| 摘要 |
A gearchange control arrangement for an automatic transmission for motor vehicles comprises a planetary reduction gear and a brake band for changing the transmission ratio. The arrangement serves to apply the brake band gradually. The arrangement comprises a servopiston, a piston rod attached to the servopiston and the brake band and a collecting-chamber piston which is inserted with the ability to slide axially in the bore of the servopiston. The servopiston is preloaded by a first spring which serves to return the servopiston in order to release the brake band. The collecting-chamber piston is preloaded by a second spring at one end of the bore of the servopiston. Oil chambers for the application and release of the brake band are formed on opposite sides of the servopiston and a collecting oil chamber is formed between the end of the bore and the collecting-chamber piston. Pressurised oil is fed to the application oil chamber, thereby moving the servopiston, counter to the first spring, in the direction of application of the brake band. The collecting-chamber piston then moves by a certain stroke counter to the second spring. The collecting-chamber piston then comes into engagement with the servopiston, with the result that the two pistons move together to tighten the brake band. <IMAGE>
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