Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
2000-09-07
2003-05-13
Schwartz, Christopher P. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
Reexamination Certificate
active
06561597
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an electromagnetically driving part for use in a vehicle braking system for performing antilock control, traction control, and so on.
First, the schematic configuration of a vehicle braking system using an electromagnetically driving part according to the present invention will be described with reference to
FIG. 9. A
left front wheel brake Bfl, a right rear wheel Brr, a right front wheel brake Bfr and a left rear wheel brake Brl are disposed in the respective wheels. In addition, a pair of master cylinders M/C form a tandem master cylinder so as to output braking fluid pressure corresponding to the depression of a brake pedal. A braking fluid pressure controller
100
is provided among the brakes Bfl, Brr, Bfr and Brl and the tandem master cylinder M/C so as to be connected with the brakes Bfl, Brr, Bfr and Brl through a main fluid-pressure channel II and with the master cylinder M/C through a main fluid pressure channel I.
A braking fluid pressure controller
100
has four normally open electromagnetic valves Vofl, Vorr, Vofr and Vorl; four check valves Cofl, Corr, Cofr and Corl; four normally closed electromagnetic valves Vcfl, Vcrr, Vcfr and Vcrl; a pair of reservoirs Ra and Rb; a pair of reciprocating plunger pumps Pa and Pb; and a plurality of fluid pressure channels for making these members communicate with one another. The normally open electromagnetic valves Vofl, Vorr, Vofr and Vorl are provided as valve means corresponding to the left front wheel brake Bfl, the right rear wheel Brr, the right front wheel brake Bfr and the left rear wheel brake Brl. The four check valves Cofl to Corl are connected in parallel with the normally open electromagnetic valves Vofl to Vorl respectively so as to be opened to send brake fluid from the corresponding wheel brakes Bfl to Brl back to the master cylinder M/C when the input to the master cylinder M/C is released. The normally closed electromagnetic valves Vcfl to Vcrl are provided individually correspondingly to the respective wheel brakes Bfl to Brl. The reservoirs Ra and Rb are provided respectively correspondingly to the left front wheel brake Bfl and the right rear wheel Brr and to the right front wheel brake Bfr and the left rear wheel brake Brl. The reciprocating plunger pumps Pa and Pb are connected with the reservoirs Ra and Rb respectively.
In addition, the braking fluid pressure controller
100
has a single braking fluid pressure controller motor (hereinafter referred to as a “motor” simply) M for driving both the plunger pumps Pa and Pb, and an electronic control unit ECU for controlling the switching of the respective normally open electromagnetic valves Vofl to Vorl and the respective normally closed electromagnetic valves Vcfl to Vcrl between demagnetization and excitation.
Running conditions of a vehicle are fed into the electronic control unit ECU from vehicle velocity sensors (not shown) provided in the respective wheels, and so on. In accordance with the running conditions of the vehicle, the electronic control unit ECU controls each of the wheel brakes Bfl to Brl on the basis of any one of the following three commands In a pressure increasing mode, one of the normally open electromagnetic valves Vofl to Vorl corresponding to the wheel in question is demagnetized and opened, and one of the normally closed electromagnetic valves Vcfl to Vcrl corresponding to the wheel in question is demagnetized and closed. Thus, the pressure is increased by the fluid pressure applied from the master cylinder M/C to a wheel cylinder (not shown). In a retaining mode, one of the normally open electromagnetic valves Vofl to Vorl corresponding to the wheel in question is excited and closed, and one of the normally closed electromagnetic valves Vcfl to Vcrl corresponding to the wheel in question is demagnetized and closed. Thus, the fluid pressure is prevented from being transmitted from the master cylinder M/C to a wheel cylinder (not shown), so that the fluid pressure is retained. In a pressure reducing mode, one of the normally open electromagnetic valves Vofl to Vorl corresponding to the wheel in question is excited and closed, and one of the normally closed electromagnetic valves Vcfl to Vcrl corresponding to the wheel in question is excited and opened. Thus, the braking fluid is reserved temporarily from a wheel cylinder (not shown) into the reservoirs Ra and Rb, so that the fluid pressure is reduced to prevent the wheel from being in a lock state.
Then, the electronic control unit ECU drives the motor M so as to drive the pumps Pa and Pb. Thus, the braking fluid reserved temporarily in the reservoirs Ra and Rb is sent back to the master cylinder M/C.
Next, a background-art configuration of such a normally open electromagnetic valve used in a vehicle braking system will be described with reference to FIG.
10
. In
FIG. 10
, the reference numeral
10
represents a housing member or main body formed out of magnetic metal and shaped into a stepped cylinder. The housing member
10
is fitted into an electromagnetic valve fitting hole
12
formed in a substrate
11
, and attached to an inner surface of the fitting hole
12
while being sealed fluid-tightly by using a seal member
13
. The reference numeral
14
represents a snap ring for preventing the housing main body
10
from falling off. On one side of the housing main body
10
, a cylindrical fixed core
15
of an electromagnetic coil
30
is provided to extend toward the outside of the fitting hole
12
. The reference numeral
16
represents a communication path for making the aforementioned main fluid pressure channels I and II communicate with each other.
The reference numeral
17
represents a guide cylinder fixed to the fixed core
15
. The guide cylinder
17
is formed out of non-magnetic material, for example, stainless steel, into a thin closed-end cylinder the front end of which is formed as a spherical closed end. The guide cylinder
17
is engaged with the external surface of the fixed core
15
by welding. The reference numeral
18
represents a movable core which is slidably received in the guide cylinder
17
. A valve shaft
19
of non-magnetic material is inserted into the fixed core
15
slidably, and disposed so that a valve ball
20
provided as a valve body on the front end of the valve shaft
19
faces a valve hole
23
of a valve seat member
22
. The valve shaft
19
is always in a position where the valve ball
20
is detached from the valve seat member
22
by the energizing operation of an elastic body
24
, that is, in a position where the valve is opened. By the operation of magnetic flux generated when a current is made to flow through the electromagnetic coil
30
, the movable core
18
is sucked and driven so that the valve ball
20
abuts against the valve seat member
22
and reaches the position where the valve is closed.
FIG. 11
shows in magnification the portion where the guide cylinder
17
is engaged with the fixed core
15
. A press-in portion
15
a
is provided on the front end of the fixed core
15
so that the guide cylinder
17
is press-fitted onto the press-in portion
15
a
. After the guide cylinder
17
is press-fitted onto the press-in portion
15
a
, the guide cylinder
17
is welded with the press-in portion
15
a
from the external surface of the guide cylinder
17
and over the entire surface thereof so that the fixed core
15
and the guide cylinder
17
are seal-engaged with each other. A welded portion
40
shows a portion which was welded at the time of welding.
The process where the aforementioned welded portion
40
is formed will be described. The portion
40
is melted by heat at the time of welding, and metal vapor (gas) is generated then. There is a possibility that the metal vapor catches the molten metal and flies about when the metal vapor leaves the portion
40
. Thus, there appears a phenomenon that the flying metal (sputtering) adheres to the external surface of the guide cylinder
17
or the portion
40
is formed to swell over the external surfa
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