JPS6220950A - Timing belt driving apparatus - Google Patents

Abstract

PURPOSE:To maintain good timing of a belt by fixing a dynamic damper having inherent vibration two times of the resonant frequency of a timing belt to a driven pulley to be rotatable concentrically. CONSTITUTION:A timing belt 5 is wound over the circumferential section of a driven pulley or a cam shaft pulley 4 over the predetermined angle. A dynamic damper 7 is fixed to the endface of a driven pulley 5 to be rotatable concentri cally. Inherent vibration of a dynamic damper 7 is set to double the resonant frequency of the timing belt 5. Consequently, the influence of resonance of the timing belt can be cancelled by the influence of inherent vibration of the dynamic damper resulting in good timing irrespectively of the vibration of the timing belt.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to, for example, a timing belt drive device that transmits the rotation of an engine crankshaft to a camshaft, fuel injection pump, etc. via a timing belt. It is.

[Prior art]

For example, as shown in Japanese Utility Model Application Publication No. 57-102752, a timing belt drive device is known that transmits the rotation of an engine crankshaft to a driven wheel such as a camshaft at a predetermined timing via a timing belt. be.

As shown in FIG. 6, such a timing belt drive device includes a crankshaft pulley 2 as a driving pulley fixed to one end of a crankshaft 1 as a driving shaft, and a camshaft 3 as a driven shaft fixed to one end. The timing belt 5 is wound around these pulleys 2 and 4, and the tension pulley 6 is used to adjust the tension of the timing belt 5. is customary. A toothed belt is normally used as the timing belt 5 in order to eliminate slippage between the crankshaft pulley 2 and the camshaft pulley 4.

Incidentally, it is known that such a timing belt 5 causes string vibrations between both pulleys 2 and 4, similar to the strings of a violin. At engine speeds where this string vibration is at resonance, the vibration becomes so noticeable that it can be seen with the naked eye. Along with this string vibration, vibration occurs in the direction perpendicular to this, that is, in the direction of the rotational force of the belt, and this vibration is caused by both pulleys 2
・It has the effect of trying to rotate 4 in opposite directions. In other words, as shown in FIG. 7, at timing a when the timing belt 5 is in a straight line between both pulleys 2 and 4, the crankshaft pulley 2 is rotated counterclockwise and the camshaft pulley 4 is rotated clockwise. Since the camshaft pulley 4 is intended to rotate in each direction, the rotational phase of the camshaft pulley 4 is ahead of the average rotational phase. On the other hand, both pulleys 2
・The timing heald 5 becomes arched outward between 4 and 4b
At the timing of , the crankshaft pulley 2 is to be rotated clockwise and the camshaft boot U4 is to be rotated counterclockwise, so the camshaft pulley 4
The rotational phase of lags behind the average rotational phase. Next, at timing C, when the timing belt 5 is in a straight line between both pulleys 2 and 4, the crankshaft pulley 2 is moved counterclockwise, and the camshaft pulley 4 is
, respectively, in the clockwise direction, the rotational phase of the camshaft pulley 4 is ahead of the average rotational phase. At timing d, when the timing belt 5 becomes arched inward between both pulleys 2 and 4, the crankshaft pulley 2 is moved clockwise and the camshaft pulley 4 is moved counterclockwise, similar to timing b. Since the rotation phase of the camshaft pulley 4 lags behind the average rotation phase. The vibration of the timing belt 5 ends when the timing belt 5 returns to the timing a when the timing belt 5 becomes linear again between the pulleys 2 and 4, and the vibration of one cycle λ ends.

In this way, the camshaft pulley 4, which is a driven pulley, vibrates at a vibration frequency twice that of the timing belt 5, and this variation in the rotational speed of the camshaft 3 causes the valve timing to go out of order, resulting in a decrease in engine output. Otherwise, the ignition timing of the ignition device linked to the camshaft 3 will be out of order, resulting in an extreme drop in engine output.

Theoretically, if the basic resonance frequency n of the string vibration of the timing belt 5 is made high enough so that the resonant vibration of the timing belt 5 does not occur in the normal engine speed range, the timing belt in the normal engine speed range can be It should be possible to prevent fluctuations in the rotational phase of the camshaft pulley 4 due to the vibrations of the timing belt 5 (and prevent the engine output from decreasing as described above). is inversely proportional to the length l, and proportional to the square root of the ratio of the string tension T to the string linear density σ.Therefore, in order to increase the fundamental resonance frequency n of the string vibration of the timing belt 5, the pulley interval By narrowing the string length l, the string tension T
It is conceivable to increase the linear density σ and to decrease the linear density σ.

However, the timing belt 5 has the necessary elasticity to bend along the periphery of both pulleys, and the cross-sectional area of the timing belt 5 required to transmit the required driving force is approximately fixed, so the timing belt It is not possible to significantly reduce the linear density σ of 5. Also, the tension T
There is also a limit to increasing , since this increases the resistance of the camshaft 3 and threatens the durability of the timing belt 5 . An idle pulley is provided between the crankshaft pulley 2 and the camshaft pulley 4, and the length of the string is l.
Although it is possible to double the fundamental resonance frequency n by halving it, in most cases the resonant vibration of the timing belt 5 still appears in the engine's normal rotational speed range. be.

As described above, it is extremely difficult to increase the basic resonant frequency n1 of the timing belt 5 so that the resonant vibration of the timing belt 5 does not appear in the normal rotational speed range of the engine.

[Purpose of the invention]

The present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a timing belt drive device that prevents timing errors on the driven pulley side due to resonance vibration of the timing belt 5. be.

[Structure of the invention]

A timing heald drive device according to the present invention is a timing heald drive device that transmits the rotation of a crankshaft to a driven pulley at a predetermined timing via a crankshaft pulley and a timing belt, in which a ring member rotates concentrically with the driven pulley. At the same time, by attaching a dynamic damper having an inertial body fixed to the outer periphery of the ring member via an elastic member and having a natural vibration frequency twice the resonant frequency of the timing belt, the timing belt can be improved. This is characterized in that the influence of resonance vibration is offset by the influence of vibration on the rigidity of the dynamic damper.

[Example 1] An example of the present invention will be described below based on FIGS. 1 to 3.

This embodiment is applied to a timing belt drive device provided between an engine crankshaft and a valve drive camshaft, and includes all the configurations shown in FIG. 6. Therefore, the corresponding members having the same functions as those shown in FIG. 6 will be described with the same reference numerals.

A camshaft pulley 4 serving as a driven pulley is fitted onto and fixed to one end of the valve-operating camshaft 3, and a timing belt 5 is wound around the periphery of the camshaft pulley 4 over a predetermined angular range. A dynamic damper 7 is attached to the end face of the driven pulley 5 with four bolts 8 so as to rotate concentrically therewith. The dynamic damper 7 is fixed to the end face of the camshaft pulley 4 and has a ring member 9 in the form of a rotating body having an L-shaped cross section, and an annular ring member 9 made of rubber or the like fixed to the outer circumferential surface of the ring member 9 by, for example, vulcanization adhesive. It is composed of an elastic member 10 and an annular inertial body 11 fixed to the outer peripheral surface of the elastic member 1o by vulcanization adhesive or the like. Further, the natural vibration frequency of the dynamic damper 7 is set to twice the resonance frequency of the timing belt 5.

In the above configuration, when the timing belt 5 vibrates chordally at its resonant frequency, the camshaft pulley 4 moves the timing belt 5 due to the vibration generated in a direction perpendicular to this vibration.
It is attempted to vibrate at a frequency twice the resonant frequency of. In response to the vibration of the timing belt 5 acting on the camshaft pulley 4, the vibration of the dynamic damper 7, which vibrates in the opposite direction to the vibration at a natural frequency twice the resonant frequency of the timing belt 5, acts on the camshaft. Acts on pulley 4. Therefore, the vibrations applied to the camshaft boot U 4 from the timing belt 5 are apparently canceled out by the vibrations applied from the dynamic damper 7, and timing errors due to vibrations of the timing belt 5 of the camshaft pulley 4 no longer occur. .

For example, in a conventional timing belt drive device that does not have a dynamic damper 7, as shown by the solid line in FIG. Then, in the above-mentioned embodiment in which the dynamic damper 7 is simply added, the fluctuation in the rotational speed of the camshaft pulley 4 due to the vibration of the timing belt 5 is reduced to the extent that it does not pose a practical problem, as shown by the broken line in Fig. 3. It has been experimentally confirmed that

[Embodiment 2] In another embodiment of the present invention, as shown in FIG.
I is divided into four equal parts in the circumferential direction. In such a configuration, each part 11a to lid is moved in the centrifugal direction by the centrifugal force acting on each part 11a to lid of the inertial body 11, so as the rotation speed increases, the natural frequency of the dynamic damper 7 increases. descend. Therefore,
As shown in FIG. 5, the fundamental resonance frequency n of the timing belt 5 decreases as the engine speed N increases.

The natural vibration frequency of the dynamic damper 7 can be changed correspondingly, and it is possible to prevent timing deviations of the camshaft pulley 4 due to vibrations of the timing belt 5 over a wider range of engine speeds.

The present invention is not limited to the above-mentioned embodiments. For example, the ring member 9 may be formed into a flat plate shape, and the inertial body 11 may be fixed to the peripheral edge of the end surface of the ring member 9 through an annular elastic member 10. It goes without saying that the present invention can also be applied to a timing belt drive device between the crankshaft 1 and the fuel injection pump.

〔Effect of the invention〕

As described above, the timing belt drive device of the present invention dynamically reduces the influence of the resonant vibration of the timing belt by attaching a dynamic damper whose natural vibration frequency is twice the resonant frequency of the timing belt so as to be rotatable concentrically to the driven pulley. Since this is offset by the influence of the damper's natural vibration, it is possible to eliminate timing errors, that is, rotational speed fluctuations caused by vibrations of the timing belt of the driven pulley.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of the main part of an embodiment of the present invention, FIG. 2 is a front view thereof, and FIG. 3 is a comparison between the above embodiment and a conventional example. Driven pulley rotation speed variation - engine rotation number relationship diagram,
Fig. 4 is a front view of another embodiment of the present invention, Fig. 5 is a timing belt resonance frequency-engine rotation speed relationship diagram, Fig. 6 is a perspective view of a conventional example, and Fig. 7 is a timing belt resonance vibration. FIG. 3 is an explanatory diagram of the relationship between frequency and the resulting rotational speed fluctuation frequency of the camshaft. 1 is the drive shaft (crankshaft), 2 is the drive pulley (
4 is a driven pulley (camshaft pulley), 5 is a timing belt, 7 is a dynamic lift damper, 9 is a ring member, 10 is an elastic member, and 1 is an inertial body. Figure 1 Figure 2 Figure 4 [ Figure 3 Figure 6 Figure 7

Claims (1)

[Claims] 1. In a timing belt drive device that transmits the rotation of the drive shaft to a driven pulley at a predetermined timing via a drive pulley and a timing belt, a ring member that rotates concentrically with the driven pulley is attached to the driven pulley, and the outer circumference of this ring member is 1. A timing belt device comprising: an inertial body fixed to the timing belt via an elastic member; and a dynamic damper having a natural vibration frequency twice the resonance frequency of the timing belt.