JPS6030408A - Valve actuating device in engine - Google Patents

Abstract

PURPOSE:To maintain engine torque at a high value throughout the whole range of engine rotational speed, by fitting, onto a cam shaft or crankshaft, a pulley composed of a part coupled with the shaft side and a part coupled with the belt side, and by adjusting the relative positions of both parts to adjust the valve timing in accordance with the engine speed. CONSTITUTION:A pulley 4 fitted onto a cam shaft or crankshaft 2 is composed of a first rotary member 7 fixed to the shaft 2 and a second rotary member 8 which is rotated relatively to the first rotary member 7 and coupled to a timing belt. The both rotary members 7, 8 are formed therein with grooves 9, 10 which are gradually shallow radially outwardly and which are crossed together, and a weight 12 is disposed in between the grooves 9, 10. Both rotary members 7, 8 are pressed together by means of a resilient member 13, and the radial position of the weight varys under centrifugal force in accordance with the engine speed so that the relative positions of both rotary members 7, 8 are changed to adjust the relative positions of the crankshaft and the cam shaft, thereby the valve timing is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a valve train for an automobile engine or the like having a function of automatically changing the valve timing of an intake valve.

(b) Prior art - In an f0 type reciprocating engine, the timing of closing the intake valve is set early (see broken line a in Figure 1).
Compared to those with standard valve timing (see the solid line in Figure 1), higher engine torque can be obtained in the low-speed rotation range, but there is a tendency for the torque to drop significantly in the middle and high-speed rotation ranges. be. On the other hand, when the intake valve is set to close at a later date (see dot-dash line C in Figure 1), the torque drop in the middle to high speed range is lower than when the valve timing is standard. Although it is rare, there is a tendency that sufficient torque cannot be obtained in the low speed rotation range. Therefore, in order to obtain high torque over the entire rotational speed range, it is desirable that the valve train for driving the intake valve has a function of advancing or retarding the valve timing in accordance with the rotational speed of the engine.

However, as a prior art related to a valve train developed to meet such demands, the previously filed Utility Application filed in 1973
As shown in No. 6-59075, the timing pulley is installed so that it can freely rotate by a required angle in the circumferential direction with respect to the camshaft. Some devices are equipped with a biasing spring member.In other words, this device was developed based on the fact that the torque required to drive the camshaft increases approximately in proportion to the increase in engine rotational speed. In the high-speed rotation range, the deflection of the spring member increases and the valve timing is automatically retarded.However, with this configuration, the spring member is placed on the camshaft side. In addition to the pulley, the camshaft must also be newly designed, reducing the rate of common parts with standard engines that do not have a retard function, and increasing costs. This method has disadvantages in that it invites upgrades and cannot be easily applied to existing engines.

(c) Purpose of the invention The present invention was made with attention to the above circumstances, and
Engine torque can be maintained at a high value over the entire rotation speed range, and the number of parts is small.
An object of the present invention is to provide a valve train for an engine that is extremely simple in construction and can be easily applied to existing engines.

B) Structure of the Invention In order to achieve the above object, the present invention provides a system in which a transmission member such as a pulley, sprocket or gear constituting a valve train is connected to a first rotating body fixed to a crankshaft or a camshaft; a second rotary body which is provided so as to be movable in the axial direction with respect to the first rotary body and has a transmission element on its outer periphery; a pair of cam grooves formed to become gradually shallower toward the outer end; a weight that is engaged between the two cam grooves and is slidable approximately radially along the two cam grooves; an elastic body that presses both rotating bodies in the direction toward each other and urges the weight toward the inner end side of the cam groove; The outer end of the cam groove of the second rotating body is provided so as to be offset from the outer end of the second rotating body in the rotation advancing direction.

(e) Example Hereinafter, an example of the present invention will be described with reference to FIGS. 2 to 7.

Timing pulleys 3.4 serving as transmission parts are respectively mounted on the crankshaft 1-1 and camshaft 2 of the engine, and a timing belt 5 is stretched between these two pulleys 3.4. arrow
The rotational force in the direction is applied to the pulley 3, belt 5 and pulley 4.
The signal is transmitted to the camshaft 2 via the camshaft 2. Note that the timing pulley 3 on the drive side is a normal one, and is fixed to the crankshaft 1 via a key 6. On the other hand, the timing pulley 4 on the driven side is connected to the first rotating body 7 fixed to the camshaft 2 and the first rotating body 7 fixed to the camshaft 2.
a second rotary body 8 which is provided so as to be movable in the axial direction with respect to the rotary body 7; a pair of cam grooves 9.10 provided on opposing surfaces of both of the rotary bodies 7.8; Cam groove 9.
10, and a wave spring 13, which is an elastic body that presses both the rotating bodies 7 and 8 in the direction toward each other. Said first
The rotating body 7 is composed of a hub 7a that fits on the outer periphery of the end of the camshaft 2, and a disk portion 7b that projects from the outer periphery of the hub 7a. 15 to the camshaft 2. Further, the second rotating body 8 includes a disk portion 8a that is rotatably fitted to the outer periphery of the hub 7a of the first rotating body 7.
and a cylindrical portion 8b integrally formed on the outer periphery of this disc portion 8a.
The outer periphery of the cylindrical portion 8b is provided with a transmission element, that is, teeth 8C with which the timing belt 5 meshes.
is the provision. The cam groove 9 is oval-shaped and is provided in the end surface of the disk portion 7b of the first rotary body 7 in a substantially radial direction, so that one half of the ball 12 can fit into the cam groove 9. 4 Yellow cross section is shaped like a semicircular arc. This cam groove 9 has a slope V from the inner end 9a to the outer end 9b.
It is set so that ζ is shallow. Further, the cam groove 10
is an oval shape provided in a portion of the disc portion 8a of the second rotating body 8 corresponding to the cam groove 9, and has a cross section so that the other half of the ball 12 can fit therein. It is shaped like a semi-circular arc. The cam groove 10 is also set to become gradually shallower from the inner end n: "+i ] Oa toward the outer end 10b.

Note that the directions in which the two cam grooves 9 and 10 are carved are slightly different from each other. In other words, in this embodiment, the cam groove 9
The outer end 9b of the cam groove 10 is set to be deviated from the outer end 10b of the cam groove 10 by a required amount of 11 times in the receiving direction. Note that 16 is a snap ring that locks the wave spring 13. In addition, the cam groove 9.10
A plurality of balls 12 (for example, 3 to 6 sets) are provided at equiangular intervals in the circumferential direction.

With such a configuration, the centrifugal force acting on the ball 12 is small in the low rotational speed range where the rotational speed of the crankshaft 1 and the camshaft 2 is low, so that the ball 12 As shown in the figure, it is held at the inner end 9a, 108 of each cam groove 9.10. That is, since the first rotary body 7 and the second rotary body 8 are biased toward each other by the elastic force of the wave spring 13, the ball 12 is pushed into the two cam grooves 9, 10 by the biasing force. These cam grooves 9 and 10 are designed to become gradually shallower toward the outer ends 9b and 10b. Therefore, the clamping force and the cam groove 9
．． Due to the depth change of 10, a force in the center direction acts on the ball 12, and in a low speed rotation range where the center force overcomes the centrifugal force, the ball 12 moves into the cam groove 9.1.
It will be held at the inner end 9a, 108 part of 0. From this state, the rotational speed of the engine increases and the ball 12
When the centrifugal force acting on the cam groove 9.1 exceeds a certain value, the ball 12 expands the distance between the rotating bodies 7.8 and the cam groove 9.1.
0 toward the outer ends 9b and 10b, and is held at a position that balances the above-mentioned cardiac force. At this time, due to the difference in the inclinations of the two cam grooves 9 and 10 in the rotational direction, the two rotating bodies 7
．． 8, and the valve timing will be delayed by that amount. And, when rotating at the highest speed, the 3rd
As shown in the imaginary line and in FIG.
reaches the outer ends 9b, 10b of the cam grooves 9.10, and the valve timing becomes the most delayed state. and,
When the speed is decelerated from this state, the centrifugal force acting on the ball 12 decreases, and the ball 12 is moved to the inner end 9a by the cardiac force induced by the wave spring 13 described above.
, 10a. FIG. 6 shows the relationship between the crankshaft 10 rotational speed and valve timing in this example, and FIG. 7 shows the difference between valve timing I in the low-speed rotation range and valve timing I in the high-speed rotation range. This is what is shown.

As described above, according to the valve train according to the present invention, the valve timing of the intake valve can be automatically controlled by appropriately selecting the pressing force of the wave spring 13, the shape of the cam groove 9, 10, etc. can. However, as in this embodiment, it is easy to control the valve timing to retard the transition from a low speed rotation range to a high speed rotation range, and in this way, the intake inertia can be utilized. Since the closing timing of the intake valve can be delayed only in the high-speed rotation range where it is possible, the output characteristics in the high-speed rotation range can be effectively improved without deteriorating the performance in the middle and low speed rotation ranges. Moreover, this valve train has a very simple structure with a small number of parts, and can be expected to operate reliably. Moreover, there is no need to perform any special processing on the camshaft 2, etc. Therefore, it is possible to reduce costs by increasing the rate of common parts with standard engines that do not have valve timing control functions, and it can also be easily applied to existing engines by simply replacing the pulley. It has the advantage of being able to

In addition, in the above embodiment, a case was explained in which the shape of the cam groove was set so that the valve timing could be retarded in a high-speed rotation range, but the invention recited in claim 1 is not necessarily limited to such a structure. Of course, it is not possible to
For example, various modifications are possible, such as retarding the valve timing only in the idling operating range, or in the idling operating range and in the high speed rotation range.

Further, in the above embodiments, the case where the transmission member is a timing pulley on the camshaft side has been described, but it goes without saying that the present invention is not limited to such a thing. For example, the present invention can be applied to a pulley on the crankshaft side. You may. Alternatively, instead of a pulley, the present invention can be similarly applied to a sprocket, gear, etc. for tensioning a chain.

Furthermore, the weight is not limited to a ball, but may also be a roller or the like.

(f) Effect Since the present invention has the above-described configuration, it is possible to maintain engine torque at a high value over the entire rotational speed range, and the structure is simple and highly reliable, making it possible to use existing engines etc. Therefore, it is possible to provide a valve train for an engine that can be easily applied to the present invention.

-4. Brief description of the drawings FIG. 1 is an explanatory diagram showing the relationship between the engine, torque, rotation, and smoothness. Figures 2 to 7 show an embodiment of the present invention, in which Figure 2 is a partially cutaway front view, Figure 3 is an enlarged side sectional view showing the main parts, and Figures 4 and 5 are operational views. Explanatory diagram, No. 6
The figure is a characteristic explanatory diagram showing retard characteristics, and FIG. 7 is a diagram showing valve timing.

1... Crankshaft 2... Camshaft 4... Transmission member (timing pulley) 7... First rotating body 8... Second rotating body 9.10... Cam groove 12. ... Weight (ball) 13 ... Elastic body (wave spring) Agent Patent attorney Akazawa-Hiroshi Kaeda side

Claims (2)

[Claims] (1) In a system in which the rotational force of a crankshaft is transmitted to a camshaft for opening and closing intake valves via a pair of transmission members such as pulleys, sprockets, or gears supported by both shafts, at least One transmission member includes a first rotating body fixed to the shaft, and a second rotating body that is movable back and forth in the axial direction with respect to the first rotating body and has a transmission element on the outer periphery. A rotary body, and at least one of the rotary bodies provided on opposing surfaces of the two rotary bodies, which is gradually shallower toward the outer end thereof, is pushed toward each other in a direction to move the weight into the deepened cam groove. and an elastic body that biases the center toward one end, and is configured such that the phases of the two rotating bodies can be mutually changed by outward movement of the weight due to centrifugal force. A valve train for an engine. (2) In a device in which the rotational force of the crankshaft is transmitted to the camshaft for opening and closing the intake valves via a pair of transmission members such as pulleys, sprockets, or gears supported by both shafts, at least One transmission member includes a first rotating body fixed to the shaft, and a second rotating body that is movable in the axial direction with respect to the first rotating body and has a transmission element on the outer peripheral part.
a rotating body, a pair of cam grooves formed on opposing surfaces of both rotating bodies, and at least one of which is formed to become gradually shallower toward the outer end; and a pair of cam grooves that are engaged between the two cam grooves. A weight that can slide approximately radially along both of these cam grooves, and an elastic body that presses both of the rotating bodies in the direction toward each other and biases the weight toward the inner end of the deeper cam groove. and the outer end of the cam groove of the first rotating body is offset in the direction of rotational advance relative to the outer end of the cam groove of the second rotating body. An engine valve train featuring: