Hydraulically driven vehicle

Abstract

A hydrostatic transaxle, comprises: a transaxle casing; a pair of left and right axles disposed in the transaxle casing; a pair of hydraulic motors for driving the respective axles; and a pair of left and right steerable drive wheels disposed on left and right outsides of the transaxle casing so as to be drivingly connected to the respective axles. The hydraulic motors are disposed in the housing so as to be fluidly connected to a common hydraulic pressure source in parallel to each other. One of the hydraulic motors is a fixed displacement hydraulic motor, and the other is a variable displacement hydraulic motor. Displacement of the variable displacement hydraulic motor is changed according to change of steered angles of the drive wheels.

1 . A hydraulically driven vehicle, comprising: 
 a first transaxle, including 
 a first transaxle casing,  
 a pair of left and right first axles disposed in the first transaxle casing,  
 a first hydraulic motor disposed in the first transaxle so as to drive the first axles, and  
 a pair of left and right first drive wheels steerably disposed on left and right distal ends of the first transaxle casing and drivingly connected to the respective first axles;  
   a second transaxle, including 
 a second transaxle casing,  
 a pair of left and right second axles disposed in the transaxle casing,  
 a second fixed displacement hydraulic motor disposed in the second transaxle casing so as to drive one of the second axles,  
 a third variable displacement hydraulic motor disposed in the second transaxle casing so as to drive the other second axle, and  
 a pair of left and right second drive wheels steerably disposed on left and right distal sides of the second transaxle casing and drivingly connected to the respective second axles, wherein a displacement of the third hydraulic motor is changed according to change of steered angles of the second drive wheels; and  
   a common hydraulic pressure source for the first, second and third hydraulic motors, wherein the first hydraulic motor and the pair of second and third hydraulic motors are fluidly connected in series to the hydraulic pressure source, and wherein the second hydraulic motor and the third hydraulic motor are fluidly connected in parallel to the hydraulic pressure source.    
   
   
       2 . The hydraulically driven vehicle according to  claim 1 , wherein the first transaxle casing is pivoted onto a vehicle frame so as to be horizontally rotatable, and wherein the left and right first drive wheels are unsteerably connected to the respective first axles.  
   
   
       3 . The hydraulically driven vehicle according to  claim 1 , further comprising: 
 a pair of left and right steerable casings relatively horizontally rotatably attached onto respective left and right ends of the first transaxle casing so as to support the respective first drive wheels, thereby making the first drive wheels steerable;    a rotary member pivoted on the first transaxle casing so as to be connected to a steering actuator; and    a pair of link members each of which is pivotally interposed between the rotary member and each of the steerable casings.    
   
   
       4 . The hydraulically driven vehicle according to  claim 1 , further comprising: 
 a pair of left and right steerable casings relatively horizontally rotatably attached onto respective left and right ends of the second transaxle casing so as to support the respective second drive wheels, thereby making the second drive wheels steerable; and    a displacement control section for controlling displacement of the third hydraulic motor, wherein the displacement control section is connected to a link member extended from one of the steerable casings so as to enable the change of displacement of the third hydraulic motor according to change of steered angles of the second drive wheels.