US 4,858,435 AGranted

Fluid pressure control circuit for working vehicle having transmission operable by fluid pressure

AssigneeKubota Corporation

InventorKenji Ikeda

Life of this patent

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Abstract

A fluid pressure control circuit for a working vehicle having a transmission operable by a fluid pressure and a negative type fluid pressure parking brake. The control circuit comprises a fluid pressure cylinder movable to a first end position to place the transmission in a low speed position and to a second end position to place the transmission in a high speed position, a fluid supply line for supplying pressure fluid to the cylinder, and a control valve mounted on the fluid supply line. The control valve comprises a three position valve having a first position to release the pressure fluid from the parking brake and the fluid supply line, a second position to supply the pressure fluid to the parking brake and set the cylinder to the first end position, and a third position to supply the pressure fluid to the parking brake and set the cylinder to the second end position.

Claims4

Dependent claims

A fluid pressure control circuit for a working vehicle having transmission means operable by a fluid pressure, comprising:

fluid pressure actuator means for controlling said transmission means said actuator means including a first cylinder acting to control a main change speed operation of said transmission means and a second cylinder acting to control an auxiliary change speed operation of said transmission means, said second cylinder being movable to a first end position to place said transmission means in a low sped position and to a second end position to place said transmission means in a high speed position,
a fluid supply line for supplying pressure fluid to said first and second cylinders of said fluid pressure actuator means,
fluid pressure parking brake means connected to said fluid supply line, said fluid pressure parking brake means being a negative-type brake operable by fluid pressure to release parking brakes, and
control valve means mounted on said fluid supply line and having a first position to release the pressure fluid from said fluid supply line and thereby from said fluid pressure parking brake means and a second position to supply the pressure fluid to said fluid pressure parking brake means, and to control the supply of the pressure fluid from said fluid supply line to said fluid pressure actuator means in order to set said second cylinder selectively to said first end position and said second end position.

1 more element

Dependencies are inferred from the claim text.

Facts

Application: 07/142,960Filed 12 Jan 1988
Priority: JP 62-69543[U]9 May 1987
Granted: 22 Aug 1989
Term ends: Not estimatedThe source records don’t support an estimate.

Classification9 codes

B60T 13/22
The fluid being liquid: brakes applied by springs or weights and released hydraulically
B60W 10/10
Conjoint control of vehicle sub-units of different type or different function: including control of change-speed gearings
B60W 10/182
Including control of braking systems: including control of parking brakes
B60W 30/18
Purposes of road vehicle drive control systems not related to the control of a particular sub-unit, e.g. of systems using conjoint control of…:…