Work vehicle and drive unit for work vehicle

Abstract

To reduce power consumption.SOLUTION: The work vehicle comprises a drive wheel, an electric motor, a first clutch, a second clutch, a first shifting unit, a second shifting unit, a first hydraulic chamber, and a biasing member. The electric motor is configured to drive the drive wheel. The first clutch includes a first piston and a plurality of first clutch discs. The second clutch includes a second piston and a plurality of second clutch discs. The first shifting unit receives power from the electric motor via the first clutch. The second shifting unit receives power from the electric motor via the second clutch. The first hydraulic chamber is supplied with hydraulic pressure for moving the first piston toward the first clutch disc. The biasing member biases the second piston toward the second clutch disc.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a work vehicle and a drive unit for a work vehicle. [Background technology]

[0002] Electric forklifts are widely used indoors in factories, warehouses, etc., because they do not emit exhaust gases and are quiet. Electric forklifts are driven by an electric motor, which drives the drive wheels to move the forklift.

[0003] Patent Document 1 proposes an electric forklift equipped with a transmission. By installing a transmission in this way, it is possible to increase the driving force of the electric motor and increase the speed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-139830 Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, there is a demand for reducing power consumption in electric forklifts having a transmission. Therefore, an object of the present invention is to provide a work vehicle that can reduce power consumption. [Means for solving the problem]

[0006] A work vehicle according to a first aspect includes drive wheels, an electric motor, a first clutch, a second clutch, a first transmission unit, a second transmission unit, a first hydraulic chamber, and a biasing member. The electric motor is configured to drive the drive wheels. The first clutch has a first piston and a plurality of first clutch discs. The second clutch has a second piston and a plurality of second clutch discs. The first transmission unit receives power from the electric motor via the first clutch. The second transmission unit receives power from the electric motor via the second clutch. The first hydraulic chamber is supplied with hydraulic pressure to move the first piston toward the first clutch disc. The biasing member biases the second piston toward the second clutch disc.

[0007] With this configuration, hydraulic pressure is used when the first clutch is engaged to transmit power via the first transmission unit, but hydraulic pressure is not used when the second clutch is engaged to transmit power via the second transmission unit because the biasing force of the biasing member is used. This reduces the need for an electric motor to drive an oil pump to supply hydraulic pressure, thereby reducing power consumption.

[0008] A work vehicle according to a second aspect is the work vehicle according to the first aspect, and is configured as follows: The biasing member is a spring.

[0009] A work vehicle according to a third aspect is the work vehicle according to the second aspect, and is configured as follows: The first clutch has a cylindrical first clutch outer. Each first clutch disc is disposed within the first clutch outer. The second clutch has a cylindrical second clutch outer. Each second clutch disc is disposed within the second clutch outer. The spring is disposed radially outward from the first clutch outer and the second clutch outer.

[0010] A work vehicle according to a fourth aspect is the work vehicle according to the third aspect, and is configured as follows: The second piston has a first protrusion. The first protrusion is a biasing member that protrudes radially outward from the second clutch outer and biases the second piston via the first protrusion.

[0011] A work vehicle according to a fifth aspect is the work vehicle according to the fourth aspect, and is configured as follows: The first clutch outer has a second protruding portion. The second protruding portion protrudes radially outward. The biasing member has a first end and a second end. The first end is supported by the first protruding portion. The second end is supported by the second protruding portion.

[0012] A work vehicle according to a sixth aspect is the work vehicle according to the fifth aspect, and is configured as follows: The first clutch has a pressure-receiving member. The pressure-receiving member is configured to cooperate with the first piston to sandwich each of the first clutch discs. The second protrusion overlaps with the pressure-receiving member when viewed in the radial direction.

[0013] A work vehicle according to a seventh aspect is the work vehicle according to any one of the third to fifth aspects, further comprising a hydraulic balance chamber. The hydraulic balance chamber is defined by the second clutch outer and the second piston. The hydraulic balance chamber is filled with hydraulic oil.

[0014] A work vehicle according to an eighth aspect is the work vehicle according to any one of the first to seventh aspects, further comprising a second hydraulic chamber. The second hydraulic chamber is supplied with hydraulic pressure for moving the second piston away from the second clutch disc.

[0015] A work vehicle according to a ninth aspect is the work vehicle according to the eighth aspect, further comprising a wall member. The second piston has a pressure portion and a piston portion. The pressure portion is configured to press the second clutch disc. The piston portion is disposed axially spaced apart from the pressure portion. The wall member is disposed so as to be movable relative to the piston portion. The wall member cooperates with the piston portion to define a second hydraulic chamber.

[0016] A drive unit according to a tenth aspect is a drive unit for a work vehicle. The drive unit includes an electric motor, a first clutch, a second clutch, a first transmission unit, a second transmission unit, a first hydraulic chamber, and a biasing member. The first clutch has a first piston and a plurality of first clutch discs. The second clutch has a second piston and a plurality of second clutch discs. The first transmission unit receives power from the electric motor via the first clutch. The second transmission unit receives power from the electric motor via the second clutch. The first hydraulic chamber is supplied with hydraulic pressure for moving the first piston toward the first clutch disc. The biasing member biases the second piston toward the second clutch disc. [Effects of the Invention]

[0017] According to the present invention, it is possible to reduce power consumption in a work vehicle. [Brief explanation of the drawings]

[0018] [Figure 1] Side view of a forklift. [Figure 2] Schematic diagram of a drive unit. [Figure 3] FIG. 4 is a cross-sectional view of the transmission when the first clutch is in a clutch-on state. [Figure 4] FIG. 4 is a cross-sectional view of the transmission when the second clutch is in a clutch-on state. [Figure 5] FIG. 4 is a cross-sectional view of a second piston and a second clutch outer as viewed in the axial direction. DETAILED DESCRIPTION OF THE INVENTION

[0019] A drive unit for a work vehicle according to this embodiment and a work vehicle equipped with the same will be described below with reference to the drawings. A forklift will be described below as an example of the work vehicle. The work vehicle is not limited to a forklift, and may be, for example, a towing tractor or a rough terrain crane.

[0020] In the following description, the axial direction refers to the direction in which the rotation axis O of the first clutch 6 and the second clutch 7 extends. The circumferential direction refers to the circumferential direction of a circle centered on the rotation axis O, and the radial direction refers to the radial direction of a circle centered on the rotation axis O. Furthermore, the first axial side refers to the right side in FIG. 2, and the second axial side refers to the left side in FIG. 2. Furthermore, "front" and "rear" refer to the front and rear of the vehicle body 101. In other words, the left in FIG. 1 is the front, and the right is the rear.

[0021] [forklift] Fig. 1 is a side view of a forklift. As shown in Fig. 1, the forklift 100 has a vehicle body 101, a lift device 102, a pair of drive wheels 103, and a drive unit 10. The forklift 100 also has a pair of driven wheels 104, a seat 105, an operation unit 106, and the like. In this embodiment, the front wheels are the drive wheels 103, and the rear wheels are the driven wheels 104.

[0022] The forklift 100 is an electric forklift that uses an electric motor 2 as a drive source. The forklift 100 does not have an internal combustion engine. The forklift 100 uses a battery (not shown) as a power source.

[0023] The forklift 100 can load and unload cargo using a lift device 102. The lift device 102 is disposed in front of and attached to a vehicle body 101. The drive wheels 103 are attached to the front of the vehicle body 101. The driven wheels 104 are attached to the rear of the vehicle body 101.

[0024] [Drive unit] The drive unit 10 is configured to be mounted on a forklift. The drive unit 10 is disposed inside a vehicle body 101. The drive unit 10 is disposed at the front of the vehicle body 101. The drive unit 10 is configured to drive drive wheels 103.

[0025] Fig. 2 is a schematic diagram of the drive unit. As shown in Fig. 2, the drive unit 10 is configured to rotate and drive drive wheels 103. In detail, the drive unit 10 outputs drive force to the pair of drive wheels 103 via a differential gear 107. The drive unit 10 has an electric motor 2 and a transmission 3.

[0026] [Electric motor] The electric motor 2 is configured to rotate and drive the drive wheels 103. The electric motor 2 is driven by power supplied from a battery. The electric motor 2 has a rotor (not shown) and a stator (not shown). The stator is non-rotatable together with the motor case. The rotor is rotatably arranged.

[0027] [Gearbox] Fig. 3 is a cross-sectional view of the transmission 3 when the first clutch 6 is in the clutch-on state, and Fig. 4 is a cross-sectional view of the transmission 3 when the second clutch 7 is in the clutch-on state. As shown in Figs. 2 to 4, the transmission 3 is configured to change the rotational speed of the electric motor 2 at a variable gear ratio. For example, the transmission 3 is a manual transmission. However, the transmission 3 may also be an automatic transmission.

[0028] The transmission 3 has a two-stage gear train. That is, the transmission 3 has a first gear train 4 (an example of a first transmission section) and a second gear train 5 (an example of a second transmission section). The transmission 3 also has a first clutch 6, a second clutch 7, a first hydraulic chamber 8, a second hydraulic chamber 9, a hydraulic balance chamber 11, a first biasing member 12 (an example of a biasing member), and a wall member 13.

[0029] <First and second gear trains> The first gear train 4 receives power from the electric motor 2 via a first clutch 6. The second gear train 5 receives power from the electric motor 2 via a second clutch 7. The first gear train 4 is arranged on a first side in the axial direction relative to the second gear train 5. The first gear train 4 has a larger gear ratio than the second gear train 5.

[0030] Each of the first gear train 4 and the second gear train 5 has a plurality of gears (for example, a pair of gears). Specifically, the first gear train 4 has a first drive gear 4a and a first driven gear 4b. The first drive gear 4a and the first driven gear 4b mesh with each other. Furthermore, the second gear train 5 has a second drive gear 5a and a second driven gear 5b. The second drive gear 5a and the second driven gear 5b mesh with each other.

[0031] The first drive gear 4a has a smaller diameter than the second drive gear 5a. The first driven gear 4b has a larger diameter than the second driven gear 5b. The first drive gear 4a has a first gear body portion 41a and a first engagement portion 42a. The first engagement portion 42a extends from the first gear body portion 41a toward a second side in the axial direction. The outer peripheral surface of the first engagement portion 42a is configured to engage with a first driven plate 632, which will be described later.

[0032] The second drive gear 5a has a second gear body 51a and a second engagement portion 52a. The second engagement portion 52a is cylindrical. The second engagement portion 52a extends from the second gear body 51a toward a first side in the axial direction. The outer peripheral surface of the second engagement portion 52a is configured to engage with a second driven plate 732, which will be described later.

[0033] The transmission 3 transmits power from the electric motor 2 to the drive wheels 103 via either the first gear train 4 or the second gear train 5. In this way, the transmission 3 can select either the first gear train 4 or the second gear train 5, so the gear ratio is variable.

[0034] The transmission 3 has an input shaft 15 and an output shaft 16. The input shaft 15 and the output shaft 16 extend in the axial direction. First and second drive gears 4a, 5a are attached to the input shaft 15. The first and second drive gears 4a, 5a are rotatable relative to the input shaft 15. First and second driven gears 4b, 5b are attached to the output shaft 16. The first and second driven gears 4b, 5b rotate integrally with the output shaft 16.

[0035] <First and second clutches> As shown in Fig. 3, the first clutch 6 and the second clutch 7 are supported on the input shaft 15. The first clutch 6 and the second clutch 7 are configured to switch the power transmission path between the first gear train 4 and the second gear train 5. The first clutch 6 and the second clutch 7 may be wet multi-plate clutches.

[0036] The first clutch 6 is disposed on a first axial side relative to the second clutch 7. The first clutch 6 has a first clutch outer 61, a first piston 62, a plurality of first clutch discs 63, and a first pressure-receiving member 64 (an example of a pressure-receiving member).

[0037] The first clutch outer 61 is cylindrical. The first clutch outer 61 is configured to rotate integrally with the input shaft 15. In detail, the first clutch outer 61 has a first circular plate portion 611, a first cylindrical portion 612, and a second protruding portion 613. The first circular plate portion 611, the first cylindrical portion 612, and the second protruding portion 613 are integrally configured by a single member.

[0038] The first circular plate portion 611 extends radially outward from the input shaft 15. The first circular plate portion 611 is configured to rotate integrally with the input shaft 15. Note that although the first circular plate portion 611 is configured integrally with the input shaft 15 by a single member, it may also be a member separate from the input shaft 15.

[0039] The first cylindrical portion 612 extends from the outer peripheral end of the first circular plate portion 611 to a first side in the axial direction. The first cylindrical portion 612 has a plurality of grooves 614 extending in the axial direction. Each groove 614 is formed on the inner peripheral surface of the first cylindrical portion 612. Each groove 614 does not penetrate the first cylindrical portion 612.

[0040] The second protruding portion 613 protrudes radially outward from the first cylindrical portion 612. The second protruding portion 613 has an annular shape extending in the circumferential direction. The second protruding portion 613 is disposed so as to overlap with the first pressure-receiving member 64 when viewed in the radial direction.

[0041] The first piston 62 is disposed within the first clutch outer 61. The first piston 62 is disposed so as to be movable in the axial direction. The first piston 62 is configured to press the first clutch disc 63. The first piston 62 slides on the input shaft 15. The first piston 62 is biased toward a second side in the axial direction by a second biasing member 65. The second biasing member is, for example, a compression coil spring.

[0042] The multiple first clutch discs 63 are arranged axially between the first piston 62 and the first pressure-receiving member 64. The multiple first clutch discs 63 are arranged inside the first clutch outer 61. The multiple first clutch discs 63 include a first drive plate 631 and a first driven plate 632.

[0043] The first drive plate 631 rotates integrally with the first clutch outer 61. More specifically, the first drive plate 631 engages with the groove portion 614 of the first clutch outer 61. Therefore, the first drive plate 631 is engaged with the first clutch outer 61 so as to be movable in the axial direction but not rotatable.

[0044] The first driven plate 632 rotates integrally with the first drive gear 4a of the first gear train 4. More specifically, the first driven plate 632 engages with the first engagement portion 42a. The first driven plate 632 engages with the first engagement portion 42a so as to be non-rotatable but axially movable.

[0045] The first pressure-receiving member 64 is configured to cooperate with the first piston 62 to sandwich each of the first clutch discs 63 in the axial direction. The first pressure-receiving member 64 is attached to the first clutch outer 61 so as to be unable to rotate. The first pressure-receiving member 64 is arranged so as to be unable to move on the first side in the axial direction.

[0046] By placing the first clutch 6 in a clutch-on state, power is transmitted via the first gear train 4. More specifically, the first clutch 6 is placed in a clutch-on state by moving the first piston 62 toward the first clutch disc 63 and sandwiching the first clutch disc 63 between the first piston 62 and the first pressure-receiving member 64. When the first clutch 6 is placed in the clutch-on state, the first drive gear 4a rotates integrally with the input shaft 15. As a result, power from the input shaft 15 is transmitted to the output shaft 16 via the first gear train 4. The first clutch 6 is configured to transmit power to the first gear train 4 or interrupt the power transmission.

[0047] As shown in FIG. 4, the second clutch 7 has a second clutch outer 71, a second piston 72, a plurality of second clutch discs 73, and a second pressure-receiving member 74.

[0048] The second clutch outer 71 is cylindrical. The second clutch outer 71 is configured to rotate integrally with the input shaft 15. In detail, the second clutch outer 71 has a second disc portion 711 and a second cylindrical portion 712. The second disc portion 711 and the second cylindrical portion 712 are integrally configured by a single member.

[0049] The second circular plate portion 711 extends radially outward from the input shaft 15. The second circular plate portion 711 is configured to rotate integrally with the input shaft 15. Note that although the second circular plate portion 711 is configured integrally with the input shaft 15 by a single member, it may also be a member separate from the input shaft 15.

[0050] The second cylindrical portion 712 extends from the outer peripheral end of the second disc portion 711 to a second side in the axial direction. The second cylindrical portion 712 has a plurality of slits 713 extending in the axial direction. Each slit 713 penetrates the second cylindrical portion 712 in the radial direction. The slits 713 are arranged at intervals in the circumferential direction (see FIG. 5). Each slit 713 opens to the second side in the axial direction. Note that FIG. 5 is a cross-sectional view of the second piston 72 and the second clutch outer 71 as viewed in the axial direction.

[0051] The second piston 72 is disposed within the second clutch outer 71, excluding a first protruding portion 723, which will be described later. The second piston 72 is disposed so as to be movable in the axial direction. The second piston 72 is configured to press against the second clutch disc 73. The second piston 72 slides on the input shaft 15. The second piston 72 is configured to rotate integrally with the second clutch outer 71.

[0052] The second piston 72 has a pressure portion 721, a piston portion 722, and a plurality of first protrusions 723. The pressure portion 721 is annular and extends in the circumferential direction. The pressure portion 721 is disposed so as to face the second clutch disc 73. The pressure portion 721 is configured to press the second clutch disc 73. The pressure portion 721 is movable in the axial direction relative to the second clutch outer 71.

[0053] The piston portion 722 is arranged so as to be able to move in the axial direction inside the second clutch outer 71. The piston portion 722 airtightly divides the inside of the second clutch outer 71. In detail, the piston portion 722 divides the inside of the second clutch outer 71 into a second hydraulic chamber 9 and a hydraulic balance chamber 11.

[0054] The piston portion 722 is configured to move in the axial direction integrally with the pressure portion 721. Note that the piston portion 722 and the pressure portion 721 may move separately in the axial direction toward the first side.

[0055] The piston portion 722 is disposed at an interval in the axial direction from the pressure portion 721. In particular, the piston portion 722 is in contact with the pressure portion 721 at its outer periphery, while the portion other than the outer periphery is disposed at an interval in the axial direction from the pressure portion 721. In other words, the outer periphery of the piston portion 722 is disposed on the second axial side with respect to the portion other than the outer periphery.

[0056] The first protruding portion 723 protrudes radially outward from the second clutch outer 71. That is, the first protruding portion 723 is a portion of the second piston 72 that protrudes radially outward from the second clutch outer 71. In this embodiment, the first protruding portion 723 is formed by a part of the pressure portion 721 and a part of the piston portion 722.

[0057] 5, the first protrusions 723 are spaced apart from one another in the circumferential direction. The first protrusions 723 are engaged with the slits 713. Therefore, the second piston 72 rotates integrally with the second clutch outer 71. The first protrusions 723 protrude radially outward through the slits 713.

[0058] As shown in Fig. 4, the wall member 13 is disk-shaped. The wall member 13 cooperates with the piston portion 722 to define the second hydraulic chamber 9. The wall member 13 is disposed at an interval from the piston portion 722 in the axial direction. The wall member 13 is disposed between the piston portion 722 and the pressure portion 721 in the axial direction. The wall member 13 is disposed so as to be movable relative to the piston portion 722. In detail, the movement of the wall member 13 toward the second side in the axial direction is restricted by a stopper ring or the like.

[0059] The plurality of second clutch discs 73 are arranged axially between the second piston 72 and the second pressure-receiving member 74. The plurality of second clutch discs 73 are arranged inside the second clutch outer 71. The plurality of second clutch discs 73 include a second drive plate 731 and a second driven plate 732.

[0060] The second drive plate 731 rotates integrally with the second clutch outer 71. More specifically, the second drive plate 731 engages with each slit 713 of the second clutch outer 71. Therefore, the second drive plate 731 is engaged with the second clutch outer 71 so as to be movable in the axial direction but not rotatable.

[0061] The second driven plate 732 rotates integrally with the second drive gear 5a of the second gear train 5. More specifically, the second driven plate 732 engages with the second engagement portion 52a. The second driven plate 732 engages with the second engagement portion 52a so as to be non-rotatable but axially movable.

[0062] The second pressure-receiving member 74 is configured to cooperate with the second piston 72 (more specifically, the pressure portion 721) to sandwich each second clutch disc 73 in the axial direction. The second pressure-receiving member 74 is attached to the second clutch outer 71 so as to be unable to rotate. The second pressure-receiving member 74 is arranged so as to be unable to move on the second axial side.

[0063] By placing the second clutch 7 in a clutch-on state, power is transmitted via the second gear train 5. More specifically, the second clutch 7 is placed in a clutch-on state by moving the second piston 72 toward the second clutch disc 73 and sandwiching the second clutch disc 73 between the second piston 72 and the second pressure-receiving member 74. By placing the second clutch 7 in a clutch-on state, the second drive gear 5a rotates integrally with the input shaft 15. As a result, power from the input shaft 15 is transmitted to the output shaft 16 via the second gear train 5. The second clutch 7 is configured to transmit power to the second gear train 5 or interrupt the power transmission.

[0064] <1st Hydraulic Chamber> As shown in Fig. 3, the first hydraulic chamber 8 is defined by the first clutch outer 61 and the first piston 62. The first hydraulic chamber 8 is supplied with hydraulic pressure for moving the first piston 62 toward the first clutch disc 63. The first hydraulic chamber 8 is supplied with hydraulic oil via a first supply path 81. The oil pump for supplying hydraulic pressure to the first hydraulic chamber 8 is driven by the electric motor 2 or another electric motor (not shown).

[0065] When hydraulic pressure is supplied to the first hydraulic chamber 8, the first piston 62 moves to the first side in the axial direction against the biasing force of the second biasing member 65. As a result, the first clutch 6 is brought into the clutch-on state, and power is transmitted via the first gear train 4. In this way, the first clutch 6 is brought into the clutch-on state by the hydraulic pressure. On the other hand, when the supply of hydraulic pressure to the first hydraulic chamber 8 is stopped, the first clutch 6 is brought into the clutch-off state. The first piston 62 moves to the second side in the axial direction by the biasing force of the second biasing member 65.

[0066] <Second hydraulic chamber> As shown in FIG. 4, the second hydraulic chamber 9 is defined by the second piston 72 and the wall member 13. The second hydraulic chamber 9 is supplied with hydraulic pressure for moving the second piston 72 away from the second clutch disc 73. The second hydraulic chamber 9 is supplied with hydraulic oil via a second supply path 91. The oil pump for supplying hydraulic pressure to the second hydraulic chamber 9 is driven by the electric motor 2 or another electric motor (not shown). This oil pump can also be used as the oil pump for supplying hydraulic pressure to the first hydraulic chamber 8. When hydraulic oil is supplied to the second hydraulic chamber 9, hydraulic oil is also supplied to the first hydraulic chamber 8.

[0067] When hydraulic pressure is supplied to the second hydraulic chamber 9, the second piston 72 moves axially toward the first side against the biasing force of the first biasing member 12. As a result, the second clutch 7 enters the clutch-off state. That is, power transmission via the second gear train 5 is interrupted.

[0068] <Hydraulic balance chamber> The hydraulic balance chamber 11 is filled with hydraulic oil. The hydraulic balance chamber 11 is defined by the second clutch outer 71 and the second piston 72 (more specifically, the piston portion 722). Hydraulic oil is supplied to and discharged from the hydraulic balance chamber 11 via an oil passage 111.

[0069] <First biasing member> The first biasing member 12 biases the second piston 72 toward the second clutch disc 73. The first biasing member 12 is, for example, a spring. More specifically, the first biasing member 12 is a coil spring. The first biasing member 12 extends in the axial direction. The first biasing member 12 is disposed in a compressed state.

[0070] The first biasing member 12 is disposed radially outward from the first clutch outer 61 and the second clutch outer 71. In other words, the first biasing member 12 is disposed so as to surround the first clutch outer 61 and the second clutch outer 71.

[0071] The first biasing member 12 has a first end 121 and a second end 122 in the axial direction. The first end 121 is supported by the first protruding portion 723. The second end 122 is supported by the second protruding portion 613. Therefore, the first biasing member 12 biases the second piston 72 toward the second side in the axial direction via the first protruding portion 723.

[0072] The second clutch 7 is brought into a clutch-on state when the second piston 72 moves to the second side in the axial direction due to the biasing force of the first biasing member 12. As a result, power is transmitted via the second gear train 5. In this way, the second clutch 7 is brought into a clutch-on state not by hydraulic pressure but by the biasing force of the first biasing member 12. On the other hand, when hydraulic pressure is supplied to the second hydraulic chamber 9, the second piston 72 moves to the first side in the axial direction against the biasing force of the first biasing member 12, and the second clutch 7 is brought into a clutch-off state.

[0073] <How it works> First, in situations where high torque is required, such as when starting or traveling uphill, hydraulic pressure is supplied to the first hydraulic chamber 8 and the second hydraulic chamber 9. This causes the first clutch 6 to enter a clutch-on state and the second clutch 7 to enter a clutch-off state. As a result, power is transmitted via the first gear train 4.

[0074] In situations where high torque is not required, such as during normal driving, the supply of hydraulic pressure to the first hydraulic chamber 8 and the second hydraulic chamber 9 is stopped. This causes the first clutch 6 to enter a clutch-off state and the second clutch 7 to enter a clutch-on state. As a result, power is transmitted via the second gear train 5.

[0075] In this way, the oil pump for supplying hydraulic pressure can be stopped when power is transmitted via the second gear train 5. As a result, power consumption can be reduced.

[0076] [Variations] Although the embodiments of the present invention have been described above, the present invention is not limited to these, and various modifications are possible without departing from the spirit of the present invention. Note that the following modifications can basically be applied simultaneously.

[0077] (a) In the above embodiment, the gear ratio of the first gear train 4 is greater than the gear ratio of the second gear train 5, but the gear ratio of the first gear train 4 may be smaller than the gear ratio of the second gear train 5. In other words, when starting or traveling uphill, the second clutch 7 may be in a clutch-on state and power may be transmitted via the second gear train 5, and during normal traveling, the first clutch 6 may be in a clutch-on state and power may be transmitted via the first gear train 4.

[0078] (b) In the above embodiment, the first transmission unit is configured by a gear train, but the first transmission unit may be configured by something other than a gear train. For example, the first transmission unit may be configured by a pair of pulleys and a belt. The same applies to the second transmission unit.

[0079] (c) A reducer may be provided between the electric motor 2 and the transmission 3. Also, a reducer may be provided between the transmission 3 and the drive wheels 103.

[0080] (d) In the above embodiment, the first protruding portion 723 is configured by a part of the pressure portion 721 and a part of the piston portion 722, but the configuration of the first protruding portion 723 is not limited to this. For example, the first protruding portion 723 may be configured by only a part of the pressure portion 721, or by only a part of the piston portion 722. Note that when the first protruding portion 723 is configured by only a part of the pressure portion 721, it is preferable that the pressure portion 721 is configured to move integrally with the piston portion 722 toward the first axial side.

[0081] (e) The first biasing member 12 does not have to be a spring as long as it biases the second piston 72 by means other than hydraulic pressure. For example, the first biasing member 12 may be a cam mechanism or the like. The mechanism may be one in which the rotation of a cam of the cam mechanism biases the second piston 72 toward the second side in the axial direction, thereby moving the second piston 72 toward the second side in the axial direction. [Explanation of symbols]

[0082] 2: Electric motor 4: First gear train 5: Second gear train 6: First clutch 61: First clutch outer 613:Second protrusion 62: First piston 63: First clutch disc 7: Second clutch 71: Second clutch outer 72: Second piston 721: Pressure section 722: Piston part 723: 1st protrusion 73: Second clutch disc 8: First hydraulic chamber 9: Second hydraulic chamber 10: Drive unit 11: Hydraulic balance chamber 12: First biasing member 121: First end 122: Second end 13:Wall parts 100: Forklift 103: Drive wheel

Claims

1. Drive wheels and an electric motor configured to drive the drive wheels; a first clutch having a first piston and a plurality of first clutch discs; a second clutch having a second piston and a plurality of second clutch discs; a first transmission unit that receives power from the electric motor via the first clutch; a second transmission unit that receives power from the electric motor via the second clutch; a first hydraulic chamber to which hydraulic pressure is supplied for moving the first piston toward the first clutch disc; a biasing member that biases the second piston toward the second clutch disc; A work vehicle equipped with:

2. The biasing member is a spring. The work vehicle according to claim 1 .

3. The first clutch has a cylindrical first clutch outer, Each of the first clutch discs is disposed within the first clutch outer, The second clutch has a cylindrical second clutch outer, Each of the second clutch discs is disposed within the second clutch outer, The biasing member is disposed radially outward relative to the first clutch outer and the second clutch outer. The work vehicle according to claim 2 .

4. the second piston has a first protruding portion that protrudes radially outward from the second clutch outer, The biasing member biases the second piston via the first protrusion. The work vehicle according to claim 3 .

5. the first clutch outer has a second protruding portion that protrudes radially outward, The biasing member has a first end supported by the first protrusion and a second end supported by the second protrusion. The work vehicle according to claim 4.

6. the first clutch has a pressure-receiving member configured to cooperate with the first piston to sandwich the first clutch discs, The second protruding portion overlaps with the pressure-receiving member when viewed in a radial direction. The work vehicle according to claim 5.

7. a hydraulic balance chamber defined by the second clutch outer and the second piston and filled with hydraulic oil; The work vehicle according to claim 3 .

8. a second hydraulic chamber to which hydraulic pressure is supplied for moving the second piston away from the second clutch disc; The work vehicle according to claim 1 .

9. Further comprising a wall member; The second piston is a pressure portion configured to press the second clutch disc; a piston portion disposed axially apart from the pressure portion; and the wall member is disposed so as to be movable relative to the piston portion, and defines the second hydraulic chamber in cooperation with the piston portion; The work vehicle according to claim 8.

10. A drive unit for a work vehicle, an electric motor; a first clutch having a first piston and a plurality of first clutch discs; a second clutch having a second piston and a plurality of second clutch discs; a first transmission unit that receives power from the electric motor via the first clutch; a second transmission unit that receives power from the electric motor via the second clutch; a first hydraulic chamber to which hydraulic pressure is supplied for moving the first piston toward the first clutch disc; a biasing member that biases the second piston toward the second clutch disc; A drive unit comprising:

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