Travel control device for hydraulically driven vehicle and hydraulically driven vehicle

• US 20070119163A1
• Filed: 09/17/2004
• Published: 05/31/2007
• Est. Priority Date: 09/30/2003
• Status: Active Grant

• Current Assignee: Hitachi Construction Machinery Company Limited (Hitachi, Ltd.)
• Original Assignee: Hitachi Construction Machinery Company Limited (Hitachi, Ltd.)
• Inventors: Tatsuno, Yukihiro, Ichimura, Kazuhiro
• Granted Patent: US 7,398,648 B2
• Time in Patent Office: Days
• US Class Current: 60/493
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 2520/105 Longitudinal acceleration
• CPC Class Codes: B60W 30/18072 Coasting
• CPC Class Codes: F15B 11/0445 with counterbalance valves, e.g. to prevent overrunning or for braking
• CPC Class Codes: F15B 2211/20546 variable capacity
• CPC Class Codes: F15B 2211/30525 Directional control valves, e.g. 4/3-directional control valve
• CPC Class Codes: F15B 2211/329 actuated by fluid pressure
• CPC Class Codes: F15B 2211/40507 with constant throttles or orifices
• CPC Class Codes: F15B 2211/40584 the flow control means arranged in parallel with a check valve
• CPC Class Codes: F15B 2211/45 Control of bleed-off flow, e.g. control of bypass flow to the return line
• CPC Class Codes: F15B 2211/46 Control of flow in the return line, i.e. meter-out control
• CPC Class Codes: F15B 2211/50518 using pressure relief valves
• CPC Class Codes: F15B 2211/50545 using braking valves to maintain a back pressure
• CPC Class Codes: F15B 2211/5151 being connected to a pressure source and a directional control valve
• CPC Class Codes: F15B 2211/5153 being connected to an output member and a directional control valve
• CPC Class Codes: F15B 2211/55 for limiting a pressure up to a maximum pressure, e.g. by using a pressure relief valve
• CPC Class Codes: F15B 2211/6054 using shuttle valves
• CPC Class Codes: F15B 2211/6316 the pressure being a pilot pressure
• CPC Class Codes: F15B 2211/633 representing a state of the prime mover, e.g. torque or rotational speed
• CPC Class Codes: F15B 2211/6355 having valve means
• CPC Class Codes: F15B 2211/6651 : Control of the prime mover, e.g. control of the output torque or rotational speed
• CPC Class Codes: F15B 2211/6654 : Flow rate control
• CPC Class Codes: F15B 2211/7058 : Rotary output members
• CPC Class Codes: F15B 2211/76 : Control of force or torque of the output member
• CPC Class Codes: F16H 2059/6876 : the motor speed
• CPC Class Codes: F16H 59/22 : Idle position
• CPC Class Codes: F16H 59/40 : Output shaft speed
• CPC Class Codes: F16H 61/4148 : Open loop circuits
• CPC Class Codes: F16H 61/4157 : Control of braking, e.g. preventing pump over-speeding when motor acts as a pump
• CPC Class Codes: F16H 61/431 : Pump capacity control by electro-hydraulic control means, e.g. using solenoid valves

Abstract

The present invention includes a hydraulic pump 10 driven by a prime mover 1, a traveling motor 12 driven with pressure oil delivered from the hydraulic pump 10, a control valve 11 for traveling that controls a flow rate of the pressure oil delivered from the hydraulic pump 10 to the traveling motor 12, a counterbalance valve 13 switched in response to a motor load pressure supplied via the control valve 11, that generates a braking pressure at a conduit L1A or L1B disposed on a return side of the traveling motor 12 as the load pressure becomes lower, an overspeed detection means 42 for detecting an overspeed state in the traveling motor 12, and a motor overspeed inhibiting means 50 for inhibiting rotation of the traveling motor 12 if the overspeed detection means 42 detects an overspeed state in the traveling motor 12 until a braking pressure is generated through a switchover at the counterbalance valve 13 and the traveling motor 12 is no longer in the overspeed state.

Claims

1. A travel control device for a hydraulically driven vehicle, comprising:

a hydraulic pump driven by a prime mover;

a traveling motor driven with pressure oil delivered from the hydraulic pump;

a control valve for traveling that controls a flow rate of the pressure oil delivered from the hydraulic pump to the traveling motor;

a counterbalance valve switched in response to a motor load pressure supplied via the control valve, that generates a braking pressure at a conduit disposed on a return side of the traveling motor as the load pressure becomes lower;

an overspeed detection means for detecting an overspeed state in the traveling motor; and

a motor overspeed inhibiting means for inhibiting rotation of the traveling motor if the overspeed detection means detects an overspeed state in the traveling motor until a braking pressure is generated through a switchover at the counterbalance valve and the traveling motor is no longer in the overspeed state.

2. A travel control device for a hydraulically driven vehicle according to claim 1, further comprising:

a rotation speed detection means for detecting a rotation speed of the traveling motor, wherein;

the overspeed detection means detects the overspeed state when the motor rotation speed detected by the rotation speed detection means is equal to or greater than a predetermined value.

3. A travel control device for a hydraulically driven vehicle according to claim 1, further comprising:

an acceleration detection means for detecting an acceleration of the traveling motor, wherein;

the overspeed detection means detects the overspeed state when the motor speed is equal to or higher than a specific level and the motor acceleration detected by the acceleration detection means is equal to or greater than a predetermined value.

4. A travel control device for a hydraulically driven vehicle according to claim 2, wherein:

the motor overspeed inhibiting means is a prime mover rotation speed reducing means for reducing a rotation speed of the prime mover to a greater extent when the detected motor rotation speed is at a higher level.

5. A travel control device for a hydraulically driven vehicle according to claim 2, wherein:

the hydraulic pump is a variable displacement hydraulic pump; and

the motor overspeed inhibiting means is a pump displacement angle reducing means for reducing a displacement angle of the hydraulic pump to a greater extent when the detected motor rotation speed is at a higher level.

7. A travel control device for a hydraulically driven vehicle according to claim 3, wherein:

the motor overspeed inhibiting means is a prime mover rotation speed reducing means for reducing a rotation speed of the prime mover to a greater extent when the detected motor acceleration is at a higher level.

8. A travel control device for a hydraulically driven vehicle according to claim 3, wherein:

the hydraulic pump is a variable displacement hydraulic pump; and

the motor overspeed inhibiting means is a pump displacement angle reducing means for reducing a displacement angle of the hydraulic pump to a greater extent when the detected motor acceleration is at a higher level.

6. A hydraulically driven vehicle that comprises a drive control device, wherein:

the travel control device comprises;

a hydraulic pump driven by a prime mover;

a traveling motor driven with pressure oil delivered from the hydraulic pump;

a control valve for traveling that controls a flow rate of the pressure oil delivered from the hydraulic pump to the traveling motor;

a counterbalance valve switched in response to a motor load pressure supplied via the control valve, that generates a braking pressure at a conduit disposed on a return side of the traveling motor as the load pressure becomes lower;

an overspeed detection means for detecting an overspeed state in the traveling motor; and

a motor overspeed inhibiting means for inhibiting rotation of the traveling motor if the overspeed detection means detects an overspeed state in the traveling motor until a braking pressure is generated through a switchover at the counterbalance valve and the traveling motor is no longer in the overspeed state.