TRANSMISSION HOUSING ASSEMBLY WITH A FREEWHEEL FOR SUPPORTING A MOTOR SHAFT

Abstract

A transmission housing assembly includes a transmission housing and a freewheel including an inner ring and an outer ring. The inner ring is non-positively connectable to a motor shaft. The transmission housing includes a steel bearing bush overmolded with aluminum, which defines an opening of the transmission housing into which the freewheel is pressed.

Claims

1. A transmission housing assembly, comprising: a transmission housing; and a freewheel including an inner ring and an outer ring; wherein the inner ring is non-positively connectable to a motor shaft; the transmission housing includes a steel bearing bush overmolded with aluminum which defines an opening in the transmission housing; the freewheel is pressed into the opening in the transmission housing.

2. The transmission housing assembly according to claim 1, wherein the opening of the transmission housing is centrally located in the transmission housing.

3. The transmission housing assembly according to claim 1, wherein the steel bearing bushing has a non-round shape on its outside.

4. The transmission housing assembly according to claim 1, wherein the inner ring of the freewheel is seated on a motor shaft and pressed thereto.

5. The transmission housing assembly according to claim 1, wherein the freewheel includes a backstop and allows rotation of the motor shaft in only one direction.

6. An actuator of an automotive automatic transmission, the actuator comprising: an electric motor with a motor shaft; and a transmission with the transmission housing assembly according to claim 1.

7. A method for producing a transmission housing assembly of an actuator of a motor vehicle automatic transmission, the method comprising: providing a casting mold to form a transmission housing of the transmission housing assembly; inserting a steel bearing bushing into the mold; pressing aluminum into the mold and forming a positive connection between the aluminum and the steel bearing bushing and an opening in the gear housing defined by the steel bearing bushing; and pressing a freewheel into the steel bearing bushing.

8. The method according to claim 7, wherein the steel bearing bushing has a non-round shape on an outside.

9. The method according to claim 7, wherein the freewheel includes an inner ring and an outer ring.

10. The method according to claim 9, wherein the transmission housing assembly includes a motor shaft; and the method further includes pressing the inner ring of the freewheel with the motor shaft.

11. The method according to claim 7, wherein the freewheel includes a backstop and allows a rotational movement of the motor shaft in only one direction.

12. The method according to claim 7, wherein the freewheel is a ball bearing freewheel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Example embodiments of the present disclosure are explained in more detail below with reference to the drawings. Identical or functionally identical components are provided with the same reference signs in the figures.

[0021] FIG. 1 is an exploded view of a transmission housing according to an example embodiment of the present disclosure with freewheel.

[0022] FIG. 2 is an isometric representation of the assembled gear housing according to an example embodiment of the present disclosure.

DETAILED DESCRIPTION

[0023] FIG. 1 shows a gear housing 1 of a gear housing assembly 3. The gear housing 1 has a central opening 4 into which a freewheel 5 is inserted. The freewheel 5 is a ball bearing freewheel with inner ring 6 and outer ring 7. The ball bearing freewheel 5 is used as a backstop, i.e. it prevents the motor shaft not shown from rotating backwards.

[0024] The outer ring 7 has not shown recesses on the inside, in which balls are accommodated. The balls are spring preloaded towards a clamping position. The recesses extend in the circumferential direction, with the depth of the recess decreasing continuously in the opposite direction to the direction of forward rotation of the motor. In the clamping position, the depth is so small that the balls are clamped between the inner ring 6 and the outer ring 7 so that rotation of the motor shaft in the reverse direction is prevented. If the inner ring 6 rotates with the motor shaft in the forward direction of rotation of the motor, the balls are pressed against the spring force into an area of the recess where the balls have no contact with both rings 6,7. In this freewheel area, the motor shaft can rotate freely without blocking.

[0025] The described ball bearing freewheel 5 is only one of many suitable freewheels with backstop available on the market. Also available are freewheels without springs, with cylindrical rollers instead of balls and/or freewheels with sprags. Depending on the application, an appropriate freewheel must be selected.

[0026] Transmission housing 1 is made of aluminum and is manufactured by die-casting aluminum. However, due to the high coefficient of thermal expansion, the aluminum housing is not suitable for a secure and tight fit of the freewheel 5 in the opening 4 and for good support of the occurring forces at high temperatures.

[0027] Therefore, during the production of the transmission housing 1 using the aluminum die casting process, a steel bearing bush 8 is placed in the casting mold. The molten metal is pressed under high pressure into the preheated casting mold and injected around the steel bearing bushing 8.

[0028] To ensure that the steel bearing bushing 8 is firmly seated in the gear unit housing 1, the steel bearing bushing 8 has a non-circular shape on the outside 9.

[0029] FIG. 2 shows the gear housing 1 as seen from below on the steel bearing bushing 8. The die casting process creates an inseparable positive connection between the aluminum and the steel bearing bushing 8. The freewheel 5 is pressed into the steel bearing bushing 8 during assembly. The steel bearing bushing 8 holds the freewheel 5 securely in position over a temperature range of −40° C. to 150° C. with constant force absorption.

[0030] While example embodiments of the present disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. The scope of the present disclosure, therefore, is to be determined solely by the following claims.