Axial Piston Pump Layout With Detachable Servo Unit
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Solution Overview
Problem
Existing hydraulic pump systems in hydrostatic transmissions lack flexibility in layout and standardization, as they often require integrated servo units and expensive servomechanisms, limiting their adaptability to various vehicle designs and increasing costs.
Innovation Solution
An axial piston hydraulic pump design that allows for a detachable servo unit, enabling separate placement from the hydraulic motor, with a port block configuration that minimizes size and cost by incorporating a charge relief valve within the housing, and includes parallel charge check valves to reduce the port block's dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the hydraulic pump is integrated with the hydraulic motor in a combined HST assembly, then component parts are reduced and cost is lowered, but layout freedom is limited and adaptability to various vehicle designs is reduced
Solution Approach 1:
The HST system is segmented into separate hydraulic pump and hydraulic motor components, allowing independent placement and flexible layout configuration while maintaining functional integration through hydraulic fluid connections. The pump unit and motor unit can be positioned independently within the vehicle chassis.
Solution Approach 2:
The hydraulic pump is designed with a universal mounting interface that accepts both servo units and non-servo actuators, enabling the same pump assembly to be used across different vehicle configurations and applications. The externally open ports provide universal connectivity for hydraulic fluid transmission.
2Measurement precision
If a servo unit is integrated into the hydraulic pump housing, then control precision is improved, but device complexity and cost increase due to expensive servomechanisms
Solution Approach 1:
The servo unit is extracted from the hydraulic pump housing as a separate, detachable component. This allows the pump to function with simplified mechanics while enabling optional servo control when precision is required. The externally threaded bore provides a standardized interface for attaching the servo unit or alternative actuators.
Solution Approach 2:
The control system configuration is made dynamic and adjustable, allowing the hydraulic pump to operate with different control mechanisms (servo unit, non-servo actuator, or manual control) depending on the application requirements. This enables cost optimization by selecting simpler control for less demanding applications.
3Strength
If the port block is made thicker to ensure sufficient strength for incorporating the charge relief valve, then structural strength is improved, but device size and cost increase
Solution Approach 1:
The charge relief valve is nested within the hydraulic pump housing structure, with the valve body positioned inside the housing cavity rather than requiring external mounting space. This nested arrangement allows the port block to maintain sufficient strength with reduced thickness, as the housing provides additional structural support.
Solution Approach 2:
The port block and housing are merged into an integrated structure where the housing serves dual functions as both the pump enclosure and structural reinforcement for the port block. This combination eliminates the need for excessive port block thickness, reducing overall size while maintaining strength.
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
This design enhances layout flexibility, reduces costs, and allows for easy exchange of servo units with non-servo actuators, improving the hydraulic pump's adaptability to different vehicle designs and reducing manufacturing complexity.
Implementation Method 1
The movable swash plate is rotatably supported by the housing and abuts against the plungers. The plurality of plungers are fitted into respective cylinders formed in the cylinder block so as to reciprocally slide parallel to the drive shaft.
Implementation Method 2
The port block includes a pair of main fluid passages connecting the respective externally open ports to the cylinders in the cylinder block. The port block is provided with a charge relief valve for regulating a hydraulic pressure in the fluid-charge passage.
Data Source
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AI summary
A housing of a hydraulic pump is configured to have a servo unit detachably attached thereto so as to control tilt direction and angle of its movable swash plate. A port block is formed therein with a pair of main ports and, and a pair of main fluid passages and fluidly connecting respective main ports and to cylinders in its cylinder block. Main ports are used to have respective external pipes connected thereto so as to fluidly connect the hydraulic pump to a hydraulic motor disposed outside of the hydraulic pump, thereby constituting a hydrostatic transmission.