Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
2000-11-13
2001-11-20
Graham, Matthew C. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C303S119300
Reexamination Certificate
active
06318818
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of compensating for the temperature dependence of a coil resistance of a valve coil in a hydraulic unit, and a device for controlling the pressure in a wheel brake.
BACKGROUND OF THE INFORMATION
The main types of vehicle dynamics control systems are anti-lock brake and traction control systems (ABS/TCS). Control systems of this type are used to influence the longitudinal dynamics of the vehicle. These concepts also include control systems for motor vehicles that are used to influence the vehicle's transverse dynamics. These, for example, include control systems for controlling a quantity describing the vehicle yaw rate (VSC/ESP system). A system of this type can, among other things, influence the steering performance of motor vehicles (for example, taking into account the yaw rate, steering angle, float angle, etc.).
A brake system that includes means for performing anti-lock braking and traction control functions is described in the article entitled “Antiblockiersystem und Antriebsschlupfregelung der 5. Generation” (Fifth-Generation Anti-lock Brake and Traction Control System), by Wolf-Dieter Jonner, Wolfgang Maisch, Robert Mergenthaler, and Alfred Sigl, published in ATZ Autmobiltechnische Zeitschrift 95, 1993, Vol. 11. The hydraulic valves and the pump elements used to build up and relieve pressure are combined into a hydraulic unit. Particularly in the case of traction control, it is desirable to know the temperature of the brake system (the hydraulic unit and thus the hydraulic system), in particular the temperature of the coils of the respective solenoid valves. Measures for taking into account the brake system temperature are not described for the conventional brake system.
Hydraulic units used in the vehicle stability control systems listed above (ABS, TCS, ESP, VSC) provide valves that can operate in either a linear or proportional fashion. The linearly settable pressure drop across the valve according to a characteristic function depends on the valve current. However, the valve coil resistance is greatly dependent on coil temperature. Therefore, the valve current and pressure drop when setting a specific valve voltage are also greatly dependent on temperature. To avoid inaccuracies that this can produce in vehicle stability control, a conventional method measures the temperatures at the respective coils and takes into account a corresponding correction factor on the basis of the measured temperatures in controlling the coils. However, it has proven to be extremely cumbersome to measure the temperature at all valve coils.
To obtain reliable measurement results, it is especially important to use, for example, valves with current-controlled valve output stages. However, such valve output stages, and the valves equipped with them, are relatively expensive.
Corrective measures to compensate for temperature influences are conventional, for example, for solenoid valves used to control the metering of fuel in an internal combustion engine. Thus, an internal combustion engine in which the time of activation of the solenoid valve can be corrected as a function of solenoid valve temperature is described from German Patent Application No. 196 06965.
SUMMARY
An object of the present invention is to provide an easy-to-use and economical temperature detection method for solenoid valves in a hydraulic unit.
According to an embodiment of the method the temperature of a second solenoid valve is compensated for, based on a quantity of a first solenoid valve. It is no longer necessary to perform the cumbersome temperature detection at each individual solenoid valve. The solenoid valve at which the temperature is measured is the only one that must be equipped with relatively expensive temperature detection means. The remaining solenoid valves can have a less complicated and therefore more economical design.
According to another embodiment of the method, temperature influences during the activation of a second solenoid valve that is provided in a hydraulic unit located in a vehicle brake system are taken into account, i.e. eliminated, by determining at least one first quantity that describes the performance of a first solenoid valve, determining a temperature quantity that describes the temperature of the second valve as a function of the at least one first quantity, and taking into account the temperature quantity during activation of the second valve. The coil voltage, coil current, coil resistance and/or coil temperature of the first solenoid valve is suitably used as the first quantity.
According to this method for taking into account, i.e. eliminating, temperature influences, the coil temperature of the first solenoid valve does not have to be determined explicitly if a quantity describing the temperature of the second valve can be determined as a function of the coil voltage, coil current, or coil resistance, for example.
The coil temperature of the first solenoid valve is suitably determined by measuring a coil voltage and a coil current, with a temperature-dependent resistance of the coil being calculated or determined from this measurement. The coil temperature can be easily obtained on the basis of a valve coil resistance of this type, for example with the help of the conventional relationship between the resistance and temperature of copper wire, which is typically used as the coil material.
According to an advantageous embodiment of the method according to the present invention to compensate for temperature dependence, the coil current of the first solenoid valve is controlled using a current-controlled valve output stage. A current-controlled valve output stage of this type makes it possible to set the coil current very accurately so that a voltage applied to the coil can also be determined with a high degree of accuracy. The current control arrangement can be used to compensate for the temperature at this first valve. Overall, this leads to very precise resistance and temperature measurement values, respectively. The fact that, according to the present invention, only the first solenoid valve needs to be provided with a current-controlled valve output stage of this type is, specially advantageous. The remaining solenoid valves (in particular the second solenoid valve), at which the temperature is not measured directly, can be equipped with more economical, for example switching, valve output stages.
The coil voltage measured at the solenoid valve is suitably transmitted to the electronic control unit on a check-back line of the solenoid valve, for example by pulse width modulation.
REFERENCES:
patent: 41 07 978 (1992-09-01), None
patent: 43 37 133 (1995-05-01), None
patent: 196 06 965 (1997-08-01), None
patent: 199 20 448 (1999-12-01), None
patent: 0 538 600 (1994-11-01), None
patent: 0 933 274 (1999-08-01), None
Jonner et al., Wolf-Dieter, “Antiblockiersystem und Antriebsschlupfregelungder 5. Generation,” ATZ Automobiltechnische Zeitschrift, 95, vol. 11, 1993. Described in Specification.
Brachert Jost
Holl Eberhard
Graham Matthew C.
Kenyon & Kenyon
Robert & Bosch GmbH
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