JP2016121713A - Work vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a work vehicle which stably performs hydraulic servo control of a hydraulic static transmission (HST).SOLUTION: A work vehicle includes a hydraulic static transmission (HST) 60 and a main pump P1 and a sub pump P2 which supply a hydraulic fluid to a hydraulic circuit. The hydraulic fluid is supplied from the main pump P1 to a power steering device 31, and the hydraulic fluid is branched and supplied from the sub pump P2 to a hydraulic servo 60s of the HST 60, a charge circuit 60c of the HST 60, and a PTO clutch 27. A pressure control valve 103 is disposed at the upstream of the charge circuit 60c of the HST 60.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a work vehicle having a hydraulic circuit including a power steering device.

  Pressure oil supply to the power steering device, pressure oil supply to the PTO clutch, and hydraulic oil supply to the hydraulic servo and charge circuit of the hydrostatic continuously variable transmission have different required pressures, and the flow rate must also be considered. However, a work vehicle equipped with a hydraulic circuit for supplying pressure oil to these devices with a single supply pump by connecting a charge circuit of a hydrostatic continuously variable transmission to a return oil circuit of a power steering device. Known (Patent Document 1).

JP 2000-240778 A

  However, in the technique described in Patent Document 1, back pressure is generated in the tank port of the power steering apparatus. However, if the back pressure becomes too high, it causes an increase in steering operation load, deterioration in feeling, and the like. In order to prevent this, it is necessary to place a pressure reducing valve upstream of the power steering and control the pressure to limit the back pressure of the power steering device. However, since the downstream flow rate changes during pressure control by the pressure reducing valve, the flow rate for controlling the hydraulic servo of the hydrostatic continuously variable transmission located downstream may be insufficient, and the control has become unstable. .

  Furthermore, the vibration generated by the variable displacement pump in the hydrostatic continuously variable transmission is transmitted to the hydraulic servo, and the pulsation generated due to the vibration causes pressure exceeding the allowable pressure to be applied to the PTO clutch, resulting in damage. There was a thing.

  In order to solve the above-described problems, the first invention includes a hydrostatic continuously variable transmission and a power steering device, and includes a main pump and a sub pump that supply hydraulic oil to a hydraulic circuit. The hydraulic oil is supplied from the pump, and the hydraulic oil is supplied from the sub-pump to the hydraulic servo of the hydrostatic continuously variable transmission and the charge circuit of the hydrostatic continuously variable transmission, and the hydrostatic continuously variable transmission is charged. It is characterized in that it has a hydraulic circuit in which a pressure control valve is arranged upstream of the circuit.

  The second invention has a PTO clutch that is hydraulically operated in the first invention. The PTO clutch is supplied with branching pressure oil from a sub pump, and the pressure oil is supplied to the charge circuit of the hydrostatic continuously variable transmission. It is characterized in that a pressure control valve is arranged upstream of the oil passage to be supplied.

  According to a third aspect of the present invention, in the second aspect of the present invention, a control valve that opens and closes a flow path to the PTO clutch is provided in an oil passage that supplies hydraulic oil to the PTO clutch. It is characterized in that a hydraulic servo control valve for controlling the hydraulic servo is provided to be freely opened and closed.

  According to the fourth aspect of the invention, in any one of the first to third aspects of the invention, a flow control valve is disposed upstream of the power steering device, and a tank port of the power steering device is opened to the tank. Has characteristics.

  According to the first aspect of the invention, the main pump and the sub pump are provided as pumps for supplying pressure oil to each device, the power steering device is supplied with pressure oil from the main pump, and the hydraulic servo and charge circuit of the hydrostatic continuously variable transmission By supplying pressure oil from the sub pump, means such as arranging a pressure reducing valve necessary for suppressing the back pressure of the power steering device is not required. For this reason, it can prevent that the flow volume of the hydraulic fluid supplied to the hydraulic servo of a hydrostatic continuously variable transmission is insufficient.

  According to the second invention, in addition to the effect of the first invention, in the configuration in which the pressure oil is also branchedly supplied from the sub pump to the PTO clutch, the pressure control valve is provided upstream of the charge circuit of the hydrostatic continuously variable transmission. Therefore, it is possible to ensure an appropriate pressure for the PTO clutch. Furthermore, even if high pressure is generated due to pulsation caused by vibration generated by the variable displacement pump in the hydrostatic continuously variable transmission, the pressure control valve upstream of the charge circuit escapes to the charge circuit side of the hydraulic continuously variable transmission. Therefore, damage to the PTO clutch can be prevented.

  According to the third invention, in addition to the effect of the second invention, a sufficient flow rate can be supplied to the charge circuit by closing the control valve when the operation of the PTO clutch and the hydraulic servo is unnecessary.

  According to the fourth invention, in addition to the effect of any one of the first to third inventions, the flow rate to the power steering device can be kept constant by the flow rate adjusting valve. Furthermore, since the downstream is open to the tank port, no back pressure is generated, so that the performance of the power steering device can be maintained in a good state.

Side view of the entire tractor Schematic diagram of steering mechanism Power transmission mechanism diagram of tractor transmission Cross section of PTO clutch Hydraulic circuit diagram Another form of hydraulic circuit diagram

  An embodiment of a tractor as an example of a work vehicle will be described below.

  In the present specification, the left and right directions in the forward direction of the work vehicle are referred to as left and right, respectively, the forward direction is referred to as front, and the reverse direction is referred to as rear.

  As shown in FIG. 1, the tractor 1 includes front wheels 2, 2 and rear wheels 3, 3 at the front and rear portions of the fuselage, and the rotation of the engine output shaft 20 of the engine 5 mounted on the front portion of the fuselage A plurality of transmissions are used to decelerate in multiple stages and transmit to the front wheels 2, 2 and the rear wheels 3, 3.

  A steering handle 7 is provided on the handle post 6 in the cabin 190, and a seat 9 is provided behind the steering handle 7. Below the steering handle 7 is provided a forward / reverse lever 10 for switching the advancing direction of the airframe to the front / rear direction. When the forward / reverse lever 10 is operated to the front side, the airframe moves forward, and when operated to the rear side, it moves backward.

  An accelerator lever 11 for adjusting the engine speed is provided on the opposite side of the forward / reverse lever 10 with the handle post 6 in between, and an accelerator for similarly adjusting the engine speed is provided at the right corner of the step floor 13. The pedal 18 and left and right brake pedals 19R and 19L for operating the left and right rear wheels 3 and 3 are provided.

  A meter panel 16 is provided on the front side of the steering handle 7 at the upper part of the handle post 6 to display the vehicle status such as traveling speed.

  The main transmission lever 14 for shifting the main transmission mechanism is located on the left front side portion of the seat 9, the auxiliary transmission lever 15 for shifting the auxiliary transmission mechanism is located behind it, and further, the PTO transmission for shifting the PTO shaft 111 to the right side thereof. A lever 12 is provided.

  A rotary working machine 17 is mounted on the rear part of the tractor 1 so as to be driven by a PTO shaft 111 protruding rearward from the mission case 8.

  A rear case of the transmission case 8 is provided with a cylinder case 26 in which a main cylinder 25 is housed. The piston in the main cylinder 25 reciprocates, whereby the lift arm 27 rotates about the lift arm rotation fulcrum 27a, and the lift rod The rotary working machine 17 is moved up and down by rotating the lower link 29 up and down via 28.

  FIG. 2 is a schematic view of the steering mechanism.

  The rotation of the steering handle 7 is input to the power steering device 31 via the handle shaft 30. The power steering device 31 selects the oil passage a and the oil passage b depending on the rotation direction of the steering handle 7 for the hydraulic oil supplied from the pump port 31P, and the gerotor pump 31g built therein operates the flow rate according to the rotation amount. Oil is sent to the steering cylinder 32.

  When the power steering device 31 selects the oil passage a as the supply oil passage, the cylinder 32a is pushed out, and the hydraulic oil pushed out from the steering cylinder 32 goes out from the tank port 31T through the oil passage b.

  When the power steering device 31 selects the oil passage b as the supply oil passage, the cylinder 32a is pulled in, and the hydraulic oil pushed out from the steering cylinder 32 passes through the oil passage a and exits from the tank port 31T.

  The steering cylinder 32 rotates one front wheel 2 via a drag rod 33, but the left and right front wheels 2, 2 are connected to the left and right knuckle arms 35 by tie rods 34, and thus simultaneously rotate in the same direction.

  With these functions, the traveling direction of the tractor 1 is changed to the left and right.

  FIG. 3 is a power transmission mechanism diagram showing a configuration of a transmission in which a hydrostatic continuously variable transmission (HST) 60 is incorporated in a power transmission system.

  The engine output shaft 20 of the engine 5 is connected to the input shaft 59 of the HST 60 via the main clutch 112. The input shaft 59 of the HST 60 is interlocked and connected to the pump output shaft 61, the PTO first gear 62 fixed to the pump output shaft 61 is engaged with the PTO second gear 63 fixed to the first PTO shaft 28, and the PTO clutch 27 is interposed. To drive the PTO shaft 111.

  Further, the second traveling gear 66, the third traveling gear 67, and the fourth traveling gear 68 are meshed with the first traveling gear 65 fixed to the motor output shaft 64 of the HST 60, and further, the fifth traveling gear is fixed to the first traveling shaft 70. Engage with the traveling gear 69 to transmit. The third traveling gear 67 and the fourth traveling gear 68 are integrally supported by the pump output shaft 61 to save the transmission space.

  In the configuration in which the illustrated fourth traveling gear 68 and the fifth traveling gear 69 are engaged, the vehicle speed can be adjusted and changed by design. However, the fourth traveling gear 68 is eliminated and the third traveling gear 67 is replaced with the third traveling gear 67. By directly meshing with the five traveling gears 69, the number of parts can be reduced.

  The first traveling shaft 70 is fixed with a sixth traveling gear 71, a seventh traveling gear 72, and an eighth traveling gear 73, and three shift gear portions 76a of a shift gear 76 that are spline-fitted to the idle shaft 74 and the drive pinion shaft 79. , 76b, 76c, and the drive pinion shaft 79 is shifted in three stages.

  The rotation of the drive pinion shaft 79 is transmitted to the rear differential gear 81, the ninth travel gear 82, and the tenth travel gear 83 by the bevel gear 80, and drives the rear axle 84 of the rear wheel 3.

  The rotation of the drive pinion shaft 79 is transmitted to the front wheel drive shaft 52 through the eleventh traveling gear 85, the twelfth traveling gear 86, the thirteenth traveling gear 87, and the traveling clutch gear 88, and the front differential gear 89 The front first traveling shaft 90 and the front second traveling shaft 91 are transmitted to the front axle 92 to drive the front wheels 2.

  FIG. 4 is a sectional view of the PTO clutch 27.

  The clutch shaft 27a integrated with the PTO second gear 63 is rotatably supported by the first PTO shaft 28 by the second bearing 42 and the third bearing 43, and a plurality of inner clutch plates 27b are provided at the rear portion. Have.

  The rear portion of the clutch shaft 27a is covered with a clutch case 27d, and a presser plate 27e fixed to the inside of the front portion of the clutch case 27d is positioned in front of the front ends of the plurality of inner clutch plates 27b.

  A plurality of outer clutch plates 27c are alternately arranged inside the clutch case 27d so as to be sandwiched between the inner clutch plates 27b, and the inner clutch plates 27b have a plurality of teeth on the inner side. The outer clutch plate 27c rotates integrally with the shaft 27a and rotates integrally with the clutch case 27d because it has a plurality of teeth on the outer side.

  The clutch case 27d has a clutch piston 27f at the rear part of the clutch shaft 27a and is urged rearward by a spring 27g. The rear part of the clutch piston 27f has a space for a cylinder part 27h to which pressure oil is supplied. .

  In the PTO clutch 27, when pressure oil is supplied to the cylinder portion 27h and the pressure exceeds the elastic force of the spring 27g, the clutch piston 27f moves forward, and the inner clutch plate 27b and the outer clutch plate 27c are sandwiched between the presser plate 27e. Press.

  The inner clutch plate 27b and the outer clutch plate 27c, which are pressed, transmit the driving force to each other by friction, and the driving force transmitted from the PTO second gear 63 is transmitted to the clutch case 27d, and the clutch case 27d is splined. The fitted first PTO shaft 28 rotates.

  When no pressure oil is supplied to the cylinder portion 27h and no pressure is applied, the clutch piston 27f is pushed rearward by the elastic force of the spring 27g, so that the inner clutch plate 27b and the outer clutch plate 27c are not pressed.

  In this state, the inner clutch plate 27b and the outer clutch 27c do not transmit driving force to each other. Therefore, the PTO clutch 27 is in a state of interrupting power transmission, and even if the PTO second gear 63 rotates, the first PTO shaft 28 rotates. do not do.

  FIG. 5 shows a hydraulic circuit of the tractor.

A main pump P1 and a sub-pump P2 are provided as pumps for supplying pressure oil in response to driving of the engine. Pressure oil is supplied from the main pump P1 to work equipment hydraulic equipment such as the power steering device 31 and the main cylinder 25. PTO clutch 27 from sub pump
Pressure oil is supplied to HST60.

  A first pressure control valve 101 is connected to the oil passage immediately after coming out of the main pump P1, and oil is returned to the tank T when the supply pressure exceeds a certain level.

  The pressure oil from the main pump P1 is supplied to the working machine hydraulic equipment such as the main cylinder 25 and the power steering device 31 through the flow dividing valve 102. The power steering device 31 is supplied with the flow dividing valve 102 as a flow rate adjusting valve. Oil is supplied at a constant flow rate. The diversion valve 102 has a function of adjusting the flow rate in one direction.

  In the power steering device 31, when the steering handle 7 is rotated, the operation valve 31v is operated according to the rotation direction to change the oil passage, and the gerotor pump 31g causes the pressure oil corresponding to the rotation amount of the steering handle 7 to the steering cylinder 32. Supplied.

  The tank port 31T of the power steering device 31 is opened to the tank T, and the oil pushed out from the steering cylinder 32 is discharged to the tank T through the tank port 31T.

  The pressure oil from the sub pump P2 is branched and supplied to the PTO clutch 27 and the HST 60, and the oil path to the HST 60 is an oil path d1 that supplies hydraulic oil to the hydraulic servo 60s for driving the trunnion shaft of the HST 60, A further branch is made to an oil passage d2 to the charge circuit for replenishing hydraulic oil to the circuit.

  An openable / closable proportional control valve 104 is arranged upstream of an oil passage c for supplying hydraulic oil to the PTO clutch 27, and the flow rate to the PTO clutch 27 is freely adjusted.

  A hydraulic servo drive valve 60v for freely moving the hydraulic servo 60s by changing or blocking the oil path to the hydraulic servo 60s is disposed in the oil passage d1 for supplying hydraulic oil to the hydraulic servo 60s.

  Further, a charge oil filter OF2, an oil cooler OC, and a second pressure control valve 103 are arranged upstream of an oil passage d2 for replenishing pressure oil to the charge circuit 60c of the HST 60, and if the pressure in the oil passage d2 becomes too high. The third pressure control valve 105 discharges the oil passage d3 opened to the tank T.

  Since the tractor as a work vehicle in the present invention can open the tank port of the power steering device 31 to the tank T, the back pressure of the power steering device 31 does not increase, and the steering handle 7 has an operational feeling and steering performance. Stable in good condition.

  Furthermore, since it is not necessary to arrange a pressure reducing valve necessary for back pressure suppression upstream of the circuit, a sufficient flow rate can always be ensured in the entire circuit. In particular, in the conventional configuration in which pressure oil is supplied to the entire circuit with a single pump, the power steering device 31 must be disposed upstream of the hydraulic servo 60s of the HST 60. The problem that the flow rate is not stable has occurred, but this problem is solved by the present invention.

  In addition, the second pressure control valve 103 is arranged at a position branched and supplied from the sub pump P2 upstream of the oil passage d2 for supplying pressure oil to the charge circuit 60c of the HST 60, thereby ensuring an appropriate pressure in the hydraulic PTO cylinder 27. can do. Particularly, when the HST 60 vibrates in response to driving from the HST pump 60p engine 5, the vibration is transmitted to the hydraulic servo 60s mechanically connected to the HST pump 60p, and the oil passage d1 may pulsate due to the vibration. There is an abnormal pressure applied to the PTO clutch 27 due to this pulsation, and the PTO clutch 27 may be damaged, but this can be suppressed by the second pressure control valve 103.

  Further, when it is not necessary to drive the hydraulic servo 60s of the PTO clutch 27 and HST 60, a sufficient flow rate can be supplied to the charge circuit 60c by closing the proportional control valve 104 and the hydraulic servo drive valve 60v.

  In the above embodiment, the throttle valve or the like is not arranged in the oil passage d1 for sending pressure oil to the hydraulic servo 60s, but the variable throttle valve 106 is arranged here as shown in FIG. As a configuration for changing the throttle diameter in response to a user's operation, a configuration in which the pump flow rate of the entire circuit is suppressed may be employed.

  Further, as a configuration for suppressing the pulsation of the oil passage d1 that sends pressure oil to the hydraulic servo 60s by the HST pump 60p, a bypass oil passage d4 that connects the oil passage d1 and the oil passage d2 that supplies pressure oil to the charge circuit 60c of the HST 60 is provided. A diaphragm 107 may be provided here.

  As other methods for suppressing the pulsation of the oil passage d1, a check valve may be provided in the oil passage d1, a plurality of throttles may be provided, or a choke may be used instead of the throttle. Furthermore, the oil passage diameter of the oil passage d1 may be increased, or the oil passage d1 may be configured by a flexible hose.

  Further, as a configuration for preventing damage to the oil cooler OC at low temperature start, the oil passage d5 on the tank port side of the oil cooler pressure control valve 108 is returned to the oil passage d6 between the first oil filter OF1 and the main pump P1 or the sub pump P2. It is good also as a structure.

27 PTO clutch 31 Power steering device 60 HST (hydrostatic continuously variable transmission)
60s Hydraulic servo 60c Charge circuit 102 Diverging valve (Flow control valve)
103 Second pressure control valve (pressure control valve)
104 Proportional control valve (control valve)
P1 Main pump P2 Sub pump

Claims (4)

  It has a hydraulic continuously variable transmission and a power steering device, and has a main pump and a sub pump that supply hydraulic oil to the hydraulic circuit. The hydraulic power is supplied from the main pump to the power steering device, and the hydraulic servo of the hydraulic continuously variable transmission And a hydraulic vehicle in which hydraulic oil is branched and supplied from a sub-pump to the charge circuit of the hydraulic continuously variable transmission, and a pressure control valve is arranged upstream of the charge circuit of the hydraulic continuously variable transmission.   It has a PTO clutch that operates hydraulically, and a pressure control valve is disposed upstream of an oil passage that supplies pressure oil to the PTO clutch from a sub-pump and supplies pressure oil to the charge circuit of the hydraulic continuously variable transmission. The work vehicle according to claim 1.   A control valve for opening and closing the flow path to the PTO clutch is provided in the oil passage for supplying hydraulic oil to the PTO clutch so that the hydraulic servo control valve for controlling the hydraulic servo of the hydraulic continuously variable transmission can be opened and closed. The work vehicle according to claim 2 provided.   The work vehicle according to any one of claims 1 to 3, wherein a flow control valve is disposed upstream of the power steering device, and a tank port of the power steering device is opened to the tank.

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