192 clutches and power-stop control – Clutches – Operators
Reexamination Certificate
2001-05-24
2002-12-31
Schwartz, Christopher P. (Department: 3683)
192 clutches and power-stop control
Clutches
Operators
C192S10900B
Reexamination Certificate
active
06499577
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a valve apparatus for controlling hydraulic pressure of a hydraulic pressure operated actuator usable for a clutch or a brake, and a method for controlling hydraulic pressure.
BACKGROUND ART
A hydraulic pressure control apparatus applicable for a clutch, disclosed in Japanese Laid-Open Patent publication No. 235732/1988, will be explained as an example of prior arts.
FIG. 9
shows a clutch cylinder
101
and a control valve
102
for controlling the clutch cylinder
101
in the above prior art. The control valve
102
includes a pressure control valve
103
for controlling clutch hydraulic pressure, and a flow rate detection valve
104
. The flow rate detection valve
104
is provided with a sensor section
105
for detecting filling and clutch pressure level. The pressure control valve
103
, the flow rate detection valve
104
and the sensor section
105
are stored in an integrated housing (
107
as shown in FIG.
10
). The pressure control valve
103
and the sensor section
105
are electrically connected to a controller
106
.
As shown in
FIG. 10
, the control valve
102
includes an input port
110
, an output port
111
and drain ports
113
and
114
. To the input port
110
of the control valve
102
, a hydraulic fluid supply line delivered from a pump (not shown) is connected. And, to the tip of the output port
111
, the clutch cylinder
101
(as shown in
FIG. 9
) is connected.
The pressure control valve
103
has a spool
115
, the right end of which comes in contact with a plunger
117
of a proportional solenoid. In the left end of the spool
115
, a piston
119
is installed and a spring
118
comes into contact with the spool
115
. In the spool
115
, a hydraulic chamber
120
close to the piston
119
and a hydraulic passage
121
communicated with the hydraulic chamber
120
are formed. Hydraulic pressure in the hydraulic passage
122
is applied, as a feedback pressure, to the hydraulic chamber
120
via a hydraulic passage
121
.
The flow rate detection valve
104
has a spool
125
, which defines hydraulic chambers
126
,
127
and
128
in the housing
107
. An orifice
130
is formed between the hydraulic chambers
127
and
128
. Springs
131
and
132
abut on the left and right ends of the spool
125
, respectively. The spool
125
is positioned at the neutral position as shown in
FIG. 10
under a resilient force of the springs
131
and
132
when pressure dose not rise in the hydraulic chambers
127
and
128
. When the piston
125
is at the neutral position, the hydraulic fluid, which has reached from the input port
110
to the flow rate detection valve
104
via the hydraulic passage
129
, remains in the hydraulic chamber
126
.
A detection pin
134
made of metal is disposed on the upper right side of the flow rate detection valve
104
. The pin
134
detects that the spool
125
is displaced in the rightward direction from the neutral position, as shown in
FIG. 10
, overcoming a resilient force of the spring
132
. The detecting pin
134
is mounted to the housing
107
by a cover
135
via an isolation sheet
136
. From the end of the detecting pin
134
, a lead wire
137
is extended, which is connected to a point “a” located between resistances R
1
and R
2
which are connected to each other in series. Between the resistances R
1
and R
2
, a predetermined magnitude of DC voltage V (for instance, 12 V) is applied. The end of the resistance R
2
and the housing
107
are grounded respectively. The sensor section
105
comprises these spring
132
, detecting pin
134
, and resistances R
1
and R
2
.
Next, operation of the hydraulic pressure control apparatus for a clutch having the above-mentioned structure will be explained referring to
FIG. 9
to FIG.
11
.
The horizontal axis shows a time t in FIG.
11
(A) to FIG.
11
(E). The vertical axis of FIG.
11
(A) shows current I commanded from the controller
106
, the vertical axis of FIG.
11
(B) shows a pump pressure P
0
, the vertical axis of FIG.
11
(C) shows hydraulic pressure (clutch pressure) P
1
in the hydraulic chamber
127
in the front of the orifice
130
, the vertical axis of FIG.
11
(D) shows hydraulic pressure (clutch pressure) P
2
in the hydraulic chamber
128
in the back of the orifice
130
, and the vertical axis of FIG.
11
(E) shows a output S (a voltage at a point “a”) of the sensor section
105
.
When a clutch is connected, at a time point t
1
in
FIG. 11
, the controller
106
operates so that trigger command current
1
I is supplied to the proportional solenoid
116
of the control valve
102
. Thereafter, the controller
106
operates so that the trigger command current I
1
is lowered to an initial pressure command current
10
and this condition is maintained until the termination of filling. The initial pressure command current
10
corresponds to an initial pressure Pa (as shown in FIG.
11
(D)) of the clutch pressure.
By supplying the trigger command current I
1
, the spool
115
of the pressure control valve
103
is displaced in the leftward direction so that the input port
110
is communicated with the hydraulic passage
122
. Consequentially, the hydraulic fluid delivered from the pump is introduced from the input port
110
into the hydraulic chamber
127
of the flow rate detecting valve
104
via the hydraulic passage
122
, and then into the hydraulic chamber
128
via the orifice
130
. At this moment, differential pressure (P
1
-P
2
) is generated between the hydraulic chambers
127
and
128
due to the existence of the orifice
130
. The differential pressure causes the spool
125
to be displaced in the leftward direction, so that the flow rate detecting valve
104
is opened. Therefore, the hydraulic fluid flows from the input port
110
into the hydraulic chamber
127
via the hydraulic passage
129
and the hydraulic chamber
126
, and then into the clutch via the orifice
130
, the hydraulic chamber
128
and the output port
111
. The hydraulic fluid continues to flow until a clutch-back becomes completely filled.
Here, when the spool
125
is positioned at the neutral position in
FIG. 10
, and, during a period in which the spool
125
is being displaced in the leftward direction from the neutral position, the spool
125
is parted away from the detecting pin
134
. Accordingly, the potential at the point “a” is a voltage V′, which is obtained by dividing the voltage V by the resistances R
1
and R
2
, as shown in FIG.
11
(E).
When the clutch-back is completely filled with the hydraulic fluid, the filling is terminated. At this time, since the hydraulic fluid stops flowing, there is no difference in pressures at the front and back of the orifice
130
(that is, P
1
=P
2
). At this moment, the spool
125
is displaced in the rightward direction by the spring
131
and a difference in the pressure receiving areas of the spool
125
result in the detecting pin
134
, once conducted to the housing
107
, being grounded via the spool
125
. The conduction is effected by displacement of the spool
125
due to shoot pressure generated at the termination of filling. And, the spool
125
returns to the neutral position in
FIG. 10
when the shoot pressure disappears. Accordingly, as shown in FIG.
11
(E), the potential at the point “a” is lowered to zero at a time point t
2
, and rises to V′ again. A detecting signal S showing the potential at the point “a” is inputted to the controller
106
, which determines the termination of filling from the potential rising at point “a”. At the termination of filling, the controller
106
operates so that the command current I for the clutch cylinder
101
is gradually increased from the initial pressure command current
10
(as shown in FIG.
11
(A)). Incidentally, the controller
106
operates so that the command current for a pre-stage clutch is lowered to zero at the determination of the termination of filling, as shown FIG.
11
(A) with a dashed line.
As the result, the clutch pressure is lowered from the shoot pressure to the in
Hasegawa Kaoru
Kitamoto Hiroaki
Shimada Kenjiro
Komatsu Ltd.
Schwartz Christopher P.
Wenderoth , Lind & Ponack, L.L.P.
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