JP7199312B2 - Hydraulic servo device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic servo device that hydraulically operates a continuously variable transmission.

As a hydraulic servo apparatus having the above configuration, Patent Document 1 discloses a double-acting servo cylinder that controls the swash plate angle of a hydrostatic continuously variable transmission. Arrangements are described with proportional control valves for supplying and draining oil.

In Patent Document 1, a potentiometer detects the depression amount of a shift pedal, a swash plate angle sensor detects the swash plate angle, and when the shift pedal is depressed, a proportional control valve is operated based on a detection signal from the potentiometer. By doing so, the servo cylinder is operated. Further, when the servo cylinder is operated, the swash plate angle is fed back by the swash plate angle sensor so that the servo cylinder is controlled to operate by an amount corresponding to the depression amount.

JP 2010-234863 A

In a configuration that controls a pair of electromagnetic control valves (proportional control valves in Patent Document 1) as described in Patent Document 1, if the electromagnetic control valves fail, the servo cylinder cannot be properly controlled, and the driver's An unintended running speed may also be set.

For these reasons, there is a need for a hydraulic servo apparatus that can prevent the servo cylinder from greatly operating even when the electromagnetic control valve that controls the double-acting servo cylinder fails.

The characteristic configuration of the hydraulic servo apparatus according to the present invention includes a double-acting servo cylinder that operates a continuously variable transmission, a pair of control passages that individually communicate with two oil chambers of the servo cylinder, and a pair of an electromagnetic control valve provided in each of the pair of control passages for individually supplying the hydraulic oil from the hydraulic pump to the control passage; a pair of on-off valves arranged in the flow paths of the pair of control flow paths for individually controlling the flow of hydraulic oil in the flow paths; and a drain flow path communicating with the pair of control flow paths, The on-off valve closes one of the control flow paths corresponding to the on-off valve when the pressure in the control flow path is less than the set value, and closes the on-off valve when the pressure reaches the set value or more. The corresponding one of the control flow paths is opened, and when one of the pair of on-off valves closes one of the control flow paths, the on-off valve closes the other control flow path in association with the closing. When one of the pair of on-off valves opens one of the control flow paths, the opening of the control flow path is linked to the opening of the other control flow path. The drain passage is opened, and the on- off valve is held in a closing position for closing one of the control passages by a spring biasing force when the pressure in the control passage is less than the set value, and the control passage is an on-off valve body that operates to an open position to open one of the control flow paths against the spring biasing force when the pressure of the valve reaches the set value or more, and the on-off valve body is in the closed position and a drain portion that closes the drain passage communicating with the other control passage when the control passage is in the open position, and connects the drain passage communicating with the other control passage to the discharge side when the control passage is in the open position. There is a point.

According to this characteristic configuration, when the hydraulic oil is supplied from the hydraulic oil pump to one of the control flow paths by the electromagnetic control valve, the pressure of the hydraulic oil supplied to the control flow path causes the control flow path to be prepared. Then, the on-off valve is opened, and hydraulic oil is supplied to one oil chamber of the servo cylinder. When the servo cylinder operates by supplying hydraulic fluid to one of the oil chambers in this way, the hydraulic fluid discharged from the other oil chamber passes through the drain passage that communicates with the other control passage. is discharged from the on-off valve which is in the open state.
In this configuration, when the working oil cannot be discharged, such as when one of the solenoids of the pair of electromagnetic control valves is broken, the on-off valve of the control flow path that cannot discharge the working oil is kept closed. As a result, the working oil is not discharged from the oil chamber of the servo cylinder , and the malfunction of the servo cylinder is not caused.
In addition, according to this, when the hydraulic oil is supplied to the control flow path, the pressure of the hydraulic oil opens the on-off valve body, and the hydraulic oil can be supplied from the control oil path to one of the oil chambers of the servo cylinder. becomes. In conjunction with this, the drain portion of the on-off valve body enables the flow of hydraulic oil discharged from the other oil chamber to the drain passage. This activates the servo cylinder. On the other hand, when neither of the pair of electromagnetic control valves operates, hydraulic fluid does not flow through either of the pair of control passages or the pair of drain passages, and the servo cylinder is restrained.
Therefore, a hydraulic servo apparatus is constructed in which even if an electromagnetic control valve for controlling a double-acting servo cylinder fails, the servo cylinder does not operate significantly.

As a configuration in addition to the above configuration, the on-off valves are accommodated in a pair of on-off valve holes formed in a block-shaped valve housing, and the valve housing has a pair of control passages and a pair of drain passages. and the pair of opening/closing valve holes may be arranged at points symmetrical with respect to a predetermined central point of the valve housing.

According to this, a pair of on-off valve holes are formed in a block-shaped material forming a valve housing, an on-off valve is inserted into each of the on-off valve holes, and a pair of control flow paths and a pair of valves are formed in the block-shaped material. The on-off valve unit can be formed by forming the drain passage of . In particular, when forming an on-off valve hole in a block-shaped material, the block-shaped material is fixed to a machine tool table or the like so that it can rotate about the center point, and a single on-off valve hole is formed by drilling with a tool such as a drill. A pair of on-off valve holes can be formed without arranging the tools at different positions by forming the openings, then rotating the table by 180°, and then drilling again using the same tool.

As a configuration in addition to the above configuration, a pair of opening and closing valve holes are formed in the valve housing in a parallel posture, and the opening and closing valve has a supply side port capable of sending hydraulic oil to the oil chamber; a drain side port capable of discharging the above, the valve housing includes a first combined flow path that allows the supply side port of one of the on-off valves and the drain side port of the other of the on-off valves to communicate with each other; A second composite flow path is formed to communicate the supply side port of the on-off valve and the drain side port of one of the on-off valves, and the first composite flow path communicates with one of the oil chambers. The two combined flow paths may communicate with the other oil chamber.

According to this, the pair of composite flow paths has the functions of a control flow path and a drain flow path. The valve is opened, and along with this opening, hydraulic oil is supplied from one of the composite flow paths (for example, the first composite flow path) from the supply side port to one of the oil chambers of the servo cylinder. In addition, when one of the on-off valves is open in this way, the hydraulic oil discharged from the other oil chamber of the servo cylinder flows into the other composite flow path (for example, the second composite flow path), and the opening/closing valve in the open state It is discharged from the drain side port of the valve. By forming a pair of composite flow paths in the valve housing in this way, it is not necessary to form a pair of control flow paths and a pair of drain flow paths between the valve housing and the servo cylinder. In addition, the processing steps for forming the flow path can be reduced.

1 is a hydraulic circuit diagram of a continuously variable transmission and a servo device; FIG. FIG. 4 is a cross-sectional view of the electromagnetic proportional pressure reducing valve in a state of shutting off hydraulic oil; FIG. 4 is a cross-sectional view of the electromagnetic proportional pressure reducing valve in a state of supplying hydraulic oil; FIG. 4 is a cross-sectional view of a valve housing;

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.
[Basic configuration]
FIG. 1 shows a hydrostatic continuously variable transmission A that transmits the driving force of an engine E to a transmission case 1 for traveling by continuously changing the speed, and a hydraulic servo device that operates the continuously variable transmission A by hydraulic pressure. B shows the hydraulic circuit.

The continuously variable transmission A and the hydraulic servo device B are provided in a vehicle such as a tractor. The continuously variable transmission A is operated so as to increase the running speed in the reverse direction.

[Continuously variable transmission]
As shown in FIG. 1, the continuously variable transmission A includes a variable displacement hydraulic pump P driven by an engine E, and a hydraulic motor M for transmitting driving force to a transmission case 1 for traveling. The continuously variable transmission A includes a pair of drive oil passages 2 for supplying hydraulic oil from a hydraulic pump P to a hydraulic motor M. By adjusting the amount of hydraulic oil sent from the hydraulic pump P, the hydraulic motor The driving speed of M is controlled to realize the setting of the running speed of the vehicle.

The continuously variable transmission A includes a charge pump 3 driven by an engine E. Hydraulic oil sent from the charge pump 3 is supplied to a pair of drive oil passages 2 via a charge circuit 4 . The charge circuit 4 includes a plurality of relief valves and a pair of check valves, and supplies hydraulic fluid to the drive oil passage 2 when the pressure in the drive oil passage 2 is reduced due to leakage.

The hydraulic pump P is of an axial plunger type having a plurality of plungers. By setting the angle of a swash plate (not shown) (swash plate angle), the forward speed of the hydraulic motor M is controlled and the hydraulic motor and reverse speed control.

By setting the swash plate to a preset neutral position, hydraulic oil does not flow through the pair of drive oil passages 2, the hydraulic motor M stops, and the vehicle stops running. In this continuously variable transmission A, by tilting the swash plate in one direction from the neutral position, hydraulic oil flows to the forward side in the pair of drive oil passages 2, and the vehicle body can move forward. On the other hand, by tilting the swash plate in the other direction, hydraulic oil flows to the reverse side in the pair of driving oil passages 2, thereby enabling the vehicle body to move backward.

[Hydraulic servo device]
The hydraulic servo device B includes a double-acting servo cylinder 10 for setting the swash plate angle. An electromagnetic proportional pressure reducing valve 20 (an example of an electromagnetic control valve) for supplying hydraulic oil from a hydraulic hydraulic pump 12 to the passage 11 is provided.

Further, in the hydraulic servo device B, an on-off valve 30 is provided in the flow path of the control flow path 11 that supplies hydraulic oil from the electromagnetic proportional pressure reducing valve 20 to the oil chamber 10 s of the servo cylinder 10 . The on-off valve 30 is closed when the pressure in the control flow path 11 is less than the set value, and is opened when the pressure is equal to or higher than the set value, so that the flow of hydraulic oil in the pair of control flow paths 11 is individually controlled. to control. A drain passage 13 that communicates with the pair of control passages 11 is connected to the drain side port 8 of the on-off valve 30 .

FIG. 1 shows a drain channel 13 branched from the pair of control channels 11 and an on-off valve 30 provided in each channel of the pair of control channels 11 . The circuit is shown expanded for easy understanding of the function with the flow path 13 . That is, the pair of on-off valves 30 are accommodated in the valve housing 5 shown in FIG. doing. The composite channel F will be described later.

The servo cylinder 10 has a piston 10b slidably accommodated in a cylinder 10a, a piston rod 10c connected to the piston 10b is linked to a swash plate of the hydraulic pump P, and a neutral spring 10d biasing the piston rod 10c to a neutral position. It has

In this servo cylinder 10, an oil chamber 10s is formed inside the cylinder 10a at a position sandwiching the piston 10b. With this configuration, when the pressure acting on the pair of oil chambers 10s is reduced, the biasing force of the neutral spring 10d returns the piston 10b to the neutral position, and the swash plate is operated to the preset neutral posture. .

[Hydraulic servo device: Electromagnetic proportional pressure reducing valve]
As shown in FIGS. 2 and 3, the electromagnetic proportional pressure reducing valve 20 has a sleeve 22 fitted in a case 21 and a spool 23 slidably accommodated in the sleeve 22. A solenoid portion 24 is provided outside the case 21 .

The sleeve 22 includes a pump port 22p to which hydraulic oil is supplied from the hydraulic oil pump 12, a supply port 22a to send the hydraulic oil to the control flow path 11 (see FIG. 1), and a tank port 22t to discharge the hydraulic oil. ing. The spool 23 has a first land portion 23a that controls the flow of hydraulic fluid from the pump port 22p to the supply port 22a, and a second land portion 23b that controls the flow of hydraulic fluid from the supply port 22a to the tank port 22t. I have.

As shown in FIG. 2, when the electromagnetic proportional pressure reducing valve 20 is in an OFF state in which current is not supplied to the electromagnetic solenoid portion 24, the supply of hydraulic fluid from the pump port 22p is cut off, and hydraulic fluid from the supply port 22a is supplied to the tank port 22t. The spool 23 is held in a position for discharging to the. As a result, hydraulic fluid in the control flow path 11 is discharged from the tank port 22t.

When the electromagnetic proportional pressure reducing valve 20 is in the ON state for supplying current to the electromagnetic solenoid portion 24, as shown in FIG. Hydraulic oil supply from is supplied to the supply port 22a. As a result, hydraulic fluid from the hydraulic fluid pump 12 is supplied to the control flow path 11 .

The electromagnetic solenoid section 24 has a spring that holds the spool 23 in the OFF position shown in FIG. 2 when no current is supplied. Accompanying this increase, the amount of operation of the spool 23 is increased to enable an increase in the flow rate of hydraulic oil supplied to the control flow path 11 .

[Hydraulic servo device: on-off valve]
In the hydraulic servo device B, as shown in FIG. 4, a pair of on-off valves 30 are accommodated in a block-shaped valve housing 5, and a pair of composite flow paths F (first composite flow path) communicating with the on-off valves 30 are provided. Generic concept of the channel and the second composite channel) is formed. The valve housing 5, the pair of on-off valves 30, and the pair of composite flow paths F constitute an on-off valve unit.

That is, the valve housing 5 is rectangular when viewed in the direction shown in FIG. 4, and opening/closing valve hole portions 5a are formed in parallel side surfaces (left and right vertical walls of the valve housing 5 in FIG. 4). The on-off valve hole portions 5a are arranged parallel to each other, and are formed at points symmetrical with respect to the center point C shown in FIG. As a result, the on-off valve hole portions 5a are in a positional relationship in which they overlap with each other when the valve housing 5 is rotated by 180°.

The on-off valve 30 includes an on-off valve body 31 that is slidably inserted into the on-off valve hole 5a, a spring 32 that biases the on-off valve body 31 to the closed position, and seals the opening of the on-off valve hole 5a. It is provided with a plug 33 that is screwed together.

A supply opening 6 is formed in communication with the inner end position of the on-off valve hole portion 5a and a control flow path 11 to which hydraulic oil is supplied from the electromagnetic proportional pressure reducing valve 20, and a drain is formed near the outer end of the on-off valve hole portion 5a. An opening 7 is formed. On the inner circumference of the on-off valve hole portion 5a, there are a drain side port 8 capable of discharging the working oil of the composite flow path F to the drain opening 7, and a supply side port capable of supplying the working oil from the supply opening 6 to the composite flow path F. 9 are formed.

As shown in FIG. 4, the on-off valve body 31 has a drain space 31a (an example of a drain portion) that can communicate with the drain opening 7 via a groove-shaped portion formed on the outer periphery.

A pair of composite flow paths F are formed in a parallel posture toward the inside from one end surface (the upper wall portion of the valve housing 5 in FIG. 4) orthogonal to the side surface of the valve housing 5 . Also, the pair of composite flow paths F individually communicate with the pair of oil chambers 10s.

In this valve housing 5, the composite flow path F on one side (left side of the figure) is an example of a first composite flow path, and the composite flow path F on the other side (right side of the figure) is an example of a second composite flow path. there is In addition, one composite flow path F (first composite flow path) is connected to the supply side port 9 of the on-off valve 30 on one side (upper side in FIG. 4) and the drain side of the on-off valve 30 on the other side (lower side in FIG. 4). It communicates with port 8. Similarly, the other composite flow path F (second composite flow path) is the drain side port 8 of the on-off valve 30 on one side (upper side in FIG. 4) and the supply port 8 of the on-off valve 30 on the other side (lower side in FIG. 4). It communicates with the side port 9 .

With this configuration, when hydraulic oil is not supplied to the supply opening 6 of any of the on-off valves 30, the on-off valve body 31 is held in the closed position by the biasing force of the spring 32 (spring biasing force). Thus, when the on-off valve body 31 is in the closed position, hydraulic oil is not supplied to the control flow path 11 communicating with the oil chamber 10s of the servo cylinder 10, and the drain opening 7 and the drain side port 8 are closed. are maintained in a closed state in which they are out of communication with each other.

On the other hand, when hydraulic oil is supplied to the supply opening 6 of one of the on-off valves 30 (the upper side in FIG. 4), the pressure of the hydraulic oil causes the on-off valve element 31 to open against the biasing force of the spring 32. As a result of moving to the position, the hydraulic oil from the supply side port 9 is delivered to one composite flow path F (first composite flow path) (on the left side in the figure). When the on-off valve body 31 is moved to the open position in this way, the drain side port 8 communicates (opens) with the drain opening 7 via the drain space 31a. Hydraulic oil is discharged from the

When the on-off valve 30 is opened in this manner, hydraulic oil is supplied to one oil chamber 10 s of the servo cylinder 10 and is discharged from the drain opening 7 of the on-off valve 30 from the other oil chamber 10 s. Therefore, the operation of the servo cylinder 10 is realized. Further, when the hydraulic oil is supplied to the supply opening 6 of the other (lower side in FIG. 4) on-off valve 30, the supply side port 9 of the other on-off valve 30 is connected to the other composite flow path F (second composite flow path). flow path), and the hydraulic oil in one of the composite flow paths F is discharged from the drain opening 7 of the on-off valve 30, so that the servo cylinder 10 can be operated in the opposite direction.

In particular, by providing the pair of on-off valves 30 in this way, for example, when the electromagnetic proportional pressure reducing valve 20 fails and falls into a state where hydraulic oil cannot be supplied, the on-off valve 30 is maintained in a closed state. Hydraulic oil cannot be discharged from the oil chamber 10s of the servo cylinder 10, and a phenomenon in which the servo cylinder 10 operates improperly is suppressed.

Thus, the composite flow path F has the functions of both the control flow path 11 and the drain flow path 13. As shown in FIG. are provided in the valve housing 5, the number of flow paths is reduced and the simplification of the configuration is realized. Incidentally, like the hydraulic circuit shown in FIG. 1, it is also possible to configure the servo device B so that the pair of drain passages 13 branched from the pair of control passages 11 are individually connected to the on-off valve 30 .

[Action and effect of the embodiment]
In this configuration, unlike the conventional technology in which a pair of electromagnetic proportional pressure reducing valves 20 (an example of an electromagnetic control valve) controls the supply and discharge of hydraulic oil to and from the oil chamber 10s of the servo cylinder 10, the oil chamber By providing the on-off valve 30 in the flow path of the control flow path 11 that communicates with 10s, when the electromagnetic proportional pressure reducing valve 20 fails, the inconvenience of improperly discharging hydraulic oil is eliminated, and as a result, the vehicle This eliminates the inconvenience of greatly fluctuating the running speed of the

In addition, by providing a pair of on-off valves 30 for the valve housing 5 and forming a pair of composite flow paths F, the number of flow paths formed in the valve housing 5 can be reduced to facilitate manufacture of the hydraulic circuit. I have to.

The block-shaped valve housing 5 is provided with a pair of on-off valves 30. In the on-off valve holes 5a formed at points symmetrical with respect to a predetermined center point C of the valve housing 5, It is configured to accommodate the on-off valve 30 . For this reason, for example, when forming the on-off valve hole portion 5a, the block-shaped material is fixed to a machine tool table or the like so as to be rotatable about the center point C, and a hole is drilled with a tool such as a drill. After the on-off valve hole is formed, the table can be rotated 180° and the same tool can be used to perform hole processing again. becomes.

[Another embodiment]
The present invention may be configured as follows other than the above-described embodiments (components having the same functions as those of the embodiments are given the same numbers and symbols as those of the embodiments).

(a) In order to configure the hydraulic servo device B, the control flow path 11 and the drain flow path 13 are formed as independent flow paths as shown in FIG. 1 described in the specification. Even with such a configuration, good operation is realized.

(b) It is not always necessary to use the valve housing 5 described in the specification, and it is also possible to support the pair of on-off valves 30 and the pair of electromagnetic proportional pressure reducing valves 20 (electromagnetic control valves) on a common member. be. With such a configuration, the control flow path 11 and the drain flow path 13 can be configured as independent oil paths, and a pair of composite flow paths F can also be formed.

(c) The object to be changed by the hydraulic servo device is not limited to the hydrostatic continuously variable transmission, and may be, for example, a belt continuously variable transmission (belt CVT).

INDUSTRIAL APPLICABILITY The present invention can be used for a hydraulic servo device that shifts a continuously variable transmission by hydraulic pressure.

5 Valve housing 5a Open/close valve hole 8 Drain side port 9 Supply side port 10 Servo cylinder 10s Oil chamber 11 Control flow path 12 Hydraulic oil pump 13 Drain flow path 20 Electromagnetic proportional pressure reducing valve (electromagnetic control valve)
30 On-off valve 31 On-off valve element 31a Drain part A Continuously variable transmission C Center point F Composite flow path (first composite flow path/second composite flow path)

Claims (4)

a double-acting servo cylinder that operates a continuously variable transmission;
a pair of control flow paths individually communicating with two oil chambers of the servo cylinder;
an electromagnetic control valve provided in each of the pair of control passages for individually supplying hydraulic oil from a hydraulic pump to the pair of control passages;
a pair of on-off valves arranged in the flow paths of the pair of control flow paths for individually controlling the flow of hydraulic fluid in the control flow paths in response to pressure changes in the pair of control flow paths;
and a drain channel communicating with the pair of control channels,
The on-off valve closes one of the control flow paths corresponding to the on-off valve when the pressure in the control flow path is less than the set value, and closes the on-off valve when the pressure reaches the set value or more. opening the corresponding one of the control channels;
When one of the pair of on-off valves closes one of the control flow paths, the on-off valve closes the drain flow path communicating with the other control flow path in association with this blockage, When one of the pair of on-off valves opens one of the control flow paths, the drain flow path communicating with the other control flow path is opened in association with this opening ,
The on-off valve is held at a closing position where one of the control passages is closed by a spring biasing force when the pressure in the control passage is less than the set value, and the pressure in the control passage is equal to or higher than the set value. an on-off valve body that operates to an open position that opens one of the control flow paths against the spring biasing force when the valve reaches
The on-off valve body closes the drain channel communicating with the other control channel when in the closed position, and discharges the drain channel communicating with the other control channel when in the open position. A hydraulic servo device having a drain that communicates with the side . The on-off valve is accommodated in a pair of on-off valve holes formed in a block-shaped valve housing, and a pair of the control passages and a pair of the drain passages are formed in the valve housing. the unit is made up of
2. The hydraulic servo device according to claim 1 , wherein the pair of open/close valve holes are arranged at points symmetrical with respect to a predetermined center point of the valve housing. A pair of opening/closing valve holes are formed in the valve housing in a parallel posture, and the opening/closing valve has a supply side port capable of sending hydraulic oil to the oil chamber and a drain side port capable of discharging hydraulic oil. and
In the valve housing, a first composite flow path for communicating the supply side port of one of the on-off valves and the drain side port of the other on-off valve, the supply side port of the other on-off valve and the one of the on-off valves. A second composite flow path is formed to communicate with the drain side port of the on-off valve, the first composite flow path communicates with one of the oil chambers, and the second composite flow path communicates with the other oil chamber. 3. The hydraulic servo device according to claim 2 . a double-acting servo cylinder that operates a continuously variable transmission;
a pair of control flow paths individually communicating with two oil chambers of the servo cylinder;
an electromagnetic control valve provided in each flow path of the pair of control flow paths for individually supplying hydraulic oil from a hydraulic pump to the pair of control flow paths to the two oil chambers;
an on-off valve disposed in the flow path of the pair of control flow paths for individually controlling the flow of hydraulic oil in the control flow paths in response to pressure changes in the pair of control flow paths;
and a drain channel communicating with the pair of control channels,
The on-off valve closes one of the control flow paths corresponding to the on-off valve when the pressure in the control flow path is less than the set value, and closes the on-off valve when the pressure reaches the set value or more. Having a single on-off valve body that opens the corresponding one of the control flow paths,
In the on-off valve, when one of the pair of on-off valve bodies closes one of the control flow paths, the on-off valve closes the drain flow path communicating with the other control flow path in association with this blockage. , when one of the pair of on-off valve bodies opens one of the control passages, the hydraulic oil supplied from the hydraulic oil pump through the electromagnetic control valve is A hydraulic servo device that supplies hydraulic fluid to one of the two oil chambers and discharges hydraulic fluid from the other of the two oil chambers by opening the drain passage that communicates with the other control passage in association with the opening.

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