Hydraulic Control Device for CVT Idling Stop
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Solution Overview
Problem
Conventional hydraulic control devices for vehicles with idling stop function require larger electric pumps or accumulators to maintain high belt clamping pressure during reduced-speed travel, leading to increased size and potential cost issues, and struggle to maintain hydraulic pressure effectively during external disturbances.
Innovation Solution
A hydraulic control device that includes an electric pump directly supplying oil to a belt-type continuously variable transmission mechanism, with an accumulator that accumulates and discharges oil using the electric pump's pressure, and a pressure accumulation control valve to manage back pressure, reducing the size of both the pump and accumulator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the size of the electric pump or accumulator is increased to maintain high belt clamping pressure during idling stop at reduced speed, then the hydraulic pressure can be maintained under external disturbances, but the device size and cost increase
Solution Approach 1:
The accumulator pre-stores hydraulic oil at high pressure before external disturbances occur. When disturbances like sudden braking or road changes occur during idling stop, the pre-charged accumulator immediately supplies oil to maintain belt clamping pressure, eliminating the need to oversized the electric pump for peak demand scenarios.
Solution Approach 2:
The accumulator acts as an intermediary energy storage device between the electric pump and the CVT clutch. It decouples the continuous operation of the electric pump from the intermittent high-demand scenarios, allowing the pump to operate at reduced size while the accumulator handles peak pressure requirements during disturbances.
2Reliability
If the size of the electric pump or accumulator is increased to maintain high belt clamping pressure during idling stop at reduced speed, then the hydraulic pressure can be maintained under external disturbances, but the device size and cost increase
Solution Approach 1:
The accumulator pre-stores hydraulic oil at high pressure before external disturbances occur. When disturbances like sudden braking or road changes occur during idling stop, the pre-charged accumulator immediately supplies oil to maintain belt clamping pressure, eliminating the need to oversized the electric pump for peak demand scenarios.
Solution Approach 2:
The accumulator acts as an intermediary energy storage device between the electric pump and the CVT clutch. It decouples the continuous operation of the electric pump from the intermittent high-demand scenarios, allowing the pump to operate at reduced size while the accumulator handles peak pressure requirements during disturbances.
3Use of energy by moving object
If conventional hydraulic control devices are used with mechanical pump stopped during idling stop, then fuel economy improves, but hydraulic pressure supply becomes insufficient for high-speed operation
Solution Approach 1:
The mechanical pump driven by the engine is replaced with an electric pump during idling stop operations. This substitution allows the engine to remain off for fuel economy while the electric pump independently supplies hydraulic pressure to the CVT clutch, maintaining transmission control functionality without mechanical coupling to the engine.
Solution Approach 2:
The system changes the operating parameters of the hydraulic supply by switching from engine-speed-dependent mechanical pump operation to electrically-controlled pump operation. This allows independent control of hydraulic pressure supply from engine operation, enabling fuel economy during idling stop while maintaining sufficient pressure for CVT control through electric pump regulation.
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 configuration reduces the size of the electric pump and accumulator while maintaining sufficient belt clamping pressure, preventing slip during external disturbances and allowing for efficient idling stop function execution without significant size or cost increases.
Implementation Method 1
an electric pump that supplies oil to the belt-type continuously variable transmission mechanism
Implementation Method 2
an accumulator that accumulates and discharges oil using the oil supplied by the electric pump as an operating pressure
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A hydraulic control device 1 includes an electric pump 33 configured to supply oil to a belt-type continuously variable transmission mechanism 11 of a power transmission device 5 through a hydraulic path 36 based on driving of a motor 32, and an accumulator 44 configured to accumulate oil inside by using the oil supplied by the electric pump 33 and supplies the oil to a C1 control system 18 by discharging the accumulated oil through the hydraulic path 36. According to such a configuration, an increase in the sizes of the electric pump 33 and the accumulator 44 used for hydraulic control at the time of executing an idling stop function can be suppressed.