TWI393818B - Valve operating system for internal combustion engine - Google Patents

Description

Valve drive for internal combustion engine

The present invention relates to an improvement of a valve driving device for an internal combustion engine having the following members: a decompression cam member supported by a cam shaft having a valve driving cam and moving in a compression stroke of the engine An actuating position for actuating the exhaust valve actuating member toward the opening direction of the exhaust valve and a non-actuating position of the "liberating exhaust valve actuating member"; and an exhaust returning cam member, the exhaust recirculating cam member being The actuating position of the camshaft supported by the "actuating member of the exhaust valve actuating member" and the "actuating member of the exhaust valve of the engine in the opening direction of the exhaust valve" And a centrifugal mechanism that is mounted on a driven sequential rotating member that is driven by the crank shaft and rotates integrally with the valve driving cam, so that the decompression cam member can be in the starting rotation region of the engine The actuating position, the inactive position after starting, and the actuation of the exhaust return cam member in the low-speed operating region of the engine and the high-speed operating region Set actuation.

The valve driving device of the internal combustion engine is known to the public as disclosed in Patent Document 1 below.

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2005-240793

The valve driving device of the conventional internal combustion engine engine is connected to the driven timing rotating member by a cam shaft having an exhaust cam and an intake cam, and the reduced pressure cam member and the exhaust returning cam member supported by the cam shaft Between the driven timing rotating member and the exhaust cam, it is necessary to ensure sufficient space for the driven timing rotating member and the exhaust cam between the driven timing rotating member and the exhaust cam. The valve drive is miniaturized.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a valve driving device that can form a compact internal combustion engine engine regardless of the arrangement of the driven timing rotating member and the exhaust cam.

In order to achieve the above object, the present invention is a valve driving device for an internal combustion engine having a member: a decompression cam member supported by a cam shaft having a valve driving cam, and in a compression stroke of the engine, Actuating a position in which the exhaust valve actuating member is actuated in the opening direction of the exhaust valve and a non-actuating position of the "liberating exhaust valve moving valve member"; and an exhaust returning cam member that is The actuating position of the camshaft supported by the "actuating member of the exhaust valve actuating member" and the "actuating member of the exhaust valve of the engine in the opening direction of the exhaust valve" And a centrifugal mechanism that is mounted on a driven sequential rotating member that is driven by the crank shaft and rotates integrally with the valve driving cam, so that the decompression cam member can be in the starting rotation region of the engine Actuation position and non-actuation position after starting, and the exhaust gas recirculation cam member is in a non-actuated position in the low speed operation region of the engine and in the high speed operation region The first position is that the valve driving cam is provided with a recess that surrounds the cam shaft and forms an opening on the other side of the driven timing rotating member and the base surface of the valve driving cam, and the decompression cam The member and the exhaust gas recirculation cam member are housed in the recess. The intake valve actuating member and the exhaust valve actuating member respectively correspond to the intake rocker arm 29i and the exhaust rocker arm 29e in the embodiment of the present invention to be described later, and further, the slave sequential time-rotating member corresponds to Drive timing pulley 32.

Further, in addition to the first feature, the present invention has a second feature of "a valve drive cam is fitted and fixed to a cam shaft that is different from the valve drive cam".

In addition to the first feature, the present invention has the following features as a third feature. The centrifugal mechanism is configured by a first centrifugal weight that is a driven sequential rotating member. The shaft is pivoted from the retracted position toward the intermediate expanded position corresponding to an increase in centrifugal force, and prevents further shaking; and the second centrifugal weight is subjected to the same driven sequential rotating member by the second centrifugal weight The shaft branch is swung from the retracted position toward the intermediate expanded position together with the first centrifugal weight corresponding to the increase of the centrifugal force, and is separated by the increase of the centrifugal force after the first centrifugal weight stops at the intermediate expansion position. And a return spring that is between the second centrifugal weight and the driven timing rotating member, and pushes the second centrifugal weight toward the retracted position side; the second centrifugal weight is interlocked Connected to the decompression cam member and the exhaust recirculation cam member, when the second centrifugal weight occupies the retracted position, the decompression cam member is controlled to the actuating position, and the exhaust recirculation cam member is controlled to be inactive Further, when the second centrifugal weight occupies the intermediate expansion position, the decompression cam member and the exhaust gas return cam member are controlled together in the non-actuated position, and not only when the second centrifugal weight occupies the expansion position, The decompression cam member is controlled to the non-actuated position and controls the exhaust recirculation cam member to the actuating position.

In addition to the above description, in addition to the third feature, the present invention has the following portion as the fourth feature, in which the intake valve actuating member and the exhaust valve actuating member are shifted from each other and are slidably coupled to the outer peripheral surface of the valve drive cam. .

According to the first aspect of the present invention, the decompression cam member and the exhaust return cam member can be tightly housed in the valve drive cam, and the valve drive device can be downsized.

According to the second aspect of the present invention, by integrally configuring the valve drive cam and the camshaft, the recessed portion can be formed on the valve drive cam without being hindered by the camshaft, and the cost of the valve drive device can be reduced.

According to the third aspect of the present invention, the decompression cam member and the row can be easily and surely achieved by setting the contraction position and the intermediate expansion position of the first and second centrifugal weights and the expansion position of the second centrifugal weight. The timing of actuation of the air return cam member.

According to the fourth aspect of the present invention, the opening and closing of the intake and exhaust valves can be performed by the common one valve driving cam, and the valve driving device can be further downsized.

Hereinafter, embodiments of the present invention will be described based on preferred embodiments of the invention shown in the drawings.

[Example 1]

First, in Fig. 1, the engine body 1 of the internal combustion engine E is constituted by a crank case 2 which is an inclined surface that obliquely intersects the crank shaft 6, and bolts the first case half. 2a and the second tank half 2b; and the cylinder block 3, which extends upward from the second tank half 2b; and the cylinder head 4, which is integrally formed in the cylinder cylinder The upper end of the body 3. In the crank case 2, a crank shaft 6 supported by the left and right side walls thereof is housed, and the crank shaft 6 is connected to a piston 7 fitted in a cylinder bore 3a of the cylinder block 3 via a connecting rod 8. On one side of the engine body 1, a conventional kickback starter 13 for cranking the crank shaft 6 is attached.

In the first and second figures, the cylinder head 4 is formed with a combustion chamber 15 connected to the cylinder bore 3a and an intake port 16i and an exhaust port 16e whose inner end is open to the combustion chamber 15, and is provided for use. The intake valve 17i and the exhaust valve 17e that open and close the intake port 16i and the exhaust port 16e are attached and fixed to the intake and exhaust valves 17i and 17e, respectively, and are respectively pushed in the valve closing direction. Intake and exhaust valve springs 30i, 30e. The valve driving device 20 that drives the intake valve 17i and the exhaust valve 17e to open and close by the common operation with the valve springs 30i and 30e is disposed from the crankcase 2 to the cylinder head 4. The valve drive unit 20 will be described in detail later.

On the cylinder head 4, the spark plug 21 of the "electrode facing the combustion chamber 15" is also rotatably fixed, and not only the carburetor 22 and the row respectively connected to the outer ends of the intake port 16i and the exhaust port 16e are attached. The air muffler 23 is attached and fixed to the air inlet of the carburetor 22 with an air cleaner 19.

Further, the crankcase 2 is attached to the upper portion with a fuel tank 24 adjacent to the carburetor 22 and the exhaust muffler 23.

Next, the valve driving device 20 will be described.

As shown in FIGS. 1 to 3, the cylinder block 3 to the cylinder head 4 are formed with a valve chamber 20a extending upward from the inside of the crank case 2 and adjacent to one of the cylinder bores 3a. A valve driving device 20 is disposed in the dynamic valve chamber 20a. The valve driving device 20 includes a support shaft 27 that is disposed in parallel with the crank shaft 6 and traverses an upper portion of the overrun valve chamber 20a, and a hollow cylindrical cam shaft 26 that is hollow cylindrical The cam shaft 26 is rotatably supported by the support shaft 27. The support shaft 27 is fixed to the cylinder head 4 by fitting the both ends to the pair of branch holes 28 and 28 of the "opposing side wall of the valve chamber 20a", and is fixed by the bolt 51. The pressure plate 52 on the outer side of the cylinder head 4 presses the outer end portion of the support shaft 27.

As shown in FIGS. 3 to 6, the single valve drive cam 25 is fitted and fixed to the outer circumference of one end portion of the cam shaft 26 by press fitting or the like. At one end of the valve drive cam 25, a driven timing pulley 32 "around the other end of the cam shaft 26" is integrally formed, and the driven timing pulley 32 is formed from the drive timing pulley 31 fixed to the crank shaft 6. It is driven by the timing belt 33 at a reduction ratio of one-half.

The cylinder head 4 is provided with an intake swing shaft 34i and an exhaust swing shaft 34e that are parallel to the "cam shafts 26 disposed on both sides of the intake and exhaust valves 17i, 17e", and are connected to the valve drive cam 25 and the intake air. The intake rocker arm 29i between the valves 17i is rotatably supported by the intake rocker shaft 34i, and the exhaust rocker arm 29e connected between the valve drive cam 25 and the exhaust valve 17e is freely rockable. The ground is supported by the above-described exhaust rocking shaft 34e. The above-described intake and exhaust rocker arms 29i and 29e are subjected to the rise of the valve drive cam 25 at a specific timing by making the contact phases with the valve drive cam 25 different from each other, and utilizing and intake air. The intake and exhaust valves 17i and 17e are opened and closed, respectively, in cooperation with the exhaust valve springs 30i and 30e.

The valve driving device 20 is configured as described above, and the head cover 18 that covers the valve driving device 20 from above is joined to the upper end surface of the cylinder head 4.

As shown in FIGS. 4 to 6, the driven timing pulley 32 is formed by an arm wall 32a which is radially expanded from one end portion of the valve driving cam 25, and a ring gear 32b. The ring gear 32b is formed on the outer circumference of the arm wall 32a, and is supported by the first pivot 36 which is fixed to the arm wall 32a and protrudes from the outer side surface thereof, and supports the first and the first "formed slightly U-shaped" Each of the end portions of the centrifugal weights 351 and 352 is rotatably supported to surround the half circumference of the cam shaft 26. Each of the first and second centrifugal weights 351 and 352 has a plate shape and overlaps each other. The first centrifugal weight 351 is formed at a rocking end opposite to the pivot shaft 36 to form a rocking end for the second centrifugal weight 352. The abutting tab 351a.

The first centrifugal weight 351 is a retracted position A around the pivot 36 from the "outer circumferential surface of the spacer ring 49 on which the U-shaped bent portion abuts on the cam shaft 26" (please refer to FIG. 5). The rocking direction is shifted toward the intermediate expansion position M (refer to FIG. 10) of the "contact piece 351a contacting the outer circumferential surface of the spacer ring 49", and the shaking beyond the intermediate expansion position M is not formed. Further, the second centrifugal weight 352 is formed so as to be swung from the contraction position A to the expansion position B via the intermediate operation position M around the pivot shaft 36, and the contraction position A of the second centrifugal weight 352 (refer to FIG. 5) The first centrifugal weight 351 is located at the contraction position A, and the rocking end of the second weight 352 is brought into contact with the abutting piece 351a; the intermediate centrifugal position 352 of the second centrifugal weight 352 is defined. (Refer to Fig. 10) It is defined that when the first centrifugal weight 351 is at the intermediate expansion position M, the rocking end of the second centrifugal weight 352 is brought into contact with the contact piece 351a; The expansion position B of the centrifugal weight 352 (refer to FIG. 11) is defined by the following method: when the first centrifugal weight 351 is restrained at the intermediate expansion position M, the second centrifugal weight 352 is abutted The sheet 351a is separated from the specific distance and abuts against the stopper piece 351b of "the side edge formed on the opposite side of the first centrifugal weight 351 on the opposite side of the contact piece 351a". Then, the return spring 43 that "pushes the second centrifugal weight 352 to the contraction position A side with a specific preload" is stretched over the locking claw 40 of the second centrifugal weight 352 and the arm wall 32a. Between the locking pins 41. The first centrifugal weight 351, the second centrifugal weight 352, and the return spring 43 described above constitute a centrifugal mechanism 46 that drives the drive ring 45 to be described later.

As shown in FIG. 3 and FIG. 7 to FIG. 9, the valve drive cam 25 is provided with a circular outer surface surrounding the cam shaft 26 and facing the driven timing timing pulley 32 and the base circular surface of the valve drive cam 25. A recess 39 of the opening 25a, in which the camshaft 26 is mounted on the cam shaft 26 from the side of the valve drive cam 25, and is sequentially fitted with an exhaust gas recirculation cam member 48, a decompression cam member 47, a drive ring 45, and a separation distance. Ring 49. Accordingly, the exhaust return cam member 48, the decompression cam member 47, and the drive ring 45 can all be accommodated in the recess 39 of the valve drive cam 25.

In the third and fifth to ninth drawings, the drive ring 45 is a member that is rotatably fitted to the outer peripheral surface of the cam shaft 26, and the drive ring 45 is integrally formed with a protrusion from the outer peripheral surface thereof. And extending to the connection protrusion 45a on the side of the first and second centrifugal weights 351 and 352, the coupling protrusion 45a is engaged with the connection groove 352a provided in the inner circumference of the rocking end of the second centrifugal weight 352. When the second centrifugal weight 352 is rocked in the radial direction, the driving projection 45 is urged to rotate by the coupling projection 45a. Further, the drive ring 45 has an axially-retaining groove 45b on its inner peripheral surface, and the roller 44 extending in the axial direction of the cam shaft 26 is held by the driven timing pulley 32 and the valve drive by the holding groove 45b. Between the cams 26e. The roller 44 is rotatable on the outer peripheral surface of the cam shaft 26 by relative rotation with the cam shaft 26 of the drive ring 45.

In the seventh to eleventh drawings, the decompression cam member 47 and the exhaust gas recirculation cam member 48 are slidably fitted along the diameter line of the cam shaft 26: they are formed on both side faces of the cam shaft 26, and are mutually A pair of parallel guiding faces 55, 55. In this way, the decompression cam member 47 can slide between the actuating position C (Fig. 8) and the non-actuating position D (Fig. 10) along the guiding faces 55, 55, the actuating position C and the inactive position D is defined by the following manner: the inner end faces 56a and 56b of the decompression cam member 47 in the direction orthogonal to the guide faces 55 and 55 abut against the outer peripheral surface of the camshaft 26. Further, the exhaust gas recirculation cam member 48 is slidable along the guide faces 55, 55 between the non-actuated position F (Fig. 7) and the actuating position G (Fig. 11), the actuating position F and the inactive position G It is defined that the inner end faces 57a and 57b of the exhaust gas recirculation cam member 48 in the direction orthogonal to the guide faces 55 and 55 abut against the outer peripheral surface of the camshaft 26.

The decompression cam member 47 and the exhaust gas recirculation cam member 48 integrally have, on their outer peripheral surfaces, convex cams 47a, 48a which are far below the front end of the valve drive cam 25, and these convex cams 47a, 48a are formed At the respective actuation positions C and G, they protrude from the base circular surface 25a of the valve drive cam 25 to the outside, and are retracted to the inner side of the base circular surface 25a at the non-actuated positions D and F. Further, the convex cam 47a of the decompression cam member 47 is configured such that when it occupies the actuation position C, the exhaust rocker arm 29e is lifted up in the compression stroke of the engine, and the convexity of the exhaust gas recirculation cam member 48 is raised. The cam 48a is configured such that when it occupies the actuating position G, the exhaust rocker arm 29e is lifted up in the intake stroke of the engine.

As shown in Fig. 8, a concave cam 58 that cooperates with the roller 44 is formed at a central portion of the inner end surface 56b on the convex cam 47a side of the decompression cam member 47. The concave cam 58 is configured by a slope 58a that is pressed by the roller 44 when the second centrifugal weight 352 is held at the contraction position A by the elastic force of the return spring 43. The decompression cam member 47 is forcibly moved to the operating position C; and the arcuate bottom surface 58b avoids the interference of the roller 44 when the second centrifugal weight 352 is swung to the intermediate expansion position M. The movement of the decompression cam member 47 toward the non-actuated position D is allowed. The decompression cam member 47 is formed such that when its center of gravity is offset from the center of the decompression cam member 47 to the opposite side of the concave cam 58 and the roller 44 comes to the opposite position of the arcuate bottom surface 58b, the decompression cam member 47 will move toward the non-actuated position D by the centrifugal force acting on the above-mentioned center of gravity.

As shown in Fig. 7 and Fig. 11, on the other hand, a concave cam 59 that cooperates with the roller 44 is formed at a central portion of the inner end surface 57b on the side of the convex cam 48a on the exhaust gas return cam member 48. . The concave cam 59 is configured by an arc-shaped bottom surface 59a that avoids rolling between the second centrifugal weight 352 and the intermediate expansion position M from the contraction position A to the intermediate expansion position M. The interference between the sub-ports 44 allows the exhaust gas returning cam member 48 to move toward the non-actuating position F; and the inclined surface 59b which is rotated by the roller when the second centrifugal weight 352 is swung to the expanded position B 44 is pressed to force the exhaust gas return cam member 48 to the actuating position G. The exhaust gas recirculation cam member 48 is formed such that when its center of gravity is offset from the center of the exhaust gas recirculation cam member 48 to the opposite side of the concave cam 59, and the roller 44 is located at the opposite position of the arcuate bottom surface 59a, the exhaust gas is recirculated. The cam member 48 moves toward the non-actuated position G by the centrifugal force acting on the center of gravity.

Next, the action of this embodiment will be described.

When the crankshaft 6 rotates, since the drive timing pulley 31 drives the driven timing pulley 32 through the timing belt 33, the valve drive cam 25 "integrated with the driven timing pulley 32" is also driven to rotate. Next, in the intake stroke, the front end portion of the valve drive cam 25 swings the intake rocker arm 29i to push the intake valve 17i against the spring force of the intake valve spring 30i. Further, in the exhaust stroke, the front end portion of the valve drive cam 25 also swings the exhaust rocker arm 29e in the same manner, and pushes the exhaust valve 17e. The opening and closing timings of the intake valve 17i and the exhaust valve 17e are shown in Fig. 13.

In Fig. 12, in the start rotation area a of the engine "the number of engine revolutions Ne is 0 to a specific number of revolutions Ne1 below the idle rotation number", as shown in Figs. 4, 5, and 8 It is to be noted that the first and second centrifugal weights 351 and 352 are held together at the contraction position A by the preload of the return spring 43. At this time, the drive ring 45 connected to the second centrifugal weight 352 through the connection projection 45a presses the roller 44 against the inclined surface 58a of the concave cam 58 of the decompression cam member 47, so that the decompression cam member 47 is held. The operation position C of "the convex cam 47a protrudes outward from the base circular surface 25a of the valve drive cam 25".

According to this, if the kickback starter 13 that can start the internal combustion engine E is operated in the above state, since the crankshaft 6 is caused to rotate by the starter 13 through the starter shaft 12, it is also driven by the timing belt 33 or the like. The valve driving cam 25 rotates, so that as described above, in the compression stroke of the piston 7, the convex cam 47a of the decompression cam member 47 slightly pushes the exhaust rocker arm 29e slightly, and the exhaust valve 17e is slightly opened. . The timing at this time is shown in Fig. 10. In this way, since a part of the compressed gas in the cylinder bore 3a is discharged toward the exhaust port 16e, the increase in the compression pressure is suppressed, the operating load of the actuator 13 can be reduced, and the crankshaft 6 can be shaken relatively briskly and vigorously. So the engine can be started easily.

After the engine is started, once the engine revolution number Ne rises and leaves the starting rotation region a, as shown in Fig. 10, the periphery around the pivot 36 derived from the total centrifugal force of the first and second centrifugal weights 351, 352 is used. The torque is greater than the torque around the pivot 36 of the first centrifugal weight 351 derived from the preload of the return spring 43, and the first and second centrifugal weights 351, 352 are integrally formed from the retracted position A toward the radial direction. The outer side of the spacer ring 351a of the first centrifugal weight 351 abuts against the outer peripheral surface of the spacer ring 49 on the cam shaft 26, and the first and second centrifugal weights 351 and 352 reach the intermediate expansion together. Position M, and only the first centrifugal weight 351 is prevented from forming a further expansion. In the above-described process, the swing of the second centrifugal weight 352 from the contraction position A to the intermediate expansion position M is transmitted to the coupling projection 45a, and the drive ring 45 is rotated counterclockwise in FIG. 10 to further The roller 44 is moved to a position opposing the bottom surface 58b of the concave cam 58 of the decompression cam member 47. Therefore, the decompression cam member 47 can be moved to the non-actuated position D by the action of the centrifugal force without being obstructed by the roller 44, and the convex cam 47a can be retracted to the inner side of the base circular surface 25a of the valve drive cam 25.

In the above process, the exhaust gas recirculating cam member 48 is as shown in Fig. 7, since the bottom surface 59a of the concave cam 59 is the roller 44 facing the drive ring 45, the exhaust gas recirculation cam member 48 can also be prevented from rolling. The restraint of the sub-44 is held at the non-actuated position F by the centrifugal force, and the convex cam 48a is retracted to the inner side of the base circular surface 25a of the valve drive cam 25.

According to the above description, the exhaust valve 17e can be controlled to open and close only by the original shape of the valve driving cam 25 as usual.

However, once the first centrifugal weight 351 reaches the intermediate expansion position M, since the further expansion shaking is blocked by the cam shaft 26, when the engine revolution Ne rises above Ne1, the second centrifugal weight 352 has not yet passed from the When the contact piece 351a of the centrifugal weight 351 is separated, the load acting on the return spring 43 is constant. Therefore, in the engine speed field Ne1 to Ne2 in which the return spring 43 cannot be deformed only by the centrifugal force of the second centrifugal weight 352, that is, it is formed in the low speed operation region b including the idle speed: the second centrifugal weight 352 is held In the middle expansion position M.

When the engine revolution number Ne forms Ne2 or more, that is, once the high-speed operation region c is entered, the centrifugal force of the second centrifugal weight 352 is sufficiently increased, and the pivot 36 of the second centrifugal weight 352 derived based on the centrifugal force is caused. The surrounding torque is greater than the torque of the second centrifugal weight 352 derived from the load of the return spring 43, so that as shown in Fig. 11, the second centrifugal weight 352 reaches the expansion position B and is driven by the drive ring 45. In the counterclockwise rotation caused by the above-described operation, the roller 44 is pressed against the inclined surface 59b of the concave cam 59 of the exhaust gas recirculation cam member 48, thereby causing the exhaust gas recirculation cam member 48 to overcome the centrifugal force and move to the operating position G. Therefore, the exhaust return cam member 48 is formed such that its convex cam 48a protrudes from the base circular surface 25a of the valve drive cam 25. Therefore, as described above, in the intake stroke of the piston 7, the exhaust rocker arm 29e is slightly pushed up by the convex cam 48a of the exhaust gas recirculation cam member 48, and the exhaust valve 17e can be slightly opened. In this way, the exhaust gas remaining in the exhaust port 16e can be introduced into the combustion chamber 15, that is, the reflux of the exhaust gas is performed. In the expansion stroke of the latter stage, the exhaust gas can suppress the excessive rise of the combustion temperature when the mixed gas is burned, reduce the NOx concentration in the exhaust gas, and can help to improve the low fuel economy as the HC concentration decreases. .

As described above, the common drive ring 45 can be actuated by the centrifugal mechanism 46 formed by the first and second centrifugal weights 351 and 352 and the return spring 43, and the decompression cam member 47 and the row can be arranged. The gas return cam member 48 is sequentially operated, and the valve drive device 20 having the "decompression function and the exhaust gas recirculation function that does not interfere with each other and having the desired characteristics" can be simplified and reduced in size.

In addition, since the centrifugal mechanism 46 is attached to the outer surface of the driven timing pulley 32, the decompression cam member 47 and the exhaust return cam member 48 are housed in the "valve driving cam 25 integrally formed on the driven timing pulley 32". The recess 39 is supported by the cam shaft 26, so that the decompression cam member 47 and the exhaust return cam member 48 can be tightly received in the valve drive cam 25 to achieve further miniaturization of the valve drive unit 20.

Further, in the centrifugal mechanism 46, the contraction position A and the intermediate expansion position M of the first and second centrifugal weights 351 and 352 and the expansion position B of the second centrifugal weight 352 can be easily and surely set. The timing of the operation of the decompression cam member 47 and the exhaust recirculation cam member 48 is achieved.

In addition, the intake rocker arm 29i and the exhaust rocker arm 29e, which are respectively used to perform the opening and closing of the intake valve 17i and the exhaust valve 17e, are shifted from each other and are slidably coupled to the outer peripheral surface of the valve drive cam 25, Further, opening and closing of the intake and exhaust valves 17i and 17e can be performed by one common valve drive cam 25, and further miniaturization of the valve drive unit 20 can be achieved.

The present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the scope of the invention. For example, the valve drive cam 25 and the camshaft 26 may also be integrally formed as a single piece. It is also possible to abolish the stopper piece 351b for restricting the expansion position B of the second centrifugal weight 352 by abutting the roller 44 against the side wall 58b side end wall of the concave cam 58 of the decompression cam member 47. The expansion position B of the second centrifugal weight 352 is restricted.

Further, in the case where the present invention is applied to a valve drive device that "provides an intake cam and an exhaust cam on the cam shaft 26", it is only necessary to accommodate the decompression cam member 47 and the exhaust return cam member 48. It is sufficient to approach the cam of the driven timing pulley 32. Further, the time-varying transmission formed by the drive timing pulley 31, the driven timing pulley 32, and the timing belt 33 may also constitute a gear type. In this case, the driven sequential rotation member of the present invention is constituted by a driven timing gear.

E. . . Internal combustion engine

A. . . Contraction position of the first and second centrifugal weights

M. . . Intermediate expansion position of the first and second centrifugal weights

B. . . Expansion position of the second centrifugal weight

C. . . Operating position of the decompression cam member

D. . . Unactuated position of the decompression cam member

F. . . Inactive position of the exhaust return cam member

G. . . Exhaust return cam member actuation position

6. . . Crankshaft

17e. . . Vent

20. . . Valve drive

25. . . Valve drive cam

26. . . Camshaft

29i. . . Intake valve actuating member (intake rocker arm)

29e. . . Exhaust valve actuating member (exhaust rocker arm)

32. . . Driven rotating member (driven timing pulley)

351. . . 1st centrifugal weight

352. . . 2nd centrifugal weight

39. . . Concave

43. . . Return spring

46. . . Centrifugal mechanism

47. . . Decompression cam member

48. . . Exhaust return cam member

Fig. 1 is a longitudinal sectional front view showing an important part of an internal combustion engine having a valve driving device in an embodiment of the present invention. (First embodiment)

Fig. 2 is a cross-sectional view taken along line 2-2 of Fig. 1. (First embodiment)

Fig. 3 is an enlarged view of the place indicated by the figure 3 in Fig. 1. (First embodiment)

Figure 4: A view in the direction indicated by Figure 4 in Figure 2. (First embodiment)

Figure 5: A view in the direction indicated by Figure 5 in Figure 3. (First embodiment)

Fig. 6 is an exploded perspective view of the main part of the above valve driving device. (First embodiment)

Fig. 7 is a sectional view taken on line 7-7 of Fig. 3. (First embodiment)

Fig. 8 is a sectional view taken on line 8-8 of Fig. 3. (First embodiment)

Figure 9 is a sectional view of line 9-9 in Figure 3. (First embodiment)

Fig. 10 is a view showing the action of the valve driving device for releasing the decompression and stopping the exhaust gas. (First embodiment)

Fig. 11 is a view showing the action of the valve driving device for displaying the exhaust gas recirculation state. (First embodiment)

Fig. 12 is a line diagram showing the field of actuation of the decompression cam member and the exhaust recirculation cam member. (First embodiment)

Fig. 13 is a line diagram showing the relationship between the rotation angle of the crankshaft and the opening and closing timing of the intake valve and the exhaust valve. (First embodiment)

4. . . Cylinder head

20. . . Valve drive

25. . . Valve drive cam

25a. . . Base circle

26. . . Camshaft

27. . . Support shaft

28. . . Branch hole

29e. . . Exhaust valve actuating member (exhaust rocker arm)

29i. . . Intake valve actuating member (intake rocker arm)

32. . . Driven rotating member (driven timing pulley)

32a. . . Arm wall

32b. . . Tooth ring

36. . . Pivot

39. . . Concave

40. . . Claw claw

43. . . Return spring

44. . . Roller

45. . . Drive ring

45a. . . Connecting protrusion

45b. . . Keep the ditch

46. . . Centrifugal mechanism

47(C). . . Decompression cam member (actuation position)

47a. . . Convex cam

48(F). . . Exhaust return cam member (no moving position)

49. . . Spacing ring

351. . . 1st centrifugal weight

352. . . 2nd centrifugal weight

352a. . . Connecting groove

Claims (3)

A valve driving device for an internal combustion engine engine includes: a decompression cam member (47) supported by a cam shaft (26) having a valve driving cam (25) and a compression stroke of the engine The movement position (C) of the exhaust valve actuating member (29e) in the opening direction of the exhaust valve (17e) and the inactive position (D) of the purge valve member (29e) are moved. And an exhaust gas recirculation cam member (48) supported by the cam shaft (26) and in a non-actuated position (F) for liberating the exhaust valve actuating member (29e), and The exhaust valve actuating member (29e) is movable between the actuating position (G) of the opening of the exhaust valve (17e) in the intake stroke of the engine; and the centrifugal mechanism (46), the centrifugal mechanism (46) Is mounted on a driven timing rotating member (32) that is driven by the crank shaft (6) and rotates integrally with the valve driving cam (25), and is used to make the decompression cam member (47) in the engine Actuating the actuating position (C) in the rotating region (a) and the actuating position (D) after starting, and causing the exhaust gas recirculation cam member (48) to be transported at a low speed of the engine The non-actuated position (F) in the transition region (b) and the actuation position (G) in the high-speed operation region (c) are characterized in that: one end portion in the axial direction of the valve drive cam (25) is integrally formed forming There is a driven timing rotating member (32), and the valve driving cam (25) is provided with a recess (39), one end side of the axial direction of the recess (39) is closed by a valve driving cam (25), the recess ( 39) surrounding the camshaft (26) and forming an opening on the side of the valve driving cam (25) and the base circular surface (25a) of the valve driving cam (25) toward the driven timing rotating member (32) The pressing cam member (47) and the exhaust return cam member (48) are housed in the recess (39), and the centrifugal weight (351, 352) of the centrifugal mechanism (46) is pivotally supported by the driven sequential rotating member ( 32), a part of the opening surface of the other side of the recessed portion (39) in the axial direction is closed, and the concave portion (39) is formed on the valve driving cam (25) without being hindered by the cam shaft (26). The valve drive cam (25) is fitted and fixed to a cam shaft (26) different from the individual. The valve driving device for an internal combustion engine according to the first aspect of the invention, wherein the centrifugal mechanism (46) is configured by a first centrifugal weight (351), wherein the first centrifugal weight (351) is The driven timing rotating member (32) is pivoted and corresponding to an increase in centrifugal force, and is swung from the retracted position (A) toward the intermediate expanded position (M), and prevents further shaking; and the second centrifugal weight ( 352), the second centrifugal weight (352) is also axially supported by the driven sequential rotating member (32), and corresponds to the increase of the centrifugal force, and together with the first centrifugal weight (351) from the retracted position (A) ) shaking toward the intermediate expansion position (M) and stopping at the first centrifugal weight (351) After the intermediate expansion position (M), corresponding to the increase of the centrifugal force, the vibration is separately moved toward the expansion position (B); and the return spring (43), the return spring (43) is at the second centrifugal weight (352) Between the driven timing rotating member (32), the second centrifugal weight (352) is pushed to the retracted position (A) side, and the second centrifugal weight (352) is coupled to the decompression cam member (47). The exhaust gas recirculation cam member (48) controls the decompression cam member (47) to the actuating position (D) when the second centrifugal weight (352) occupies the retracted position (A), and exhausts the exhaust cam The member (48) is controlled at the inactive position (F), and further, when the second centrifugal weight (352) occupies the intermediate expanded position (M), the decompression cam member (47) and the exhaust return cam member (48) Controlling the non-actuated position (D, F) together, not only that, when the second centrifugal weight (352) occupies the expanded position (B), the decompression cam member (47) is controlled to the inactive position (D) And the exhaust gas return cam member (48) is controlled to the actuating position (G). The valve driving device for an internal combustion engine according to the second aspect of the invention, wherein the intake valve actuating member (29i) and the exhaust valve actuating member (29e) are in a phase shifted from each other and are slidably coupled to the valve driving cam (25). ) the outer perimeter.