Hydraulic Pump Suction Layout to Prevent Negative Pressure
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Solution Overview
Problem
In hydraulic systems for working machines, a negative pressure can be generated in the fluid passage connected to the suction port of the first hydraulic pump when the flow rate of hydraulic fluid discharged from the second hydraulic device becomes smaller than the flow rate of hydraulic fluid supplied to it, leading to unstable hydraulic fluid supply to the first hydraulic device.
Innovation Solution
A hydraulic system design that includes a first hydraulic pump, a first hydraulic device, a hydraulic fluid tank, a second hydraulic pump, a second hydraulic device, and a connecting fluid passage branching off from the second discharge fluid passage to the suction fluid passage, with a supplier to supply additional hydraulic fluid to the second discharge fluid passage, ensuring stable hydraulic fluid supply to the first hydraulic pump regardless of the second hydraulic device's actuation manner.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the second hydraulic device is actuated such that the flow rate of discharged hydraulic fluid becomes smaller than the supplied flow rate, then the second hydraulic device can maintain high pressure for effective work, but a negative pressure is generated in the fluid passage connected to the suction port of the first hydraulic pump, causing unstable hydraulic fluid supply
Solution Approach 1:
The patent introduces a third hydraulic pump as an intermediary device between the first hydraulic pump and the second hydraulic device. This third pump acts as a mediator that ensures stable hydraulic fluid supply to the first hydraulic pump's suction port by compensating for negative pressure conditions, thereby resolving the contradiction between maintaining high pressure in the second hydraulic device and ensuring stable supply to the first hydraulic pump.
Solution Approach 2:
The patent implements a beforehand cushioning mechanism by providing a third hydraulic pump that proactively compensates for potential negative pressure conditions in the fluid passage. This pump is configured to supply hydraulic fluid to the suction port of the first hydraulic pump in advance, preventing negative pressure from causing instability before it can affect the system's reliability.
2Adaptability or versatility
If the second hydraulic device operates with variable flow rate according to actuation manner, then it can adapt to different working conditions, but this causes fluctuation in the flow rate supplied to the first hydraulic pump, leading to unstable operation
Solution Approach 1:
The third hydraulic pump serves as a buffer intermediary that decouples the variable flow rate operations of the second hydraulic device from the first hydraulic pump. By positioning the third pump in the fluid passage and configuring it to maintain stable supply to the first pump's suction port, it absorbs the fluctuations caused by the second device's adaptability, thus protecting the first pump's stable operation.
Solution Approach 2:
The patent utilizes parameter changes by adjusting the operational parameters of the third hydraulic pump to compensate for flow rate variations from the second hydraulic device. The third pump's parameters (such as discharge flow rate) are dynamically adjusted to maintain constant supply conditions for the first hydraulic pump, thereby preserving stability while allowing the second device to maintain adaptability.
Data Source
AI summary
A hydraulic system for a working machine includes: a first hydraulic pump; a first hydraulic device; a hydraulic fluid tank; a first discharge fluid passage to allow hydraulic fluid discharged from the first hydraulic device to flow into the tank; a second hydraulic pump to suck fluid from the tank through a suction fluid passage; a second hydraulic device in which difference between flow rate of fluid from the second hydraulic pump device and that of discharged fluid changes according to actuation; a second discharge fluid passage connected to a suction port of the first hydraulic pump and allowing fluid discharged from the second hydraulic device to flow into the first hydraulic pump; a connecting fluid passage branching from the second discharge fluid passage and connected to the suction fluid passage between the tank and the second hydraulic pump; a supplier to supply fluid to the second discharge fluid passage.