JP4935224B2 - Mechanical steering device for work vehicle - Google Patents

Description

  The present invention relates to a mechanical steering device for a work vehicle such as a wheel crane.

  Conventionally, as a work vehicle such as a wheel crane, a lower traveling body in which at least two left and right wheels are respectively mounted on a plurality of axles, an upper revolving body that is rotatably mounted on the lower traveling body, What is provided in a revolving structure and is provided with a cab that serves as both a cockpit during work and a driver's cab during traveling is generally well known.

  Moreover, as a steering device for such a work vehicle, for example, as disclosed in Patent Document 1, a plurality of steering cylinders that respectively change the directions of the wheels are provided, and are rotated by a driver in the cab. An all-hydraulic type in which hydraulic oil is guided to a predetermined steering cylinder and steers each wheel in a predetermined direction in accordance with a mode selected by a steering handle rotation operation amount and a switch operation is often used. However, in this all-hydraulic steering device, the steering handle and the wheels are not mechanically connected so as to transmit the steering force mechanically, so the traveling speed is severely limited when traveling on general public roads.

Therefore, in order to avoid such a limitation, as disclosed in, for example, Patent Document 2, a steering force is applied from the steering handle to the front wheel, which is a wheel on the front axle, separately from the all-hydraulic steering device. Mechanical steering devices that transmit via gears and gears have been proposed and put into practical use. In this mechanical steering device, the steering cylinder assists the steering of the front wheels when the steering force from the steering handle is transmitted to the front wheels. Further, in order not to interfere with the turning of the upper swing body, a through-hole penetrating in the vertical direction is provided in the swivel joint arranged at the center of the upper swing body. An intermediate shaft, which is one transmission shaft, is inserted and arranged.
JP-A-5-39057 WO 97/46438 pamphlet

  However, the conventional mechanical steering device described above steers only the front wheels, and the wheels on the rear axle remain fixed in a straight traveling state. For this reason, there is a problem that the amount of skid of the tire is increased and the wear of the tire is accelerated.

  It is also known that when a mechanical steering device and a fully hydraulic steering device are used together, the wheels on the front axle are steered by the mechanical steering device, and the wheels on the rear axle are steered by the fully hydraulic steering device. However, in this case, the wheels on the rear axle are configured to be steered by the switch operation described above. Therefore, when the front and rear wheels are steered simultaneously, the driver needs to use both hands separately and simultaneously, which is difficult to operate and is not preferable from a safety standpoint.

  The present invention has been made in view of the above points, and an object of the present invention is to appropriately transmit the steering force to the wheels on the rear axle as well as the wheels on the front axle when the steering handle is steered. By adopting the configuration, it is an object of the present invention to provide a mechanical steering device for a work vehicle that can reduce tire wear by reducing the amount of tire slip and improve operability and safety.

  In order to solve the above-described problems, the invention according to claim 1 is directed to a lower traveling body in which wheels are steerable on a plurality of axles, and an upper revolving body that is rotatably mounted on the lower traveling body. And a steering wheel disposed in the cab as a mechanical steering device for a work vehicle, which is provided in the upper swing body and includes a cab that serves both as a cockpit during operation and a cab during operation. An upper revolving body side steering force transmission mechanism that transmits force to the lower traveling body side and a plurality of axles of the lower traveling body are arranged to increase the steering force transmitted from the upper revolving body side steering force transmission mechanism. A gear box that distributes in the direction, a lower traveling body front side steering force transmission mechanism that transmits one steering force distributed by the gear box to the wheels on the front axle, and the other steering that is distributed by the gear box A lower traveling body rear side steering force transmission mechanism that transmits the vehicle wheel to the wheels on the rear axle, and steers the wheels on the rear axle in phase with the wheels on the front axle when the steering handle is steered. Each steering force transmission mechanism is connected.

  In this configuration, when the driver in the cab steers the steering wheel while the work vehicle is traveling, the steering force is transmitted to the gear box via the upper turning body side steering force transmission mechanism, and is increased by this gear box. However, one of the steering forces is distributed to the wheels on the front axle via the lower traveling body front side steering force transmission mechanism, and the other steering force is rearized via the lower traveling body rear side steering force transmission mechanism. By being transmitted to the wheels on the side axle, the wheels on the front axle are steered in the steering direction of the steering handle, and the wheels on the rear axle are steered in phase with the wheels on the front axle. For this reason, the amount of tire slip on the wheels on the rear axle can be suppressed to reduce tire wear.

  Moreover, since the gear box that increases the steering force and distributes in two directions is disposed between the plurality of axles of the lower traveling body, the space for arranging the gear box and the ground height can be easily and sufficiently secured. In addition, the total transmission length of the entire steering force transmission mechanism on the lower traveling body side (that is, the lower traveling body front side steering force transmission mechanism and the lower traveling body rear side steering force transmission mechanism, etc.) can be shortened as much as possible. it can.

In addition to the above-described configuration , the invention according to claim 1 is configured so that the upper turning body side steering force transmission mechanism has an intermediate shaft that transmits a steering force across the upper turning body and the lower traveling body, In addition, the intermediate shaft is inserted into a through hole of a swivel joint arranged at the turning center of the upper turning body. In this configuration, since the intermediate shaft is inserted into the through-hole of the swivel joint arranged at the turning center of the upper swing body without separating the intermediate shaft of the upper swing body side steering force transmission mechanism up and down during work, This intermediate shaft does not hinder the turning of the upper turning body.

According to a second aspect of the present invention, in the mechanical steering device for a work vehicle according to the first aspect, a preferred form of the gear box is provided. That is, the base end of the arm is attached to the output shaft, and the transmission rod of the lower traveling body front side steering force transmission mechanism and the transmission rod of the lower traveling body rear side steering force transmission mechanism are connected to the distal end side of the arm. To do. In this configuration, by swinging one arm attached to the output shaft, the transmission rod of the lower traveling body front side steering force transmission mechanism and the transmission rod of the lower traveling body rear side steering force transmission mechanism are both in the longitudinal direction, which is the axial direction. Since the steering force is distributed in two directions, the steering force can be reliably distributed with a small number of parts.

According to a third aspect of the present invention, in the mechanical steering device for a work vehicle according to the second aspect , the output shaft of the gear box is disposed in the vehicle width direction, and the arm and the lower traveling body rear side steering force transmission mechanism are arranged. The connection location with the transmission rod is set so that the ground height is higher than the connection location between the arm and the transmission rod of the lower traveling body front side steering force transmission mechanism. In this configuration, the connection point between the transmission rod of the lower traveling body rear side steering force transmission mechanism and the arm of the gear box located near the center in the front-rear direction of the work vehicle is the same as the transmission rod of the lower traveling body front side steering force transmission mechanism. The ground clearance of the lower traveling body rear side steering force transmission mechanism is also increased, so that interference with road obstacles on rough roads etc. Absent.

The inventions according to claims 4 to 6 are directed to a work vehicle equipped with a mechanical steering device and an all-hydraulic steering device, and provide a preferred form of a mechanical stearin device for the work vehicle. .

That is, according to a fourth aspect of the present invention, in the mechanical steering device for a work vehicle according to any one of the first to third aspects, the direction of each wheel is a component of the all-hydraulic steering device. It is assumed that a steering cylinder for changing the above is provided. The steering force is applied by the steering cylinder when the steering force is transmitted to the wheels when the steering handle is steered. In this configuration, when the steering force is transmitted by the mechanical steering device during steering of the steering handle, the assist force is applied by the steering cylinder that is a component of the all-hydraulic steering device, which places a burden on the driver. Therefore, the wheel can be steered easily and reliably.

According to a fifth aspect of the present invention, in the mechanical steering device for a work vehicle according to the fourth aspect , the lower traveling body rear side steering force transmission mechanism is configured to transmit a steering force from the gear box to the wheels on the rear axle. A configuration having a blocking means capable of blocking transmission is adopted. In this configuration, when a fully hydraulic steering device is selected and used instead of a mechanical steering device at a work site or the like, the gear box is moved in advance to the wheel on the rear axle by the shut-off means of the lower traveling body rear steering force transmission mechanism. When the transmission of the steering force is cut off, for example, the wheels on the rear axle can be steered in the opposite phase to the wheels on the front axle by the fully hydraulic steering device.

Further, according to a sixth aspect of the present invention, in the mechanical steering device for a work vehicle according to the fifth aspect , the blocking means is a cylinder device that constitutes a transmission member of a lower traveling body rear side steering force transmission mechanism, and the cylinder. The expansion and contraction of the piston rod of the device is constituted by a lock mechanism that can be switched between a free state and a locked state. In this configuration, when the expansion / contraction of the piston rod of the cylinder device is in the locked state, the cylinder device performs a function as a transmission member of the lower traveling body rear side steering force transmission mechanism, while the piston mechanism of the cylinder device is expanded / contracted by the lock mechanism. When is switched to the free state, the function as a transmission member is not exhibited by the expansion and contraction of the piston rod, and transmission of the steering force from the gear box to the wheels on the rear axle is surely cut off.

  As described above, according to the mechanical steering device for a work vehicle in the present invention, when the driver steers the steering handle in the cab on the upper turning body side, the steering force is applied to the rear axle together with the wheels on the front axle. The wheel on the rear axle is steered to the same phase as the wheel on the front axle, reducing the amount of tire slip on the wheel on the rear axle and reducing tire wear. In addition, since the operation is easy, operability and safety can be improved. Moreover, since the gear box that increases the steering force and distributes in two directions is disposed between the plurality of axles of the lower traveling body, the space for arranging the gear box and the ground height can be easily and sufficiently secured. In addition, the total transmission length of the entire steering force transmission mechanism on the lower traveling body side can be shortened as much as possible, and it is highly practical in terms of weight reduction, cost reduction, and space saving. It has the effect.

In addition, since the intermediate shaft of the upper turning body side steering force transmission mechanism is inserted into the through-hole of the swivel joint arranged at the turning center of the upper turning body, it is not necessary to separate the intermediate shaft up and down during work. The intermediate shaft does not hinder the turning of the upper turning body, and is advantageous for implementation.

In particular, in the invention according to claim 2 , the transmission rod of the lower traveling body front side steering force transmission mechanism and the transmission rod of the lower traveling body rear side steering force transmission mechanism by the swing of one arm mounted on the output shaft of the gear box, Since both move in the longitudinal direction, which is the axial direction, and the steering force is distributed in two directions, it is possible to reliably distribute the steering force with a small number of parts, reducing weight, reducing costs, and saving space. Can be further planned.

In the invention according to claim 3 , the connection point between the transmission rod of the lower traveling body rear side steering force transmission mechanism and the arm of the gear box located near the center of the work vehicle in the front-rear direction is the transmission of the lower traveling body front side steering force transmission mechanism. The ground clearance is set to be higher than the connection point between the rod and the arm, and the ground clearance of the transmission rod of the lower traveling body rear side steering force transmission mechanism is also increased, so interference with road surface obstacles on bad roads etc. There is also an effect that can be prevented.

In the invention according to claim 4 , when the steering force is transmitted by the mechanical steering device during steering of the steering handle, the assist force is applied by the steering cylinder which is a component of the all-hydraulic steering device. It also has the effect that the steering of the wheel can be performed easily and reliably without imposing a burden.

In the invention according to claim 5, when the full hydraulic steering device is selectively used instead of the mechanical steering device at a work site or the like, the rear axle is separated from the gear box by the shut-off means of the lower traveling body rear steering force transmission mechanism in advance. If the transmission of the steering force to the upper wheel is cut off, the wheel on the rear axle can be freely steered by the fully hydraulic steering device, which is effective when used in combination with the fully hydraulic steering device. It is.

Further, in the invention according to claim 6 , when the expansion and contraction of the piston rod of the cylinder device is in the locked state, the cylinder device exhibits a function as a transmission member of the lower traveling body rear side steering force transmission mechanism, When the expansion and contraction of the piston rod of the device is switched to the free state, the function of the transmission member is not exhibited due to the expansion and contraction of the piston rod, and the transmission of the steering force from the gear box to the wheels on the rear axle can be reliably interrupted. Therefore, the operation reliability can be increased.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments that are the best mode for carrying out the present invention will be described below with reference to the drawings.

  1 to 4 show a work vehicle equipped with a mechanical steering device according to an embodiment of the present invention. Reference numeral 1 includes three axles, that is, a first axle 2, a second axle 3, and a third axle 4 from the front side. The left and right wheels 5L and 5R, 6L and 6R, and 7L and 7R are provided on the axles 2 to 4 of the lower traveling body 1, respectively. Reference numeral 8 denotes an upper swing body that is mounted on a mounting seat 9 of the lower traveling body 1 so as to be swingable via a swing bearing (not shown). A cab 10 serving both as a cockpit and a driving cab during traveling is provided, and a steering handle 11 that is rotated or steered by the driver is disposed in the cab 10.

  The wheels 5L, 5R, 6L, 6R, 7L, and 7R on each of the axles 2 to 4 are supported by the lower traveling body 1 via the knuckle arm 13 and the suspension device 14, respectively. Power of a mounted engine (not shown) is transmitted and transmitted through a propeller shaft or the like. Also, the knuckle arms 13 and 13 of the left and right wheels 5L and 5R, 6L and 6R, 7L and 7R on each axle 2 to 4 are connected to each other via tie rods 15, 16, and 17 extending in the vehicle width direction. The two left and right wheels 5L and 5R, 6L and 6R, and 7L and 7R on the axles 2 to 4 are provided so as to be integrally changeable in the same direction, that is, steerable.

  In the case of this embodiment, the mechanical steering device 30 according to the present invention is used as a steering device for steering the wheels 5L, 5R, 6L, 6R, 7L, and 7R on the axles 2 to 4 by rotating the steering handle 11. Apart from this, a fully hydraulic steering device 20 is provided in the work vehicle. This all-hydraulic steering device 20 includes six steering cylinders 21, 21, 22, 22, 23, which change the direction of each of the wheels 5L, 5R, 6L, 6R, 7L, and 7R on the axles 2 to 4, respectively. 23, and is configured to steer the wheels 5L, 5R, 6L, 6R, 7L, and 7R by guiding hydraulic oil to predetermined steering cylinders 21 to 23 in accordance with the rotation operation of the steering handle 11 and the selection mode. Further, although not shown, the all-hydraulic steering device 20 and the mechanical steering device 30 are selectively used by switching means.

  On the other hand, the mechanical steering device 30 includes an upper turning body side steering force transmission mechanism 32 that transmits a rotational operation force of the steering handle 11, that is, a steering force to the lower traveling body 1 side, as shown in an enlarged detail in FIG. As a constituent member of the upper swing body side steering force transmission mechanism 32, as shown in FIG. 6, the upper swing body side steering force transmission mechanism 32 is inserted into a through hole 33 provided through the swivel joint 31 in the vertical direction. Is disposed between the intermediate shaft 35 to which the steering force is transmitted from the intermediate shaft 35 via the bevel gear unit 34 and the first axle 2 and the second axle 3 of the lower traveling body 1. A gear box 38 that increases the steering force transmitted through the lower traveling body side first steering force transmission mechanism 37 and distributes the steering force in two directions, and one of the gear box 38 that is distributed by the gear box 38 The lower traveling body side second steering force transmission mechanism 39 as a lower traveling body front side steering force transmission mechanism for transmitting the steering force to the left wheel 5L on the first axle 2 and the other steering force distributed by the gear box 38 are used. A lower traveling body side third steering force transmission mechanism 40 as a lower traveling body rear side steering force transmission mechanism that transmits to the left wheel 6L on the second axle 3 is provided.

  The upper turning body side steering force transmission mechanism 32 has three transmission shafts 41, 42, 43 connected in series via universal joints and bevel gear units 44, 45, separately from the intermediate shaft 35 described above. The steering force is transmitted as rotational force around the transmission shafts 41 to 43 and the intermediate shaft 35. The lower traveling body side first steering force transmission mechanism 37 is formed by connecting two transmission shafts 46 and 47 with a universal joint and a bevel gear unit 48 interposed therebetween.

  In the gear box 38, the base end of the swing arm 52 is attached to the output shaft 51, and the transmission rod 55 of the lower traveling body side second steering force transmission mechanism 39 and the lower traveling body side first are connected to the distal end side of the swing arm 52. A transmission rod (specifically, a first transmission rod) 65 of the three steering force transmission mechanism 40 is connected. The output shaft 51 of the gear box 38 is disposed in the vehicle width direction, and the swing arm 52 is inclined rearward and downward when the steering angle of the steering handle 11 is zero. And the transmission rod 65 of the lower traveling body side third steering force transmission mechanism 40 are closer to the output shaft 51 than the connection portion of the swing arm 52 and the transmission rod 55 of the lower traveling body side second steering force transmission mechanism 39. The ground clearance is set high.

  The lower traveling body side second steering force transmission mechanism 39 includes one transmission rod 55, and one end (rear end) of the transmission rod 55 is connected to the front end side of the swing arm 52 of the gear box 38 as described above. On the other hand, the other end (front end) of the transmission rod 55 is connected to the knuckle arm 13 of the left wheel 5L on the first axle 2, and swings as a steering force from the swing arm 52 of the gear box 38. It is received as an axial force of the transmission rod 55 and transmitted to the left wheel 5L on the first axle 2. In addition, the lower traveling body side third steering force transmission mechanism 40 is disposed between the gear box 38 and the second axle 3 and is supported at its central portion so as to be swingable around the support shaft 61. 62, a second swing lever 64 disposed between the second axle 3 and the third axle 4 and having a central portion supported so as to swing about the support shaft 63, and a swing arm of the gear box 38 52, a first transmission rod 65 that connects one end (lower end) of the first swing lever 62 and the other end (upper end) of the first swing lever 62 and one end (second end) of the second swing lever 64 (see FIG. A second transmission rod 66 that connects the upper end of the second axle 3 while bypassing the upper side of the second axle 3, and the other end (lower end) of the second swing lever 64 and the knuckle of the left wheel 6L on the second axle 3. A cylinder device 70 as a third transmission rod or transmission member for connecting the arm 13; The first and second transmission rods 65 and 66 and the shaft of the cylinder device 70 are swung from the swing arm 52 of the gear box 38 as a steering force. It is received as force and transmitted to the left wheel 6L on the second axle 3.

  Thus, the mechanical steering device 30 transmits the steering force to the wheels 5L and 5R on the first axle 2 to steer the wheels 5L and 5R on the first axle 2 when the steering handle 11 is steered. The wheels 6L, 6R on the second axle 3 are also transmitted to steer the wheels 6L, 6R on the second axle 3 in phase with the wheels 5L, 5R on the first axle 2. The mechanical steering device 30 is not shown, but when the steering force is transmitted to the wheels 5L and 5R on the first axle 2 and the wheels 6L and 6R on the second axle 3 when the steering handle 11 is steered. By sensing the transmission and operating the steering cylinder 21 on the first axle 2 side and the steering cylinder 22 on the second axle 3 side, an assist force is applied to the steering of each wheel 5L, 5R, 6L, 6R. Is configured to do.

  As shown in detail in FIG. 7, the cylinder device 70 is a hollow cylinder 71, is slidably disposed in the cylinder 71, and the first air chamber 72 and the second air chamber 73 are disposed in the cylinder 71. And a piston rod 75 provided through the piston 74 and straddling the inside and outside of the cylinder 71, and a high pressure from the first air supply port 76 to the first air chamber 72 in the cylinder 71. When air is supplied, the piston 74 slides closer to the second air chamber 73 in the cylinder 71, and the piston rod 75 enters deep into the cylinder 71 and the length outside the cylinder 71 contracts, while the second air supply port 77. When high pressure air is supplied from the first to the second air chamber 73 in the cylinder 71, the piston 74 slides closer to the first air chamber 72 in the cylinder 71 and the piston rod 75 extends outside the cylinder 71. The length outside the cylinder 71 is adapted to extend to. The cylinder device 70 also has a lock mechanism 80 that can switch the expansion and contraction of the piston rod 75 between a free state and a locked state, and the lower traveling body side third steering force transmission is achieved by the lock mechanism 80 and the cylinder device 70. In the mechanism 40, a blocking means 100 capable of blocking the transmission of the steering force from the gear box 38 to the left wheel 6L on the second axle 3 is configured.

  As shown in detail in FIG. 8, the lock mechanism 80 includes a lock sleeve 81 that is slidably disposed in the axial direction in a space between the outer cylinder portion 71 a and the inner cylinder portion 71 b of the cylinder 71, and the lock mechanism 80. A spherical main lock detent 84 that engages with an annular groove 83 provided in the piston rod 75 from an insertion hole 82 provided in the inner cylinder portion 71b of the cylinder 71 corresponding to the sleeve 81, and the lock sleeve 81 in one direction at all times. A lock sleeve spring 85 to be biased, a sub-block detent 88 engaged with a recess 86 formed on the outer peripheral surface of the lock sleeve 81 through an insertion hole 87 provided in the outer cylinder portion 71a of the cylinder 71, and the sub-block detent 88 Corresponding to the lock release switch 89 attached to the outer peripheral surface of the outer cylindrical portion 71a of the cylinder 71, the outer cylindrical portion 71a of the cylinder 71, In order to supply high-pressure air into the air chamber 90 opposite to the sleeve lock spring 85 of the lock sleeve 81 between the cylinder portion 71b and an air supply port 91 provided in the outer cylinder portion 71a of the cylinder 71. ing. When high-pressure air is removed from the air chamber 90, the lock sleeve 81 keeps the main lock detent 84 engaged with the annular groove 83 of the piston rod 75 as shown in the figure, and the lock release switch 89 is turned off. By engaging the sub-block detent 88 with the recess 86 of the lock sleeve 81, the piston rod 75 is brought into a locked state in which expansion and contraction is restricted. On the other hand, when releasing this locked state, first, the lock release switch 89 is turned on, and the sub-block detent 88 is extracted from the recess 86 of the lock sleeve 81 by magnetic force, and then the high pressure air is supplied from the air supply port 91 into the air chamber 90. Is supplied, the lock sleeve 81 slides to the right in the figure against the urging force of the lock sleeve spring 85, and the main lock detent 84 enters the recess 92 formed on the inner peripheral surface of the lock sleeve 81 and enters the piston rod 75. By releasing from the annular groove 83, the locked state is released, and the expansion and contraction of the piston rod 75 becomes free. 7 and 8, reference numeral 95 denotes a space between the outer cylinder portion 71 a and the inner cylinder portion 71 b of the cylinder 71, which communicates with the arrangement side of the sleeve lock spring 85 and is provided on the outer cylinder portion 71 a of the cylinder 71. The drain port.

  Next, the operation of the above embodiment, particularly the operation of the mechanical steering device 30, will be described. When the driver in the cab 10 steers the steering handle 11 while the work vehicle is traveling, the steering force is It is transmitted to the gear box 38 via the steering force transmission mechanism 33 and the lower traveling body side first steering force transmission mechanism 37 and is distributed in two directions while being increased in this gear box 38, and one of the steering forces of the lower traveling The other steering force is applied to the wheels 5L, 5R on the first axle 2 via the body side second steering force transmission mechanism 39, and the other steering force is applied to the wheels 6L, 5L, 5R on the second axle 3 via the lower traveling body side third steering force transmission mechanism 40. By being transmitted to 6R, the wheels 5L and 5R on the first axle 2 are steered in the steering direction of the steering handle 11, and the wheels 6L and 6R on the second axle 3 are Wheels 5L on the shaft 2 are steered to the 5R and the same phase. For this reason, it is possible to reduce the amount of tire slip on the wheels 6L and 6R on the second axle 3, thereby reducing tire wear. Further, since the operation is easy only by steering the handle 11, both operability and safety can be improved.

  In addition, since the gear box 38 is disposed between the first axle 2 and the second axle 3 of the lower traveling body 1, the space for arranging the gear box 38 and the ground height can be easily and sufficiently secured. The entire lower steering body side steering force transmission mechanism (that is, the lower traveling body side first steering force transmission mechanism 37, the lower traveling body side second steering force transmission mechanism 39, and the lower traveling body side third steering force transmission mechanism 40). Can be made as short as possible. As a result, it is possible to contribute to weight reduction, cost reduction, space saving, and the like, and there is an effect excellent in practicality.

  Particularly, in the case of the present embodiment, the gear box 38 is connected to the transmission rod 55 of the lower traveling body side second steering force transmission mechanism 39 and the lower traveling body side first by the swing of one swing arm 52 attached to the output shaft 51. Since the first transmission rod 65 of the three steering force transmission mechanism 40 moves in the longitudinal direction, which is the axial direction, and distributes the steering force in two directions, the steering force is reliably distributed with a small number of parts. Thus, weight reduction, cost reduction, and space saving can be further achieved. In addition, the connection point between the first transmission rod 65 of the lower traveling body side third steering force transmission mechanism 40 and the swing arm 52 of the gear box 38 located near the center in the front-rear direction of the work vehicle is the lower traveling body side second steering force transmission. It is provided at a position where the ground height is higher than the connection point between the transmission rod 55 of the mechanism 39 and the swing arm 52, and the ground height of the first transmission rod 65 of the lower traveling body side third steering force transmission mechanism 40 is also high. Therefore, there is an effect that interference with a road surface obstacle can be prevented on a rough road or the like.

  The upper turning body side steering force transmission mechanism 32 includes an intermediate shaft 35 that transmits a steering force between the upper turning body 8 and the lower traveling body 1. Since it is inserted into the through-hole 33 of the swivel joint 31 disposed at the center of rotation of the revolving structure 8, the intermediate shaft 35 does not interfere with the turning of the upper revolving structure 8 during work at the work site. This is effective for implementation.

  In addition, when the steering force is transmitted to the wheels 5L and 5R on the first axle 2 and the wheels 6L and 6R on the second axle 3 by the mechanical steering device 30 when the steering handle 11 is steered as described above, Since the steering cylinder 21 on the first axle 2 side and the steering cylinder 22 on the second axle 3 side, which are components of the steering device 20, are actuated to give assist force, without burdening the driver, The wheels 5L and 5R on the first axle 1 and the wheels 6L and 6R on the second axle 3 can be easily and reliably steered.

  Further, when the full hydraulic steering device 20 is selectively used instead of the mechanical steering device 30 at a work site or the like, the second axle 3 is connected from the gear box 38 by the shut-off means 100 of the lower traveling body side third steering force transmission mechanism 40 in advance. If transmission of the steering force to the upper wheels 6L and 6R is cut off, for example, the wheels 6L and 6R on the second axle 3 are reversed in phase with the wheels 5L and 5R on the first axle 2 by the fully hydraulic steering device 20. Therefore, it is effective when used in combination with the all-hydraulic steering device 20.

  In addition, the blocking means 100 can switch the expansion and contraction of the cylinder device 70 constituting the transmission member of the lower traveling body side third steering force transmission mechanism 40 and the piston rod 75 of the cylinder device 70 between a free state and a locked state. Therefore, the function of transmitting / blocking the steering force can be surely exhibited. In other words, when the expansion and contraction of the Pillton rod 75 of the cylinder device 70 is in the locked state, the cylinder device 70 functions as a transmission member of the lower traveling body side third steering force transmission mechanism 40, while the lock mechanism 80 causes the piston of the cylinder device 70 to function. When the expansion and contraction of the rod 75 is switched to the free state, the function of the transmission member is not exhibited by the expansion and contraction of the piston rod 75, and the transmission of the steering force is reliably interrupted.

  In addition, this invention is not limited to the said embodiment, A various other form is included. For example, in the above-described embodiment, in the lower traveling body side third steering force transmission mechanism 40 as the lower traveling body rear side steering force transmission mechanism, one steering force distributed by the gear box 38 is used as the second axle as the rear axle. 3 and the third axle 4 are configured to transmit only to the wheels 6L and 6R on the second axle 3, but the present invention is arranged on the wheels 6L and 6R on the second axle 3 and the third axle 4. The lower traveling body rear side steering force transmission mechanism may be configured to transmit the steering force to both the wheels 7L and 7R.

  Further, in the above embodiment, the steering force straddling between the upper swing body 8 and the lower travel body 1 in the upper swing body side steering force transmission mechanism 32 that transmits the steering force of the steer handle 11 to the lower travel body 1 side. The intermediate shaft 35 is configured to be inserted into the through-hole 33 of the swivel joint 31 disposed at the center of rotation of the upper swing body 8. The arrangement position is not limited to the through-hole 33 of the swivel joint 31 and may be arranged in another part. However, in that case, it is necessary to provide the intermediate shaft so that it can be separated vertically so as not to hinder the turning of the upper turning body 8 during the work.

  Furthermore, the present invention is not limited to a three-axle and six-wheel work vehicle as in the above-described embodiment, and is a mechanical steering device for a multi-axle and multi-wheel work vehicle in which wheels are provided on a plurality of axles in a steerable manner. Can be widely applied.

It is a side view showing composition of a mechanical steering device of a work vehicle concerning an embodiment of the present invention. It is also a plan view. It is the perspective view which looked at the structure of the lower traveling body side part of the said mechanical steering apparatus from the upper direction. It is the perspective view similarly seen from the bottom. FIG. 2 is an enlarged view of the vicinity of the gear box in FIG. 1. It is an expanded sectional view in the XX line of FIG. It is a side view of a cylinder apparatus. It is a longitudinal cross-sectional view which shows the structure of the locking mechanism of the said cylinder apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lower traveling body 2, 3, 4 Axle 5L, 5R, 6L, 6R, 7L, 7R Wheel 8 Upper turning body 10 Cab 11 Steering handle 20 Full hydraulic steering device 21, 22, 23 Steering cylinder 30 Mechanical steering device 31 Swivel joint 32 Upper turning body side steering force transmission mechanism 33 Through hole 35 Intermediate shaft 38 Gear box 39 Lower traveling body side second steering force transmission mechanism (lower traveling body front side steering force transmission mechanism)
40 Lower traveling body side third steering force transmission mechanism (lower traveling body rear side steering force transmission mechanism)
51 Output shaft 52 Swing arm 55 Transmission rod of lower traveling body side second steering force transmission mechanism 65 First transmission rod of lower traveling body side third steering force transmission mechanism 70 Cylinder device (transmission member)
75 Piston rod 80 Lock mechanism 100 Blocking means

Claims (6)

A lower traveling body in which wheels are steerable on a plurality of axles, an upper revolving body that is turnably mounted on the lower traveling body, and a cockpit at the time of work provided on the upper revolving body A mechanical steering device for a work vehicle having a cab that also serves as a driver's cab during traveling,
An upper turning body side steering force transmission mechanism for transmitting a steering force of a steering handle disposed in the cab to the lower traveling body side;
A gear box that is disposed between a plurality of axles of the lower traveling body and increases the steering force transmitted from the upper turning body side steering force transmission mechanism and distributes it in two directions;
A lower traveling body front side steering force transmission mechanism that transmits one steering force distributed by the gear box to a wheel on the front axle;
A lower traveling body rear side steering force transmission mechanism that transmits the other steering force distributed by the gear box to the wheels on the rear axle;
Each steering force transmission mechanism is coupled so as to steer the wheels on the rear axle in phase with the wheels on the front axle when the steering handle is steered ,
The upper turning body side steering force transmission mechanism has an intermediate shaft that transmits a steering force straddling between the upper turning body and the lower traveling body, and this intermediate shaft is a swivel disposed at the turning center of the upper turning body. A mechanical steering device for a work vehicle, wherein the mechanical steering device is inserted into a through hole of a joint . In the gear box, the base end of the arm is attached to the output shaft, and the transmission rod of the lower traveling body front side steering force transmission mechanism and the transmission rod of the lower traveling body rear side steering force transmission mechanism are connected to the distal end side of the arm. mechanical steering device for a work vehicle according to claim 1 that is. The output shaft of the gear box is arranged in the vehicle width direction, and the connection point between the arm and the transmission rod of the lower traveling body rear side steering force transmission mechanism is the transmission of the arm and the lower traveling body front side steering force transmission mechanism. The mechanical steering device for a work vehicle according to claim 2, wherein the ground height is set to be higher than a connection position with the rod . A steering cylinder for changing the direction of each wheel is provided, and an assist force is applied by the steering cylinder when the steering force is transmitted to the wheel when the steering handle is steered. The mechanical steering device for a work vehicle according to any one of claims 3 to 4 . 5. The mechanical steering device for a work vehicle according to claim 4, wherein the lower traveling body rear side steering force transmission mechanism has blocking means capable of blocking transmission of steering force from the gear box to the wheels on the rear axle. . The shut-off means comprises a cylinder device that constitutes a transmission member of a lower traveling body rear side steering force transmission mechanism, and a lock mechanism that can switch expansion and contraction of a piston rod of the cylinder device between a free state and a locked state. The mechanical steering device for a work vehicle according to claim 5.