WO1993015928A1

WO1993015928A1 - Gearshift lever and a method of forming a gearshift lever

Info

Publication number: WO1993015928A1
Application number: PCT/US1993/001014
Authority: WO
Inventors: Anthony R. Gurney
Original assignee: Dura Mechanical Components, Inc.
Priority date: 1992-02-10
Filing date: 1993-02-05
Publication date: 1993-08-19

Abstract

A gearshift lever (12) for an automotive vehicle is made of a low carbon plain carbon steel by the cold heading process. The lever (12) includes an integral part-spherical ball portion (22) and is formed from a single rod (50) that is deformed in a single or progressive die by applying a substantial endwise force to the rod (50). The finished lever (12) has a hardness of Rockwell ''B'' 50-90.

Description

GEARSHIFT LEVER AND A METHOD OF FORMING A GEARSHIFT LEVER

BACKGROUND OF THE INVENTION

This invention relates generally to gearshift levers for automotive vehicle transmissions and, more particularly, to a gearshift lever for a manual transmission.

Many automotive manual transmissions are located remotely from the driver-operated gearshift lever, which is frequently mounted in a floor-mounted console. This is particularly true in front-wheel drive vehicles, which have recently become more popular. Originally, in such vehicles the gearshift levers were connected to the transmission by a linkage comprising interconnected rigid links.

Recently, automotive vehicles have become smaller to decrease weight. This "downsizing" forces the compaction of all mechanical elements into a smaller vehicle envelope. This compaction, plus the addition of the catalytic converter effectively eliminates the straight line path necessary for the use of a linkage of rigid elements.

Th s, shifters have been developed which do not require a linear path to link the gearshift lever and the transmission. These shifters use pairs of Bowden cables which are snaked around underbody obstructions to connect the transmission and the gearshift lever. This enables lever movement to be transmitted to the transmission in a nonlinear path.

The initial cable shifters were of the so-called cross-axis type in which the lever is connected to one cable and is pivotally attached to a lever carrier. The carrier is pivoted about a spaced axis to a mounting base and is attached to the other cable. These bulky shifters are now being replaced by shifters which eliminate the lever carrier. A ball mounted on the shift lever is received in a socket on the base to enable universal movement of the lever, which is connected to both cables. This design provides a more compact mechanism.

Applicant's assignee has developed such a ball shifter, as illustrated in U.S. Patent 4,693,135 to LaRocca et al. That patent illustrates a shift lever constructed of a steel lever to which is mounted a plastic ball. The use of a separate ball, however, requires the added expense of assembly of the ball on the lever.

The current version of this shifter eliminates the separate ball by incorporating an integral ball. The shifr lever is formed by machining a single piece of steel to produce a shifter with an integral ball. This eliminates the assembly operation and its attendant cost. After machining, it is drilled at its lower end for attachment to a shift cable. To provide good machinability, the hardness needed for ball durability and sufficient tensile strength at its lower end without heat treatment, SAE 1144 steel is used. Machining of the lever is a relatively slov: and expensive process, and requires use of an expensive steel.

Thus, there is a need for a shift lever for a ball shifter which has a ball of sufficient hardness and sufficient strength at its lower end to provide needed durability and which can be quickly and inexpensively manufactured.

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide a shift lever for a ball shifter which has a ball of sufficient hardness and sufficient strength at its lower end to provide needed durability and which is inexpensive to manufacture.

Accordingly, this invention features a gearshift lever having an integral part-spherical ball intermediate its ends that is characterized by being made of plain carbon steel and having a hardness of Rockwell"B" 50-90.

This invention also features a gearshift lever made of low carbon plain carbon steel in which its lower end has a greater cross-section area than its upper end.

This invention further features a gearshift lever that is cold headed to produce the Rockwell"B" 50-90 hardness.

In another aspect, this invention features a method of forming a gearshift lever having an integral part-spherical ball intermediate its ends which comprises the steps of:

a. providing a rod of low carbon plain carbon steel, b. providing a die having a cavity conforming to the finished shape of the lever, c. placing the rod in the die cavity, d. applying an endwise force to the rod at room temperature to force the rod to conform to the cavity shape, and e, removing the formed lever from the die.

These and further objects and features of this invention will become more readily apparent upon reference to the following detailed description of a preferred embodiment, as illustrated in the accompanying drawings, in which: BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a side elevation of a gearshift mechanism employing a gearshift lever according to this invention;

Fig. 2 is a partially broken-away front elevation of the mechanism of Fig. 1;

Fig. 3 is a side elevation of the gearshift lever of

Figs. 1 and 2, formed in accordance with the method c this invention; and

Fig. 4 is a side elevation of a steel rod prior tc being formed into the lever of Fig. 3 in accordance with the method of this invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring now to Figs. 1 and 2 of the drawings, a shifter 10 comprises a gearshift lever 12 that is manipulated to effect movement of Bowden cables 14 and IC which are mounted on shifter base 18 and are connected tc a conventional automotive manual transmission (not shown) . The shifter 10 is substantially the same as the shifter disclosed in U.S. Patent 4,693,135 to LaRocca et al, which is incorporated herein by reference.

Lever 12 mounts a knob 20 at the upper end cf it? upper portion 21 and incorporates an integral ball II that is received in a ball cage 24 mounted in base 18. Lever 12 is made of steel in a manner described later, while cage 2 is made of plastic, preferably Delrin. The lower end 26 cf lever 12 is drilled for connection by a pivot pin 28 to one end of a lever extension link 30. Lower end 26 of lever 12 has a greater cross-section (i.e. is thicker) than upper lever portion 21.

A pin 36 extends laterally from ball 22 and terminates in a ball end 38 that is slidingly received in the end of one arm of a bellcrank 39 which is pivoted by pin 42 to base 18. The other end of bellcrank 39 is pivoted by pin 42 to end fitting 44 for cable 14. With this arrangement, movement of shift lever 12 about longitudinal axis X pivots bellcrank 39 which results in movement of cable 14. Further details of construction and operation of shifter 12 can be found in the LaRocca patent.

Referring now to Figs. 3 and 4, gearshift lever 12 is a 260 mm unitary piece of SAE 1010 or 1018 steel that includes ball 22 as an integral portion. In accordance with this invention, lever 12 is formed from a single piece of 15 mm diameter rod 50 cut from a wire coil and impact deformed by the cold heading process.

The cold heading process, also sometimes known as cold forging, is a well-known process for making rivets by upsetting a piece of wire. In this process, rod 50 is placed in the cavity of a die and is subjected to a substantial endwise force (e.g. 500 tons) to deform the rod into the illustrated finished shape which includes upper lever portion 21, formed ball 22 and lower lever end 26 which is thicker than upper portion 21.

Ball 22 can be, but need not be, completely spherical.

Thus, ball 22 is illustrated as being part- spherical, comprising upper spherical portion 52 and lower spherical portion 54, separated by a flat circumferential band 56. After forming the lever, hole 58 is drilled through^"band 56 to receive pin 36. Similarly, hole 60 is drilled through lower lever end 26 to receive pin 28. Also, the upper end to receive and retain knob 20.

Depending on size and material, cold heading in a single die may not be sufficient to produce the desired shape. In this case, the rod must be sequentially deformed in a series of progressive dies (e.g. two or three) . The use of progressive dies is well-known and involves sequentially placing the rod in a series of dies and impacting it. These dies have cavities which progress through intermediate shapes to the desired finished article shape.

Gearshift levers must meet manufacturers' durability standards of many thousands of cycles. To accomplish this, the ball must have sufficient hardness. In the prior art shifter manufactured by the assignee herein, a block of SAE

1144 steel was screw machined into the desired finished unitary lever configuration. This is a relatively slow process (e.g. a production rate of ~ 50/hour) . In the automotive world, both durability and cost are important.

Thus, it is desirable to avoid the costly extra step of heat treating or other hardness enhancing process. SAE

1144 was selected both for its achinability an it? hardness.

By utilizing this invention, however, an inexpensive plain carbon steel can be used. Cold heading process work- hardens the steel. Also, cold heading enables lower lever end 26 to be thicker than the initial rod blank, providing more residual material around hole 60. Because of this, it has been found that a lower cost, low carbon steel, such aε SAE 1018, or even 1010, can be used. After cold heading, a 1010 steel gearshift lever will have a hardness of Rockwell"B" 50-70. Although this is minimally acceptable, it has been found more desirable to use the higher carbon 1018 steel which will have a hardness of Rockwell"B" 70-90 after fabrication by cold heading. In any event, the greater amount of residual material around hole 60, provided by forming a thicker lower lever end 26, increases the strength of the lever in this area to enable use of a lower tensile strength and lower cost steel.

Another advantage of this invention is a dramatic increase in production (e.g. a rate of ~ 500/hour) . Thus, by forming a gearshift lever according to this invention, the manufacturer can realize cost savings by increasing the production rate, in addition to the savings realized by using a lower cost steel and avoiding added finishing operations.

While only a preferred embodiment has been illustrated and described, obvious modifications thereof are contemplated within the scope of this invention and the following claims.

Claims

I claim:

1. A gearshift lever (12) having an integral part- spherical ball (22) intermediate its ends (21, 26) , characterized by being made of a solid rod (50) of plain carbon steel which is impact formed to form the ball (22) which is hardened to a hardness of Rockwell"B" 50-90.

2. The gearshift lever (12) of claim 1, further characterized by the lever end (26) on one side of the ball (22) having a greater cross-section than the lever end (21) on the other side of the ball (22) .

3. The gearshift lever (12) of claim 1, further characterized by being made of low carbon plain carbon steel.

4. The gearshift lever (12) of claim 3, further characterized by being made of SAE 1018 steel.

5. A method of forming a gearshift lever (12) having an integral part-spherical ball (22) intermediate its ends

(21, 26) from a rod (50) of low carbon plain carbon steel, characterized by the steps of:

a. providing a die having a cavity conforming to the finished shape of the lever, b. placing the rod (50) in the die cavity, c. applying an endwise force to the rod (50) at room temperature to force the rod (50) to conform to the cavity shape, and d. removing the formed lever (12) from the die. 6. The method of claim 5, further characterized by the steps of:

a. providing a succession of progressive dies, with the last die having a cavity conforming to the finished shape of the lever (12) , b. sequentially placing the rod (50) in each of the progressive die cavities, c. applying an endwise force to the rod (50) at room temperature to force the rod (50) to conform to the shape of each die cavity, and d. removing the formed lever (12) from the last die.

AMENDED CLAIMS

[received by the International Bureau on 27 July 1993 ⁽27.07.93⁾; original claim 1 amended; other claims unchanged ⁽2 pages⁾]

1. A gearshift lever (12) having an integral part- spherical ball (22) intermediate its ends (21, 26) , characterized by being made of a solid rod (50) of plain carbon steel which is impact formed to form the ball (22) which is work hardened during formation to a hardness of Rockwell"B" 50-90.

3. The gearshift lever (12) of claim l, further characterized by being made of low carbon plain carbon steel.

5. A method of forming a gearshift lever (12) having an integral part-spherical ball (22) intermediate its ends (21, 26) from a rod (50) of low carbon plain carbon steel, characterized by the steps of:

a. providing a die having a cavity conforming to the finished shape of the lever, b. placing the rod (50) in the die cavity, c. applying an endwise force to the rod (50) at room temperature to force the rod (50) to conform to the cavity shape, and d. removing the formed lever (12) from the die.

6. The method of claim 5, further characterized by the steps of:

STATEMENTUNDER ARTICLE 19

Claim 1 has been amended to more clearly state that the hardness of the finished gearshift lever is due to work hardening during the impact forming process.