JPH0729617B2 - Steering brake structure for work vehicle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is such that the steering braking force increases as the hydraulic pressure discharged from the middle of the stroke of each operating cylinder that turns on and off a pair of left and right steering brakes increases. The present invention relates to a steering brake structure for a work vehicle in which a manually operated lever is linked to a throttle valve of a variable relief valve that adjusts the exhaust hydraulic pressure so as to have a mechanical linkage mechanism.

[Conventional technology]

In the steering brake structure of this type of work vehicle, in order to configure a mechanical linkage mechanism, conventionally, a spring that presses the throttle valve against the valve seat is provided between the spring and the pressing pin that transmits the operation of the manual operation lever to the throttle valve. Therefore, the operation amount of the holding pin is increased as the operation amount of the manual operation lever is increased, thereby increasing the spring and increasing the pressing force against the valve seat of the throttle valve. The exhaust oil pressure was set to be high from the middle of the stroke.
(For example, JP-A-60-261783).

[Problems to be Solved by the Invention]

Since the exhaust hydraulic pressure, that is, the brake pressure is expressed by the spring force, a large expansion and contraction of the spring is required in order to obtain a large brake pressure, and the mechanical linkage mechanism inevitably causes the throttle valve of this variable relief valve. It was necessary to set a large operation amount of the manual operation lever connected to.

Therefore, the operation amount of the manual operation lever is increased, and there is room for improvement in terms of operability.

An object of the present invention is to provide a mechanical linkage mechanism that can be easily modified to reduce the amount of operation of the manual operation lever.

[Means for Solving the Problems]

In the characteristic configuration according to the present invention, the mechanical linkage mechanism is configured such that the movement amount of the throttle valve in the variable relief valve toward the valve seat side with respect to the operation amount of the manual operation lever has a constant proportional value. And its effects are as follows.

[Action]

For example, as shown in FIG. 1, the throttle valve (23) is directly pressed against the valve seat (22) by the pressing pin (25) via the spacer (26) (the throttle valve (23 ) May not be pressed against the valve seat (22) by a spring), and the throttle valve (23) may be connected to the valve seat (2).
2) As the operating force for the manual operation lever (11) is increased in the state of being brought into contact with the operation lever (11), the operation arm (13) for the holding pin (25) and the manual operation lever (11) that constitute the mechanical linkage mechanism (K). ) Causes the throttle valve (23) to bend and increases the pressing force against the valve seat (22).

Therefore, by increasing the pressing force of the throttle valve (23) against the valve seat (22), the operation cylinders (8A), (8A)
The hydraulic pressure discharged from B) can be increased and the steering braking force can be increased.

〔The invention's effect〕

Conventionally, the structure of increasing the stroke of the lever of the manual operation lever to increase the pressing force against the valve seat of the throttle valve is changed to the valve seat side of the throttle valve in the variable relief valve with respect to the operation amount of the manual operation lever. The amount of movement is set to a constant proportional value and the pressing force on the valve seat of the throttle valve is changed by changing the operating force on the manual operation lever, so that the valve of the throttle valve can be operated without increasing the operation amount of the manual operation lever. The pressing force against the seat can be increased,
This made it possible to improve operability by reducing the operation amount.

Further, since the throttle valve and the manual operation lever are not linked via a spring as in the conventional case, the pressure applied to the throttle valve is reflected more directly on the manual operation lever, and the braking force and the manual operation lever are reflected. A more accurate correspondence with the operation force to improve the operation feeling.

〔Example〕

A parking brake key structure used in a combine as an example of a work vehicle will be described.

As shown in FIG. 4, a pair of left and right steering clutches are attached to a mission case (3) that supports the drive cases (2) and (2) with respect to the pair of left and right crawler traveling devices (1) and (1). The brakes (4A) and (4B) are provided, and these steering clutches and brakes (4A) and (4B) are operated by a claw clutch type steering clutch and a clutch sleeve of the steering clutch. It consists of and. And
A shift fork (5) that acts on the clutch sleeve to open and close the steering clutches and brakes (4A) and (4B) is attached to the operation shaft (6) in a state of being engaged with the clutch sleeve. The left and right steering clutches / brakes (4A) and (4B) are provided with an operation arm (7A) at an end of the operation shaft (6) protruding outward of the transmission case (3)
(7B) is integrally rotatably fixed, and power-operated by left and right operation cylinders (8A) and (8B) described later.
That is, the left and right operation cylinders (8A) and (8B) for contacting the operation arms (7A) and (7B) with the piston rod from above are provided above the operation arms (7A) and (7B), and the left and right operation cylinders are provided. Electromagnetic control valve (9) for selectively switching hydraulic oil between (8A) and (8B), and variable relief in the oil discharge passage from the middle of the stroke of the left and right operation cylinders (8A) and (8B) A valve (10) is provided for steering clutch.
The brakes (4A) and (4B) can be operated by power.

A single manual operation lever (11) is provided for the steering clutches and brakes (4A), (4B), and the potentiometer (12) of the operation lever (11) at the swing axis (X) position is provided. The electromagnetic control valve (9) is switched based on the operation lever swing detection result, and oil is supplied to the operation cylinder (8A or 8B) on the swing direction side of the operation lever (11). Then, the piston rod extends and the steering arm (7A or 7B) on the steering direction side.
Is operated to turn the steering clutch to the disengaged state. When the operation lever (11) is further swung from the clutch disengaged position, the variable relief valve (10) has a throttling effect, so that the exhaust oil pressure can be varied, and the piston rod is further extended as the exhaust oil pressure increases. The steering braking force can be increased and the braking force can be maximized if the variable relief valve (10) is completely closed. Variable Relief Valve (10)
Swing operation arm (13) and manual operation lever (11)
And are linked by a release wire (14), and the operating force for the manual operating lever (11) is used as the throttle force of the variable relief valve (10). In other words, the left and right interlocking arms (29A) and (29B) pivotally supported near the manual operation lever (11) without crossing each other, and the left interlocking arm (29A) outer end and the right interlocking arm (29B). The inner end of the variable relief valve (10) is connected to the inner end of the variable relief valve (10) so that the manual operation lever (11) can be swung in either direction.

As shown in FIG. 2, the outer end (15a) of the release wire (15) is attached to one end of the left operation arm (7A) that is integrally rotatably fitted to the operation shaft (6) and the horizontal axis (Y). While attaching via a top member (16) that is relatively rotatable around,
The inner end (15b) of the inner wire extended from the outer end (15a) is pin-connected to one end of the right operation arm (7B) through a long hole. Meanwhile, this release wire (1
The outer end (15c) on the other end side of 5) is fixed to a mounting support frame (18) to which a parking pedal (17) as a single artificial operation tool is attached, and extends from this outer end (15c). The inner end (15d) of the inner wire has a parking pedal (1
It is attached and fixed to a swing arm (19) that rotates together with 7). Then, when the parking pedal (17) is locked and fixed by the stepping lock member (20), the inner wire is pulled and the posture of the outer wire is changed, so that the operation arms (7A) and (7B) are changed as shown in the drawing. Swing toward each other. Therefore, the left-right steering brake is turned on, and the parking brake is activated.

Next, the structure of the variable relief valve (10) will be described. As shown in FIG. 1, a valve seat (22) is installed in the oil passage (A) of the valve body (21), and a poppet type throttle valve (23) that abuts against this valve seat (22). This poppet type throttle valve (23) adjusts the discharge oil pressure from the outlet port (b) by restricting the discharge oil from the operation cylinders (8A) and (8B) introduced at the inlet port (a). It is configured accordingly. A stopper block (24) is screwed and fixed on the back side of the poppet type throttle valve (23), and the poppet type throttle valve (23) is pressed against the valve seat (22) to contact the stopper block (24). The holding pin (25) is slidably supported, and the tip of the holding pin (25) and the poppet type throttle valve (2
A spacer (26) is interposed between it and 3). Further, a pin head (27) is fixed to the tip portion of the pressing pin (25) protruding from the stopper block (24), and a spring () is provided between the pin head (27) and the end surface of the stopper block (24). 28) is inserted and this spring (28)
The pressing pin (25) is urged in the direction away from the poppet type throttle valve (23) by the pin head (2
It is slid in the direction approaching the poppet type throttle valve (23) by the swing operation arm (13) acting on 7).

That is, the left and right interlocking arms (29A), (29B), release wire (14), swing operation arm (13), pin head (2)
The amount of movement of the throttle valve (23) of the variable relief valve (10) to the valve seat (22) side with respect to the amount of operation of the manual operation lever (11) by 7), the pressing pin (25), and the spacer (26). A mechanical linkage mechanism (K) that links the manual operation lever (11) and the throttle valve (23) is configured so that the constant value becomes a constant proportional value. When (11) is swung to the brake on position, the poppet type throttle valve (23) is brought into substantially contact with the valve seat (22), and if an operating force is further applied from this state,
Since the holding pin (25) itself is at the sliding limit, the swing operation arm (13) and the manual operation lever (11) are bent,
The poppet type throttle valve (23) increases the pressing force against the valve seat,
Exhaust oil pressure from the operating cylinders (8A) and (8B) is correspondingly increased, leading to an increase in braking force.

[Other Embodiments] The mechanical linkage mechanism (K) may have a structure in which the poppet type throttle valve (23) is directly pressed by the pressing pin (25) without using the spacer (26). The release wire (14) may be replaced with a link mechanism. That is, the valve seat (2
Any structure can be used as long as the pressing force against 2) can be changed only by the operating force applied to the manual operation lever (11) instead of the spring force.

The above embodiment may be applied to other work vehicles such as agricultural machines and construction machines other than combine harvesters.

In the above embodiment, the steering clutch / brake has been described, but the present invention can be applied to a steering clutch / brake only.

It should be noted that reference numerals are added to the claims for convenience of comparison with the drawings, but the present invention is not limited to the structures of the accompanying drawings by the entry.

[Brief description of drawings]

The drawings show an embodiment of the steering brake structure for a work vehicle according to the present invention. FIG. 1 is a sectional view showing the internal structure of a variable relief valve, FIG. 2 is a front view showing the parking brake structure, and FIG.
FIG. 4 is a side view showing the operation structure of the parking brake and the steering brake, and FIG. 4 is a hydraulic configuration diagram showing the operation structure of the steering brake. (4a), (4B) ... Steering brake, (8A), (8B) ... Operating cylinder, (10) ... Variable relief valve, (11) ... Manual operating lever, (22) ... Valve seat, (23) ... Throttle valve, (K) ...
Mechanical linkage mechanism.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-261783 (JP, A) JP-A-62-152980 (JP, A)

Claims (1)

[Claims] 1. The steering braking force is increased as the hydraulic pressure discharged from the middle of the stroke of the respective operating cylinders (8A) and (8B) for turning on / off the pair of left and right steering brakes (4A) and (4B) increases. For a throttle valve (23) of a variable relief valve (10) that adjusts its exhaust oil pressure so that it becomes larger, a manually operated lever (11) is linked via a mechanical linkage mechanism (K) to a work vehicle. In the steering brake structure, the mechanical linkage mechanism (K) is directed toward the valve seat (22) side of the throttle valve (23) in the variable relief valve (10) with respect to the operation amount of the manual operation lever (11). A steering brake structure for a work vehicle configured so that the moving amount of the work vehicle has a constant proportional value.