Hill Hold Control Valve Pressure Threshold Strategy
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Solution Overview
Problem
Existing hill hold systems in motor vehicles are complex and costly due to the requirement of multiple sensors, including a sensor for determining road gradient and a pressure sensor for monitoring brake pressure, making them impractical for lower price categories.
Innovation Solution
A method and device that set a pressure threshold value at a control valve independently of the brake circuit pressure, allowing the valve to maintain brake pressure on the wheel brake, eliminating the need for a pre-pressure sensor by using gradient information and a stop light switch to detect brake application and vehicle standstill, with the pressure threshold value adjusted based on gradient and minimum brake pressure requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pre-pressure sensor is used to monitor brake pressure in the brake circuit, then the hill hold system can accurately maintain brake pressure, but the system complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the pre-pressure sensor from the hill hold system by using an alternative approach: setting the pressure threshold value directly at the control valve based on gradient information, thereby achieving brake pressure maintenance without the complex sensor-based monitoring system
Solution Approach 2:
The patent introduces a mediator approach by using the control valve itself to enforce the pressure threshold based on gradient data, rather than using a sensor to monitor pressure and then controlling the valve. This intermediary mechanism simplifies the system while maintaining functionality
2Reliability
If multiple sensors (gradient sensor and pressure sensor) are used to ensure accurate hill hold control, then the vehicle can be reliably kept at standstill, but the equipment cost increases
Solution Approach 1:
The patent removes the pressure sensor from the system by directly setting the pressure threshold at the control valve using gradient information, thereby reducing the number of sensors from two (gradient sensor and pressure sensor) to one (gradient sensor only)
Solution Approach 2:
The control valve is given a dual function: it not only controls brake pressure release but also actively enforces the pressure threshold based on gradient data, eliminating the need for separate pressure sensing and control components
3Device complexity
If the pressure threshold value is set independently of brake circuit pressure at the control valve, then the pre-pressure sensor can be eliminated, but the control system must accurately determine gradient information
Solution Approach 1:
The patent uses gradient information as an intermediary parameter to set the pressure threshold at the control valve, avoiding the need for direct pressure measurement while maintaining accurate hill hold control through the relationship between gradient and required brake pressure
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 approach simplifies and cost-reduces the hill hold system by eliminating the need for a pre-pressure sensor, ensuring the vehicle remains stationary without unintentional movement while allowing for efficient startup when driver intent is detected, thus enhancing safety and reducing equipment costs.
Implementation Method 1
set a pressure threshold value at a valve with the aid of which it is possible to maintain the brake pressure prevailing on one wheel brake, independently of the level of the brake pressure prevailing in the brake circuit
Implementation Method 2
If the differential pressure dropping at the valve is greater than the pressure threshold value, medium flows into the valve
Data Source
AI summary
A method is described for automatically keeping a motor vehicle at a standstill. The motor vehicle includes a braking system having a valve for limiting the brake pressure to a predefinable pressure threshold value. Gradient information and a pressure threshold value dependent on the gradient information are ascertained. The pressure threshold value is set at the valve as soon as the motor vehicle is at a standstill and the service brake is applied.