JPH09137838A - Steering clutch brake operation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an amount of oil leaking to an oil discharge port through the outer peripheral surface of a piston by a method wherein a cylinder member fitted in an oiltight manner in the inner peripheral surface of a cylinder case is located between the inner peripheral surface of a cylinder case and the outer peripheral surface of a piston and an opening part connected to the oil discharge port is formed therein. SOLUTION: When a piston 63 effects stroke within a cylinder case 64, viscosity of pressure oil in an oil pressure chamber between the bottom of a recessed part 64b and the inner end face of a piston 63 is reduced due to the increase of temperature and the pressure oil is about to leak through the inner and outer peripheral surfaces of the piston 63 to the outside of the cylinder case 64 but the leak is stopped by O-rings (b) and (c). The pressure oil leaking to the outer peripheral side of the piston 63 flows through the opening part 40 of a cylinder member 39 before the flow of it to the O-ring (b). But, when a brake is in an engaging state, since the same pressure oil as that in the recessed part 64b is exerted on the opening part 40, no leakage occurs. Further, when a brake is in a state to disengage a clutch, the opening part 40 is communicated with the tank side through an annular groove 65a, since the degree of the opening of the opening part 40 is reduced by a cylinder member 39, leaking pressure oil is reduced to a minimum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering clutch brake operating device for independently connecting / disconnecting power to / from a left and right crawler type traveling device and further applying a braking force to the crawler device on the disconnecting side. .

[0002]

2. Description of the Related Art Conventionally, with respect to a steering clutch / brake operating device, a steering shaft is horizontally mounted in a mission case, and a hollow cylinder case fixed to the inner wall of the mission case is provided on the outer periphery of the steering shaft. Position, an annular piston is arranged in the cylinder case, and pressure oil is selectively supplied from the direction switching valve to the oil supply port of the cylinder case, so that the piston is provided in the middle of the cylinder case. Slide the side clutch gear on the steering shaft away from the drive gear, and then operate to increase the pressure in the oil drain port, causing the piston to slide further from the oil drain port position. A mechanism for applying a brake to the side clutch gear is known. For example,
This is the same as the technique described in Japanese Patent Application Laid-Open No. 6-135353 by the same applicant.

[0003]

However, in the prior art, the following problems have occurred.
That is, in the conventional technique, the outer peripheral surface of the piston is installed so as to directly contact the inner peripheral surface of the cylinder case, and the piston is configured to slide in the cylinder case. When the temperature of the oil supplied to the cylinder case rises and the viscosity of the oil decreases, even if pressure oil is supplied to the oil supply port of the cylinder case by operating the directional control valve, Since the amount of oil leaking to the oil drain port provided on the inner peripheral surface increases, the piston does not generate enough force to pull the side clutch gear out of the drive gear, causing a problem that the straight-running state continues. I was doing it. In order to solve such a problem, the present invention reduces the amount of oil leak from the outer peripheral surface of the piston to the oil drain port of the cylinder case.

[0004]

The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described. The steering shaft is laid horizontally in the mission case, the hollow cylinder case fixed to the inner wall of the mission case is arranged on the outer periphery of the steering shaft, and the annular piston is arranged in the cylinder case. By selectively supplying pressure oil from the switching valve to the oil supply port of the cylinder case, the piston slides to the position of the oil discharge port provided in the middle of the cylinder case to drive the side clutch gear on the steering shaft. In the mechanism that separates the piston from the gear and then operates to increase the pressure of the oil drain port, the piston is slid further from the oil drain port position to apply braking to the side clutch gear. A cylindrical member 39 that is oil-tightly fitted to the inner peripheral surface of the cylinder case is provided between the surface and the outer peripheral surface of the piston, and the cylindrical member 39 has an opening connected to the oil discharge port. It is provided with a 40.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a side view of a combine equipped with the steering clutch brake operating device of the present invention, and FIG.
Is a skeleton diagram of a traveling power transmission mechanism including the steering clutch brake operating device of the present invention, FIG. 3 is a side sectional view of the steering clutch brake operating device of the present invention, FIG. 7 is an inner side view of the cylinder case 64 of the invention, FIG. 6 is an outer side view of the cylinder case 64, and FIG.
6 is a sectional view taken along the line YY of FIG. 6, FIG. 8 is a sectional view taken along the line XX of FIG. 5, FIG. 9 is a sectional view taken along the line ZZ of FIG. 5, and FIG. Fig. 1 is an overhead view of the cylindrical member 39
FIG. 1 is a hydraulic circuit diagram of the steering clutch brake operating device of the present invention.

FIG. 1 is a side view of the combine. The mission case 1 is arranged between the left and right crawler type traveling devices 53L and 53R. The traveling output shafts 35L and 35R are projected from the mission case 1 to the left and right,
The traveling device 53L is attached to the traveling output shafts 35L and 35R.
・ 53R drive sprockets 31L and 31R are fixed.

The power transmission mechanism in the mission case 1 will be described with reference to FIG. The driving force from the engine (not shown) is input to the input pulley 2a of the input shaft 2 via the V belt. The rotation input to the input pulley 2a is transmitted to a power output shaft 20 and a traveling output shaft 35L via a transmission unit described later.
-It is configured to output to 35R. First, the transmission mechanism from the input pulley 2a to the output pulley 20a of the power takeoff shaft 20 will be described.

On the input shaft 2 in the mission case 1,
The sub-transmission sliding body 3 is spline-engaged so as to be relatively non-rotatable and axially slidable. Further, the gear 4 is loosely fitted and installed. The sub-transmission slide body 3 is configured as a double gear including a gear portion 3b and a gear portion 3a. The gear portion 3b can be meshed with a fixed gear 9 on a counter shaft 6 that is erected on the lower side of the power transmission system. Also,
The gear portion 3 a can mesh with the fixed gear 8 on the counter shaft 6. Further, the gear portion 3a can be engaged with the internal tooth portion of the gear 4 on the input shaft 2. The gear 4 is constantly meshed with the fixed gear 7 on the counter shaft 6.

By slidingly operating the auxiliary transmission sliding body 3 by means of an auxiliary transmission shifter (not shown), high, medium, and low three-stage auxiliary transmission rotations can be obtained on the counter shaft 6. That is, when the gear portion 3b meshes with the fixed gear 9, the auxiliary shift becomes slower. When the gear portion 3a meshes with the fixed gear 8, the medium speed of the auxiliary shift is achieved. When the gear portion 3c engages with the inner tooth portion of the gear 4, the high speed of the auxiliary shift is achieved.

Two hydraulic clutch shafts 71 and 22 are installed on the lower side of the power transmission system of the counter shaft 6. On the hydraulic clutch shaft 71, the hydraulic clutch F1
F3 is installed, and hydraulic clutches F2 and R are installed on the hydraulic clutch shaft 22. In addition, the fixed gear 10 on the counter shaft 6 is loosely fitted on the hydraulic clutch shaft 71, and the hydraulic clutch F1 causes the hydraulic clutch shaft 71 to move.
It always meshes with the forward first-stage gear 25 that is engaged and disengaged with the. Further, the forward first-stage gear 25 on the hydraulic clutch shaft 71 is loosely fitted on the hydraulic clutch shaft 22 and always meshes with the reverse gear 26 which is engaged with and disengaged from the hydraulic clutch shaft 22 by the hydraulic clutch R. .

Further, the fixed gear 9 on the counter shaft 6 is
The hydraulic clutch F3 is loosely fitted on the hydraulic clutch shaft 71,
3rd forward gear 7 disengaged from the hydraulic clutch shaft 71 by
Always meshes with 3. The fixed gear 9 is loosely fitted on the hydraulic clutch shaft 22 and simultaneously meshes with the forward two-stage gear 24 that is engaged with and disengaged from the hydraulic clutch shaft 22 by the hydraulic clutch F2. As described above, the hydraulic clutch type main transmission device is configured, and the counter shaft 6 is rotated by the forward first stage gear 25, the forward second stage gear 24, and the forward third stage gear 73.
To the reverse gear 26, the hydraulic clutch F1 is switched by switching the shift operation valve (not shown).
By selectively engaging one of the hydraulic clutch F2, the hydraulic clutch F3, and the hydraulic clutch R, a main shift of three forward gears and one reverse gear can be obtained.

Further, a power transmission gear 27 is fixed to the central portion of the hydraulic clutch shaft 71, and a power transmission gear 28 is fixed to the central portion of the hydraulic clutch shaft 22. Power transmission gear 2
7 and the power transmission gear 28 simultaneously mesh with a drive gear 30 installed at a substantially central position on the steering shaft 29, and transmit the power that has undergone the main shift to the steering shaft 29. Hydraulic clutch shaft 22
A parking brake 32 is arranged in a portion of the mission case 1 that protrudes to the left side surface. The left and right ends of the steering shaft 29 have friction plate devices BL and B for left and right steering brakes.
R is provided, and side clutch gears 33L and 33R are slidably fitted on both sides of the drive gear. A steering clutch is configured by disengaging the tooth portions of the side clutch gears 33L and 33R with respect to the inner teeth 30L and 30R of the drive gear 30.

Of the friction plate devices BL and BR, the driving side friction plates are locked to the side clutch gears 33L and 33R, the driven side friction plates are locked to the mission case 1 side, and the side clutch gears 33L and 33R are slid. By the movement, both friction plates can be pressed freely to form a steering brake. While the side clutch gears 33L and 33R are slidable, the fixed gears 34L and 3L on the traveling output shafts 35L and 35R are slidable.
4R is configured to be constantly meshed with the traveling output shaft 35.
The drive sprockets 31L and 31R are driven from the L and 35R. Crawler type traveling devices 53L and 53R are driven by the drive sprockets 31L and 31R.

A hydraulic pump P, which is a drive source for operating a side clutch and a side brake, is connected to a portion of the input shaft 2 opposite to the input pulley 2a and protruding from the transmission case 1 to the outside. There is.

A cylindrical shaft 19 is loosely fitted on the power output shaft 20. The gear 16 on the counter shaft 15 keeps the gear portion 3 irrespective of the sliding position of the auxiliary transmission sliding body 3 to the left or right.
It is formed wide so that a is in a meshed state. Also,
The gear 16 meshes with a gear 21 that is loosely fitted on the cylinder shaft 19. In addition, the gear 1 fixed on the counter shaft 15
7 meshes with a gear 42 which is loosely fitted on the power take-off shaft 20.

A variable speed sliding body 23 is spline-engaged on the loose fitting cylinder shaft 19. When the engaging portion 23a of the speed change sliding body 23 meshes with the protrusion 21a of the gear 21, the cylindrical shaft 1
9 is a low speed rotation. Engaging portion 23b of the variable speed sliding body 23
However, when the gear 42 meshes with the protrusion 42a of the gear 42, the cylinder shaft 19 is rotated at high speed. The power take-off shaft 20 is configured such that the engagement body 44 fixed to the cylinder shaft 19 and the clutch slider 14 spline-fitted onto the power take-off shaft 20 are connected so that the rotation of the cylinder shaft 19 is transmitted. ing.

Next, the essential parts of the present invention will be described in detail with reference to FIGS. 3 and 4. A drive gear 30 is fixedly provided on the outer periphery of the substantially central portion of the steering shaft 29, and side clutch gears capable of engaging and disengaging internal teeth 30L and 30R formed on the left and right of the inner periphery of the boss portion of the drive gear 30. Cylindrical rotary bodies 32L and 32R having 33L and 33R on one end side are slidably fitted on the steering shaft 29. The tubular rotating body 32L / 3
An annular pressure plate 61 is locked to the step portion 33c formed in the middle portion of 2R.

Spline grooves are formed along the axial direction on the outer peripheral surface of the cylindrical rotary bodies 32L and 32R on the rear end side, and the rotary side friction plates of the friction plate devices BL and BR are axially formed in the spline grooves. It is slidable and locked so that it cannot rotate relative to it. 68
Is an oil passage plate 67 attached to both outer side surfaces of the mission case 1.
It is a brake case mounted on the upper part, and the steering shaft 29 is supported by a bearing therein, and the friction plate device B is also provided.
It houses L and BR. The fixed-side friction plate of the friction plate device BL / BR, which overlaps with the rotating-side friction plate, is fitted in a locking groove formed on the inner surface of the brake case 68 so as to be axially slidable and relatively non-rotatable. Cylindrical rotating body 32L ・ 32
A biasing spring 6 is provided between the rear end side of the R and the brake case 68.
0 is arranged, and the steering clutch brake is configured by urging the side clutch gears 33L and 33R in the direction in which they engage with the internal teeth 30L and 30R of the drive gear 30.

The tubular rotating body 32L is arranged in a direction to disengage the side clutch gears 33L and 33R from the inner teeth 30L and 30R.
An annular cylinder case 64 having a through hole slightly larger than the outer diameters of the side clutch gears 33L and 33R in the center thereof for sliding operation of the 32R is provided as the cylindrical rotating body 3.
It is attached to both inner side surfaces of the mission case 1 so as to be fitted on the outer periphery of the middle portion of the 2L / 32R. A bottomed recess 64b is formed on the inner peripheral side of the mounting surface 64a of the cylinder case 64 with respect to the transmission case 1. An annular piston 63 is housed in the recess 64b so as to move back and forth. The outer end surface of the piston 63 is in contact with the pressure plate 61 via a thrust bearing.

As shown in FIGS. 5 to 9, the cylinder case 64 has an inner end surface of the piston 63 and a concave portion 6 facing the inner end surface.
A hydraulic chamber is formed between the hydraulic chamber and the bottom surface of 4b, and one end of the oil supply port 66 is opened therein, and the other end of the oil supply port 66 is opened in the mounting surface 64a and straddles the inner and outer surfaces of the mission case 1. It communicates with the oil passage 1a. When pressure oil is supplied to the oil passage 1a and the oil supply port 66 from the hydraulic circuit described later through the oil passage 67a formed between the oil passage plate 67 and the outer surface of the transmission case 1, the piston 63 is The tubular rotary bodies 32L and 32R are extended outward and slide the tubular rotary bodies 32L and 32R outward via the pressure plate 61, and the side clutch gear 33L and
The "clutch disengaged" state in which the engagement between the 33R and the internal teeth 30L, 30R is released is obtained, and then the "brake engaged" state in which the pressure plate 61 presses the friction plate devices BL, BR is obtained. ing.

In order to ensure that the "clutch disengagement" position of the piston 63 is revealed, an annular groove 65a is formed on the outer peripheral surface of the recess 64b at a position where the piston 63 has been stroked to the "clutch disengagement" position. The annular groove 65a communicates with one end of the oil drain port 65b. The other end of the oil drain port 65b is opened to the mounting surface 64a,
It communicates with an oil passage 1b extending over the inner and outer surfaces of the mission case 1. When the pressure oil is supplied to the oil supply port 66, the pressure oil is supplied to the oil passage plate 67 and the mission case 1.
If the oil is supplied to the oil passage 1b and the oil discharge port 65b through the oil passage 67b formed between the piston 63 and the outer surface of the piston, the piston 63 is further "brake on" from the "clutch disengaged" position according to the pressure oil force. Can be extended to a state. Further, if the oil drain port 65b is opened into the tank (mission case 1), the piston 63 is in the middle of its stroke, and when the inner end surface of the piston 63 approaches the oil drain port 65b, the pressure oil of the oil feed port 66 becomes an annular groove. Because it escapes to 65a, it stops securely at the position where the "clutch engaged" state appears.

A cylindrical member 39 is fixed to the outer peripheral wall of the recess 64b of the cylinder case 64 so as not to move in the axial direction so as to cover the annular groove 65a. As shown in FIG. 10, on the outer peripheral surface of the cylindrical member 39, annular grooves are engraved at positions inward and outward of the O-ring (a).
Is installed and is oil-tightly fitted to the inner peripheral wall surface of the recess 64b. Further, the cylindrical member 39 has an opening 40 having a shape shorter than the entire circumference of the cylindrical member 39 and smaller than the width of the annular groove 65a, and has an inner peripheral surface and an outer peripheral surface. The opening 40 that is cut out so as to penetrate therethrough is provided, and the opening 40 is directly opposed to the annular groove 65a. The position of the outer end surface of the piston 63 is
Even when the piston 63 contracts most, the opening 40
So that the width in the axial direction is relatively long, and the O-ring (b) is installed on the outer peripheral surface near the outer end surface of the cylindrical member 39 so that it is oil-tight. It is slidably fitted. Further, an O-ring (c) is installed on the inner peripheral surface near the inner end surface of the piston 63, and it is slidably fitted in an oil-tight manner to the peripheral wall surface of the recess 64b.

Therefore, as described above, when the piston 63 makes a stroke in the recess 64b, the pressure oil supplied to the hydraulic chamber between the bottom surface of the recess 64b and the inner end surface of the piston rises in temperature as the machine runs. When the viscosity of the oil is reduced due to the
Even if an attempt is made to leak outside, the O-rings (b, c) are surely received. Here, the pressure oil leaking to the outer peripheral surface side of the piston 63 reaches the O-ring (b) by
Even if it passes through the opening 40 of the cylindrical member 39, if the "brake on" state is obtained, the pressure oil having the same force as the pressure oil in the recess 64b acts on the opening 40,
It never leaks. Further, when the "clutch disengagement" state is obtained, the opening 40 communicates with the tank side through the annular groove 65a, but the opening degree of the opening 40 is the same as that described above in the cylindrical member 39 separate from the cylinder case 64. Since the processing can be made as small as possible in this mode, the piston 63 can be stably and surely stroked to the position of the "clutch disengaged" state while suppressing the pressure oil leaking therefrom.

In FIG. 11, the hydraulic oil of the hydraulic pump P is supplied to the hydraulic chamber of the cylinder case 64 to supply the piston 6 with the hydraulic oil.
3 is a hydraulic circuit diagram for actuating No. 3. A steering clutch directional control valve AV and a steering brake directional control valve HV are connected in parallel to the hydraulic pump P. The steering clutch directional control valve AV has a carry-over port for guiding the first oil supply passage 70 communicating with the hydraulic pump P to the second oil supply passage 71 communicating with the steering brake directional control valve HV. And a left and right sides thereof, and an operating position for selectively passing the first oil supply passage 70 through one of the clutch oil passages 72, 72, a three-position switching type is provided. The steering brake directional control valve HV connects the second oil supply passage 71 and one of the brake oil passages 73 to one of the brake oil passages 73 and the neutral position where the second oil supply passage 71 and each hydraulic chamber of the cylinder case 64 are connected to the tank. And an operating position where the other one of the brake oil passages 73 communicates with the tank, and an operating position where the second oil supply passage 71 communicates with the other brake oil passage 73 and one of the brake oil passages 73 communicates with the tank. It is also configured as a 3-position switchable type.

The steering clutch directional control valve AV is of an electromagnetic switching type. For example, the combine is automatically steered along the grain culm row in response to a signal from a grain culm detection sensor mounted in front of the harvesting section of the combine. It is configured to be switched by an electric signal from a controller (not shown) when the vehicle is to be operated, or when the course of the machine is slightly modified and the steering is to be performed for a short time. The steering brake directional control valve HV is of a manual switching type and is linked to a steering lever arranged near the driver's seat. Further, the LV increases the set relief value proportionally to increase the hydraulic pressure acting on the second oil supply passage 71 when the steering brake directional control valve HV is switched from the neutral position to one of the operating positions. It is a variable relief valve mechanically interlocked with the steering brake directional control valve HV so as to be raised.

The oil supply port 66 and the oil discharge port 65b provided in the cylinder case 64, the clutch oil passage 72,
Pilot hydraulic pressure switching type clutch brake control valves SV and SV are interposed between 72 and the brake oil passages 73 and 73. The clutch brake control valves SV and SV connect the brake oil passage 73 to both the oil supply port 66 and the oil discharge port 65a (I) position, and the clutch oil passage 72 to the oil supply port 66 so as to connect the oil discharge port 65a. A two-position switching type having a (II) position that communicates with the brake oil passage 73 is formed, and the pilot oil chamber SVa is connected to the clutch oil passage 72 so that pressure oil flows through the clutch oil passage 72. It is configured to automatically switch to the (II) position only at times.

When the steering clutch directional control valve AV is switched to one operating position by an electric signal from the controller, the first oil supply passage 70 is connected to one of the clutch oil passages 72, and the steering clutch brake on that side is connected. The control valve SV is switched to the (II) position, and the pressure oil flowing through the clutch oil passage 72 is introduced into the hydraulic chamber of the cylinder case via the oil supply port 66. When the piston 63 strokes to the "clutch disengaged" position, the pressure oil in the hydraulic chamber is discharged from the oil discharge port 65b to the tank through the brake oil passage 73 and the neutral position of the steering brake directional control valve HV. The piston 63 is stopped in the middle of its stroke, the steering clutch is only disengaged, the steering brake is not applied, and the vehicle body steers with a large turning radius.

When the steering clutch directional control valve AV is in the neutral position and the steering brake directional control valve HV is manually switched to one of the operating positions, the second oil supply passage 71 becomes the brake oil passage 73. Connected to one. Since the steering clutch brake control valve SV on that side is in the position (I) shown in the figure, the pressure oil flowing through the brake oil passage 73 is guided to the hydraulic chamber of the cylinder case through the oil supply port 66 and discharged. It is also guided to the oil port 65b. Since the set relief value of the variable relief valve LV is changed according to the switching amount of the steering brake directional control valve HV to the operating position, the second oil supply passage 71, that is, the hydraulic chamber,
In addition, the hydraulic pressure acting on the oil discharge port 65b is artificially adjusted, so that the piston 63 can be freely stroked from the "clutch disengaged" state to the "brake engaged" state, and the aircraft will have a large turning radius. To a small turning radius.

[0029]

According to the present invention, the cylindrical member 39 is interposed between the inner peripheral surface of the cylinder case 64 and the outer peripheral surface of the piston 3, and the oil drain port 65b is provided in the cylindrical member 39.
When the "clutch disengaged" state in which the side clutch gears 33L and 33R are separated from the drive gear 30 is obtained by providing the opening 40 that communicates with the oil supply port 66.
When pressure oil is supplied to the piston 63, the piston 63 is in the middle of its stroke, and when the inner end surface of the piston 63 reaches the opening 40, the pressure oil of the oil supply port 66 escapes to the tank through the opening 40 and the oil discharge port 65b. The "cut" state can be surely brought out.

In addition, when the "clutch disengaged" state is operated, if the viscosity of the oil decreases due to the temperature rise during traveling, the pressure oil supplied into the hydraulic chamber of the cylinder case 64 will change from the inner end surface of the piston 63 to the outer peripheral surface. Although it tries to leak into the oil discharge port 65b side by flowing into the tank, the amount of pressure oil leaking to the tank side can be limited by the appropriately set opening degree of the opening 40, and the piston 63 can be stroked in the hydraulic chamber. The resulting hydraulic pressure can be generated, and the "clutch disengaged" state can be stably exhibited in any situation.

The opening 40 is provided in the cylinder case 64.
The cylindrical member 39, which is separate from, can be easily processed and formed, and the degree of opening can be freely set.

[Brief description of the drawings]

FIG. 1 is a side view of a combine equipped with a steering clutch and brake operating device of the present invention.

FIG. 2 is a skeleton diagram of a traveling power transmission mechanism including a steering clutch brake operating device of the present invention.

FIG. 3 is a side sectional view of the steering clutch brake operating device of the present invention.

FIG. 4 is a plan sectional view of the same.

FIG. 5 is an inner side view of a cylinder case 64 of the present invention.

FIG. 6 is an outer side view of a cylinder case 64 of the same.

7 is a sectional view taken along the line YY of FIG.

FIG. 8 is a sectional view taken along line XX of FIG.

9 is a cross-sectional view taken along the line ZZ of FIG.

FIG. 10: Cylindrical member 3 fitted in the cylinder case 64
9 bird's eye view.

FIG. 11 is a hydraulic circuit diagram of the steering clutch brake operating device of the present invention.

[Explanation of symbols]

 BL / BR Friction plate device P Hydraulic pump AV Directional switching valve for steering clutch HV Directional switching valve for steering brake 1 Mission case 30 Large diameter gear 30L, 30R Inner teeth 33L, 33R Side clutch gear 39 Cylindrical member 40 Opening 63 Piston 64 Cylinder case 65a Annular groove 65b Oil drain port 66 Oil supply port

Claims (1)

[Claims] 1. A steering shaft is horizontally mounted in a mission case,
A hollow cylinder case fixed to the inner wall of the transmission case is arranged on the outer circumference of the steering shaft, an annular piston is arranged in the cylinder case, and the direction switching valve selectively feeds the oil supply port of the cylinder case. By supplying pressure oil, slide the piston to the position of the oil drain port provided in the middle of the cylinder case, separate the side clutch gear on the steering shaft from the drive gear, and then By operating to increase the pressure, the piston is further slid from the oil drain port position to apply braking to the side clutch gear, in the mechanism between the inner peripheral surface of the cylinder case and the outer peripheral surface of the piston. A cylindrical member 39 that is oil-tightly fitted to the inner peripheral surface of the cylinder case is provided.
A steering clutch / brake operating device having an opening 40 connected to the oil drain port.