JP2012091541A5 - - Google Patents

Description

Work vehicle

  The present invention relates to a work vehicle technology.

2. Description of the Related Art Conventionally, work vehicles such as tractors are known that transmit the rotational power of an engine to a traveling device via a continuously variable transmission. The work vehicle includes an accelerator lever and an accelerator pedal which are engine speed setting means for setting the engine speed at a normal time.
In addition, a work vehicle that changes the vehicle speed according to an engine load expressed by an engine load factor, an engine down amount, a traction torque, or the like during work is also known. When the engine load is heavy (during heavy load), the vehicle speed is slowed to prevent engine stall. In addition, when the engine load is small (light load), the vehicle speed is increased to improve running performance.

JP 2007-315472 A

  However, even when the vehicle speed is slowed down during heavy load, engine stall may occur when the load is applied rapidly. In addition, when the vehicle speed is increased at light loads, the running performance is improved, but the engine speed is increased more than necessary, so the fuel efficiency cannot be improved.

Therefore, in view of the problem related to the present invention, at heavy load, by increasing the engine speed and decreasing the vehicle speed, engine stall can be prevented, work efficiency can be improved, and at light load, Provided is a work vehicle capable of traveling with low fuel consumption while suppressing an increase in engine speed.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

That is, in claim 1, the engine speed detecting means, the engine speed setting means, the engine speed changing actuator, the vehicle speed detecting means, the continuously variable transmission, and the speed change actuator for shifting the continuously variable transmission. And a control device that controls the engine speed and the vehicle speed, when the engine load becomes larger than the set heavy load value, the engine speed is maintained while maintaining the vehicle speed constant. When the engine load increases to the upper limit value of the engine speed and the engine load becomes larger than the set heavy load value, the engine speed change actuator and the speed change actuator are decreased so that the vehicle speed is decreased. When the engine load becomes smaller than the set light load value, the vehicle speed is kept constant. While so as to decrease the engine speed, but with a light load mode for controlling the shift actuator and the engine rotational speed change actuator.

  According to a second aspect of the present invention, there is provided change means capable of arbitrarily changing the change amount of the engine speed and the change amount of the vehicle speed in the heavy load mode and the light load mode.

  According to a third aspect of the present invention, there is provided operation means for performing on / off setting of control of the engine speed changing actuator by performing on / off setting for the heavy load mode or the light load mode.

  According to a fourth aspect of the present invention, the set heavy load value and the set light load value in the heavy load mode and the light load mode can be changed by a threshold setting means.

  According to a fifth aspect of the invention, there is provided setting means for setting the engine speed changing speed and the vehicle speed changing speed in the heavy load mode and the light load mode.

  According to a sixth aspect of the invention, there is provided display means for displaying the heavy load mode and the light load mode and displaying that the engine speed is increasing or decreasing or the vehicle speed is decreasing.

  As effects of the present invention, the following effects can be obtained.

  In claim 1, when the heavy load mode is selected during heavy load, engine stall can be prevented by increasing the engine speed by the engine speed change actuator and decreasing the vehicle speed by the speed change actuator. Efficiency can be improved. Further, when the light load mode is selected at the time of light load, the engine speed can be reduced by the engine speed change actuator, and the vehicle can travel with low fuel consumption.

  According to claim 2, the engine speed change amount and the vehicle speed change amount in each mode can be changed separately in accordance with the user's preference, work mode, and state of the field, thereby improving work efficiency. Can do.

  According to the third aspect of the present invention, the heavy load mode or the light load mode can be arbitrarily selected by turning on / off the operation means according to the user's preference.

  According to the fourth aspect of the present invention, the threshold value in each mode can be changed according to the user's preference, the work mode, and the state of the field, so that the work finish can be improved and the engine stall can be prevented.

  According to claim 5, the engine speed change speed and the vehicle speed change speed in each mode can be changed according to the user's preference, work mode, and state of the field, improving the work finish, Can be prevented.

  In the sixth aspect, the setting states of the heavy load mode and the light load mode can be easily confirmed.

1 is an overall side view of a tractor according to an embodiment of the present invention. The figure which shows the power transmission structure of a tractor. The block diagram which shows the structure which concerns on control of a tractor. The top view which shows an operation panel. The top view which shows a display part. The 1st flowchart figure which shows the control aspect of an engine speed and vehicle speed control. The 2nd flowchart figure which shows the control aspect of engine speed and vehicle speed control. The 3rd flowchart figure which shows the control aspect of engine speed and vehicle speed control. The 4th flowchart figure which shows the control aspect of engine speed and vehicle speed control. The 5th flowchart figure which shows the control aspect of engine speed and vehicle speed control. The graph which shows the relationship between load, an engine speed, a vehicle speed, and time. The graph which shows the relationship between engine speed and time at the time of engine speed upper limit change. The graph which shows the relationship between engine speed and time at the time of target engine speed change.

  Next, the whole structure of the tractor 1 which concerns on one Embodiment of this invention is demonstrated.

  As shown in FIG. 1, in the tractor 1, the body frame 2 is arranged with the longitudinal direction as the front-rear direction, and is supported by a pair of left and right front wheels 3, 3 via a front axle at the front part, and at the rear part. It is supported by a pair of left and right rear wheels 4, 4 via a rear axle. An engine 5 is provided at the front of the machine body frame 2 and is covered with a bonnet 6. A mission case 7 that houses a part of the power transmission mechanism of the tractor 1 is provided at the rear of the body frame 2.

  A cabin 8 is disposed behind the bonnet 6, and a driving operation unit 10 is provided inside the cabin 8 for an operator to board and operate the tractor 1. In the driving operation unit 10, a steering handle 11 is provided at the front, and a seat 12 is disposed behind the steering handle 11. Further, a gear ratio setting means 63, a position lever (or position switch) serving as a lift position setting means 72, a tilling depth setting means 65, and the like are disposed on the side portion of the seat 12, and the steering column 11 side portion of the steering handle 11 is disposed. Further, an accelerator lever or a forward / reverse switching lever 62 serving as the engine speed setting means 70 is arranged (see FIG. 3). An accelerator pedal (engine speed setting means 70), a brake pedal, a main clutch pedal, a differential lock pedal, and the like are disposed on the step below the front of the seat 12.

  The work machine connection device 20 mainly includes a top link 21, lower links 22 and 22, and lift rods 23 and 23. The top link 21 is rotatably connected to a top link bracket fixed to the rear portion of the mission case 7. The lower links 22 and 22 are rotatably connected to both sides of the transmission case 7 or the rear axle housing. The lift rods 23, 23 are rotatably connected at one end to the front and rear middle portions of the lower links 22, 22, and the other end is rotatably connected to lift arms 24, 24 protruding rearward from the hydraulic case. . A position sensor serving as a lift position detecting means 73 is disposed at the rotating base of the lift arm 24. In this embodiment, a rotary tiller 30 is connected to the rear ends of the top link 21 and the lower links 22 and 22 as work machines. However, the working machine is not limited to the rotary tiller 30, and a chemical spreader, a mower, a rake or the like can be attached.

  The rotary tilling device 30 includes a tilling claw 31, a tilling cover 32, a rear cover 33, a chain case 34, and the like. The tilling claws 31, 31... Are planted radially on the claw shaft 35 laid horizontally so as to be freely rotatable in the left-right direction, and the rotational trajectories 36 at the tips of the tilling claws 31, 31. A tilling cover 32 is arranged so as to cover the upper side and the side. A front end of the rear cover 33 is rotatably connected to a rear end of the tilling cover 32, and the rotation of the rear cover 33 is a cover serving as a tilling depth detecting means 66. It is detected by the angle sensor. The claw shaft 35 is linked to a PTO shaft 49 protruding rearward from the rear surface of the transmission case 7 via a chain case 34, a universal joint, etc. (see FIG. 2).

  Then, as shown in FIG. 2, the power of the engine 5 is transmitted to the rear wheels 4 and 4 through the main transmission mechanism 41, the forward / reverse switching mechanism 42, the auxiliary transmission mechanism 43, the rear wheel differential mechanism 44, and the like sequentially. At the same time, the power of the engine 5 is transmitted to the front wheels 3 and 3 sequentially through the main transmission mechanism 41, the forward / reverse switching mechanism 42, the auxiliary transmission mechanism 43, the front wheel drive switching mechanism 45, the front wheel differential mechanism 46, and the like. The The continuously variable transmission 41a of the main transmission mechanism 41 is configured by a hydraulic continuously variable transmission, but is not limited thereto, and may be configured by a belt type or toroidal type CVT or the like. As a result, the front wheels 3 and 3 and the rear wheels 4 and 4 are rotationally driven, and the tractor 1 travels. Further, the power of the engine 5 is transmitted to the claw shaft 35 of the rotary tiller 30 through the PTO clutch mechanism 47, the PTO transmission mechanism 48, the PTO shaft 49, and the like sequentially. As a result, the tilling claws 31, 31... Are rotated together with the pawl shaft 35, and the tilling work is performed.

  Next, the structure regarding control of the tractor 1 is demonstrated.

  The control device 100 is provided at an arbitrary position of the tractor 1. The control device 100 includes a central processing unit, a storage device, and the like. As shown in FIG. 3, the control device 100 includes a vehicle speed detection means 61, a forward / reverse switching lever 62, a transmission ratio setting means 63, a transmission ratio detection means 64, a tilling depth setting means 65, and a tilling depth detection. Means 66, PTO switch 67, PTO lever 68, PTO switching dial 69, engine speed setting means 70, engine speed detection means 71, lift position setting means 72, lift position detection means 73, The output detection means 74, the control selection switch 80, the mode operation switch 81, the engine speed change amount setting dial 82, the vehicle speed change amount setting dial 83, the threshold setting dial 84, and the display unit 85 are connected. . In addition, a speed change actuator 91 and a lift actuator 92 are connected to the control device 100.

  The vehicle speed detection means 61 detects the actual traveling speed (vehicle speed) of the tractor 1. In the present embodiment, the vehicle speed detection means 61 is configured to detect the rotational speed of the axle of the rear wheel 4. The vehicle speed detection means 61 is composed of a magnetic pickup coil, a rotary encoder, etc., and the detection value detected by the vehicle speed detection means 61 is transmitted to the control device 100 as the vehicle speed V.

  The forward / reverse switching lever 62 sets the traveling direction of the tractor 1. The forward / reverse switching lever 62 includes a sensor that detects an operation position, and the operation position detected by the sensor is transmitted to the control device 100. The control device 100 transmits a signal to the solenoid valve based on the operation position to drive the hydraulic actuator, and the forward clutch 42a and the reverse clutch 42b (see FIG. 2) of the forward / reverse switching mechanism 42 are turned on or off. ”. More specifically, when the forward / reverse switching lever 62 is operated to the “forward” position, the forward clutch 42a of the forward / reverse switching mechanism 42 is operated to “ON”, and when operated to the “reverse” position, the reverse clutch 42b is set to “ When it is operated to the “neutral” position, the forward clutch 42a and the reverse clutch 42b are operated to “off”.

  The gear ratio setting means 63 sets the gear ratio of the continuously variable transmission 41a in the main transmission mechanism 41. The gear ratio setting means 63 is composed of, for example, a main gear shift lever and a speed adjustment dial. The gear ratio setting means 63 includes a sensor that detects an operation amount, and the operation amount detected by the sensor is transmitted to the control device 100 as a target gear ratio, and the control device 100 determines a target speed ratio based on the target gear ratio. The vehicle speed Vs is determined.

The gear ratio detection means 64 detects the gear ratio of the continuously variable transmission 41a in the main transmission mechanism 41. The gear ratio detection means 64 is, for example, a sensor that detects the swash plate angle of the hydraulic pump or hydraulic motor of the continuously variable transmission, and the signal detected by this sensor is the actual transmission ratio (actual) of the continuously variable transmission 41a. (Transmission ratio) is transmitted to the control device 100.
The sub shift position detecting means 88 detects the shift position of the sub shift lever. However, the shift position of the slider of the subtransmission mechanism 43 may be detected and is not limited. This detection signal is transmitted to the control device 100. In this embodiment, the high position and the low position are detected.

  The tilling depth setting means 65 sets the tilling depth of the tilling claws 31 in the rotary tiller 30 to an arbitrary tilling depth. The working depth setting means 65 is, for example, a working depth setting dial that can be rotated. The tilling depth setting unit 65 includes a sensor that detects an operation amount, and the operation amount detected by the sensor is transmitted to the control device 100 as a target tilling depth.

  The tilling depth detecting means 66 detects the tilling depth of the rotary tiller 30. The plowing depth detecting means 66 is, for example, a cover angle sensor (not shown) that detects the rotation angle of the rear cover 33 with respect to the plowing cover 32 (the opening degree of the rear cover 33). As a result, it is transmitted to the control device 100.

  The PTO switch 67 sets power transmission to the PTO shaft 49 and cutoff. The PTO switch 67 includes a sensor that detects an operation position, and the operation position detected by the sensor is transmitted to the control device 100. The control device 100 transmits a signal to the electromagnetic valve based on the operation position of the PTO switch 67 and a PTO switching dial 69 described later to operate the hydraulic actuator, and the PTO clutch 47a of the PTO clutch mechanism 47 and the PTO clutch 47a are in conflict with each other. The PTO brake 47b that is actuated automatically is turned on or off.

  The PTO lever 68 changes the rotation speed and rotation direction of the PTO shaft 49. The PTO lever 68 is connected to a shifter that selectively changes the meshing of the transmission gear in the PTO transmission mechanism 48. In the present embodiment, the PTO lever 68 can be operated to the “forward”, “neutral”, and “reverse” positions. Based on this operation, the shifter of the PTO transmission mechanism 48 slides, and the PTO shaft 49 The number of rotations and direction of rotation are changed. The PTO lever 68 includes a sensor that detects an operation position, and the operation position detected by the sensor is transmitted to the control device 100.

  The PTO switching dial 69 switches the operation mode of the PTO clutch mechanism 47. The PTO switching dial 69 includes a sensor that detects an operation position, and this sensor is connected to the control device 100. The PTO switching dial 69 can be switched to the “interlocking”, “independent”, or “elevation interlocking” positions.

  The engine speed setting means 70 sets the speed of the engine 5. The engine speed setting means 70 is composed of, for example, an accelerator lever or an accelerator pedal. The engine speed setting means 70 includes a sensor such as a potentiometer that detects the operation amount, and the operation amount detected by the sensor is transmitted to the control device 100 as the target engine speed Ns.

  The engine speed detecting means 71 detects the speed of the engine 5. The engine speed detection means 71 is configured to detect the speed of the flywheel and crankshaft of the engine 5, for example. The engine speed detecting means 71 is composed of a magnetic pickup coil, a rotary encoder, etc., and the signal detected by the engine speed detecting means 71 is transmitted to the control device 100 as the engine speed Nr.

  The raising / lowering position setting means 72 sets the height of the rotary tiller 30 with respect to the vehicle body of the tractor 1. The raising / lowering position setting means 72 includes, for example, a working machine raising / lowering lever for raising and lowering the working machine to an arbitrary height, a working machine raising switch and a working machine lowering switch for raising and lowering to a predetermined position (a raised position and a lowered position). It is said. These work implement lift levers, work implement lift switches, and work implement drop switches are equipped with sensors that detect the operation amount, and the operation amounts detected by these sensors are the target lift position (target rotation of lift arms 24 and 24 described later). Is transmitted to the control device 100 as the angle αs).

  The raising / lowering position detecting means 73 detects the height of the rotary tiller 30 with respect to the vehicle body of the tractor 1, and is disposed at the base of the lift arm 24.

  The output detection means 74 detects the output of the engine 5. For example, the output detection means 74 is calculated from the fuel injection amount of the fuel injection device, and a signal related to the fuel injection pattern of the fuel injection device is transmitted to the control device 100. The control device 100 can calculate the output of the engine 5 based on the signal. Note that the output detection means 74 is not limited to the fuel injection device, and may be any device that can detect the output of the engine 5.

  In the present embodiment, the load detection unit is configured by the control device 100 and the engine speed detection unit 71. The control device 100 calculates the load factor L of the engine 5 based on the engine speed Nr detected by the engine speed detecting means 71. The load detection means detects the load by calculating the load factor L of the engine 5 in this embodiment, but is not limited to this. For example, the load detection means calculates the engine down amount or traction torque or the like. The load may be detected.

The control selection switch 80, the mode operation switch 81, the engine speed change amount setting dial 82, and the vehicle speed change amount setting dial 83 are provided on the operation panel 86 as shown in FIG. The operation panel 86 is provided on the handle column side portion of the steering handle 11.
The threshold setting dial 84 is provided in the driving operation unit 10. However, it may be provided on the operation panel 86.

  The control selection switch 80 constitutes selection means for selecting “ON” or “OFF” for engine speed control and vehicle speed control. Each time the control selection switch 80 is pressed, “ON” or “OFF” of the engine speed control and the vehicle speed control is changed.

  The mode operation switch 81 constitutes an operation means for performing an on / off setting between the heavy load mode and the light load mode. Each time the mode operation switch 81 is pressed, the heavy load mode “OFF” and the light load mode “OFF”, the heavy load mode “ON”, the light load mode “OFF”, the heavy load mode “OFF”, and the light load mode “ON”. ”, And the heavy load mode“ ON ”and the light load mode“ ON ”, one of four states is sequentially changed. On / off of the heavy load mode and the light load mode is indicated by display lamps 86b and 86c, respectively.

  The engine speed change amount setting dial 82 and the vehicle speed change amount setting dial 83 constitute change means that can arbitrarily change the engine speed change amount and the vehicle speed change amount in the heavy load mode and the light load mode. To do.

  The engine speed change amount setting dial 82 is a means for setting an allowable amount of increase or decrease in engine speed from the target engine speed Ns. For example, the allowable amount can be set between 0 rpm and 500 rpm. When the engine speed change amount setting dial 82 is operated and the allowable amount is set to 0 rpm, regardless of the selection of “ON” or “OFF” by the control selection switch 80 and the mode selection by the mode operation switch 81. The engine speed control is not performed.

  The vehicle speed change amount setting dial 83 is a means for setting a vehicle speed change amount (deceleration rate). For example, the deceleration rate can be set between 0% and 50%. When the deceleration rate is set to 0% by operating the vehicle speed change amount setting dial 83, regardless of the selection of “ON” or “OFF” by the control selection switch 80 and the mode selection by the mode operation switch 81, Does not perform vehicle speed control.

  The threshold setting dial 84 changes the set first heavy load value L1, second double load value L2, first light load value L3, and second light load value L4 in the heavy load mode and the light load mode. It constitutes a means. Here, the first heavy load value L1 is a lower limit load value that increases the engine speed in the heavy load mode, and the second double load value L2 is a lower limit load value that decreases the vehicle speed. The first heavy load value L1 and the second double load value L2 may be equal values. The first light load value L3 is an upper limit load value that restores the changed vehicle speed in the light load mode, and the second light load value L4 is the engine speed in the light load mode. It is the upper limit load value to decrease. The first light load value L3 and the second light load value L4 may be equal values. The threshold setting dial 84 may set a threshold value for starting an increase in engine speed and a decrease in vehicle speed in the heavy load mode, or a threshold value for starting a decrease in engine speed and an increase in the vehicle speed in the light load mode. it can.

The display unit 85 is provided in the driving operation unit 10. As shown in FIG. 5, the display unit 85 turns on the display lamp 85 a when the engine speed control and the vehicle speed control are “ON” by operating the control selection switch 80, and turns it OFF when “OFF”.
Further, by operating the control selection switch 80, the display lamp 86a is turned on when the control selection switch 80 is "ON" and is turned off when "OFF". When the control selection switch 80 is “ON”, the display lamp 85a is also turned on at the same time. The position of the display lamp 85a is not limited.
Further, by operating the mode operation switch 81, the display lamps 86b and 86c are turned on or off to display the heavy load mode or the light load mode.

The display unit 85 displays that the engine speed is increasing or decreasing, or that the vehicle speed is decreasing.
The display unit 85 is provided with a lamp that lights up when the engine speed actually increases or decreases by a certain number. In the present embodiment, a lamp that is turned on when the engine speed is increasing by 50 rpm or decreasing by 50 rpm is provided. In addition, the display unit 85 is provided with a liquid crystal unit 85b, and when the vehicle speed is decreasing at a constant speed, the liquid crystal unit 85b displays that the vehicle speed is decreasing. In the present embodiment, when the vehicle speed is reduced by 5% or more, a downward arrow is displayed on the liquid crystal part 85b.

The engine speed changing speed in the heavy load mode and the light load mode is switched depending on the shift position of the subtransmission mechanism 43. The shift position of the subtransmission mechanism 43 is detected by the subtransmission position detection means 88. For example, when the subtransmission mechanism 43 is in a low speed state, the speed at which the engine speed is increased is increased. Further, when the auxiliary transmission mechanism 43 is in a high speed state, the speed at which the engine speed is increased is decreased. Furthermore, the amount of change is increased as the engine speed increases. Specifically, the operating speed of the engine speed changing actuator 93 is changed by a predetermined amount.
The vehicle speed change speed is increased in the vehicle speed increase mode and is decreased in the vehicle speed decrease mode. Specifically, the operating speed of the shift actuator 91 is changed by a predetermined amount.

  The transmission actuator 91 changes the transmission ratio of the continuously variable transmission 41a in the main transmission mechanism 41, that is, the swash plate angle. The speed change actuator 91 includes an electromagnetic proportional valve, a cylinder, a motor, and the like. The speed change actuator 91 is driven based on the signal transmitted from the control device 100 to change the swash plate angle of the continuously variable transmission 41a to change the speed ratio of the main speed change mechanism 41. The control device 100 controls the drive of the speed change actuator 91 so that the actual speed ratio detected by the speed ratio detection means 64 matches the target speed ratio set by the speed ratio setting means 63, thereby continuously variable transmission. The gear ratio of 41a is changed.

  The raising / lowering actuator 92 raises / lowers the rotary tiller 30 with respect to the vehicle body. The lifting / lowering actuator 92 includes a hydraulic cylinder that rotates the lift arms 24 and 24, and an electromagnetic valve that switches the amount and direction of pressure oil supplied to the hydraulic cylinder. The lifting / lowering actuator 92 is driven based on a signal transmitted from the control device 100 to change the height of the rotary tiller 30.

  The engine speed changing actuator 93 changes the engine speed. The engine speed changing actuator 93 is a rack actuator in the case of an electronic governor, and an injector in the case of a common rail type. The engine speed changing actuator 93 is driven based on a signal transmitted from the control device 100 to change the fuel injection amount to change the engine speed. The control device 100 drives and controls the engine speed changing actuator 93 so that the engine speed Nr matches the target engine speed Ns.

  Below, the control aspect of the tractor 1 is demonstrated in detail.

The calculation of the output of the engine 5 and the load factor L by the control device 100 will be described.
The control device 100 constantly calculates the output (PS) of the engine 5. Specifically, the control device 100 does not show the relationship between the fuel injection pattern of the fuel injection device (for example, the fuel injection amount, the number of fuel injections, the fuel injection timing, etc.) and the output of the engine 5. A map is stored in advance. The control device 100 calculates the output of the engine 5 based on the fuel injection pattern of the fuel injection device and the map.

  The control device 100 constantly calculates the load factor L of the engine 5. Here, the load factor L according to the present embodiment refers to the ratio (%) of the actual injection amount to the maximum fuel injection amount when the engine 5 is driven at a certain rotational speed. Specifically, the control device 100 stores in advance a map indicating the relationship between the output and the load factor L for each engine speed Nr. The control device 100 calculates the load factor L of the engine 5 based on the engine speed Nr detected by the engine speed detecting means 71, the calculated output of the engine 5, and the map.

  Hereinafter, aspects of engine speed and vehicle speed control by the control device 100 will be described with reference to FIGS.

First, in FIG. 6, it is determined whether or not the control selection switch 80 is “ON” (step S10). When the control selection switch 80 is “OFF”, the process returns to step S10 again.
If the control selection switch 80 is “ON”, it is next determined whether or not the heavy load mode is selected (step S20). If the heavy load mode is selected, it is further determined whether or not the light load mode is selected (step S30). When the light load mode is selected, the process proceeds to step S100. If the light load mode is not selected, the process proceeds to step S200. If the heavy load mode is not selected in step S20, it is further determined whether or not the light load mode is selected (step S40). When the light load mode is selected, the process proceeds to step S300. If the light load mode is not selected, the process proceeds to step S400.

<Heavy load mode / Engine speed increase step>
In step S100 shown in FIG. 7, it is determined whether or not the calculated load factor L is larger than the set heavy load value L1. When the load factor L is larger than the heavy load value L1, it is determined whether or not the engine speed Nr is smaller than the engine speed upper limit value Nmax (step S105), and the load factor L is less than or equal to the heavy load value L1. In that case, the process proceeds to step S120. If the engine speed Nr is smaller than the engine speed change upper limit value Nmax in step S105, the engine speed change actuator 93 is driven to increase the engine speed Nr (step S110). Then, the process returns to step S100. If the engine speed Nr is greater than or equal to the engine speed upper limit value Nmax in step S105, the engine speed upper limit value Nmax is maintained and the process proceeds to step S120.

<Heavy load mode / vehicle speed reduction step>
In step S120, it is determined whether or not the load factor L is larger than the heavy load value L2. When the load factor L is larger than the heavy load value L2, it is determined whether or not the target vehicle speed Vs is faster than the vehicle speed lower limit value Vmin (step S125). When the load factor L is less than or equal to the heavy load value L2, the process proceeds to step S140. If the vehicle speed V is higher than the vehicle speed lower limit value Vmin in step S125, the vehicle speed V is decreased by driving the speed change actuator 91 (step S130). Then, the process returns to step S120. In step S125, when the target vehicle speed Vs is equal to or lower than the vehicle speed lower limit value Vmin, the target vehicle speed Vs is maintained at the vehicle speed lower limit value Vmin, and the process proceeds to step S140.

<Light load mode / vehicle speed return step>
In step S140 shown in FIG. 7, it is determined whether or not the load factor L is smaller than the light load value L3. If the load factor L is smaller than the light load value L3, it is determined whether or not the vehicle speed V and the target vehicle speed Vs are the same (step S145). If the load factor L is greater than or equal to the light load value L3. Since it is in the proper load range, the engine speed and the vehicle speed are maintained. In step S145, when the vehicle speed V is not the target vehicle speed Vs, the speed change actuator 91 is driven to set the vehicle speed V to the target vehicle speed Vs (step S150). Then, the process proceeds to step S140. In step S145, when the vehicle speed V is the target vehicle speed Vs, the process proceeds to step S160.

<Light load mode, engine speed reduction step>
In step S160, it is determined whether or not the load factor L is smaller than the light load value L4. When the load factor L is smaller than the light load value L4, it is determined whether or not the engine speed Nr is larger than the engine speed lower limit value Nmin (step S165). When the load factor L is greater than or equal to the light load value L4, the engine speed and the vehicle speed are maintained, and the process returns to the beginning. In step S165, when the engine speed Nr is larger than the engine speed lower limit Nmin, the engine speed Nr is set by the engine speed change amount setting dial 82 by driving the engine speed change actuator 93. The change amount is decreased (step S170). Then, the process returns to S160. In step S165, when the engine speed Nr is equal to or lower than the engine speed lower limit value Nmin, the engine speed lower limit value Nmin is maintained, and the process returns to the beginning.

<Heavy load mode / Engine speed increase step>
In step S200 shown in FIG. 8, it is determined whether or not the load factor L is larger than the heavy load value L1. When the load factor L is larger than the heavy load value L1, it is determined whether or not the engine speed Nr is smaller than the engine speed upper limit value Nmax (step S205). When the load factor L is less than or equal to the heavy load value L1, the process proceeds to step S220. In step S205, if the engine speed Nr is smaller than the engine speed upper limit Nmax, the engine speed Nr is increased by driving the engine speed changing actuator 93 (step S210). Then, the process returns to step S200. In step S205, when the engine speed Nr is equal to or higher than the engine speed upper limit Nmax, the process proceeds to step S220.

<Heavy load mode / vehicle speed reduction step>
In step S220, it is determined whether or not the load factor L is larger than the heavy load value L2. When the load factor L is larger than the heavy load value L2, it is determined whether or not the target vehicle speed Vs is faster than the vehicle speed lower limit value Vmin (step S225). When the load factor L is less than or equal to the heavy load value L2, the process returns to the beginning. If the target vehicle speed Vs is larger than the vehicle speed lower limit value Vmin in step S225, the vehicle speed V is decreased by driving the speed change actuator 91 (step S230). Then, the process returns to step S220. If the target vehicle speed Vs is equal to or lower than the vehicle speed lower limit value Vmin in step S225, the process returns to the beginning.

<Light load mode, engine speed reduction step>
In step S300 shown in FIG. 9, it is determined whether or not the load factor L is smaller than the light load value L4. When the load factor L is smaller than the light load value L4, it is determined whether or not the engine speed Nr is larger than the engine speed lower limit value Nmin (step S305). If the load factor L is greater than or equal to the heavy load value L4, the process returns to the beginning. In step S305, when the engine speed Nr is larger than the engine speed lower limit value Nmin, the engine speed Nr is set by the engine speed change amount setting dial 82 by driving the engine speed change actuator 93. Decrease by the change amount (step S310), and return to step S300. In step S305, when the engine speed Nr is equal to or lower than the engine speed lower limit Nmin, the process returns to the beginning.

<No mode selection, vehicle speed reduction step>
In step S400 shown in FIG. 10, it is determined whether or not the load factor L is larger than the heavy load value L2. When the load factor L is larger than the heavy load value L2, it is determined whether or not the target vehicle speed Vs is faster than the vehicle speed lower limit value Vmin (step S405). When the load factor L is less than or equal to the heavy load value L2, the process returns to the beginning. If the target vehicle speed Vs is greater than the vehicle speed lower limit value Vmin in step S405, the vehicle speed V is decreased by driving the speed change actuator 91 (step S410). Then, the process returns to step S400. If the target vehicle speed Vs is equal to or lower than the vehicle speed lower limit value Vmin in step S405, the process returns to the beginning.

  Below, an example of the time change of the load factor L, the engine speed Nr, and the vehicle speed V when the engine speed and the vehicle speed control are performed will be described with reference to FIG. In this example, the control selection switch 80 is in the “ON” state, and the heavy load mode and the light load mode are selected. Hereinafter, a case where the heavy load value L1 and the heavy load value L2 are equal and the light load value L3 and the light load value L4 are equal will be described.

When the load factor L increases and becomes larger than the heavy load value L1 (T1), when the state larger than the heavy load value L1 continues for a minute time d1, the engine speed changing actuator 93 is driven. As a result, the engine speed Nr is increased. The length of the minute time d1 can be changed and can be set to zero. The speed at which the engine speed Nr is increased is determined based on the state of the auxiliary transmission mechanism 43.
Next, even when the engine speed Nr has remained at or above the engine speed upper limit Nmax for a minute time d2 from the time point (T2) when the engine speed Nr has become equal to or higher than the engine speed upper limit value Nmax, Since the load factor L is larger than the heavy load value L2 (L1), the vehicle speed V is decreased. The length of the minute time d2 can be changed and can be set to zero. The speed at which the vehicle speed V is decreased is determined based on the state of the auxiliary transmission mechanism 43.
The decrease in the vehicle speed V continues until the time point (T3) when the load factor L becomes equal to or less than the heavy load value L2 (L1). After T3, the engine speed Nr remains at the change upper limit value and the vehicle speed V decreases at the time point T3. Maintains speed.
Furthermore, when the state where the load factor L becomes smaller than the light load value L3 continues for a minute time d3 from the time (T4) when the load factor L becomes smaller than the light load value L3, the vehicle speed V becomes Since it is different from the target vehicle speed Vs, the vehicle speed V is increased to return to the target vehicle speed Vs. The length of the minute time d3 can be changed and can be set to zero. Even when the vehicle speed V becomes equal to the target vehicle speed Vs (T5), if the state where the load factor L is smaller than the light load value L4 (L3) continues for a minute time d4, the engine speed is changed. By driving the actuator 93, the engine speed Nr is decreased. The length of the minute time d4 can be changed and can be set to zero. The speed at which the engine speed Nr is increased is determined based on the state of the auxiliary transmission mechanism 43.
The decrease in the engine speed Nr continues until a time point (T6) when the load factor L becomes equal to or higher than the light load value L4 (L3). After T6, the engine speed Nr remains at the reduced engine speed at the time point T6 and the vehicle speed. V is maintained at the target vehicle speed Vs.

  Further, when the engine speed change amount setting dial 82 is operated during the engine speed and vehicle speed control and the engine speed upper limit value Nmax or the engine speed lower limit value Nmin is changed, the changed engine speed upper limit value is changed. The engine speed Nr is changed so as to be equal to or less than the value Nmax or equal to or greater than the changed engine speed lower limit Nmin.

  For example, as shown in FIG. 12, when the engine speed Nr is increased from T7 and increased to the engine speed N1 (T8), the engine speed is maintained at N1. When the engine speed upper limit Nmax is decreased from Nmax1 to Nmax2 by operating the engine speed change amount setting dial 82, the engine speed Nr is set to Nmax2 by driving the engine speed change actuator 93 from T9. Decrease gradually. When the engine speed Nr becomes Nmax2 at T10, the engine speed and the vehicle speed are controlled again.

Further, when the engine speed setting means 70 is operated during the engine speed and vehicle speed control and the target engine speed Ns is changed, an increase / decrease of the target engine speed Ns to the engine speed Nr at that time. Is increased or decreased.
For example, as shown in FIG. 13, when the engine speed Nr is increased from T11 and the engine speed Nr is increased from the target engine speed Ns1 to N2 (T12), the engine speed Nr is maintained at N2. If the target engine speed Ns is increased from Ns1 to Ns2 by operating the engine speed setting means 70 at T13, the engine speed is changed from T13 by driving the engine speed change actuator 93. The number Nr is gradually increased by the difference d between Ns2 and Ns1. When the engine speed Nr becomes N2 + d at T14, the engine speed Nr is maintained as it is.

  Further, when the engine speed setting means 70 is being operated, the engine speed and vehicle speed control are temporarily stopped. That is, when the target engine speed Ns fluctuates, the load factor L fluctuates greatly, so that the engine speed and vehicle speed control are temporarily suspended.

  Further, when the control selection switch is changed from “ON” to “OFF” by operating the control selection switch 80 during the engine speed and vehicle speed control, the engine speed change actuator 93 and the speed change actuator 91 are changed. By driving, the engine speed Nr and the vehicle speed V are gradually returned to the target engine speed Ns and the target vehicle speed Vs.

As described above, the tractor 1 includes the engine speed detecting means 71, the engine speed setting means 70, the engine speed changing actuator 93, the vehicle speed detecting means 61, the continuously variable transmission 41a, and the continuously variable transmission. In a tractor including a speed change actuator 91 for shifting 41a, a control device 100 as load detection means, an engine speed detection means 71, an output detection means 74, and a control device 100 for controlling the engine speed and vehicle speed. engine load factor L is, when it becomes larger than the heavy load value L1 is set to increase the engine rotational speed Nr while maintaining the vehicle speed V constant, while the engine rotational speed Nr increases until the engine rotational speed upper limit value Nmax When the engine load factor L becomes larger than the set heavy load value L2, the engine speed factor V is decreased so as to decrease the vehicle speed V. When the engine load factor L becomes smaller than the set light load value L4, the engine speed Nr is maintained while keeping the vehicle speed V constant. A light load mode for controlling the engine speed changing actuator 93 and the speed change actuator 91 so as to decrease the speed is provided.
With this configuration, when the heavy load mode is selected at the time of heavy load, the engine speed Nr can be increased, the vehicle speed V can be decreased, engine stall can be prevented, and work efficiency can be improved. . Further, at the time of light load, when the light load mode is selected, the engine speed Nr is decreased by the engine speed changing actuator 93, and the vehicle can travel with low fuel consumption.

Also provided with an engine speed change amount setting dial 82 and a vehicle speed change amount setting dial 83 capable of arbitrarily changing the change amount of the engine speed Nr and the change amount of the vehicle speed V in the heavy load mode and the light load mode. It is.
By configuring in this way, the amount of change in the engine speed Nr and the amount of change in the vehicle speed V in each mode can be changed according to the user's preference, work mode, and state of the field, respectively, and work efficiency can be improved. Can be improved.

Further, a mode operation switch 81 for performing on / off setting of control of the engine speed changing actuator 93 by performing on / off setting for the heavy load mode or the light load mode is provided.
With this configuration, the heavy load mode or the light load mode can be arbitrarily selected by turning on / off the mode operation switch 81 according to the user's preference.

In the heavy load mode and the light load mode, the set heavy load value L1 and heavy load value L2, and the set light load value L3 and light load value L4 can be changed by the threshold setting dial 84.
By configuring in this way, the threshold value in each mode can be changed according to the user's preference, work mode, and state of the field, so that the work finish can be improved and engine stall can be prevented.

Further, a sub-transmission mechanism 43 is provided as setting means for setting the engine speed changing speed and the vehicle speed changing speed in the heavy load mode and the light load mode.
By configuring in this way, the threshold value in each mode can be changed according to the user's preference, work mode, and state of the field, so that the work finish can be improved and engine stall can be prevented.

Moreover, the display part 85 which displays heavy load mode and light load mode is provided.
With this configuration, the work vehicle setting state can be easily confirmed.

DESCRIPTION OF SYMBOLS 1 Tractor 5 Engine 61 Vehicle speed detection means 70 Engine rotation speed setting means 71 Engine rotation speed detection means 80 Control selection switch 81 Mode operation switch 82 Engine rotation speed change amount setting dial 83 Vehicle speed change amount setting dial 84 Threshold setting dial 85 Display unit 91 Variable speed actuator 93 Engine speed change actuator 100 Control device

Claims (6)

Engine speed detection means, engine speed setting means, engine speed change actuator, vehicle speed detection means, continuously variable transmission, variable speed actuator for shifting the continuously variable transmission, load detection means, engine In a work vehicle comprising a control device that controls the rotational speed and the vehicle speed,
Engine load, when it becomes larger than the heavy load value set, to increase the engine speed while maintaining a vehicle speed constant, increasing engine speed until the engine rotational speed upper limit value, the engine load, set A heavy load mode for controlling the engine speed change actuator and the speed change actuator so as to reduce the vehicle speed when the load value is greater than the heavy load value;
Work with a light load mode for controlling the engine speed changing actuator and the speed change actuator so that the engine speed is decreased while maintaining the vehicle speed constant when the engine load becomes smaller than the set light load value. vehicle.   2. The work vehicle according to claim 1, further comprising a changing unit capable of arbitrarily changing a change amount of the engine speed and a change amount of the vehicle speed in the heavy load mode and the light load mode.   The work vehicle according to claim 1, further comprising operation means for performing on / off setting of control of the engine speed changing actuator by performing on / off setting for the heavy load mode or the light load mode.   The work vehicle according to claim 1, wherein the set heavy load value and the set light load value in the heavy load mode and the light load mode can be changed by a threshold setting means.   The work vehicle according to claim 1, further comprising setting means for setting an engine speed change speed and a vehicle speed change speed in the heavy load mode and the light load mode.   The work vehicle according to claim 1, further comprising display means for displaying the heavy load mode and the light load mode and displaying that the engine speed is increasing or decreasing or the vehicle speed is decreasing.