# US 5,700,220 A · Power-shiftable gear, especially two-speed planet gear

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- Number: US 5,700,220 A
- Document ID: US5700220A
- Status: Granted
- Kind: A
- Application number: 08/687,356
- Filed: 1996-08-01
- Granted: 1997-12-23
- Earliest claimed: 1994-02-19
- Assignees: ZF Friedrichshafen AG
- Inventors: Jurgen Legner
- Web page: https://patentgrep.com/patent/US5700220A

## CPC

- F16H 3/54: one of the central gears being internally toothed and the other externally toothed
- F16H 61/067: {using an accumulator}
- F16H 2063/3036: {the clutch is actuated by springs and released by a fluid pressure}
- F16H: GEARING

## Abstract

The invention relates to a power-shiftable two-speed gear. The gear is designed as planet gear (3). The two ratios can be hydraulically shifted via two friction clutches (9 and 10). At least one of the friction clutches (9 or 10) is fitted with a mechanism which prevents the full locking pressure from acting upon the friction components during downshifts or upshifts. A store (30), which the torque curve can be affected, is used for this purpose. To prevent traction loss and abrupt changes which are found to be particularly unpleasant, the store (30) consists of a cylinder (32) and a piston (33) is fitted in the line (18 and 24) leading to the pressure chamber (17 and 23). A non-return valve (28) with a choke (29) in parallel with it is integrated into the piston.

## Claims

### Claim 1

A power-shiftable gear, especially two-speed gear designed as planet gear (3), having at least one friction clutch (9 and 10) the friction components of which (13, 14 and 19, 20) are engaged by spring tension (16, 22) and disengaged by oil pressure, having a line (18 and 24) which leads to a pressure chamber (17 and 23) and in which is a store (30) comprising of one cylinder (32) and one spring-loaded piston (33) with a non-return valve (28) and a choke (29) in parallel with it.

### Claim 2 (depends on 1)

A gear according to claim 1, characterized in that said piston (33), when said friction clutch (9 and 10) is engaged, assumes a position in which the store has a minimum storage capacity (35).

### Claim 3 (depends on 1)

A gear according to claim 1, characterized in that in said store (30), at the beginning of engaging said friction clutch (9 and 10) when said line (18 and 24) is connected with said tank (17) and said non-return valve (28) is engaged, part of the pressure medium is transmitted into said pressure chamber (17 and 23), said store (30) has a maximum storage capacity (35).

### Claim 4 (depends on 3)

A gear according to claim 3, characterized in that the residual pressure medium remaining in said pressure chamber (17 and 23) discharges via said choke (29) during the further course of the closing movement of said friction clutch (9 and 10).

### Claim 5 (depends on 3)

A gear according to claim 3, characterized in that a ratio of the capacity of said pressure chamber (17 and 23), when said friction clutch (9 and 10) is disengaged, to the maximum store capacity (35) is about 2:1.

### Claim 6 (depends on 4)

A gear according to claim 4, characterized in that a ratio of the capacity of said pressure chamber (17 and 23), when said friction clutch (9 and 10) is disengaged, to the maximum store capacity (35) is about 2:1.