Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle subsystem or accessory control
Reexamination Certificate
1998-10-05
2001-04-17
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle subsystem or accessory control
C701S036000, C701S038000, C701S039000
Reexamination Certificate
active
06219601
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. HEI 10-6946 filed on Jan. 16, 1998 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a vehicle height adjust control apparatus and method for setting a vehicle height to a target vehicle height by supplying hydraulic fluid to and discharging it from hydraulic actuators provided between a vehicle body and wheels.
2. Description of Related Art
A vehicle height adjust control apparatus described in Japanese Patent Application Laid-Open No. Hei 2-3515, for example, includes a hydraulic actuator for changing a vehicle height by hydraulic fluid supplied and discharged, a supply-discharge device made up of a hydraulic pump, a control valve for supplying hydraulic fluid into and discharging it from the hydraulic actuator, a vehicle height detection device for detecting an actual vehicle height, and a supply-discharge control device for controlling the operation of the supply-discharge device so as to eliminate deviation of the detected actual vehicle height from a predetermined target vehicle height. The apparatus controls and sets the actual vehicle height to a target vehicle height by supplying hydraulic fluid to and discharging it from the hydraulic actuator using the supply-discharge device.
In this vehicle height adjust control apparatus, various problems occur depending on various factors, such as the construction of the hydraulic pump or the control valve, the control of the supply-discharge device by the supply-discharge control device, the condition of the hydraulic fluid, the condition of a battery, and the like. Specifically, if the hydraulic pump is operated at a very low hydraulic fluid temperature, an excessively great load is caused on the hydraulic pump. This adversely affects the durability of the hydraulic pump because at a very low temperature the fluidity of hydraulic fluid is very low and the viscosity thereof is very high. At a very high hydraulic fluid temperature, the viscosity of hydraulic fluid becomes very low, so that the ejecting performance of the hydraulic pump decreases. Therefore, it becomes necessary to operate the hydraulic pump for longer periods. Long-time operation of the hydraulic pump further increases the hydraulic fluid temperature, thereby adversely affecting the durability of the hydraulic pump. This temperature-dependent problem is significant, particularly if the hydraulic pump is a gear pump.
If stopping of the hydraulic pump and switching of the control valve from a open state to an close state are simultaneously performed to stop the supply of hydraulic fluid from the hydraulic pump to the hydraulic actuator, hydraulic fluid may impact the control valve because the hydraulic pump will not immediately stop ejecting hydraulic fluid, due to the inertia of an electrical motor or the like. Such impact on the control valve produces impact noise and degrades the durability of the hydraulic system, including the hydraulic pump, the control valve and the like. This problem becomes more significant if the hydraulic fluid temperature is lower and the hydraulic fluid viscosity is higher, and if the hydraulic fluid ejecting pressure produced by the hydraulic pump is higher.
If the control valve is an electromagnetic on-off valve, a size reduction of the control valve results in a reduction in the number of turns of the coil, so that it may become difficult for the coil to provide a sufficiently great attraction force for drawing a plunger. Furthermore, since a temperature increase correspondingly increases the resistance of the coil, the coil may not be provided with a current sufficient to attract the plunger if the hydraulic fluid temperature is high. In addition, an insufficient current through the coil for attracting the plunger also results from a voltage reduction of the battery that energizes the coil.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to improve the durability of a vehicle height adjust control apparatus and ensure reliable operation of the apparatus by solving the aforementioned various problems of the conventional art.
According to a first aspect of the invention, there is provided a vehicle height adjust control apparatus including a hydraulic actuator capable of increasing and reducing a vehicle height using hydraulic fluid, and a hydraulic pump for ejecting hydraulic fluid. The vehicle height adjust control apparatus further includes a supply/discharge device for enabling the supplying of the hydraulic fluid to the hydraulic actuator and the discharging of the hydraulic fluid from the hydraulic actuator, a vehicle height detection device for detecting a vehicle height, a supply/discharge control device for controlling operation of the supply/discharge device so as to eliminate a deviation of the vehicle height detected by the vehicle height detection device from a predetermined target vehicle height, a fluid temperature detection device for detecting a temperature of the hydraulic fluid, and a suspending control device for suspending control of the operation of the supply/discharge device by the supply/discharge control device if the temperature of the hydraulic fluid detected by the fluid temperature detection device is equal to or lower than a first predetermined temperature or equal to or higher than a second predetermined temperature.
If the temperature of the hydraulic fluid is equal to or lower than the first predetermined temperature or equal to or higher than the second predetermined temperature, the operation of the supply/discharge device, including the hydraulic pump, is stopped by the suspending control device. Therefore, by suitably setting the first and second predetermined temperatures, the operation of the hydraulic pump provided in the supply/discharge device will be stopped if the temperature of the hydraulic fluid becomes very low or very high (or if the viscosity of the hydraulic fluid becomes very high or very low so that the fluidity thereof is very low or very high). Therefore, the durability or service life of the supply/discharge device, including the hydraulic pump, is increased.
According to another aspect of the invention, there is provided a vehicle height adjust control apparatus including a hydraulic pump for ejecting hydraulic fluid into a supply/discharge device, an accumulator for accumulating hydraulic fluid ejected by the hydraulic pump, a fluid temperature detection device for detecting a temperature of the hydraulic fluid, and a suspending control device for suspending the supplying of the hydraulic fluid from the hydraulic pump to the accumulator if the temperature of the hydraulic fluid detected by the fluid temperature detection device is equal to or lower than a first predetermined temperature or equal to or higher than a second predetermined temperature. Therefore, if the temperature of the hydraulic fluid is equal to or lower than the first predetermined temperature or equal to or higher than the second predetermined temperature, the operation of the hydraulic pump for supplying the hydraulic fluid to the accumulator is stopped by the suspending control device. Consequently, by suitably setting the first and second predetermined temperatures, the durability or service life of the supply/discharge device, including the hydraulic pump and the accumulator, is increased, as in the construction described above.
According to still another aspect of the invention, there is provided a vehicle height adjust control apparatus including a hydraulic actuator capable of increasing and reducing a vehicle height using hydraulic fluid, and a hydraulic pump for ejecting the hydraulic fluid. The apparatus further includes a control valve provided in a fluid passage between the hydraulic pump and the hydraulic actuator, for opening and closing the fluid passage, a vehicle height detection device for detecting a vehicle height, a supply/discharge control device for
Harada Kenji
Hashimoto Yoshiyuki
Kanatani Masaki
Sato Atushi
Shono Shoichi
Cuchlinski Jr. William A.
Marc-Coleman Marthe Y.
Oliff & Berridg,e PLC
Toyota Jidosha & Kabushiki Kaisha
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