaft 33. ) And a bearing portion interposed between the outer circumferential surface of the eccentric shaft 33 and the inner circumferential surface of the harmonic ring 32, for example, a needle bearing 34.

The needle bearing 34 is a cage (not shown) in which a bearing body portion obtained simply by holding a plurality of needles 34a is fitted to the outer circumferential surface of the eccentric shaft 33, and the harmonic ring 32 is placed on the outer circumference of the bearing body portion. This structure has a structure to rotatably support the harmonic ring 32. The needle 34a has a maximum length minus the length necessary to form the cage from the lengths of the opposing cylindrical surfaces of the eccentric shaft 33 and the harmonic ring 32.

The eccentric shaft 33 is composed of a shaft member having an outer diameter slightly larger than the intake cam shaft 10. The outer circumferential surface of the shaft member is eccentric with the axial center of the intake camshaft 10, and the harmonic ring 32 rotates on the outer circumferential surface of the eccentric shaft material in an eccentric state.

The drive arm 31 protrudes radially from the point of the fixed ring 31a fitted to the outer circumferential surface of the camshaft portion and the fixed ring 31a deviated from the boss portion 19 by an angle of 180 °. Has The fixing ring 31a is fixed (coaxial) to the intake camshaft 10 by a fixing member, for example, the pin member 29 (only a part of FIG. 1 is shown). The drive arm 31 is set to a point adjacent to the end face of the cam lobe 16. The boss portion 19 of the cam lobe 16 is disposed next to the side of the fixing ring 31a on the side opposite to the arm portion 31b. The boss portion 19 is located parallel to the side at a point adjacent to the side of the drive arm 31. The entire boss portion 19 is compactly arranged around the end of the drive arm 31.

The end of any one of the relay pins 35a and 35b is rotatably inserted into the end face of the tip portion of the arm portion 31b and the end face of the boss portion 19. An end portion of the relay pin 35a (inlet-side transmission member) protruding from the arm portion 31b is slidably inserted into the slide groove 36a which is formed in the end face of the harmonic ring 32 and extends in the radial direction. An end portion of the relay pin 35b (the transmission member on the outlet side) protruding from the boss portion 19 passes through the fixing ring 31a and is formed at a position shifted from the slide groove 36a at an angle of 180 degrees to extend in the radial direction. It is slidably inserted into the slide groove 36b.

Thereby, rotation of the intake camshaft 10 is transmitted from the drive arm 31 to the harmonic ring 32 via the relay pin 35a, and from the harmonic ring 32 to the relay pin 35b and the boss portion. It is transmitted to cam lobe 16 via 19. That is, the rotation of the intake camshaft 10 delays the periphery of the eccentric shaft 33 (the periphery of the intake camshaft 10) as shown in Figs. 5A and 5C. Or the cam lobe 16 after changing to a rotation in which the speed is changed at a predetermined period as shown by the solid line or the broken line in FIG. 5B through the harmonic ring 32 which rotates eccentrically while generating a progress. Delivered.

In consideration of the arrangement of the eccentric shaft 33, rotation is transmitted from the intake cam shaft 10 to the cam lobe 16 at the end face of the driving ring 31 on the harmonic ring 32 side of the fixing ring 31 a. It is designed by the end surface 31c (corresponding to the end surface part of this original part) which continues to overlap with the end surface of the needle bearing 34 when being made. The end face of the fixing ring 31a is formed to overlap the end face of the needle bearing 34 regardless of the rotational position of the drive arm 31 with respect to the eccentric shaft 33 when projecting along the axis of the cam shaft 10. do. As shown in Figs. 1 and 3 (enlarged view of the portion enclosed by circle A in Fig. 1), the end face 31c projects from the end face of the boss portion 19 toward the needle bearing 34. As shown in Figs. It is. The distance S between the boss portion 19 and the harmonic ring 32 is preferably as short as possible. This is because the relay pin 35b can be tightened with a small force, that is, torque can be smoothly transferred from the harmonic ring 32 to the boss portion 19 when the distance S is short.

For this reason, the present invention is constructed as follows. As is apparent from Fig. 3, the main body 17 of the cam lobe 16 has a contact surface 16a in contact with the left end surface of the fixing ring 31a of the drive arm 31 as shown in the drawing. The axial positioning of the cam lobe 16 with respect to the arm 31 is performed. This enables accurate relative positioning of the cam lobe 16 and drive arm 31. The holding ring 31a has an axial length B set slightly longer than the axial length between the end face 16a of the cam lobe 16 and the end face 19a of the tip portion of the boss portion 19. Therefore, the amount by which the end face 31c of the fixing ring 31a of the drive arm 31 protrudes more than the end face 16a of the cam lobe 16 can be set with high precision. In other words, the distance S can be set as short as possible.

The period setting section 40 has a structure in which the input gear 41 is integrally fitted to the eccentric shaft 33 as shown in FIGS. 1 and 2. The input gear 41 is formed of a circular gear coaxial with the intake camshaft 10. When the setting of the valve opening period is input from the input gear 41, the axial center of the eccentric shaft 33 eccentrically phases around the axial center of the intake cam shaft 10. As shown in FIG. Each section of the period setting section 40 is set in association with the maximum lift of the intake valve 8 as shown in Figs. 5A to 5C. As shown in Fig. 5C, the eccentric phase is zero in which the axial center position β of the eccentric shaft 33 is aligned above the axial center position α of the intake cam shaft 10 (opposite side of the valve). When set at an angle (upward eccentricity), the rotational phase of the cam mounting portion 18 relative to the rotational angle of the camshaft 10 is advanced to the maximum when the camshaft 10 is at an angle within the range of 0 ° to 180 °, If the camshaft 10 is at an angle within the range of 180 ° to 360 °, it is delayed to the maximum. As a result, the valve opening period is the longest for the upward eccentricity. On the contrary, as shown in Fig. 5A, the eccentric phase is aligned with the axial center position β of the eccentric shaft 31 below the axial center position α of the intake cam shaft 10 (valve side). When set at an angle of 180 ° (downward eccentric), the rotational phase of the cam mounting portion 18 with respect to the rotational angle of the camshaft 10 is maximized when the camshaft 10 is at an angle within the range of 0 ° to 180 °. Delayed, and advances to maximum when the camshaft 10 is at an angle within the range of 180 ° to 360 °. As a result, the valve opening period is the shortest in the case of downward eccentricity. In this way, the valve opening period can be varied at an angle between both positions, ie between 0 ° and 180 ° depending on the eccentric phase.

The input gear 41 is engaged with the gear 42a of the control shaft 42 (operating member) as indicated by the dashed line in FIG. When the actuator (not shown) connected to the control shaft 42 is controlled according to the operating state of the engine, the eccentric position of the harmonic ring 32 is changed according to the operating state of the engine, so that the intake valve of each cylinder 4 ( The valve opening period of 8) can be adjusted.

Operation will be described below.

In the variable valve gear 15 of the engine configured as described above, as shown in Fig. 5C by using an actuator not shown, the axial center position β of the eccentric shaft 33 on the intake side is the intake cam shaft. It is set to an eccentric phase angle of 0 ° above the axial center position α of (10). As a result, the eccentric position of the harmonic ring 32 is positioned at a predetermined point.

The cam portion 18 passing through the intake valve 8 of each cylinder 4 is displaced to the maximum during the valve opening timing and to the maximum delay during the valve closing timing, as described above. As shown by the solid line in Fig. 6, the intake valve 8 is opened and closed as a characteristic of a long valve opening period suitable for high speed operation of the engine.

On the contrary, by using the actuator, as shown in Fig. 5A, the axial position β of the eccentric shaft 25 on the intake side is O ° lower than the axial center position α of the intake cam shaft 10. Is set to the eccentric phase angle of. As a result, the eccentric position of the harmonic ring 32 is positioned at a predetermined point.

As a result, the cam portion 18 passing through the intake valve 8 of each cylinder 4 is displaced so as to be maximally delayed during the valve opening timing and to the maximum advance during the valve closing timing as described above. As shown by the broken line in Fig. 6, the intake valve 8 is opened and closed as a characteristic of a short valve opening period suitable for low speed operation of the engine. Of course, when the eccentric phase angle of the eccentric shaft 33 is changed within the range of 0 to 180 °, the valve opening period of the intake valve 8 is the valve characteristic of the minimum valve opening period shown by the broken line in FIG. It varies between the valve characteristics of the largest valve opening period shown by the solid line in five.

During the control of the valve opening period, for example, the axial center position β of the eccentric shaft 33 shown in FIGS. 4A to 4D is the axial center position α of the intake cam shaft 10. The annular end face of the needle bearing 34 faces the end face of the drive arm 31 and the boss portion of the cam lobe 16, while the harmonic ring 32 is rotated, so that it is represented in a state set below the). Face the end face of (19) is repeated. Since it is disposed outside the drive arm 31, the boss portion 19 of the cam lobe 16 has the entire end surface of the boss portion 19 completely outward from the annular end surface of the needle bearing 34. It shifts and repeats the behavior which returns to the inside of the needle bearing 34 again.

At this time, only the end surface 31c of the drive arm which continues to overlap with the annular end surface of the needle bearing 34 protrudes toward the needle bearing 34 side rather than the end surface of the boss part 19. In the case where the needle bearing 34 moves in the disengaging direction due to the change in the eccentric direction of the harmonic ring 32, as shown in Fig. 3, the end face (which always protrudes near the end face of the needle bearing 34) ( 31c), the ring-shaped end face of the needle bearing 34 faces any part of the end face 31c, and the behavior of the needle bearing 34 in the disengaging direction is restricted. This suppresses unnecessary movement of the needle bearing 34 so that the harmonic ring 32 can always be well bearing.

Although the end of the needle bearing 34 protrudes toward the cam lobe 16 even though it is minute, as shown in FIG. 3, the end of the needle bearing 34 is simply in contact with the protruding end face 31c. The movement is restricted rather than contacting the corner portion 19c of the end face of the boss portion 19 at the point withdrawn from the side surface 31c. Therefore, abnormal wear is prevented.

Therefore, the needle bearing 34, the harmonic ring 32, and the eccentric shaft 33 have a simple structure that does not require machining, thereby suppressing the movement of the needle bearing 34 in the disengagement direction and end of the needle bearing 34. And interference between the boss portion 19 of the cam lobe 16 can be prevented. The protruding end face 31c is simply formed by increasing the thickness dimension of the drive arm 31, more specifically the thickness dimension of the fixing ring 31a, which enables a particularly simple structure.

Since no load is applied to the needle bearing 34 from the outside, it is possible to employ the needle 34a of the maximum length inside the confined space between the harmonic ring 32 and the eccentric shaft 33. As a result, the supporting strength of the harmonic ring 32 can be secured sufficiently.

In addition, the present invention is not limited to the above-described embodiment. Various changes may be made without departing from the spirit of the invention. For example, in one embodiment, the width dimension of the anchoring ring was increased to protrude an end face that continues to overlap with the end face of the bearing portion. Needless to say, however, it is also possible to design the end face to extend from the anchoring ring to the arm part and to increase the width dimension of the same part so as to protrude the end face which continues to overlap with the end face of the bearing part. In one embodiment, needle bearings are used as bearings, although other bearings such as sliding bearings may be used. One embodiment has a structure in which an eccentric rotational variable valve gear is installed on the intake side of an engine, and the present invention is employed in such a gear. However, the present invention can also be applied to an eccentric rotary variable valve gear provided on the exhaust side of the engine.

Claims (3)

A cylinder head having an intake or exhaust valve, A cam drive shaft rotatably supported by the cylinder head; A cam lobe rotatably supported by the cam drive shaft and having a cam for driving the valve; A drive arm fixed adjacent to one end of the cam lobe in the cam drive shaft, the cam drive shaft being rotatably supported at a position opposite the cam lobe with respect to the drive arm and eccentric with the axis of the cam drive shaft An eccentric shaft member having an outer circumferential surface that is adjustable and an intermediate rotator member rotatably supported through a bearing member and connected to the drive arm around an outer circumferential surface of the eccentric shaft member, wherein the drive arm and the intermediate rotation member And a variable valve mechanism for transmitting a rotation of the cam drive shaft to the cam lobe through and adjusting the eccentricity of the eccentric shaft member to vary the valve opening period of the valve. The drive arm has an end face that overlaps with the end face of the bearing member when projecting along the axis of the cam drive shaft, regardless of the rotational position of the drive arm relative to the chamfer shaft member, the end face of the drive arm being A variable valve gear for an internal combustion engine protruding more toward the bearing member than the end face of the cam lobe. The driving arm of claim 1, wherein the driving arm has a fixed ring fixed to the cam drive shaft and an arm portion extending from an outer circumference of the fixed ring in a radially outward direction and transmitting torque to the intermediate rotating member, The bearing side end face of the stationary ring overlaps with the end face of the bearing member at the drive arm. 3. The cam lobe of claim 2, wherein the cam lobe has a boss portion to which the torque of the intermediate rotating member is transmitted at a point shifted from the axis of the cam lobe and extends toward the intermediate rotating member, The cam lobe is in contact with the cam lobe end surface of the stationary ring of the drive arm and has a contact surface that determines the axial position of the cam lobe relative to the drive arm, And the fixed ring of the drive arm has an axial length longer than the axial length between the contact surface of the cam lobe and the tip side surface of the boss portion.