JP6284274B2 - Work vehicle - Google Patents

Description

  The present invention relates to a work vehicle such as a tractor for agricultural work or a wheel loader for civil engineering work.

  2. Description of the Related Art Conventionally, a work vehicle such as an agricultural tractor includes a left and right brake pedal that can be depressed as an operation tool for braking both left and right rear wheels on a control seat on a traveling machine body (for example, Patent Document 1). Etc.). The work vehicle described in Patent Document 1 includes a brake valve that supplies hydraulic oil to a hydraulic cylinder (brake cylinder) for operating a brake mechanism incorporated in the left and right rear wheels in conjunction with a depression operation of a brake pedal. It has.

JP 2012-171380 A

  In the configuration of Patent Document 1, the piston inserted in the brake valve is interlocked with the depression operation of the brake pedal, thereby supplying the working oil to the brake cylinder and operating the brake mechanism. In such a configuration, the working oil discharge amount from the brake valve is determined according to the movement amount of the piston and the piston cross section. Therefore, if the piston cross section is enlarged in order to improve the response to the brake mechanism, the pedaling force on the brake pedal becomes heavy. On the other hand, if the piston cross section is made small in order to reduce the pedaling force on the brake pedal, the stroke length of the piston becomes long, and the response to the brake mechanism becomes poor.

  Further, as in the configuration of Patent Document 1, a pair of left and right pistons are inserted in the brake valve so as to operate the brake mechanisms of both the left and right rear wheels. Therefore, when the left and right brake pedals are connected and stepped on simultaneously, the left and right pistons are pushed in, and the left and right rear wheel brake mechanisms can be operated simultaneously. However, when the pedaling force applied to the left and right brake pedals varies, the pushing amount of the left and right pistons is different, and there is a possibility that a difference occurs in the amount of operation in the brake mechanism of the left and right rear wheels.

  This invention makes it a technical subject to provide the working vehicle which examined and improved the above present condition.

The present invention provides a work vehicle including a brake valve for braking a wheel of a traveling machine body and a brake pedal for reciprocating a brake piston in the brake valve. The brake piston is divided into a first piston and a second piston. The cross-sectional area of the first piston is set to be larger than the cross-sectional area of the second piston, and the second piston moves after the first piston is moved first by depressing the brake pedal. The brake valve includes a reservoir tank communicating with the input side of the first piston, and a pilot valve is interposed between the output side of the first piston and the reservoir tank, The pilot valve operates when the pressure on the output side of the second piston becomes higher than a predetermined pressure, The output side of the serial first piston is that communicates with the reservoir tank.

  In the work vehicle, a check valve is interposed between the first piston and the second piston, and a pressure at a connection portion between the first piston and the second piston is higher than a pressure of the second piston. In this case, the check valve may be operated so that the output side of the first piston communicates with the output side of the second piston.

  The work vehicle includes left and right brake pedals that reciprocate a pair of brake pistons in the brake valve, and the brake valve is provided with an equalizer piston that communicates with both brake pistons. By applying the brake pressure at the brake piston corresponding to each end part, even if there is a difference in the left and right pedaling force when the left and right brake pedals are depressed simultaneously, By moving the equalizer piston according to the difference in brake pressure, the difference in brake pressure between the left and right brake pistons can be absorbed, and the brake pressure can be made equal to the left and right (the braking force of the left and right wheels can be made equivalent). .

  The work vehicle includes a cabin frame that forms a framework of a cabin that covers a control seat on a traveling machine body, the cabin frame including a board support plate that supports a dashboard positioned in front of the control seat, and the brake valve And the brake pedal are attached to the board support plate, the dashboard can be supported by the board support plate with high strength while improving the rigidity of the entire cabin frame. The brake pedal and the brake valve, which are movable members, can be supported with high strength and compactness on the board support plate which is a strength member of the cabin frame.

  According to the present invention, since the brake piston is separated, the brake pressure is applied with a short stroke by the first piston when the brake pedal is initially depressed, and then a large brake pressure is applied with a light pedal force by the second piston. It is possible to apply the brake with a light pedal force without making the stroke too long. Brake pedal operability and braking performance can be improved.

  According to the present invention, by providing a check valve, the check valve is operated to connect the first piston and the second piston, and the pressure (brake pressure) on the first piston side is released to the second piston side. The working oil having a flow rate based on the displacement of the first piston can be discharged. The state in which the first piston is connected to the second piston can be maintained, and the pressing force from the first piston can be transmitted to the second piston. Therefore, in the initial depression of the brake pedal, the first piston can apply the brake pressure with a short stroke, which contributes to the improvement of the operability of the brake pedal.

  According to the present invention, by providing the pilot valve, when the brake pressure on the first piston side reaches a predetermined pressure by the depression operation of the brake pedal, the pilot valve is operated to release the brake pressure on the first piston side, and the second The brake pressure can be maintained with just the piston. Switching from the first piston to the second piston can be performed smoothly, which contributes to improvement of the brake pedal operability.

It is a left view of a tractor. It is a top view of a tractor. It is a right view of a tractor. It is the perspective view which looked at the tractor from diagonally right back. It is left side explanatory drawing of a traveling body. It is left side explanatory drawing which shows the detailed structure of a traveling body. It is the perspective view which looked at the traveling body from diagonally left rear. It is right side explanatory drawing of a traveling body. It is right side explanatory drawing which shows the detailed structure of a traveling body. It is the perspective view which looked at the traveling machine body from diagonally right rear. It is the perspective view which looked at the cabin frame from diagonally left front. It is the perspective view which looked at the cabin frame from diagonally left rear. It is a front perspective view of an air cut plate. It is a perspective view of an engine and a cabin viewed from the right front side. It is right side sectional drawing which shows the relationship between an air cut plate, a brake pedal, and a brake valve. It is the figure which looked ahead from the control seat. It is a perspective view which shows the structure inside a dashboard. It is a perspective view which shows the relationship between a brake pedal and a brake valve. It is side surface sectional drawing which shows the structure of a brake valve. It is a partial sectional view by plane view showing the composition of a brake valve. It is a partial cross section figure by the front view which shows the structure of a brake valve. It is a hydraulic circuit diagram which shows the structure of a brake valve. It is an expanded sectional view by the side view which shows the structure of a brake valve. It is an expanded sectional view by the side view which shows the structure of a brake valve.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, taking a tractor as a work vehicle as an example.

  First, an outline of the tractor 1 will be described with reference to FIGS. The traveling machine body 2 of the tractor 1 in the embodiment is supported by a pair of left and right rear wheels 4 as well as a pair of left and right front wheels 3 as a traveling unit. The tractor 1 is configured to travel forward and backward by driving the rear wheels 4 and the front wheels 3 with a common rail type diesel engine 5 (hereinafter simply referred to as an engine) as a power source mounted on the front portion of the traveling machine body 2. Has been. The engine 5 is covered with a bonnet 6. A cabin 7 is installed on the upper surface of the traveling machine body 2. Inside the cabin 7, a steering seat 8 and a steering handle (round handle) that moves the steering direction of the front wheel 3 to the left and right by steering. 9 are arranged. Steps 10 on which the operator gets on and off are provided at the left and right lower portions of the cabin 7. A fuel tank 11 that supplies fuel to the engine 5 is provided below the bottom of the cabin 7.

  The traveling machine body 2 includes an engine frame 14 having a front bumper 12 and a front axle case 13, and left and right machine body frames 15 detachably fixed to a rear portion of the engine frame 14. A front axle 16 is rotatably protruded outward from the left and right ends of the front axle case 13. The front wheels 3 are attached to the left and right ends of the front axle case 13 via the front axle 16. A transmission case 17 is connected to the rear part of the body frame 15 for appropriately changing the rotational power from the engine 5 and transmitting it to the front and rear four wheels 3, 3, 4, 4. A tank frame 18 having a rectangular frame plate shape in a bottom view projecting outward in the left and right directions is bolted to the lower surface sides of the left and right body frames 15 and the mission case 17. The fuel tank 11 of the embodiment is divided into left and right. The left and right fuel tanks 11 are distributed and mounted on the upper surface side of the left and right projecting portions of the tank frame 18. The left and right rear axle cases 19 are mounted on the left and right outer surfaces of the mission case 17 so as to protrude outward. Left and right rear axle cases 20 are rotatably inserted in the left and right rear axle cases 19. The rear wheel 4 is attached to the mission case 17 via the rear axle 20. Upper portions of the left and right rear wheels 4 are covered with left and right rear fenders 21.

  A hydraulic lifting mechanism 22 that lifts and lowers a working machine such as a rotary tiller is detachably attached to the rear upper surface of the mission case 17. A work machine such as a rotary tiller is connected to the rear portion of the transmission case 17 via a three-point link mechanism including a pair of left and right lower links 23 and a top link 24. On the rear side surface of the mission case 17, a PTO shaft 25 for transmitting a PTO driving force to a working machine such as a rotary tiller is provided to project rearward.

  A flywheel 26 is attached to an engine output shaft (not shown) projecting rearward from the rear side surface of the engine 5. A main shaft 27 projecting rearward from the flywheel 26 and a main transmission input shaft 28 projecting forward from the front side of the transmission case 17 are connected via a power transmission shaft 29 having universal shaft joints at both ends. FIG. 1, FIG. 7 and FIG. 10). In the transmission case 17, a hydraulic continuously variable transmission, a forward / reverse switching mechanism, a traveling auxiliary transmission gear mechanism, and a differential gear mechanism for rear wheels are arranged. The rotational power of the engine 5 is transmitted to the main transmission input shaft 28 of the transmission case 17 via the main driving shaft 27 and the power transmission shaft 29, and is appropriately shifted by the hydraulic continuously variable transmission and the traveling auxiliary transmission gear mechanism. Then, the transmission power is transmitted to the left and right rear wheels 4 through the rear wheel differential gear mechanism.

  The front wheel output shaft 30 projecting forward from the lower front portion of the transmission case 17 projects rearward from the front axle case 13 containing a front wheel differential gear mechanism (not shown) via a front wheel drive shaft 31. A front wheel transmission shaft (not shown) is connected. Transmission power by the hydraulic continuously variable transmission and the traveling auxiliary transmission gear mechanism in the transmission case 17 is transmitted from the front wheel output shaft 30, the front wheel drive shaft 31, and the front wheel transmission shaft to the front wheel differential gear mechanism in the front axle case 13. Is transmitted to the left and right front wheels 3 via.

  Next, the internal structure of the cabin 7 will be described with reference to FIGS. A steering column 32 is disposed in front of the control seat 8 in the cabin 7. The steering column 32 is erected in a state of being embedded in the back side of the dashboard 33 disposed on the front side inside the cabin 7. A steering handle 9 having a substantially round shape in plan view is attached to the upper end side of the handle shaft that protrudes upward from the upper surface of the steering column 32.

  On the right side of the steering column 32, there is a one-touch lift lever 34 for forcibly moving a working machine such as a rotary tiller to the highest position or the lowest position, and a pair of left and right brake pedals 35 for braking the traveling machine body 2. And are arranged. On the left side of the steering column 32, a forward / reverse switching lever 36 (reverser lever) for switching the traveling direction of the traveling machine body 2 between forward and reverse and a power transmission clutch (not shown) are disconnected. A clutch pedal 37 is provided.

  An erroneous operation preventing body 38 (reverser guard) extending along the forward / reverse switching lever 36 is disposed on the left side of the steering column 32 and below the forward / reverse switching lever 36. By disposing an erroneous operation prevention body 38 as a contact preventer below the forward / reverse switching lever 36, the operator is prevented from inadvertently contacting the forward / reverse switching lever 36 when getting on and off the tractor 1. An operation display panel 39 incorporating a liquid crystal panel is provided on the upper rear side of the dashboard 33.

  An accelerator pedal 41 that controls the rotational speed or the vehicle speed of the engine 5 is disposed on the right side of the steering column 32 in the floor plate 40 in front of the control seat 8 in the cabin 7. Note that substantially the entire top surface of the floor plate 40 is formed as a flat surface. Side columns 42 are arranged on both the left and right sides of the control seat 8. Between the control seat 8 and the left side column 42, the parking brake lever 43 for executing the operation of maintaining the left and right rear wheels 4 in a braking state and the traveling speed (vehicle speed) of the tractor 1 are forcibly greatly increased. An ultra-low speed lever 44 (creep lever) to be reduced, a sub-shift lever 45 for switching the output range of the traveling sub-transmission gear mechanism in the transmission case 17, and a PTO shift for switching the driving speed of the PTO shaft 25 A lever 46 is arranged. A differential lock pedal 47 for turning on / off the differential drive of the left and right rear wheels 4 is disposed below the control seat 8. A reverse PTO lever 48 that performs an operation of driving the PTO shaft 25 in the reverse direction is disposed on the left rear side of the control seat 8.

  Between the control seat 8 and the left side column 42, an armrest 49 for placing the arm and elbow of the operator seated on the control seat 8 is provided. The armrest 49 is configured separately from the control seat 8 and has a main transmission lever 50 that increases and decreases the traveling speed of the tractor 1 and a dial type that manually changes and adjusts the height position of a work machine such as a rotary tiller. A working part position dial 51 (elevating dial) is provided. In addition, the armrest 49 is configured to be able to be turned up and rotated in a plurality of stages with the rear end lower part as a fulcrum.

  The left side column 42 includes, in order from the front side, a throttle lever 52 that sets and maintains the rotational speed of the engine 5, and a PTO clutch switch 53 that performs intermittent operation of power transmission from the PTO shaft 25 to a working machine such as a rotary tiller. A plurality of hydraulic operation levers 54 (SCV levers) for switching and operating a hydraulic external take-out valve arranged on the upper surface side of the mission case 17 are arranged. Here, the hydraulic external take-off valve is for supplying and controlling hydraulic oil to another work machine such as a front loader retrofitted to the tractor 1. In the embodiment, four hydraulic operation levers 54 are arranged in accordance with the number of hydraulic external take-out valves (four stations).

  Next, the detailed structure of the cabin 7 will be described with reference to FIGS. 1 to 6 and FIGS. 11 to 14. The cabin 7 that covers the control seat 8 on the traveling machine body 2 includes a cabin frame 300 that forms a framework. The cabin frame 300 includes a pair of left and right front columns 301 positioned in front of the control seat 8, a pair of left and right rear columns 302 positioned behind the control seat 8, and a front beam that connects between the upper ends of the front columns 301. A member 303, a rear beam member 304 for connecting the upper ends of the rear columns 302, and a left and right side beam member 305 for connecting the upper ends of the front columns 301 and the rear columns 302 arranged in the front-rear direction. It is a box frame. A roof body 306 is detachably attached to the upper end side of the cabin frame 301, that is, on a rectangular frame constituted by the front beam member 303, the rear beam member 304, and the left and right side beam members 305.

  The left and right outer end sides of the front lower plate 307 extending inward and leftward and rightward are connected to the lower end side of each front support column 301. A vertically long board support plate 308 that fixes and supports the dashboard 33 is connected to the left and right inner ends of the left and right front lower plate plates 307, and the board support plate 308 is erected between the left and right front columns 301. On the other hand, a rear intermediate beam member 309 extending in parallel with the rear beam member 304 is connected between the lower ends of the left and right rear columns 302. The rear intermediate beam member 309 is connected to the upper ends of a pair of left and right rear lower frames 310 extending downward. End portions in the longitudinal direction of the bottom frame 311 extending in the front-rear direction are connected to the front lower plate 307 and the lower end side of the rear lower frame 301 arranged in the front-rear direction.

  A rear end upper side of the fender frame 312 that is curved so as to swell forward and upward in a side view along the shape of the rear fender 21 is connected to the lower end side of each rear post 302. The front end lower side of each fender frame 312 is connected to the rear end side of the side frame 313 protruding rearward from the lower portion of the corresponding front support 301. The left and right outer end sides of the front lower plate plate 307 are also connected to each side frame 313. The left and right rear fenders 21 are attached to the left and right outer surfaces of each fender frame 312 and the corresponding left and right outer surfaces of the rear lower frame 310.

  A rear cover plate 314 that covers a region surrounded by the rear intermediate beam member 309 and the left and right rear lower frames 310 is attached to the rear intermediate beam member 309 and the left and right rear lower frames 310. A seat support plate 315 that is L-shaped in a side view is attached to the lower end side of the rear cover plate 314 and the left and right bottom frames 311. The control seat 8 is disposed on the seat support plate 315. The left and right fender frames 312, the rear lower frame 310, and the bottom frame 311 are attached with bulged fender inner plates 316 along the front inner surface side of the rear wheel 4. Side columns 42 are disposed on the left and right fender inner plates 316. A floor plate support plate 317 is attached and supported on the left and right front lower plate plates 307, the front side of the bottom frame 311, the side frames 313, and the front end sides of the seat support plates 315. The floor board 40 is disposed on the left and right floor board support plates 317. The front end lower sides of the left and right fender frames 312 and the front and rear middle portions of the bottom frame 311 corresponding thereto are connected by left and right horizontally long auxiliary frames 318.

  A windshield 321 is disposed on the front side of the cabin frame 300, that is, in a region surrounded by the left and right front columns 301, the front beam members 303, and the left and right front lower plate plates 307. A rear glass 322 is disposed on the rear surface side of the cabin frame 300, that is, in a region surrounded by the left and right rear columns 302, the rear beam member 304, and the rear intermediate beam member 309. Side doors 323 made of transparent glass are disposed in the left and right side surfaces of the cabin frame 300, that is, in the region surrounded by the front and rear columns 301 and 302, the side beam members 305, the fender frame 312 and the side frames 313. doing. Each side door 323 is attached to the corresponding rear column 302 via a pair of upper and lower hinges 324 so as to be opened and closed.

  As is apparent from the arrangement structure of the windshield 321, the rear glass 322, and the left and right side doors 323, the columns 301 and 302 and the beam members 303, 304, and 305 are located on the side sides of the cabin 7 (cabin frame 300). ing. For this reason, it is possible to widen the windows on the front, rear, left and right sides of the cabin frame 300. In the embodiment, a windshield 321, a rear glass 322, and left and right side doors 323 (made of transparent glass) are disposed on the front, rear, left and right side surfaces of the cabin frame 300. As a result, both the front / rear and left / right visibility of the operator and the rigidity of the cabin frame 300 are ensured.

  As shown in FIG. 11 and FIG. 12 and the like, the front portions of the left and right front lower plate plates 307 have front support attached to the left and right body frames 15 via front vibration isolation rubber bodies 98 as vibration isolation members. It is connected to a table 96. Further, a base bracket 327 projecting outward in the left and right directions is provided at a connecting portion (butting portion) between the left and right rear lower frames 310 and the bottom frame 311. The left and right base brackets 327 are connected to a rear support 97 attached to the left and right rear axle cases 19 via a rear vibration isolation rubber body 99 as a vibration isolation member. Accordingly, the traveling machine body 2 supports the cabin 7 in a vibration-proof manner via the plurality of vibration-proof rubber bodies 98 and 99.

  Next, the structure of the air cut plate 308 and its periphery will be described with reference to FIGS. A vertically long air cut plate 308 that fixes and supports the dashboard 33 is connected to the left and right inner ends of the front lower plate plate 307 connected to the lower end side of each front support post 301, and the air cut plate is interposed between the left and right front support posts 301. 308 is erected. As can be seen from the connection relationship between the left and right front columns 301 and the front lower plate plate 307, the air cut plate 308 is one of the components of the cabin frame 300 and constitutes a strength member of the cabin frame 300. On the other hand, a windshield 321 is disposed on the front side of the cabin frame 300, that is, in an area surrounded by the left and right front columns 301, the front beam members 303, and the left and right front lower plate plates 307. The air cut plate 308 is located closer to the cabin 7 than the windshield 321. The windshield 321 covers the front side of the board support plate 308. The windshield 321 is disposed on the front side of the cabin 7 without forming a notch.

  Not only the steering column 32 and the dashboard 33 are attached to the air cut plate 308, but also a brake valve 254 for braking the wheel 4 of the traveling machine body 2 and a brake pedal 35 for operating the brake valve 254 are attached. ing. The brake valve 254 and the brake pedal 35 are supported on the air cut plate 308. In this case, through holes 253 and 442 penetrating in the front-rear direction are formed in both the air cut plate 308 and the windshield 321. A brake valve 254 is inserted into and fixed to the through holes 253 and 442. The front end side of the brake valve 254 protrudes forward of the cabin 7 from both through holes 253 and 442. A front wiper 421 for cleaning the windshield 321 is provided near the center of the windshield 321. The drive shaft 422 a of the front wiper 421 passes through the windshield 321 and is pivotally supported on the upper portion of the air cut plate 308.

  The cabin frame 300 includes an air cut plate 308 that supports the dashboard 33 positioned in front of the control seat 8, and the air cut plate 308 is positioned inside the cabin 7 relative to the windshield 321, and the air cut plate 308 is attached to the cabin frame. It consists of 300 strength members. Therefore, the dashboard 33 can be supported by the air cut plate 308 with high strength while improving the rigidity of the cabin frame 300 as a whole. The windshield 321 can be attached to the front side of the cabin 7 without forming a notch, the processing cost of the windshield 321 and the cost for securing the sealing performance can be reduced, and the windproof and waterproof structure of the cabin 7 can be provided. Easy to configure.

  Moreover, since the brake valve 254 for braking the wheel 4 of the traveling machine body 2 and the brake pedal 35 for operating the brake valve 254 are attached to the air cut plate 308, the brake pedal 35 and the brake valve 254, which are movable members, are connected. The air cut plate 308 which is a strength member of the cabin frame 300 can be supported with high strength. Further, through holes 253 and 442 penetrating front and rear are formed in the windshield 321 and the air cut plate 308, the brake valve 254 is inserted and fixed in the through holes 253 and 442, and the front end side of the brake valve 254 is connected to the through hole 253 The front side of the cabin 7 protrudes from 442. Thus, the windproof and waterproof structure of the cabin 7 can be easily configured, but the brake pedal 35 is arranged in the cabin 7 and the brake valve 254 to the braking mechanism for braking the wheels 4 are simply connected. it can.

  As shown in FIGS. 14 to 18, the pair of left and right brake pedals 35 is provided with a pushing member 352 that is in contact with the input side piston (first piston) 501 of the brake valve 254 in the middle of the brake arm 351. Yes. The switch stay 353 is disposed so as to cover the rear surfaces of the brake arms 351 of the left and right brake pedals 35. The switch stay 353 fixes a pair of left and right brake stoppers 354 and a pair of left and right brake pedal switches 355 at positions where the switch stay 353 contacts the rear surface of the brake arm 351 of the left and right brake pedal 35. The brake stopper 354 abuts on the brake arm 351 in a state where the brake pedal 35 is not depressed, and regulates the position of the brake pedal 35. The brake pedal switch 355 contacts the brake arm 351 in a state where the brake pedal 17 is not depressed and is turned on.

  A brake stopper 354 and a brake pedal switch 355 are integrally fixed by a switch stay 353 at a position on the rear side of the brake arm 351 with respect to the left and right brake pedals 35, and a pushing member 352 is attached to the brake arm 351. Yes. And the brake pedal switch 355 is arrange | positioned so that the brake pedal switch 355 will be in an ON state in the state which controlled the position of the brake pedal 35 with the brake stopper 354. Therefore, when the brake pedal 35 is assembled, the position of the push-in member 28 is simply adjusted so that the push-in member 351 and the input-side piston 501 of the brake valve 254 come into contact with each other without any depression when the brake pedal 35 is not depressed. Good. Therefore, the assembly work of the brake mechanism can be simplified to reduce the number of assembly steps, and at the same time, the position adjustment of each component can be executed accurately.

  One end of a connection plate 356 is pivotally attached to one brake arm 351 of the left and right brake pedal 35, and a locking plate 357 that engages with the other end of the connection plate 356 is provided on the other brake arm 351. By locking the other end of the connecting plate 356 to the locking plate 357, the left and right brake pedals 35 are connected to enable simultaneous operation of the left and right brake pedals 35. On the other hand, by removing the other end of the connecting plate 356 from the locking plate 357, the left and right brake pedals 35 can be operated independently. The locking plate 357 is provided with a connection confirmation sensor 358 that detects that the connection plate 356 is connected to the lock plate 357. The connection confirmation sensor 358 includes, for example, a proximity switch that optically detects the other end of the connection plate 356, and is turned on when the connection plate 356 is engaged with the locking plate 357. The connection plate 356, the locking plate 357, and the connection confirmation sensor 358 are configured as a connection tool for the left and right brake pedals 35.

  As shown in FIGS. 14 to 17 and the like, the front side of the dashboard 33 is covered with an air cut plate (board support plate) 308 for shielding heat from the engine 5 and the like under the bonnet 6. Further, the front window glass 321 is composed of a single glass plate, and the air cut plate 308 is connected to the back surface of the front window glass 321. The dashboard 33 includes a wiper drive mechanism 422 so as to cover the rear of the windshield 321. The wiper drive mechanism 422 includes a drive motor that generates rotational power to the wiper 421 that is pivotally supported by the windshield 321 and a gear mechanism that transmits the rotational power of the drive motor to the wiper 421. As the drive motor in the wiper drive mechanism 422 rotates, the rotation of the drive motor is transmitted to the wiper 421 via the gear mechanism, and the wiper 421 rotates along the surface of the windshield 321.

  The wiper drive mechanism 422 is connected and fixed to the air cut plate 308. That is, the wiper drive mechanism 422 is fixed to the rear surface of the air cut plate 308, and the front window glass 321 is stretched on the front side of the air cut plate 308. Then, the drive shaft 422 a of the wiper drive mechanism 422 is passed through the windshield 321. The wiper 421 is rotated by the wiper drive mechanism 422 when the drive shaft 422 a of the wiper drive mechanism 422 pivotally supports the wiper 421.

  A meter control device (meter ECU) 904 and an antenna 905 are fixed to the rear surface of the air cut plate 308 together with the wiper drive mechanism 422. By attaching the wiper drive mechanism 422, the meter ECU 904, and the antenna 905 to the air cut plate 308, the air cut plate 308 can be configured as a single unit, so that the assembling operation of each component inside the dashboard 33 can be simplified.

  The meter panel 906 is disposed in a state where the panel surface is inclined slightly upward from the rear so as to face the operator seated on the control seat 8 at a position on the lower front side of the control handle 9. The dashboard 33 is provided with a plurality of switch members 907 such as a parking switch and a wiper switch at a position on the outer periphery of the meter panel 906. The key switch 61 is a rotary switch that can be rotated with a predetermined key inserted into the keyhole, and is attached to the right side of the steering handle 9 on the dashboard 33.

  The steering column 32 is erected in a state of being embedded in the back side of the dashboard 33, and supports a vertically long handle shaft. A steering handle 9 having a substantially round shape in plan view is provided on the upper end side of the handle shaft. It is attached. A tilt lever 915 and a telescopic lever 914 for adjusting the attitude of the steering handle 9 are arranged separately on the left and right of the steering column 32 where the steering handle 9 is arranged. That is, a telescopic lever 914 that is pivotally supported in the lateral direction and pivoted in the front-rear direction is provided on the right side surface of the steering column 32. A tilt lever 915 is provided below the left side surface of the steering column 32 and is pivotally supported in the horizontal direction and rotated in the front-rear direction.

  A brake pedal support mechanism 916 including a brake pedal shaft 720 that pivotally supports the left and right brake pedals 35 is disposed in front of the steering column 32. The brake pedal support mechanism 916 is connected and supported in the middle of the air cut plate 308. The steering column 32 has a forward / reverse switching lever 36 projecting from the left side thereof, and an erroneous operation preventing body 38 (reverser guard) is disposed below the forward / backward switching lever 36. Further, the steering column 32 is provided with operation levers 62 and 63 such as a wiper lever for driving the wiper 421 and an auto cruise lever for driving the work vehicle at a constant speed on the right side surface thereof.

  A DPF regeneration switch 62 for executing regeneration control of the exhaust gas purifying device 224 is provided on the upper surface of the steering column 32 at the base of the steering handle 9. That is, the DPF regeneration switch 62 is disposed in the operator's field of view when in a straight-ahead working posture. Therefore, the position and lighting display state of the DPF regeneration switch 64 can be easily visually recognized by a seated operator without the DPF regeneration switch 62 being hidden by the steering handle 9 or the operation levers 36, 62, and 63.

  On the upper surface of the steering column 32, a plurality of switches 65 such as a work switch and a one-touch automatic switch are arranged at positions that are symmetrical with respect to the handle axis of the steering handle 9. Therefore, the operator who sits down can easily confirm the positions of the switch for work and the one-touch automatic switch by visually recognizing the switch group 65 arranged on the upper surface of the steering column 32, so that erroneous operations can be reduced.

  Next, the structure of the brake valve 254 and its periphery will be described with reference to FIGS. When the brake pedal 35 is depressed, the pushing member 351 attached to the brake pedal 35 pushes the input side piston 501 of the brake valve 254 into the brake valve 254. When the input-side piston 501 is pushed into the brake valve 254, hydraulic oil is pumped from the brake valve 254 to the pair of left and right brake cylinders 255 that brake the pair of left and right rear wheels 4, respectively. Operate.

  The brake valve 254 has a pair of left and right input pistons 501 inserted in the valve case 502. The valve case 502 is configured by connecting a front case 503 having a fixing flange 505 on the outer periphery of a plane and a rear case 504 having a rear end of the input-side piston 501 protruding from the back and forth. The front case 503 constitutes a reservoir tank (storage tank) 507 for storing working oil by covering an upper space with an upper lid 506. The front case 503 has a pair of left and right front cylinders 508 penetrating front and rear under the reservoir tank 507, and a front sealing plug 509 is screwed into a front opening of the front cylinder 508.

  The front case 503 has a check valve 510 having a T-shaped valve body 511 on the front cylinder 508 side fitted in two through holes communicating with the bottom of the reservoir tank 507 and the left and right front cylinders 508. Yes. In the present embodiment, the check valve 510 is constituted by the plug 512 having a lower opening diameter larger than the upper opening diameter and having a through hole 513 provided with a step, and the valve body 511 is plugged. The plug 512 is screwed to the bottom of the reservoir tank 507 while being inserted into the through hole 513 of 512 from below. The valve body 511 is biased toward the reservoir tank 507 by a spring whose one end is locked to the lower end of the plug 512, and the valve body 511 contacts the step of the through hole 513, whereby the reservoir tank 507 and the front cylinder 508 are urged. Block communication with.

  The front case 503 is provided with a through hole in the lower front side of each of the left and right front cylinders 508 to form an oil passage 514, and is connected to each of the left and right brake cylinders 255 at the lower end of each of the left and right oil passages 514. A connection port 515 that connects to the hydraulic pipe 256 is provided. The front case 503 is provided with a piston cylinder (equalizer piston cylinder) 516 for communicating the left and right front cylinders 508 at a position below the left and right front cylinders 508 and facing the check valve 510.

  The piston cylinder 516 is configured by screwing a pair of left and right sealing plugs 517 into openings at both left and right ends of a through hole that penetrates the front case 503 from side to side. In addition, a pair of left and right oil passages 518 communicating with the left and right front cylinders 508 are provided above the piston cylinder 516. The piston cylinder 516 includes an equalizer piston 519 that slides left and right in the piston cylinder 516 and a pair of left and right springs 520 that are arranged on the left and right sides of the piston main body 520, and the equalizer piston 519 is displaced to displace the left and right front cylinders. Adjust the pressure at 508.

  One end of the spring 520 is locked to the sealing plug 517 and the equalizer piston 519 is pressed at the other end. The piston cylinder 516 is provided with a left adjustment oil chamber 521 in a space closed by the left side of the equalizer piston 519 and the left side sealing plug 517, and in a space closed by the right side and the right side sealing plug 517 of the equalizer piston 519. A regulating oil chamber 522 is provided. That is, the equalizer piston 519 slides left and right in the piston cylinder 516, thereby changing the volumes of the left and right adjustment oil chambers 521 and 522, thereby adjusting the pressure in the left and right front cylinders 508.

  Cylindrical output side pistons (second pistons) 523 are inserted into the left and right front cylinders 508 in the front case 503 from the back side (fixing flange 505 side). The output side piston 523 has a cylindrical shape provided with a through hole 524 that constitutes an oil passage in the piston. The through hole 524 is configured such that the inner diameters at both front and rear ends are larger than the inner diameter of the midway part. Further, the outer wall of the output side piston 523 is provided with a notch 525 in which the entire outer peripheral surface of the front end side midway is notched.

  The rear end of the spring 526 in which the front end is inserted into the front sealing plug 509 is inserted into the front end of the through hole 524 of the output side piston 523, and the rear end of the spring 526 is brought into contact with the front step of the through hole 524. ing. Thereby, the output side piston 523 is urged toward the rear of the front cylinder 508 by the spring 526 locked to the plug 509 at the front end of the front cylinder 508. A check valve 527 with the rear end in contact with the front end of the input side piston 501 is fitted to the rear end of the output side piston 523.

  The check valve 527 is provided with a through hole 529 having a step in a plug 528 screwed to the rear end of the output side piston 523. A spherical valve body 530 is housed in front of the step portion of the through hole 529, and a valve input side oil chamber 531 into which the front end central portion of the input side piston 501 is inserted is provided on the rear side of the step portion of the through hole 520. ing. The valve body 530 is urged toward the input side piston 501 by a spring whose one end is locked to the front end of the plug 528, and the valve body 530 comes into contact with the step of the through hole 529, so that the valve input side oil chamber 531. And communication with the through hole (piston oil passage) 524 of the output side piston 523 is blocked. A plurality of communication holes 532 communicating with the valve input side oil chamber 531 are provided on the rear side wall of the plug 528.

  The front case 503 is provided with an oil passage 533 serving as a control port to a pilot valve 537, which will be described later, at a position below each of the left and right front cylinders 508 and behind the piston cylinder 516. The oil passage 533 is configured by connecting a vertical hole 534 drilled below the front cylinder 508 and a horizontal hole 535 drilled forward from the back of the front case 505 (the surface on the fixing flange 505 side).

  The rear case 504 includes a pair of left and right rear cylinders 536 penetrating in the front-rear direction. The pair of left and right front cylinders 508 provided in the front case 503 communicate with the front end of the rear cylinder 536, while the input side piston The rear end of 501 protrudes from the rear end of the rear cylinder 536. An output side piston 523 protruding from the front cylinder 508 of the front case 503 and a check valve 527 are inserted at the front end of the rear cylinder 536, and the front end surface of the input side cylinder 501 is in contact with the rear end surface of the check valve 527. I am letting.

  The rear case 504 includes a pair of left and right pilot valves 537 provided with shaft-shaped valve bodies 538 below the pair of left and right rear cylinders 536. The valve body 538 of the pilot valve 537 includes a hollow portion 539 drilled along the axial direction from the rear end surface, and a communication hole 540 that communicates with the hollow portion 539 is provided on the outer peripheral wall of the front end portion of the valve body 538. Yes. The rear case 504 has a pair of left and right valve cylinders 541 that slide the valve body 538 of the pilot valve 537 in the front-rear direction below each of the pair of left and right rear cylinders 536.

  The valve cylinder 541 is formed from the front end surface of the rear case 504, and the front end opening thereof is communicated with the rear end opening of the horizontal hole 535 of the oil passage (control port) 533 in the front case 503. The rear case 504 is provided with a cylinder rear oil passage 542 drilled rearward at the rear ends of the pair of left and right valve cylinders 541. The valve cylinder 541 communicates with a front portion (intermediate oil chamber 551) of the rear cylinder 536 via a vertical oil passage 543 serving as an input port, and the cylinder rear oil passage 542 serves as a vertical oil passage serving as an output port. It communicates with the rear portion (rear oil chamber 552) of the rear cylinder 536 via the oil passage 544 in the direction.

  In the hollow portion 539 of the valve body 538, a front end of a spring 545 in which a rear end side is inserted into the cylinder rear oil passage 542 is inserted. A step is provided in each of the hollow portion 539 of the valve body 538 and the cylinder rear oil passage 542, and the front end of the spring 545 is brought into contact with the step of the hollow portion 539, while the step of the spring 545 is arranged on the step of the cylinder rear oil passage 542. The ends are in contact. Therefore, the valve body 538 is urged forward (front case 502 side) by the spring 545 locked to the step of the cylinder rear oil passage 542, and when the hydraulic pressure of the control port 533 is low, the front end of the valve body 538 is Comes into contact with the rear end surface of the front case 502. Further, when the hydraulic pressure of the control port 533 increases and the pressing force by the hydraulic pressure from the control port 533 exceeds the urging force of the spring 545, the valve body 538 slides backward. The valve body 538 is restricted from moving backward by the rear end portion of the valve cylinder 541.

  The rear portions (rear oil chambers 552) of the left and right rear cylinders 536 in the rear case 504 communicate with the reservoir tank 507 of the front case 503 through return oil passages 546 to 549. In the rear case 504, a return oil passage 546 is formed between the rear cylinders 536 in the left-right direction so as to communicate the rear portions (rear oil chambers 552) of the pair of left and right rear cylinders 536. Further, the rear case 504 configures the return oil passage 547 as a vertical oil passage drilled upward from an intermediate position of the return oil passage 546, and the return oil passage 548 from the upper end of the return oil passage 547 to the front. It is configured as an oil passage in the front-rear direction drilled in the direction. The return oil passage 548 is open at the front end surface of the rear case 504, and an opening portion of the return oil passage 549 formed in the front case 503 from the rear of the reservoir tank 507 toward the rear end surface of the front case 503. Communicate.

  The front cylinder 508 is provided with a step so that the inner diameter forward from the middle portion is thicker than the inner diameter behind the middle portion, and the inner diameter behind the middle portion is configured to be equal to the outer diameter R1 of the output side piston 523. Yes. The front cylinder 508 is connected to a hydraulic oil passage 514, an equalizer piston oil passage 518, and a pilot valve oil passage (control port) 533 through a front portion (a portion having a large inner diameter) from the step. 1st oil chamber) 550 is comprised. In the front oil chamber 550 in the front cylinder 508, the front end of the output-side piston 523 moves in the front-rear direction, whereby the working oil is discharged or sucked into the brake cylinder 255.

  Further, the outer diameter of the front end portion in front of the notch 525 of the output side piston 523 is R1, and the axial length L2 of the notch 525 in the output side piston 523 is equal to or larger than the stroke length L1 of the output side piston 523. Yes. Accordingly, when the brake pedal 35 is in a non-operating state, as shown in FIG. 19, the outer peripheral portion of the front end of the output side piston 523 contacts the lower side of the outer peripheral surface of the valve body 511 of the check valve 510, and the valve body 511 is By tilting, the check valve 510 is opened, and the front oil chamber 550 and the reservoir tank 507 are in communication with each other.

  On the other hand, when the brake pedal 35 is operated and the output side piston 523 is pushed forward via the input side piston 501, the notch 525 of the output side piston 523 is positioned below the check valve 510. Accordingly, the check valve 510 becomes operable, and the valve body 511 opens and closes according to the oil pressures of the front oil chamber 550 and the reservoir tank 507, respectively. Since the pressure of the front oil chamber 550 in the front cylinder 507 is normally higher than the pressure of the reservoir tank 507 due to the pushing of the output side piston 523, the valve body 511 transits from the inclined state to the upright state. Is closed, and the front oil chamber 550 and the reservoir tank 507 are disconnected.

  The rear cylinder 536 is provided with a step so that the inner diameter forward from the midway portion becomes thicker than the inner diameter behind the midway portion, and the inner diameter forward from the midway portion is set to the outer diameter R2 (R2> R1) of the front end portion of the input side piston 501. ). The input side piston 501 has a shape in which the outer diameter of the front end piston portion is thicker than the outer diameter of the rear rod portion, and the front end piston portion of the input side piston 501 contacts the stepped portion of the rear cylinder 536. The rearward movement of the input side piston 501 is restricted by contacting.

  The rear cylinder 536 constitutes an intermediate oil chamber (second oil chamber) 551 into which the output side piston 523 and the check valve 527 are inserted by a front portion (a portion having a large inner diameter) from the step. The intermediate oil chamber (second oil chamber) 551 communicates with a pilot valve oil passage (input port) 543. Further, the rear cylinder 508 has a rear oil chamber (third oil chamber) communicating with the pilot valve oil passage (output port) 544 and the return oil passage 546 in the vicinity of the step in the rear portion (the portion having a small inner diameter) from the step. ) 552. Further, the rear cylinder 536 has an inner diameter of a rear end portion (a portion having a small inner diameter) from the step, which is substantially the same as a rod portion (a portion having a small outer diameter) of the input side piston 501. The rear oil chamber (third oil chamber) 552 is sealed by interposing an O-ring or the like between the rod portion of the input side piston 501 and the rear cylinder 508.

  An input port (hydraulic supply port) 553 and an output port (hydraulic discharge port) 554 communicating with the reservoir tank 507 are provided on the upper lid 506 that covers the upper side of the front case 503. The input port 553 is connected to a hydraulic circuit of an external hydraulic device such as the hydraulic lifting mechanism 22 through a hydraulic pipe, is supplied with working oil from the outside, is equipped with a filter (not shown), and is an important safety part. Dust and foreign matter are prevented from entering a certain brake valve 254. The output port 554 is connected to the hydraulic circuit of the mission case 17 through hydraulic piping, and returns the working oil in the reservoir tank 507 to the hydraulic tank (not shown) in the mission case 17.

  As described above, the brake valve 254 is inserted so that the brake piston 35 reciprocated by the brake pedal 35 is separated into the input piston (first piston) 501 and the output piston (second piston) 523. Yes. The cross sectional area of the input side piston 501 is set larger than the cross sectional area of the output side piston 523. Specifically, the outer diameter R2 of the input side piston 501 is set larger than the outer diameter R1 of the output side piston 523. Further, in the brake valve 254, the output side piston 523 is moved after the input side piston 501 is moved first by the depression operation of the brake pedal 35. Accordingly, when the brake pedal 35 is initially depressed, the brake pressure can be applied with a short stroke by the input side piston 501, and thereafter, a large brake pressure can be applied with a light pedal force by the output side piston 523. As a result, since the brake can be applied with a light pedal effort without increasing the stroke length L1 of the brake piston in the brake valve 254, the operability and braking performance of the brake pedal 35 can be improved.

  The brake valve 254 is an equalizer piston that displaces in a pair of left and right brake pistons 501 and 523 reciprocated by a brake pedal 35 and an oil chamber (piston cylinder) 516 communicating with a cylinder 508 that houses both the brake pistons 501 and 523. 519. The brake pressures at the brake pistons 501 and 523 respectively corresponding to the end portions of the equalizer piston 519 are applied, and the equalizer piston 519 is displaced in the cylinder 518. Even if there is a difference in left and right pedaling force when the left and right brake pedals 35 are depressed simultaneously, the left and right brake pistons 501 and 523 are moved by moving the equalizer piston 519 by the difference in brake pressure between the brake pistons 501 and 523. By absorbing the difference in brake pressure at the left and right, the brake pressure can be made approximately equal to the left and right (the braking force of the left and right wheels 4 can be made equivalent).

  The brake piston inserted in the brake valve 254 discharges or sucks hydraulic oil to the input side piston (first piston) 501 pressed by the brake pedal 35 and the brake cylinder 255 for braking the left and right wheels 4 of the traveling machine body 2. And an output side piston (second piston) 523 that performs the above operation. Thereby, by depressing the brake pedal 35, the input side piston 501 is moved first, and then the output side piston 523 is moved. The output side pistons 523 of the brake pistons are communicated with each other via the equalizer piston 519, and the output side The brake pressure between the pistons 523 is adjusted.

  A pressure at a connecting portion (intermediate oil chamber 551) between the input side piston 501 and the output side piston 523 is interposed between the input side piston (first piston) 501 and the output side piston (second piston) 523. When the (brake pressure) becomes higher than the pressure (brake pressure) of the output side piston 523, the check valve 527 is operated to output the output side (intermediate oil chamber 551) of the input side piston 501 and the output side (front) of the output side piston 523. The oil chamber 550) is communicated to release the pressure (brake pressure) on the input side piston 501 side to the output side piston 523 side. At this time, the operation of the check valve 527 causes the working oil having a flow rate based on the displacement of the input side piston 501 to be discharged to the brake cylinder 255. The state where the input side piston 501 is connected to the output side piston 523 can be maintained, and the pressing force from the input side piston 501 can be transmitted to the output side piston 523. Therefore, in the initial step of depression of the brake pedal, the brake pressure can be applied with a short stroke by the input side piston 501, which contributes to improvement in the operability of the brake pedal 35.

  The brake valve 245 includes a reservoir tank 507 communicating with the input side (rear oil chamber 552) of the input side piston (first piston) 501. The brake valve 245 includes an output side (intermediate oil chamber 551) of the input side piston 501 and the reservoir tank 507. A pilot valve 537 is interposed between the two. The pilot valve 537 operates when the brake pressure of the output side piston (second piston) 523 becomes higher than a predetermined pressure, and connects the output side (intermediate oil chamber 551) of the input side piston 501 to the reservoir tank 507. Then, the brake pressure of the input side piston 501 is released. At this time, when the pilot valve 537 is opened, the check valve 527 is closed, and the working oil having a flow rate based on the displacement of the output side piston 523 is discharged to the brake cylinder 255. That is, when the brake pressure on the output side piston 523 reaches a predetermined pressure by the depression operation of the brake pedal 35, the pilot valve 537 operates to release the brake pressure on the input side piston 501 side to the reservoir tank 507, and the output side piston 523. Just hold the brake pressure. Since the switching from the brake operation state by the input side piston 501 to the brake operation state by the output side piston 523 becomes smooth, it contributes to the improvement of the operability of the brake pedal 35.

  In addition, the structure of each part in this invention is not limited to embodiment of illustration, A various change is possible in the range which does not deviate from the meaning of this invention.

DESCRIPTION OF SYMBOLS 1 Tractor 2 Traveling machine body 3 Front wheel 4 Rear wheel 7 Cabin 8 Control seat 35 Brake pedal 254 Brake valve 255 Brake cylinder 256 Brake hydraulic piping 501 Input side piston (first piston)
502 Valve case 503 Front case 504 Rear case 505 Fixing flange 506 Top cover 507 Reservoir tank 508 Front cylinder 509 Front sealing plug 510 Check valve 511 Valve body 512 Plug (for check valve)
513 Through hole 514 Oil passage (for hydraulic piping)
515 Connection port 516 Piston cylinder (for equalizer piston)
517 Seal plug (left and right pair)
518 Oil passage (for equalizer piston)
519 Equalizer piston 520 Coil spring 521 Left adjustment oil chamber 522 Right adjustment oil chamber 523 Output side piston (second piston)
524 Through hole (oil passage in piston)
525 Notch 526 Spring 527 Check valve 528 Plug 529 Through hole 530 Valve body 531 Valve input side oil chamber 532 Communication hole 533 Oil passage (control port)
534 Vertical hole 535 Horizontal hole 536 Rear cylinder 537 Pilot valve 538 Valve body 539 Hollow part (oil chamber)
540 Communication hole 541 Valve cylinder 542 Cylinder rear oil passage 543 Oil passage (input port)
544 Oil passage (Output port)
545 Spring 546 Return oil path 547 Return oil path 548 Return oil path 549 Return oil path 550 Front oil chamber (first oil chamber)
551 Intermediate oil chamber (second oil chamber)
552 Rear oil chamber (third oil chamber)
553 Input port 554 Output port

Claims (2)

In a work vehicle comprising a brake valve for braking a wheel of a traveling machine body, and a brake pedal for reciprocating a brake piston in the brake valve,
The brake piston is configured to be separated into a first piston and a second piston, the cross-sectional area of the first piston is set larger than the cross-sectional area of the second piston,
The first piston is moved first by the depression operation of the brake pedal, and then the second piston is moved .
The brake valve includes a reservoir tank communicating with the input side of the first piston,
A pilot valve is interposed between the output side of the first piston and the reservoir tank, and the pilot valve is activated when the pressure on the output side of the second piston becomes higher than a predetermined pressure. A work vehicle characterized in that an output side of the first piston communicates with the reservoir tank .    A check valve is interposed between the first piston and the second piston, and when the pressure at the connecting portion of the first piston and the second piston becomes higher than the pressure of the second piston, the check valve 2. The work vehicle according to claim 1, wherein the output side of the first piston and the output side of the second piston are made to communicate with each other.

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