JP4949805B2 - Work vehicle - Google Patents

Description

  The present invention relates to a work vehicle.

  A work vehicle such as a wheel loader is usually provided with an accelerator for adjusting the speed of the vehicle (see Patent Document 1). When the operator operates the accelerator, the engine speed command value is determined according to the accelerator operation amount, and the engine speed is changed. Thereby, the speed of the vehicle can be adjusted.

Here, the engine speed command value increases as the accelerator operation amount increases, and becomes maximum when the accelerator operation amount reaches the maximum operation amount.
Japanese Patent Laid-Open No. 2006-36002

  In general, the maximum speed of a work vehicle is smaller than that of a normal passenger car, for example, there is a maximum speed at 30 to 40 km / h. For this reason, when a work vehicle travels with a normal passenger car on a general road, it is often necessary to maintain the travel at the maximum speed of the work vehicle. In this case, in the conventional work vehicle as described above, the operator needs to keep the state where the amount of operation of the accelerator is maximized, and fatigue increases.

  An object of the present invention is to provide a work vehicle that can reduce operator fatigue.

A work vehicle according to a first aspect of the present invention is operated by a hydraulic pump, a work machine driven by pressure oil discharged from the hydraulic pump, an engine that outputs driving force for driving the hydraulic pump and the vehicle, and an operator. An accelerator, an accelerator operation amount detection unit that detects an operation amount of the accelerator, an engine speed determination unit that determines an engine speed command value according to the operation amount of the accelerator detected by the accelerator operation amount detection unit, An engine control unit that controls the engine speed based on the engine speed command value determined by the engine speed determination unit, and a vehicle speed detection unit that detects the vehicle speed. Then, the engine speed determining unit determines the engine speed command value so that the engine speed command value is maximized when the accelerator operation amount is the maximum operation amount, and the accelerator operation amount. When the first operation amount is smaller than the maximum operation amount, it is possible to switch between the second control mode for determining the engine speed command value so that the engine speed command value becomes maximum. In addition, the engine speed determination unit, when the vehicle speed detected by the vehicle speed detection unit is equal to or higher than a reference speed smaller than the maximum speed that the vehicle can output , and the accelerator operation amount reaches the maximum operation amount, Switch from the first control mode to the second control mode.

  In this work vehicle, the control mode for determining the engine speed command value can be switched between the first control mode and the second control mode. In the first control mode, the engine speed command value is maximized when the accelerator operation amount is the maximum operation amount, while in the second control mode, the engine rotation is performed when the accelerator operation amount is the first operation amount. The numerical command value becomes the maximum. Since the first operation amount is smaller than the maximum operation amount, in the second control mode, the operator does not need to operate the accelerator to the maximum operation amount, and the engine speed command is made with a smaller operation amount than in the first control mode. The value can be maximized. Thereby, in this work vehicle, operator fatigue can be reduced.

  Further, in this work vehicle, when the vehicle speed is equal to or higher than the reference speed and the accelerator operation amount reaches the maximum operation amount, the first control mode is switched to the second control mode. For this reason, it can switch to the 2nd control mode in the situation where the amount of operation of an accelerator becomes large.

  Further, in this work vehicle, the engine speed command value is maintained at the maximum value at the moment of switching from the first control mode to the second control mode. For this reason, it is possible to prevent the engine speed command value from changing discontinuously when switching from the first control mode to the second control mode, and to suppress a sudden change in the vehicle speed.

  A work vehicle according to a second aspect is the work vehicle according to the first aspect, wherein the engine speed determination unit is configured such that the vehicle speed detected by the vehicle speed detection unit is smaller than a reference speed and the accelerator operation amount is greater than the first operation amount. When the small second operation amount is reached, the second control mode is switched to the first control mode.

  In this work vehicle, when the vehicle speed is equal to or higher than the reference speed and the accelerator operation amount reaches a second operation amount smaller than the first operation amount, the second control mode is switched to the first control mode. For this reason, it is possible to switch to the first control mode in a situation where the accelerator operation amount may be small.

  The work vehicle according to a third aspect of the present invention is the work vehicle of the second aspect, wherein the second operation amount is an accelerator operation amount that minimizes the engine speed command value.

  In this work vehicle, the engine speed command value is maintained at the minimum value at the moment of switching from the second control mode to the first control mode. Therefore, it is possible to prevent the engine speed command value from changing discontinuously when switching from the second control mode to the first control mode, and it is possible to suppress a sudden change in the vehicle speed.

  A work vehicle according to a fourth aspect of the present invention is the work vehicle according to any one of the first to third aspects of the present invention, wherein the operation force increasing unit increases the operation force of the accelerator when the operation amount of the accelerator is larger than the first operation amount. Is further provided.

  In this work vehicle, when the operator operates the accelerator and becomes larger than the first operation amount, the operation force of the accelerator increases. For this reason, it is possible to make the operator aware that the amount of operation of the accelerator is large by changing the operation force of the accelerator. Thereby, an operator can be urged for energy-saving operation.

  Further, in this work vehicle, the operation force of the accelerator is increased when the operation amount is greater than the first operation amount, but the engine speed command value is maximized even if the operation amount is not greater than the first operation amount in the second control mode. Therefore, an increase in operator fatigue can be suppressed.

  In the work vehicle according to the present invention, in the second control mode, the operator does not need to operate the accelerator to the maximum operation amount, and maximizes the engine speed command value with a smaller operation amount than in the first control mode. be able to. Thereby, in this work vehicle, operator fatigue can be reduced.

<Configuration>
A work vehicle 1 according to an embodiment of the present invention is shown in FIG. The work vehicle 1 is a hole loader, and includes a vehicle body 2, a work machine 3 attached to the front portion of the vehicle body 2, four tires 4 that rotate while supporting the vehicle body 2 and run the vehicle body 2, A cab 5 mounted on the upper portion of the vehicle body 2 is provided. Further, as shown in FIG. 2, the vehicle body 2 is provided with an engine 11, a transmission 6, a working machine hydraulic pump 7, a steering hydraulic pump 8, a steering cylinder 9, a control unit 10, and the like. Is distributed to the transmission 6, the working machine hydraulic pump 7, the steering hydraulic pump 8, and the like, and becomes the driving force of the working machine 3 and driving. 1 is an external side view of the work vehicle 1, and FIG. 2 is a schematic diagram showing the configuration of a hydraulic circuit and a control system of the work vehicle 1.

  The engine 11 is a diesel engine, and a fuel injection device 12 that controls the output torque and the rotational speed of the engine 11 is attached. Further, the engine 11 is provided with an engine speed detection unit 13 including a rotation sensor that detects the actual rotation speed of the engine 11, and a rotation speed signal from the engine speed detection unit 13 is input to the control unit 10. The The work vehicle 1 is provided with a vehicle speed detector 36. The vehicle speed detection unit 36 is a sensor that detects the vehicle speed of the work vehicle 1, and sends a vehicle speed signal indicating the vehicle speed to the control unit 10.

  A traveling transmission 6 having a torque converter 14 is connected to the output shaft of the engine 11, and the driving force of the engine 11 is transmitted to the tire 4 through the transmission 6. The transmission 6 can switch the reduction ratio in a plurality of stages from high speed to low speed, and the reduction ratio is switched based on an operation signal from the operation unit 15 described later.

  The work machine hydraulic pump 7 is a variable displacement hydraulic pump driven by the output of the engine 11, and the work machine hydraulic pump 7 is operated using the pressure oil discharged from the work machine hydraulic pump 7. A regulator 16 that adjusts the tilt angle of the swash plate of the machine hydraulic pump 7 and an electromagnetic control valve 17 that controls the regulator 16 based on a control current from the control unit 10 are provided. In addition, a pressure sensor 18 that detects the discharge pressure of the work machine hydraulic pump 7 is provided, and a pump discharge pressure signal from the pressure sensor 18 is input to the control unit 10.

  The work machine 3 is a portion that is driven by pressure oil discharged from the work machine hydraulic pump 7, and includes a lift arm 19 attached to the front part of the vehicle body 2 and a bucket attached to the tip of the lift arm 19. 20 and a work machine cylinder 21 (see FIG. 2). The lift arm 19 is an arm member for lifting the bucket 20 attached to the tip. The bucket 20 is attached to the tip of the lift arm 19. The work machine cylinder 21 is a hydraulic actuator that drives the lift arm 19 and the bucket 20 with pressure oil discharged from the work machine hydraulic pump 7.

  The steering hydraulic pump 8 is a variable displacement hydraulic pump driven by the output of the engine 11, and the tilting of the swash plate of the steering hydraulic pump 8 is performed using the pressure oil discharged from the steering hydraulic pump 8. A regulator 22 for adjusting the angle and an electromagnetic control valve 23 for controlling the regulator 22 based on a control current from the control unit 10 are provided. The steering cylinder 9 is driven by the pressure oil discharged from the steering hydraulic pump 8 and changes the traveling direction during traveling. Further, a pressure sensor 24 for detecting the discharge pressure of the steering hydraulic pump 8 is provided, and a pump discharge pressure signal from the pressure sensor 24 is input to the control unit 10.

  The cab 5 is configured by combining a plurality of steel pipes and steel plates, and is provided with an accelerator pedal 25 and an operation unit 15 operated by an operator, a display unit 26 for displaying various information, and the like.

  The accelerator pedal 25 is means for instructing the target rotational speed of the engine 11, and includes a pedal body 28, a pedal support member 29, and a leaf spring 30 as shown in FIG. 3.

  The pedal body 28 is a member operated by an operator's foot, and one end of the pedal body 28 is attached to the floor of the cab 5 so as to be rotatable about the first rotation shaft 31. FIG. 3A shows the state of the accelerator pedal 25 when it is not operated by the operator (hereinafter referred to as “no-operation state”). FIG. 3B shows a state where the accelerator pedal 25 is operated by the first operation amount θA from the non-operation state (hereinafter referred to as “first operation state”). FIG. 3C shows a state where the accelerator pedal 25 is further operated from the first operation state to the maximum operation amount θMax (hereinafter referred to as “maximum operation state”). The first operation amount θA and the maximum operation amount θMax are changes in the operation angle from the no-operation state.

  The pedal support member 29 is a member that supports an intermediate portion of the pedal body 28, and one end of the pedal support member 29 is attached to the pedal body 28 so as to be rotatable about the second rotation shaft 32. A rotating wheel 33 is rotatably attached to the other end of the pedal support member 29 and abuts against an inclined surface 50 provided on the floor surface of the cab 5. In addition, a protrusion 34 that protrudes upward is provided at an intermediate portion of the pedal support member 29. When the pedal body 28 is operated by the operator and pivots about the first rotation shaft 31 (see arrow AW1 in FIG. 3B), the rotating wheel 33 of the pedal support member 29 rolls on the inclined surface 50 and moves. The pedal support member 29 rotates around the second rotation shaft 32 (see arrow AW3 in FIG. 3B) (see arrow AW2 in FIG. 3B). Note that an elastic member (not shown) is attached to the pedal support member 29, and the pedal support member 29 is biased in a direction to return the pedal body 28 to the non-operation state.

  The leaf spring 30 is attached to the back side of the pedal body 28, and functions as an operation force increasing portion that increases the operation force of the accelerator pedal 25 when the operation amount of the accelerator pedal 25 is larger than the first operation amount θA. That is, the leaf spring 30 is rotated so that the pedal body 28 approaches the floor and the inclination angle of the pedal body 28 is changed, so that the leaf spring 30 comes close to the protrusion 34 of the pedal support member 29, as shown in FIG. As shown, when the operation amount of the pedal body 28 becomes the first operation amount θA, the pedal body 28 contacts the protrusion 34. Then, as shown in FIG. 3C, when the operation amount of the pedal body 28 becomes larger than the first operation amount θA, the protrusion 34 presses the leaf spring 30 to be elastically deformed. Thereby, the operating force of the accelerator pedal 25 increases.

  As shown in FIG. 2, an accelerator operation amount detection unit 27 that detects the operation amount of the accelerator pedal 25 is connected to the accelerator pedal 25. The accelerator operation amount detection unit 27 includes a potentiometer that detects the operation position of the accelerator pedal 25, and an opening degree signal indicating the opening amount of the accelerator pedal 25 corresponding to the operation amount of the accelerator pedal 25 is sent to the control unit 10. A control signal is output from the control unit 10 to the fuel injection device 12. Here, the opening degree of the accelerator pedal 25 (hereinafter referred to as “accelerator opening degree”) is “0%” when the accelerator pedal 25 is in the non-operating state, and according to the increase in the operation amount of the accelerator pedal 25. When the accelerator pedal 25 is in the maximum operating state, the value is “100%”.

  The operation unit 15 includes a steering, an operation lever, an operation button, and the like (not shown), and is operated by an operator to change the traveling direction of the work vehicle 1, select a reduction ratio of the transmission 6, and the like.

  The display unit 26 is a display panel disposed in front of a seat inside the cab 5 and is equipped with various pilot lamps that are lit during operation of a device such as a parking brake, a speed meter indicating a traveling speed, a fuel gauge, and a selection. A shift indicator indicating the reduction ratio being displayed is displayed.

  The control unit 10 controls the operation of the work vehicle 1 and controls the fuel injection amount of the fuel injection device 12 based on the opening degree of the accelerator pedal 25 and the actual rotation speed of the engine 11. The control unit 10 performs all speed control and can control the engine speed according to the accelerator opening. All-speed control is a control that regulates speed in almost all speed ranges and load ranges except for the fuel increase range at start-up, and the engine speed can be kept substantially constant even when the load fluctuates. .

  Here, the control unit 10 includes an engine speed determination unit 35. The engine speed determination unit 35 determines an engine speed command value according to the operation amount of the accelerator pedal 25 detected by the accelerator operation amount detection unit 27. That is, the engine speed determination unit 35 determines an engine speed command value based on the opening degree signal sent from the accelerator operation amount detection unit 27 and sends the engine speed command signal to the fuel injection device 12. The fuel injection device 12 functions as an engine control unit that controls the engine speed by adjusting the fuel injection amount based on the engine speed command value determined by the engine speed determination unit 35.

  Hereinafter, the engine speed command value determining method by the engine speed determining unit 35, which is characteristic in the present invention, will be described in detail.

<Determination Method of Engine Speed Command Value by Engine Speed Determination Unit 35>
As shown in FIG. 4, the engine speed determining unit 35 determines the engine speed command value so that the engine speed command value becomes maximum when the accelerator opening is maximum (broken line graph). L2) and the second control mode (see the solid line graph L2) for determining the engine speed command value so that the engine speed command value is maximized when the accelerator opening is the first opening A. Is possible.

  The first opening A is the accelerator opening when the accelerator pedal 25 is operated by the first operation amount θA and is in the first operation state. Further, the minimum opening 0% is the accelerator opening when the accelerator pedal 25 is not operated and is not operated. The maximum opening degree 100% is the accelerator opening degree when the accelerator pedal 25 is operated by the maximum operation amount θMax and is in the maximum operation state.

  In a state where the accelerator opening is minimum, that is, a non-operation state, the engine speed command value is minimum both in the first control mode and in the second control mode. In the state where the accelerator opening is the maximum, the engine speed command value is the maximum in both the first control mode and the second control mode. However, in the first control mode, the engine speed command value increases continuously as the accelerator opening increases from the minimum to the maximum, and the engine speed command value reaches the maximum value when the accelerator opening is at the maximum. . On the other hand, in the second control mode, when the accelerator opening increases from the minimum to the first opening A, the engine speed command value also increases continuously, and the accelerator opening is in the state of the first opening A. The engine speed command value reaches the maximum value. In the second control mode, when the accelerator opening is equal to or greater than the first opening A, the engine speed command value maintains the maximum value.

  The engine speed determining unit 35 is set to determine the engine speed command value in the first control mode in the initial state. The engine speed determining unit 35 switches from the first control mode to the second control mode when the vehicle speed is equal to or higher than a predetermined reference speed and the accelerator opening reaches the maximum opening. Further, the engine speed determination unit 35 switches from the second control mode to the first control mode when the vehicle speed is lower than the reference speed and the accelerator opening is minimized. Note that the reference speed is a speed when the amount of operation of the accelerator pedal 25 is relatively large, such as when the work vehicle 1 is traveling on a general road, not when working on the work site. A speed of about 80 to 90% of the maximum speed of 1 is selected.

<Features>
(1)
In this work vehicle 1, when the engine speed command value is determined in the second control mode during high-speed traveling, the maximum engine speed command value is output by operating the accelerator pedal 25 to the first operation amount θA. be able to. For this reason, it is not necessary to operate the accelerator pedal 25 up to the maximum operation amount θMax during high-speed traveling, and the operator's fatigue can be reduced.

(2)
In this work vehicle 1, when the accelerator pedal 25 is operated to be larger than the first operation amount θA, the operating force of the accelerator pedal 25 is increased by the leaf spring 30. Thereby, it can suppress that an operator operates the accelerator pedal 25 excessively during a work, and can promote an energy-saving driving | operation. Then, as described above, during the high-speed traveling where the operation amount of the accelerator pedal 25 tends to be large, the mode is switched to the second control mode. In the second control mode, the engine rotational speed command value can be maximized in a state where the operating force of the accelerator pedal 25 is not increased by the leaf spring 30, so that an increase in operator fatigue can be suppressed.

(3)
In this work vehicle 1, switching from the first control mode to the second control mode is performed when the vehicle speed is equal to or higher than the reference speed and the accelerator opening is maximized. In the state where the accelerator opening is the maximum, the engine speed command value is the maximum value and the same in both the first control mode and the second control mode. For this reason, at the time of switching from the first control mode to the second control mode, it is possible to suppress a large change in the engine speed command value, and it is possible to suppress a sudden change in the engine speed.

  The switching from the second control mode to the first control mode is performed when the vehicle speed is lower than the reference speed and the accelerator opening is minimized. In the state where the accelerator opening is minimum, the engine speed command value is the minimum value and the same in both the first control mode and the second control mode. For this reason, even when switching from the second control mode to the first control mode, the engine speed command value can be prevented from changing greatly, and the engine speed can be prevented from changing abruptly.

<Other embodiments>
(A)
In the above embodiment, the determination of switching between the first control mode and the second control mode takes into account not only the vehicle speed but also the accelerator opening, but instead of the accelerator opening condition or the accelerator opening condition Other conditions may be taken into account.

(B)
In the above-described embodiment, the work vehicle 1 is provided with a mechanism in which the operating force of the accelerator opening is changed by the leaf spring 30. In such a work vehicle 1, a particularly high operator fatigue reduction effect can be achieved. However, even in a work vehicle 1 that is not equipped with such a mechanism, the engine speed command value is determined by the engine speed determination unit 35 as described above, thereby reducing operator fatigue. it can.

(C)
In the above embodiment, the condition that the accelerator opening is minimized is considered in switching from the second control mode to the first control mode. Instead of this condition, the accelerator opening is set to a predetermined second opening. A condition that the degree B (0 <B <A) or less may be considered. Also in this case, if the engine speed command value in the first control mode and the engine speed command value in the second control mode are the same at the second opening degree B, the engine speed will change rapidly as described above. Can be suppressed.

(D)
In the above-described embodiment, the accelerator pedal 25 that is operated by the operator's foot is provided as an accelerator that adjusts the vehicle speed of the work vehicle 1, but an operating member that is operated by hand such as a lever may be provided. In this case as well, fatigue in the accelerator operation of the operator can be reduced.

(E)
In the above embodiment, the maximum operation amount of the accelerator pedal 25 does not necessarily need to coincide with the maximum value of the movable range of the accelerator pedal 25. For example, when the accelerator pedal 25 is provided with “play”, the maximum operation amount of the accelerator pedal 25 may be smaller than the maximum movable range of the accelerator pedal 25. The same applies to the minimum operation amount of the accelerator pedal 25.

  The present invention has an effect of reducing operator fatigue and is useful as a work vehicle.

The external appearance side view of a working vehicle. Schematic showing the configuration of the hydraulic circuit and control system of the work vehicle Schematic which shows a structure and operation | movement of an accelerator pedal. The graph which shows the relationship between an accelerator opening and an engine speed command value.

DESCRIPTION OF SYMBOLS 1 Work vehicle 11 Engine 12 Fuel injection apparatus (engine control part)
25 Accelerator pedal (Accelerator)
27 Accelerator operation amount detection unit 30 Leaf spring (operation force increasing unit)
35 Engine speed determination unit 36 Vehicle speed detection unit

Claims (4)

A hydraulic pump;
A working machine driven by pressure oil discharged from the hydraulic pump;
An engine that outputs driving force for driving the hydraulic pump and driving the vehicle;
An accelerator operated by an operator;
An accelerator operation amount detector for detecting the operation amount of the accelerator;
An engine speed determination unit that determines an engine speed command value according to the accelerator operation amount detected by the accelerator operation amount detection unit;
An engine control unit for controlling the engine speed based on an engine speed command value determined by the engine speed determination unit;
A vehicle speed detector for detecting the vehicle speed;
With
The engine speed determining unit is configured to determine an engine speed command value so that the engine speed command value is maximized when the accelerator operation amount is a maximum operation amount; When the amount is the first operation amount smaller than the maximum operation amount, it is possible to switch between the second control mode for determining the engine speed command value so that the engine speed command value becomes maximum,
When the vehicle speed detected by the vehicle speed detection unit is equal to or higher than a reference speed that is lower than the maximum speed that the vehicle can output and the operation amount of the accelerator reaches the maximum operation amount, Switching from the first control mode to the second control mode,
Work vehicle. When the vehicle speed detected by the vehicle speed detection unit is smaller than the reference speed and the operation amount of the accelerator reaches a second operation amount smaller than the first operation amount, the engine speed determination unit Switching from the control mode to the first control mode;
The work vehicle according to claim 1. The second operation amount is an operation amount of the accelerator at which the engine speed command value is minimum.
The work vehicle according to claim 2. An operation force increasing unit that increases the operation force of the accelerator when the operation amount of the accelerator is greater than the first operation amount;
The work vehicle according to any one of claims 1 to 3.

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