Hydraulic Drive System Steering Responsivity Control
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Solution Overview
Problem
Work vehicles face challenges in maintaining high steering responsivity while traveling at high speeds, as high responsivity to steering handle operations can lead to difficulty in maintaining a straight line, and low oil viscosity due to temperature affects steering performance.
Innovation Solution
A hydraulic drive system with a steering actuator and work machine actuator connected in parallel to a hydraulic pump, featuring a steering control valve, actuator control valve, meter-in compensator, bleed-off compensator, vehicle state detecting unit, and controller to adjust the flow rate of hydraulic oil to the steering actuator based on vehicle state, reducing responsivity during high-speed travel and varying oil temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the steering control valve moves quickly to improve steering responsivity, then the steering actuator responds rapidly to steering handle operations, but it becomes difficult to perform fine adjustment for straight traveling during high-speed travel
Solution Approach 1:
The patent applies dynamics by making the meter-in compensator's opening degree variable based on vehicle speed. At low speeds, the compensator maintains a smaller opening for fine adjustment capability, while at high speeds, it increases the opening to provide sufficient flow rate for responsive steering. This dynamic adjustment resolves the contradiction between steering responsivity and fine adjustment capability across different operating conditions.
Solution Approach 2:
The patent changes the flow rate parameter of hydraulic oil supplied to the steering actuator based on vehicle speed detection. The controller adjusts the meter-in compensator's opening degree to modify the flow rate, providing high flow rate (high responsivity) at high speeds and controlled flow rate (fine adjustment) at low speeds. This parameter change strategy resolves the contradiction by adapting the system behavior to operational context.
2Ease of operation
If the meter-in compensator maintains a small opening degree to enable fine adjustment, then fine control is achievable, but the flow rate of hydraulic oil supplied to the steering actuator becomes insufficient during high-speed travel
Solution Approach 1:
The meter-in compensator dynamically adjusts its opening degree based on vehicle speed detected by the vehicle state detecting unit. During high-speed travel, the compensator opens wider to increase hydraulic oil flow rate for rapid steering response. During low-speed operation, it maintains a smaller opening for fine adjustment capability. This dynamic behavior resolves the contradiction between fine adjustment capability and steering response speed.
Solution Approach 2:
The system changes the flow rate parameter of hydraulic oil by adjusting the meter-in compensator's opening degree according to vehicle speed. At high speeds, the opening degree increases to provide sufficient flow rate for responsive steering. At low speeds, the opening degree decreases to enable fine adjustment. This parameter adaptation resolves the contradiction by optimizing flow rate for each operating condition.
3Speed
If the opening degree of the meter-in compensator is increased to improve steering responsivity, then hydraulic oil flows quickly to the steering actuator, but it becomes difficult to perform fine adjustment for straight traveling
Solution Approach 1:
The patent makes the meter-in compensator's opening degree dynamic rather than fixed. The controller adjusts the opening degree based on vehicle speed: at high speeds, a larger opening provides rapid steering response; at low speeds, a smaller opening enables fine adjustment for straight traveling accuracy. This dynamic adjustment resolves the contradiction between steering responsivity and straight traveling accuracy.
Solution Approach 2:
The system changes the flow rate parameter by adjusting the meter-in compensator's opening degree according to operational conditions. During high-speed travel, the opening degree increases to improve steering responsivity. During straight traveling at low speeds, the opening degree decreases to enable fine adjustment precision. This parameter change strategy resolves the contradiction by adapting flow rate to operational context.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively adjusts steering responsivity according to vehicle state, allowing for stable straight-line travel at high speeds and mitigating the impact of temperature on steering performance.
Implementation Method 1
a meter-in compensator which is provided in a meter-in passage connecting the hydraulic pump to the steering control valve, and is configured to adjust an opening degree of the meter-in passage in such a manner that the opening degree of the meter-in passage is increased as the opening degree of the spool of the steering control valve is increased
Implementation Method 2
a bleed-off compensator which is provided in a bleed-off passage connecting the hydraulic pump to the actuator control valve and is configured to adjust an opening degree of the bleed-off passage in such a manner that the opening degree of the bleed-off passage is reduced with an increase in a pressure of the hydraulic oil flowing to the steering actuator
Implementation Method 3
A work vehicle includes a hydraulic drive device to drive these actuators... a steering actuator and a work machine actuator are connected in parallel to a hydraulic pump... the hydraulic oil is supplied to the work machine actuator while securing the flow rate of the hydraulic oil which is required for the steering device
Data Source
Figure 1
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Figure 3
AI summary
A hydraulic drive system (1) including a meter-in compensator (37) and a bleed-off compensator (42) comprises a plurality of sensors (64 to 68), a controller (62), and an outlet pressure switching valve (61). The controller (62) determines whether or not the state of a wheel loader (2) which is detected based on the signals output from the sensors (64 to 68) meets a predetermined steering limiting condition. When the controller (62) determines that the state of the wheel loader (2) meets the steering limiting condition, it outputs a command signal to the outlet pressure switching valve (61). The outlet pressure switching valve (61) reduces the flow rate of the hydraulic oil flowing to steering cylinders (18L, 18R), in response to the command signal in such a manner that the flow rate becomes lower than that corresponding to the operation amount of a handle of a steering device (35).