Shift Lever of a Transmission for an Automobile

This invention relates to a shift lever of a transmission for an internal combustion engine in an automobile.

Traditionally, as is well known in the art, transmissions for an internal combustion engine are classified as a manual transmission and an automatic transmission. In a manual transmission, a shift and select operations are carried out by a shift lever. The shift lever is composed of a first shift lever having a cylindrical portion and a rod-like portion which are coaxial each other, and a rod-like second shift lever having a smaller diameter than the cylindrical portion of the first shift lever. The upper end portion of the second shift lever is inserted into the cylindrical portion of the first shift lever by a predetermined length. The lower end portion of the second shift lever is fixed to a shift lever retainer provided in an extension housing of the transmission. A grip is fitted to the upper end of the rod-like portion of the first shift lever. During engine operation, the extension housing may vertically vibrate, which may cause sizzle vibration and sizzle noise of the shift lever. In the case of slow accelaration from a constant engine speed, noise may be generated by torsional vibration due to play in a driving system, or which noise is the resonance noise occurring from twist of drive line and is called "Jara" noise, and this "Jara" noise may be propagated through the shift lever into an automotive compartment.

Traditionally, in order to reduce such sizzle vibration and sizzle noise of the shift lever, and such "Jara" noise propagated through the shift lever into the automotive compartment, shock absorbing rubber rings are packed in the annular space defined by the cylindrical portion of the first shift lever and the inserted portion of the second shift lever into the cylindrical portion at the upper and lower end portions thereof. However, unless the spring constant of the shock absorbing rubbers is considerably reduced, it may be difficult to minimize the propagation of the sizzle vibration, sizzle noise and "Jara" noise of the shift lever into the automotive compartment. In this case, if the spring constant of the shock absorbing rubbers is extremely reduced, the durability of the shift lever decreases, and during the operation of the shift lever, the first shift lever is greatly bent relative to the second shift lever, thereby causing an operation feeling of the shift lever to be remarkably made worse.

It is an object of the present invention to provide a shift lever which remarkably reduces sizzle vibration and sizzle noise.

It is another object of the present invention to provide a shift lever whereby the propagation of "Jara" noise into an automotive compartment is reduced.

It is still another object of the present invention to provide a shift lever which hardly bends during the shift operation and improves an operation feeling of the shift lever.

In the present invention, a predetermined length of the second shift lever is inserted into the cylindrical portion of the first shift lever. In the annular space defined by the cylindrical portion of the first shift lever and the inserted portion of the second shift lever into the cylindrical portion, a first elastic material such as a soft rubber is disposed and bonded onto the peripheral surfaces of both the inserted portion and the cylindrical portion, and a second elastic material such as a hard rubber is bonded onto either inner peripheral surface of the cylindrical portion of the first shift lever or outer peripheral surface of the inserted portion of the second shift lever, thereby defining an annular narrow clearance between either peripheral surface and the elastic material.

Various general and specific objects, advantages and aspects of the invention will become apparent when reference is made to the following detailed description considered in conjunction with the accompanying drawings.

FIG. 1 shows a schematic illustration of the shift lever mounted in an extension housing of a transmission according to the present invention;

FIG. 2 is a vertical sectional view of the first preferred embodiment of the invention;

FIG. 3(a) is an elevational view of the essential part shown in FIG. 2;

FIG. 3(b) is a side sectional view of FIG. 3(a);

FIG. 4(a) is an elevational view of the another essential part shown in FIG. 2;

FIG. 4(b) is a side sectional view of FIG. 4(a);

FIG. 5 is a side sectional view of the still another essential part shown in FIG. 2;

FIG. 6 is a vertical sectional view of the second preferred embodiment of the invention;

FIG. 7 is a side sectional view of the essential part shown in FIG. 6; and

FIG. 8 is a vertical sectional view of the third preferred embodiment of the invention.

Referring now to FIGS. 2-5, a shift lever 1 has a first shift lever 2 and a second shift lever 3. The first shift lever 2 is comprised of a rod-like portion 2a, a hollow cylindrical portion 2b coaxial with the rod-like portion 2a and a conical portion 2c connecting the rod-like portion 2awith the cylindrical portion 2b. The upper end of the rod-like portion 2a is threaded to form a male screw 2d. The second shift lever 3 is a circular rod, the diameter of which is smaller than that of the cylindrical portion 2b of the first shift lever 2, and is composed of three portions which differ in diameter, that is, a smaller diameter portion 3a, a medium diameter portion 3b and a larger diameter portion 3c. The whole length of the smaller diameter portion 3a and a greater part of the medium diameter portion 3b are inserted into the cylindrical portion 2b of the first shift lever 2. Hereinafter this portion will be referred to as an inserted or end portion of the second shift lever 3. In an annular space 4 defined between the cylindrical portion 2b of the first shift lever 2 and the smaller diameter portion 3a as well as the medium diameter portion 3b of the second shift lever 3, a soft (i.e., relatively low spring constant) rubber ring 5 (a first vibration damping elastic member) is packed and bonded onto both the outer peripheral surface of the upper end portion of the smaller diameter portion 3a and the inner peripheral surface of the cylindrical portion 2b. Similarly, a ring-like soft rubber assembly (a second elastic vibration damping member) 6 is packed into the space 4 at the lower end portion of the cylindrical portion 2b. The rubber assembly 6 is comprised of a steel inner tube 6a, a steel outer tube 6b coaxial with the inner tube 6a and a soft rubber ring 6c bonded onto the peripheral surfaces of both tubes 6a and 6b, and packed into an annular space between the tubes 6a and 6b. The outer tube 6b is closely fitted with an inner peripheral surface of the cylindrical portion 2b of the first shift lever 2 and the inner tube 6a is closely fitted with an outer peripheral surface of the medium diameter portion 3b of the second shift lever 3. A through-hole 6d is provided in the soft rubber ring 6c, in order to reduce a spring constant with respect to that of the first and second elastic members) of the rubber assembly 6 if desired. A hard (i.e. relatively high spring constant) rubber ring third elastic vibration damping numbers 7 is disposed in the annular space 4 between the cylindrical portion 2b having an axial length L defined from the rubber ring 5 to the rubber ring 6c of the rubber assembly 6 and the second shift lever 3. There is provided an annular narrow clearance 8 between the rubber ring 7 and the smaller diameter portion 3a as well as the medium diameter portion 3b. The rubber ring 7 is closely fitted with the inner peripheral surface of the cylindrical portion 2b of the first shift lever 2. The rubber ring 7 is disposed in spaced apart relation from the rubber rings 5 and 6c.

The larger diameter portion 3c of the second shift lever 3 is curved at the lower portion thereof and its lower end is mounted to the shift lever retainer 11 fitted to the extension housing 10 of the transmission 9 at the lower end so as to permit the inclination in all directions. A grip 12 is threadedly engaged with the male screw 2d of the first shift lever 2.

During engine operation, the extension housing 10 will vertically vibrate and the second shift lever 3 will also vibrate in its axial direction or vertically. However, since the vibration of the second shift lever 3 may be diminished by the damping action of the soft rubber rings 5 and 6c, the vibration of the first shift lever 2 is extremely diminished. Accordingly, the sizzle vibration and sizzle noise due to the shift lever 1 can be reduced and the propagation of the "Jara" noise into the automotive compartment can be effectively avoided.

When the shift lever 1 is operated by moving the grip 12 by hand, that is, shifted and selected, both the rubber rings 5 and 6care deformed. However, since the force acting on the rubber ring 5 is greater than that acting on the rubber ring 6c, the rubber ring 5 is more greatly deformed than the rubber ring 6c. As a result, the smaller diameter portion 3a of the second shift lever 3 is brought into contact with the rubber ring 7 at the portion adjacent to the rubber ring 5. Accordingly, the first shift lever 2 is tilted relative to the second shift lever 3 until the smallerdiameter portion 3a comes to contact with the rubber ring 7. But, the first shift lever 2 is hardly tilted relative to the second shift lever 3 because of the hardness of the rubber ring 7 after the rubber ring 7 contacted with the smaller diameter portion 3a of the second shift lever 3. The angle of inclination of the first shift lever 2 relative to the second shift lever 3 can be set to be small by making the clearance 8 to be small, causing the operation feeling of the shift lever 1 to be improved as compared to the conventional shift lever. In the modification of the shift lever structure, the rubber ring 7 may be bonded to the inserted portion of the second shift lever 3 and the clearance 8 may be defined between the rubber ring 7 and the cylindrical portion 2b. The rubber ring 5 may be formed without the recesses as shown in FIG. 3.

Referring to FIGS. 6 and 7, there is shown a shift lever 21 of the second embodiment according to the present invention. Similar reference numbers are utilized to describe similar components in the first preferred embodiment, omitting the explanation of such components. In comparison to the shift lever 1 in FIG. 1, the shift lever 21 is not provided with the rubber ring 7. The rubber ring 25 corresponding to the rubber ring 5 of the shift lever 1 is included in the shift lever 21 and is formed of a soft rubber inner ring 25a bonded to a hard rubber outer ring 25b. To effectively diminish the vertical or axial vibration of the first shift lever 2, the volume of the inner ring 25a is preferably made equal to the volume of the rubber ring 5 in FIG. 1. As a result, the axial length of the rubber ring 25 is greater than that of the rubber ring 5.

In the shift and select operations of the shift lever 21, the first shift lever 2 is slightly tilted relative to the second shift lever 3 because of the softness of the inner ring 25a, but the hard rubber outer ring 25b instantaneously shows a resilient (i.e., secondary vibration damping) effect to prevent an excessive inclination of the first shift lever 2. Accordingly, the operation feeling of the shift and select operations is not impaired at all. Since the vertical vibration of the second shift lever 3 can be diminished by the action of the inner ring 25a of the rubber ring 25 and the rubber assembly 6, the propagation of the sizzle vibration and sizzle noise to the first shift lever 2 can be reduced and the propagation of the "Jara" noise through the shift lever 21 into the automotive compartment can be also reduced. In the second preferred embodiment, the inner ring 25a and the outer ring 25b may be made of a hard rubber and a soft rubber, respectively.

Referring to FIG. 8, there is shown a shift lever 31 of the third embodiment according to the present invention. Similar reference numbers are utilized to describe similar components in the first preferred embodiment, omitting the explanation of such components. In comparison to the shift lever 1 in FIG. 1, the shift lever 31 is not provided with the rubber ring 7. The rubber ring 5 and the rubber assembly 6 are provided with hard rubber rings 32 and 33, respectively. In FIG. 8, the hard rubber ring 32 is bonded to the inner peripheral surface of the cylindrical portion 2b of the first shift lever 2, but it may be bonded to the outer peripheral surface of the smaller diameter portion 3a of the second shift lever 3. In a similar fashion, the hard rubber ring 33 may be bonded to the inner peripheral surface of the outer tube 6b of the rubber assembly 6 instead of being bonded to the outer peripheral surface of the inner tube 6a of the rubber assembly 6.

In the shift and select operations of the shift lever 31, the rubber ring 5 and the rubber assembly 6 effectively diminish the propagation of the vibration through the second shift lever 3 and the first shift lever 2. Furthermore, the hard rubber rings 32 and 33 effectively prevent an excessive bending of the first shift lever 2 to the second shift lever 3. As shown in FIG. 8, the contact area of the soft rubber ring 5 and the hard rubber ring 32 is made small owing to the difference in the spring constant of both rubber rings 5 and 32 so as to increase the durability of the soft rubber ring 5.

Having thus described the preferred embodiments of the invention it should be understood that numerous structural modifications and adaptations may be restored to without departing from the spirit of the invention.