Work vehicle

Abstract

To provide a work vehicle that prevents overheating of a prime mover by preventing an excessive load from being applied on the prime mover.SOLUTION: A continuously variable transmission (42) which increases or decreases output rotation of a prime mover (E) is provided on a transmission path between the prime mover (E) and front wheels (2). A controller (60) automatically steering the front wheels (2) is provided in an operation section (5). The controller (60) sets a set route (72) along which a work vehicle travels under automatic steering based on travel position information received by a positioning device (32) arranged on a rear side of the operation section (5). The controller (60) is configured to receive a set route (390) with sparseness or density where sparseness or density of turf grass is superimposed on the set route (72), and increase or decrease a travel speed of the work vehicle by operating the continuously variable transmission (42) based on the sparseness or density of the turf grass on the set route (390) with sparseness or density.SELECTED DRAWING: Figure 13

Description

[Technical field]

[0001] The present invention relates to a work vehicle that increases or decreases its traveling speed depending on the density of turf grass. [Background technology]

[0002] A technology has been known in the past in which a work vehicle is automatically steered to change the direction of travel in response to grass detected by a camera mounted on the work vehicle, and the grass is cut (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-101619 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the load on the work vehicle's grass-cutting device varies greatly depending on the density of the grass; in other words, when the grass is dense, the load on the grass-cutting device is greater, and when the grass is sparse, the load on the grass-cutting device is smaller. Therefore, if a work vehicle is driven at the same speed through an area with dense grass, excessive load will be placed on the prime mover that transmits rotational power to the grass-cutting device, causing it to overheat or causing the cut grass to become clogged in the chute.

[0005] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to provide a work vehicle that prevents an excessive load from being applied to the prime mover, thereby suppressing overheating of the prime mover. [Means for solving the problem]

[0006] The present invention which has solved the above problems is as follows. That is, the invention described in claim 1 is a work vehicle having a pair of left and right front wheels (2) and rear wheels (3) provided below a body frame (1) on which a prime mover (E) is mounted, a grass cutting device (4) for cutting grass is provided in front of the body frame (1), and a control section (5) for an operator to ride on is provided above the body frame (1), The work vehicle is characterized in that a continuously variable transmission (42) that accelerates or decelerates the output rotation of the prime mover (E) is provided in a transmission path between the prime mover (E) and the front wheels (2), a controller (60) that automatically steers the front wheels (2) is provided in the steering unit (5), and the controller (60) sets a set route (72) along which the work vehicle travels while automatically steering, based on traveling position information received by a positioning device (32) arranged behind the steering unit (5), and the controller (60) receives a set route (390) with a turfgrass density superimposed on the set route (72), and operates the continuously variable transmission (42) to accelerate or decelerate the traveling speed of the work vehicle based on the turfgrass density of the set route (390).

[0007] A second aspect of the present invention provides the work vehicle according to the first aspect, wherein the controller (60) operates the continuously variable transmission (42) to increase or decrease the traveling speed in a stepped manner.

[0008] The invention described in claim 3 is the work vehicle described in claim 1 or 2, wherein the controller (60) stops increasing or decreasing the traveling speed when an operator is on the control unit (5) and a speed change pedal (26) of the control unit is depressed.

[0009] The invention described in claim 4 is the work vehicle described in claim 1 or 2, wherein the controller (60) gradually increases or decreases the traveling speed in a ramp pattern over time when an operator is seated on the control unit (5) and a speed change pedal (26) of the control unit is not depressed.

[0010] The invention recited in claim 5 is the work vehicle recited in claim 4, wherein the controller (60) sets a maximum traveling speed of the work vehicle to a speed lower than the traveling speed at which the speed change pedal (26) is most depressed.

[0011] A sixth aspect of the present invention provides the work vehicle according to the fifth aspect, wherein the controller (60) calculates in advance a grass cutting operation time from the set route (72) and the travel speed. Effect of the Invention

[0012] According to the invention described in claim 1, a continuously variable transmission (42) that increases or decreases the output rotation of the prime mover (E) is provided in the transmission path between the prime mover (E) and the front wheels (2), a controller (60) that automatically steers the front wheels (2) is provided in the steering unit (5), the controller (60) sets a set route (72) along which the work vehicle travels while automatically steering based on travel position information received by a positioning device (32) located behind the steering unit (5), the controller (60) receives a set route (390) with a turfgrass density superimposed on the set route (72), and operates the continuously variable transmission (42) to increase or decrease the travel speed of the work vehicle based on the turfgrass density of the set route (390), so that the load on the prime mover (E) is prevented from becoming excessive and the prime mover (E) is prevented from overheating. Also, the cut grass can be prevented from clogging the chute.

[0013] According to the invention recited in claim 2, in addition to the effect of the invention recited in claim 1, the controller (60) operates the continuously variable transmission (42) to increase or decrease the traveling speed in a stepped manner, so that the traveling speed can be increased or decreased quickly.

[0014] According to the invention described in claim 3, in addition to the effects of the invention described in claim 1 or 2, when an operator is in the control section (5) and the speed change pedal (26) of the control section is depressed, the controller (60) stops increasing or decreasing the traveling speed, so that the operator in the control section (5) can drive the work vehicle at an optimal traveling speed.

[0015] According to the invention of claim 4, in addition to the effects of the invention of claim 1 or 2, when an operator is on the control section (5) and the speed change pedal (26) of the control section is not depressed, the controller (60) gradually increases or decreases the traveling speed in a ramp pattern over time, thereby making it possible to prevent the operator from experiencing excessive shock when the traveling speed is increased or decreased.

[0016] According to the invention recited in claim 5, in addition to the effect of the invention recited in claim 4, the controller (60) sets the maximum traveling speed of the work vehicle to a speed lower than the traveling speed at which the speed change pedal (26) is fully depressed, thereby making it possible to further prevent excessive shocks from being applied to the worker when the traveling speed is increased or decreased.

[0017] According to the invention recited in claim 6, in addition to the effect of the invention recited in claim 5, the controller (60) calculates the grass mowing operation time in advance from the set route (72) and the traveling speed, so that the operation completion time is known before the start of the mowing operation, making it easier to plan the operation. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is an explanatory diagram of the system. [Diagram 2] FIG. [Diagram 3] 3 is a transmission diagram of the output rotation of a prime mover of a work vehicle. [Figure 4] FIG. 1 is a hardware block diagram of a work vehicle, a drone, and a server. [Diagram 5] FIG. 4 is an explanatory diagram of a set route for a work vehicle. [Figure 6] FIG. 1 is an explanatory diagram of a drone flying above a set route. [Figure 7] FIG. 1 is an explanatory diagram of a convolutional neural network. [Figure 8] FIG. 2 is an explanatory diagram of a perceptron node. [Figure 9] FIG. 1 is an explanatory diagram of a convolutional layer. [Figure 10]FIG. [Figure 11] FIG. 2 is an explanatory diagram of a pooling layer. [Figure 12] FIG. 13 is an explanatory diagram of data showing the grass density overlaid on a set route. [Figure 13] 4 is an explanatory diagram of a method for increasing or decreasing the travel speed of a work vehicle. FIG. [Figure 14] FIG. 1 is an explanatory diagram of a work vehicle traveling while automatically steering along a set route. [Figure 15] FIG. 1 is an explanatory diagram of turfgrass density and running speed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] As shown in Fig. 1, the system 500 includes a work vehicle 100 such as a tractor, a drone 200 that flies over a field or the like to photograph the grass growing in the field, and a server 300 that analyzes the density of the grass in the photographs taken by the drone 200, all of which are wirelessly connected to each other via a network 400 so as to be able to communicate with each other. The server 300 also analyzes the density of the grass in the photographs taken by the drone 200 using a convolutional neural network (hereinafter referred to as CNN).

[0020] As shown in FIG. 2, the work vehicle 100 has a pair of left and right front wheels 2 provided on the front underside of a body frame 1 on which a prime mover E such as an engine or an electric motor is mounted, and a pair of left and right rear wheels 3 provided on the rear underside of the body frame 1.

[0021] A grass cutting device 4 for cutting grass growing in the field is provided at the front of the machine frame 1, a control unit 5 for the operator to ride on is provided at the rear of the grass cutting device 4, a safety frame (ROPS) 6 for protecting the operator is provided at the rear of the control unit 5, and a grass collection container 7 for storing the cut grass is provided at the rear of the safety frame 6.

[0022] The rear of the grass cutting device 4 and the front of the grass collection container 7 are connected by a chute 10. The chute 10 is formed of a front chute 10A and a rear chute 10B, and a blower 11 that exhausts air into the chute 10 is disposed between the front chute 10A and the rear chute 10B. In addition, a pair of left and right L-shaped arms 12 connected to the lifting cylinder 27 are provided at the rear of the grass cutting device 4.

[0023] A steering column 22 supporting a steering wheel 21 is provided in front of the cockpit 20 of the control section 5. A touch-type monitor 23 that displays the output speed of the prime mover E and the like is provided at the top of the steering column 22, and the bottom is fixed to the front part of a floor 24 on which an operator places his / her legs. In addition, a seat sensor 24S is provided in the cockpit 20 to measure whether an operator is seated in the control section 5 or not.

[0024] A brake pedal 25 for decelerating the rotation speed of the front wheels 2, which are the driving wheels, is provided on the left side of the floor 24, and a speed change pedal 26 for operating a hydraulic continuously variable transmission (hereinafter referred to as "HST") 42, which will be described later, for increasing or decreasing the output rotation speed of the prime mover E is provided on the right side. The amount of depression of the speed change pedal 26 is measured by an angle sensor 26S attached to the base of the speed change pedal 26.

[0025] A lifting cylinder 27 connected to the arm 12 of the grass cutting device 4 is provided below the floor 24. The longitudinal direction of the lifting cylinder 27 is arranged along the front-to-rear direction. When the piston in the tube of the lifting cylinder 27 moves rearward, the grass cutting device 4 rises and the mowing height increases, and when the piston moves forward, the grass cutting device 4 descends and the mowing height decreases.

[0026] The upper part of the front wheel 2 is covered with a fender 28, and the fender 28, located on the left side of the cockpit 20, is provided with a throttle lever 29 for increasing or decreasing the output speed of the prime mover E by operating a throttle valve that adjusts the amount of diesel fuel supplied to the prime mover E. When the upper part of the throttle lever 29 is moved forward of the lower part to transition to a forward leaning posture, the output speed of the prime mover E increases, and when the upper part of the throttle lever 29 is moved rearward of the lower part to transition to a backward leaning posture, the output speed of the prime mover E decreases. The amount of operation of the throttle lever 29 is measured by an angle sensor attached to the base of the throttle lever 29.

[0027] A lift lever 30 is provided behind the throttle lever 29 to operate a valve that supplies oil to the lift cylinder 27, which adjusts the grass cutting height H. The amount of operation of the lift lever 30 is measured by an angle sensor attached to the base of the lift lever 30.

[0028] A reinforcing member 31 extending in the left-right direction is provided in the vertical middle part of the safety frame 6. The reinforcing member 31 is provided in the front-rear center part of the work vehicle 100 excluding the grass cutting device 4, and a positioning device 32 such as a GPS antenna that receives information transmitted from a positioning satellite and a base station is attached to the left-right center part of the reinforcing member 31. This makes it possible to accurately set a set route 72 (described later) along which the work vehicle 100 travels while being automatically steered, based on the information transmitted from the positioning satellite and the base station.

[0029] As shown in FIG. 3, the output rotation of the prime mover E is transmitted to a rotating shaft 40, and then transmitted to a rotating shaft 41 provided perpendicular to the rotating shaft 40 via a joint.

[0030] The output rotation transmitted to the rotating shaft 41 is transmitted to the HST 42 , where it is accelerated or decelerated, and then transmitted to the rotating shaft 43 .

[0031] The output rotation transmitted to the rotating shaft 43 is transmitted to the front wheels 2 via a front wheel differential gear 44. In addition, the output rotation transmitted to the rotating shaft 43 is transmitted to the rear wheels 3 via a 4WD clutch 45 and a rear wheel differential gear 46. A 4WD switch (not shown) for connecting and disconnecting the 4WD clutch 45 is provided on the rear side of the monitor 23 at the top of the steering column 22.

[0032] The output rotation transmitted to the rotating shaft 41 is transmitted to the mower PTO 51 via the mower PTO clutch 50 to rotate the grass cutting blade built into the grass cutting device 4. A mower switch (not shown) for connecting and disconnecting the mower PTO clutch 50 is provided on the rear side of the monitor 23 at the top of the steering column 22.

[0033] The output rotation transmitted to the rotary shaft 41 is transmitted to a blower PTO 56 via a blower PTO clutch 55, and rotates the blower blades mounted inside the blower 11. A blower switch (not shown) for connecting and disconnecting the blower PTO clutch 55 is provided behind the monitor 23 at the top of the steering column 22.

[0034] As shown in Fig. 1, the drone 200 is provided with a driving device 210 such as an electric motor that rotates a propeller, a photographing device 220 such as a camera that photographs the grass growing in the field from above, a positioning device 230 such as a GPS antenna that receives information transmitted from a positioning satellite and a base station, and an inertial measurement unit 240 that measures the drone's flight attitude, etc. This makes it possible to photograph the grass growing in the field by facing the lens of the photographing device 220 toward the field, and to accurately calculate the density of the grass based on the photograph. The server 300 is also located in a remote location away from the field.

[0035] As shown in Figure 4, the controller 60 of the work vehicle 100 is formed from a processing unit 61 consisting of a CPU etc., a memory unit 62 consisting of a ROM, RAM, a hard disk drive, flash memory etc., an input / output unit 63 having an input / output interface circuit, and a communication unit 64 that communicates with the drone 200 and the server 300 via the network 400.

[0036] The processing unit 61 sets a set route 72 for automatically steering the work vehicle 100 based on the travel position information of the work vehicle 100 measured by a positioning satellite received by the positioning device 32, the mowing width of the grass cutting device 4, and the like.

[0037] The memory unit 62 stores the mowing width of the grass mower 4 input in advance to the monitor 23, a correlation equation of the travel speed of the work vehicle 100 corresponding to the grass density calculated by the server 300, and the like.

[0038] The input side of the input / output unit 63 is connected via a specified input interface circuit to devices such as a seat sensor 24S that measures whether or not an operator is seated in the control unit 5, an angle sensor 26S that measures the amount of depression of the speed change pedal 26, and a positioning device 32, while the output side is connected via a specified output interface circuit to devices such as an HST motor 42A that rotates the trunnion axis that operates the HST 42.

[0039] The communication unit 64 communicates with the drone 200 and the server 300 via the network 400.

[0040] The controller 260 of the drone 200 is formed from a processing unit 261 consisting of a CPU etc., a memory unit 262 consisting of a ROM, RAM, a hard disk drive, flash memory etc., an input / output unit 263 having an input / output interface circuit, and a communication unit 264 that communicates with the work vehicle 100 and the server 300 via the network 400.

[0041] The processing unit 261 calculates a flight setting route 75 in which the drone 200 flies above the set route 72 of the work vehicle 100 received by the communication unit 264, controls the driving device 210 to fly the drone 200 along the flight setting route 75, and adds information such as the shooting location and shooting date and time to the photo of the grass taken by the photographing device 220.

[0042] The memory unit 262 stores the flight speed of the drone 200 and the shooting interval of the imaging device 220 corresponding to the mowing width of the grass cutting device 4 received by the communication unit 264.

[0043] The communication unit 264 communicates with the work vehicle 100 and the server 300 via the network 400 .

[0044] The controller 360 of the server 300 is formed from a processing unit 361 consisting of high-speed processing chips such as GPU, FPGA, and ASIC, a memory unit 362 consisting of ROM, RAM, a hard disk drive, flash memory, etc., an input / output unit 363 having an input / output interface circuit, and a communication unit 364 that communicates with the work vehicle 100 and the drone 200 via the network 400.

[0045] The processing unit 361 uses CNN to calculate the density of the grass based on the photo of the grass received by the communication unit 364, and overlays the calculated density on the set route 72 of the work vehicle 100. Furthermore, if the vertical and horizontal sizes of the photograph of the grass received by the communication unit 364 are larger than the mowing width of the grass mowing device 4, the vertical and horizontal sizes are trimmed to match the mowing width of the grass mowing device 4.

[0046] The memory unit 362 stores the flight speed of the drone 200 and the shooting interval of the imaging device 220 corresponding to the mowing width of the grass cutting device 4 received by the communication unit 275.

[0047] The communication unit 364 communicates with the work vehicle 100 and the drone 200 via the network 400.

[0048] <Setting route> 5, the worker carries the work vehicle 100 into the field 70 through the entrance 70A of the field 70. Next, the worker presses the reference path switch provided on the operation unit 5, and then drives the work vehicle 100 along the inner periphery of the ridge of the field 70 while manually steering it counterclockwise.

[0049] The controller 60 calculates a reference route 71 along which the worker has manually steered the work vehicle 100 based on position information received by the positioning device 32 from a positioning satellite, and stores the reference route 71 in the memory unit 62. Note that although the form shown in Fig. 5 shows the work vehicle 100 traveling in a counterclockwise direction, it can also be traveled in a clockwise direction.

[0050] After the worker has driven the work vehicle 100 while manually steering it, he or she presses the set route switch provided on the operation unit 5. The controller 60 calculates a set route 72 along which the work vehicle 100 will be driven by automatically steering it based on the reference route 71, and stores the calculated set route 72 in the memory unit 62.

[0051] The set path 72 is formed of a straight set path 72A that extends linearly in the vertical direction, and a semicircular turning set path 72B that connects the end of the straight set path 72A to the start of the adjacent straight set path 72A. The distance between the straight set path 72A and the adjacent straight set path 72A is set to the mowing width of the grass cutting device 4. This makes it possible to efficiently set the set path 72 along which the work vehicle 100 travels while automatically steering in accordance with the shape of the field 70.

[0052] After completing travel along the set route 72, the work vehicle 100 is driven by the worker while manually steering it and transported out of the field 70 through the entrance 70A. Note that in Fig. 5, the reference route 71 along which the worker has driven the work vehicle 100 while manually steering it is shown by a solid line, and the set route 72 along which the controller 60 has driven the work vehicle 100 while automatically steering it is shown by a dashed line.

[0053] <Flight route setting> As shown in Figure 6, based on a set route 72 along which the work vehicle 100 will travel while automatically steering, which is received by the communication unit 264 of the controller 260 of the drone 200 via the network 400, a flight set route 75 along which the drone 200 will fly while automatically operating above the set route 72 is calculated and stored in the memory unit 262.

[0054] The flight set route 75 is formed on the same route as the set route 72, and is formed of a straight flight set route 75A that extends in a straight line in the vertical direction, and a semicircular turning flight set route 75B that connects the end of 75A to the start of the adjacent straight flight set route 75A. This allows the server 300 to efficiently perform the alignment process of the photos taken by the imaging device 220 of the drone 200.

[0055] The photograph of the grass taken by the photographing device 220 is formed in a square shape, and the vertical and horizontal lengths of the photograph are set to the mowing width of the grass mower 4. This allows the server 300 to efficiently calculate the grass density and overlay the calculated grass density on the set route 72. Note that reference numeral 76 indicates the photograph of the grass taken by the photographing device 220. Also, satellite photographs can be used instead of the photograph of the grass taken by the photographing device 220.

[0056] <Density of turfgrass> As shown in Fig. 7, the CNN 370 used by the processing unit 361 of the controller 360 of the server 300 is formed of an input layer 371, a convolution layer 372, a pooling layer 373, a fully connected layer 374, and an output layer 375. Note that Fig. 7 illustrates the layers of the CNN 370 in a deformed form.

[0057] As shown in FIG. 8, an input layer 371, a convolution layer 372, a pooling layer 373, etc. are formed from perceptron nodes 376.

[0058] The input layer 370 receives image data 380 of a photo 76 of grass taken by the photographing device 220 of the drone 200 and received by the communication unit 364 of the controller 360 of the server 300 via the network 400 .

[0059] In the convolution layer 372, first, as shown in Fig. 9(a), image data 380 of the grass photo 76 is divided into pixels 381 that can be processed by the processing unit 361. Fig. 9(a) also illustrates the form in which the image data 380 is divided into 8 x 8 pixels 381.

[0060] Next, as shown in Figures 9(b) to (d), image data 380 is filtered using filter 382A obtained by prior learning as shown in Figure 10(a) to output feature map 383A. Also, Figure 9(d) shows a form in which feature map 383A is divided into 6 x 6 pixels 384A, and the numerical values ​​A11 of 1 x 1 pixel 384A and A66 of 6 x 6 pixel 384A indicate the degree of match with filter 382A.

[0061] The numerical values ​​A11 and A66 are calculated by inputting 1 to pixels 381 where the pixel of 3×3 pixel 381 being filtered by filter 382A matches the pixel of filter 382A, and inputting 0 where the pixel does not match, and dividing the sum of the input values ​​of 3×3 pixel 381 by 9; the closer the numerical value is to 1, the more it matches filter 382A, and the closer the numerical value is to 0, the less it matches filter 382A.

[0062] Next, as shown in Figures 9(e) to (g), image data 380 is filtered using filter 382B obtained by prior learning shown in Figure 10(b) to output feature map 383B. Also, Figure 9(g) illustrates a form in which feature map 383B is divided into 6 x 6 pixels 384B, and the numerical values ​​B11 of 1 x 1 pixel 384B and B66 of 6 x 6 pixel 384B indicate the degree of match with filter 382B.

[0063] The numerical values ​​B11 and B66 are calculated by inputting 1 into pixels 381 where the pixel of 3×3 pixel 381 being filtered by filter 382B matches the pixel of filter 382B, and inputting 0 where the pixel does not match, and dividing the sum of the input values ​​of 3×3 pixel 381 by 9; the closer the numerical value is to 1, the more it matches filter 382B, and the closer the numerical value is to 0, the less it matches filter 382B.

[0064] Next, as shown in Figures 9(h) to (j), image data 380 is filtered using filter 382C obtained by prior learning as shown in Figure 10(c) to output feature map 383C. Also, Figure 9(j) shows a form in which feature map 383C is divided into 6 x 6 pixels 384C, and the numerical values ​​of C11 of 1 x 1 pixel 384C and C66 of 6 x 6 pixel 384C indicate the degree of match with filter 382C.

[0065] The numerical values ​​of C11 and C66 are calculated by inputting 1 into pixels 381 where the pixel of 3×3 pixel 381 being filtered by filter 382C matches the pixel of filter 382C, and inputting 0 where the pixel does not match, and dividing the sum of the input values ​​of 3×3 pixel 381 by 9; the closer the numerical value is to 1, the more it matches filter 382C, and the closer the numerical value is to 0, the less it matches filter 382C.

[0066] 11(a) and (b), the pooling layer 373 selects the maximum value for each 2×2 pixel 384A of the 6×6 pixel 384A of the feature map 383A and outputs pooled image data 385A. The pooled image data 385A is also divided into 5×5 pixels 386A, and a11 of the 1×1 pixel 386A and a55 of the 5×5 pixel 386A indicate the maximum value for each 2×2 pixel 384A. This makes it possible to reduce the image data 380 while retaining important information of the feature map 383A.

[0067] 11(c) and (d), the maximum value of each 2×2 pixel 384B of the 6×6 pixel 384B of the feature map 383B is selected to output pooled image data 385B. The pooled image data 385B is also divided into 5×5 pixels 386B, and b11 of the 1×1 pixel 386B and b55 of the 5×5 pixel 386B indicate the maximum value of each 2×2 pixel 38BA. This makes it possible to reduce the image data 380 while retaining important information of the feature map 383B.

[0068] 11(e) and (f), the maximum value of each 2×2 pixel 384C of the 6×6 pixel 384C of the feature map 383C is selected to output pooled image data 385C. The pooled image data 385C is also divided into 5×5 pixels 386C, and c11 of the 1×1 pixel 386C and c55 of the 5×5 pixel 386C indicate the maximum value of each 2×2 pixel 384C. This makes it possible to reduce the image data 380 while retaining important information of the feature map 383C.

[0069] The pooled image data 385A to 385C become image data to be input to the next convolution layer 372, and are filtered again by a filter (not shown) obtained by learning in advance and different from the filters 382A to 382C.

[0070] The fully connected layer 374 sums the values ​​of the pooled image data 385A-385C and outputs the respective proportions of the image data 380 of the grass photo 76 that match the filters 382A-382C.

[0071] The output layer 375 outputs the sparseness of the image data 380 of the grass photo 76 from the sparseness of the grass of the filters 382A to 382C and the output of the fully connected layer 374. For example, if the sparseness of the grass of the filter 382A is 78% and the matching rate is 50%, the sparseness of the grass of the filter 382B is 56% and the matching rate is 40%, and the sparseness of the grass of the filter 382C is 33% and the matching rate is 10%, then the sparseness of the grass is output as 64.7% ((0.78×0.5+0.56×0.4+0.33×0.1)×100=64.7[%]). The sparseness of the grass output from the output layer 375 is stored in the memory unit 362.

[0072] <Overlay of the set route and grass density> As shown in Figure 12, the processing unit 361 of the controller 360 of the server 300 reads out the set route 72 along which the work vehicle 100 will travel while automatically steering, and the turfgrass density, stored in the memory unit 362, and creates a set route 390 with turfgrass density by overlaying the turfgrass density on the set route 72, and then transmits this to the work vehicle 100 via the network 400. Note that the reference numeral 391 indicates a high density area where the turfgrass density is high, the reference numeral 392 indicates a medium density area where the turfgrass density is medium, and the reference numeral 393 indicates a low density area where the turfgrass density is low.

[0073] <How to increase or decrease the driving speed of a work vehicle> As shown in FIG. 13, in step S1, the processing unit 61 of the controller 60 of the work vehicle 100 reads out the sparse / dense set route 390 received by the communication unit 64 from the storage unit 62 via the network 400, and proceeds to step S2.

[0074] In step S2, the processing unit 61 automatically steers the work vehicle 100 along the set route 72 of the densely populated set route 390, and determines whether or not an operator is on board the steering unit 5.

[0075] If the input signal of the seat sensor 24S is OFF and it is determined that an operator is not in the control unit 5, the process proceeds to step S3; if the input signal of the seat sensor 24S is ON and it is determined that an operator is in the control unit 5, the process proceeds to step S6.

[0076] In step S3, the processing unit 61 reads the traveling position information received by the positioning device 32, and the process proceeds to step S4.

[0077] In step S4, the processing unit 61 reads the grass density displayed on the set route 72 of the grass density-added set route 390 corresponding to the travel position information of the work vehicle 100, and proceeds to step S5.

[0078] In step S5, the processing unit 61 drives the HST motor 42A to increase or decrease the output rotation speed of the HST 42, so that the travel speed of the work vehicle 100 becomes the corresponding travel speed corresponding to the grass density read in step S4, and then returns to step S1. This prevents the load on the prime mover E from becoming excessive, and suppresses overheating of the prime mover E. In addition, the time required for mowing work can be calculated by dividing the set route 72 of the grass density set route 390 by the corresponding travel speed.

[0079] The output rotation speed of the prime mover E and the grass cutting blade of the grass cutting device 4 to which the output rotation of the prime mover E is transmitted without passing through the HST 42 is not increased or decreased. Also, as shown in Fig. 14, the grass density displayed on the traveled set route 73 on the set route 72 where the work vehicle 100 has already traveled is erased as needed. This makes it possible to prevent the capacity of the memory unit 62 from becoming excessively large.

[0080] In step S6, the processing unit 61 determines whether the operator is depressing the speed change pedal 26 or not.

[0081] If the input signal from the angle sensor 26S, which measures the amount of depression of the speed change pedal 26, is equal to or greater than a predetermined value, indicating that the operator is depressing the speed change pedal 26, the process proceeds to step S7. If the input signal from the angle sensor 26S is less than a predetermined value, indicating that the operator is not depressing the speed change pedal 26, the process proceeds to step S8.

[0082] In step S7, the processing unit 61 drives the HST motor 42A based on the depression amount of the speed change pedal 26, ie, the input signal from the angle sensor 26S, to increase or decrease the output rotation speed of the HST 42, and then returns to step S1.

[0083] In step S8, the processing unit 61 sets the maximum travel speed of the work vehicle 100, and proceeds to step S9. This limits the maximum travel speed of the work vehicle 100, thereby improving safety. The maximum travel speed is set to a speed lower than the travel speed when the worker fully depresses the speed change pedal 26. This makes it possible to prevent excessive shock from being applied to the worker on the control unit 5 when accelerating.

[0084] In step S9, the processing unit 61 reads the traveling position information received by the positioning device 32, and the process proceeds to step S10.

[0085] In step S10, the processing unit 61 reads the grass density displayed on the set route 72 of the grass density-added set route 390 corresponding to the travel position information of the work vehicle 100, and proceeds to step S11.

[0086] In step S11, the processing unit 61 drives the HST motor 42A to increase or decrease the output rotation speed of the HST 42, so as to increase or decrease the travel speed of the work vehicle 100 to a travel speed corresponding to the density of the turfgrass read in step S4, and then returns to step S1. This prevents the load on the prime mover E from becoming excessive, and suppresses overheating of the prime mover E.

[0087] Furthermore, when increasing or decreasing the travel speed of the work vehicle 100, it is preferable to increase or decrease the travel speed gradually over time in a ramp manner rather than increasing or decreasing the travel speed in a step manner. This can further reduce the shock that is applied to the worker when the travel speed is increased or decreased.

[0088] <Travel speeds according to sparseness of grass> As shown in FIG. 15(a), the processing unit 61 of the controller 60 of the work vehicle 100 linearly reduces the travel speed of the work vehicle 100 as the density of the turfgrass on the sparsely-packed set route 390 increases.

[0089] As shown in Fig. 15(b), the processing unit 61 of the controller 60 of the work vehicle 100 can also gradually reduce the travel speed of the work vehicle 100 as the density of the grass on the sparsely-densified set route 390 increases. This can reduce the processing load on the processing unit 61 of the controller 60 and can quickly increase or decrease the travel speed of the work vehicle 100. Note that in Fig. 15(b), the sparsely-densified grass on the sparsely-densified set route 390 is divided into three density zones, a high density zone 391, a medium density zone 392, and a low density zone 393, and the travel speed of the work vehicle 100 is increased or decreased in three stages, but the sparsely-densified set route 390 can also be divided into four to six sparse-density zones and the travel speed of the work vehicle 100 can be increased or decreased in four to six stages. [Explanation of symbols]

[0090] 1 Aircraft frame 2 Front wheels 3 Rear wheel 4 Grass cutting equipment 5. Control Unit 26 Gear shift pedal 32 Positioning device 42 Continuously variable transmission (HST) 60 Controller 72 Setting Route 390 Route planning with sparse density E Prime Mover

Claims

1. A work vehicle having a pair of left and right front wheels (2) and rear wheels (3) provided below a body frame (1) on which a prime mover (E) is mounted, a grass cutting device (4) for cutting grass is provided in front of the body frame (1), and a control section (5) for an operator to ride on is provided above the body frame (1), a continuously variable transmission (42) for increasing or decreasing the output rotation of the prime mover (E) is provided in a transmission path between the prime mover (E) and the front wheels (2); The steering unit (5) is provided with a controller (60) for automatically steering the front wheel (2); The controller (60) sets a set route (72) along which the work vehicle travels while automatically steering, based on travel position information received by a positioning device (32) arranged behind the steering unit (5); The controller (60) receives a set route (390) with a turfgrass density superimposed on the set route (72), and operates the continuously variable transmission (42) to increase or decrease the travel speed of the work vehicle based on the turfgrass density of the set route (390).

2. 2. The work vehicle according to claim 1, wherein the controller (60) operates the continuously variable transmission (42) to increase or decrease the travel speed in a stepped manner.

3. 3. The work vehicle according to claim 1, wherein the controller (60) stops increasing or decreasing the traveling speed when an operator is on the control unit (5) and a speed change pedal (26) of the control unit is depressed.

4. 3. A work vehicle as described in claim 1 or 2, wherein the controller (60) increases or decreases the traveling speed gradually in a ramp manner over time when an operator is on the control unit (5) and a speed change pedal (26) of the control unit is not depressed.

5. 5. The work vehicle according to claim 4, wherein the controller (60) sets a maximum travel speed of the work vehicle to a speed lower than the travel speed at which the speed change pedal (26) is most depressed.

6. 6. The work vehicle according to claim 5, wherein the controller (60) calculates in advance a grass cutting operation time from the set route (72) and the travel speed.

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