JPS63189607A - Intake and exhaust valve timing device for internal combustion engine - Google Patents

Abstract

PURPOSE:To intend to reduce vibration and noise by providing an inverted cam which rotates circumscribing to an integral excentric cam on a crank shaft for making an intake and exhaust valve open and close following to inverted cam face. CONSTITUTION:An inverted cam 17 is cercumscrived on inner periphery face 18, 19 of its hollow portion to eccentric cams 15, 16 integral with a center axis line Co of a crank shaft 6 for bearing the inverted cam 17 freely rotatable. Cam face 20 on outer periphery face of the inverted cam 17 is abutted to cam followers 21, 22 that open and close an intake and exhaust valve 28. The eccentric cams 15, 16 press mutually opposed faces of the inverted cam 17 alternately. According to this, it can be down to make operation smooth and to reduce vibration and noise.

Description

Detailed Description of the Invention A0 Object of the Invention (1) Industrial Application Field The present invention provides an eccentric cam that rotates integrally with a crankshaft.
The driven cam is rotated at a speed of one-half of the rotational speed of the crankshaft while the mutually opposing surfaces on the inner circumferential surfaces forming the hollow part of the driven cam eccentric to the crankshaft are always in circumscription. The present invention relates to an intake/exhaust valve timing actuation device for an internal combustion engine in which a cam follower moves to open/close the intake/exhaust valves by following a cam surface on the outer peripheral surface of the cam.

(2) Conventional technology In intake/exhaust valve operating devices driven by a crankshaft, the use of a gear or chain transmission mechanism is avoided, and the output shaft connected to the crankshaft is rotated twice. JP-A-59-150912 or JP-A-61-229906 discloses a valve mechanism in which a guide part shaped to return to the original position is formed, and an interlocking mechanism guided by the guide part opens and closes the valve mechanism. It is stated in the No.

(3) Problems to be Solved by the Invention In the conventional intake/exhaust valve actuating device described above, the shape of the guide part is complicated, and the shape is such that it returns to the original position after two rotations, so the axis of the crankshaft This requires a large amount of space in both directions, and the interlocking mechanism guided by the guide section is also forced to make complex three-dimensional movements.

As a result, the structure of the intake/exhaust valve actuating device as a whole becomes complicated, it is not easy to miniaturize it, and the moving parts are subject to wear. The main object of the present invention is to obtain an intake/exhaust valve timing actuation device for an internal combustion engine that generates little noise and can be easily miniaturized.

B0 Structure of the Invention (1) Means for Solving Problems According to the present invention, the crankshaft has a central axis eccentric from the central axis of the crankshaft and is integrated with the crankshaft around the central axis of the crankshaft. A rotating eccentric cam is rotatably supported eccentrically with an eccentricity equal to the eccentricity of the eccentric cam with respect to the crankshaft, and on the inner circumferential surface forming a hollow part, there is constantly a a driven cam having mutually opposing surfaces that rotate while circumscribing the eccentric cam while sandwiching the eccentric cam; and a cam surface on the outer peripheral surface of the driven cam to open and close intake and exhaust valves. There is obtained an intake/exhaust valve timing actuating device for an internal combustion engine, which is characterized in that it is equipped with a cam follower that performs a movement for.

(2) Function Among the pair of circumscribed lines between the mutually opposing surfaces forming the hollow portion of the driven cam and the eccentric cam corresponding to this opposing surface, the distance from the central axis of the crankshaft increases as the crankshaft rotates. On the increasing circumferential line, as the crankshaft rotates, the eccentric cam exerts a pressing force on the opposing surface of the driven cam, and this pressing force applies a torque corresponding to the amount of eccentricity of the eccentric cam to the driven cam. It will be given to In this way, the eccentric cams alternately press the mutually opposing surfaces of the driven cams, so that during one revolution of the crankshaft, the driven cams turn half a turn, and the driven cams are decelerated and sucked into and exhausted from the cam driven body. Make movements to open and close the valve.

(3) Examples An embodiment of the present invention will be described below with reference to the drawings.

In FIGS. 1 and 2, a small end of a connecting rod 5 is pivotally supported via a piston pin 4 to a piston 3 that slides into a cylinder bore 2 formed in a cylinder block 1. The large end of 5 is pivotally supported by a crank pin of a crank 7 that rotates integrally with the crankshaft 6. The crankshaft 6 is rotatably supported by the cylinder block 1 via bearings 8, 9 and seals 10.11,
A flywheel 1 with a cooling fan 12' is attached to one end thereof.
2 is attached, and a clutch plate 13 is attached to the other end.

A pair of eccentric cams 15.16 are mounted on the crankshaft 6 between the bearing 9 and the cover plate 14 so as to rotate together with the crankshaft 6.
The driven cam 17 circumscribing the cylinder block 1 and the cover plate 1 is eccentrically moved toward the piston 3 by an eccentric amount e equal to the eccentric amount e of the eccentric cam 15 and 16 relative to the crankshaft 6.
4, it is rotatably supported.

The end surfaces of intake and exhaust cam followers 21 and 22 are in contact with the cam surfaces 20+ and 208 on the outer peripheral surface of the driven cam 17,
The axial movement of the cam followers 21.22 actuated by the follower cam 17 is effected by the rocker arm 2 pivoting about the spherical pivot 25 via bushing rods 23.24, respectively.
6.27. As a result, the rocker arm 26 presses the valve shaft 29 of the intake valve 28 against the spring force of the compression spring 36 interposed between the spring seat 32 and the shoulder 33 on the cylinder head side. 28, and the rocker arm 27 presses the valve shaft 31 of the exhaust valve 30 against the spring force of a compression spring 37 interposed between the spring seat 34 and the shoulder 35 on the cylinder head side. By doing so, the valve 30 is opened and closed.

The eccentric cams 15, 16 and the driven cams 17 will be explained in more detail below.

As shown in FIGS. 3 and 4, each eccentric cam 1
5.16 has a cylindrical outer circumferential surface with a circular cross section, and is eccentric by an eccentric amount e from the central axis Co of the crankshaft 6 in opposite directions when viewed in the diametrical direction of the crankshaft 6.

Corresponding to the position of each eccentric cam 15, 16, the crankshaft 6
A central axis C1 eccentric by an eccentric amount e from the central axis C0 of
The inner circumferential surface 18. which forms the hollow part of the driven cam 17.
19 surrounds the outer peripheral surface of the eccentric cam 15,16.

The inner circumferential surface 18 has a pair of mutually parallel opposing surface portions 181.18t that rotate while circumscribing the eccentric cam 15 while always sandwiching the eccentric cam 15 as the crankshaft 6 rotates, and the inner circumferential surface 19 are a pair of mutually parallel opposing surface portions 191 and 19 that rotate while circumscribing the eccentric cam 16 while always sandwiching the eccentric cam 16 as the crankshaft 6 rotates.
g, and each opposing surface portion IL, 182 of the inner circumferential surface 18 and each opposing surface portion IL, 19g of the inner circumferential surface 19 are formed with a phase shift of 90'' from each other.

In Fig. 3 (al) and Fig. 4 (8), the eccentric cam 15
is in a downwardly eccentric state, the opposing surface portion 181
．． 182 extends in the vertical direction, and in this case, the eccentric cam 1
6 is eccentric upward and facing surface portions 19t, 19
g extends horizontally.

When the crankshaft 6 rotates in the direction of the arrow r in this state, the outer tangent line on the side where the distance from the central axis C0 of the drive shaft increases among the pair of outer tangent lines between each pair of opposing surfaces and each eccentric cam , each eccentric cam 15 , 16 presses against the opposing surface and transmits torque to the driven cam 17 . That is, the eccentric cam 15 presses the opposing surface portion 181 and the eccentric cam 16 presses the opposing surface portion 191. As a result, when the rotation of the eccentric cams 15 and 16 has progressed by 90 degrees, the third
Figure 4), the rotation of the driven cam 17 is 4 as shown in Figure 4 (b).
Go forward 5 degrees. The eccentric cam 15 further includes a facing surface portion 18 . While continuing to press , the eccentric cam 16 continues to press the opposing surface portion 181,
When the rotation of the eccentric cam 15.16 progresses by 180'', as shown in Fig. 3 (
C), the rotation of the driven cam 17 is 90 as shown in Fig. 4 (C).
At this point, further rotation of the eccentric cam 15. At the same time as the eccentric cam 16 starts to push the opposing surface portion 19I. When the rotation of the eccentric cams is further progresses to 270@, the driven cam 17 rotates by 135'' as shown in FIG. 3 16) and FIG. 3 td).

In the present invention, each eccentric cam 15.16 may be molded integrally with the crankshaft 6, or each eccentric cam 15.16 may be formed integrally with the crankshaft 6.
Alternatively, it may be formed separately from the crankshaft 6 and then fixed onto the crankshaft 6. If a pair of eccentric cams are arranged on the crankshaft with the eccentric directions shifted by 1800 degrees as shown in the figure, the torque will be transmitted smoothly to the driven cam and the generation of vibration will be suppressed. It is also possible to arrange one or more eccentric cams on the crankshaft. Furthermore, if the pair of opposing surfaces rotate while circumscribing the eccentric cam with the eccentric cam sandwiched between them as the crankshaft rotates, the cross-sectional shape of the outer peripheral surface of the eccentric cam 15, 16 is a perfect circle. It is not necessary, and the pair of opposing surface portions do not necessarily need to be plane portions parallel to each other. However, if the cross-sectional shape of the outer circumferential surface of the eccentric cam 15, 16 is circular as in the embodiment, and the pair of opposing surfaces are parallel plane parts, the parts can be easily machined, and the driven cam 17 can be easily machined. There is an advantage that rotation is also carried out smoothly.

Further, the present invention can be applied to a side valve type internal combustion engine, and the cam follower is directly inhaled.

It may also be configured to operate an exhaust valve.

C1 Effects of the Invention As described above, according to the present invention, the eccentric cam rotates integrally with the crankshaft, and the eccentric cam is eccentric with an eccentric amount equal to the eccentric amount of the eccentric cam. The timing mechanism is composed of a driven cam that has a pair of opposing surfaces that rotate at the same time, so the structure is simple with few parts, the operation is smooth, and the internal combustion engine is lightweight and compact with little vibration and noise. A timing actuation device for engine intake and exhaust valves can be obtained. Furthermore, if the driven cam is eccentrically moved from the central axis of the crankshaft toward the piston side, the driven cam can be brought closer to the suction and exhaust valve by an amount commensurate with the amount of eccentricity, and the length of the motion transmission mechanism can be reduced accordingly. This can further contribute to reducing the weight and size of the entire device.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view of main parts showing an example of an internal combustion engine equipped with an intake and exhaust valve timing actuation device according to an embodiment of the present invention;
The figure is a cross-sectional view of the main part taken along the line nn in Figure 1.
The diagrams (al to Td) show the relationship between the first eccentric cam and the driven cam in sequence in response to changes in the rotation angle of the crankshaft.
A cross-sectional view of the main part along the line III-III in the figure, Fig.
) ~ (d+ is I in Figure 1, which sequentially shows the relationship between the second eccentric cam and the driven cam in response to changes in the rotation angle of the crankshaft.
It is a cross-sectional view of the main part along the V-IV line.

Claims (1)

[Scope of Claims] [1] The crankshaft (6) has a center axis eccentric from the center axis (C_0) of the crankshaft (6), and the crankshaft (6) is arranged around the center axis (C_0) of the crankshaft (6). Eccentric cams (15, 16) that rotate integrally;
The crankshaft (16) is rotatably supported eccentrically with an eccentricity (e) equal to the eccentricity (e) with respect to the crankshaft (6) of As the shaft (6) rotates, the eccentric cam (15,
16), which rotate while circumscribing the eccentric cams (15, 16);
19_1, 19_2), and a cam surface (20_1) on the outer peripheral surface of this driven cam (17).
, 20_2) for opening and closing the intake and exhaust valves (28, 30). Actuation device. [2] The driven cam (17) is connected to the crankshaft (6)
The intake and exhaust valve timing actuating device for an internal combustion engine according to claim 1, wherein the timing actuating device is eccentric from the central axis (C_0) of the piston (3) toward the piston (3).