JP2019196169A - Work vehicle - Google Patents

Abstract

To provide a work vehicle mounted with a one-sided brake, which can improve operability.SOLUTION: A work vehicle 1 is equipped with: left and right brake pedals 12L and 12R; a pedal connection part 303; a pedal connection/operation part 310; a detection part 137; a control part 120; a four-wheel-drive clutch that switches drive into either of two-wheel drive and four-wheel drive; a lock mechanism that locks and unlocks the pedal connection part with the left and right brake pedals connected; and a lock operation detection part 138 that detects operation of the lock mechanism. During the two-wheel drive, when the brake pedal is operated, the four-wheel-drive clutch is switched into the four-wheel drive, and if the lock operation detection part detects the unlocking by the lock mechanism, switching of the four-wheel-drive clutch is neglected even if the brake pedal is operated.SELECTED DRAWING: Figure 11

Description

  The present invention relates to a work vehicle.

  2. Description of the Related Art Conventionally, work vehicles such as agricultural tractors have left and right brake pedals corresponding to wheels (for example, rear wheels) driven by engine power. The brake pedal is connected to the left and right when used to brake the left and right wheels simultaneously, and is disconnected from the left and right when used to brake the left and right wheels individually.

  Further, there is a technique for detecting engine depression by detecting the depression of the brake pedal and detecting the depression of the brake pedal to automatically disconnect the travel clutch (see, for example, Patent Document 1).

Japanese Patent Laying-Open No. 2015-067093

  However, the conventional work vehicle as described above sometimes disengages the traveling clutch even when a so-called one-brake operation in which one of the left and right brake pedals is depressed, and sometimes stops against the operator's intention. Thus, the conventional work vehicle has room for improvement in operability.

  The present invention has been made in view of the above, and an object thereof is to provide a work vehicle capable of improving operability.

In order to solve the above-described problems and achieve the object, a work vehicle according to claim 1 is provided:
Left and right brake pedals operated respectively when braking left and right wheels,
A pedal connecting portion for connecting the left and right brake pedals;
A pedal coupling operation unit that is operated when the left and right brake pedals are coupled / uncoupled by the pedal coupling unit;
When the brake pedal is operated during two-wheel drive, a control unit that controls the 4WD clutch to switch to four-wheel drive;
A 4WD clutch that switches to either two-wheel drive or four-wheel drive;
A lock mechanism for locking / unlocking the pedal connecting portion in a state where the left and right brake pedals are connected;
A lock operation detector for detecting an operation of the lock mechanism;
With
The controller is
When unlocking by the lock mechanism is detected by the lock operation detection unit, switching of the 4WD clutch is ignored even when the brake pedal is operated.

The work vehicle according to claim 2, wherein the control unit is the work vehicle according to claim 1.
When the brake pedal is operated, it controls to disengage the travel clutch,
When unlocking by the lock mechanism is detected by the lock operation detection unit, the disengagement of the travel clutch is ignored even if the brake pedal is operated.

According to the work vehicle of claim 1,
When unlocking by the lock mechanism is detected, when the one-brake operation is performed, it is possible to steer as intended by the operator by avoiding the switching of the 4WD clutch accompanying the brake operation. Thereby, operativity can be made favorable.

  According to the work vehicle of the second aspect, when unlocking by the lock mechanism is detected, when the one-brake operation is performed, the unintended stop by the operator is avoided by avoiding the disconnection of the traveling clutch accompanying the brake operation. Can be prevented. Thereby, operativity can be made favorable.

FIG. 1 is a schematic left side view of a work vehicle. FIG. 2 is a transmission path diagram in the mission case. FIG. 3 is a schematic cross-sectional view of the forward / reverse clutch. FIG. 4 is a hydraulic circuit diagram of the work vehicle. FIG. 5 is an explanatory diagram of the operating device in front of the cockpit. FIG. 6 is an enlarged view of a portion A in FIG. FIG. 7 is an explanatory diagram of the operating device on the right side of the cockpit. FIG. 8 is a schematic perspective view of the left and right brake pedals. FIG. 9 is an explanatory diagram of the pedal connection operation unit. FIG. 10A is an operation explanatory diagram (No. 1) of the lock mechanism. FIG. 10B is an operation explanatory diagram (No. 2) of the locking mechanism. FIG. 11 is a block diagram of the control unit. FIG. 12 is a timing chart of brake control when the left and right brake pedals are connected. FIG. 13 is a timing chart of brake control when the left and right brake pedals are in a disconnected state. FIG. 14 is a timing chart of the brake control in the locked state by the lock mechanism. FIG. 15 is a timing chart of the brake control in the unlocked state by the lock mechanism. FIG. 16 is an explanatory diagram of the relationship between the rotational speed and the torque in normal engine control. FIG. 17 is an explanatory diagram of an example of the relationship between the rotational speed and torque in engine control. FIG. 18 is an explanatory diagram of another example of the rotation speed-torque relationship in engine control.

  Hereinafter, an embodiment of a work vehicle disclosed in the present application will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by embodiment shown below.

  FIG. 1 is a schematic left side view of a work vehicle. Hereinafter, the tractor 1 will be described as an example of the work vehicle. The tractor 1 is an agricultural tractor that performs work on a farm field or the like while self-propelled. In the following description, the front-rear direction is a traveling direction when the work vehicle, that is, the tractor 1 is traveling straight, and the front side of the traveling direction is defined as “front” in the front-rear direction and the rear side is defined as “rear” in the front-rear direction To do. Here, the traveling direction of the tractor 1 is a direction from a cockpit 7 (to be described later) toward the steering handle 8 when the tractor 1 travels straight.

  The left-right direction is a direction that is horizontally orthogonal to the front-rear direction. Here, the left and right are defined toward the “front” side in the front-rear direction. That is, the left hand side is “left” and the right hand side is “right” when the operator has arrived at the cockpit 7 and turned forward. Further, the vertical direction is a direction orthogonal to the front-rear direction and the left-right direction. Therefore, the front-rear direction, the left-right direction, and the vertical direction are orthogonal to each other in three dimensions.

  As shown in FIG. 1, a tractor 1 as a work vehicle has an engine E mounted in a hood 2 at the front of the machine body. Rotational power from the engine E is transmitted to the traveling transmission device in the mission case 3, decelerated by the traveling transmission device, and transmitted to the wheels, that is, the front wheels 4 and the rear wheels 5 of the tractor 1.

  A cockpit 7 is provided in the cabin 6 at the rear of the aircraft. A steering handle 8 for steering the front wheels 4 is provided in front of the cockpit 7. A meter panel 9 is provided in front of the steering handle 8. The tractor 1 is connected to a rotary work machine or the like behind the machine body. Such a working machine is driven by a PTO shaft 111 protruding rearward from the mission case 3.

  Further, in the cabin 6, there are a steering handle 8, a meter panel 9, various operation pedals such as an accelerator pedal 10, a clutch pedal 11, a brake pedal 12, a forward / reverse lever 14, and a main transmission lever 15 around the cockpit 7. Various operation levers such as an auxiliary transmission lever (not shown) are provided. Note that details of various operation devices around the cockpit 7 will be described later with reference to FIGS. 5, 6, and 7.

  Next, a transmission mechanism (traveling transmission device) provided in the mission case 3 will be described with reference to FIG. FIG. 2 is a transmission path diagram in the mission case 3. As shown in FIG. 2, in the mission case 3, the rotational power of the output shaft 20 of the engine E on the upstream side of the power is transmitted to the input shaft 21.

  The rotational power input to the input shaft 21 is such that the first input gear 22 and the second input gear 23 of the input shaft 21 are the first low speed gear 26 of the first Hi-Lo clutch 24 and the second low speed of the second Hi-Lo clutch 25. By meshing with the first high-speed gear 30 of the gear 27 and the first Hi-Lo clutch 24 and the second high-speed gear 31 of the second Hi-Lo clutch 25, the power is transmitted to the downstream side.

  Here, the first Hi-Lo clutch 24 and the second Hi-Lo clutch 25 are the same hydraulic multi-plate clutch, and the first clutch shaft 28 reduces the rotational power of the input shaft 21 to high and low two stages at the same reduction ratio. And transmitted to the second clutch shaft 29.

  The rotational power of the low-speed transmission shaft 34 and the high-speed transmission shaft 32 is transmitted to the first sync change 42 and the second sync change 36, respectively, and the first sync small gear 43 and the second sync small gear 37 are transmitted to the first transmission shaft. When the first synchro large gear 44 and the second synchro large gear 38 are engaged with the sixth gear 41 of the first transmission shaft 39, the power is further transmitted to the downstream side.

  As a result, the rotational power of the input shaft 21 is shifted by the first transmission shaft 39 to four low speed stages and four high speed stages.

  The main transmission section of the tractor 1 (see FIG. 1) is configured by the transmission mechanism (multi-stage transmission 150) described above. In the main transmission unit, a shift position of the main transmission lever 15 (see FIG. 1) operated by the operator is detected, and a first Hi-Lo clutch 24 and a second Hi are automatically detected by a travel control unit 120 (see FIG. 11) described later. -By controlling the Lo clutch 25, the first sync change 42 and the second sync change 36, it is possible to shift from the low speed 4 speed to the high speed 4 speed.

  As shown in FIG. 2, the first transmission shaft 39 is connected to the second transmission shaft 45. The second transmission shaft 45 is provided with a seventh gear 46 and an eighth gear 47. Here, the seventh gear 46 and the eighth gear 47 mesh with the forward clutch gear 49 of the forward / reverse clutch (hereinafter referred to as “travel clutch”) 48 and the reverse gear 51 of the reverse shaft 52, and the reverse gear 51 The reverse clutch gear 50 is engaged.

  Therefore, when the traveling clutch 48 is connected to the forward rotation clutch gear 49, the rotational power of the first transmission shaft 39 is transmitted to the subtransmission shaft 53 connected to the traveling clutch 48 in the forward rotation state. When connected to the reverse clutch gear 50, it is transmitted to the auxiliary transmission shaft 53 in a reverse state.

  The auxiliary transmission shaft 53 is provided with a ninth gear 54 and a tenth gear 55. Here, the ninth gear 54 and the tenth gear 55 mesh with the third sync small gear 56 and the third sync large gear 59 of the third sync change 58, respectively.

  When the third sync change 58 is connected to the third sync small gear 56 side, the fifth transmission shaft 60 is increased at high speed by the rotational power transmitted from the ninth gear 54 to the third sync small gear 56. Driven by rotation.

  When the third sync change 58 is connected to the third sync large gear 59 side, the fifth transmission shaft 60 is decelerated by the rotational power transmitted from the tenth gear 55 to the third sync large gear 59. Driven at high speed.

  Further, when the third sync change 58 is in a neutral state, the rotational power of the tenth gear 55 is transmitted to the third sync large gear 59, and the fourth sync small from the eleventh gear 57 provided on the third sync large gear 59. It is transmitted to the gear 69.

  Further, when the fourth sync change 71 is connected to the fourth sync small gear 69 side, the rotational power of the fourth sync small gear 69 becomes the rotation of the sixteenth gear 74, thereby reducing the speed. Further, when the fourth sync change 71 is connected to the fourth sync large gear 72 side, the rotational power of the fourth sync small gear 69 is changed from the 15th gear 70 to the 17th gear 75, the 18th gear 76, the 4th synchro large gear. Transmission to the gear 72 causes the sixteenth gear 74 to be at a very low speed.

  Further, when the sixteenth gear 74 meshes with the twelfth gear 61 provided on the fifth transmission shaft 60, the fifth transmission shaft 60 is rotationally driven. Further, the first bevel gear 62 provided at the shaft end of the fifth transmission shaft 60 meshes with the second bevel gear 63 of the rear bevel gear case 64, and the 13th gear 66 and the 14th gear from the bevel output shaft 65 of the rear bevel gear case 64. The rear wheel output shaft 68 is driven to rotate through 67. Thereby, the rear wheel 5 is rotationally driven.

  The fifth transmission shaft 60 is provided with a 21st gear 117. The rotational power of the 21st gear 117 is transmitted to the 19th gear 77 of the first front wheel drive shaft 78 via the 22nd gear 118 and the 23rd gear 148 provided on the 3rd cylinder shaft 119 of the auxiliary transmission shaft 53, The low-speed 16-stage and high-speed 16-stage rotational power of the fifth transmission shaft 60 is transmitted to the first front wheel drive shaft 78.

  Further, the rotational power is transmitted from the first front wheel drive shaft 78 to the second front wheel drive shaft 85 via the front wheel acceleration clutch (hereinafter referred to as “4WD clutch”) 79, and the third front wheel drive shaft 86 and the fourth front wheel are transmitted. The signal is transmitted to the drive shaft 87 and the front wheel drive bevel shaft 88.

  A first front bevel gear 89 provided at the shaft end of the front wheel drive bevel shaft 88 meshes with the second front bevel gear 115 of the front bevel case 90, and the first front output bevel gear set 92 from the front bevel output shaft 91 of the front bevel case 90. The front wheel output shaft 94 is rotationally driven through the front wheel drive shaft 116 and the second front output bevel gear set 93. Thereby, the front wheel 4 is rotationally driven.

  Here, when the 4WD clutch 79 is connected to the front wheel constant speed gear 82 side, the rotational power of the first front wheel drive shaft 78 is transmitted to the second front wheel drive shaft 85 as it is, and normal four-wheel drive is performed. When the 4WD clutch 79 is connected to the front wheel speed increasing gear 84 side, the rotational power of the first front wheel drive shaft 78 is transferred from the front wheel constant speed gear 82 via the first speed increasing gear 81 and the second speed increasing gear 83. The increased rotational power is transmitted to the second front wheel drive shaft 85, and the front wheel double-speed four-wheel drive is performed. Further, when the 4WD clutch 79 is in a neutral state, the rotational power is not transmitted to the front wheels 4, so that the rear wheels 5 are driven by two wheels.

  As shown in FIG. 2, the second input gear 23 meshes with the main clutch gear 96 of the PTO clutch 97, whereby the rotational power is intermittently connected (connected / disconnected, that is, disconnected) to the PTO shaft 111 by the PTO clutch 97. It becomes like this.

  The first PTO shaft 95 is provided with a PTO transmission 157. The first PTO shaft 95 includes a first PTO gear 98, a fifth sync change 151, a fifth sync small gear 100, and a fifth sync large gear 101. The second PTO shaft 107 includes a twentieth gear 102, a twenty-fourth gear 152, a twenty-sixth gear 103, and a twenty-fifth gear 153, and a PTO reverse gear 105 is pivotally supported on the counter shaft 106.

  Here, when the first PTO gear 98 slides and meshes with the twentieth gear 102, the second PTO shaft 107 becomes the second speed. When the first PTO gear 98 slides and meshes with the second PTO gear 99, the rotational power of the first PTO shaft 95 is transmitted to the second PTO shaft 107 via the second PTO gear 99 and the 24th gear 152, and the second PTO shaft 107. Becomes the 4th speed.

  Further, when the fifth sync change 151 is connected to the fifth sync small gear 100, the rotational power of the fifth sync small gear 100 is transmitted to the 26th gear 103 to become the first speed. Further, when the fifth sync change 151 is connected to the fifth sync large gear 101, the rotational power of the fifth sync large gear 101 is transmitted to the 25th gear 153 to become the third speed. When the PTO reverse gear 105 meshes with the first PTO gear 98 and the twentieth gear 102, the rotational power of the first PTO shaft 95 is transmitted to the twentieth gear 102 via the first PTO gear 98 and the PTO reverse gear 105, and The rotation is transmitted to the second PTO shaft 107 and reversely rotated.

  The rotational power of the second PTO shaft 107 is transmitted to the fourth PTO shaft 108 via the third PTO shaft 156, and further decelerated by the first PTO output gear 109 and the second PTO output gear 110, so that the PTO shaft 111 is rotationally driven. .

  Here, the travel clutch 48 will be described in detail with reference to FIG. FIG. 3 is a schematic cross-sectional view of the traveling clutch 48. As described above, the traveling clutch 48 is a forward / reverse clutch, and transmits the rotational power of the first transmission shaft 39 (see FIG. 2) to the auxiliary transmission shaft 53 by rotating forward or backward.

  As shown in FIG. 3, the traveling clutch 48 includes a clutch shaft 48 a provided integrally with a forward clutch gear 49. The clutch shaft 48a is rotatably supported on the auxiliary transmission shaft 53 by the second bearing B1 and the third bearing B2. A plurality of inner clutch plates 48b are arranged behind the clutch shaft 48a. Furthermore, the clutch shaft 48a has a rear portion covered with a clutch case 48d, and a presser plate 48e provided inside the front portion of the clutch case 48d is disposed in front of the front ends of the plurality of inner clutch plates 48b. Yes.

  A plurality of outer clutch plates 48c are alternately arranged inside the clutch case 48d so as to be sandwiched between adjacent inner clutch plates 48b. Since the inner clutch plate 48b has a plurality of teeth on the inner side, it rotates integrally with the clutch shaft 48a, and the outer clutch plate 48c has a plurality of teeth on the outer side. It rotates together with the case 48d.

  In the clutch case 48d, a clutch piston 48f urged rearward by a spring 48g is provided behind the clutch shaft 48a. A space for a cylinder part 48h to which hydraulic oil is supplied is formed at the rear part of the clutch piston 48f. In the traveling clutch 48, when hydraulic oil is supplied to the cylinder portion 48h and the pressure of the supplied hydraulic oil exceeds the elastic force of the spring 48g, the clutch piston 48f moves forward, and the inner clutch plate 48b and the outer clutch plate 48c are pressed. Clamping is performed between 48e.

  The clamped inner clutch plate 48b and outer clutch plate 48c transmit power to each other by friction, and the rotational power transmitted from the forward clutch gear 49 is transmitted to the clutch case 48d, which is transmitted to the clutch case 48d. The auxiliary transmission shaft 53 fitted with the spline rotates.

  Further, in a state where hydraulic oil (pressure oil) is not supplied to the cylinder portion 48h and no pressure is applied, the clutch piston 48f is pushed rearward by the elastic force of the spring 48g, so that the inner clutch plate 48b and the outer clutch plate 48c. Is not pinched. In such a state, since the inner clutch plate 48b and the outer clutch plate 48c do not transmit power to each other, the PTO clutch 97 is in a state of interrupting power transmission, and even if the forward rotation clutch gear 49 rotates, the auxiliary transmission shaft 53 Does not rotate.

  A reverse clutch gear 50 is provided on the opposite side of the auxiliary transmission shaft 53 across the clutch case 48d, and the reverse-side power is transmitted (and cut off) in the same configuration as described above. The first Hi-Lo clutch 24, the second Hi-Lo clutch 25, and the 4WD clutch 79 have the same configuration as described above. Further, in the PTO clutch 97, the one-half configuration having the above-described configuration is used.

  Next, the hydraulic circuit of the tractor 1 will be described with reference to FIG. FIG. 4 is a hydraulic circuit diagram of the work vehicle (tractor 1). As shown in FIG. 4, in the tractor 1 (see FIG. 1), the main pump 250 and the sub pump 251 that are operated by the rotational power of the engine E (see FIG. 2) suck up the lubricating oil in the transmission case 3 through the suction filter 252. Pressure oil is supplied as hydraulic oil into the hydraulic circuit.

  The sub pump 251 supplies pressure oil to the power steering device 253. Thereby, the front wheel 4 (refer FIG. 2) is operated. The hydraulic oil discharged from the power steering device 253 is also used as oil for lubricating and cooling the first Hi-Lo clutch 24, the second Hi-Lo clutch 25, and the forward / reverse clutch (traveling clutch) 48, and the transmission case. 3 is returned.

  The main pump 250 supplies pressure oil to the work machine hydraulic device 254 and the traveling hydraulic device 255. The main pump 250 supplies pressure oil to the PTO system and the 2WD / 4WD switching system hydraulic device 258 in the traveling system hydraulic device 255 through a route separated from the route supplied to the traveling system hydraulic device 255. According to such a main pump 250, when the main speed change lever 15 (see FIG. 1) is operated to the first speed, for example, a current flows through the solenoid 207 of the first main speed change solenoids 207 and 208 to operate the valve. Then, the pressure oil is released from the Lo side oil chamber 256L of the first main transmission cylinder 256, and the first sync change 42 is connected to the first sync small gear 43 side (both see FIG. 2). Further, for example, a current flows through the solenoid 211a out of the first Lo-side solenoid 211a and the first Hi-side solenoid 211b, the valve operates, pressure oil is supplied to the Lo-side oil chamber of the first Hi-Lo clutch 24, and the first low speed It is connected to the gear 26 (see FIG. 2) side.

  When the main transmission lever 15 is operated from the first speed to the second speed, the first main change solenoid 207 remains in the same state, and the first sync change 42 is connected to the first sync small gear 43 side. The current supply to the 1Lo-side solenoid 211a is stopped, the current is supplied to the first Hi-side solenoid 211b, the respective valves are operated, the pressure oil is supplied to the Hi-side oil chamber of the first Hi-Lo clutch 24, the first 1 Connected to the high speed gear 30 side.

  Further, when the main transmission lever 15 is operated from the second speed to the third speed, the current supply to the first main transmission solenoid 207 is stopped, and for example, the current is supplied to the solenoid 209 of the second main transmission solenoids 209 and 210. The first sync change 42 is disconnected and the second sync change 36 is connected to the second sync small gear 37 (both see FIG. 2).

  Further, the current of the first Hi-side solenoid 211b stops, the current flows through the second Lo-side solenoid 212a, and the respective valves operate to supply pressure oil to the Lo-side oil chamber of the second Hi-Lo clutch 25. 2 Connected to the low-speed gear 27 side.

  Similarly, in the fourth speed, the second synchro small gear 37 and the second high speed gear 31 (see FIG. 2), and in the fifth speed, the first synchro large gear 44 and the first low speed gear 26 (see FIG. 2), the sixth speed. In the first synchro large gear 44 and the first high-speed gear 30 and the seventh speed, the second synchro large gear 38 and the second low-speed gear 27 (see FIG. 2), and in the eighth speed, the second synchro large gear 38 and the second gear. High speed gears 31 are connected to each other.

  During such a shift or when the tractor 1 starts, the clutch connection pressure is adjusted to suppress a shift shock or a shock at the start. When the forward / reverse lever 14 (see FIG. 1) is operated to move forward or backward, the operation position of the forward / reverse lever 14 is detected by the forward / reverse lever sensor, and a current flows to the forward switching solenoid 141F or the reverse switching solenoid 141R. The valve operates and the oil passage is selected.

  In the circuit configuration as illustrated in FIG. 4, the flow rate that determines the relief pressure of the forward / reverse relief valve 142a is adjusted according to the magnitude of the current flowing through the forward / reverse boost solenoid 142 that is a proportional solenoid. Thereby, the connection pressure of the traveling clutch 48 can be arbitrarily adjusted by arbitrarily adjusting the pressure of the forward and backward oil passage 142b.

  Next, various operation devices provided around the cockpit 7 will be described with reference to FIGS. 5, 6, and 7. FIG. 5 is an explanatory diagram of the operating device in front of the cockpit 7. FIG. 6 is an enlarged view of a portion A in FIG. FIG. 6 shows a case where the part A of FIG. 5 is viewed from right to left. FIG. 7 is an explanatory diagram of the operating device on the right side of the cockpit 7. Further, the types and arrangements of the operation devices shown in the drawings are examples, and are not limited to these.

  As shown in FIG. 5, the steering handle 8 is provided in front of the cockpit 7 (see FIG. 1) as described above. A clutch pedal 10 is provided on the lower left side of the handle post 350 to which the steering handle 8 is attached, and an accelerator pedal 11 and a brake pedal 12 are provided on the lower right side of the handle post 350. The brake pedal 12 includes left and right brake pedals 12L and 12R. The configuration of the left and right brake pedals 12L and 12R will be described later with reference to FIG.

  A forward / reverse lever 14 is provided on the upper left side of the handle post 350. As shown in FIGS. 5 and 6, an accelerator lever 351, a blinker lever 352, and a one-touch lift lever 353 are provided on the upper right side of the handle post 350. The one-touch lift lever 353 is used to operate the lift arm that connects the work machine to the machine body to the operation position or the uppermost position of the position lever 358 (see FIG. 7) with one touch. A PTO speed change lever 354 is provided at the center of the handle post 350.

  As shown in FIG. 5, a dashboard cover 355 is provided in front of the steering handle 8. The dashboard cover 355 is provided with a meter panel 9 so that it can be seen from the operator of the cockpit 7. The meter panel 9 is provided with a display unit (liquid crystal monitor) 356, an engine tachometer (tachometer) 357, and the like. The liquid crystal monitor 356 displays various displays such as a shift speed display that displays the current shift speed, a fuel consumption rate display, and a travel speed display, and the fuel consumption rate display and the travel speed display are switched at regular intervals. May be displayed.

  The meter panel 9 is provided with an energy saving monitor lamp (not shown). The energy saving monitor lamp is configured to be lit when a low fuel consumption engine output curve is selected with the engine mode selection switch 192 (see FIG. 6). For example, the energy saving monitor lamp is lit in green.

  As shown in FIG. 6, a travel / work changeover switch 223 and an engine mode selection switch 192 are provided on the right side of the dashboard cover 355. When the engine mode selection switch 192 is pressed, the engine E (see FIG. 2) is controlled with a low fuel consumption engine output curve.

  As shown in FIG. 7, operation levers such as a main transmission lever 15 and a position lever 358 are provided on the right side of the cockpit 7. The position lever 358 is for operating the lifting arm described above. Further, on the right side of the cockpit 7, a PTO on / off switch 221, a PTO automatic / manual switch 222, a shift sensitivity dial 135, an engine rotation instruction unit (constant rotation switch) 126, a rotation speed increase adjustment switch 123, a rotation speed decrease Operation switches such as an adjustment switch 124 are provided. Of the operation switches, the PTO automatic / manual switching switch 222 automatically shuts off the PTO clutch 97 (see FIG. 2) when the above-described lift arm rises to a certain level or higher. Further, an operation panel storage box 359 for storing an operation panel 206 (see FIG. 11) on which other operation switches and the like are disposed is provided to the right of the cockpit 7.

  Here, the lock mechanism 318 that locks the connection between the left and right brake pedals 12L and 12R and the left and right brake pedals 12L and 12R will be described with reference to FIGS. 8, 9, 10A, and 10B. FIG. 8 is a schematic perspective view of the left and right brake pedals 12L and 12R. FIG. 9 is an explanatory diagram of the pedal connection operation unit 310. 10A and 10B are explanatory diagrams of the operation of the lock mechanism 318. FIG. As described above, the brake pedal 12 includes the left and right brake pedals 12L and 12R that are operated to brake the left and right wheels (rear wheel 5), respectively.

  As shown in FIG. 8, the left and right brake pedals 12L, 12R are pivotally supported by a base shaft 300 extending in the left-right direction, and are provided at the distal ends of the arms 301, 301 extending downward. . The arms 301 and 301 are biased to the opposite side to the direction in which the operator steps on the base shaft 300 by biasing members 302 and 302 such as springs, respectively. Further, a pedal connecting portion 303 for connecting the left and right brake pedals 12L, 12R is provided in the middle of the arms 301, 301.

  The pedal connecting portion 303 includes a connecting piece 304 and a receiving portion 305. The connecting piece 304 is attached to an arm 301 provided with one of the left and right brake pedals (for example, the left brake pedal 12L) so as to be rotatable in a direction substantially orthogonal to the extending direction of the arm 301. The receiving portion 305 is provided on the arm 301 provided with the other brake pedal (for example, the right brake pedal 12R) of the left and right.

  The pedal connecting portion 303 connects the arms 301 and 301 by rotating the connecting piece 304 about the rotation axis and fitting the tip of the connecting piece 304 into the hook-shaped receiving portion 305. As described above, the arms 301 and 301 are connected by the pedal connecting portion 303, so that the left and right brake pedals 12L and 12R are substantially integrated, and operate together when the operator steps on. The operation of connecting the left and right brake pedals 12L and 12R and stepping on the left and right at the same time is used when the aircraft normally travels on the road or the like. On the other hand, the operation of releasing the connection between the left and right brake pedals 12L and 12R and individually depressing the brake pedals 12L and 12R is used when the vehicle is suddenly turned in a field or the like. In the following, a normal operation in which the operator depresses the brake pedals 12L and 12R at the same time in the state where the left and right brake pedals 12L and 12R are connected is referred to as a “brake operation”. It may be called “brake operation”.

  The connecting piece 304 of the pedal connecting portion 303 is connected to the wire 306. When the operator steps on the pedal connecting operation portion 310 (see FIG. 9), the connecting piece 304 is pulled up by the wire 306, and the left and right brake pedals 12L and 12R are connected. Unlink. When the operator removes his / her foot from the pedal connection operation portion 310, the pulling up of the connection piece 304 by the wire 306 is released, the connection piece 304 rotates and fits into the receiving portion 305, and the left and right brake pedals 12L and 12R are moved. Connected.

  The pedal connection operation unit 310 described above is provided to protrude toward the cockpit 7 at the lower part of the handle post 350 (see FIG. 5). As shown in FIG. 9, the pedal connection operation section 310 is provided with a pedal section 311 at the tip. In addition, the pedal connection operation unit 310 has a base end portion 312 that is rotatable, and can be stepped on by an operator. Further, the base end portion 312 of the pedal connection operation unit 310 has a first protrusion 313a protruding upward from the rotation center and a first protrusion 313a protruding upward from the rotation center by a predetermined angle. Two convex portions 313b are provided. The first protrusion 313a and the second protrusion 313b move in the rotation direction together with the pedal connection operation section 310 when the pedal connection operation section 310 rotates.

  A lock plate 315 is provided above the base end 312 of the pedal connection operation unit 310. The lock plate 315 is provided so as to be rotatable about a rotation shaft 316. Further, the lock plate 315 is connected to the lock lever 314 via the rod 317. Therefore, the lock plate 315 rotates around the axis of the rotation shaft 316 by operating the lock lever 314 up and down. The lock plate 315 operates the pedal connection operation unit 310 that releases the connection state of the left and right brake pedals 12L and 12R together with the first convex portion 313a of the pedal connection operation unit 310, the rod 317, the lock lever 314, and the like. A lock mechanism 318 is configured to lock in a disabled state.

  As shown in FIG. 10A, the lock mechanism 318 includes the first convex portion when the pedal connection operation unit 310 is not depressed by the operator, that is, when the pedal connection operation unit 310 is in the reference posture (substantially horizontal posture). 313a is in a state inclined at a predetermined angle around the base end 312. In this state, since the wire 306 is not pulled and the connecting piece 304 of the pedal connecting portion 303 is fitted in the receiving portion 305, the left and right brake pedals 12L and 12R are connected. At this time, if the lock lever 314 is fixed at the lowered position, the first convex portion 313a contacts the one end 315a of the lock plate 315 even if the operator tries to step on the pedal connection operation portion 310. The brake pedals 12L and 12R are not disconnected.

  As shown in FIG. 10B, when the lock lever 314 is raised, the lock plate 315 is rotated so that the pedal connection operation unit 310 can be depressed. When the pedal connection operation part 310 is stepped on by the operator, the wire 306 is pulled and the connection piece 304 of the pedal connection part 303 is pulled up. Thereby, the connection of the left and right brake pedals 12L and 12R is released.

  As shown in FIG. 9, a detection unit (pedal connection operation detection switch) 137 that detects a connection operation by the pedal connection operation unit 310 is provided in the vicinity of the pedal connection operation unit 310. Specifically, the pedal connection operation detection switch 137 is provided above the base end portion 312 of the pedal connection operation unit 310. When the pedal connection operation unit 310 rotates, the second convex portion 313b is moved accordingly. The actuator 137a is pressed against the second convex portion 313b, and the sensing portion 137b is pressed via the actuator 137a. Thereby, the operation of the pedal connection operation unit 310 can detect the connection / disconnection of the left and right brake pedals 12L and 12R. In the example of FIG. 9, when the pedal connection operation unit 310 is in the basic posture (substantially horizontal posture), the pedal connection operation detection switch 137 is pressed, and the pedal connection unit 303 connects the left and right brake pedals 12L and 12R. To detect. Further, when the pedal connection operation unit 310 is in the tilted posture, the connection release of the left and right brake pedals 12L and 12R by the pedal connection unit 303 is detected.

  As shown in FIG. 9, a lock operation detection unit (lock operation detection switch) 138 that detects the rotation operation of the lock plate 315 is provided in the vicinity of the lock plate 315. Specifically, the lock operation detection switch 138 is provided above the lock plate 315, and when the lock plate 315 rotates, the projection 319 provided on the upper portion of the lock plate 315 is moved at a predetermined angle. The actuator 138a is pressed against the convex portion 319, and the sensing unit 138b is pressed via the actuator 138a. Thereby, the lock / unlock described above can be detected by the lock mechanism 318. In the example of FIG. 9, when the lock lever 314 is lowered, the lock of the pedal connecting portion 303 is detected. In addition, when the lock lever 314 is raised, the lock operation detection switch 138 is pressed, and the unlocking of the pedal connecting portion 303 is detected.

  Next, an example of the control configuration of the control unit (travel control unit) 120 of the tractor 1 will be described with reference to FIG. FIG. 11 is a block diagram of the control unit 120. As shown in FIG. 11, as the control unit, the travel control unit 120 includes an engine control unit 121 that controls the engine E (see FIG. 2) and the like, and a work machine lifting control unit that lifts and lowers the work machine mounted on the PTO coupling device. 122, the meter panel 9, the operation panel 206, and the like are connected so as to be able to communicate with each other alternately via CAN communication lines (CAN1 and CAN2 in FIG. 11).

  The engine control unit 121 includes the engine mode selection switch 192 to the engine mode, the engine exhaust temperature sensor 203 to the exhaust temperature, the engine rotation sensor 125 to the engine speed, the engine oil pressure sensor 193 to the engine lubricating oil pressure, the engine The temperature of the cooling water from the water temperature sensor 194, the pressure of the common rail of the engine E from the rail pressure sensor 198, the pedal operation position of the accelerator pedal 10 (see FIG. 5) and the operation position of the accelerator lever 351 from the accelerator operation position detection sensor 195, respectively. Entered. The engine control unit 121 also includes a high-pressure fuel pump 196 that pressurizes and pumps fuel pumped from the fuel tank to the common rail, and each high-pressure injector 197 that injects high-pressure fuel accumulated in the common rail into the cylinder of the engine E. Outputs a control signal for operation.

  The work implement lift control unit 122 includes an operation signal for the position control sensor 199 provided on the position lever 358, a lift signal for the lift arm sensor 200, a lift position restriction signal for the lift position restriction dial 201, and a drop speed adjustment dial. 202 descent speed setting signals are input. Further, the work implement lifting / lowering control unit 122 outputs a work implement lifting / lowering signal to the main raising solenoid 204 and the main lowering solenoid 205 to operate the working implement raising / lowering cylinder.

  The traveling control unit 120 controls the traveling of the tractor 1 by controlling the main transmission, the auxiliary transmission, the forward / reverse switching mechanism, the PTO output mechanism, the front wheel side power transmission mechanism, and the like. The travel control unit 120 receives a brake operation (or one-brake operation) signal for the left and right brake pedals 12L and 12R. Further, when the engine speed is instructed by the constant rotation switch 126, the rotation speed increase adjustment switch 123, and the rotation speed decrease adjustment switch 124, the traveling control section 120 displays the above-described display section (liquid crystal monitor) 356 (see FIG. 5). The engine speed displayed on the display is approximated to the actually measured engine speed, that is, the engine speed displayed on the engine tachometer (tachometer) 357 (see FIG. 5). A specific control method for approximating the engine speed instructed to rotate the engine and the actually measured engine speed will be described later with reference to FIGS. 16, 17 and 18.

  The traveling control unit 120 receives detection signals for the above-described connection / disconnection and the above-described lock / unlock detection from the pedal connection operation detection switch 137 and the lock operation detection switch 138, respectively. In addition, a brake depression signal is input from the brake depression detection switch 139, a traveling speed is input from the vehicle speed detection unit (vehicle speed sensor) 140, and an engine speed is input from the engine rotation sensor 125 to the traveling control unit 120.

  In addition, detection results of the forward clutch pressure sensor 128 and the forward / reverse lever operation position sensor 130 in the traveling clutch 48 are input to the traveling control unit 120, respectively. Further, the traveling control unit 120 detects from the main transmission lever position sensor 136 that detects the operation position of the main transmission lever 15 (see FIG. 7) and the auxiliary transmission position sensor 131 that detects the operation position of the auxiliary transmission lever. The result is entered. Furthermore, the temperature of the mission oil is input from the oil temperature sensor 133 to the travel control unit 120.

  Further, the traveling control unit 120 is provided around the cockpit 7 (see FIG. 1), detects a rotational speed of the PTO shaft 111, a PTO rotation sensor 220, a PTO on / off switch 221, a PTO automatic / manual switch 222, Each detection result is input from the travel / work switching switch 223. In addition, the traveling control unit 120 receives a setting signal output from an automatic clutch disengagement setting switch 134 that automatically disengages the traveling clutch 48 when the operator performs a one-brake operation. Furthermore, a sensitivity signal output from a shift sensitivity dial 135 that adjusts the shift sensitivity of the main shift lever 15 is input to the travel control unit 120.

  The traveling control unit 120 corresponds to the constant rotation switch 126 and the constant rotation switch 126 for executing the “constant rotation mode”, in which the engine rotation number is set to a predetermined rotation number specifically set by the operator. Setting signals from a rotation speed increase adjustment switch 123 and a rotation speed decrease adjustment switch 124 that adjust the increase / decrease of the predetermined engine rotation speed setting are input. It should be noted that two kinds of engine speeds of high and low (for example, 2600 [rpm] for high speed and 1600 [rpm] for low speed) are arbitrarily set by the rotational speed increase adjustment switch 123 and the rotational speed decrease adjustment switch 124. Remember.

  The travel control unit 120 includes a forward switching solenoid 141F that operates a clutch on the forward / reverse output first gear side in the traveling clutch 48, a reverse switching solenoid 141R that operates a clutch on the forward / rearward output second gear side, and forward and reverse travel. In order to reduce the shock at the time of switching, a forward / reverse pressure boosting solenoid 142 for controlling the hydraulic pressure when the traveling clutch 48 is operated is connected to output these control signals.

  The traveling control unit 120 is connected to a first main transmission first solenoid 207 and a first main transmission second solenoid 208 that operate the first main transmission shifter, and outputs these control signals. Further, the traveling control unit 120 is connected to the second main transmission first solenoid 209 and the second main transmission second solenoid 210 that operate the second main transmission shifter, and outputs these control signals.

  The travel control unit 120 also operates a first Lo-side solenoid 211a that operates the first Hi-Lo shift Lo side gear side clutch, and a first Hi-Lo shift Hi side gear side clutch in the first Hi-Lo shift clutch. The first Hi side solenoid 211b is connected to output these control signals. Further, the travel control unit 120 operates the second Lo-side solenoid 212a that operates the second Hi-Lo shift Lo side gear side clutch, and the second Hi-Lo shift Hi side gear side clutch in the second Hi-Lo shift clutch. The second Hi side solenoid 212b is connected to output these control signals.

  Further, the travel control unit 120 is connected to a 4WD solenoid 213 and a front wheel acceleration solenoid 214 that operate a 4WD clutch 79 (see FIG. 2), and a PTO clutch solenoid 216 that operates a PTO clutch 97 (see FIG. 2). These control signals are output. Furthermore, the travel control unit 120 is connected to a buzzer 215 that gives various warnings to the operator and outputs a control signal.

  When the travel control unit 120 controls the tractor 1 as described above, for example, based on the detection result of the main shift lever position sensor 136 or the like, the processing unit converts the computer program described above into such a processing unit. The tractor 1 is travel-controlled by reading into the memory incorporated in the vehicle and performing calculations, and controlling actuators such as the first Hi-side solenoid 211b according to the calculation results. In this case, the processing unit appropriately stores a numerical value in the middle of the calculation in the storage unit, and extracts the stored numerical value and executes the calculation.

  Next, with reference to FIG. 12, FIG. 13, FIG. 14, and FIG. 15, the timing control of each part in the brake control during the brake operation and the one-brake operation will be described. FIG. 12 is a timing chart of brake control when the left and right brake pedals 12L and 12R are connected. FIG. 13 is a timing chart of the brake control when the left and right brake pedals 12L and 12R are in the disconnected state. FIG. 14 is a timing chart of the brake control when the lock mechanism 318 is in the locked state. FIG. 15 is a timing chart of the brake control when the lock mechanism 318 is in the unlocked state. The control configuration shown in FIGS. 14 and 15 is different from the control configuration shown in FIGS. 12 and 13.

  As shown in FIG. 12, in a state where the left and right brake pedals 12L and 12R are connected, it outputs to the travel control unit 120 that the pedal connection operation detection switch 137 is in the ON state. Here, when the operator depresses the clutch pedal 10 and operates the forward / reverse lever 14 to the forward side with the clutch automatic cutoff setting switch 134 turned on, the forward / backward advance of the traveling clutch 48 is performed by the forward switching solenoid 141F. The first clutch side, that is, the front clutch is operated, and the hydraulic pressure of the front clutch is increased to the pressure P1 by the forward / reverse boost solenoid 142. At this time, the forward clutch pressure sensor 128 detects that the hydraulic pressure of the front clutch has increased to the pressure P1. In the example of FIG. 12, the traveling control unit 120 increases the hydraulic pressure of the front clutch immediately after the pedal operation of the clutch pedal 10 is released without increasing immediately after the forward / reverse lever 14 is switched to forward movement. . Then, the traveling control unit 120 causes the aircraft to travel forward at a speed corresponding to the pedal operation of the accelerator pedal 11 or the like.

  When the left and right brake pedals 12L and 12R are simultaneously depressed (normal) and a brake operation is performed (ON state), the hydraulic pressure of the front clutch is reduced to the pressure P2 to stop the aircraft while preventing the engine stall. Thereafter, when the pedal operation of the brake pedals 12L and 12R is released (OFF state), the hydraulic pressure of the front clutch is increased from the pressure P2 to the pressure P1 according to the standard pattern, and the speed according to the pedal operation of the accelerator pedal 11 or the like. Etc. Advance the aircraft. Then, when the brake pedals 12L and 12R are operated again, the traveling control unit 120 stops the airframe while preventing the engine stall by reducing the hydraulic pressure of the front clutch to the pressure P2, and then the forward / reverse lever 14 becomes neutral. When switched, the hydraulic pressure of the front clutch is reduced to zero. The traveling control unit 120 increases the hydraulic pressure of the rear clutch to the pressure P2 when the forward / reverse lever 14 is switched to reverse, and the hydraulic pressure of the rear clutch when the pedal operation of the brake pedals 12L and 12R is released. Is increased to the pressure P1, and the aircraft is moved backward at a speed corresponding to the pedal operation of the accelerator pedal 11 or the like.

  Further, in a normal brake operation in which the left and right brake pedals 12L and 12R are connected, the traveling control unit 120 disconnects the traveling clutch 48 and increases the 4WD clutch 79 from two-wheel drive to four-wheel drive in order to improve braking performance. The “4WD switching mode” for switching is executed. At this time, when the “constant rotation mode” in which the engine speed is set to a predetermined rotation speed is being executed, the execution of the “constant rotation mode” is ended based on the detection of the brake operation. As shown in FIG. 12, when the travel / work changeover switch 223 is operated to switch to the “work mode”, four-wheel drive is always performed.

  As shown in FIG. 13, in a state where the left and right brake pedals 12L, 12R are disconnected, the fact that the pedal connection operation detection switch 137 has changed from the ON state to the OFF state is output to the travel control unit 120. Here, when the operator depresses the clutch pedal 10 and operates the forward / reverse lever 14 to the forward side while the clutch automatic cutoff setting switch 134 is ON, the hydraulic pressure (pressure) of the front clutch is reduced to the pressure P1. The aircraft is moved forward at a speed corresponding to the operation of the accelerator pedal 11 and the like. When the one-brake operation is performed (ON state), the traveling control unit 120 shuts off the traveling clutch 48 as in the above-described (normal) brake operation while keeping the hydraulic pressure of the front clutch at the pressure P1, and the 4WD clutch 79. The execution of the “4WD switching mode” for switching between and the end control of the “constant rotation mode” are not performed. Specifically, the traveling control unit 120 ignores the detection result of the brake depression detection switch 139, continues the connection state of the traveling clutch 48, and finishes control of the “4WD switching mode” and the engine “constant rotation mode”. Do not execute. In the example of FIG. 13, the continuation of the traveling clutch 48 and the non-execution of the “4WD switching mode” and the “constant rotation mode” end control are all performed, but at least one of these controls is performed. May be performed.

  Further, as shown in FIG. 14, a state in which the connection of the left and right brake pedals 12L and 12R cannot be released by the lock mechanism 318, that is, a lock state by the lock mechanism 318 (the lock operation detection switch 138 is OFF) is detected. When the brake operation is performed (ON state), the traveling control unit 120 performs normal brake control similar to the case of FIG. 12, that is, the traveling clutch 48 is disconnected, and the 4WD clutch 79 is moved from the two-wheel drive. The “4WD switching mode” for switching to four-wheel drive is executed, and the “constant rotation mode” end control is executed to set the engine speed to a predetermined speed.

  Further, as shown in FIG. 15, the lock mechanism 318 can release the connection between the left and right brake pedals 12L and 12R, that is, the lock release state by the lock mechanism 318 (the lock operation detection switch 138 is ON). If detected, when the brake operation is performed (ON state), the traveling control unit 120 performs the same normal brake control as that in FIG. 13, that is, the hydraulic pressure of the front clutch remains at the pressure P1 as described above. (Normal) Shut off the traveling clutch 48 such as a brake operation, execute the “4WD switching mode” for switching the 4WD clutch 79, and execute the end control for the “constant rotation mode” with the engine speed set to a predetermined speed. Do not do each. Specifically, the traveling control unit 120 ignores the detection result of the brake depression detection switch 139, continues the connection state of the traveling clutch 48, and performs the “4WD switching mode” and the engine “constant rotation mode” end control. Do not execute. In the example of FIG. 15 as well, the connection continuation of the traveling clutch 48 and the non-execution of the “4WD switching mode” and “constant rotation mode” end control are all performed, but at least one of these controls is controlled. May be performed.

  By performing the brake control as described above, it is possible to prevent the traveling clutch 48 from being disconnected due to the one-brake operation, and to prevent the vehicle (tractor 1) from being unintended by the operator. Thereby, operativity can be made favorable.

  In addition, the vehicle (tractor 1) can be steered as intended by the operator while avoiding switching of the four-wheel drive accompanying the one-brake operation. Thereby, operativity can be made favorable.

  In addition, it is possible to continue the operation before the one-brake operation by avoiding the stop of the predetermined rotation speed instruction of the engine E accompanying the one-brake operation. Thereby, operativity can be made favorable.

  In addition, when a connection release signal is input from the pedal connection operation detection switch 137, the travel control unit 120 detects the travel speed when a vehicle speed sensor 140 detects a travel speed of a predetermined speed (for example, 10 km / h) or more. For example, the liquid crystal monitor 356 of the panel 9 is controlled to display a warning notifying that the left and right brake pedals 12L and 12R are in the disconnected state. Furthermore, the traveling control unit 120 detects that the lock operation detection switch 138 detects unlocking by the lock mechanism 318 and the vehicle speed sensor 140 detects a traveling speed of a predetermined speed (for example, 10 km / h) or more. Control is performed so as to display, for example, a warning notifying that the lock is released on the liquid crystal monitor 356 of the meter panel 9.

  By displaying a warning when the traveling speed is equal to or higher than a predetermined speed in the brake control as described above, it is possible to alert the operator who performs the one-brake operation. Thereby, safety can be improved.

  Next, engine control by the travel control unit 120 and the engine control unit 121 will be described with reference to FIGS. 16 and 17. FIG. 16 is an explanatory diagram of the relationship between the rotational speed and the torque in normal engine control. FIG. 17 is an explanatory diagram of an example of the relationship between the rotational speed and the torque in the engine control of the present embodiment. FIG. 16 shows a comparative example of the present embodiment (example of FIG. 17). In the following description, the travel control unit 120 or the engine control unit 121 controls each unit shown in FIG. 11 and the like, and the travel control unit 120 rotates the engine based on the instruction value set by the operator. Specify the number.

  As shown in FIG. 16, in normal engine control, the engine speed is instructed by operating the accelerator lever 351 and the accelerator pedal 11 (both see FIG. 5) (see (a) in the figure). Here, when a load is applied to the engine E (see FIG. 2), the engine speed decreases (see (b) in the figure). When the engine speed decreases, when maintaining the engine speed, the fuel injection amount is increased to increase the torque (see (c) in the figure). In particular, when working using a working machine, it is possible to work more uniformly with a constant engine speed for driving the PTO shaft 111 (see FIG. 2). When the fuel injection amount exceeds a prescribed torque curve (the load factor described above exceeds 100%), no further fuel injection is performed, and therefore the engine speed gradually decreases ((d) in the figure). reference).

  Here, if the control (isochronous control) is performed so as to automatically adjust the fuel injection amount when the load increases and maintain the rotational speed (isochronous control), the rotation of the PTO shaft 111 can be made constant. Since the engine noise also increases, the operator may feel uncomfortable. By performing control (droop control) so that the engine speed gradually decreases as the load increases, the operator can operate the aircraft without feeling such a sense of incongruity. However, as described above, in the droop control, the engine speed is adjusted by the engine control unit 121. Therefore, the engine rotation value indicated by the operator may differ from the actual engine speed. The engine operation with the accelerator lever 351 or the accelerator pedal 10 indicates the engine speed with a sense, so it is difficult to feel uncomfortable due to the difference in the speed. However, in the “constant speed mode” described above, the operator numerically sets the engine speed. Since the instruction value displayed on the display unit 356 is different from the actual engine speed displayed on the tachometer 357, an uncomfortable feeling may be felt. Therefore, in the present embodiment, the error between the engine speed instruction value set by the operator and the actual engine speed (actually measured engine speed) is minimized.

  In order to execute the droop control described above, the engine control unit 121 adjusts the engine speed based on a predetermined adjustment coefficient D and the load factor L of the engine E. As shown in FIG. 17, in the conventional engine control example C3 in which the engine speed instruction value Ni is not corrected by the travel control unit 120, the operator operates the engine rotation instruction unit (constant rotation switch) 126 (see FIG. 7). When the command value Ni (for example, Ni = 2600 [rpm]) is set by (see (e) in the figure), the command value Ni is output from the travel control unit 120 to the engine control unit 121. The engine control unit 121 adjusts the engine speed based on a predetermined adjustment coefficient D when the load factor at which the traveling clutch 48 is disconnected is 0% (see (f) in the figure). For example, when the adjustment coefficient D = 0.05 (5%), the value obtained by increasing the indicated value Ni by 5% is set to the adjusted engine speed Nf (Nf = Ni + Nd = Ni (1 + D−L × D: adjustment value Nd). = Ni (1 + D−L × D), engine load factor L = 0) = 2600 [rpm] × 1.05 = 2730 [rpm]), the engine control unit 121 sets the engine control.

  Further, in the first engine control example C1 of the present embodiment, when the engine load factor is 0%, the adjusted engine speed (adjusted value Nf) matches the indicated value Ni (Nf = Ni). The correction instruction value Ni ′ is calculated by back-calculating from the above formula of Nf (for example, Nf = Ni = Ni ′ (1 + D), Ni ′ = Ni / (1 + D) = 2600 [rpm] /1.05=2476 [ rpm]) (see (g) in the figure). The correction instruction value Ni ′ is calculated by the travel control unit 120 and output to the engine control unit 121. Then, the engine speed after adjustment is calculated based on the corrected instruction value Ni ′ (see (h) in the figure). At this time, if the load factor is 0%, it substantially matches the instruction value Ni set by the operator. (Nf = Ni (1 + D) = 2476 [rpm] × 1.05≈2600 [rpm]).

  Furthermore, the traveling control unit 120 controls the instruction value Ni to be displayed on the liquid crystal monitor 356 (see FIG. 5).

  By performing such engine control, the engine speed indication value Ni displayed on the liquid crystal monitor 356 and the actually measured value of the engine speed displayed on the tachometer 357 (see FIG. 5) can be substantially matched. it can. Accordingly, the operator can perform an operation without a sense of incongruity because the engine speed (indicated value Ni) instructed by the operator substantially matches the actually measured engine speed (actually measured value). Thereby, operability can be improved.

  Next, another example of engine control will be described with reference to FIG. FIG. 18 is an explanatory diagram of another example of the rotational speed-torque relationship in engine control. In order to execute control in the second engine control example C2, which is another example of engine control of the present embodiment, the engine control unit 121 calculates an engine load factor and outputs the calculation result to the travel control unit 120. To do. Further, the travel control unit 120 calculates the correction instruction value Ni ′ by further using the load factor L of the engine E in the calculation formula of the correction instruction value Ni ′ described above, and outputs the calculation result to the engine control unit 121.

  As shown in FIG. 18, in the conventional engine control example C3 in which the engine speed instruction value Ni is not corrected by the travel control unit 120, the operator operates the engine rotation instruction unit (constant rotation switch) 126 (see FIG. 7). When the instruction value Ni (for example, Ni = 2600 [rpm]) is set by (see (h) in the figure), for example, in a state where the engine E is under load, such as when traveling, The engine speed is adjusted as a function of the load factor L (see (i) in the figure). Here, for example, when the load factor L = 0.5 (50%), the value obtained by increasing the indicated value Ni by 2.5% is set to the adjusted engine speed Nf (Nf = Ni + Nd = 2600 [rpm] + 65 = 2665 [rpm]: Adjustment value Nd = Ni (DL × D) = 2600 [rpm] (0.05−0.025) = 65) is set by the engine control unit 121, and then the engine is controlled.

  In the second engine control example C2, which is another example of the engine control of the present embodiment, the travel control unit 120 adds the predetermined adjustment coefficient D and the load factor L (for example, acquired by the engine control unit 121) , 50%), the corrected instruction value Ni ′ is calculated and output to the engine control unit 121 (Nf = Ni = Ni ′ (1 + D−L × D), Ni ′ = Ni / (1 + D−L × D) = 2600 [rpm] / (1.05-0.05 × L)) = 2600 [rpm] /1.025≈2537 [rpm]) (see (j) in the figure). Thus, the engine speed Nf after adjustment is calculated based on the corrected instruction value Ni ′, and substantially matches the instruction value Ni set by the operator even when the engine E is under load ((k in the figure)). )reference).

  Furthermore, the traveling control unit 120 controls the instruction value Ni to be displayed on the liquid crystal monitor 356 (see FIG. 5).

  As described above, when the engine control unit 121 is instructed by the corrected instruction value Ni ′ reflecting the load factor L of the engine E obtained in real time, the engine E is under load when it is running. Even when the engine speed is instructed, the engine speed instruction value Ni displayed on the liquid crystal monitor 356 can be approximated to the engine speed actual value displayed on the tachometer 357 (see FIG. 5). Therefore, even when the engine E is loaded, such as when the operator is running, the engine rotational speed (instructed value Ni) instructed by the operator and the actually measured engine rotational speed (actually measured value) substantially coincide with each other. The operation can be performed. Thereby, operability can be improved.

  Further effects and modifications can be easily derived by those skilled in the art. Thus, the broader aspects of the present invention are not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications can be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

1 Work vehicle (tractor)
3 Mission Case 4 Front Wheel 5 Rear Wheel 6 Cabin 7 Pilot's Seat 8 Steering Handle 9 Meter Panel 10 Clutch Pedal 11 Accelerator Pedal 12 Brake Pedal 12L Left Brake Pedal 12R Right Brake Pedal 14 Forward / Reverse Lever 15 Main Shift Lever 48 Forward / Reverse Clutch (Travel clutch)
79 Front wheel speed increasing clutch (4WD clutch)
120 control unit (running control unit)
REFERENCE SIGNS LIST 121 engine control unit 122 work implement lifting control unit 123 rotation speed increase adjustment switch 124 rotation speed decrease adjustment switch 125 engine rotation sensor 126 constant rotation switch (engine rotation instruction unit)
137 Pedal connection operation detection switch (detector)
138 Lock operation detection switch (Lock operation detection unit)
140 Vehicle speed sensor (vehicle speed detector)
222 PTO automatic / manual changeover switch 223 travel / work changeover switch 300 base shaft 301 arm 302 urging member 303 pedal connecting portion 304 connecting piece 305 receiving portion 306 wire 310 pedal connecting operation portion 311 pedal portion (tip portion)
312 Base end portion 313a First convex portion 313b Second convex portion 314 Lock lever 315 Lock plate 315a One end portion 315b Other end portion 316 Rotating shaft 317 Rod 318 Lock mechanism 319 Convex portion 356 Liquid crystal monitor (display unit)
357 Tachometer (Engine tachometer)
D Adjustment factor L Load factor Nd Adjustment value Nf Engine speed after adjustment Ni instruction value Ni 'Correction instruction value

Claims (2)

Left and right brake pedals operated respectively when braking left and right wheels,
A pedal connecting portion for connecting the left and right brake pedals;
A pedal coupling operation unit that is operated when the left and right brake pedals are coupled / uncoupled by the pedal coupling unit;
When the brake pedal is operated during two-wheel drive, a control unit that controls the 4WD clutch to switch to four-wheel drive;
A 4WD clutch that switches to either two-wheel drive or four-wheel drive;
A lock mechanism for locking / unlocking the pedal connecting portion in a state where the left and right brake pedals are connected;
A lock operation detector for detecting an operation of the lock mechanism;
With
The controller is
A work vehicle characterized by ignoring switching of the 4WD clutch even when the brake pedal is operated when unlocking by the lock mechanism is detected by the lock operation detection unit. The controller is
When the brake pedal is operated, it controls to disengage the travel clutch,
2. The work vehicle according to claim 1, wherein when the unlocking by the lock mechanism is detected by the lock operation detection unit, the disengagement of the travel clutch is ignored even if the brake pedal is operated.

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