Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
2000-09-19
2001-11-27
Orberleitner, Robert L. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C251S129050, C303S152000
Reexamination Certificate
active
06322166
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to brake controllers for carrying out ABS control for optimally controlling the brake-fluid pressure so as to prevent wheel lock during braking, moment control for producing, when a vehicle falls in excessive oversteer or excessive understeer during steering, a braking force in wheels so as to form a yaw moment in the direction of restraining it, traction control for producing, when a traction of driving wheels becomes excessively large, a braking force for restraining it, automatic braking control for producing a braking force during automatic cruising as required, brake-by-wire control wherein a brake pedal and wheel cylinders are not directly connected through a hydraulic transfer system, etc., and solenoid-valve controllers suitably applied to the brake controllers.
BACKGROUND ART
Conventionally, solenoid valves are used for increasing or decreasing the brakefluid pressure in ABS control, automatic braking control, etc. The solenoid valves are known in the form of a valve having a valve hole switched between full closing and full opening by a plunger and a valve having the opening degree of a valve hole proportionally controlled by controlling a plunger at a middle position between full closing and full opening. Due to the control reliability, size reduction, cost reduction, etc., of the apparatus, the bake controllers typically use the former solenoid valve.
One of the known methods of controlling the valve hole at the middle opening degree as ensured in the latter valve by using a solenoid valve with two switching positions of full opening and full closing relies upon the use of pulse-width modulation control (hereafter refer to as PWM control)(see, for example, a Japanese document of JP-A 8-295225).
However, brake controllers for carrying out the above PWM control do not provide means for determining whether or not a desired brake-fluid pressure is formed by locating the plunger of solenoid valve in a desired position. Feedback as to whether or not the solenoid valve carries out a desired operation is ensured in accordance with an actual wheel velocity, such as, for example, whether or not the wheel velocity rises or lowers to a target value after implementation of brake-fluid pressure control.
In such a way, when brake-fluid pressure control was carried out based on feedback on the wheel velocity, a time was absolutely needed until the result of operation of the solenoid valve is shown on the wheel velocity, resulting in a problem that a time was needed until the wheel velocity converges at a desired slip ratio.
Therefore, an improvement in the control responsibility is demanded to shorten a time up to convergence of the wheel velocity, and thus to obtain improved control quality.
In connection with one means for solving this problem, the inventors of the application guessed that the control responsibility could be improved by detecting in which position the plunger of the solenoid valve is controlled with respect to a desired position, which is then feedback controlled.
A prior art technique for checking the position of the plunger of such solenoid valve switching two positions of full opening and full closing is known from means disclosed in a Japanese document of JP-A 5-211105.
This prior art technique is configured such that a coil of the solenoid valve is connected in series with a current detection resistance, and is supplied with power during a short period of time to the extent that the plunger is hardly moved so as to take out a current response waveform at both ends of the current detection resistance, based on which the position of the plunger is determined.
However, this prior art technique is a technique for carrying out a check when the solenoid valve is not actuated. If such check takes place while actuating the solenoid valve, a value of current passing through the coil is reduced due to series arrangement of the current detection resistance and the coil of the solenoid valve, reducing an attraction force of the coil. Thus, for obtaining a desired coil attraction force, an increase in the number of turns of the coil of the solenoid valve is needed compared with the case with no current detection resistance arranged, resulting in a problem of an increase in manufacturing cost and in size of the solenoid valve.
The present invention is made in view of the above conventional problem, and has as a first objective to achieve detection of the position of the plunger during actuation of the solenoid valve by means of a low-cost and small sized technique which requires no enhancement of an attraction force of the coil of the solenoid valve.
Moreover, in the solving technique, a second objective is to enhance the detection accuracy, and a third objective is to enhance the control responsibility of the plunger of the solenoid valve. Additionally, a fourth objective is to improve the control responsibility of the brake controllers, and thus the control quality by apply the solving technique to brake controllers which can implement ABS control or automatic braking control by carrying out PWM control for the solenoid valve.
SUMMARY OF THE INVENTION
For achieving the above first objective, the invention as specified in claim
1
provides, as shown in a claim corresponding view in
FIG. 1
, a solenoid-valve controller provided with a solenoid valve C which is switchable between the full closed state where a plunger a abuts on a sheet face b and the full open state where the plunger separates from the sheet face, and control means e for carrying out energization to a coil d for driving the plunger a of the solenoid valve C by pulse width modulation control, characterized in that there are arranged regenerative-current formation means f for forming a regenerative current in parallel with said coil d, that said control means e are arranged with regenerative-current detection means g for detecting the regenerative current, and that said control means e carry out said pulse width modulation control based on a detection value of the regenerative-current detection means g.
It is noted that in the solenoid-valve controller depicted in claim
1
, as specified in claim
2
, said control means may be provided with an opening-degree determination part for determining a position of the plunger with respect to said sheet face based on a response waveform of the regenerative current.
The invention as depicted in claim
1
operates as follows:
When the control means e carry out energization based on pulse width modulation control to the coil d, the regenerative current is formed by the regenerative-current formation means arranged in parallel with the coil d after cutoff of energization. This regenerative current has a characteristic varying with an air-gap amount corresponding to a distance between the plunger a and the sheet face b, and therefore, a detection value of the regenerative-current formation means correspond to a position of the plunger a. The control means e carry out pulse width modulation control in accordance with the position of the plunger. And when detecting the position of the plunger a in such a way, the regenerative-current formation means f are arranged in parallel with the coil d, resulting in no lowering of an attraction force of the coil d.
Thus, the position of the plunger a can be detected without increasing the number of turns of the coil d, obtaining the effect of enabling detection of the position of the plunger a by means which are low in cost and require no increase in attraction force of the coil d.
Moreover, in the solenoid-valve controller depicted in claim
2
, as specified in claim
3
, said control means are provided with an output-value correction part for correcting an output value of the pulse width modulation control in accordance with the position of the plunger determined in the opening-degree determination part.
According to the invention as specified in claim
2
, the inductance of the coil d varies in accordance with the position of the plunger a with respect to the sheet face b, in
Emura Jyunichi
Furuya Takayuki
Iwasaki Katsuya
Kakizaki Shinobu
Saita Norihiro
Foley & Lardner
Kramer Devon
Orberleitner Robert L.
Unisia Jecs Corporation
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