JP2007008356A - Tire pressure control device for work vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an appropriate air pressure according to the travel state. <P>SOLUTION: An air pressure control device is equipped with a solenoid valve (4) switching the air filling position for feeding the air or the air bleed position for evacuating the air from the neutral position to a tire (2). The air pressure control device is provided with a selection means (1) selecting the air pressure state of the tire (2) to a low pressure state or a high pressure state. The solenoid valve (4) is switched to the air filling position or the air bleed position based on the selection operation of the selection means (1) so as to obtain target low pressure state or high pressure state, and can conform to the travel state or working state or the like through the operation of the selection means (1) from a driving seat by a driver. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a tire air pressure control device for a work vehicle that switches a tire air pressure between a high pressure state and a low pressure state according to a working state.

There is a technique (for example, see Patent Document 1) that maintains the tire air pressure constant and presses the lateral side surface of the tire from the outside by the tire pressing means to switch between high pressure and low pressure to narrow or widen the contact area. Are known.
Japanese Unexamined Patent Publication No. 2000-301904 (first page, FIG. 1).

  A work vehicle tends to slip when the traction resistance is large, and therefore, the work vehicle often travels with the tire air pressure lowered. However, if the air pressure is kept low, the fuel efficiency is reduced when traveling on the road. In accordance with such a case, the tire pressure is switched by a simple remote operation by the selection means.

  The invention according to claim 1 includes an electromagnetic valve (4) that switches from a neutral position to an air injecting position for sending air to the tire (2) or an air venting position for extracting air, and the tire (2) is in a low pressure state. A selection means (1) for selecting a state or a high pressure state is provided, and based on a selection operation of the selection means (1), the solenoid valve (4) is switched to an air injecting position or an air bleeding position to achieve a target low pressure state or high pressure. A tire pressure control device for a work vehicle, characterized in that the state is obtained.

  When the vehicle driver selects the selection means (1) such as a switch, the solenoid valve (4) is switched. When the high pressure state is selected, the solenoid valve (4) is switched to the air injection position and air is supplied to the tire (2). When the low pressure state is selected, the solenoid valve (4) is switched to the air bleeding position to bring the high pressure tire into a low pressure state.

  The invention according to claim 2 is characterized in that the air pressure of the tire (2) is provided so as to be automatically switchable between a high pressure state and a low pressure state according to a high speed position and a low speed position of the vehicle body (3) traveling shift. To do. When the travel shift of the vehicle body (3) is operated to the high speed position by the main shift or sub-shift operation as in the road travel state, the solenoid valve (4) is thereby switched to the high pressure state, and the air pressure of the tire (2) Is maintained at a high pressure. When the travel shift is shifted to the low speed position as in the work travel state, the air pressure of the tire (2) is automatically switched to the low pressure state by the solenoid valve (4).

  According to a third aspect of the present invention, in the configuration of the first aspect, the air pump is configured such that the piston reciprocates in the cylinder by forward or backward rotation of the wheel.

  According to the first aspect of the present invention, the driver operating the work vehicle operates the selection means (1) from the driver's seat or the like, so that the pneumatic pressure of the tire (2) is changed to the high pressure state by the operation of the electromagnetic valve (4). Since it is possible to switch to a low pressure state, the switching operation is simple and easy, and it is possible to immediately respond to running or working conditions.

  The invention according to claim 2 improves the operability because the air pressure of the tire (2) is automatically switched between the high pressure state and the low pressure state in accordance with the shift running at the high speed position and the shift position of the work vehicle. it can.

  Since the invention according to claim 3 is equipped with an air pump (70) that operates in accordance with forward or reverse rotation of the wheel, air is stably supplied into the tire (2) during traveling. be able to.

  On the basis of the drawings, the work vehicle constitutes a four-wheel drive tractor riding tractor in which front wheels 7 and rear wheels 8 are arranged in front and rear of the vehicle body 3 and driven by an engine 9 mounted on the front portion. . The vehicle body 3 is integrally formed by connecting the engine 9 to the front end of the clutch housing 10 and connecting the front mission case 11 and the rear mission case 12 to the rear end. An HST (hydraulic continuously variable transmission) is mounted in the clutch housing 10 at the front end of the transmission case 11. Note that the HST is known in the art that can perform a stepless main shift from the neutral position to the forward acceleration position or the reverse acceleration position by stepping on the HST petal composed of the forward petal and the reverse petal on the step floor 18. It is a configuration.

  A steering post 40 is provided at the front of the step floor 18 and a steering handle 41 is provided at the top. In addition, a driver's seat 43 is provided at the rear of the step floor 18 so that the driver's seat 43 can be moved back and forth with respect to the seat floor 42. The bracket 44 integrated with the driver's seat 43 operates a sub shift lever 47 that operates the shift shifter 45 of the sub transmission in conjunction with the link 46 and a switching shifter 48 of the front wheel clutch that transmits to the front wheels 7 in conjunction with the link 49. A two-wheel drive and four-wheel drive switching lever 50 is coaxially supported 51. By adjusting the forward / backward movement of the driver's seat 43, the auxiliary transmission lever 47, the switching lever 50, etc. are moved together to maintain operability at a constant level.

  Further, as shown in FIG. 5, the auxiliary transmission lever 47 is provided with a spring 52 for preventing the transmission gear from being lost, on the side of the lever guide 53 that guides and locks the transmission position of the auxiliary transmission lever 47. It is configured in a form that does not get in the way. The auxiliary transmission lever 47 is supported by a support pin 55 so as to be swingable in the axial direction with respect to a boss 54 fitted around the lever shaft 51, and protrudes toward the lever guide 53 between the boss 54 and the auxiliary transmission lever 47. A spring 52 is stretched between the protrusions 56 and 57 to tension the auxiliary transmission lever 47 toward the lever guide 53 side. The lever guide 53 is fixed to the bracket 44.

  The front wheel 7 and the rear wheel 8 have a tire 2 and are configured to be able to switch the air pressure between a high pressure state and a low pressure state. The disc 63 of the tire 2 rim 62 is attached to the axle 61 that is pivotally supported by the axle housing 60. A balance chamber 65 that communicates with the inside of the tire 2 through a communication port 64 and a high-pressure chamber 66 are formed on the inner peripheral portion of the rim 62. An eccentric cam 67 is fitted around the axle 61 so as to be integrated with the axle housing 60.

  The casing 68 integral with the rim 62 is provided with a seal 69 between the inner peripheral edge portion and the axle housing 60. An air pump 70 for sending the air pressure of the high pressure chamber 66 is provided inside the casing 68. The air pump 70 is pressed against the spring 74 by sliding into the cylinder 73 and sliding on the eccentric cam 67 while being fitted into the cylinder 73 via the check valve 71 and the pipe 72. And a piston 75 (FIG. 1).

  When the piston 75 is reciprocated in the cylinder 73 by the forward F or reverse R rotation of the tire 2, the outside air in the casing 68 is sucked from the cylinder 73 intake hole 76, the check valve 71 is opened, and the pipe 72 side is opened. To the pressure. The pipe 72 is provided with a relief valve 77 for releasing a predetermined amount or more of high-pressure air into the outer casing 68. The balance chamber 65 and the high-pressure chamber 66 are formed over a substantially half circumference centering on the air pump 70 and form a partition wall 78. The three-position electromagnetic valve 4 is disposed between the balance chamber 65 and the high-pressure chamber 66 at two locations, and communicates with the neutral position where the two chambers 65 and 66 are partitioned and closed. It is possible to switch between an air injection position for sending the high-pressure air into the balance chamber 65 and an air extraction position for drawing the air in the balance chamber 65 into the casing 68.

  Each balance chamber 65 is provided with an air pressure sensor 79. The air pressure of the tire 2 is uniform over the entire circumference, but the balance chamber 65 communicating with the tire 2 is divided into two sections with a partition wall 78 as a boundary, and the air pressure sensor 79 and the electromagnetic valve 4 are provided for each balance chamber 65. Thus, the air pressure of the entire tire 2 is quickly adjusted by switching the air pressure for each balance chamber 65.

  As shown in FIG. 3, the controller 80 that performs such air pressure switching and pressure control has, on the input side, the selector switch 1 as a selection unit for switching the air pressure of the tire 2 between high pressure and low pressure, Each air pressure sensor 79, a position sensor 81 of the shift lever 47 indicating the other working state, a lever position sensor 83 of the work implement elevating lever 82, an angle sensor 85 of the lift arm 84, and the like are provided. On the output side, various pilot lamps 86, a warning buzzer 87, a liquid crystal monitor 88, a solenoid valve 4, and the like are provided.

  When the driver switches the air pressure of the tire 2, the switch 1 is switched to the target high pressure state or low pressure state depending on the working conditions and running conditions. By this switching, the solenoid valve 4 is switched from the neutral position to the air injection position or the air bleeding position, and is switched from the current air pressure state to the high pressure state or the low pressure state. In this air pressure control, the air pressure is constantly detected by the pressure sensor 79 and feedback control is performed so as to maintain the target pressure.

  By switching the air pressure of the tire 2 between a high pressure state and a low pressure state, the ground contact form is changed. The ground contact width is narrow in the high pressure state, and wide in the low pressure state. Due to the deformation of the tire, mud adhering to the rotating peripheral surface can be dropped. For this reason, it is possible to provide a mud dripping switch for mud dripping and repeat the predetermined interval and the number of switchings to perform switching control between the high pressure state and the low pressure state to control mud dripping. Is possible.

  By operating the steering handle 41, the front wheel 7 can be steered by receiving the hydraulic pressure from the power steering and extending and retracting the power steering cylinder 90. The power steering cylinder 90 is supported by the front axle housing 91, and the left and right front wheels 7 can be steered and interlocked via the steering arm 93, the tie rod 89, and the like by the extension and contraction of the spindle 92. In such a power steering cylinder 90, as shown in FIG. 6, a circular dust seal 94 and a semicircular dust ring 95 holding the dust seal 94 are configured to be retrofitted.

  A seal metal 96 is integrally formed at the tip of the cylinder 90, and a dust seal 97 fitted between the surface of the spindle 92 is provided on the inner peripheral portion thereof. The dust ring 95 is attached by a plate holder 98 and a bolt 99 so as to be in contact with the tip of the seal metal 96. A fitting hole is formed in the end surface portion of the plate holder 98, and the dust ring 95 is fitted, and the snap ring 100 prevents the dust ring 95 from cracking and prevents it from coming off from the plate holder 98. . The dust seal 94 is fitted into a ring groove formed on the inner circumference of the dust ring 95, and the outer circumference of the spindle 92 is fitted and slid. 101 is a hydraulic hose.

  Further, instead of the plate holder 98, a spring holder 103 may be provided as shown in FIG. This spring holder 103 is formed in an 8-shaped form in which the middle part is twisted approximately 180 degrees as a ring form, and rings 104 and 105 are formed at both ends. One ring 104 portion is fitted to the outer periphery of the dastle 95, and the other ring 105 portion is fitted to the protruding member 106 on the cylinder 90 side and held.

  Further, in place of the spring holder 103, a spring holder 108 formed with a winding portion 109 in the form of winding around the spindle 92 as shown in FIG. 8 may be provided. Both ends 110 of the spring holder 108 are engaged with and fixed to the clip holes 111 of the seal metal 96.

  Further, as shown in FIG. 9, the winding holder 109 of the spring holder 108 is formed to have a large diameter and fitted so as to form a large gap with the peripheral surface of the spindle 92. It can also comprise so that a part may be engaged. An o-ring 112 is provided in place of the nap ring 100 for preventing the dust ring 95 from cracking.

  Next, in the middle of the hydraulic circuit 115 of the main lift cylinder for raising and lowering the lift arm 84, an external take-out hydraulic circuit 118 for the mower elevating external take-out cylinder 117 that is switched to the elevating switching control valve 116 is provided. P is a hydraulic pump and T is a tank port. The external take-out hydraulic circuit 118 is provided with a pilot check valve 119 between the elevation switching valve 116 and the cylinder 117. The lower port 120 is provided with an orifice 121 and a pilot port 122 sufficient to operate the pilot check valve 119. The simple pilot check valve configuration has a drawback that it reaches the relief valve pressure when lowered, and an oil temperature rise and a relief noise are likely to occur. However, the above configuration can eliminate such a drawback. Further, the pilot check valve 119 is provided with an externally operable manual push pin 123 capable of manual operation for operating the pilot check valve 119 at the pilot port 122 for raising the pilot pressure on the lower side. The manual push pin 123 can be operated even when the hydraulic pressure is exhausted when the engine 9 is stopped, the mower cannot be lowered, and the mower deck and the like can be easily assembled in the initial stage.

The front sectional view of a tire. The side view. The block diagram of the pneumatic control. The side view of a tractor, and a partial top view. The front view of the subtransmission lever part. Front sectional view (A), flat sectional view (B), and side view (C) of the power steering cylinder section. A plan view (A), a front sectional view (B), and a side view (C) of a power steering cylinder portion showing another example thereof. A plan view (A), a front sectional view (B), and a side view (C) of a power steering cylinder portion showing another example thereof. The plane sectional view showing the example according to the part. External extraction hydraulic circuit diagram.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Switch 2 Tire 3 Car body 4 Solenoid valve 7 Front wheel 8 Rear wheel 65 Balance chamber 66 High pressure chamber 67 Eccentric cam 70 Air pump 71 Check valve 72 Pipe 80 Controller

Claims (3)

  A selection means for selecting an air pressure state of the tire (2) between a low pressure state and a high pressure state, comprising an electromagnetic valve (4) that switches to an air injection position for sending air from the neutral position to the tire (2) or an air bleeding position for removing air. (1) is provided, and the solenoid valve (4) is switched to an air injection position or an air bleeding position based on a selection operation of the selection means (1) to obtain a target low pressure state or high pressure state. A tire pressure control device for a work vehicle.   The work vehicle according to claim 1, wherein the air pressure of the tire (2) is provided so as to be automatically switchable between a high pressure state and a low pressure state according to a high speed position and a low speed position of the vehicle body (3) traveling speed change. Tire pressure control device.   2. The tire pressure control device for a work vehicle according to claim 1, wherein the tire air pressure control device comprises an air pump configured to reciprocate in a cylinder by forward or reverse rotation of a wheel.

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