Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
2002-01-22
2003-11-11
Lavinder, Jack (Department: 3683)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C303S113500, C303S122000, C188S359000, C188S355000
Reexamination Certificate
active
06644760
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a hydraulic pressure control device for a vehicle in which a proportional pressure control valve having a built-in spool valve is actuated by the force applied to the brake pedal to adjust (or amplify) the hydraulic pressure for the wheel brakes to a proper pressure, and more specifically a hydraulic pressure control device in which even if a pressure source including a power-driven pump fails so that the supply of hydraulic pressure therefrom has stopped, the brakes can be applied, and a brake device which uses it to improve travel safety.
A so-called brake-by-wire type vehicle brake device has been developed in which in order to electrically control the braking force applied to the vehicle, the hydraulic pressure generated by the brake operation by the driver is converted to an electric signal and the hydraulic pressure generated in the power line (that is, pressure source including a power-driven pump) is adjusted to a value corresponding to the electric signal before supplied to the wheel brakes.
Also, a proportional pressure control valve suitable for use with such a brake-by-wire type brake device has been developed and actually used.
FIG. 10
shows an example. In this proportional pressure control valve
60
, a spool valve
62
is inserted in a housing
61
having an input port
61
a
, an output port
61
b
and a discharge port
61
c
to selectively connect the output port
61
b
to the input port
61
a
or the discharge port
61
c
by driving the spool valve
62
with a magnetic force generated by activating a coil
63
a
of a solenoid
63
and to adjust the degree of opening of passages defined between a shoulder portion on the outer periphery of the spool valve
62
and the edge of each port.
The input port
61
a
is connected to a pressure source
67
having a power-driven pump P and a pressure accumulator Acc. Also, the output port
61
b
is connected to wheel brakes
68
and the discharge port
61
c
is connected to a reservoir
69
. By changing over the connection of these ports by the spool valve
62
, the wheel brake pressure is increased and decreased, and in some cases, the output port
61
b
is separated from both the input port
61
a
and discharge port
61
c
to hold the wheel brake pressure.
The spool valve
62
has a difference in area between its pressure-bearing surfaces opposite to each other, the difference being equal to the sectional area of a pin
65
inserted in a pin hole
64
. Thus, assuming that the hydraulic pressure introduced through the input port
61
a
is P, the force of a return spring
66
is F, the current supplied to the coil
63
a
is I, and the sectional area of the pin
65
is S, the thrust force acting against the spool valve
62
balances at a position where the following formula is met:
P·S+F=a·I
2
(a is a constant)
and the spool valve
62
stops at such a position.
The above formula is replaced with
P
=(
a·I
2
−F
)/
S
In this formula, a and S are constants. If the spring constant is ignored, F can also be regarded as a constant. Thus, the hydraulic pressure P is proportional to the square of the current I and corresponds to an electric signal controlling the current I, i.e. the brake operating amount that generates the signal.
The present inventors considered actuating the above-described proportional pressure control valve with a brake pedal.
A device in which the operating force of the brake pedal is used to drive the spool is disclosed e.g. in Japanese patent publication 2000-326839. In the device, only in an emergency (when electric line fails), the spool is adapted to be driven by the brake pedal, while in a normal state the spool is driven electrically. Thus, electronic control is indispensable, so that the device is complicated.
In contrast, in the device the present inventors have conceived, the brake pedal is coupled to the spool valve so that not only in an emergency but in a normal state, the spool is driven by the operating force to the brake pedal. Thus, in case braking force control is not necessary such as during regenerative blending braking, a braking force corresponding to the brake operating amount can be generated without electronic control.
With the device the present inventors are considering or the device disclosed in Japanese patent publication 2000-326839, the supply of hydraulic pressure to the wheel brakes is made only from the pressure source having a power-driven pump. Thus, while the pressure source is normal, even if the electric line should fail, it is possible to apply the brakes by driving the spool valve with the brake pedal. But if the pressure source fails and the supply of hydraulic pressure therefrom stops, the brakes would not work.
An object of this invention is to increase travel safety of the vehicle by eliminating such a trouble.
SUMMARY OF THE INVENTION
According to this invention, there is provided a hydraulic pressure control device comprising a housing formed with an input port, an output port and a discharge port, and a proportional pressure control valve and a hydraulic pressure generator mounted in the housing, the proportional pressure control valve having a spool valve and a return spring for biassing the spool valve, the spool valve bringing the output port into communication with the discharge port in a non-operated state, bearing hydraulic pressure on its opposed pressure-bearing surfaces having a difference in area, and moving to a balance point where the sum of the hydraulic pressure and the force of the return spring balances with an external force applied opposite thereto to change over connections of the output port to the input port and the discharge port, adjust the degree of opening of fluid passages, and adjust the hydraulic pressure at the output port to a value corresponding to the external force, the hydraulic pressure generator combined with the proportional pressure control valve, the hydraulic pressure generator comprising a second piston for transmitting a force to the spool valve through a second spring, a first piston for transmitting a force to the second piston through a first spring and an output port, wherein the first piston receives the brake pedal force as the external force, pressurizes and outputs brake fluid introduced into a fluid chamber between the first piston and the second piston.
Also, there is provided a brake device for a vehicle comprising the hydraulic pressure control device mentioned above, a pressure source connected to the input port of the hydraulic pressure control device, wheel brakes in a first line connected with said output port, wheel brakes in a second line connected with the output port of the hydraulic pressure generator, and a copy valve actuated by the hydraulic pressure difference between the first line and the second line to open and close a passage extending from the hydraulic pressure generator to the wheel brakes in the second line, the copy valve having a piston bearing fluid pressure in the first line on one side for pressurizing the wheel brakes in the second line, and a reservoir connected to the discharge port of the proportional pressure control valve, wherein brake fluid is supplied from the reservoir to a fluid chamber between the first and second pistons of the hydraulic pressure generator, and during failure of the pressure source, the hydraulic pressure generated in the hydraulic pressure generator is supplied to the wheel brakes in the second line.
The hydraulic pressure generator may be one in which the spring force of its first spring is greater than the sum of the force of the second spring and its sliding resistance or one in which a reactive force spring for returning the brake pedal is disposed between the second piston and the proportional pressure control valve. With the former hydraulic pressure generator, it is possible to lighten the force applied to the brake pedal during failure of the power source by providing a pressure-bearing unit having a piston for bearing the hydraulic pressure of the pressure source
Nakano Keita
Nishikimi Makoto
Yoshino Masato
Greenblum & Bernstein P.L.C.
Lavinder Jack
Sumitomo (SEI) Brake Systems, Inc.
Williams Thomas
LandOfFree
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