Work vehicle

Abstract

The present invention provides a work vehicle that can suitably change the steering angle of the front wheels. [Solution] The system comprises a drive force transmission shaft 30 positioned with its axis facing the front-rear direction and to which the driving force of the engine 3 is transmitted; a transmission shaft 41 positioned with its axis facing the left-right direction and to which the driving force from the drive force transmission shaft 30 is transmitted to the left and right front wheels 6; a front axle case 50 housing the transmission shaft 41; and a steering cylinder 60 that can change the steering angle of the front wheels 6 and is provided in the front axle case 50 so as to be located above the transmission shaft 41.

Description

Technical Field

[0001] The present invention relates to the technology of work vehicles.

Background Art

[0002] Conventionally, the technology of work vehicles has been known. For example, it is as described in Patent Document 1.

[0003] Patent Document 1 describes a tractor. The tractor includes a front axle mechanism composed of a front axle case that houses the axle of the front wheels and a steering cylinder connected to the front axle case. The front axle mechanism changes the cut angle by swinging the front wheels around a fulcrum provided on the front axle case by expanding and contracting the steering cylinder.

[0004] Here, in the front axle mechanism as described above, depending on the position of the steering cylinder with respect to the axle, it may be difficult to sufficiently ensure the cut angle of the front wheels with respect to the expansion and contraction amount of the steering cylinder, and it may be difficult to suitably change the cut angle of the front wheels.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] One aspect of the present disclosure has been made in view of the above situation, and the problem to be solved is to provide a work vehicle capable of suitably changing the cut angle of the front wheels.

Means for Solving the Problems

[0007] The problem that one aspect of this disclosure aims to solve is as described above, and the means for solving this problem will now be explained.

[0008] A work vehicle according to one aspect of the present disclosure comprises: a drive force transmission shaft arranged with its axis facing the front-rear direction and through which the driving force of the engine is transmitted; a transmission shaft arranged with its axis facing the left-right direction and through which the driving force from the drive force transmission shaft is transmitted to the left and right front wheels; a front axle case housing the transmission shaft; and a steering cylinder that can change the steering angle of the front wheels and is provided in the front axle case so as to be located above the transmission shaft. According to one aspect of this disclosure, the steering angle of the front wheels can be suitably changed.

[0009] A work vehicle according to one aspect of the present disclosure comprises a body frame that supports the front axle case from above, and the body frame has a first recess formed therein that is recessed upward and in which the steering cylinder can be arranged inside. According to one aspect of this disclosure, the height of the vehicle's hood can be reduced.

[0010] A work vehicle according to one aspect of the present disclosure is equipped with a suspension device that absorbs vibrations transmitted from the front axle case to the vehicle frame, the suspension device being equipped with a suspension cylinder that connects the vehicle frame and the front axle case and is positioned forward of the first recess. According to one aspect of this disclosure, the reduction in rigidity of the vehicle body frame due to the provision of the first recess can be suppressed.

[0011] The suspension cylinder according to one aspect of this disclosure is provided at the front end of the vehicle frame. According to one aspect of this disclosure, the strength of the front portion of the vehicle frame can be improved.

[0012] A work vehicle according to one aspect of the present disclosure comprises a body frame that supports the front axle case from above, and a second recess is formed in the portion of the body frame rearward of the front axle case, so as to avoid interference with the front wheel, and the recess is recessed toward the left-right center of the body frame. According to one aspect of this disclosure, the steering angle of the front wheels can be ensured by avoiding interference between the vehicle frame and the front wheels.

[0013] A work vehicle according to one aspect of the present disclosure comprises a body frame that supports the front axle case from above, the body frame having a cast portion made of casting, and the cast portion having a guide portion capable of guiding a linear member. According to one aspect of this disclosure, a guide portion capable of guiding a linear member can be formed by utilizing a cast portion of the vehicle frame that is easily formed into a complex shape.

[0014] The cast portion according to one aspect of the present disclosure is provided with ribs protruding in a predetermined direction, and the guide portion is formed in a groove shape partitioned by the ribs. According to one aspect of this disclosure, a guide portion can be formed using ribs that reinforce the vehicle body frame. [Brief explanation of the drawing]

[0015] [Figure 1] A side view showing the overall configuration of a tractor according to one aspect of this disclosure. [Figure 2] A perspective view showing the tractor's body frame, drive shaft, front axle case, steering cylinder, and suspension system. [Figure 3] A side view showing the tractor's body frame, drivetrain shaft, front axle case, steering cylinder, and suspension system. [Figure 4] An exploded perspective view showing the tractor's chassis frame, drivetrain shaft, front axle case, steering cylinder, and suspension system. [Figure 5] A perspective view showing the vehicle frame. [Figure 6] Plan view showing the vehicle body frame. [Figure 7] Exploded perspective view showing the driving force transmission shaft, front axle case and steering cylinder. [Figure 8] Front view schematically showing the front axle case and the steering cylinder. [Figure 9] Plan view schematically showing the front axle case and the steering cylinder. [Figure 10] (a) Front view schematically showing a conventional front axle case and steering cylinder. (b) Plan view schematically showing a conventional front axle case and steering cylinder.

Mode for Carrying Out the Invention

[0016] Hereinafter, the directions indicated by the arrows U, D, F, B, L and R in the drawings will be defined as the upward direction, downward direction, forward direction, rearward direction, leftward direction and rightward direction, respectively, for explanation.

[0017] First, the overall configuration of the tractor 1 according to one aspect of the present disclosure will be described.

[0018] The tractor 1 shown in FIG. 1 mainly includes a vehicle body frame 2, an engine 3, a bonnet 4, a transmission case 5, front wheels 6, rear wheels 7, fenders 8, a lifting device 9, a cabin 10, a driving force transmission shaft 30, a front axle 40, a front axle case 50, a steering cylinder 60 and a suspension device 70.

[0019] The vehicle body frame 2 is a member to which the engine 3 and the like are fixed. The detailed description of the configuration of the vehicle body frame 2 will be described later. The vehicle body frame 2 is disposed at the front portion of the tractor 1. The engine 3 is covered by the bonnet 4. A transmission case 5 is fixed to the rear portion of the engine 3. A muffler 4a for discharging the exhaust gas of the engine 3 is disposed on the right side of the bonnet 4.

[0020] The transmission case 5 houses the power transmission mechanism (not shown). A clutch housing (not shown) is provided in front of the transmission case 5, which houses the power transmission mechanism (transmission, clutch, etc.).

[0021] The front of the vehicle frame 2 is supported by a pair of front wheels 6 via a front axle mechanism (front axle case 50 and steering cylinder 60, described later). The front axle mechanism is connected to the vehicle frame 2 via a suspension device 70, described later (see Figure 3). The rear of the transmission case 5 is supported by a pair of rear wheels 7 via a rear axle mechanism (not shown). The pair of rear wheels 7 are generally covered from above by fenders 8.

[0022] A lifting device 9 is provided at the rear of the transmission case 5. Various work devices (for example, a tiller, etc.) can be attached to the lifting device 9. The lifting device 9 can raise and lower the attached work devices using actuators such as hydraulic cylinders.

[0023] The power from engine 3 is shifted by a transmission (not shown) housed in the clutch housing, and then transmitted to the front axle mechanism via a drive force transmission shaft 30 (see Figure 7), and subsequently to the front wheels 6 via the front axle mechanism. The power shifted by the transmission is then transmitted to the rear wheels 7 via the rear axle mechanism. In this way, the power from engine 3 rotates the front wheels 6 and the rear wheels 7, allowing the tractor 1 to move. The power from engine 3 can also be used to drive the work equipment mounted on the lifting device 9.

[0024] A cabin 10 is located behind the engine 3. The cabin 10 is mounted on the vehicle body (transmission case 5, etc.). Inside the cabin 10, a living space for the driver is formed. A seat 11 for the driver is placed in the living space. A steering wheel 12 for adjusting the steering angle of the front wheels 6 is located at the front of the cabin 10. Depending on the amount the steering wheel 12 is operated, a steering cylinder 60 (described later) is activated, and the steering angle of the front wheels 6 is changed.

[0025] The following describes the configuration of the vehicle frame 2, the drive force transmission shaft 30, the front axle 40, the front axle case 50, the steering cylinder 60, and the suspension system 70.

[0026] The vehicle frame 2 shown in Figures 3, 5, and 6 is formed in a long, rectangular shape in the front-to-rear direction. In addition to the engine 3 described above, equipment (battery, radiator, air cleaner device, etc.) located inside the bonnet 4 is fixed to the vehicle frame 2. The vehicle frame 2 according to this embodiment is composed of a cast part 20, which is a part made of cast iron, and a predetermined sheet metal for fixing predetermined members to the cast part 20. The cast part 20 constitutes the main part of the vehicle frame 2. The cast part 20 is connected to the front axle mechanism (front axle case 50 and steering cylinder 60) via a suspension device 70, which will be described later (see Figure 3). The cast part 20 comprises a first part 21 and a second part 28.

[0027] The first part 21 constitutes the front part of the cast iron section 20. Equipment located in the front of the bonnet 4 (such as a battery, radiator, and air cleaner unit) is mounted on the first part 21. The first part 21 is formed in a roughly box shape with openings at the top and rear. The rear part of the first part 21 is formed so that the vertical dimension gradually increases towards the rear (see Figure 3). The first part 21 comprises side sections 23 and a front section 24. The first part 21 comprises a bottom section 25 having a guide section 25b, which will be described later. The first part 21 comprises a first recess 26. The first part 21 comprises a second recess 27.

[0028] The side portions 23 constitute the left and right side walls of the first portion 21. The side portions 23 are formed to be elongated in the front-rear direction. The left and right side portions 23 are formed to be generally symmetrical with respect to each other. The side portions 23 are equipped with connecting portions 23a.

[0029] The connecting portion 23a is the part to which the upper end of the suspension cylinder 72, which will be described later, is connected. The connecting portion 23a is connected to the suspension cylinder 72 via a predetermined connecting shaft whose axis is oriented in the left-right direction. The connecting portion 23a has a hole through which the connecting shaft is inserted. The connecting portion 23a is provided on the left and right side portions 23 that face outward in the left-right direction. As shown in Figures 3 and 5, the connecting portion 23a is provided at the front end of the side portion 23.

[0030] The front portion 24 shown in Figures 5 and 6 constitutes the front wall of the first portion 21. The front portion 24 is formed to connect the front ends of the left and right side portions 23. As shown in Figure 5, the front portion 24 has a recess formed by cutting out the upper end so that it is recessed downwards. The front portion 24 can be provided with a support portion 24a for fixing weights or the like. The support portion 24a is formed, for example, by combining sheet metal.

[0031] The bottom portion 25 constitutes the bottom wall of the first portion 21. The bottom portion 25 has a rib 25a and a guide portion 25b.

[0032] Rib 25a is a portion formed to protrude upward from the bottom portion 25. Rib 25a is formed to extend in the front-rear direction. Rib 25a is formed on the front portion of the bottom portion 25 (first portion 21). Rib 25a is formed on both the left and right sides of the front portion 24. The left and right ribs 25a are each formed to be located towards the left-right center of the bottom portion 25, at a predetermined distance from the left and right sides 23. An opening is formed between the left and right ribs 25a, penetrating the bottom portion 25 in the vertical direction.

[0033] The guide portion 25b is a portion capable of guiding a predetermined linear member. The linear member can be a hose connected to a predetermined cylinder (for example, a steering cylinder 60 or a suspension cylinder 72), a harness connected to a predetermined device, a wire, or other such member. The guide portion 25b is formed to extend in the front-rear direction. The guide portion 25b is formed on both the left and right sides of the first portion 21. In this embodiment, the guide portion 25b is formed in a groove shape demarcated by a side portion 23, a rib 25a, and a bottom portion 25.

[0034] The first recess 26 shown in Figures 3 and 5 is a portion formed in the lower part of the first section 21, recessed upwards. Figure 3 shows a schematic, enlarged view of the portion of the first section 21 in which the first recess 26 is formed (the portion enclosed by the dashed line). The first recess 26 is formed in the front part of the first section 21. More specifically, the first recess 26 is formed in a position close to the connecting portion 23a of the side section 23 in the front-rear direction, and is positioned behind the connecting portion 23a. The first recess 26 is formed in a shape that allows the steering cylinder 60, which will be described later, to be placed inside. More specifically, the front-rear dimension of the first recess 26 is formed to be larger than the front-rear dimension of the portion of the steering cylinder 60 that overlaps with the first section 21 in a plan view (bottom view) (for example, the cylinder tube 61, which will be described later). Also, the vertical dimension of the first recess 26 is formed to be larger than the vertical dimension of the portion of the steering cylinder 60 that overlaps with the first section 21 in a plan view.

[0035] As shown in Figures 3 and 5, the rib 25a and guide portion 25b according to this embodiment are formed to straddle the first recess 26 in the front-rear direction. More specifically, the rib 25a and guide portion 25b are formed to overlap with the first recess 26 in a plan view. In addition, the rib 25a and guide portion 25b are formed to curve in accordance with the shape of the first recess 26 in a side view (see Figure 3). With the above configuration, the portion of the cast iron part 20 (vehicle frame 2) in which the first recess 26 is formed can be reinforced with the rib 25a.

[0036] The second recess 27 shown in Figures 3, 5, and 6 is a portion formed to be recessed toward the left-right center of the cast part 20 (vehicle frame 2). The second recess 27 is formed on the rear portion of the side part 23. The second recess 27 is formed by curving the side part 23. More specifically, as shown in Figure 6, the left and right side parts 23 are curved so that their intermediate portions in the front-rear direction are close to each other, and the second recess 27 is formed by this curved portion.

[0037] The second part 28 constitutes the rear portion of the cast part 20. The second part 28 is formed to extend rearward from the left and right side portions 23 of the first part 21. The left and right second parts 28 are fixed to the rear ends of the left and right side portions 23 using fasteners such as bolts. The left and right second parts 28 secure the engine 3 by sandwiching it in the left and right direction.

[0038] The drive force transmission shaft 30 shown in Figures 3 and 7 transmits power from the engine 3 (transmission) to the front axle 40, which will be described later. The drive force transmission shaft 30 is formed in a roughly cylindrical shape with its axis generally oriented in the front-rear direction. A gear (not shown), such as a bevel gear, is provided at the front end of the drive force transmission shaft 30 to transmit driving force (rotation) to the front axle 40.

[0039] The front axle 40 shown in Figure 8 constitutes the axle for the left and right front wheels 6. The front axle 40 transmits the rotation transmitted from the drive force transmission shaft 30 to the left and right front wheels 6. The front axle 40 comprises a transmission shaft 41, a connecting shaft 42, and a fixed part 43. Various gears for transmitting rotation can be provided on the transmission shaft 41, the connecting shaft 42, and the fixed part 43.

[0040] The transmission shaft 41 is the part to which the driving force from the driving force transmission shaft 30 is transmitted. The transmission shaft 41 is positioned with its axis oriented in the left-right direction.

[0041] The connecting shaft 42 is the part that transmits the rotation of the transmission shaft 41 to the fixed part 43, which will be described later. The connecting shaft 42 is positioned with its axis generally oriented in the vertical direction. The connecting shaft 42 is provided on both the left and right sides of the transmission shaft 41.

[0042] The fixing part 43 is the part to which the front wheel 6 is fixed. The fixing part 43 transmits the rotation of the left and right connecting shafts 42 to the left and right front wheels 6, respectively. The fixing part 43 has a shaft portion 43a whose axis is generally oriented in the left-right direction. The fixing part 43 rotates around the shaft portion 43a by the driving force transmitted from the connecting shafts 42 via the shaft portion 43a.

[0043] The front axle case 50 shown in Figures 3, 7, and 8 houses the front axle 40. The front axle case 50 is formed in a hollow shape. Together with the steering cylinder 60, which will be described later, the front axle case 50 constitutes the front axle mechanism. The front axle case 50 is located below the vehicle body frame 2. As shown in Figures 2 and 3, the front axle case 50 is connected to the vehicle body frame 2 via a suspension device 70, which will be described later. The front axle case 50 is located in front of the second recess 27 of the vehicle body frame 2 (first portion 21). The front axle case 50 comprises a main body portion 51 and a swinging portion 52.

[0044] The main body 51 is the primary structure of the front axle case 50. The main body 51 is formed in a roughly cylindrical shape that is elongated in the left-right direction. As shown in Figure 8, the transmission shaft 41 is housed inside the main body 51. The oscillating member 71 of the suspension device 70, which will be described later, is fixed to the lower surface of the main body 51. The main body 51 is equipped with a cylinder holding portion 51a.

[0045] The cylinder holder portion 51a shown in Figure 7 supports the steering cylinder 60, which will be described later. The cylinder holder portion 51a is formed in a shape that opens in the left-right direction, and the steering cylinder 60 is arranged in the space inside. The cylinder holder portion 51a holds the steering cylinder 60 so that it is located within the first recess 26. The cylinder holder portions 51a are provided at intervals in the left-right direction so that they are located on both sides of the main body portion 51 in the left-right direction. The cylinder holder portion 51a is provided on the upper front of the main body portion 51 at an angle. More specifically, as shown in Figure 7, the cylinder holder portion 51a is provided on the front part of the upper surface of the main body portion 51.

[0046] The oscillating part 52 rotatably supports the connecting shaft 42 and the fixed part 43, and oscillates relative to the main body 51. In Figure 8, the oscillating part 52 is shown as a solid color. As shown in Figure 3, the oscillating part 52 is formed in a substantially circular shape in a side view. The oscillating part 52 is formed in a hollow shape. The shaft portion 43a of the connecting shaft 42 and the fixed part 43 is housed inside the oscillating part 52. The oscillating parts 52 are positioned on both the left and right sides of the main body 51. As shown in Figure 8, the oscillating part 52 is pivotably connected to the main body 51 around the pivot axis 52a, which is shown by the dashed line. The pivot axis 52a is positioned with its axis generally oriented in the vertical direction. The oscillating part 52 oscillates relative to the main body 51 by the operation of the steering cylinder 60, which will be described later. The pivot axis 52a is positioned generally coaxially with the connecting shaft 42. The oscillating part 52 has an arm 52b.

[0047] The arm 52b shown in Figures 7 to 9 is the part to which the tie rod end 63a of the steering cylinder 60, which will be described later, is connected. The arm 52b is provided so as to protrude diagonally forward and upward from the pivoting part 52 (see Figures 3 and 7).

[0048] The steering cylinder 60 shown in Figures 7 to 9 is capable of changing the steering angle of the front wheels 6 according to the amount of steering wheel 12 is operated. The steering cylinder 60 constitutes a power steering mechanism that assists steering using hydraulics. The steering cylinder 60 comprises a cylinder tube 61, a cylinder rod 62, and a tie rod 63.

[0049] The cylinder tube 61 constitutes the housing of the steering cylinder 60. The cylinder tube 61 is formed in a substantially cylindrical shape that is elongated in the left-right direction. Oil from an appropriate pump (not shown) is supplied to the inside of the cylinder tube 61 via a predetermined hose. The cylinder tube 61 is held by the cylinder holder 51a by being positioned inside the opening of the cylinder holder 51a.

[0050] The cylinder rod 62 moves from side to side as the piston (not shown) is pushed by the hydraulic pressure inside the cylinder tube 61. The cylinder rod 62 is formed in an elongated shape in the left-right direction. The cylinder rod 62 protrudes from both the left and right sides of the cylinder tube 61.

[0051] The tie rod 63 transmits the movement of the cylinder rod 62 to the oscillating part 52. The tie rod 63 is provided on both the left and right sides of the cylinder rod 62. The tie rod 63 connects the left and right ends of the cylinder rod 62 to the arms 52b of the oscillating part 52. The tie rod 63 is equipped with tie rod ends 63a.

[0052] The tie rod end 63a is the part that connects to the arm 52b of the swinging part 52. The tie rod end 63a is rotatably connected to the arm 52b, with the connecting shaft 63b having its axis oriented roughly in the vertical direction.

[0053] In the power steering mechanism equipped with the steering cylinder 60 described above, a steering valve (not shown) is driven according to the amount of operation of the steering wheel 12, thereby supplying oil from an appropriate pump (not shown) to the steering cylinder 60, and the cylinder rod 62 moves in the left-right direction by hydraulic pressure. The movement of the cylinder rod 62 is transmitted to the oscillating part 52 via the tie rod 63, causing the oscillating part 52 to oscillate relative to the main body 51, thereby changing the steering angle of the front wheels 6.

[0054] The suspension device 70 shown in Figures 3 and 4 absorbs vibrations transmitted from the front axle case 50 (front wheel 6) to the vehicle frame 2. The suspension device 70 connects the front axle case 50 and the vehicle frame 2. The suspension device 70 comprises a rocking member 71 and a suspension cylinder 72.

[0055] The oscillating member 71 is fixed to the front axle case 50 and is pivotably connected to the vehicle frame 2. The oscillating member 71 is formed in an elongated shape in the front-rear direction. The upper surface of the front portion of the oscillating member 71 is fixed to the lower surface of the front axle case 50 (see Figure 4). The oscillating member 71 comprises an oscillating shaft 71a and a connecting portion 71b.

[0056] The pivot shaft 71a shown in Figure 3 is the axis that serves as the pivot center of the pivoting member 71. The pivot shaft 71a is positioned with its axis oriented in the left-right direction. The rear end of the pivoting member 71 is connected to the vehicle body frame 2 via the pivot shaft 71a.

[0057] The connecting portion 71b is the part to which the lower end of the suspension cylinder 72 is connected. The connecting portion 71b is connected to the suspension cylinder 72 via a predetermined connecting shaft whose axis is oriented in the left-right direction. A hole is formed in the connecting portion 23a through which the connecting shaft is inserted. As shown in Figure 4, the connecting portions 71b are provided on both the left and right sides of the front end of the oscillating member 71.

[0058] The suspension cylinder 72 absorbs vibrations through the flow resistance of oil supplied by an appropriate pump (not shown). The suspension cylinder 72 absorbs vibrations by expanding and contracting in the vertical direction. A pair of suspension cylinders 72 are arranged to connect the left and right sides of the vehicle frame 2 and the oscillating member 71.

[0059] Specifically, as shown in Figures 3 and 4, the upper end of the suspension cylinder 72 is rotatably connected to the connecting portion 23a of the side portion 23 of the vehicle frame 2 via a connecting shaft. The lower end of the suspension cylinder 72 is rotatably connected to the connecting portion 71b of the rocking member 71 via a connecting shaft. As shown in Figure 3, the suspension cylinder 72 is positioned in front of the first recess 26. The suspension cylinder 72 is also provided at the front end of the side portion 23 of the vehicle frame 2.

[0060] By providing the above-mentioned suspension device 70, the suspension cylinder 72 interposed between the front axle case 50 (oscillating member 71) and the vehicle frame 2 can absorb vibrations transmitted from the front axle case 50 (front wheel 6) to the vehicle frame 2.

[0061] The configuration of the tractor 1 according to this embodiment has been described above. In the tractor 1 described above, the steering angle of the front wheels 6 can be suitably changed by making the steering angle of the front wheels 6 relatively large relative to the extension and retraction amount of the steering cylinder 60.

[0062] In the following, the effects of the tractor 1 according to this embodiment will be explained using the front axle mechanism (front axle case 50 and steering cylinder 60) according to this embodiment shown in Figures 8 and 9, and the conventional front axle mechanism shown in Figure 10. In the following description of the conventional example, components similar to those in the front axle mechanism according to this embodiment will be described using the same reference numerals.

[0063] As shown in Figure 10(a), in a conventional front axle mechanism, the steering cylinder 60 is positioned at approximately the same height as the transmission shaft 41 of the front axle 40. As shown in Figure 10(b), in a conventional example, the steering cylinder 60 is positioned at the front of the front axle case 50A. The arm 52b of the front axle case 50A is formed to protrude forward from the vertical center of the pivoting part 52.

[0064] In the conventional example shown in Figure 10(b), the distance L2 between the connecting part (connecting shaft 63b) of the steering cylinder 60 to the pivot part 52 of the front axle case 50A and the pivot point (pivot shaft 52a) of the front wheel 6 is appropriately set to avoid interference between the steering cylinder 60 and the front axle case 50.

[0065] On the other hand, as shown in Figure 8, in the front axle mechanism according to this embodiment, the steering cylinder 60 is positioned above the transmission shaft 41 of the front axle 40. With the above configuration, as shown in Figure 9, the distance L1 between the connection part of the steering cylinder 60 to the oscillating part 52 (connecting shaft 63b of the tie rod end 63a) and the pivot point of the front wheel 6 (oscillating shaft 52a) can be made shorter than L2 shown in Figure 10(b), while avoiding interference with the front axle case 50. As a result, the steering angle of the front wheel 6 can be made relatively large with respect to the extension and retraction amount of the steering cylinder 60 (amount of movement of the cylinder rod 62 relative to the cylinder tube 61), and the steering angle of the front wheel 6 can be suitably changed.

[0066] Furthermore, in tractors with a generally narrow width (narrow tractors), it is relatively difficult to secure the amount of extension and retraction of the steering cylinder 60 necessary to ensure the steering angle of the front wheels 6. In other words, narrow tractors intended for use in vineyards, orchards, etc., require high turning performance (a relatively large amount of extension and retraction of the steering cylinder 60). The front axle mechanism according to this embodiment can secure a relatively large steering angle of the front wheels 6 with a relatively small amount of extension and retraction of the steering cylinder 60, and is therefore suitable for application to the narrow tractors described above.

[0067] Furthermore, in the tractor 1 according to this embodiment, a first recess 26 is provided in the body frame 2 (cast part 20) that can accommodate the steering cylinder 60. By positioning the steering cylinder 60 above the transmission shaft 41, the steering angle of the front wheels 6 can be secured while reducing the height of the body's bonnet 4. In other words, by providing the first recess 26 in the body frame 2, even if the suspension cylinder 72 is retracted from the state shown in Figure 3, for example, interference between the body frame 2 and the steering cylinder 60 can be avoided. With the above configuration, the vertical distance between the body frame 2 and the steering cylinder 60 can be made relatively small, and consequently, the height of the bonnet 4 located above the body frame 2 can be reduced.

[0068] In this embodiment, the suspension cylinder 72 connects the portion of the vehicle frame 2 in front of the first recess 26 to the oscillating member 71. This suppresses the reduction in rigidity of the vehicle frame 2 (cast portion 20) caused by the provision of the first recess 26. Furthermore, in this embodiment, the suspension cylinder 72 is connected to the front end portion (connecting portion 23a) of the vehicle frame 2. This improves the strength of the front portion (front part 24) of the vehicle frame 2.

[0069] Furthermore, in this embodiment, by positioning the steering cylinder 60 above the transmission shaft 41, the suspension cylinder 72 can be brought closer to the front axle case 50 in the longitudinal direction while avoiding interference with the steering cylinder 60 (see Figure 3). This makes the vehicle body more compact in the longitudinal direction.

[0070] Furthermore, in this embodiment, by providing a second recess 27 in the vehicle body frame 2 (cast part 20), interference between the front wheel 6 and the vehicle body frame 2 can be avoided. This ensures that the steering angle of the front wheel 6 is maintained.

[0071] In this embodiment, a guide portion 25b is provided on the vehicle frame 2 (cast portion 20). This allows for the efficient routing of linear members such as hoses supplying oil to the steering cylinder 60 and suspension cylinder 72, or harnesses and wires connected to predetermined equipment, by utilizing the guide portion 25b. Furthermore, with this configuration, the vehicle frame 2 (cast portion 20) on which the guide portion 25b is formed can be used as a guide for the linear members, thereby reducing the number of components. Moreover, in this embodiment, the guide portion 25b can be formed using the rib 25a that reinforces the first recess 26 of the vehicle frame 2.

[0072] Furthermore, in this embodiment, since most of the vehicle body frame 2 is formed by the cast portion 20, it is possible to easily form a vehicle body frame 2 with a complex shape that includes ribs 25a, guide portions 25b, first recess 26, second recess 27, etc.

[0073] As described above, the tractor 1 (work vehicle) according to this embodiment is A drive force transmission shaft 30 is positioned with its axis oriented in the front-rear direction and transmits the driving force of the engine 3, A transmission shaft 41 is positioned with its axis oriented in the left-right direction and transmits the driving force from the driving force transmission shaft 30 to the left and right front wheels 6, The front axle case 50 houses the transmission shaft 41, A steering cylinder 60 is provided in the front axle case 50 so as to be located above the transmission shaft 41 and capable of changing the steering angle of the front wheel 6, It is equipped with the following features.

[0074] This configuration allows for a favorable change in the steering angle of the front wheel 6. Specifically, by positioning the steering cylinder 60 above the transmission shaft 41, interference with the front axle case 50 can be avoided, while the distance L1 between the connecting portion of the steering cylinder 60 to the front axle case 50 (connecting shaft 63b) and the pivot point of the front wheel 6 (oscillating shaft 52a) can be made relatively short. This allows for a relatively large steering angle of the front wheel 6 relative to the extension and retraction amount of the steering cylinder 60.

[0075] Also, Tractor 1 is The vehicle body frame 2 supports the aforementioned front axle case 50 from above, The aforementioned vehicle body frame 2 includes: A first recess 26 is formed, which is recessed upwards and allows the steering cylinder 60 to be positioned inside.

[0076] This configuration allows for a reduction in the height of the vehicle's hood 4. Specifically, the provision of the first recess 26 prevents interference between the vehicle frame 2 and the steering cylinder 60. This allows for a relatively small vertical distance between the vehicle frame 2 and the steering cylinder 60, and consequently, a reduction in the height of the hood 4 provided on the vehicle frame 2.

[0077] Also, Tractor 1 is The vehicle is equipped with a suspension device 70 that absorbs vibrations transmitted from the front axle case 50 to the vehicle body frame 2. The suspension device 70 is The vehicle body frame 2 and the front axle case 50 are connected, and the vehicle also includes a suspension cylinder 72 positioned forward of the first recess 26.

[0078] By configuring it in this way, the reduction in rigidity of the vehicle frame 2 caused by the provision of the first recess 26 can be suppressed.

[0079] Furthermore, the suspension cylinder 72 is It is provided at the front end of the vehicle body frame 2.

[0080] By configuring it in this way, the strength of the front part (front section 24) of the vehicle frame 2 can be improved.

[0081] Also, Tractor 1 is The vehicle body frame 2 supports the aforementioned front axle case 50 from above, A second recess 27 is formed in the portion of the vehicle frame 2 that is rearward of the front axle case 50, so as to avoid interference with the front wheel 6, and which is recessed toward the left-right center of the vehicle frame 2.

[0082] By configuring it in this way, interference between the vehicle frame 2 and the front wheel 6 can be avoided, thereby ensuring the steering angle of the front wheel 6.

[0083] Also, Tractor 1 is The vehicle body frame 2 supports the aforementioned front axle case from above, The vehicle frame 2 has a cast iron portion 20 made of cast iron, The aforementioned cast iron portion 20 includes, A guide portion 25b capable of guiding a linear member is formed.

[0084] By configuring it in this way, a guide portion 25b capable of guiding a linear member can be formed using the cast iron portion 20 of the vehicle frame 2, which is easy to form into a complex shape.

[0085] Furthermore, the cast iron portion 20 includes, A rib 25a is provided that protrudes in a predetermined direction. The guide portion 25b is, It is formed in a groove-like shape, partitioned by the aforementioned rib 25a.

[0086] By configuring it in this way, the guide portion 25b can be formed using the rib 25a that reinforces the vehicle frame 2.

[0087] Furthermore, the tractor 1 according to this embodiment is one form of the work vehicle according to the present invention.

[0088] Although one embodiment of the present invention has been described above, the present invention is not limited to the above configuration, and various modifications are possible within the scope of the invention as described in the claims.

[0089] For example, the shapes of the components described in the above embodiment (vehicle frame 2, drive force transmission shaft 30, front axle 40, front axle case 50, steering cylinder 60, and suspension device 70, etc.) are merely examples and are not limited to the shapes described above. The shapes of the above components can be changed to any shape. Furthermore, the arrangement of the above components can also be changed as appropriate.

[0090] Furthermore, although the above embodiment shows an example in which a guide portion 25b (rib 25a), a first recess 26, and a second recess 27 are formed in the cast portion 20, the embodiment is not limited to this configuration. For example, a configuration in which some or all of the guide portion 25b, the first recess 26, and the second recess 27 are not formed is also possible.

[0091] Furthermore, although the above embodiment shows an example in which most of the vehicle body frame 2 is formed from the cast iron portion 20, the embodiment is not limited to this configuration. For example, it is also possible to form a part (for example, the second portion 28) or all of the cast iron portion 20 shown in this embodiment from sheet metal or the like.

[0092] Furthermore, although a tractor 1 was used as an example of a work vehicle in the above embodiment, the embodiment is not limited to this. For example, the work vehicle may be other agricultural vehicles, construction vehicles, industrial vehicles, etc. [Explanation of symbols]

[0093] 1 tractor 2. Vehicle frame 20 Casting Section 50 Front Axle Case 60 Steering Cylinder 70 Suspension System

Claims

1. A drive force transmission shaft is positioned with its axis oriented in the front-rear direction, and the engine's driving force is transmitted through it. A transmission shaft is positioned with its axis oriented in the left-right direction and transmits the driving force from the aforementioned driving force transmission shaft to the left and right front wheels, A front axle case housing the aforementioned transmission shaft, A steering cylinder is provided in the front axle case so as to be located above the transmission shaft and capable of changing the steering angle of the front wheel, A work vehicle equipped with [a certain feature].

2. The vehicle body frame provides support for the aforementioned front axle case from above. The aforementioned vehicle frame includes: A first recess is formed, which is recessed upwards and in which the steering cylinder can be positioned inside. The work vehicle according to claim 1.

3. The vehicle is equipped with a suspension device that absorbs vibrations transmitted from the front axle case to the vehicle body frame, The suspension device is The vehicle body frame and the front axle case are connected, and the suspension cylinder is positioned forward of the first recess. The work vehicle according to claim 2.

4. The suspension cylinder is The vehicle body frame is provided at the front end, The work vehicle according to claim 3.

5. The vehicle body frame provides support for the aforementioned front axle case from above. In the portion of the vehicle frame located behind the front axle case, a second recess is formed that is recessed toward the left-right center of the vehicle frame, in order to avoid interference with the front wheel. The work vehicle according to claim 1.

6. The vehicle body frame provides support for the aforementioned front axle case from above. The aforementioned vehicle frame has a cast part made of cast iron, The aforementioned cast iron part includes, A guide portion is formed that can guide a linear member. The work vehicle according to claim 1.

7. The aforementioned cast iron part includes, Ribs are provided that protrude in a predetermined direction. The aforementioned guide section is Formed in a groove-like shape partitioned by the aforementioned ribs, The work vehicle according to claim 6.

Images