Fluid handling – Systems – Multi-way valve unit
Reexamination Certificate
2001-10-12
2003-09-09
Fox, John (Department: 3753)
Fluid handling
Systems
Multi-way valve unit
C137S625340, C137S625690
Reexamination Certificate
active
06615868
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spool valve having notches provided in a step between a land and a groove in a spool.
2. Description of the Related Art
Such a spool valve is known from Japanese Utility Model Registration Nos. 2568961 and 2580463.
FIGS. 9 and 10
show the structure of a conventional pressure-controlling spool valve having a proximal end toward a direct drive-type linear solenoid
26
and a distal end away from the solenoid. An input port
13
, an output port
14
, a drain port
15
and a feedback port
16
are open along an axis, L, into a valve bore
12
which is circular in cross section and defined in a valve housing
11
. A spool
17
is slidably received in the valve bore
12
in the valve housing
11
and includes a first land
18
, a second land
19
, a third land
20
, a spring seat
21
extending from a distal end of the third land
20
, a first groove
22
defined between the first land
18
and the second land
19
, a second groove
23
defined between the first land
18
and the third land
20
, and a solenoid connection
24
extending from a proximal end of the second land
19
. The spool
17
is biased proximally by a valve spring
25
disposed between an end of the valve bore
12
and the spring seat
21
to coaxially abut against a distal end of an output rod
27
of the direct drive-type linear solenoid
26
for directly operating the spool
17
.
The first groove
22
in the spool
17
is connected to a proximal end of the first land
18
through a first step
28
. The first step
28
is perpendicular to the L-axis and axially disposed from the second land
19
through a second step
29
perpendicular to the L-axis. A predetermined number of (e.g., four) notches
30
are defined in the first step
28
by chamfers inclined at 30° with respect to the L-axis. When the spool
17
is in a position as shown in
FIG. 9
, the input port
13
is in communication with the output port
14
through the first groove
22
. When the spool
17
is moved proximally, to cut off the communication between the input port
13
and the first groove
22
, the output port
14
is brought into communication with the drain port
15
through the first groove
22
. A feedback pressure is applied to an oil chamber
31
provided distally of the third land
20
through the feedback port
16
. An oil chamber
32
defined between the first land
18
and the third land
20
communicates with the spool
17
through an oil bore
33
defined to connect the first groove
22
and the second groove
23
to each other.
In the spool valve having the above-described arrangement, when the linear solenoid
26
is excited to drive the output rod
27
distally, thereby urging the proximal end of the spool
17
against a repulsive force of the valve spring
25
, the input port
13
is put into communication with the output port
14
through the first groove
22
, such that the hydraulic pressure in the input port
13
is reduced depending on the opening degree thereof and delivered from the output port
14
. In this case, the amount of pressure changed in the output port
14
relative to the amount of change in position of the spool
17
can be decreased to inhibit a self-induced vibration of the spool
17
.
In the above prior art, the oil supplied from the input port
13
is passed through the notches
30
into the first groove
22
. The oil flows within the first groove
22
in the direction of the L-axis to collide with the second step
29
, thereby producing a flow force Fo for biasing the spool
17
proximally. The flow force Fo acts to oppose a distal drive force Fs generated by the linear solenoid
26
, causing the smooth operation of the linear solenoid
26
is obstructed. As a result, it is difficult to conduct a subtle hydraulic pressure control.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to ensure that the notches are defined in the spool to suppress the generation of a flow force, thereby stabilizing the operation of the spool valve, while preventing the generation of vibration.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided a spool valve comprising a valve housing having a valve bore, an input port and an output port axially spaced within the valve housing and opening into the valve bore. A spool is received in the valve bore for sliding movement in the axial direction. A first land and a second land are formed on the spool and spaced along the axis. A groove is defined in the spool and connected to the first and second lands through first and second steps. A notch is formed by a cutout portion from the first step. Also, an actuator drives the spool in the axial direction, so that the spool is driven by the actuator to put the input port into communication with the groove. When the input port is put into communication with the groove, a fluid flowing into the groove through the input port is discharged from the output port through the groove. The notch in the spool is formed so that a line, which extends through a communication zone provided upon communication of the notch with the input port, and which forms a free flow-in angle with respect to the axial direction, first intersects a bottom of the groove.
With the above arrangement, when the notch is put into communication with the input port, the fluid flowing into the groove through the communication zone does not collide with other portions of the spool, before colliding with the bottom of the groove. Therefore, the flow of the fluid in the axial direction, which causes the flow force applied to the spool, is suppressed and the load on the actuator is decreased. Thus, it is possible to decrease the flow force applied to the spool to achieve the stable operation of the spool valve, while preventing the self-induced vibration of the spool as a result of the notch cut out from the first step.
According to a second aspect and feature of the present invention, the free flow-in angle is 69°, which corresponds to a maximum free flow-in angle. Hence, even if the free flow-in angle becomes equal to 69°, corresponding to the maximum free flow-in angle in accordance with the shape of the notch and the opening degree of the input port, the flow force applied to the spool can be suppressed so as to be small.
According to a third aspect and feature of the present invention, the notch is formed in a direction perpendicular to the axis. The notch can be made by an end mill, resulting in enhanced workability.
According to a fourth aspect and feature of the present invention, there is provided a spool valve comprising a valve housing having a valve bore, an input port and an output port defined in the valve housing and spaced along an axis and opening into the valve bore. A spool is received in the valve bore for sliding movement in the axial direction. A first land and a second land are formed on the spool and spaced along the axis. A groove is defined in the spool and connected to the first and second lands through first and second steps, respectively. A notch is formed as a cutout portion from the first step, and an actuator for driving the spool in the axial direction, puts the input port into communication with the groove, so that a fluid flowing into the groove through the input port is discharged from the output port through the groove. A concave curved face is formed on a bottom of the groove. The notch in the spool is formed so that a line, which extends through a communication zone provided upon communication of the notch with the input port and which forms a free flow-in angle of a jet formed by the notch, points to a portion of the curved face displaced from a smallest-diameter portion toward the first step.
With the above arrangement, a fluid flowing into the groove upon communication of the notch in the spool with the input port, before colliding with the bottom of the groove, does not collide with other portions of the spool. Therefore, the momentum of the fluid causing a fl
Arent Fox Kintner & Plotkin & Kahn, PLLC
Fox John
Honda Giken Kogyo Kabushiki Kaisha
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