JP7547307B2 - Work vehicles - Google Patents

Description

The present invention relates to work vehicle technology.

Traditionally, it is known that in work vehicles such as tractors, the rotational power of the engine is transmitted to the traveling gear via a continuously variable transmission. The work vehicle is equipped with an accelerator lever or accelerator pedal, which is an engine speed setting means for setting the engine speed during normal operation. Work vehicles are also known that change the vehicle speed during operation according to the engine load, which is represented by the engine load rate, engine down amount, traction torque, or the like. When the engine load is large (heavy load), the vehicle speed is slowed down to prevent the engine from stalling. When the engine load is small (light load), the vehicle speed is increased to improve driving performance.

JP 2007-315472 A

However, while increasing the vehicle speed under light load improves driving performance, the engine speed also increases more than necessary, making it impossible to improve fuel economy.

In view of the above problems, the present invention aims to provide a work vehicle that can run with low fuel consumption under light loads and improve work efficiency.

The problem that the present invention aims to solve is as described above, and the means for solving this problem will be explained next.

A work vehicle according to one aspect of the present invention includes 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.

1 is an overall side view of a tractor according to an embodiment of the present invention; FIG. FIG. 2 is a block diagram showing a configuration related to control of the tractor. FIG. FIG. FIG. 4 is a first flowchart showing a control mode of engine speed and vehicle speed control. FIG. 5 is a second flowchart showing the control manner of the engine speed and vehicle speed control. FIG. 7 is a third flowchart showing the control manner of the engine speed and vehicle speed control. FIG. 4 is a fourth flowchart showing the control manner of engine speed and vehicle speed control. FIG. 5 is a fifth flowchart showing the control manner of engine speed and vehicle speed control. FIG. 4 is a graph showing the relationship between load, engine speed, and vehicle speed and time. 6 is a graph showing the relationship between engine speed and time when the upper limit of the engine speed is changed; 6 is a graph showing the relationship between engine speed and time when the target engine speed is changed;

Next, we will explain the overall configuration of the tractor 1 according to one embodiment of the present invention.

As shown in FIG. 1, in the tractor 1, the body frame 2 is arranged with its lengthwise 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 provided at the front of the body frame 2 and is covered by a bonnet 6. A transmission case 7 that houses 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 inside the cabin 8, a driving operation unit 10 is provided for an operator to ride in and operate the tractor 1. In the driving operation unit 10, a steering wheel 11 is disposed at the front, and a seat 12 is disposed behind the steering wheel 11. A gear ratio setting means 63, a position lever (or a 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 a 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). An accelerator pedal (engine speed setting means 70), a brake pedal, a main clutch pedal, a differential lock pedal, etc. are disposed on the step below and in front of the seat 12.

The working machine connecting device 20 mainly comprises a top link 21, lower links 22, and lift rods 23. The top link 21 is rotatably connected to a top link bracket fixed to the rear of the transmission case 7. The lower links 22 are rotatably connected to both sides of the transmission case 7 or the rear axle housing. One end of the lift rods 23 is rotatably connected to the middle of the front and rear of the lower links 22, and the other end is rotatably connected to lift arms 24 protruding rearward from the hydraulic case. A position sensor is disposed at the rotation base of the lift arm 24, which serves as the lift position detection means 73. In this embodiment, a rotary tiller 30 is connected to the rear ends of the top link 21 and the lower links 22 as a working machine. However, the working machine is not limited to the rotary tiller 30, and a chemical sprayer, mower, rake, etc. 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, etc. The tilling claws 31, 31... are radially planted at appropriate intervals on a tine shaft 35 that is horizontally suspended so as to be freely rotatable in the left-right direction, and the tilling cover 32 is arranged to cover the upper and lateral sides of the rotation trajectory 36 of the tips of the tilling claws 31, 31.... The front end of the rear cover 33 is rotatably connected to the rear end of the tilling cover 32, and the rotation of the rear cover 33 is detected by a cover angle sensor that serves as a tilling depth detection means 66. The tine shaft 35 is linked to a PTO shaft 49 that protrudes rearward from the rear surface of the transmission case 7 via a chain case 34, a universal joint, etc. (see FIG. 2).

2, the power of the engine 5 is transmitted to the rear wheels 4, 4 through the main transmission mechanism 41, the forward/reverse switching mechanism 42, the auxiliary transmission mechanism 43, the rear wheel differential mechanism 44, etc., and the power of the engine 5 is transmitted to the front wheels 3, 3 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, etc. The continuously variable transmission 41a of the main transmission mechanism 41 is composed of a hydraulic continuously variable transmission, but is not limited to this, and can be composed of a belt type or toroidal type CVT, etc. As a result, the front wheels 3, 3 and the rear wheels 4, 4 are rotated and the tractor 1 runs. The power of the engine 5 is also transmitted to the claw shaft 35 of the rotary tilling device 30 through the PTO clutch mechanism 47, the PTO transmission mechanism 48, the PTO shaft 49, etc., in order. This causes the tilling tines 31, 31... to rotate together with the tine shaft 35, and tilling work is carried out.

Next, we will explain the configuration related to the control of tractor 1.

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 switching 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 switching 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. The control device 100 is also connected to a shift actuator 91 and a lift actuator 92.

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 wheels 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 direction of travel of the tractor 1. The forward/reverse switching lever 62 is equipped with a sensor that detects the operating position, and the operating position detected by this sensor is transmitted to the control device 100. The control device 100 transmits a signal to an electromagnetic 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 switching mechanism 42 to "ON" or "OFF". In detail, 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 switched to "ON", when the forward/reverse switching lever 62 is operated to the "reverse" position, the reverse clutch 42b is switched to "ON", and when the forward/reverse switching lever 62 is operated to the "neutral" position, the forward clutch 42a and reverse clutch 42b are switched 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 transmission lever or a speed adjustment dial. The gear ratio setting means 63 is equipped with a sensor that detects the amount of operation, and the amount of operation 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.

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 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, this 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.

The tillage depth setting means 65 sets the tillage depth of the tillage tines 31 in 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 rotated. 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 transmitted to the control device 100 as the target tillage depth.

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 (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.

The PTO switch 67 sets the transmission and cut-off of power to the PTO shaft 49. The PTO switch 67 is equipped with a sensor that detects the operating position, and the operating position detected by this sensor is sent to the control device 100. The control device 100 operates the hydraulic actuator by sending a signal to an electromagnetic valve based on the operating positions of the PTO switch 67 and a PTO changeover dial 69 (described later), and turns the PTO clutch 47a of the PTO clutch mechanism 47 and the PTO brake 47b, which operates in opposition to the PTO clutch 47a, "ON" or "OFF."

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 meshing of the transmission gears in the PTO transmission mechanism 48. In this embodiment, the PTO lever 68 can be operated to the "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 the operating position, and the operating position detected by this sensor is transmitted to the control device 100.

The PTO switch dial 69 switches the operating mode of the PTO clutch mechanism 47. The PTO switch dial 69 is equipped with a sensor that detects the operating position, and this sensor is connected to the control device 100. The PTO switch dial 69 can be switched to the "linked", "independent", or "lift-linked" 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 is equipped with a sensor such as a potentiometer that detects the amount of operation, and the amount of operation detected by this sensor is transmitted to the control device 100 as the target engine speed Ns.

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

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

The lift position detection means 73 detects the height of the rotary tilling device 30 relative to the vehicle body of the tractor 1 and is located 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 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 sent 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 can be anything that can detect the output of the engine 5.

In this embodiment, the load detection means is composed of the control device 100 and the engine speed detection means 71. The control device 100 calculates the load rate 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 rate L of the engine 5, but is not limited to this, and may detect the load by calculating, for example, the engine down amount or the traction torque, etc.

The control selection switch 80, the mode operation switch 81, the engine RPM change amount setting dial 82, and the vehicle speed change amount setting dial 83 are provided on an operation panel 86, as shown in FIG. 4. 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 in the driving operation unit 10. However, it may be provided on the operation panel 86.

The control selection switch 80 constitutes a selection means for selecting whether the engine speed control and vehicle speed control are "on" or "off." Each time the control selection switch 80 is pressed, the engine speed control and vehicle speed control are switched between "on" and "off."

The mode operation switch 81 constitutes an operating means for turning on and off the heavy load mode and the light load mode. Each time the mode operation switch 81 is pressed, the state is changed in sequence to one of four states: 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". Turning on and off the heavy load mode and the light load mode is indicated by indicator lamps 86b and 86c, respectively.

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.

The engine speed change amount setting dial 82 is a means for setting the allowable amount of 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, no engine speed control is performed regardless of the selection of "on" or "off" by the control selection switch 80 and the selection of the mode by the mode operation switch 81.

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 deceleration rate is set to 0% by operating the vehicle speed change amount setting dial 83, vehicle speed control is not performed regardless of the selection of "on" or "off" by the control selection switch 80 and the selection of the mode by the mode operation switch 81.

The threshold setting dial 84 constitutes a threshold setting means for changing the first heavy load value L1, the second heavy 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 light 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 light load value L2 may be equal values. The first light load value L3 is the upper limit load value at which the changed vehicle speed is restored to its original value 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 value at which the engine speed starts to increase and the vehicle speed starts to decrease in the heavy load mode, or a threshold value at which the engine speed starts to decrease and the vehicle speed starts to increase in the light load mode.

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 the operation of the control selection switch 80, and turns off the indicator lamp 85a when the control selection switch 80 is "off". In addition, the display lamp 86a turns on when the control selection switch 80 is "on" by the operation of the control selection switch 80, and turns off when the control selection switch 80 is "off". In addition, when the control selection switch 80 is "on", the indicator lamp 85a is also turned on at the same time. The position of the indicator lamp 85a is not limited. In addition, the display lamps 86b and 86c are turned on or off by the operation of the mode operation switch 81 to indicate whether the heavy load mode or the light load mode is selected.

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 is turned on when the engine speed is actually increasing or decreasing by a certain amount. In this embodiment, a lamp is provided that is turned on when the engine speed is increasing by 50 rpm or decreasing by 50 rpm. The display unit 85 is also provided with a liquid crystal unit 85b, and when the vehicle speed is decreasing by a certain amount, the liquid crystal unit 85b displays 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 unit 85b.

The engine speed change speed in 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 speed at which the engine speed is increased is increased. Also, when the sub-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 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.

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.

The lifting actuator 92 raises and lowers the rotary tilling device 30 relative to the vehicle body. The lifting actuator 92 is composed of a hydraulic cylinder that rotates the lift arms 24, 24, and an electromagnetic 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 tilling device 30.

The engine speed change actuator 93 changes the engine speed. In the case of an electronic governor, the engine speed change actuator 93 is a rack actuator, and in the case of a common rail type, it is composed of an injector. The engine speed change 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 change actuator 93 so that the engine speed Nr matches the target engine speed Ns.

The control mode of the tractor 1 is explained in detail below.

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.

The control device 100 constantly calculates the load factor L of the engine 5. Here, the load factor L in 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.

Below, the manner in which the control device 100 controls the engine speed and vehicle speed will be explained with reference to Figures 6 to 9.

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. 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.

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

<Heavy load mode/vehicle 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 the vehicle speed V is faster than the vehicle speed lower limit Vmin in step S125, the shift actuator 91 is driven to reduce the vehicle speed V (step S130). Then, the process returns to step S120. If the target vehicle speed Vs is equal to or less than the vehicle speed lower limit Vmin in step S125, the target vehicle speed Vs is maintained at the vehicle speed lower limit 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 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 since they are within the appropriate load range. In step S145, if 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. In step S145, if 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 the load rate L is smaller than the light load value L4. If the load rate L is smaller than the light load value L4, it is determined whether the engine speed Nr is larger than the engine speed lower limit value Nmin (step S165). If the load rate L is equal to or larger 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 larger 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 smaller than the engine speed lower limit value Nmin in step S165, the engine speed Nr is maintained at the engine speed lower limit value Nmin, 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 the load rate L is greater than the heavy load value L1. If the load rate 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 value Nmax (step S205). If the load rate 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 value 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 value Nmax in step S205, the process proceeds to step S220.

<Heavy load mode/vehicle 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 the target vehicle speed Vs is greater than the vehicle speed lower limit Vmin in step S225, the shift actuator 91 is driven to reduce the vehicle speed V (step S230). Then, the process returns to step S220. If the target vehicle speed Vs is equal to or less than the vehicle speed lower limit 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 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 larger than the engine speed lower limit value Nmin (step S305). If the load factor L is equal to or larger than the heavy load value L4, the process returns to the beginning. If the engine speed Nr is larger than the engine speed lower limit value Nmin in step S305, 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 the engine speed Nr is equal to or smaller than the engine speed lower limit value Nmin in step S305, the process returns to the beginning.

<No mode selection/vehicle 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 the target vehicle speed Vs is greater than the vehicle speed lower limit Vmin in step S405, the shift actuator 91 is driven to reduce the vehicle speed V (step S410). Then, the process returns to step S400. If the target vehicle speed Vs is equal to or less than the vehicle speed lower limit Vmin in step S405, the process returns to the beginning.

Below, 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 are performed will be described with reference to FIG. 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.

When the load rate L increases and remains greater than the heavy load value L1 for a short time d1 from the time (T1) when the load rate L exceeds the heavy load value L1, the engine speed change actuator 93 is driven to increase the engine speed Nr. The length of the short time d1 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 sub-transmission mechanism 43. Next, even if the engine speed Nr remains greater than the engine speed upper limit value Nmax for a short time d2 from the time (T2) when the engine speed Nr exceeds the engine speed upper limit value Nmax, the load rate L is greater than the heavy load value L2 (L1), so the vehicle speed V is reduced.

The length of the minute time d2 can be changed and can be set to 0. The speed at which the vehicle speed V is reduced is determined based on the state of the sub-transmission mechanism 43. The reduction in the vehicle speed V continues until the time (T3) when the load rate L becomes equal to or less than the heavy load value L2 (L1), and after T3, the engine speed Nr is maintained at the upper limit value and the vehicle speed V is maintained at the reduced speed at the time T3. Furthermore, if the load rate L is smaller than the light load value L3 for the minute time d3 from the time (T4) when the load rate L becomes smaller than the light load value L3, the vehicle speed V is different from the target vehicle speed Vs, so 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 0. If the load rate L is smaller than the light load value L4 (L3) for the minute time d4 even at the 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 infinitesimal 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 the time (T6) when the load factor L becomes equal to or greater than the light load value L4 (L3), and after T6, the engine speed Nr is maintained at the decreased engine speed at the time T6, and the vehicle speed V is maintained at the target vehicle speed Vs.

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.

For example, as shown in FIG. 12, in the case where the engine speed Nr is increased from T7 and increased to N1 (T8), and the engine speed is maintained at N1, when the engine speed upper limit value Nmax is decreased from Nmax1 to Nmax2 by operating the engine speed change amount setting dial 82 at T9, the engine speed change actuator 93 is driven from T9 to gradually decrease the engine speed Nr until it reaches Nmax2. Then, when the engine speed Nr reaches Nmax2 at T10, engine speed and vehicle speed control are performed again.

In addition, when the engine speed setting means 70 is operated during engine speed and vehicle speed control to change the target engine speed Ns, the increase or decrease in the target engine speed Ns is added or subtracted from the engine speed Nr at that time. For example, as shown in FIG. 13, in the case where the engine speed Nr is increased from T11 and the engine speed Nr is maintained at N2 from the time point (T12) when the engine speed Nr is increased from the target engine speed Ns1 to N2, and 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 becomes N2+d at T14, the engine speed Nr is maintained as it is.

In addition, when the engine speed setting means 70 is being operated, the engine speed and vehicle speed control are temporarily suspended. In other words, when the target engine speed Ns fluctuates, the load factor L fluctuates greatly, so the engine speed and vehicle speed control are temporarily suspended.

In addition, 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 shift actuator 91 are driven to gradually return the engine speed Nr and vehicle speed V to the target engine speed Ns and target vehicle speed Vs.

As described above, the tractor 1 is equipped with an engine speed detection means 71, an engine speed setting means 70, an engine speed change actuator 93, a vehicle speed detection means 61, a continuously variable transmission 41a, a speed change actuator 91 that changes the speed of the continuously variable transmission 41a, a control device 100 as a load detection means, an engine speed detection means 71, and an output detection means 74, and a control device 100 that controls the engine speed and vehicle speed. When the engine load rate L becomes greater than the set heavy load value L1, the engine speed is changed while maintaining the vehicle speed V constant. The heavy load mode controls the engine speed change actuator 93 and the shift actuator 91 to decrease the vehicle speed V when the engine load factor L becomes greater than the set heavy load value L2 while increasing the engine speed Nr to the engine speed upper limit value Nmax, and controls the engine speed change actuator 93 and the shift actuator 91 to decrease the vehicle speed V when the engine load factor L becomes smaller than the set light load value L4. By configuring in this way, 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. Also, when the light load mode is selected under light load, the engine speed Nr is decreased by the engine speed change actuator 93, allowing the vehicle to run with low fuel consumption.

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. This configuration allows the amount of change in engine speed Nr and vehicle speed V in each mode to be changed according to the user's preferences, work style, and field conditions, improving work efficiency.

The system also includes a mode operation switch 81 that turns on and off the control of the engine speed change actuator 93 by turning on and off the heavy load mode or light load mode. With this configuration, the user can freely select the heavy load mode or light load mode according to their preference by turning the mode operation switch 81 on and off.

The heavy load values L1 and L2 set in the heavy load mode and the light load values L3 and L4 set in the light load mode can be changed by the threshold setting dial 84. By configuring it in this way, the thresholds in each mode can be changed according to the user's preferences, the type of work, and the condition of the field, improving the work finish and preventing engine stalls.

The system also includes a sub-transmission mechanism 43 as a setting means for setting the engine speed change speed and vehicle speed change speed in the heavy load mode and light load mode. This configuration allows the thresholds for each mode to be changed according to the user's preferences, the type of work, and the condition of the field, improving the work finish and preventing engine stalls.

It also has a display unit 85 that displays the heavy load mode and the light load mode. This configuration makes it easy to check the working vehicle setting status.

<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 to be reduced from the engine speed set by an 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.

According to this aspect, when the load is light, the vehicle speed is maintained constant while the engine speed is reduced, allowing the work vehicle to run with low fuel consumption. In addition, engine stalls can be prevented, improving the work efficiency of the work vehicle.

REFERENCE SIGNS LIST 1 Tractor 5 Engine 61 Vehicle speed detection means 70 Engine speed setting means 71 Engine speed detection means 80 Control selection switch 81 Mode operation switch 82 Engine speed change amount setting dial 83 Vehicle speed change amount setting dial 84 Threshold setting dial 85 Display unit 91 Speed change actuator 93 Engine speed change actuator 100 Control device

Claims (4)

An engine speed setting means for setting an engine speed;
a state 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;
A change amount setting means is provided for changing the amount of reduction when the engine speed is reduced.
Work vehicle. a reduction state display means for displaying whether the engine speed is reduced from the set speed when the control mode is enabled,
A work vehicle according to claim 1. Further, a selection means is provided for switching the control mode between enabled and disabled in response to an operation of an operation means.
A work vehicle according to claim 1 or 2 . In the control mode, when the engine load is lighter than a predetermined load value, the engine speed is reduced from the set speed.
A work vehicle according to any one of claims 1 to 3 .