| 摘要 |
<p>A utility vehicle, such as a grape harvester (1), comprises a straddling frame (2), supported at its front and rear ends by double-acting hydraulic cylinders (17, 18 and 23, 24), which can be extended or retracted in order to level the frame (2). The rear cylinders (23, 24) are normally blocked for providing the vehicle (1) with a fixed rear axle (55), while the front cylinders (16, 17) are hydraulically interconnected in order to let them extend or retract in opposition to each other for providing the vehicle (1) with an articulated axle (56). The hydraulic cylinders (17, 18, 23, 24) are governed by two control valves (38, 39) which enable lifting, lowering and sideways levelling of the frame (2). During levelling operations, the hydraulic connection between the front cylinders (16, 17) is automatically broken by a control valve (65) in order to enhance the stability of the vehicle (1). This is particularly advantageous when the vehicle (1) is levelled during downhill travel. <MATH></p> |
