JP6756391B2 - Work vehicle - Google Patents

Description

The present invention relates to a work vehicle.

Traditionally, work vehicles such as agricultural tractors have left and right brake pedals that correspond to wheels (eg, 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 at the same time, and is released from the connection when used to brake the left and right wheels individually.

Further, there is a technique for detecting the depression of the brake pedal and automatically shutting off the traveling clutch to prevent the engine from stall when the depression of the brake pedal is detected (see, for example, Patent Document 1).

JP-A-2015-067093

However, in the conventional work vehicle as described above, the traveling clutch may be disengaged even when the so-called one-sided brake operation in which one of the left and right brake pedals is depressed, and the vehicle may stop against the intention of the operator. As described above, the conventional work vehicle has room for improvement in operability.

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

In order to solve the above-mentioned problems and achieve the object, the work vehicle according to claim 1 is
The left and right brake pedals that are operated when braking the left and right wheels,
A pedal connecting portion that connects the left and right brake pedals,
A pedal connecting operation unit operated when connecting / disconnecting the left and right brake pedals by the pedal connecting unit,
A 4WD clutch that switches between two-wheel drive and four-wheel drive,
An engine rotation speed indicator that instructs the engine speed to reach the set predetermined speed,
When the brake pedal is operated during two-wheel drive, the 4WD clutch is controlled to be switched to four-wheel drive, and when the brake pedal is operated while the engine rotation speed is instructed by the engine rotation instruction unit, the brake pedal is operated. A control unit that controls to stop the rotation speed instruction,
A lock mechanism that locks / unlocks the pedal connection operation unit with the left and right brake pedals connected.
A lock operation detection unit that detects the operation of the lock mechanism,
With
The control unit
When the lock operation detection unit detects the unlocking by the lock mechanism, even if the brake pedal is operated, the switching of the 4WD clutch and the cancellation of the rotation speed instruction are ignored .

The work vehicle according to claim 2 is the work vehicle according to claim 1, and the control unit is
When the brake pedal is operated, it is controlled to disengage the traveling clutch.
When the lock operation detection unit detects the unlocking by the lock mechanism, even if the brake pedal is operated, the interruption of the traveling clutch is ignored.

According to the work vehicle according to claim 1, when unlocking by the lock mechanism is detected, when one-sided brake operation is performed, switching of the 4WD clutch due to the brake operation is avoided, as the operator intends. Can be steered. Thereby, the operability can be improved. Further, since it is possible to avoid the suspension of the predetermined rotation speed instruction of the engine E due to the one-brake operation and continue the work before the one-brake operation, the operability can be improved.

According to the work vehicle according to claim 2, when the unlocking by the lock mechanism is detected, the operator unintentionally stops by avoiding the interruption of the traveling clutch due to the brake operation when the one-side brake operation is performed. Can be prevented. Thereby, the operability can be improved.

FIG. 1 is a schematic left side view of the work vehicle. FIG. 2 is a transmission route diagram in the mission case. FIG. 3 is a schematic plan sectional view of the forward / backward clutch. FIG. 4 is a hydraulic circuit diagram of the work vehicle. FIG. 5 is an explanatory view of the operating device in front of the cockpit. FIG. 6 is an enlarged view of part A in FIG. FIG. 7 is an explanatory view 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 view of the pedal connection operation unit. FIG. 10A is an operation explanatory view (No. 1) of the lock mechanism. FIG. 10B is an operation explanatory view (No. 2) of the lock 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 the disconnected state. FIG. 14 is a timing chart of brake control in the locked state by the lock mechanism. FIG. 15 is a timing chart of brake control in the unlocked state by the lock mechanism. FIG. 16 is an explanatory diagram of the rotation speed-torque relationship in normal engine control. FIG. 17 is an explanatory diagram of an example of the rotation speed-torque relationship in engine control. FIG. 18 is an explanatory diagram of another example of the rotation speed-torque relationship in engine control.

Hereinafter, embodiments of the work vehicle disclosed in the present application will be described in detail with reference to the accompanying drawings. The present invention is not limited to the embodiments shown below.

FIG. 1 is a schematic left side view of the work vehicle. In the following, the tractor 1 will be described as an example of the work vehicle. The tractor 1 is an agricultural tractor that works in a field or the like while self-propelled. Further, in the following description, the front-rear direction is defined as the traveling direction of the work vehicle, that is, the tractor 1 when 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 the driver's seat 7, which will be described later, toward the steering steering wheel 8 when the tractor 1 goes straight.

The left-right direction is a direction 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, when the operator arrives at the driver's seat 7 and faces forward, the left hand side is "left" and the right hand side is "right". Further, the vertical direction is a direction orthogonal to the front-back direction and the left-right direction. Therefore, the front-back direction, the left-right direction, and the vertical direction are orthogonal to each other in three dimensions.

As shown in FIG. 1, the tractor 1 as a work vehicle has an engine E mounted in a bonnet 2 at the front of the machine body. The rotational power from the engine E is transmitted to the traveling transmission device in the transmission 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 fuselage. A steering handle 8 for steering the front wheels 4 is provided in front of the driver's seat 7. A meter panel 9 is provided in front of the steering wheel 8. A rotary work machine or the like is connected to the rear of the tractor 1. Such a work machine is driven by a PTO shaft 111 projecting rearward from the mission case 3.

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

Next, with reference to FIG. 2, a transmission mechanism (traveling transmission device) provided in the mission case 3 will be described. FIG. 2 is a transmission route 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 engaging with the gear 27, the first high-speed gear 30 of 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 rotational power of the input shaft 21 is reduced to two stages of high and low at the same reduction ratio, respectively, and the first clutch shaft 28 And to the second clutch shaft 29.

Further, the rotational power of the low-speed transmission shaft 34 and the high-speed transmission shaft 32 is transmitted to the first synchronization change 42 and the second synchronization change 36, respectively, and the first synchronization small gear 43 and the second synchronization small gear 37 are the first transmission shafts. The first synchro large gear 44 and the second synchro large gear 38 mesh with the fifth gear 40 of the first transmission shaft 39, and are further transmitted to the downstream side of the power by engaging with the sixth gear 41 of the first transmission shaft 39.

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

The transmission mechanism (multi-speed transmission 150) described above constitutes the main transmission unit of the tractor 1 (see FIG. 1). The main speed change unit detects the shift position of the main speed change lever 15 (see FIG. 1) operated by the operator, and the traveling control unit 120 (see FIG. 11), which will be described later, automatically detects the first Hi-Lo clutch 24 and the second Hi. -The Lo clutch 25, the first synchro change 42 and the second synchro change 36 are controlled to enable shifting from low speed 4 speeds to high speed 4 speeds.

As shown in FIG. 2, the first transmission shaft 39 is connected to the second transmission shaft 45. Further, the second transmission shaft 45 is provided with a seventh gear 46 and an eighth gear 47. Here, the 7th gear 46 and the 8th gear 47 mesh with the forward / reverse 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 further, the reverse gear 51 It meshes with the reverse clutch gear 50.

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

Further, 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 synchro small gear 56 and the third synchro large gear 59 of the third synchro change 58, respectively.

When the 3rd synchro change 58 is connected to the 3rd synchro small gear 56 side, the 5th transmission shaft 60 is accelerated by the rotational power transmitted from the 9th gear 54 to the 3rd synchro small gear 56 at high speed. It is driven to rotate.

Further, when the third synchro change 58 is connected to the third synchro large gear 59 side, the fifth transmission shaft 60 is decelerated by the rotational power transmitted from the tenth gear 55 to the third synchro large gear 59. It is driven to rotate at high speed.

When the third synchro change 58 is in the neutral state, the rotational power of the tenth gear 55 is transmitted to the third synchro large gear 59, and the eleventh gear 57 provided in the third synchro large gear 59 to the fourth synchro small It is transmitted to the gear 69.

Further, when the 4th synchro change 71 is connected to the 4th synchro small gear 69 side, the rotational power of the 4th synchro small gear 69 becomes the rotation of the 16th gear 74, so that the speed becomes low. Further, when the 4th synchro change 71 is connected to the 4th synchro large gear 72 side, the rotational power of the 4th synchro small gear 69 is changed from the 15th gear 70 to the 17th gear 75, the 18th gear 76, and the 4th synchro large. It is transmitted to the gear 72, and the 16th gear 74 becomes an ultra-low speed.

Further, when the 16th gear 74 meshes with the 12th gear 61 provided on the 5th transmission shaft 60, the 5th 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 bevel output shaft 65 to the thirteenth gear 66 and the fourteenth gear of the rear bevel gear case 64. The rear wheel output shaft 68 is rotationally driven via the 67. As a result, the rear wheels 5 are rotationally driven.

Further, 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 1st 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 rotational power of the fifth transmission shaft 60 at 16 low speeds and 16 high speeds 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 speed-up clutch (hereinafter referred to as “4WD clutch”) 79, and the third front wheel drive shaft 86 and the fourth front wheel It is transmitted to the drive shaft 87 and the front wheel drive bevel shaft 88.

The 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 front bevel output shaft 91 of the front bevel case 90 to the first front output bevel gear set 92. The front wheel output shaft 94 is rotationally driven via the front wheel drive shaft 116 and the second front output bevel gear set 93. As a result, the front wheels 4 are 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 directly transmitted to the second front wheel drive shaft 85, resulting in normal four-wheel drive. 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 transmitted 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, resulting in front wheel double speed four-wheel drive. Further, when the 4WD clutch 79 is in the 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, when the second input gear 23 meshes with the main clutch gear 96 of the PTO clutch 97, the PTO clutch 97 interrupts (connects / disconnects, that is, disconnects) the rotational power to the PTO shaft 111. Will be.

The first PTO shaft 95 is provided with a PTO transmission unit 157. Further, the first PTO shaft 95 has a first PTO gear 98, a fifth synchro change 151, a fifth synchro small gear 100, and a fifth synchro large gear 101. Further, the second PTO shaft 107 has a 20th gear 102, a 24th gear 152, a 26th gear 103, and a 25th gear 153, and the PTO reverse gear 105 is pivotally supported by the counter shaft 106.

Here, when the first PTO gear 98 slides and meshes with the 20th gear 102, the second PTO shaft 107 becomes the second gear. 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 4th gear.

Further, by connecting the 5th synchro change 151 to the 5th synchro small gear 100, the rotational power of the 5th synchro small gear 100 is transmitted to the 26th gear 103 to become the 1st gear. Further, by connecting the 5th synchro change 151 to the 5th synchro large gear 101, the rotational power of the 5th synchro large gear 101 is transmitted to the 25th gear 153 to become the 3rd gear. When the PTO reverse gear 105 meshes with the first PTO gear 98 and the 20th gear 102, the rotational power of the first PTO shaft 95 is transmitted to the 20th gear 102 via the first PTO gear 98 and the PTO reverse gear 105, and further. It is transmitted to the second PTO shaft 107 and becomes reverse rotation.

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

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

As shown in FIG. 3, the traveling clutch 48 includes a clutch shaft 48a integrally provided with the forward rotation clutch gear 49. The clutch shaft 48a is rotatably supported by the auxiliary transmission shaft 53 by the second bearing B1 and the third bearing B2. Further, a plurality of inner clutch plates 48b are arranged behind the clutch shaft 48a. Further, the rear portion of the clutch shaft 48a is covered with the clutch case 48d, and the pressing plate 48e provided inside the front portion of the clutch case 48d is arranged so as to be located in front of the front end of the plurality of inner clutch plates 48b. There is.

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, the inner clutch plate 48b rotates integrally with the clutch shaft 48a, and the outer clutch plate 48c has a plurality of teeth on the outer side. It rotates integrally 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 portion 48h to which hydraulic oil is supplied is formed at the rear portion of the clutch piston 48f. In the traveling clutch 48, hydraulic oil is supplied to the cylinder portion 48h, and when the pressure of the supplied hydraulic oil exceeds the elastic force of the spring 48g, the clutch piston 48f advances, and the inner clutch plate 48b and the outer clutch plate 48c are pressed. The pressure is sandwiched between 48e.

The pinched inner clutch plate 48b and the outer clutch plate 48c transmit power to each other by friction, and the rotational power transmitted from the forward rotation clutch gear 49 is transmitted to the clutch case 48d to the clutch case 48d. The sub-shift 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 backward 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 the power transmission, and even if the forward clutch gear 49 rotates, the auxiliary transmission shaft 53 Does not rotate.

A reverse clutch gear 50 is provided on the side opposite to the auxiliary transmission shaft 53 with the clutch case 48d interposed therebetween, and power on the reverse side is transmitted (and cut off) in the same configuration as described above. Further, also in the first Hi-Lo clutch 24, the second Hi-Lo clutch 25 and the 4WD clutch 79, those having the same configuration as described above are used. Further, in the PTO clutch 97, one having a structure of one half of the above-mentioned structure 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 a 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 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 in the hydraulic circuit.

The sub pump 251 supplies pressure oil to the power steering device 253. As a result, the front wheel 4 (see 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 is used as a transmission case. It is returned to the inside of 3.

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

Further, when the main speed change lever 15 is operated from the first speed to the second speed, the state of the first main speed change solenoid 207 remains unchanged, and the first synchro change 42 is connected to the first synchro small gear 43 side. The current supply to the 1Lo side solenoid 211a is stopped, a current is passed through the first Hi side solenoid 211b, each valve operates, pressure oil is supplied to the Hi side oil chamber of the first Hi-Lo clutch 24, and the first 1 Connected to the high speed gear 30 side.

When the main speed change lever 15 is operated from the second speed to the third speed, the current supply to the first main speed change solenoid 207 is stopped, and for example, the current is applied to the solenoid 209 of the second main speed change solenoids 209 and 210. As a result, the connection of the first synchro change 42 is cut off, and the second synchro change 36 is connected to the second synchro small gear 37 (both see FIG. 2).

Further, the current of the first Hi-side solenoid 211b is stopped, the current flows through the second Lo-side solenoid 212a, each valve operates, and the pressure oil is supplied 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 4th speed, the 2nd synchro small gear 37 and the 2nd high speed gear 31 (see FIG. 2), and in the 5th speed, the 1st synchro large gear 44 and the 1st low speed gear 26 (see FIG. 2), the 6th speed. Then, in the 1st synchro large gear 44 and the 1st high speed gear 30, the 2nd synchro large gear 38 and the 2nd low speed gear 27 (see FIG. 2) in the 7th speed, and in the 8th speed, the 2nd synchro large gear 38 and the 2nd The high speed gears 31 are respectively connected.

At the time of such shifting or when the tractor 1 is started, the clutch connection pressure is adjusted to suppress the shifting shock and the shock at the time of starting. When the forward / backward lever 14 (see FIG. 1) is operated forward or backward, the forward / backward lever sensor detects the operating position of the forward / backward lever 14, and a current flows through 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 / backward relief valve 142a is adjusted by the magnitude of the current flowing through the forward / backward boosting solenoid 142, which is a proportional solenoid. As a result, the connection pressure of the traveling clutch 48 can be arbitrarily adjusted by arbitrarily adjusting the pressure of the front-rear oil passage 142b.

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

As shown in FIG. 5, a steering handle 8 is provided in front of the cockpit 7 (see FIG. 1) as described above. Further, 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, respectively. The configurations of the left and right brake pedals 12L and 12R will be described later with reference to FIG.

A forward / backward lever 14 is provided on the upper left side of the handle post 350. Further, as shown in FIGS. 5 and 6, an accelerator lever 351 and a winker lever 352 and a one-touch elevating lever 353 are provided on the upper right side of the handle post 350. The one-touch lift lever 353 operates the lift arm that connects the work machine to the machine body with one touch to the operation position or the uppermost position of the position lever 358 (see FIG. 7). Further, a PTO shift lever 354 is provided in the center of the handle post 350.

As shown in FIG. 5, a dashboard cover 355 is provided in front of the steering wheel 8. Further, the dashboard cover 355 is provided with a meter panel 9 so as to be visible to the operator of the cockpit 7. Further, 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, for example, various displays such as a shift stage display for displaying the current shift stage, a fuel consumption rate display, and a running speed display, and the fuel consumption rate display and the running speed display are switched at regular intervals. May be displayed as.

Further, the meter panel 9 is provided with an energy-saving monitor lamp (not shown). The energy-saving monitor lamp is configured to light up when the fuel-efficient engine output curve is selected by the engine mode selection switch 192 (see FIG. 6), and is, for example, lit in green.

As shown in FIG. 6, a traveling / working 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 by the fuel-efficient engine output curve.

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

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 view of the pedal connection operation unit 310. 10A and 10B are operation explanatory views of the lock mechanism 318. As described above, the brake pedal 12 includes left and right brake pedals 12L and 12R that are operated when braking the left and right wheels (rear wheels 5), respectively.

As shown in FIG. 8, the left and right brake pedals 12L and 12R are rotatably supported by a base shaft 300 extending in the left-right direction, and are provided at the tip portions of the arms 301 and 301 extending downward. .. The arms 301 and 301 are urged by urging members 302 and 302 such as springs in the direction opposite to the direction in which the operator steps on the base shaft 300, respectively. Further, a pedal connecting portion 303 for connecting the left and right brake pedals 12L and 12R is provided at an intermediate position of the arms 301 and 301.

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

The pedal connecting portion 303 connects the arms 301 and 301 by rotating the connecting piece 304 around a rotation shaft and fitting the tip portion of the connecting piece 304 into the hook-shaped receiving portion 305. By connecting the arms 301 and 301 by the pedal connecting portion 303 in this way, the left and right brake pedals 12L and 12R are substantially integrated, and when the operator steps on them, they operate together. The operation of connecting the left and right brake pedals 12L and 12R and depressing the left and right at the same time is used when the aircraft is normally driven on a road or the like. On the other hand, the operation of disconnecting the left and right brake pedals 12L and 12R and depressing each of them individually is used when the aircraft is sharply turned in a field or the like. In the following, the normal operation in which the operator depresses the brake pedals 12L and 12R at the same time with the left and right brake pedals 12L and 12R connected is referred to as "brake operation", and the operation of depressing only one of the left and right is "one-sided". Sometimes called "brake operation".

Further, the connecting piece 304 of the pedal connecting portion 303 is connected to the wire 306, and when the operator steps on the pedal connecting operating 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. Break the connection. When the operator releases the foot from the pedal connecting operation unit 310, the wire 306 releases the pulling of the connecting piece 304, the connecting piece 304 rotates and fits into the receiving portion 305, and the left and right brake pedals 12L and 12R are moved. Be connected.

The pedal connecting operation unit 310 described above is provided at the lower part of the handle post 350 (see FIG. 5) so as to project toward the driver's seat 7. As shown in FIG. 9, the pedal connection operation unit 310 is provided with a pedal unit 311 at the tip end portion. Further, the pedal connecting operation unit 310 is provided with a base end portion 312 rotatably, so that the operator can step on the pedal. Further, the base end portion 312 of the pedal connecting operation unit 310 has a first convex portion 313a protruding upward from the rotation center and a first convex portion 313a protruding upward from the rotation center with a predetermined angle deviation from the first convex portion 313a. Two convex portions 313b are provided. When the pedal connecting operation unit 310 rotates, the first convex portion 313a and the second convex portion 313b move in the rotation direction together with the rotation.

Further, a lock plate 315 is provided above the base end portion 312 of the pedal connecting operation unit 310. The lock plate 315 is rotatably provided around a rotation shaft 316. Further, the lock plate 315 is connected to the lock lever 314 via a rod 317. Therefore, the lock plate 315 rotates around the rotation shaft 316 by operating the lock lever 314 up and down. Such a lock plate 315 operates the pedal connecting 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 connecting operation unit 310, the rod 317, the lock lever 314, and the like. It constitutes a lock mechanism 318 that locks in an impossible state.

As shown in FIG. 10A, the lock mechanism 318 has a first convex portion when the pedal connecting operation unit 310 is not depressed by the operator, that is, when the pedal connecting operation unit 310 is in the reference posture (substantially horizontal posture). The 313a is tilted by a predetermined angle about the base end portion 312. In this state, the wire 306 is not pulled, and the connecting piece 304 of the pedal connecting portion 303 is fitted into the receiving portion 305, so that 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, even if the operator tries to step on the pedal connecting operation unit 310, the first convex portion 313a comes into contact with the one end portion 315a of the lock plate 315, so that the left and right sides The connection of the brake pedals 12L and 12R of the above is not released.

As shown in FIG. 10B, when the lock lever 314 is raised, the lock plate 315 rotates and the pedal connection operation unit 310 can be stepped on. When the pedal connecting operation unit 310 is stepped on by the operator, the wire 306 is pulled and the connecting piece 304 of the pedal connecting unit 303 is pulled up. As a result, the left and right brake pedals 12L and 12R are disconnected.

Further, as shown in FIG. 9, a detection unit (pedal connection operation detection switch) 137 for detecting the 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, and when the pedal connection operation unit 310 rotates, the second convex portion 313b is moved accordingly. Rotating, the actuator 137a is pressed against the second convex portion 313b, and the sensing portion 137b is pressed via the actuator 137a. Thereby, the connection / disconnection of the left and right brake pedals 12L and 12R described above can be detected by operating the pedal connection operation unit 310. 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 left and right brake pedals 12L and 12R are connected by the pedal connection unit 303. To detect. Further, when the pedal connecting operation unit 310 is in the tilted posture, the pedal connecting unit 303 detects that the left and right brake pedals 12L and 12R are disconnected.

Further, as shown in FIG. 9, a lock operation detection unit (lock operation detection switch) 138 for detecting the rotational 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 convex portion 319 provided on the upper portion of the lock plate 315 has a predetermined angle. As it rotates, the actuator 138a is pressed against the convex portion 319, and the sensing portion 138b is pressed via the actuator 138a. As a result, the lock mechanism 318 can detect the above-mentioned lock / unlock. In the example of FIG. 9, when the lock lever 314 is lowered, the lock of the pedal connecting portion 303 is detected. Further, when the lock lever 314 is raised, the lock operation detection switch 138 is pressed to detect the unlocking of the pedal connecting portion 303.

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 a control unit, the travel control unit 120 is an engine control unit 121 that controls the engine E (see FIG. 2) and the like, and a work machine elevating control unit that raises and lowers the work machine mounted on the PTO coupling device. It is alternately and communicably connected to 122, the meter panel 9, the operation panel 206, and the like via a CAN communication line (CAN1, CAN2 in FIG. 11).

The engine control unit 121 includes the engine mode from the above-mentioned engine mode selection switch 192, the exhaust temperature from the engine exhaust temperature sensor 203, the engine rotation speed from the engine rotation sensor 125, the engine lubricating oil pressure from the engine oil pressure sensor 193, and 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) from the accelerator operation position detection sensor 195, and the operation position of the accelerator lever 351 are respectively. Entered. Further, the engine control unit 121 includes a fuel high-pressure pump 196 that pressurizes the fuel pumped from the fuel tank and pumps it to the common rail, and each high-pressure injector 197 that injects the high-pressure fuel accumulated in the common rail into the cylinder of the engine E. Outputs a control signal for operation.

The work equipment elevating control unit 122 includes an operation signal of the position control sensor 199 provided on the position lever 358, an elevating signal of the lift arm sensor 200, an elevating position regulating signal of the elevating position regulating dial 201, and a deceleration speed adjusting dial. The descent speed setting signal of 202 is input respectively. Further, the work equipment elevating control unit 122 outputs a work equipment elevating signal to the main ascending solenoid 204 and the main descending solenoid 205 to operate the working equipment elevating cylinder.

The travel control unit 120 controls the travel of the tractor 1 by controlling the main transmission, the auxiliary transmission, the forward / backward switching mechanism, the PTO output mechanism, the front wheel side power transmission mechanism, and the like. Brake operation (or one-side brake operation) signals of the left and right brake pedals 12L and 12R are input to the travel control unit 120. Further, when the traveling control unit 120 indicates the engine speed by the constant rotation switch 126, the rotation speed increase adjustment switch 123, and the rotation speed decrease adjustment switch 124, the above-mentioned display unit (liquid crystal monitor) 356 (see FIG. 5). Is instructed to approximate the engine speed displayed in the above to the 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 indicated by the engine speed and the actually measured engine speed will be described later with reference to FIGS. 16, 17, and 18.

The above-mentioned connection / release detection signal and the above-mentioned lock / unlock detection signal are input to the travel control unit 120 from the above-mentioned pedal connection operation detection switch 137 and the above-mentioned lock operation detection switch 138, respectively. Further, the travel control unit 120 is input with a brake depression signal from the brake depression detection switch 139, a travel speed from the vehicle speed detection unit (vehicle speed sensor) 140, and an engine rotation speed from the engine rotation sensor 125.

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

Further, the travel control unit 120 is provided around the driver's seat 7 (see FIG. 1), and has a PTO rotation sensor 220 that detects the rotation speed of the PTO shaft 111, a PTO on / off switch 221 and a PTO automatic / manual changeover switch 222. Each detection result is input from the travel / work changeover switch 223. Further, a setting signal output from the clutch automatic disengagement setting switch 134 for setting the traveling clutch 48 to be automatically disengaged when the operator operates one brake is input to the traveling control unit 120. Further, a sensitivity signal output from the shift sensitivity dial 135 for adjusting the shift sensitivity of the main shift lever 15 is input to the travel control unit 120.

Further, the traveling control unit 120 corresponds to a constant rotation switch 126 and a constant rotation switch 126 for executing a "constant rotation mode" in which the engine rotation speed is set to a predetermined rotation speed specifically set by the operator numerically. The setting signals from the rotation speed increase adjustment switch 123 and the rotation speed decrease adjustment switch 124 for adjusting the increase / decrease of the predetermined engine speed setting are input. Two types of engine speeds (for example, high speed is 2600 [rpm] and low speed is 1600 [rpm]) are arbitrarily set by the rotation speed increase adjustment switch 123 and the rotation speed decrease adjustment switch 124. Remember.

The travel control unit 120 includes a forward switching solenoid 141F that operates the clutch on the front / rear output first gear side of the traveling clutch 48, a reverse switching solenoid 141R that operates the clutch on the forward / backward output second gear side, and forward and reverse. In order to reduce the shock at the time of switching, the forward / backward step-up solenoid 142 that controls the hydraulic pressure when the traveling clutch 48 is operated is connected, and these control signals are output.

Further, the travel control unit 120 is connected to the first main shift first solenoid 207 and the first main shift second solenoid 208 for operating the first main shift shifter, and outputs these control signals. Further, the travel control unit 120 is connected to the second main shift first solenoid 209 and the second main shift second solenoid 210 for operating the second main shift shifter, and outputs these control signals.

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

Further, the traveling control unit 120 is connected to the 4WD solenoid 213 and the front wheel speed-increasing solenoid 214 for operating the 4WD clutch 79 (see FIG. 2) and the PTO clutch solenoid 216 for operating the PTO clutch 97 (see FIG. 2). , Output these control signals. Further, the travel control unit 120 is connected to a buzzer 215 that gives various alarms to the operator and outputs a control signal.

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

Next, the timing control of each part in the brake operation and the brake control at the time of one-sided brake operation will be described with reference to FIGS. 12, 13, 14 and 15. 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 brake control when the left and right brake pedals 12L and 12R are in the disconnected state. FIG. 14 is a timing chart of brake control in the locked state by the lock mechanism 318. FIG. 15 is a timing chart of brake control in the unlocked state by the lock mechanism 318. 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, when the left and right brake pedals 12L and 12R are connected, it is output to the traveling 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 / backward advance lever 14 to the forward side with the clutch automatic disengagement setting switch 134 turned on, the forward / backward switching solenoid 141F advances the traveling clutch 48 forward / backward. The force 1st gear side, that is, the front side clutch is operated, and the hydraulic pressure of the front side clutch is increased to the pressure P1 by the forward / backward step-up 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, in the traveling control unit 120, the hydraulic pressure of the front clutch does not increase immediately after the forward / backward lever 14 is switched to forward, but increases immediately after the pedal operation of the clutch pedal 10 is released. .. Then, the travel control unit 120 advances the aircraft at a speed or the like corresponding to the pedal operation of the accelerator pedal 11.

Then, when the left and right brake pedals 12L and 12R are simultaneously depressed (normally), the brake operation is performed (ON state), the hydraulic pressure of the front clutch is reduced to the pressure P2, and the aircraft is stopped while preventing engine stall. After that, 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 corresponding to the pedal operation of the accelerator pedal 11 or the like is increased. Move the aircraft forward with such means. Then, when the brake pedals 12L and 12R are operated again, the traveling control unit 120 reduces the hydraulic pressure of the front clutch to the pressure P2 to stop the aircraft while preventing engine stall, and then the forward / backward lever 14 becomes neutral. When switched, the oil 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 / backward lever 14 is switched to reverse, and when the pedal operation of the brake pedals 12L and 12R is released, the hydraulic pressure of the rear clutch Is increased to the pressure P1 and the aircraft is moved backward at a speed or the like corresponding to the pedal operation of the accelerator pedal 11.

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

As shown in FIG. 13, when the left and right brake pedals 12L and 12R are disconnected from each other, the pedal connection operation detection switch 137 is output to the traveling control unit 120 from the ON state to the OFF state. Here, when the operator depresses the clutch pedal 10 and operates the forward / backward lever 14 to the forward side with the clutch automatic disengagement setting switch 134 turned on, the hydraulic pressure (pressure) of the front clutch is increased to the pressure P1. It is increased to advance the aircraft at a speed or the like corresponding to the operation of the accelerator pedal 11. Then, when the one-side brake operation is performed (ON state), the travel control unit 120 shuts off the travel clutch 48 as in the above-mentioned (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" and the end control of the "constant rotation mode" are not performed. Specifically, the travel control unit 120 ignores the detection result of the brake depression detection switch 139, continues the connected state of the travel clutch 48, and controls the end of the "4WD switching mode" and the "constant rotation mode" of the engine. Do not execute. In the example of FIG. 13, the connection 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 controlled. May be done.

Further, as shown in FIG. 14, a state in which the left and right brake pedals 12L and 12R cannot be disengaged by the lock mechanism 318, that is, a locked state (lock operation detection switch 138 is OFF state) by the lock mechanism 318 is detected. If this is done, when the brake operation is performed (ON state), the travel control unit 120 shuts off the normal brake control as in the case of FIG. 12, that is, the travel clutch 48, and releases the 4WD clutch 79 from the two-wheel drive. The "4WD switching mode" for switching to four-wheel drive is executed, and the end control of the "constant rotation mode" in which the engine speed is set to a set predetermined speed is executed.

Further, as shown in FIG. 15, the state in which the left and right brake pedals 12L and 12R can be released by the lock mechanism 318, that is, the unlocked state by the lock mechanism 318 (the lock operation detection switch 138 is ON). If it is detected, when the brake operation is performed (ON state), the traveling control unit 120 performs the same normal brake control as in the case of FIG. 13, that is, the hydraulic pressure of the front clutch remains at the pressure P1 and described above. (Normal) Execution of "4WD switching mode" for shutting off the traveling clutch 48 and switching 4WD clutch 79, such as braking operation, and execution of end control of "constant rotation mode" in which the engine speed is set to a predetermined speed. Do not do each. Specifically, the travel control unit 120 ignores the detection result of the brake depression detection switch 139, continues the connected state of the travel clutch 48, and controls the end of the "4WD switching mode" and the "constant rotation mode" of the engine. Do not execute. In the example of FIG. 15, the connection 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 controlled. May be done.

By performing the brake control as described above, it is possible to avoid the interruption of the traveling clutch 48 due to the one-sided brake operation and prevent the operator from stopping the vehicle (tractor 1) unintentionally. Thereby, the operability can be improved.

In addition, it is possible to steer the vehicle (tractor 1) as the operator intends, avoiding switching of four-wheel drive due to one-brake operation. Thereby, the operability can be improved.

Further, it is possible to avoid the suspension of the predetermined rotation speed instruction of the engine E due to the one-brake operation and continue the work before the one-brake operation. Thereby, the operability can be improved.

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

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 call attention to the operator who operates one brake. As a result, safety can be enhanced.

Next, engine control by the traveling 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 rotation speed-torque relationship in normal engine control. FIG. 17 is an explanatory diagram of an example of the rotation speed-torque relationship in the engine control of the present embodiment. Note that FIG. 16 is shown as a comparative example of the present embodiment (example of FIG. 17). Further, in the following, 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 an instruction value set by the operator for the engine control unit 121. Indicate the number.

As shown in FIG. 16, in normal engine control, the engine speed is indicated 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, the fuel injection amount is increased to increase the torque when maintaining the engine speed (see (c) in the figure). In particular, when working with a working machine, it is possible to work more uniformly if the engine speed for driving the PTO shaft 111 (see FIG. 2) is constant. When the fuel injection amount exceeds the specified torque curve (the above-mentioned load factor exceeds 100%), the engine speed gradually decreases because no more fuel injection is performed ((d) in the figure). reference).

Here, if the fuel injection amount is automatically adjusted when the load increases and the control is performed so as to maintain the rotation speed (isochronous control), the rotation of the PTO shaft 111 can be made constant, but as the load increases. Since the engine noise is also loud, the operator may feel uncomfortable. By controlling the engine speed to gradually decrease as the load increases (droop control), the operator can operate the aircraft without feeling such a sense of discomfort. However, as described above, in the droop control, the engine speed is adjusted by the engine control unit 121, so that the indicated value of the engine speed specified by the operator may differ from the actual engine speed. Since the engine operation by the accelerator lever 351 and the accelerator pedal 10 indicates the engine speed with a sense, it is difficult to feel a sense of discomfort due to this difference in the speed, but in the above-mentioned "constant speed mode", the operator numerically indicates the engine speed. In order to give an instruction, the indicated value displayed on the display unit 356 and the actual engine speed displayed on the tachometer 357 are different, which may cause a sense of discomfort. Therefore, in the present embodiment, the error between the indicated value of the engine speed set by the operator and the actual engine speed (actually measured engine speed) is made as small as possible.

In order to execute the above-mentioned droop control, 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 traveling control unit 120 does not correct the indicated value Ni of the engine speed, the operator operates the engine rotation indicating unit (constant rotation switch) 126 (see FIG. 7). When the indicated value Ni (for example, Ni = 2600 [rpm]) is set by (see (e) in the figure), the indicated value Ni is output from the traveling control unit 120 to the engine control unit 121. When the load factor that disengages the traveling clutch 48 is 0%, the engine control unit 121 adjusts the engine speed based on a predetermined adjustment coefficient D (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 the adjusted engine speed Nf (Nf = Ni + Nd = Ni (1 + D−L × D: adjustment value Nd). The engine is controlled after being set by the engine control unit 121 as = Ni (1 + DL × D), engine load factor L = 0) = 2600 [rpm] × 1.05 = 2730 [rpm]).

Further, in the first engine control example C1 of the present embodiment, when the engine load factor is 0%, the adjusted engine speed (adjustment value Nf) matches the indicated value Ni (Nf = Ni). The correction instruction value Ni'is calculated by back calculation from the above Nf calculation formula (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 traveling control unit 120 and output to the engine control unit 121. Then, the adjusted engine speed is calculated based on the correction 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]).

Further, the traveling control unit 120 controls so that the indicated value Ni is displayed on the liquid crystal monitor 356 (see FIG. 5).

By performing such engine control, it is possible to substantially match the indicated value Ni of the engine speed displayed on the liquid crystal monitor 356 with the measured value of the engine speed displayed on the tachometer 357 (see FIG. 5). it can. Therefore, since the engine speed (indicated value Ni) instructed by the operator and the actually measured engine speed (measured value) are substantially the same, the operator can perform the operation without discomfort. 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 rotation speed-torque relationship in engine control. In order to execute the control in the second engine control example C2, which is another example of the engine control of the present embodiment, the engine control unit 121 calculates the engine load factor and outputs the calculation result to the travel control unit 120. To do. Further, the traveling control unit 120 calculates the correction instruction value Ni'by further using the load factor L of the engine E in the above-mentioned calculation formula of the correction instruction value Ni', 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 traveling control unit 120 does not correct the indicated value Ni of the engine speed, the operator operates the engine rotation instruction unit (constant rotation switch) 126 (see FIG. 7). When the indicated 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 loaded, such as during running, at that time. The engine speed is adjusted as a function of the load factor L of (see (i) in the figure). Here, for example, when the load factor L = 0.5 (50%), the indicated value Ni is increased by 2.5% and the adjusted engine speed Nf (Nf = Ni + Nd = 2600 [rpm] +65 = 2665 [rpm]: The engine is controlled after being set by the engine control unit 121 with the adjustment value Nd = Ni (DL × D) = 2600 [rpm] (0.05-0.025) = 65).

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

Further, the traveling control unit 120 controls so that the indicated value Ni is displayed on the liquid crystal monitor 356 (see FIG. 5).

In this way, by instructing with the correction instruction value Ni'that reflects the load factor L of the engine E obtained in real time from the engine control unit 121, the engine is loaded when the engine E is loaded, such as during running. Even when the rotation speed is instructed, the indicated value Ni of the engine rotation speed displayed on the liquid crystal monitor 356 can be approximated to the actually measured value of the engine rotation speed displayed on the tachometer 357 (see FIG. 5). Therefore, the operator does not feel uncomfortable because the engine speed (indicated value Ni) instructed by the operator and the actually measured engine speed (measured value) are substantially the same even when the engine E is loaded, such as while driving. You can perform operations. Thereby, operability can be improved.

Further effects and variations can be easily derived by those skilled in the art. For this reason, the broader aspects of the invention are not limited to the particular details and representative embodiments expressed and described as described above. Therefore, various modifications can be made without departing from the spirit or scope of the general concept of the invention 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 Driver'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 / backward lever 15 Main shift lever 48 Forward / reverse clutch (Running clutch)
79 Front wheel speed-up clutch (4WD clutch)
120 Control unit (travel control unit)
121 Engine control unit 122 Work equipment elevating control unit 123 Rotation speed increase adjustment switch 124 Rotation speed decrease adjustment switch 125 Engine rotation sensor 126 Constant rotation switch (engine rotation indicator)
137 Pedal connection operation detection switch (detection unit)
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 Biasing member 303 Pedal connection part 304 Connection piece 305 Receiving part 306 Wire 310 Pedal connection operation part 311 Pedal part (tip part)
312 Base end 313a 1st convex 313b 2nd convex 314 Lock lever 315 Lock plate 315a One end 315b Other end 316 Rotating shaft 317 Rod 318 Lock mechanism 319 Convex 356 LCD monitor (display)
357 Tachometer (engine tachometer)
D Adjustment coefficient L Load factor Nd Adjustment value Nf Adjusted engine speed Ni Instructed value Ni'Correction instructed value

Claims (2)

The left and right brake pedals that are operated when braking the left and right wheels,
A pedal connecting portion that connects the left and right brake pedals,
A pedal connecting operation unit operated when connecting / disconnecting the left and right brake pedals by the pedal connecting unit,
A 4WD clutch that switches between two-wheel drive and four-wheel drive,
An engine rotation speed indicator that instructs the engine speed to reach the set predetermined speed,
When the brake pedal is operated during two-wheel drive, the 4WD clutch is controlled to be switched to four-wheel drive, and when the brake pedal is operated while the engine rotation speed is instructed by the engine rotation instruction unit, the brake pedal is operated. A control unit that controls to stop the rotation speed instruction,
A lock mechanism that locks / unlocks the pedal connection operation unit with the left and right brake pedals connected.
A lock operation detection unit that detects the operation of the lock mechanism,
With
The control unit
When the lock operation detection unit detects unlocking by the lock mechanism, the work vehicle is characterized in that even if the brake pedal is operated, the switching of the 4WD clutch and the cancellation of the rotation speed instruction are ignored . The control unit
When the brake pedal is operated, it is controlled to disengage the traveling clutch.
The work vehicle according to claim 1, wherein when the lock operation detection unit detects the unlocking by the lock mechanism, the interruption of the traveling clutch is ignored even if the brake pedal is operated.

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