Hydraulic Pressure Correction During CVT Pump Switching
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Solution Overview
Problem
The hydraulic pressure supplied to the hydraulic operation part in a hydraulic control device decreases temporarily when switching from a second state to a first state due to the stop or low rotation state of the second pump, affecting the transmission ratio of the continuously variable transmission and vehicle traveling performance.
Innovation Solution
A hydraulic control device with a pressure adjusting valve that adds a correction hydraulic pressure to the hydraulic pressure discharged from the control valve, maintaining a constant value until the second pump stops, to prevent temporary pressure drops and ensure stable oil flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the second pump is stopped or operates at low rotation, then energy consumption is reduced, but hydraulic pressure temporarily decreases affecting transmission performance
Solution Approach 1:
The control device performs preliminary action by adding correction hydraulic pressure before the second pump actually stops or reduces rotation. The ECU detects the stop/low rotation state and immediately adds correction pressure through the pressure adjusting valve, preventing the temporary pressure drop that would otherwise occur during the transition to first state operation.
Solution Approach 2:
The invention changes the hydraulic pressure parameter by adding a predetermined correction pressure value to the control valve's discharge pressure. This parameter modification ensures that even when the second pump stops or operates at low rotation, the hydraulic pressure supplied to the hydraulic operation part remains stable and sufficient for proper transmission operation.
2Productivity
If the bypass valve switches to supply first oil when second pump discharge decreases, then the hydraulic operation part receives oil, but temporary hydraulic pressure decrease occurs
Solution Approach 1:
When the bypass valve switches to supply first oil from the first pump, the control device simultaneously adds correction hydraulic pressure to maintain stable pressure. The ECU detects the switching condition and adjusts the pressure adjusting valve to add predetermined correction pressure, ensuring that the hydraulic operation part receives continuous oil supply without temporary pressure drops that would affect transmission performance.
3Reliability
If correction hydraulic pressure is added continuously, then hydraulic pressure stability is maintained, but the second pump may return to operation unnecessarily
Solution Approach 1:
The control device uses feedback control where the ECU continuously monitors the rotation state of the second pump and the operation state of the bypass valve. Based on this feedback, the ECU determines when to add or stop adding correction hydraulic pressure. The correction pressure is added only when the second pump is in stop or low rotation state, and stopped when the second pump resumes normal operation, preventing unnecessary pump activation while maintaining pressure stability.
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 solution effectively prevents temporary hydraulic pressure decreases, maintaining stable transmission ratios and improving vehicle performance by ensuring early restoration of hydraulic pressure and reducing the risk of the second pump returning to operation during correction.
Implementation Method 1
a control that adds a correction hydraulic pressure of a predetermined amount to a hydraulic pressure of the oil discharged from the another valve (68a or 68b) is performed
Implementation Method 2
When the discharge amount (flow rate) of the second oil from the second pump exceeds the flow rate (discharge amount of the first oil from the first pump) of the first oil passing through the bypass valve, the hydraulic pressure (line pressure PH) in the downstream oil passage of the bypass valve becomes higher than the hydraulic pressure (output pressure P1) in the upstream oil passage. In this way, the bypass valve is closed
Data Source
AI summary
In a hydraulic control device switchable between a first state in which a first oil is supplied from a first pump to a hydraulic operation part via a bypass valve and a second state in which the first oil supplied from the first pump is pressurized by using the second pump and the pressurized first oil is supplied, as a second oil, to the hydraulic operation part, control that adds a correction hydraulic pressure of a predetermined amount to the hydraulic pressure of the oil discharged from a valve for adjusting the pressure of the oil supplied to the hydraulic operation part is performed when the second state is switched to the first state due to a stop or a low rotation state of the second pump.