JP3789461B2 - Steering device for work vehicle - Google Patents

Description

  The present invention relates to a mechanism for changing the rotation of a handle to rotation of a swash plate of a hydraulic motor in a configuration in which steering is performed by changing the rotation speed of left and right hydraulic motors by rotation of the handle.

Conventionally, a work vehicle is equipped with an HST transmission, and the crawler type traveling device is driven by the left and right hydraulic motors, and the rotational speed of the left and right hydraulic motors is changed in accordance with the rotation of the handle. Techniques adapted to this are well known.
In such a traveling vehicle, a steering mechanism is disposed at the lower portion of the front column in order to change the rotation of the handle to the front / rear or left / right movement of the trunnion arm that changes the angle of the swash plate.
Japanese Patent Laid-Open No. 7-81608

  In such a conventional configuration, when the sub-shift switch is connected to an actuator that drives the lock pin to be inserted and removed and an actuator that shifts the sub-transmission device to change the height, and the sub-shift is switched to the high speed side, the lock pin moves the rack. The steering angle of the handle can be turned only within a certain range from the straight direction, and it is impossible to make a quick turn at a high speed, thereby preventing a fall or the like.

The present invention uses the following means in order to solve the above problems.
A pinion is provided on a pinion shaft that is connected to the steering shaft of the handle, the pinion is engaged with a rack, a restriction recess is provided at the center of the rack, and a lock pin can be inserted into and removed from the control recess, and an operating portion A sub-shift switch is provided to enable high and low speed shifting by operating the sub-shift switch, and the sub-shift switch is connected to an actuator that drives the lock pin to be inserted and removed and an actuator that shifts the sub-transmission device at a high and low speed, It is configured to restrict turning at times.

The present invention configured as described above has the following effects.
Since the sub-shift switch is connected to the actuator that drives the insertion and removal of the lock pin and the actuator that shifts the sub-transmission device, when the sub-shift is switched to the high speed side, the lock pin regulates the movement of the rack and the handle rotation The moving angle can only turn within a certain range from the straight traveling direction, it is impossible to make a sharp turn at a high speed, and fall or the like can be prevented.

  Next, the configuration of the embodiment shown in the accompanying drawings will be described. 1 is an overall side view of the crawler tractor, FIG. 2 is a plan view of the same, FIG. 3 is a plan view of the interior of the cabin of the operating unit, and FIG. 5 is a hydraulic circuit diagram, FIG. 6 is a plan view inside the steering case, and FIG. 7 is a diagram showing a swash plate angle control means.

  The overall configuration will be described with reference to FIGS. The crawler type tractor has an engine E mounted on the front of the body frame 1 and is housed in the hood 2. A three-point link type work machine mounting device A is disposed at the rear end of the machine body frame 1, and a work machine B is mounted at the rear end of the work machine mounting device A so that it can be moved up and down by the lifting means 4. In addition, the working machine B of a present Example is a rotary tiller, and the raising / lowering means 4 is a hydraulic cylinder.

  A cabin 3 is disposed at the rear of the bonnet 2, and a driving unit C is configured with a handle 5 and a driver's seat 6 inside the cabin 3. A fuel tank 7 and a hydraulic oil tank 8 are disposed on the left and right sides of the cabin 3. A crawler type traveling device D is disposed below the body frame 1.

  The crawler type traveling device D has a traveling frame 12 disposed below the fuselage, a driving sprocket 13 driven by a hydraulic motor M is disposed at the front end of the traveling frame 12, and a driven wheel 14 is provided at the rear end so that it can be tensioned. .. Are arranged at the lower part of the traveling frame 12, the roller 16 is pivotally supported at the upper part, and the drive sprocket 13, the driven wheel 14, the rolling wheel 15, and the crawler 17 around the roller 16. The left and right drive sprockets 13 and 13 are rotated by hydraulic motors M and M so as to travel.

  As shown in FIGS. 2 and 4, a front mission case 20 is fixed to the rear portion of the engine E via a clutch case, and a pair of variable displacement hydraulic pumps P <b> 1 and P <b> 1 is attached to the rear portion of the front mission case 20. And the hydraulic pump P2 for supplying hydraulic oil to the HST transmission are arranged in series, and the engine E and the front transmission case 20, the hydraulic pumps P1, P1, and P2, and a steering case 40, which will be described later, are provided with the vibration isolating rubber 11.・ It is supported by anti-vibration with respect to the body frame 1 by 11.

  The hydraulic pumps P1 and P1 and the left and right hydraulic motors M and M communicate with each other by pipes to form a closed circuit, thereby forming an HST transmission. The hydraulic oil is fed from the hydraulic pumps P1 and P1 to the hydraulic motors M and M to drive the hydraulic motors M and M. A rear mission case 21 is disposed at the rear of the body frame 1, and power is transmitted from the front mission case 20 to the rear mission case 21 via the universal joint 22. A PTO shaft 19 protrudes rearward from the rear surface of the rear mission case 21, and power is transmitted to the working machine B via the universal joint 23.

  The front transmission case 20 and the rear mission case 21 are communicated by connecting pipes 28 and 29 so that the lubricating oil in both cases can flow, and the connecting pipe 28 is attached to the front mission case 20 side. A hydraulic pump P3 for driving the work machine and a filter 38 are disposed in the section. In addition, although the connection pipes 28 and 29 are two, it is also possible to connect with more connection pipes, and the hydraulic pump P3 and the filter 38 may be arranged in the connection pipe 29. The connecting pipes 28 and 29 are preferably arranged at the lower portions on both the left and right sides so that the lubricating oil circulates between the front mission case 20 and the rear mission case 21 by the operation of the hydraulic pump P3.

  With this configuration, the filter 38 can be easily replaced, maintenance can be easily performed, and the lubricating oil in the front and rear transmission cases can be used as hydraulic oil, so that the tank capacity can be increased. Thus, the capacity of the hydraulic oil tank can be reduced or eliminated. Further, since the lubricating oil circulates through the connecting pipes 28 and 29, the outer periphery of the pipe is cooled by the outside air, and an increase in the oil temperature can be suppressed without providing a fan or the like.

  As shown in FIG. 3, a front column 9 is provided in the rear part of the hood 2, a driver seat 6 is disposed behind the driver column C, and a right lever guide 25 is provided on the right side of the driver seat 6. A position lever 31 and a draft control lever 33 are provided, and PTO speed change levers 34 and 35 are provided on the left side. A round handle 5 is projected from the upper surface of the front column 9, an operation panel 27 such as a speedometer and a fuel meter is disposed on the upper surface of the front column 9, and the traveling direction of the upper surface of the front column 9 is further increased. The accelerator lever 24 protrudes on the right side toward the right, and the forward / reverse lever 30 protrudes on the left side. The grip 30a of the forward / reverse lever 30 is provided with a work implement elevating lever 32 and an auxiliary transmission switch 37. Reference numeral 36 denotes a brake pedal.

  Next, the hydraulic circuit will be described. Drive sprockets 13 and 13 are fixed on the output shafts of the hydraulic motors M and M, and the crawlers 17 and 17 can be rotated. The hydraulic motor M is integrally provided with a hydraulic servo brake 74 and a sub-transmission mechanism 75, and the brake 74 can be operated by switching a brake hydraulic valve 76. The brake can be braked by depressing the brake pedal 36, and the brake is released by starting the engine E and driving the hydraulic pumps P1 and P1. The sub-transmission mechanism 75 can change the flow rate to two stages of high and low by switching the actuator, in this embodiment the shift electromagnetic valve 77. The electromagnetic valve 77 is switched by operating the auxiliary transmission switch 37. 78 is a pilot hydraulic pressure switching valve. Reference numeral 80 denotes a control valve, which allows the elevating means 4 to be expanded and contracted or fed to an external hydraulic device by operating the position lever 31 or the work implement elevating lever 32. Reference numeral 79 denotes a motor, which is connected to the work implement lifting lever 32, operates the work implement lift lever 32, drives the motor 79, changes the spool of the control valve 80, and extends and lowers the lifting means 4 to work. Machine B can be moved up and down.

  As shown in FIG. 4, a steering case 40 is integrally assembled to the side portions of the hydraulic pumps P1 and P1, and a pinion shaft 39 projects upward substantially at the center of the steering case 40, The pinion shaft 39 is connected to a steering shaft extending from the center of the handle 5 via a universal joint or the like. The pinion shaft 39 is positioned below the handle 5 as much as possible.

  As shown in FIG. 6, the steering case 40 has a structure in which a speed change shaft 41 and a slide shaft 44, each of which is an angular axis (triangular axis in this embodiment), are horizontally mounted in the front-rear direction. The case 40 is rotatably supported via a bearing, and one end of the case 40 projects outward from the steering case 40 to fix an arm 48. The arm 48 is linked to the forward / reverse lever 30 via a link mechanism.

  A base portion 45b of a slide acting body 45 is slidably fitted to the front and rear central portions of the slide shaft 44, and guide arms 47 and 47 are slidably fitted to both sides thereof. A rack 45a is fixed to the lower part of the slide acting body 45 in the front-rear direction, and the rack 45a meshes with a pinion 39a fixed to the lower end of the pinion shaft 39. A restriction recess 45c is fixed to the upper portion of the rack 45a, and a lock pin 46a can be inserted into the recess of the restriction recess 45c. The lock pin 46a can be protruded by operating an actuator, in this embodiment, a solenoid 46. The solenoid 46 is fixed to the side surface of the steering case 40, and the solenoid 46 is connected to the auxiliary transmission switch 37. ing.

  The auxiliary transmission switch 37 is connected to an electromagnetic valve 77 for shifting the hydraulic motor M in two steps of high and low, and when the auxiliary transmission switch 37 is pressed to change the speed to the high speed side, the solenoid 46 is operated to operate the lock pin 46a. When the handle 5 is rotated by the fitting of the lock pin 46a into the restriction recess 45c, the rack 45a is slid by the rotation of the pinion 39a. It can only rotate within a certain range, preventing sudden turning at high speeds. Conversely, when the auxiliary transmission switch 37 is switched to a low speed, the lock pin 46a protrudes from the restricting recess 45c, so that the turning of the handle 5 can be turned without being restricted.

  Further, sliding bodies 43, 43 are rotatably fitted in the central portions of the guide arms 47, 47, and the sliding bodies 43, 43 are slidably mounted on the transmission shaft 41 via bosses 43a, 43a. It is fitted. The regulating body 45c is positioned between the sliding bodies 43 and 43, and the outer sides of the sliding bodies 43 and 43 are urged toward the center by springs 42 and 42. Further, the arms 43b and 43b protrude from one end of the sliding bodies 43 and 43, and are linked to one end of a guide body 50 and 50, which will be described later. Boss portions 47a and 47a are provided at the other ends of the guide arms 47 and 47, and pivot shafts 50a and 50a protruding from the centers of the guide bodies 50 and 50 are rotatably supported.

  The guide bodies 50 and 50 are formed in a U-shaped cross-sectional view and open on the side, and rollers 51 and 51 are inserted into the open portions, and the guide bodies 50 and 50 are slidably inserted in the front-rear direction. ing. The rollers 51 and 51 are rotatably supported at one ends of support arms 52 and 52, and the other ends of the support arms 52 and 52 are fixed to pivot shafts 54 and 54, respectively. 40, and the other end of each of the pivot shafts 54 and 54 is fixedly provided with arms 53 and 53. The arms 53 and 53 have spool control levers 55 and 55 of the swash plate angle control means G. It is connected with.

  The swash plate angle control means G will be described with reference to FIG. A base portion of a trunnion arm 92 is fixed to a swash plate operating shaft 91 interlocked with a swash plate of the hydraulic pump P1, and a pin 94 fixed to a servo spool 93 is provided in a long hole provided at the other end of the trunnion arm 92. Inserting. The servo spool 93 is inserted into a servo cylinder 95, and the servo spool 93 is biased to a neutral position by springs 96 in the servo cylinder 95. A spool control lever 55 is pivotally supported at one end of the servo spool 93, a midway portion of the spool control lever 55 is pivotally supported by a pivot shaft 97, and the other end pivotally supports the arm 53.

  By changing the angle of the swash plate of the hydraulic pumps P1 and P1, the discharge amount of hydraulic oil can be changed steplessly, the discharge direction can also be changed, forward and backward movement and main shift can be performed simultaneously, and the left and right discharges By changing the amount, it can be turned by changing the left and right rotational speeds of the hydraulic motors M and M. The angle of the swash plate is changed by the handle 5 and the forward / reverse lever 30. By rotating the forward / backward lever 30 forward or backward, the transmission shaft 41 is moved via the link mechanism and the arm 48. The sliding bodies 43 and 43 are rotated by this rotation, and the guide bodies 50 and 50 are rotated about the rotation shafts 50a and 50a via the arms 43b and 43b. Further, the support arms 52 and 52 are rotated through the rollers 51 and 51 fitted to the guide bodies 50 and 50 to rotate with the pivot shafts 54 and 54, the arms 53 and 53, and the spool control levers 55 and 55. Then, the servo spools 93 and 93 are slid and the trunnion arms 92 and 92 are rotated by the same angle to change the angle of the swash plate, thereby performing the main shift.

  When the handle 5 is rotated, the pinion shaft 39 is rotated by the rotation, and the rack 45a meshed with the pinion 39a is slid. As the rack 45a slides, the slide operating body 45 pushes the guide arm 47 on one side, and the guide arm 47 follows the speed change shaft 41 and the slide shaft 44 while maintaining the angle of the arm 43b rotated by the main speed change. The guide body 50 fitted to the boss 47a is also slid simultaneously. As the guide body 50 slides, the roller 51 moves along the concave portion of the guide body 50 toward the rotation shaft 50 a, and the support arm 52 rotates in the neutral direction, so that the pivot shaft 54, the arm 53, Rotates with the spool control lever 55, slides the servo spool 93, rotates the trunnion arm 92 in the deceleration direction, decreases the rotational speed of the hydraulic motor M on one side, and rotates with the difference in speed between the left and right To do. Further, when the handle 5 is rotated, the slide action body 45 is also slid, the roller 51 moves along the recess of the guide body 50 over the rotation shaft 50a, and the servo spool 93 exceeds the neutral position. The trunnion arm 92 rotates in the reverse direction, and the left and right hydraulic motors M and M rotate in opposite directions to perform a spin turn.

In other words, the steering case and the hydraulic pump of the HST transmission can be directly and integrally assembled, and the steering case can be adjusted as a sub-assembly, so that the number of assembly steps can be reduced. And the link and rod which were arrange | positioned between a steering case and a hydraulic pump can be eliminated, the error which arises with the link or rod can be eliminated, and it can assemble with sufficient accuracy.
In addition, since the steering case and the hydraulic pump are supported in an anti-vibration manner with respect to the fuselage frame, the natural frequency is the same, and the steering case and the hydraulic pump do not vibrate separately. The error at the time of transmission was reduced and the straightness was improved. In addition, since the steering case is disposed on the side of the hydraulic pump, the space on the front column can be eliminated, the foot of the step can be widened, and the ground clearance can be increased.
Furthermore, if the steering case and the swash plate angle control means case are configured as a single case, the number of parts can be reduced, and the pinion and arms in the steering case can be immersed in the lubricating oil. It can be improved and the life can be extended.

It is a whole side view of a crawler type tractor. It is also a plan view. It is a cabin interior top view of an operation part. It is a top view of a front mission case, a hydraulic pump, a steering case, and a rear mission case. It is a hydraulic circuit diagram. It is a top view in a steering case. It is a figure which shows a swash plate angle control means.

Explanation of symbols

P1 Hydraulic pump M Hydraulic motor 5 Handle 30 Forward / reverse lever 37 Sub-shift switch 40 Steering case 45c Restriction recess 46 Solenoid 46a Lock pin 77 Solenoid valve

Claims (1)

  A pinion is provided on a pinion shaft that is connected to the steering shaft of the handle, the pinion is engaged with a rack, a restriction recess is provided at the center of the rack, and a lock pin can be inserted into and removed from the control recess, and an operating portion A sub-shift switch is provided to enable high and low speed shifting by operating the sub-shift switch, and the sub-shift switch is connected to an actuator that drives the lock pin to be inserted and removed and an actuator that shifts the sub-transmission device at a high and low speed, A work vehicle steering system characterized in that it is sometimes configured to restrict turning.

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