Work vehicle

Abstract

To provide a work vehicle which can travel with low fuel consumption in a light load, thereby increasing working efficiency.SOLUTION: A work vehicle includes a control device for controlling an engine speed. When a predetermined condition is satisfied, the control device executes a control of reducing the engine speed within a range of an allowable value. The work vehicle further includes a change value display means which displays the engine speed.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to work vehicle technology. [Background technology]

[0002] Conventionally, work vehicles such as tractors are known that transmit engine rotational power to a traveling device via a continuously variable transmission. These work vehicles are equipped with an accelerator lever or accelerator pedal, which is an engine speed setting means for setting the normal engine speed. Also known are work vehicles that change vehicle speed during work in response to engine load, which is expressed by the engine load factor, engine down amount, traction torque, or the like. When the engine load is heavy (under heavy load), the vehicle speed is slowed to prevent engine stalling. When the engine load is light (under light load), the vehicle speed is increased to improve driving performance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-315472 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if the vehicle speed is increased under light load, the driving performance improves, but the engine speed also increases more than necessary, so fuel economy cannot be improved.

[0005] SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a work vehicle that can run with low fuel consumption when under a light load, thereby improving work efficiency. [Means for solving the problem]

[0006] The problem to be solved by the present invention is as described above, and the means for solving this problem will now be described.

[0007] A work vehicle according to one aspect of the present invention includes a control device for controlling engine speed. The control device executes control to reduce the engine speed within an allowable range when a predetermined condition is satisfied. The work vehicle further includes a change amount display means for displaying the amount of reduction when the engine speed is reduced. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is an overall side view of a tractor according to an embodiment of the present invention; [Figure 2] FIG. 2 is a diagram showing the power transmission structure of a tractor. [Figure 3] FIG. 2 is a block diagram showing a configuration related to control of the tractor. [Figure 4] FIG. [Figure 5] FIG. [Figure 6] FIG. 4 is a first flowchart showing a control mode of engine speed and vehicle speed control. [Figure 7] FIG. 6 is a second flowchart showing the control mode of engine speed and vehicle speed control. [Figure 8] FIG. 10 is a third flowchart showing the control mode of engine speed and vehicle speed control. [Figure 9] FIG. 4 is a fourth flowchart showing the control manner of engine speed and vehicle speed control. [Figure 10] FIG. 5 is a fifth flowchart showing the control manner of engine speed and vehicle speed control. [Figure 11] FIG. 4 is a graph showing the relationship between load, engine speed, and vehicle speed and time. [Figure 12] FIG. 10 is a graph showing the relationship between engine speed and time when the upper limit of engine speed is changed. [Figure 13] FIG. 6 is a graph showing the relationship between engine speed and time when the target engine speed is changed. DETAILED DESCRIPTION OF THE INVENTION

[0009] Next, the overall configuration of the tractor 1 according to one embodiment of the present invention will be described.

[0010] As shown in Figure 1, in tractor 1, a body frame 2 is disposed with its longitudinal direction in the fore-and-aft direction, and is supported at its front by a pair of left and right front wheels 3,3 via a front axle, and at its rear by a pair of left and right rear wheels 4,4 via a rear axle. An engine 5 is mounted at the front of body frame 2 and is covered by a hood 6. A transmission case 7 that houses part of the tractor 1's power transmission mechanism is mounted at the rear of body frame 2.

[0011] A cabin 8 is disposed behind the bonnet 6, and inside the cabin 8 is provided a driving operation unit 10 for an operator to sit in and operate the tractor 1. A steering wheel 11 is provided at the front of the driving operation unit 10, and a seat 12 is disposed behind the steering wheel 11. Further, a gear ratio setting means 63, a position lever (or position switch) serving as a lift position setting means 72, a tillage depth setting means 65, etc. are disposed on the side of the seat 12, and an accelerator lever and forward / reverse switch lever 62 serving as an engine speed setting means 70 are disposed on the side of the steering wheel 11 (see FIG. 3). Further, an accelerator pedal (engine speed setting means 70), a brake pedal, a main clutch pedal, a differential lock pedal, etc. are disposed on a step below and in front of the seat 12.

[0012] The work implement coupling device 20 primarily comprises a top link 21, lower links 22, and lift rods 23. The top link 21 is rotatably coupled to a top link bracket fixed to the rear of the transmission case 7. The lower links 22 are rotatably coupled to both sides of the transmission case 7 or the rear axle housing. One end of each of the lift rods 23 is rotatably coupled to a midpoint between the front and rear of the lower links 22, and the other end is rotatably coupled to lift arms 24, which protrude rearward from the hydraulic case. A position sensor serving as lift position detection means 73 is disposed at the base of the rotation of the lift arm 24. In this embodiment, a rotary tiller 30 is coupled to the rear ends of the top link 21 and the lower links 22. However, the work implement is not limited to the rotary tiller 30, and a chemical sprayer, mower, rake, etc. may also be attached.

[0013] The rotary tiller 30 includes tiller tines 31, a tiller cover 32, a rear cover 33, a chain case 34, etc. The tiller tines 31 are radially arranged at appropriate intervals on a tine shaft 35 that is horizontally suspended so as to be rotatable in the left-right direction, and a tiller cover 32 is disposed so as to cover the upper and lateral sides of a rotation locus 36 of the tips of the tines 31. The front end of a rear cover 33 is rotatably connected to the rear end of the tiller cover 32, and the rotation of the rear cover 33 is detected by a cover angle sensor that serves as tilling depth detection means 66. The tine shaft 35 is operatively connected to a PTO shaft 49 that protrudes rearward from the rear surface of the transmission case 7 via the chain case 34, a universal joint, etc. (see FIG. 2).

[0014] As shown in FIG. 2 , the power of the engine 5 is transmitted to the rear wheels 4·4 via a main transmission mechanism 41, a forward / reverse switching mechanism 42, an auxiliary transmission mechanism 43, a rear wheel differential mechanism 44, etc., and the power of the engine 5 is transmitted to the front wheels 3·3 via a main transmission mechanism 41, a forward / reverse switching mechanism 42, an auxiliary transmission mechanism 43, a front wheel drive switching mechanism 45, a front wheel differential mechanism 46, etc. The continuously variable transmission 41a of the main transmission mechanism 41 is configured as a hydraulic continuously variable transmission, but is not limited to this and can also be configured as a belt-type or toroidal CVT, etc. As a result, the front wheels 3·3 and the rear wheels 4·4 are rotated, and the tractor 1 travels. The power of the engine 5 is also transmitted to the tine shaft 35 of the rotary tiller 30 via a PTO clutch mechanism 47, a PTO transmission mechanism 48, a PTO shaft 49, etc., As a result, the tillage tines 31 are rotationally driven together with the tine shaft 35, and tillage work is carried out.

[0015] Next, the configuration relating to the control of the tractor 1 will be described.

[0016] The control device 100 is provided at any position on the tractor 1. The control device 100 is composed of a central processing unit, a storage device, etc. As shown in FIG. 3 , the control device 100 is connected to a vehicle speed detection means 61, a forward / reverse selector lever 62, a gear ratio setting means 63, a gear ratio detection means 64, a tillage depth setting means 65, a tillage depth detection means 66, a PTO switch 67, a PTO lever 68, a PTO selector dial 69, an engine speed setting means 70, an engine speed detection means 71, a lift position setting means 72, a lift position detection means 73, an output detection means 74, a control selection switch 80, a mode operation switch 81, an engine speed change amount setting dial 82, a vehicle speed change amount setting dial 83, a threshold setting dial 84, and a display unit 85. A speed change actuator 91 and a lift actuator 92 are also connected to the control device 100.

[0017] The vehicle speed detection means 61 detects the actual traveling speed (vehicle speed) of the tractor 1. In this embodiment, the vehicle speed detection means 61 is configured to detect the rotation speed of the axle of the rear wheel 4. The vehicle speed detection means 61 is configured with 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.

[0018] The forward / reverse switch lever 62 sets the direction of travel of the tractor 1. The forward / reverse switch lever 62 is equipped with a sensor that detects its operating position, and the operating position detected by this sensor is sent to the control device 100. The control device 100 sends a signal to a solenoid valve based on the operating position to drive a hydraulic actuator, and switches the forward clutch 42a and reverse clutch 42b (see FIG. 2) of the forward / reverse switch mechanism 42 on or off. In detail, when the forward / reverse switch lever 62 is operated to the "forward" position, the forward clutch 42a of the forward / reverse switch mechanism 42 is switched on; when the forward / reverse switch lever 62 is operated to the "reverse" position, the reverse clutch 42b is switched on; and when the forward / reverse switch lever 62 is operated to the "neutral" position, the forward clutch 42a and reverse clutch 42b are switched off.

[0019] 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 configured with, for example, a main speed change lever or a speed adjustment dial. The gear ratio setting means 63 is equipped with a sensor that detects an operation amount, and the operation amount detected by this sensor is transmitted to the control device 100 as a target gear ratio, and the control device 100 determines the target vehicle speed Vs based on the target gear ratio.

[0020] 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 a signal detected by this sensor is sent to the control device 100 as the actual gear ratio (actual gear ratio) of the continuously variable transmission 41a. The sub-transmission position detection means 88 detects the shift position of the sub-transmission lever. However, the detection is not limited to this and may also detect the shift position of the slider of the sub-transmission mechanism 43. This detection signal is sent to the control device 100. In this embodiment, a high position and a low position are detected.

[0021] The tillage depth setting means 65 sets the tillage depth of the tillage tines 31 of the rotary tillage device 30 to an arbitrary tillage depth. The tillage depth setting means 65 is, for example, a tillage depth setting dial that can be turned. The tillage depth setting means 65 is equipped with a sensor that detects the amount of operation, and the amount of operation detected by this sensor is sent to the control device 100 as the target tillage depth.

[0022] The tillage depth detection means 66 detects the tillage depth of the rotary tillage device 30. The tillage depth detection means 66 is, for example, a cover angle sensor (not shown) that detects the rotation angle of the rear cover 33 relative to the tillage cover 32 (the opening degree of the rear cover 33), and the detection value of this cover angle sensor is transmitted to the control device 100 as the tillage depth.

[0023] The PTO switch 67 sets whether to transmit or cut off power to the PTO shaft 49. The PTO switch 67 is equipped with a sensor that detects its operating position, and the operating position detected by this sensor is sent to the control device 100. The control device 100 sends a signal to a solenoid valve based on the operating positions of the PTO switch 67 and a PTO selector dial 69 (described later) to operate a hydraulic actuator, and turns the PTO clutch 47a of the PTO clutch mechanism 47 and the PTO brake 47b, which operates inversely with the PTO clutch 47a, "on" or "off."

[0024] The PTO lever 68 changes the rotation speed and direction of the PTO shaft 49. The PTO lever 68 is connected to a shifter that selectively changes the engagement of the transmission gears in the PTO transmission mechanism 48. In this embodiment, the PTO lever 68 can be operated to "forward," "neutral," and "reverse" positions, and based on this operation, the shifter of the PTO transmission mechanism 48 slides to change the rotation speed and direction of the PTO shaft 49. The PTO lever 68 is equipped with a sensor that detects its operating position, and the operating position detected by this sensor is sent to the control device 100.

[0025] The PTO switch dial 69 switches the operation mode of the PTO clutch mechanism 47. The PTO switch dial 69 is equipped with a sensor that detects the operation position, and this sensor is connected to the control device 100. The PTO switch dial 69 can be switched to the "interlocked," "independent," or "lift-and-lower interlocked" position.

[0026] The engine speed setting means 70 sets the speed of the engine 5. The engine speed setting means 70 is configured by, for example, an accelerator lever or an accelerator pedal. The engine speed setting means 70 is provided with a sensor such as a potentiometer that detects an operation amount, and the operation amount detected by this sensor is transmitted to the control device 100 as a target engine speed Ns.

[0027] The engine speed detection means 71 detects the rotation speed of the engine 5. The engine speed detection means 71 is configured to detect, for example, the rotation speed of a flywheel or a crankshaft of the engine 5. The engine speed detection means 71 is configured with a magnetic pickup coil, a rotary encoder, or the like, and a signal detected by the engine speed detection means 71 is transmitted to the control device 100 as the engine speed Nr.

[0028] The lifting position setting means 72 sets the height of the rotary tiller 30 relative to the vehicle body of the tractor 1. The lifting position setting means 72 may be, for example, a work implement lifting lever that raises or lowers the work implement to a desired height, or a work implement raising switch and a work implement lowering switch that raise or lower the work implement to a predetermined position (upper position or lowered position). These work implement lifting levers, work implement raising switch, and work implement lowering switch are equipped with sensors that detect the amount of operation, and the amount of operation detected by these sensors is sent to the control device 100 as a target lifting position (target rotation angle αs of the lift arms 24·24, described below).

[0029] The lift position detection means 73 detects the height of the rotary tiller 30 relative to the vehicle body of the tractor 1, and is disposed at the base of the lift arm 24.

[0030] The output detection means 74 detects the output of the engine 5. For example, the output detection means 74 calculates the output 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 anything that can detect the output of the engine 5.

[0031] In this embodiment, the load detection means is made up of the control device 100 and the engine speed detection means 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 detection means 71. In this embodiment, the load detection means detects the load by calculating the load factor L of the engine 5, but is not limited to this, and the load may be detected by calculating, for example, the engine down amount, traction torque, etc.

[0032] As shown in Fig. 4, the control selection switch 80, the mode operation switch 81, the engine rotation speed change amount setting dial 82, and the vehicle speed change amount setting dial 83 are provided on an operation panel 86. The operation panel 86 is provided on the side of the steering column of the steering wheel 11. The threshold setting dial 84 is provided inside the driving operation unit 10. However, it may be provided on the operation panel 86.

[0033] The control selector switch 80 constitutes a selection means for selecting "ON" or "OFF" for the engine speed control and the vehicle speed control. Each time the control selector switch 80 is pressed, the engine speed control and the vehicle speed control are switched between "ON" and "OFF."

[0034] The mode operation switch 81 constitutes an operating means for switching on and off the heavy load mode and the light load mode. Each time the mode operation switch 81 is pressed, the mode is changed in sequence to one of four modes: heavy load mode "off" and light load mode "off", heavy load mode "on" and light load mode "off", heavy load mode "off" and light load mode "on", and heavy load mode "on" and light load mode "on". The on / off status of the heavy load mode and the light load mode is indicated by indicator lamps 86b and 86c, respectively.

[0035] The engine speed change amount setting dial 82 and the vehicle speed change amount setting dial 83 constitute a change means that can arbitrarily change the amount of change in the engine speed and the amount of change in the vehicle speed in the heavy load mode and the light load mode.

[0036] The engine speed change amount setting dial 82 is a means for setting the allowable increase or decrease in engine speed from the target engine speed Ns. The allowable amount can be set, for example, between 0 rpm and 500 rpm. When the allowable amount is set to 0 rpm by operating the engine speed change amount setting dial 82, engine speed control is not performed regardless of whether "on" or "off" is selected with the control selector switch 80 or the mode selected with the mode operation switch 81.

[0037] The vehicle speed change amount setting dial 83 is a means for setting the amount of change in vehicle speed (deceleration rate). For example, the deceleration rate can be set between 0% and 50%. When the vehicle speed change amount setting dial 83 is operated to set the deceleration rate to 0%, vehicle speed control is not performed regardless of whether "on" or "off" is selected with the control selection switch 80 or the mode selected with the mode operation switch 81.

[0038] The threshold setting dial 84 constitutes a threshold setting means for changing the first heavy load value L1, the second load value L2, the first light load value L3, and the second light load value L4 set in the heavy load mode and the light load mode. Here, the first heavy load value L1 is the lower limit load value at which the engine speed is increased in the heavy load mode, and the second load value L2 is the lower limit load value at which the vehicle speed is decreased. The first heavy load value L1 and the second load value L2 may be equal values. Furthermore, the first light load value L3 is the upper limit load value at which the changed vehicle speed is restored in the light load mode, and the second light load value L4 is the upper limit load value at which the engine speed is decreased in the light load mode. The first light load value L3 and the second light load value L4 may be equal values. The threshold setting dial 84 can set a threshold at which an increase in the engine speed and a decrease in the vehicle speed start in the heavy load mode, or a threshold at which a decrease in the engine speed and an increase in the vehicle speed start in the light load mode.

[0039] The display unit 85 is provided in the driving operation unit 10. As shown in FIG. 5, the display unit 85 turns on an indicator lamp 85a when the engine speed control and vehicle speed control are "on" by operation of the control selector switch 80, and turns off the indicator lamp 85a when the control control and vehicle speed control are "off." Furthermore, by operation of the control selector switch 80, an indicator lamp 86a turns on when the control selector switch 80 is "on" and turns off when the control selector switch 80 is "off." Furthermore, when the control selector switch 80 is "on," the indicator lamp 85a also turns on at the same time. Note that the position of the indicator lamp 85a is not limited. Furthermore, by operation of the mode operation switch 81, indicator lamps 86b and 86c turn on or off to indicate whether the heavy load mode or the light load mode is selected.

[0040] The display unit 85 also displays whether the engine speed is increasing or decreasing, or whether the vehicle speed is decreasing. The display unit 85 is provided with a lamp that lights up when the engine speed is actually increasing or decreasing by a certain number. In this embodiment, a lamp that lights up when the engine speed is increasing or decreasing by 50 rpm is provided. The display unit 85 is also provided with a liquid crystal display 85b, and when the vehicle speed is decreasing by a certain rate, the liquid crystal display 85b displays a message that the vehicle speed is decreasing. In this embodiment, when the vehicle speed is decreasing by 5% or more, a downward arrow is displayed on the liquid crystal display 85b.

[0041] The engine rotation speed change speed between the heavy load mode and the light load mode is switched depending on the shift position of the sub-transmission mechanism 43. The shift position of the sub-transmission mechanism 43 is detected by the sub-transmission position detection means 88. For example, when the sub-transmission mechanism 43 is in a low-speed state, the rate at which the engine rotation speed is increased is increased. On the other hand, when the sub-transmission mechanism 43 is in a high-speed state, the rate at which the engine rotation speed is increased is decreased. Furthermore, the higher the engine rotation speed, the greater the change amount. Specifically, the operating speed of the engine rotation speed change actuator 93 is changed by a predetermined amount. Also, the vehicle speed change speed is increased in the vehicle speed increase mode and decreased in the vehicle speed decrease mode. Specifically, the operating speed of the shift actuator 91 is changed by a predetermined amount.

[0042] The speed change actuator 91 changes the speed ratio, i.e., the swash plate angle, of the continuously variable transmission 41a in the main transmission mechanism 41. The speed change actuator 91 is composed of an electromagnetic proportional valve, a cylinder, a motor, etc. The speed change actuator 91 is driven based on a signal sent from the control device 100 to change the swash plate angle of the continuously variable transmission 41a and change the speed ratio of the main transmission mechanism 41. The control device 100 drives and controls the speed change actuator 91 to change the speed ratio of the continuously variable transmission 41a 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.

[0043] The lifting actuator 92 raises and lowers the rotary tiller 30 relative to the vehicle body. The lifting actuator 92 is composed of a hydraulic cylinder that rotates the lift arms 24, and a solenoid valve that switches the amount and direction of pressurized oil sent to the hydraulic cylinder. The lifting actuator 92 is driven based on a signal sent from the control device 100 to change the height of the rotary tiller 30.

[0044] The engine speed changing actuator 93 changes the engine speed. In the case of an electronic governor, the engine speed changing actuator 93 is a rack actuator, and in the case of a common rail type, it is composed of an injector. The engine speed changing actuator 93 is driven based on a signal sent from the control device 100 to change the fuel injection amount and 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.

[0045] The control mode of the tractor 1 will be described in detail below.

[0046] The calculation of the output and load factor L of the engine 5 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 stores in advance a map (not shown) that indicates the relationship between the fuel injection pattern of the fuel injection device (e.g., fuel injection amount, number of fuel injections, fuel injection timing, etc.) and the output of the engine 5. 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.

[0047] The control device 100 constantly calculates the load factor L of the engine 5. Here, the load factor L according to this 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 rotation speed. Specifically, the control device 100 stores in advance a map showing the relationship between the output and the load factor L for each engine rotation speed Nr. The control device 100 calculates the load factor L of the engine 5 based on the engine rotation speed Nr detected by the engine rotation speed detection means 71, the calculated output of the engine 5, and the map.

[0048] The manner in which the control device 100 controls the engine speed and vehicle speed will be described below with reference to FIGS.

[0049] First, in FIG. 6, it is determined whether the control selection switch 80 is "ON" (step S10). If 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 the heavy load mode is selected (step S20). If the heavy load mode is selected, it is further determined whether the light load mode is selected (step S30). If 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 the light load mode is selected (step S40). If 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.

[0050] <Heavy load mode: engine speed increase step> In step S100 shown in FIG. 7, it is determined whether the calculated load factor L is greater than a set heavy load value L1. If the load factor L is greater than the heavy load value L1, it is determined whether the engine speed Nr is smaller than the engine speed upper limit value Nmax (step S105). If the load factor L is equal to or less than the heavy load value L1, the process proceeds to step S120. If in step S105 the engine speed Nr is smaller than the engine speed change upper limit value Nmax, the engine speed change actuator 93 is driven to increase the engine speed Nr (step S110). Then, the process returns to step S100. If in step S105 the engine speed Nr is equal to or greater than the engine speed upper limit value Nmax, the engine speed Nr is maintained at the engine speed upper limit value Nmax, and the process proceeds to step S120.

[0051] <Heavy load mode - speed reduction step> In step S120, it is determined whether the load factor L is greater than the heavy load value L2. If the load factor L is greater than the heavy load value L2, it is determined whether the target vehicle speed Vs is faster than the vehicle speed lower limit Vmin (step S125). If the load factor L is equal to or less than the heavy load value L2, the process proceeds to step S140. If in step S125 the vehicle speed V is faster than the vehicle speed lower limit Vmin, the shift actuator 91 is driven to reduce the vehicle speed V (step S130). The process then returns to step S120. If in step S125 the target vehicle speed Vs is equal to or less than the vehicle speed lower limit Vmin, the target vehicle speed Vs is maintained at the vehicle speed lower limit Vmin and the process proceeds to step S140.

[0052] <Light load mode - Vehicle speed return step> In step S140 shown in FIG. 7, it is determined whether 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 the vehicle speed V and the target vehicle speed Vs are the same (step S145). If the load factor L is equal to or greater than the light load value L3, the engine speed and vehicle speed are maintained because they are within the appropriate load range. If, in step S145, the vehicle speed V is not the target vehicle speed Vs, the shift 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. If, in step S145, the vehicle speed V is the target vehicle speed Vs, the process proceeds to step S160.

[0053] <Light load mode: engine speed reduction step> In step S160, it is determined whether the load factor L is smaller than the light load value L4. If the load factor L is smaller than the light load value L4, it is determined whether the engine speed Nr is greater than the engine speed lower limit value Nmin (step S165). If the load factor L is equal to or greater than the light load value L4, the engine speed and vehicle speed are maintained, and the process returns to the beginning. If the engine speed Nr is greater than the engine speed lower limit value Nmin in step S165, the engine speed change actuator 93 is driven to reduce the engine speed Nr by the change amount set by the engine speed change amount setting dial 82 (step S170). Then, the process returns to S160. If the engine speed Nr is equal to or less than the engine speed lower limit value Nmin in step S165, it is maintained at the engine speed lower limit value Nmin, and the process returns to the beginning.

[0054] <Heavy load mode: engine speed increase step> In step S200 shown in FIG. 8, it is determined whether the load factor L is greater than the heavy load value L1. If the load factor L is greater than the heavy load value L1, it is determined whether the engine speed Nr is less than the engine speed upper limit Nmax (step S205). If the load factor L is equal to or less than the heavy load value L1, the process proceeds to step S220. If the engine speed Nr is less than the engine speed upper limit Nmax in step S205, the engine speed change actuator 93 is driven to increase the engine speed Nr (step S210). Then, the process returns to step S200. If the engine speed Nr is equal to or greater than the engine speed upper limit Nmax in step S205, the process proceeds to step S220.

[0055] <Heavy load mode - speed reduction step> In step S220, it is determined whether the load factor L is greater than the heavy load value L2. If the load factor L is greater than the heavy load value L2, it is determined whether the target vehicle speed Vs is faster than the vehicle speed lower limit Vmin (step S225). If the load factor L is equal to or less than the heavy load value L2, the process returns to the beginning. If in step S225 the target vehicle speed Vs is greater than the vehicle speed lower limit Vmin, the shift actuator 91 is driven to reduce the vehicle speed V (step S230). Then, the process returns to step S220. If in step S225 the target vehicle speed Vs is equal to or less than the vehicle speed lower limit Vmin, the process returns to the beginning.

[0056] <Light load mode: engine speed reduction step> In step S300 shown in FIG. 9, it is determined whether the load factor L is smaller than the light load value L4. If the load factor L is smaller than the light load value L4, it is determined whether the engine speed Nr is greater than the engine speed lower limit value Nmin (step S305). If the load factor L is equal to or greater than the heavy load value L4, the process returns to the beginning. If in step S305 the engine speed Nr is greater than the engine speed lower limit value Nmin, the engine speed change actuator 93 is driven to reduce the engine speed Nr by the change amount set by the engine speed change amount setting dial 82 (step S310), and the process returns to step S300. If in step S305 the engine speed Nr is equal to or less than the engine speed lower limit value Nmin, the process returns to the beginning.

[0057] <No mode selection, speed reduction step> In step S400 shown in FIG. 10, it is determined whether the load factor L is greater than the heavy load value L2. If the load factor L is greater than the heavy load value L2, it is determined whether the target vehicle speed Vs is faster than the vehicle speed lower limit Vmin (step S405). If the load factor L is equal to or less than the heavy load value L2, the process returns to the beginning. If in step S405 the target vehicle speed Vs is greater than the vehicle speed lower limit Vmin, the shift actuator 91 is driven to reduce the vehicle speed V (step S410). Then, the process returns to step S400. If in step S405 the target vehicle speed Vs is equal to or less than the vehicle speed lower limit Vmin, the process returns to the beginning.

[0058] An example of the changes over time in the load factor L, engine speed Nr, and vehicle speed V when engine speed and vehicle speed control is performed will be described below with reference to Figure 11. In this example, the control selection switch 80 is in the "ON" state, and the heavy load mode and light load mode are selected. Below, a case will be described in which the heavy load value L1 is equal to the heavy load value L2, and the light load value L3 is equal to the light load value L4.

[0059] If the load factor L increases and remains greater than the heavy load value L1 for an infinitesimal time d1 from the time (T1) when the load factor L exceeds the heavy load value L1, the engine speed Nr is increased by driving the engine speed change actuator 93. The length of the infinitesimal time d1 can be changed and can also be set to 0. The rate at which the engine speed Nr is increased is determined based on the state of the auxiliary transmission mechanism 43. Next, even if the engine speed Nr remains greater than or equal to the engine speed upper limit Nmax for an infinitesimal time d2 from the time (T2) when the engine speed Nr exceeds the engine speed upper limit Nmax, the load factor L is greater than the heavy load value L2 (L1), so the vehicle speed V is reduced.

[0060] The length of the infinitesimal time d2 can be changed and can be set to 0. The rate at which the vehicle speed V is reduced is determined based on the state of the auxiliary transmission mechanism 43. The reduction in the vehicle speed V continues until time T3 when the load factor L becomes equal to or less than the heavy load value L2 (L1). After time T3, the engine speed Nr remains at the upper limit change value, and the vehicle speed V is maintained at the reduced speed at time T3. Furthermore, if the load factor L remains smaller than the light load value L3 for the infinitesimal time d3 from time T4 when the load factor L becomes smaller than the light load value L3, the vehicle speed V differs from the target vehicle speed Vs. Therefore, the vehicle speed V is increased to return to the target vehicle speed Vs. The length of the infinitesimal time d3 can be changed and can be set to 0. If the load factor L remains smaller than the light load value L4 (L3) for the infinitesimal time d4 even at time T5 when the vehicle speed V becomes equal to the target vehicle speed Vs, the engine speed Nr is reduced by driving the engine speed change actuator 93. The length of the minute time d4 can be changed and can also be set to 0. The speed at which the engine speed Nr is increased is determined based on the state of the subtransmission mechanism 43. The engine speed Nr continues to decrease until time T6 when the load factor L becomes equal to or greater than the light load value L4 (L3), and after time T6, the engine speed Nr remains at the decreased engine speed at time T6, and the vehicle speed V remains at the target vehicle speed Vs.

[0061] In addition, when the engine speed change amount setting dial 82 is operated during 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 engine speed Nr is changed so that it is equal to or less than the changed engine speed upper limit value Nmax or equal to or more than the changed engine speed lower limit value Nmin.

[0062] 12, in the case where the engine speed Nr is increased from T7 and raised to N1 (at time T8) and the engine speed is maintained at N1, if the engine speed upper limit Nmax is reduced from Nmax1 to Nmax2 by operating the engine speed change amount setting dial 82 at time T9, the engine speed change actuator 93 is driven from T9 to gradually reduce the engine speed Nr until it reaches Nmax2. Then, when the engine speed Nr reaches Nmax2 at time T10, the engine speed and vehicle speed control are performed again.

[0063] Furthermore, when the engine speed setting means 70 is operated during engine speed and vehicle speed control to change the target engine speed Ns, the engine speed Nr at that time is increased or decreased by the amount of increase or decrease in the target engine speed Ns. For example, as shown in Fig. 13, in a case where the engine speed Nr is increased from T11 and the engine speed Nr is increased from target engine speed Ns1 to N2 (T12), and the engine speed Nr is maintained at N2, when the target engine speed Ns is increased from Ns1 to Ns2 by operating the engine speed setting means 70 at T13, the engine speed Nr is gradually increased by the difference d between Ns2 and Ns1 from T13 by driving the engine speed change actuator 93. Then, when the engine speed Nr reaches N2+d at T14, the engine speed Nr is maintained as is.

[0064] Furthermore, when the engine speed setting means 70 is operated, the engine speed and vehicle speed control are temporarily suspended. That is, when the target engine speed Ns fluctuates, the load factor L fluctuates greatly, so the engine speed and vehicle speed control are temporarily suspended.

[0065] Furthermore, when the control selection switch 80 is changed from "on" to "off" by operating the control selection switch 80 during engine speed and vehicle speed control, the engine speed change actuator 93 and the gear change actuator 91 are driven to gradually return the engine speed Nr and the vehicle speed V to the target engine speed Ns and the target vehicle speed Vs.

[0066] As described above, the tractor 1 is a tractor including the engine rotation speed detection means 71, the engine rotation speed setting means 70, the engine rotation speed changing actuator 93, the vehicle speed detection means 61, the continuously variable transmission 41a, the speed change actuator 91 that changes the speed of the continuously variable transmission 41a, the control device 100 as a load detection means, the engine rotation speed detection means 71, and the output detection means 74, and the control device 100 that controls the engine rotation speed and the vehicle speed. When the engine load factor L becomes larger than the set heavy load value L1, the engine rotation speed is changed while the vehicle speed V is kept constant. The heavy load mode controls the engine speed changing actuator 93 and the gear change actuator 91 to decrease the vehicle speed V when the engine load factor L becomes greater than a set heavy load value L2 while increasing the engine speed Nr up to the engine speed upper limit value Nmax, and the engine load factor L becomes greater than a set heavy load value L2. The light load mode controls the engine speed changing actuator 93 and the gear change actuator 91 to decrease the engine speed Nr while maintaining a constant vehicle speed V when the engine load factor L becomes less than a set light load value L4. With this configuration, when the heavy load mode is selected under heavy load, the engine speed Nr is increased and the vehicle speed V is decreased, preventing engine stalls and improving work efficiency. When the light load mode is selected under light load, the engine speed Nr is decreased by the engine speed changing actuator 93, enabling the vehicle to travel with low fuel consumption.

[0067] The machine also includes an engine speed change amount setting dial 82 and a vehicle speed change amount setting dial 83 that can arbitrarily change the amount of change in engine speed Nr and vehicle speed V in heavy load mode and light load mode. With this configuration, the amount of change in engine speed Nr and vehicle speed V in each mode can be changed according to the user's preferences, work style, and field conditions, thereby improving work efficiency.

[0068] Also provided is a mode operation switch 81 that turns on or off the heavy load mode or light load mode, thereby turning on or off the control of the engine speed change actuator 93. With this configuration, the heavy load mode or light load mode can be selected as desired by the user by turning the mode operation switch 81 on or off.

[0069] Furthermore, the set heavy load values ​​L1 and L2 and the set light load values ​​L3 and L4 in the heavy load mode and light load mode can be changed using the threshold setting dial 84. With this configuration, the threshold values ​​in each mode can be changed according to the user's preferences, work style, and field conditions, thereby improving work finish and preventing engine stalls.

[0070] The vehicle also includes an auxiliary transmission mechanism 43 as setting means for setting the engine rotation speed change rate and vehicle speed change rate in the heavy load mode and light load mode. This configuration makes it possible to change the threshold value for each mode according to the user's preferences, work style, and field conditions, thereby improving work finish and preventing engine stalls.

[0071] Also provided is a display unit 85 that displays the heavy load mode and light load mode. With this configuration, the working vehicle setting state can be easily confirmed.

[0072] <Notes on the invention> In one embodiment, the work vehicle is equipped with a control device that controls engine speed and vehicle speed, and an engine speed change amount setting means that can set an allowable amount of engine speed reduction from the engine speed set by the accelerator lever, and the control device executes control to reduce the engine speed within the allowable amount while maintaining a constant vehicle speed when the engine load is lighter than a predetermined load value, while temporarily suspending execution of the control based on operation of the accelerator pedal.

[0073] According to this aspect, when the load is light, the work vehicle can be driven with low fuel consumption by reducing the engine speed while maintaining a constant vehicle speed. In addition, engine stalling can be prevented, improving the work efficiency of the work vehicle.

[0074] In addition, a work vehicle according to one embodiment is equipped with an engine speed setting means for setting the engine speed, and a status display means for displaying whether a control mode for reducing the engine speed from the set speed set by the engine speed setting means is enabled or disabled while maintaining a constant vehicle speed.

[0075] A work vehicle according to one aspect of the present invention includes a control device that controls an engine speed, and when a predetermined condition is satisfied, the control device executes control to reduce the engine speed within an allowable range, and when a control mode for reducing the engine speed is switched from enabled to disabled, the control device stops the control. [Explanation of symbols]

[0076] 1 Tractor 5 Engine 61 Vehicle speed detection means 70 Engine speed setting means 71 Engine revolution speed detection means 80 Control selection switch 81 Mode operation switch 82 Engine RPM change amount setting dial 83 Speed ​​change amount setting dial 84 Threshold setting dial 85 Display section 91 Variable speed actuator 93 Engine speed change actuator 100 control device

Claims

1. A control device for controlling the engine speed is provided. The control device When a predetermined condition is satisfied, a control is executed to reduce the engine rotation speed within a range of an allowable amount, The engine speed control device further includes a change amount display means for displaying a change amount when the engine speed is reduced. Work vehicle.

2. further comprising a change amount setting means for changing the amount of reduction; the change amount display means displays the reduction amount after the change by the change amount setting means. The work vehicle according to claim 1 .

3. The control device returns the engine rotation speed to a set value when the control is stopped. The work vehicle according to claim 1 or 2.

4. The control device maintains a constant vehicle speed while executing the control. A work vehicle according to any one of claims 1 to 3.

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