Work vehicles

Abstract

To provide a work vehicle that can reliably and freely control work equipment using an external hydraulic valve. [Solution] The system includes a work machine 14 mounted on a vehicle body 10, a first external hydraulic valve unit 60 that controls the hydraulic fluid that operates the first valve spool 70 using a proportional solenoid valve 64 and operates hydraulic equipment 17 and 18 mounted on the work machine 14, a pressure reducing valve 72 that controls the pressure of the hydraulic fluid that operates the first valve spool 70 and a pump 71 that supplies the hydraulic fluid, a first branching point 74 that branches off the hydraulic fluid that operates the first valve spool 70 from the pump 71, a second branching point 75 that branches off the hydraulic fluid that operates the hydraulic equipment 17 and 18, a pressure compensation valve 73 downstream of the second branching point 75 that compensates for the pressure of the oil passage including the second branching point 75, and hydraulic fluid unloaded from the pressure compensation valve 73 that is supplied to the second external hydraulic valve unit 90 or the main valve 80.

Description

Technical Field

[0001] The present invention relates to a work vehicle such as an agricultural tractor.

Background Art

[0002] There is a known work vehicle in which a working machine such as a front loader is attached to a work vehicle such as an agricultural tractor and the working machine is moved by an external hydraulic operation lever or a JOY stick lever (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventional external hydraulic operation levers and JOY stick levers are connected to an external hydraulic valve by wires or the like and are configured to directly operate the valve spool of the external hydraulic valve. Therefore, they cannot be automatically operated depending on the surrounding environment or the state of the work vehicle. In addition, a conventional work vehicle provides a flow control valve between a first external hydraulic valve unit and a second external hydraulic valve unit, and this flow control valve has a variable throttle in the supply oil passage to the first external hydraulic valve unit, and adjusts the flow rate to the second external hydraulic valve unit by the differential pressure before and after the variable throttle. In addition to the need to manually and appropriately adjust the variable throttle in this conventional work vehicle, when the load on the downstream second external hydraulic valve unit or the lifting control valve, which is the main valve, increases, it affects the flow control valve and the flow rate to the first external hydraulic valve unit becomes unstable, and there are problems such as the control of the actuator by the first external hydraulic valve unit becoming unstable.

[0005] Therefore, an object of the present invention is to provide a work vehicle capable of stably and freely controlling a working machine by an external hydraulic valve. [Means for solving the problem]

[0006] Therefore, the work vehicle according to the invention employs the following technical means to solve the above problems.

[0007] The vehicle body (10) is equipped with a work implement (14), a proportional solenoid valve (64) controls the hydraulic fluid that operates the first valve spool (70), and a first external hydraulic valve unit (60) that operates hydraulic equipment (17, 18) mounted on the work implement (14), and a pressure reducing valve (72) controls the pressure of the hydraulic fluid that operates the first valve spool (70). The system includes a pump (71) for supplying hydraulic fluid, a first branching point (74) for branching hydraulic fluid from the pump (71) to operate the first valve spool (70), and a second branching point (75) for branching hydraulic fluid to operate the hydraulic equipment (17, 18). Downstream of the second branching point (75) is a pressure compensation valve (73) for compensating the pressure in the oil passage including the second branching point (75), and the hydraulic fluid unloaded from the pressure compensation valve (73) is supplied to the second external hydraulic valve unit 90 or the main valve (80). [Effects of the Invention]

[0008] According to the work vehicle of the present invention, the control of the work machine by an external hydraulic valve can be performed stably and freely. [Brief explanation of the drawing]

[0009] [Figure 1] Left side view of an agricultural tractor according to an embodiment of the present invention [Figure 2] Plan view of the cabin of an agricultural tractor according to an embodiment of the present invention [Figure 3] Enlarged plan view of the right side dashboard portion of an agricultural tractor according to an embodiment of the present invention. [Figure 4] Perspective view of the interior of the cabin of an agricultural tractor according to an embodiment of the present invention, viewed from the front left. [Figure 5] Perspective view of the rear of the cabin of an agricultural tractor according to an embodiment of the present invention. [Figure 6] Perspective view of the cabin of an agricultural tractor according to an embodiment of the present invention, viewed from the front. [Figure 7] Hydraulic circuit diagram of an external hydraulic valve for an agricultural tractor according to an embodiment of the present invention. [Figure 8] Block diagram showing a control system for an agricultural tractor according to an embodiment of the present invention. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described below with reference to the drawings. In this specification, the left and right sides in the forward direction of the work vehicle will be referred to as left and right, respectively, and the front and rear will be referred to as front and rear, respectively.According to embodiments of the present invention, an agricultural machine tractor, which is an example of a work vehicle, will be described below as an example.

[0011] Figure 1 is a left side view of the agricultural tractor according to this embodiment. Figure 2 shows a plan view of the cabin of the agricultural tractor according to this embodiment, and Figure 3 shows an enlarged plan view of the right side dashboard. Figure 4 is a perspective view of the interior of the cabin of the agricultural tractor according to this embodiment, viewed from the front left, Figure 5 is a perspective view of the cabin, viewed from the rear, and Figure 6 is a perspective view of the cabin, viewed from the front.

[0012] As shown in Figure 1, the tractor 10 of this embodiment is configured with a pair of drive rear wheels 12 mounted on the rear of the vehicle body and left and right front wheels 11, which are steered by a steering wheel 20, mounted on the front. The tractor 10 has a cabin that surrounds the driver's seat 21 equipped with a steering wheel 20, and the front side of the cabin is covered with a bonnet 13. Inside the bonnet, the engine and its auxiliary components, namely the radiator, oil cooler, air conditioning condenser, intercooler, air cleaner, battery, etc., are installed.

[0013] As shown in Figure 1, the tractor 10 is equipped with a front loader 14 on the front of the vehicle body.

[0014] The front loader 14 includes a pair of left and right side frames 19 attached to both sides of the vehicle body of the tractor 10, a main frame 16 pivotally connected to the upper part of the side frame 19 and supported so as to be vertically swingable, and a bucket 15 pivotally connected to the tip side of the main frame 16 and supported so as to be vertically swingable. Further, a main frame swing cylinder 18 that can be telescopically operated is connected between the base of the side frame 19 and the central part of the main frame 16, and a bucket swing cylinder 17 that controls the swing of the bucket 15 is connected to the upper front part of the main frame 16.

[0015] Note that the tractor 10 is an example of the work vehicle of the present invention, and the front loader 14 is an example of the working machine of the present invention.

[0016] Further, the tractor 10 of the present embodiment can be attached to a three-point link mechanism configured with a working machine (not shown) such as a rotary tiller at the rear of the machine body so as to be able to be lifted and lowered, and perform ground work.

[0017] Next, the arrangement of each operating tool in the cab of the tractor 10 of the present embodiment will be described.

[0018] The driver's seat 21 arranged in the center of the cab has an armrest 26 on the left side. On both sides of the driver's seat 21, a right side dashboard 22 and a left side dashboard 23 are erected.

[0019] A step is provided at the upper part of the right side dashboard 22, and it has two substantially horizontal surfaces, an upper step surface 24 and a lower step surface 25. As shown in FIG. 4, the upper step surface 24 is formed at the rear outer side of the upper part of the right side dashboard 22, and the lower step surface 25 is formed at the front inner side of the upper part of the right side dashboard 22.

[0020] Operating tools for operating the working machine are concentratedly arranged on these upper step surface 24 and lower step surface 25.

[0021] On the upper step surface 24, a triple external hydraulic lever 34 is arranged.

[0022] A position lever 31 is located at the front end of the lower surface 25, and a PTO selector switch 32 and a tilling depth adjustment dial 33 are located near the rear end of the position lever 31. Further behind the PTO selector switch 32 and tilling depth adjustment dial 33, a PTO on / off switch 35 is located. The PTO selector switch 32 is a switch that switches between an automatic mode in which the PTO is turned on and off in conjunction with the vehicle status, and a manual mode in which the PTO is turned on and off only by the PTO on / off switch 35.

[0023] As shown in Figure 3, a lower position adjustment dial 37 is provided at the front end of the base of the position lever 31, and an upper position adjustment dial 38 is provided at the rear end of the base of the position lever 31.

[0024] The position lever 31 is a lever that controls the raising and lowering of the work implement. The rear position controls "raising," and the front position controls "lowering," allowing the work implement to be raised or lowered during machine rotation, etc. The lowering position adjustment dial 37 and the raising position adjustment dial 38 adjust the forward and backward range of motion of the position lever 31, thereby regulating the height range in which the work implement moves up and down.

[0025] Furthermore, the PTO on / off switch 35 is a dial type, so it will not malfunction even if part of the operator's body comes into contact with it. In addition, because it is positioned closest to the operator's seat 21 behind the tillage depth adjustment dial 33, the operator can operate it immediately, making it effective in terms of safety.

[0026] By placing frequently used controls on the lower surface 25, which is close to the driver's seat 21, the operator can operate the controls smoothly.

[0027] Furthermore, the JOY stick lever 30 is positioned in front of the right-side dashboard 22, in a location that is easily operated with the right hand by an operator seated in the driver's seat 21.

[0028] On the other hand, the controls for the driving system are concentrated between the driver's seat 21 and the right-side dashboard 22.

[0029] The main shift lever 40 is positioned between the driver's seat 21 and the right-side dashboard 22, in a location easily accessible with the right hand. Behind the main shift lever 40, the sub-shift lever 41 and the creep speed lever 42 are positioned in order. The sub-shift lever 41 can be fixed in any position, and the travel speed of the tractor 10 can be maintained at a constant level depending on the position of the lever.

[0030] The PTO selector switch 32 is located on the lower surface 25 of the right-side dashboard 22, in a position close to the main shift lever 40.

[0031] In this way, by concentrating the operating tools for the work equipment on the right-side dashboard 22 and concentrating the operating tools for the drive system between the driver's seat 21 and the right-side dashboard 22, the operator can easily understand the location of the operating tools and operate them smoothly.

[0032] The JOY stick lever 30 is an example of the loader lever of the present invention, and the main change lever 40 is an example of the main gear shift lever of the present invention. Also, the right-side dashboard 22 is an example of the side dashboard of the present invention.

[0033] As shown in Figure 4, the JOY stick lever 30 is positioned so that its tip is higher than the seat surface of the driver's seat 21, and the main change lever 40 is also positioned so that its tip is higher than the seat surface of the driver's seat 21.

[0034] Furthermore, although both the JOY Stick Lever 30 and the Main Change Lever 40 are levers that are operated in the forward and backward directions, they are positioned such that when an operator grips the tip of either lever at the closest position between the JOY Stick Lever 30 and the Main Change Lever 40, there is a gap between the hand gripping that lever and the other lever. Therefore, when an operator operates the JOY Stick Lever 30 or the Main Change Lever 40, their body will not accidentally come into contact with the other lever, resulting in incorrect operation.

[0035] Furthermore, instead of arranging the JOY stick lever 30 and the main change lever 40 side by side in the front-to-back direction of the aircraft, they are positioned offset from each other in the left-to-right direction of the aircraft, as shown in Figure 2. This improves operability when frequently operating these levers.

[0036] The accelerator pedal 49 is located on the floor to the right and front of the driver's seat 21.

[0037] Additionally, a 4WD lever 43 is located below and to the right of the driver's seat 21, and a PTO shift lever 36 is located below and to the left of the driver's seat 21. Furthermore, a differential lock pedal 44 is located below and to the right of the driver's seat 21.

[0038] A hazard switch 50 is located to the left front of the steering wheel 20.

[0039] As shown in Figure 5, a center horn 51 is provided in the center of the steering wheel 20. From the perspective of an operator seated in the driver's seat 21, the forward / reverse lever 45 is located to the left rear of the steering wheel 20, and the turn signal lever 52 is located to the right rear of the steering wheel 20. The throttle lever 46 is located to the right front of the steering wheel 20, and the key switch 53 and parking lever 54 are located to the lower right of the steering wheel 20.

[0040] The left and right brake pedals 48 are positioned near the floor, slightly to the right and forward of the driver's seat 21, while the clutch pedal 47 is positioned near the floor, slightly to the left and forward of the driver's seat 21. Additionally, the tilt pedal 55 is positioned near the floor, slightly to the left and below the steering wheel 20.

[0041] In the above description, the 4WD lever 43 and the PTO shift lever 36 are positioned on a surface that rises vertically from the floor below the driver's seat 21 and have a lever shape that extends forward. However, they may also be positioned closer to the side of the driver's seat 21 and have a lever shape that extends upward.

[0042] As shown in Figure 7, the first valve spool 70 of the first external hydraulic valve unit 60 slides on a connected piston 65. The piston 65 is moved by hydraulic fluid supplied at an arbitrary flow rate by a proportional solenoid valve 64. The pressure of the hydraulic fluid that controls the piston 65 by the proportional solenoid valve 64 is regulated by a pressure reducing valve 72. The pressure reducing valve 72 adjusts the pressure of the hydraulic fluid that has branched off from the pump 71 at the first branching point 74 and supplies it to the proportional solenoid valve 64. Therefore, even if the pressure of the hydraulic fluid supplied from the first branching point 74 fluctuates due to the load of the downstream second external hydraulic valve unit 90 and the main valve 81, which will be described later, the first valve spool 70 can be controlled stably. Since the speed at which the first valve spool 70 moves can also be controlled by the proportional solenoid valve 64, the extension and retraction speed of the main frame oscillating cylinder 18 can also be controlled, allowing the front loader 14 to be freely controlled.

[0043] The tractor 10 is also equipped with an implement 80 at the rear, which is raised and lowered by a main cylinder 82 controlled by a main valve 81. The main valve 81 is supplied with hydraulic fluid from a pump 71 via a first external hydraulic valve unit 60 and a second external hydraulic valve unit 90. A pressure reducing valve 72 is provided between the first branch point 74 and the proportional solenoid valve 64, and the first valve spool 70 is operated by hydraulic fluid with adjusted pressure, so that the main valve 81 can maintain stable electronic control even if the pressure in the oil passage including the first branch point 74 becomes excessive.

[0044] Hydraulic fluid is supplied from the upstream pump 71. At the first branching point 74, one branch is converted into an oil passage that operates the first valve spool 70, and the other branch is converted into an oil passage that operates the main frame oscillating cylinder 18 by switching direction to the first valve spool 70 at the second branching point 75 downstream of the first branching point 74, and the other branch is converted into an oil passage that flows to the downstream second external hydraulic valve unit 90 and main valve 81.

[0045] Downstream from the second branching point 75, a pressure compensation valve 73 is provided between the second branching point 75 and the second valve spool 91 of the second external hydraulic valve unit 90, allowing the hydraulic fluid unloaded from the pressure compensation valve 73 to be supplied to the second external hydraulic valve unit 90. The first external hydraulic valve unit 60 is equipped with a second port 62 from which hydraulic fluid is released when the main frame oscillating cylinder 18 is retracted and a third port 63 from which hydraulic fluid is released when the main frame oscillating cylinder 18 is extended, and an oil passage 67 is configured to take the pressure connected to the second port 62 or the third port 63 and connect to the spring chamber of the pressure compensation valve 73.

[0046] As a result, when operating the main frame oscillating cylinder 18, the flow rate unloaded from the pressure compensation valve 73 can be controlled by the pressure difference between the pressure in the oil passage including the second branching point 75 and the pressure of the hydraulic fluid output from the second port 62 or third port 63 that operates the main frame oscillating cylinder 18. Therefore, the flow rate output to the second port 62 or third port 63 can be controlled according to the opening amount of the first valve spool 70, and the excess flow rate can be supplied to the second external hydraulic valve unit 90 or the main valve 81. In other words, the flow rate for operating the main frame oscillating cylinder 18 and the flow rate supplied to the second external hydraulic valve unit 90 or the main valve 81 can be adjusted to maintain a good balance.

[0047] When the first valve spool 70 is in the neutral position and the main frame oscillating cylinder 18 is not being operated, the first valve spool 70 acts as a block, blocking the flow between the second branching point 75 and the main frame oscillating cylinder 18. At this time, the oil passage 67 connected to the spring chamber of the pressure compensation valve 73 is connected to the tank port 66 that discharges hydraulic fluid toward the tank 88. As a result, when the main frame oscillating cylinder 18 is not being operated, a greater flow rate of hydraulic fluid can be secured to supply the second external hydraulic valve unit 90 and the main valve 81 than when the main frame oscillating cylinder 18 is being operated.

[0048] The set pressure at which the pressure compensation valve 73 unloads when the first valve spool 70 is in the neutral position is configured so that the supply oil passage to the pressure reducing valve 72, including the first branch point 74, does not fall below the set pressure even when the rotational speed of the pump 71, which is operated by a prime mover such as an engine, decreases due to idling or other reasons. As a result, the control pressure of the first external hydraulic valve unit 60 can always be maintained at a constant pressure, allowing for stable electronic control.

[0049] The first external hydraulic valve unit 60 has a stack configuration in which its body 69 is stacked with the first block 79, which forms the first branching point 74, and the body 99 of the second external hydraulic valve unit 90, and the pressure reducing valve 72 is built into the first block 79. The first block 79 is necessary for supplying hydraulic fluid from the pump 71 to the first external hydraulic valve unit 60, so integrating the pressure reducing valve 72 into it allows for space saving.

[0050] As shown in Figure 8, the tractor 10 has a control unit 100 that controls the proportional solenoid valve 64 based on signals input from sensors, etc. Specifically, signals from a JOY stick sensor 91 that detects the operation of the JOY stick lever 30, an external hydraulic lever sensor 92 that detects the operation of the external hydraulic lever 34, a steering sensor 93 that detects the steering angle of the wheels or the operation of the steering handle 20, a vehicle speed sensor 94 that detects the vehicle speed, a forward / reverse lever sensor 95 that detects the operation of the forward / reverse lever 45, a seat sensor 96 that detects whether the driver is seated or left the driver's seat 21, a clutch sensor 97 that detects the operation of the clutch pedal 47 or the clutch pressure, and a brake sensor 98 that detects the operation of the left and right brake pedals 48 or the operation of the brake device are input, and the system is configured to process these signals and electronically control the proportional solenoid valve 64 to operate the first external hydraulic valve unit 60.

[0051] With the above configuration, the tractor 10 can stably electronically control the first valve spool 70 even if there are changes in the state of the main valve 81 or pump 71, thanks to the compact configuration of the first external hydraulic valve unit 60.

[0052] In the above embodiment, a front loader 14 operated by the JOY stick lever 30 was shown as the work implement to be attached, but it is not limited to this, and other work implements may be a reversible plow with a reversing mechanism, a harrow with a folding mechanism used for puddling work, a rake for collecting hay, or a tedda for spreading hay, which are equipped with hydraulic equipment such as hydraulic cylinders and operated by an external hydraulic lever 34 and a first external hydraulic valve unit 60.

Description of Symbols

[0053] 10 Tractor (traveling vehicle body) 14 Front loader (working machine) 17 Bucket swing cylinder (hydraulic equipment) 18 Main frame swing cylinder (hydraulic equipment) 60 First external hydraulic valve unit 64 Proportional solenoid valve 66 Tank port 67 Oil passage 70 First valve spool 71 Pump 72 Pressure reducing valve 73 Pressure compensating valve 74 First branch point 75 Second branch point 79 Block 80 Main valve 88 Tank

Claims

1. A work implement (14) attached to the vehicle body (10), A first external hydraulic valve unit (60) controls the hydraulic fluid that operates the first valve spool (70) by a proportional solenoid valve (64) and operates the hydraulic equipment (17, 18) mounted on the work machine (14), The system includes a pressure reducing valve (72) that controls the pressure of the hydraulic fluid that operates the first valve spool (70), A pump (71) that supplies hydraulic fluid, A first branching point (74) is provided for branching the hydraulic fluid that operates the first valve spool (70) from the pump (71), The system includes a second branching point (75) for branching the hydraulic fluid that operates the aforementioned hydraulic equipment (17, 18), A pressure compensation valve (73) is provided downstream of the second branching point (75) to compensate for the pressure in the oil passage including the second branching point (75). A work vehicle in which hydraulic fluid unloaded from the pressure compensation valve (73) is supplied to a second external hydraulic valve unit (90) or a main valve (80).

2. The pressure compensation valve (73) is equipped with an oil passage (67) connected to the spring chamber, When the hydraulic equipment (17, 18) is operating, the oil passage (67) connects the pressure of the hydraulic fluid that operates the hydraulic equipment (17, 18) to the spring chamber of the pressure compensation valve (73). If the hydraulic equipment (17, 18) is not operating, the pressure of the tank port (66) that discharges hydraulic fluid into the tank (88) is connected to the spring chamber of the pressure compensation valve (73). The work vehicle according to claim 1, wherein the pressure compensation valve (73) controls the flow rate to be unloaded by the differential pressure between the oil passage (67) and the oil passage including the second branch point (75).

3. The work vehicle according to claim 2, wherein the first valve spool (70) blocks the flow between the second branch point (75) and the hydraulic equipment (17, 18) when the hydraulic equipment (17, 18) is not in operation.

Images