Hydraulic Pump Feedback Valve for Cold-Start Pressure Limiting
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Solution Overview
Problem
Commercial vehicles require high drive output for variable pumps during start-up, especially during cold starts, due to increased hydraulic fluid viscosity, leading to increased energy consumption and load on the drive motor and starter motor.
Innovation Solution
A hydraulic assembly with a variable pump, feedback connector, and hydraulic valve device that includes a valve unit with shift positions to limit outlet pressure and discharge flow during start-up, reducing the power input required from the drive motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the adjustment control is set to maximum delivery position during start-up, then the hydraulic consumers receive sufficient flow, but the drive motor requires high output due to increased viscosity of cold hydraulic medium
Solution Approach 1:
The valve device is activated before the start-up procedure to pre-limit the outlet pressure and discharge flow of the variable pump. This preliminary action ensures that during cold start-up when hydraulic fluid viscosity is high, the pump does not attempt to deliver maximum flow, thereby reducing the power requirement of the drive motor while still providing sufficient hydraulic flow for consumers.
Solution Approach 2:
The valve device changes the operating parameters of the variable pump by limiting the outlet pressure and discharge flow during start-up. This parameter modification allows the pump to operate at reduced delivery conditions during cold start-up, matching the reduced capacity of the drive motor when hydraulic fluid viscosity is elevated, thus resolving the contradiction between required flow and available power.
2Quantity of substance
If the variable pump delivers maximum discharge flow during cold start-up, then hydraulic consumers are supplied, but energy losses increase due to high viscosity of the hydraulic medium
Solution Approach 1:
The valve device applies partial action by limiting the discharge flow to only what is necessary during start-up, rather than allowing maximum delivery. This partial flow limitation reduces the energy losses associated with pumping high-viscosity fluid at full capacity, while still providing sufficient hydraulic supply for consumers during the start-up phase.
3Power
If the outlet pressure is limited during start-up, then the power input of the variable pump is reduced, but the adjustment control must be influenced appropriately to maintain minimum discharge flow
Solution Approach 1:
The valve device utilizes feedback from the feedback connector, which is hydraulically connected to the adjustment control of the variable pump. This feedback mechanism ensures that when the valve device limits the outlet pressure during start-up, the adjustment control receives appropriate signals to maintain the pump at minimum discharge flow, thereby coordinating pressure limitation with flow maintenance to reduce power input while ensuring sufficient hydraulic supply.
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 solution reduces the output required by the drive motor during start-up, alleviating load on the motor and starter, and facilitating a successful cold start with lower energy losses, thus enhancing the efficiency and cost-effectiveness of the hydraulic system.
Implementation Method 1
limit or reduce the outlet pressure and/or the discharge flow, or the volumetric flow, of the variable discharge pump during a start-up procedure
Implementation Method 2
a feedback connector as an interface for pressure feedback from consumers
Data Source
AI summary
A hydraulic assembly for a commercial vehicle includes a supply connector which is hydraulically connected or connectable to a pump outlet of a hydraulic variable pump and a feedback connector The hydraulic assembly includes an adjustment control, which depends on an outlet pressure of the variable pump and on a reported pressure of the feedback connector, for adjusting the variable pump. A hydraulic valve device is disposed in the flow path between the feedback connector and the adjustment control. The valve device includes a valve unit which is effective as a hydraulic connection or interruption in the flow path, depending on a shift position. Moreover, the disclosure relates to a commercial vehicle having such a hydraulic assembly.