Rice transplanter

Abstract

To provide a rice transplanter capable of reducing an increase in the pressure of hydraulic oil in an oil passage of a continuously variable transmission.SOLUTION: This rice transplanter is equipped with a seedling planting device for planting seedlings on a paddy field surface, and a hydrostatic continuously variable transmission 45 having a hydraulic pump to which power from an engine is transmitted and a hydraulic motor for outputting power, and the continuously variable transmission 45 has a high pressure side oil passage for supplying pressure oil from the hydraulic pump to the hydraulic motor, and a low pressure side oil passage for supplying pressure oil from the hydraulic motor to the hydraulic pump, and is equipped with a pressure reducing part 75 connected to the high pressure side oil passage and reducing pressure of pressure oil supplied to the hydraulic motor.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a rice transplanter. [Background technology]

[0002] As a conventional rice transplanter, for example, as described in Patent Document 1, there is one in which power from an engine is transmitted to a seedling planting device through a row spacing transmission (called a continuously variable transmission in Patent Document 1). By operating the row spacing transmission, the row spacing by the seedling planting device can be set to a desired spacing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-060340 Summary of the Invention [Problem to be solved by the invention]

[0004] In some of such rice transplanters, as described in Patent Document 1, a hydrostatic continuously variable transmission is used as the inter-row transmission.

[0005] A hydrostatic continuously variable transmission includes a hydraulic pump to which power from an engine is transmitted, a hydraulic motor that outputs the power, an oil passage that supplies pressurized oil from the hydraulic pump to the hydraulic motor, and an oil passage that supplies pressurized oil from the hydraulic motor to the hydraulic pump.

[0006] In conventional hydrostatic continuously variable transmissions, the pressure of the hydraulic oil in the oil passages can increase as the workload of the seedling planting device increases, causing pulsation in the oil passages and resulting in the problem of abnormal noise.

[0007] Therefore, an object of the present invention is to provide a rice transplanter that can reduce the increase in pressure of hydraulic oil in the oil passages of a continuously variable transmission. [Means for solving the problem]

[0008] The rice transplanter of the present invention is equipped with a seedling planting device that plants seedlings in the surface of a rice paddy, and a hydrostatic continuously variable transmission having a hydraulic pump to which power from an engine is transmitted and a hydraulic motor that outputs power, and the continuously variable transmission has a high-pressure side oil passage that supplies pressurized oil from the hydraulic pump to the hydraulic motor, and a low-pressure side oil passage that supplies pressurized oil from the hydraulic motor to the hydraulic pump, and is equipped with a pressure reducing section that is connected to the high-pressure side oil passage and reduces the pressure of the pressurized oil supplied to the hydraulic motor.

[0009] According to this invention, the pressure reducing section is provided in the high-pressure oil passage of the continuously variable transmission, in which the pressure of the hydraulic oil increases when the load on the continuously variable transmission increases. With this configuration, the pressure reducing section reduces the pressure of the hydraulic oil in the high-pressure oil passage, making it possible to reduce the pressure of the hydraulic oil in the high-pressure oil passage from increasing.

[0010] In the present invention, it is preferable that the pressure reducing section has a relief valve.

[0011] With this configuration, the pressure of the hydraulic oil in the high-pressure oil passage is set by the relief valve, and when the pressure exceeds the set value, the relief valve opens, thereby reducing the pressure of the hydraulic oil in the high-pressure oil passage. As a result, the pressure reducing unit can adjust the pressure of the hydraulic oil in the high-pressure oil passage to an appropriate pressure by selecting a relief valve with an appropriate set value at the time of design.

[0012] In the present invention, it is preferable that the relief valve is connected to the high-pressure side oil passage and the low-pressure side oil passage.

[0013] With this configuration, when the pressure of the hydraulic oil in the high-pressure oil passage exceeds a set value set by the relief valve, the hydraulic oil in the high-pressure oil passage flows to the low-pressure oil passage via the relief valve. As a result, it is only necessary to provide a relief valve in the oil passage connecting the high-pressure oil passage and the low-pressure oil passage, and it is possible to provide a pressure reducing unit in the continuously variable transmission with a simple design change.

[0014] In the present invention, the pressure reducing section has a first oil passage connecting the high-pressure side oil passage and the relief valve, and a second oil passage connecting the relief valve and the low-pressure side oil passage, and it is preferable that an orifice is provided in either the first oil passage or the second oil passage.

[0015] With this configuration, even if the pressure of the hydraulic oil in the high-pressure oil passage increases and the relief valve opens, the orifice can prevent a sudden drop in the pressure of the hydraulic oil in the high-pressure oil passage.

[0016] In the present invention, it is preferable that the orifice is provided in the first oil passage, and that the inner diameter of the orifice is smaller than the inner diameter of the first oil passage.

[0017] According to this configuration, an orifice is provided upstream of the relief valve in the oil passage, which makes it possible to reduce the oil pressure applied to the relief valve and extend the life of the relief valve.

[0018] In the present invention, it is preferable that the pressure reducing section has an accumulator that reduces the pressure of the pressure oil supplied to the hydraulic motor, and that the accumulator communicates with the high-pressure oil passage via an orifice.

[0019] With this configuration, the hydraulic oil in the high-pressure oil passage is supplied to the accumulator, thereby reducing the pressure of the hydraulic oil in the high-pressure oil passage. By simply providing an accumulator in the high-pressure oil passage, it is possible to provide a pressure reducing unit in the continuously variable transmission with a simple design change.

[0020] In the present invention, it is preferable that the continuously variable transmission is an inter-row transmission that changes the speed of power from the engine and transmits it to the seedling planting device.

[0021] With this configuration, even if the workload of the seedling planting device increases, it is possible to reduce the increase in pressure of the hydraulic oil in the high-pressure oil passage of the inter-row transmission. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is an overall side view of a riding rice transplanter. [Figure 2] FIG. 1 is an overall plan view of a riding rice transplanter. [Figure 3] FIG. [Figure 4] FIG. [Figure 5] FIG. 2 is a diagram illustrating a configuration of a pressure reducing unit. [Figure 6] FIG. 2 is a diagram showing a hydraulic circuit of an inter-section transmission and a pressure reducing section. [Figure 7] FIG. 2 is a side view showing the configuration of an inter-row transmission and a fan. DETAILED DESCRIPTION OF THE INVENTION

[0023] An embodiment of the present invention will be described with reference to the drawings. In the following description, unless otherwise specified, the direction of arrow F in the drawings will be referred to as "front," the direction of arrow B as "rear," the direction of arrow L as "left," and the direction of arrow R as "right." Furthermore, the direction of arrow U in the drawings will be referred to as "up," and the direction of arrow D as "down."

[0024] [Overall configuration of the rice transplanter] The riding rice transplanter (an example of a "rice transplanter") of this embodiment will be described below. As shown in Fig. 1, the riding rice transplanter is provided with a link mechanism 3 and a hydraulic cylinder 4 for driving the link mechanism 3 up and down at the rear of a machine body 11 having right and left front wheels 1 and right and left rear wheels 2, and a seedling planting device 5 for planting seedlings in the rice field surface is supported at the rear of the link mechanism 3.

[0025] The seedling planting device 5 comprises a planting transmission case 6 arranged at a predetermined interval in the left-right direction, a rotating case 7 rotatably supported on the right and left rear sides of the planting transmission case 6, a pair of planting arms 8 provided at both ends of the rotating case 7, a float 9, and a seedling tray 10.

[0026] [Configuration around the driving section] As shown in FIGS. 1 and 2, a body 11 is provided with a driver's seat 13 and a steering handle 14 for steering the front wheels 1.

[0027] Right and left support frames 16 are provided on the right and left front portions of the machine body 11, and spare seedling trays 15 are supported on the support frames 16. A support frame 17 is connected across the upper portions of the right and left support frames 16.

[0028] A measuring device 18 is attached to the support frame 17 at a portion located at the lateral center CL of the airframe 11 in a plan view. The measuring device 18 is equipped with a receiving device (not shown) that acquires position information using a satellite positioning system, and an inertial measurement unit (not shown) that detects the inclination (pitch angle, roll angle) of the airframe 11.

[0029] [Configuration around the transmission case] As shown in Figure 1, a transmission case 20 is supported at the front of the vehicle body 11, and right and left front wheels 1 are supported on front axle cases 21 connected to the right and left lateral sides of the transmission case 20. A rear axle case 22 is supported at the rear of the vehicle body 11, and right and left rear wheels 2 are supported on the rear axle case 22.

[0030] 1 and 3, an engine 23 is supported in the front portion of the transmission case 20. A hydrostatic continuously variable transmission 24 is connected to the left lateral side portion of the transmission case 20, and power from the engine 23 is transmitted to an input shaft 24a of the continuously variable transmission 24 via a transmission belt 25.

[0031] The continuously variable transmission 24 is configured to be able to change speeds continuously between a neutral position, forward travel, and reverse travel, and is operated by a speed change lever 30 provided on the left side of the steering handle 14.

[0032] [Configuration of the driving transmission system for the front and rear wheels] 3, a pump 26 is connected to the right lateral side of the transmission case 20, and the pump 26 supplies hydraulic oil to the hydraulic cylinder 4. The input shaft 24a of the continuously variable transmission 24 is inserted into the transmission case 20, and a transmission shaft 27 is connected between the input shaft 26a of the pump 26 and the input shaft 24a of the continuously variable transmission 24.

[0033] Transmission shafts 28, 29 are supported in the left-right direction inside the transmission case 20, and the output shaft 24b of the continuously variable transmission 24 is connected to an end of the transmission shaft 28. A gear-type sub-transmission device 31 is provided inside the transmission case 20 and extends across the transmission shafts 28, 29.

[0034] The auxiliary transmission 31 includes a low-speed gear 32 and a high-speed gear 33 connected to the transmission shaft 28, and a shift gear 34 fitted to the outside of the transmission shaft 29 by a spline structure so as to be rotatable and slidable integrally with the transmission shaft 28. The shift gear 34 can be slid using an auxiliary speed change lever (not shown) provided near the driver's seat 13.

[0035] In the auxiliary transmission 31, when the shift gear 34 is engaged with the low-speed gear 32, the power of the transmission shaft 28 is transmitted to the transmission shaft 29 at a low speed, and when the shift gear 34 is engaged with the high-speed gear 33, the power of the transmission shaft 28 is transmitted to the transmission shaft 29 at a high speed. Here, when planting work is being performed in a paddy field, the auxiliary transmission 31 is operated to the low-speed state, and when traveling at high speed on a road or the like, the auxiliary transmission 31 is operated to the high-speed state.

[0036] Right and left front axles 35 that transmit power to the right and left front wheels 1 are supported across the transmission case 20 and the front axle case 21, and a front wheel differential device 36 is provided between the right and left front axles 35. A transmission gear 37 connected to the transmission shaft 29 is in mesh with a transmission gear 38 connected to a case 36a of the front wheel differential device 36.

[0037] An output shaft 39 is supported in the front-to-rear direction at the rear of the transmission case 20. A bevel gear 40 connected to a case 36a of the front wheel differential device 36 is engaged with a bevel gear 39a formed at the front of the output shaft 39.

[0038] As shown in Figures 1 and 3, a transmission shaft 41 is connected to the rear of the output shaft 39 via a universal joint (not shown), and the rear of the transmission shaft 41 is connected to the input shaft (not shown) of the rear axle case 22 via a universal joint (not shown).

[0039] With the above configuration, the power changed in speed by the continuously variable transmission 24 is transmitted from the output shaft 24b of the continuously variable transmission 24 to the right and left front wheels 1 via the transmission shaft 28, the sub-transmission 31, the transmission shaft 29, the transmission gears 37 and 38, the front wheel differential device 36, and the front axle 35. In addition, the power transmitted to the front wheel differential device 36 is transmitted to the right and left rear wheels 2 via the bevel gear 40, the output shaft 39 (bevel gear 39a), the transmission shaft 41, and a transmission shaft (not shown) inside the rear axle case 22.

[0040] A multi-plate brake 42 is fitted to the output shaft 39, and the brake 42 can be put into a braking state by stepping on a brake pedal 43 shown in Figure 2. By applying the brake to the output shaft 39 with the brake 42, the front wheels 1 and rear wheels 2 can be braked.

[0041] [Configuration of the work transmission system for the seedling planting device] As shown in Figure 4, a hydrostatic planting inter-row transmission 45 (an example of the "continuously variable transmission" of the present invention) is connected to the right lateral side of the transmission case 20, and an input shaft 45a of the inter-row transmission 45 is connected to the transmission shaft 28. The input shaft 45a of the inter-row transmission 45 protrudes from the opposite side of the transmission case 20, and a fan 46 that sends cooling air to the inter-row transmission 45 is connected to the protruding portion of the input shaft 45a of the inter-row transmission 45.

[0042] Transmission shafts 47 and 48 are supported in the left-right direction inside the transmission case 20, and an output shaft 45b of the inter-section transmission device 45 is connected to an end of the transmission shaft 47.

[0043] The control device (not shown) and the actuator (not shown) rotate the speed change operating shaft 45c so that the distance between the stocks is based on the settings set by the operator, and the stock distance change transmission 45 is operated to the forward side, reverse side, and neutral position.

[0044] A cylindrical transmission shaft 49 is rotatably fitted onto the outside of the transmission shaft 47 via a needle bearing, and a transmission gear 50 having two sets of gears is rotatably fitted onto the outside of the transmission shaft 48 via a bearing. A transmission gear 47a formed on the transmission shaft 47 meshes with a large diameter gear portion of the transmission gear 50, and a transmission gear 51 connected to the transmission shaft 49 meshes with a small diameter gear portion of the transmission gear 50.

[0045] A gear-type variable speed transmission 52 is provided inside the transmission case 20 across the transmission shafts 48, 49, and a bevel gear 53 is connected to the transmission shaft 48. An output shaft 54 ​​is supported in the front-to-rear direction at the rear of the transmission case 20, and a bevel gear 55 is fitted onto the front of the output shaft 54 ​​via a drive clutch 56, with the bevel gears 53, 55 meshing with each other.

[0046] As shown in FIG. 4, the variable speed transmission device 52 includes a constant speed gear 58 and a variable speed gear 59 connected to the transmission shaft 49, and a constant speed gear 60 and a variable speed gear 61 fitted onto the transmission shaft 48 so as to be rotatable relative to each other, with the constant speed gears 58 and 60 meshing with each other and the variable speed gears 59 and 61 meshing with each other.

[0047] A key-shaped speed-changing member 62 is slidably supported inside the transmission shaft 48, and by sliding the speed-changing member 62 to engage with one of the constant velocity gear 60 and the variable velocity gear 61, the constant velocity gear 60 and the variable velocity gear 61 to which the speed-changing member 62 is engaged can be connected to the transmission shaft 48.

[0048] The constant velocity gears 58, 60 are circular gears with the same diameter. As a result, when the speed-changing member 62 is engaged with the constant velocity gear 60, the power of one rotation of the transmission shaft 49 is transmitted to the transmission shaft 48 as power of one rotation at a constant angular velocity.

[0049] The variable speed gears 59, 61 are elliptical gears, eccentric gears, or non-circular gears. When the speed-changing member 62 is engaged with one of the variable speed gears 61, the power of one rotation of the transmission shaft 49 is transmitted to the transmission shaft 48 as power of one rotation, but the angular velocity within one rotation changes between high and low.

[0050] As shown in Figures 1 and 4, a transmission shaft 57 is connected to the rear of the output shaft 54 ​​via a universal joint (not shown), and the rear of the transmission shaft 57 is connected to the input shaft (not shown) of the seedling planting device 5 via a universal joint (not shown).

[0051] With the above configuration, the power changed in speed by the continuously variable transmission 24 is transmitted from the output shaft 24b of the continuously variable transmission 24 to the inter-station transmission 45 via the transmission shaft 28 and the input shaft 45a of the inter-station transmission 45.

[0052] The power changed in speed by the inter-plant transmission device 45 is transmitted from the output shaft 45b of the inter-plant transmission device 45 to the seedling planting device 5 via the transmission shaft 47 (transmission gear 47a), transmission gears 50, 51, transmission shaft 49, variable speed transmission device 52, transmission shaft 48, bevel gears 53, 55, planting clutch 56, output shaft 54, and transmission shaft 57.

[0053] When the planting clutch 56 is operated to the transmission state, power is transmitted to the seedling planting device 5, and the seedling planting device 5 operates.

[0054] When the seedling planting device 5 is activated, as shown in Fig. 2, the seedling tray 10 is driven to reciprocate sideways, while the rotating case 7 is driven to rotate counterclockwise in Fig. 5, and the two sets of planting arms 8 alternately pick up seedlings from the bottom of the seedling tray 10 and plant them on the rice field surface. As a result, as shown in Fig. 5, seedlings are planted intermittently in the rice field surface at preset intervals along the traveling direction of the machine body 11.

[0055] When the planting clutch 56 is operated to the disconnected state, power to the seedling planting device 5 is cut off, the seedling planting device 5 stops, and the seedling tray 10 and the rotating case 7 stop.

[0056] [Configuration of the inter-row transmission] As shown in Figures 5 and 6, the inter-row transmission 45 includes an axial plunger type variable displacement hydraulic pump 71, an axial plunger type hydraulic motor 72, and a closed circuit 73 connecting the hydraulic pump 71 and the hydraulic motor 72.

[0057] The closed circuit 73 connecting the hydraulic pump 71 and the hydraulic motor 72 includes a high-pressure oil passage 73H that supplies pressurized oil from the hydraulic pump 71 to the hydraulic motor 72, and a low-pressure oil passage 73L that supplies pressurized oil from the hydraulic motor 72 to the hydraulic pump 71. A charge circuit 74 for replenishing the closed circuit 73 with pressurized oil is connected across the high-pressure oil passage 73H and the low-pressure oil passage 73L.

[0058] The hydraulic pump 71 is driven by power transmitted from the engine 23 via the input shaft 45a. The hydraulic pump 71 discharges pressure oil in an amount corresponding to the swash plate angle and supplies it to the hydraulic motor 72. The hydraulic motor 72 outputs power corresponding to the discharge amount of the hydraulic pump 71.

[0059] The inter-section transmission 45 includes a pressure reducing section 75 that reduces the pressure of the pressure oil supplied to the hydraulic motor 72 .

[0060] The pressure reducing section 75 includes a relief valve 76, an orifice 77, a first oil passage 78 connecting the relief valve 76 and the orifice 77 to the high pressure side oil passage 73H, and a second oil passage 79 connecting the relief valve 76 to the low pressure side oil passage 73L.

[0061] When the workload of the seedling planting device 5 increases and the pressure of the hydraulic oil in the high-pressure oil passage 73H exceeds the set value set by the relief valve 76, part of the hydraulic oil in the high-pressure oil passage 73H flows to the low-pressure oil passage 73L via the relief valve 76. This adjusts the pressure of the hydraulic oil in the high-pressure oil passage 73H.

[0062] Orifice 77 is provided at the end of first oil passage 78, i.e., between first oil passage 78 and relief valve 76. The inner diameter of orifice 77 is smaller than the inner diameter of first oil passage 78. With this configuration, even if the pressure of the hydraulic oil in high-pressure side oil passage 73H increases and causes relief valve 76 to open, it is possible to prevent a sudden drop in the pressure of the hydraulic oil in high-pressure side oil passage 73H.

[0063] [Fan Composition] As shown in FIG. 4, the fan 46 that sends cooling air to the inter-plant transmission 45 is connected to a protruding portion of the input shaft 45a of the inter-plant transmission 45. The fan 46 rotates as the input shaft 45a rotates, generating cooling air. The fan 46 is located between the right front wheel 1 and the inter-plant transmission 45 in a plan view. The inter-plant transmission 45 is positioned so as to be biased to the right relative to the center of the vehicle body 11. The fan 46 is positioned laterally outboard of the vehicle body relative to the inter-plant transmission 45.

[0064] The right front axle case 21 is disposed below the fan 46. The right front axle case 21 houses the right front axle 35. The right front axle 35 and the right front axle case 21 extend laterally of the aircraft. The left and right front axles 35 are located between the left and right front wheels 1 in a plan view. The right front axle 35 is driven to rotate based on the power of the engine 23 and transmits the power to the right front wheel 1. As shown in FIG. 4, the fan 46 overlaps with the right front axle case 21 in a plan view and is located above the right front axle case 21.

[0065] 4 and 7, the fan 46 has a connecting portion 46A connected to the input shaft 45a, a plurality of blade portions 46B, and a frame portion 46C. Each of the plurality of blade portions 46B extends radially outward from the connecting portion 46A, centered on the input shaft 45a. The frame portion 46C is connected to the outer peripheries of the plurality of blade portions 46B and surrounds the plurality of blade portions 46B from the outer periphery.

[0066] In the rice transplanter of this embodiment, a seedling planting device 5 is supported at the rear of the link mechanism 3. Instead of the seedling planting device 5, a furrow cutter, weeder, etc. can be attached to the rear of the link mechanism 3. Therefore, the rice transplanter of this embodiment can also be used as a furrow cutter or weeder.

[0067] When a furrow cutter or weeder is attached to the rear of the link mechanism 3 and the rice transplanter is used as a furrow cutter or weeder, it is conceivable that long seedlings or straw may get caught in the fan 46 and become entangled in the input shaft 45a. If this occurs, it may become difficult for the input shaft 45a to rotate, and the operating efficiency of the inter-row transmission 45 may decrease.

[0068] As shown in FIGS. 4 and 7 , in this embodiment, a frame 46C surrounds the multiple blade portions 46B from the outer periphery. The width of the frame 46C in the left-right direction of the machine body is wider than the width of the blade portions 46B in the left-right direction of the machine body. In other words, the width of the frame 46C in the axial direction of the input shaft 45a is wider than the width of each of the multiple blade portions 46B in the axial direction of the input shaft 45a. Therefore, the entire width of the blade portions 46B in the direction of the rotational axis of the fan 46 is covered by the frame 46C. With this configuration, compared to a configuration without the frame 46C, seedlings or straw that come into contact with the frame 46C are not entangled in the blade portions 46B and are less likely to become entangled around the input shaft 45a.

[0069] Furthermore, since the fan 46 has a frame portion 46C, even if the components around the fan 46 compete for space and it is difficult to install a cover, the fan 46 alone can be configured to prevent seedlings or straw from becoming entangled.

[0070] [Another embodiment] Hereinafter, another embodiment in which the above embodiment is modified will be exemplified.

[0071] (1) In the above embodiment, the pressure reducing unit 75 is provided with the relief valve 76 and the orifice 77, but the present invention is not limited to the above embodiment. For example, the pressure reducing unit 75 may be configured to have an accumulator that reduces the pressure of the pressure oil supplied to the hydraulic motor 72, instead of the relief valve 76. In this case, the accumulator may be configured to communicate with the high-pressure side oil passage 73H via an orifice.

[0072] (2) In the above embodiment, the relief valve 76 is connected to the high-pressure oil passage 73H and the low-pressure oil passage 73L, but the present invention is not limited to the above embodiment. For example, the relief valve 76 may be connected to an oil passage different from the low-pressure oil passage 73L.

[0073] (3) In the above embodiment, an example was described in which the pressure reducing section 75 is provided with an orifice 77, but the present invention is not limited to the above embodiment, and the pressure reducing section 75 may be configured not to be provided with an orifice 77.

[0074] (4) In the above embodiment, the orifice 77 is described as being provided in the first oil passage 78, but the present invention is not limited to the above embodiment, and the orifice 77 may be provided in the second oil passage 79.

[0075] (5) In the above embodiment, an example configuration in which the inter-plant transmission 45 is provided with the pressure reducing unit 75 has been described, but the present invention is not limited to the above embodiment, and the pressure reducing unit 75 may be provided in the continuously variable transmission 24 that changes the speed of power from the engine 23 and transmits it to the right and left front wheels 1 and rear wheels 2. This configuration makes it possible to reduce the increase in pressure of the hydraulic oil in the high-pressure oil passage of the continuously variable transmission 24 when the load on the continuously variable transmission 24 fluctuates due to unevenness in the ground.

[0076] (6) In the above embodiment, the relief valve 76 and the orifice 77 are provided in the row spacing transmission 45 that transmits power to the seedling planting device 5 provided in the rice transplanter. However, the present invention is not limited to the above embodiment. For example, the present invention can be applied to rice transplanters equipped with working devices other than the seedling planting device 5, as well as agricultural and construction machines such as combine harvesters and tractors.

[0077] The configurations disclosed in the above embodiments (including other embodiments, the same applies hereinafter) can be applied in combination with configurations disclosed in other embodiments, unless a contradiction arises. Furthermore, the embodiments disclosed in this specification are merely examples, and the present invention is not limited to these, and can be modified as appropriate within the scope of the purpose of the present invention. [Industrial Applicability]

[0078] The present invention can be used not only in rice transplanters, but also in work vehicles that transmit power from a continuously variable transmission to a work implement, such as combine harvesters, tractors, and construction work machines. [Explanation of symbols]

[0079] 5: Seedling planting device 23: Engine 24: Continuously variable transmission 26: Pump 45: Inter-row transmission (continuously variable transmission) 71: Hydraulic pump 72: Hydraulic motor 73H: High pressure oil passage 73L: Low pressure oil passage 75: Pressure reduction section 76: Relief valve 77: Orifice 78:First oil road 79:Second oil road

Claims

1. a seedling planting device for planting seedlings on the surface of the rice paddy; a hydrostatic continuously variable transmission having a hydraulic pump to which power from the engine is transmitted and a hydraulic motor to output the power, The continuously variable transmission includes a high-pressure oil passage that supplies pressurized oil from the hydraulic pump to the hydraulic motor, and a low-pressure oil passage that supplies pressurized oil from the hydraulic motor to the hydraulic pump, A rice transplanter equipped with a pressure reducing unit connected to the high-pressure side oil passage and reducing the pressure of the pressurized oil supplied to the hydraulic motor.

2. The rice transplanter according to claim 1, wherein the pressure reducing section has a relief valve.

3. The rice transplanter according to claim 2, wherein the relief valve is connected to the high-pressure side oil line and the low-pressure side oil line.

4. the pressure reducing section includes a first oil passage connecting the high-pressure side oil passage and the relief valve, and a second oil passage connecting the relief valve and the low-pressure side oil passage, The rice transplanter according to claim 3, wherein an orifice is provided in either the first oil passage or the second oil passage.

5. The orifice is provided in the first oil passage, The rice transplanter according to claim 4, wherein an inner diameter of the orifice is smaller than an inner diameter of the first oil passage.

6. the pressure reducing unit has an accumulator that reduces the pressure of the pressure oil supplied to the hydraulic motor, The rice transplanter according to claim 1, wherein the accumulator is in communication with the high-pressure oil passage via an orifice.

7. The rice transplanter according to claim 1, wherein the continuously variable transmission is an inter-row transmission that changes the speed of power from the engine and transmits it to the seedling planting device.

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