JP2017172478A - Work vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a work vehicle capable of rapidly increasing a rotating speed of a driving source without troublesome operation, according to driver's intension while preventing increase of the rotating speed of the driving source to an unexpected excessive rotating speed, and improving workability.SOLUTION: A work vehicle includes a driving source disposed on a vehicle body portion, a first setting portion for setting a target rotating speed of the driving source, a second setting portion for setting a target maximum rotating speed of the driving source, and a control portion for controlling the rotating speed of the driving source according to an operation to an operation tool. The control portion controls the rotating speed of the driving source in any of a first rotating speed control mode for controlling the rotating speed of the driving source according to the operation to the operation tool within a range from the target rotating speed to the target maximum rotating speed, and a second rotating speed control mode for controlling the rotating speed of the driving source according to the operation to the operation tool within a range from the target rotating speed to a prescribed rotating speed over the target maximum rotating speed.SELECTED DRAWING: Figure 5

Description

  The present invention provides a drive source provided in a vehicle body, a first setting unit that sets a target rotation speed of the drive source, a second setting unit that sets a target maximum rotation speed of the drive source, and an operation on an operation tool. And a control unit capable of controlling the rotational speed of the drive source in accordance with the operation vehicle.

  The work vehicle as described above is composed of, for example, a tractor capable of mounting a work machine on the vehicle body, an engine as a drive source, an accelerator pedal as an operation tool, and an accelerator lever as a first setting unit. The control unit controls the rotational speed of the engine in accordance with an operation on the accelerator pedal (see, for example, Patent Document 1).

  In the work vehicle described in Patent Document 1, an upper limit setter as a second setting unit is provided, a target rotation speed is set by an accelerator lever, and a target maximum rotation speed is set by an upper limit setter. The control unit controls the engine rotation speed within the range from the target rotation speed to the target maximum rotation speed in accordance with the operation on the accelerator pedal, after controlling the engine rotation speed to the target rotation speed. Thereby, the control part controls the rotational speed of the engine so as not to exceed the target maximum rotational speed. Therefore, for example, even if a driver's operation tool misoperation occurs, the engine rotation speed does not exceed the target maximum rotation speed, preventing the engine rotation speed from being unexpectedly increased to an excessively high rotation speed. it can.

JP 2009-287471 A

  In the work vehicle described in Patent Document 1, the vehicle is traveling while performing work on the ground with a work machine mounted on the vehicle body. However, for example, a large load is generated on the work machine, so that the engine speed decreases. As a result, the work machine may not be able to operate in a desired operating state, or the vehicle body may not be able to perform a desired travel. In addition, the engine may be heavily loaded due to some influence, and engine stall may occur.

  In such a case, the driver depresses the accelerator pedal greatly with the intention of increasing the rotational speed of the engine, and the operation amount for the accelerator pedal is increased. However, in the work vehicle described in Patent Document 1, the engine rotation speed is prevented from exceeding the target maximum rotation speed in order to prevent the rotation speed of the engine from unexpectedly rising to an excessive rotation speed. The engine speed cannot be increased until the target maximum speed is exceeded. Therefore, the engine rotation speed cannot be increased according to the driver's intention, the work implement cannot be operated in a desired operation state, or an engine stall occurs, which may reduce the workability of the work vehicle. is there. Further, in order to set the target maximum rotation speed to a higher rotation speed, it is necessary to perform an operation such as resetting with an upper limit setting device as the second setting unit, which is cumbersome and difficult to respond quickly. It will be a thing.

  In view of this situation, the main problem of the present invention is to prevent the drive source from rotating unexpectedly to an excessively high rotational speed without performing troublesome operations according to the driver's intention. It is in the point which provides the work vehicle which can raise the rotational speed of this quickly and can aim at the improvement of workability | operativity.

A first characteristic configuration of the present invention includes a drive source provided in a vehicle body, a first setting unit that sets a target rotation speed of the drive source, and a second setting unit that sets a target maximum rotation speed of the drive source. A control unit that controls the rotational speed of the drive source in accordance with an operation on the operation tool,
The control unit is configured to control a rotation speed of the driving source in a range from the target rotation speed to the target maximum rotation speed in response to an operation on the operation tool, and to the operation tool. The rotational speed of the drive source is controlled by one of the second rotational speed control modes in which the rotational speed of the drive source is controlled in a range from the target rotational speed to a predetermined rotational speed exceeding the target maximum rotational speed according to an operation. The point is to control.

  According to this configuration, the control unit can control the rotational speed of the drive source in either the first rotational speed control mode or the second rotational speed control mode. In the first rotational speed control mode, since the rotational speed of the drive source is controlled in the range from the target rotational speed to the target maximum rotational speed, for example, even if an erroneous operation of the driver's operation tool or the like occurs, The rotation speed does not exceed the target maximum rotation speed, and the rotation speed of the drive source can be prevented from being unexpectedly increased to an excessive rotation speed. On the other hand, in the second rotational speed control mode, the rotational speed of the drive source is controlled in a range from the target rotational speed to a predetermined rotational speed exceeding the target maximum rotational speed, so it is desired to increase the rotational speed of the drive source. If the amount of operation with respect to the operating tool is increased by the driver with the intention of the driver, the rotational speed of the drive source can be increased to a predetermined rotational speed exceeding the target maximum rotational speed in accordance with the operation. As a result, it is possible to increase the rotation speed of the drive source according to the driver's intention by merely performing an operation on the operation tool while preventing the rotation speed of the drive source from being unexpectedly excessively increased. It is possible to improve workability and operability.

A second characteristic configuration of the present invention includes a power transmission unit that transmits power of the drive source to a traveling unit provided in the vehicle body unit,
The control section controls the power transmission section so that the vehicle speed of the vehicle body section becomes a vehicle speed corresponding to the target rotation speed when the rotation speed of the drive source is the predetermined rotation speed. And a second vehicle speed control mode for controlling the power transmission unit so that the vehicle speed of the vehicle body becomes a vehicle speed corresponding to the target maximum rotation speed when the rotation speed of the drive source is the predetermined rotation speed. The point is to control the vehicle speed of the vehicle body part.

  According to this configuration, the control unit can control the vehicle speed of the vehicle body unit in either the first vehicle speed control mode or the second vehicle speed control mode. In the first vehicle speed control mode, when the rotational speed of the drive source is controlled to a predetermined rotational speed exceeding the target maximum rotational speed in the second rotational speed control mode, power is transmitted so that the vehicle speed corresponds to the target rotational speed. Therefore, the vehicle speed of the vehicle body can be suppressed to a relatively low vehicle speed corresponding to the target rotational speed that is smaller than the target maximum rotational speed. On the other hand, in the second vehicle speed control mode, when the rotation speed of the drive source is controlled to a predetermined rotation speed exceeding the target maximum rotation speed by the second rotation speed control mode, the vehicle speed corresponding to the target maximum rotation speed is determined. Therefore, the vehicle speed of the vehicle body is controlled to a vehicle speed corresponding to the target maximum rotation speed larger than the target rotation speed, and is increased to a vehicle speed higher than that in the first vehicle speed control mode. However, it is possible to prevent the vehicle speed of the vehicle body from excessively increasing to a vehicle speed corresponding to a rotational speed larger than the target maximum rotational speed. Therefore, when the rotational speed of the drive source is controlled in the second rotational speed control mode, the vehicle speed of the vehicle body can be appropriately controlled.

According to a third characteristic configuration of the present invention, the second setting unit sets the target maximum rotation speed to a first rotation speed smaller than the predetermined rotation speed, and smaller than the predetermined rotation speed and the first rotation speed. Can be set to any of the second rotational speeds smaller than the rotational speed,
When the control unit controls the rotation speed of the driving source in the second rotation speed control mode, the second setting unit sets the target maximum rotation speed to the first rotation speed and the second rotation speed. In any case, the rotational speed of the drive source is controlled in a range from the target rotational speed to the predetermined rotational speed in accordance with an operation on the operation tool.

  According to this configuration, the target maximum rotation speed can be set to either the first rotation speed or the second rotation speed, and the first rotation speed and the second rotation speed can be set according to the work content, the work situation, or the like. It is possible to change which of the rotation speeds is set, and work can be performed efficiently. In addition, when the controller controls the rotational speed of the drive source in the second rotational speed control mode, the controller operates regardless of whether the target maximum rotational speed is set to the first rotational speed or the second rotational speed. The rotational speed of the drive source can be increased to a predetermined rotational speed exceeding the target maximum rotational speed in accordance with an operation on the operation tool intended by the user, and workability and operability can be improved.

Overall side view of tractor Block diagram showing the driving transmission system of the tractor The perspective view which shows the principal part of the operation part of a tractor Tractor control block diagram The figure which shows the adjustment range of the rotational speed of the engine in each control mode

An embodiment of a work vehicle according to the present invention will be described with reference to the drawings.
As shown in FIGS. 1 and 2, the tractor 1 as the work vehicle includes a vehicle body portion 2 to which a work machine 60 can be mounted on the rear side, and the front portion of the vehicle body portion 2 is a pair of left and right front wheels 3 (traveling portion). And the rear portion of the vehicle body portion 2 is supported by a pair of left and right rear wheels 4 (corresponding to a traveling portion). A bonnet 5 is disposed in the front part of the vehicle body 2, and an engine 6 as a drive source is accommodated in the bonnet 5. The engine 6 can be configured by, for example, a diesel engine, but is not limited thereto, and may be configured by, for example, a gasoline engine. Further, an electric motor may be employed as a drive source in addition to the engine 6 or instead of the engine 6. A cabin 7 for a driver to board is provided on the rear side of the bonnet 5, and a steering handle 8 for a driver to steer and a driver's driving seat 9 are provided in the cabin 7. It has been. In this embodiment, a tractor is described as an example of a work vehicle. However, as a work vehicle, in addition to a tractor, a rice-type machine, a combiner, a civil engineering / architecture work device, a snowplow, etc. Work vehicles are also included.

  On the rear side of the vehicle body portion 2, a three-point link mechanism including a pair of left and right lower links 10 and an upper link 11 is provided, and the working machine 60 can be mounted on the three-point link mechanism. A lifting device 12 having a hydraulic device such as a lifting cylinder is provided on the rear side of the vehicle body 2, and the lifting device 12 lifts and lowers the work implement 60 by lifting and lowering the three-point link mechanism.

  Here, FIG. 1 exemplifies the case where the reversible plow is mounted on the work machine 60, but not only the reversible plow, but also other work machines such as other plows, tillage devices, fertilizers, etc. are applied. Can do.

  As shown in FIG. 2, the tractor 1 includes, as a transmission system for rotational power from the engine 6, a traveling transmission system 20 that transmits rotational power (power) from the engine 6 to driving wheels, and rotational power from the engine 6. Is provided with a PTO transmission system (not shown). The traveling transmission system 20 is provided in a mission 21 as a power transmission unit.

  The traveling transmission system 20 includes a main transmission 23, a forward / reverse switching device 24, an auxiliary transmission 25, and a drive state switching device 26. The traveling transmission system 20 shifts the rotational power from the engine 6 with the main transmission 23, shifts the rotational power after the shift with the auxiliary transmission 25, and transmits the finally-rotated rotational power to the drive wheels. It is configured as follows.

  The main transmission 23 includes, for example, a swash plate variable discharge hydraulic pump 23a that receives rotational power from the engine 6 and a hydraulic motor 23b that rotates by hydraulic pressure from the hydraulic pump 23a and outputs rotational power. It is comprised by a type | mold continuously variable transmission (HST). When rotational power from the engine 6 is input, pressure oil is supplied from the hydraulic pump 23a to the hydraulic motor 23b, and the hydraulic motor 23b is rotationally driven by the hydraulic pressure from the hydraulic pump 23a to rotate the motor shaft. The main transmission 23 is shifted to any one of the normal rotation state, the reverse rotation state, and the neutral state located between the normal rotation state and the reverse rotation state, and also reverses when the gear is shifted to the normal rotation state. Even when the speed is changed to the rotational state, the rotational speed of the hydraulic pump 23a is changed steplessly, and the rotational speed of the hydraulic motor 23b (number of rotations per unit time) is changed steplessly. The speed change state can be changed steplessly. Incidentally, the main transmission 23 can also be configured by an HMT that combines a hydraulic continuously variable transmission (HST) and a planetary gear mechanism.

  The forward / reverse switching device 24 is a forward state in which the rotational power from the main transmission 23 is output as rotational power in the forward direction, and the reverse state in which the rotational power from the main transmission 23 is output as rotational power in the reverse direction, It can be switched to either a neutral state in which transmission of rotational power from the main transmission 23 is cut off.

  The auxiliary transmission 25 is constituted by, for example, a gear-type multi-stage transmission, and a high-speed state in which the rotational power from the forward / reverse switching device 24 is shifted and output at a high speed, and the rotation from the forward / reverse switching device 24. It is configured to be able to switch to either a low speed state in which power is shifted at a low speed stage and output.

  The drive state switching device 26 transmits the rotational power from the auxiliary transmission device 25 only to the rear wheels 4 via the rear wheel side differential device 27 and uses only the rear wheels 4 as drive wheels, and the auxiliary transmission device. Rotational power from 25 is transmitted to the rear wheel 4 and the front wheel 3 via the rear wheel side differential device 27 and the front wheel side differential device 28, and in either of the four-wheel drive state where the rear wheel 4 and the front wheel 3 are used as driving wheels. It is configured to be selectable.

  As shown in FIG. 4, the tractor 1 is provided with a control unit 40 that can control various devices in accordance with operations of various operation units. Although not shown, various operation units are disposed in the cabin 7 in the vicinity of the steering handle 8 and the driver seat 9. In addition to these operation units, a display unit for displaying various information is also provided on the steering handle. 8 or the like.

  As various operation units, for example, an accelerator pedal 41 (corresponding to an operation tool), an accelerator lever 42 (corresponding to a first setting unit for setting a target rotational speed of the engine 6), an elevating operation unit 43, a main transmission operation unit 44, an auxiliary transmission operation unit 45, a forward / reverse operation unit 46, a maximum setting operation unit 47, a rotation speed / vehicle speed switching operation unit 48, an A mode / B mode switching operation unit 49, and the like. As devices that can be controlled by the control unit 40, a governor device 31, a main transmission 23, a forward / reverse switching device 24, a sub-transmission device 25, an elevating device 12, a drive state switching device 26, and the like are provided.

  The accelerator pedal 41 is used to increase or decrease the rotational speed of the engine 6, and the control unit 40 controls the governor device 31 in accordance with an operation on the accelerator pedal 41 to change the rotational speed of the engine 6 to a desired rotational speed. Can be adjusted. Specifically, the rotational speed of the engine 6 is set in accordance with an operation on the accelerator pedal 41 in a range from a target rotational speed to a target maximum rotational speed, which will be described later, or in a range from the target rotational speed to a predetermined rotational speed. Adjust (control). The accelerator lever 42 is for increasing or decreasing the rotational speed of the engine 6 and is configured to be able to set the target rotational speed of the engine 6. The control unit 40 is configured to be able to adjust the rotational speed of the engine 6 to the target rotational speed set by the accelerator lever 42.

  The main transmission operation unit 44 is for adjusting the transmission state of the main transmission 23, and the control unit 40 controls the main transmission 23 in accordance with the operation of the main transmission operation unit 44 to 23 can be adjusted to a desired shift state. The subtransmission operation unit 45 is for switching the vehicle speed of the vehicle body unit 2 between a high speed state and a low speed state, and the control unit 40 controls the subtransmission device 25 according to the operation of the subtransmission operation unit 45. The auxiliary transmission 25 is switched between the high speed state and the low speed state. The forward / reverse operation unit 46 is for switching whether the vehicle body unit 2 travels forward, travels backward, or blocks transmission of rotational power from the engine 6. The control unit 40 includes a forward / reverse operation unit. The forward / reverse switching device 24 is controlled in accordance with the operation 46 to switch the forward / reverse switching device 24 to any one of the forward, reverse and neutral states.

  The elevating operation unit 43 is for adjusting the height of the work implement 60 mounted on the vehicle body unit 2, and the control unit 40 controls the elevating device 12 according to the operation of the elevating operation unit 43, The height of the work machine 60 can be adjusted. Here, as the raising / lowering operation unit 43, for example, a one-operation type lowering operation unit for adjusting the height of the work machine 60 to a set work height by one operation (one-touch) and a one-operation (one-touch) operation. A one-operation type ascending operation part for adjusting the height of the working machine 60 to a set non-working height, an operation part for arbitrarily adjusting the height of the working machine 60 within a predetermined lifting range, and the like are provided. However, it is illustrated as one lifting operation unit 43.

  Here, before explaining the maximum setting operation unit 47, the rotation speed / vehicle speed switching operation unit 48, the A mode / B mode switching operation unit 49, and the rotation speed control mode selection operation unit 50, a supplementary explanation will be given. As described above, the control unit 40 controls the rotational speed of the engine 6 at the engine target rotational speed set by the accelerator lever 42, but the driver operates the engine 6 at any rotational speed in accordance with the operation of the accelerator pedal 41. It is possible to set whether to increase the rotational speed of the engine 6 or to maintain or increase the vehicle speed as the rotational speed of the engine 6 increases. In the present embodiment, regarding the rotational speed of the engine 6 that rises according to the operation of the accelerator pedal 41, the rotational speed set by the driver is referred to as a target maximum rotational speed, and the vehicle speed set by the driver is also referred to as the target maximum vehicle speed. Called.

  The maximum setting operation unit 47 is a dial type operation unit that is operated when setting the target maximum rotation speed or the target maximum vehicle speed, and corresponds to a second setting unit that sets the target maximum rotation speed of the engine. The second setting unit may include a rotation speed / vehicle speed switching operation unit 48 and an A mode / B mode switching operation unit 49 in addition to the maximum setting operation unit 47. The rotational speed / vehicle speed switching operation section 48 is for switching which of the target maximum rotational speed and the target maximum vehicle speed can be set. The rotational speed / vehicle speed switching operation unit 48 is, for example, a push-type switch that can be switched between “engine rotational speed” and “vehicle speed”, and when “engine rotational speed” is selected, the target maximum When the rotation speed can be set and “vehicle speed” is selected, the target maximum vehicle speed can be set. In the present embodiment, switching to one state by an operation unit capable of switching to two states may be referred to as “selection” of the one.

  The A mode / B mode switching operation unit 49 is used when switching between the A mode and the B mode. The case where the A mode is selected by the A mode / B mode switching operation unit 49 indicates that the setting of the target maximum rotation speed and the target maximum vehicle speed associated with the A mode can be changed, and The control unit 40 is in a state in which the rotational speed and the vehicle speed of the engine 6 can be controlled by the target maximum rotational speed and the target maximum vehicle speed associated with the A mode. On the other hand, the case where the B mode is selected by the A mode / B mode switching operation unit 49 indicates that the setting of the target maximum rotation speed and the target maximum vehicle speed associated with the B mode can be changed. Moreover, it shows that the control part 40 is in the state which can control the rotational speed and vehicle speed of the engine 6 with the target maximum rotational speed and target maximum vehicle speed matched with B mode.

  For example, when setting the target maximum rotation speed associated with the A mode, the driver operates the A mode / B mode switching operation unit 49 to select the A mode, and further performs the rotation speed / vehicle speed switching operation. It is possible to set the target maximum rotation speed associated with the A mode by operating the unit 48 and selecting “engine rotation speed” and further operating the dial of the maximum setting operation section 47. When setting the target maximum rotation speed associated with the B mode, the only difference is that the B mode is selected by operating the A mode / B mode switching operation section 49. By performing the operation, the target maximum rotation speed associated with the B mode can be set.

  When the target maximum vehicle speed associated with the A mode is set, the driver operates the A mode / B mode switching operation unit 49 to select the A mode, and further performs the rotation speed / vehicle speed switching operation. It is possible to set the target maximum vehicle speed associated with the A mode by operating the unit 48 to select “vehicle speed” and further operating the dial of the maximum setting operation unit 47. When the target maximum vehicle speed associated with the B mode is set, the only difference is that the B mode is selected by operating the A mode / B mode switching operation unit 49. By performing this, the target maximum vehicle speed associated with the B mode can be set.

  The target maximum rotation speed and the target maximum vehicle speed in each mode of the A mode and the B mode can be set to different rotation speeds and vehicle speeds. Hereinafter, the target maximum rotation speed in the A mode is set to a first rotation speed larger than the target rotation speed, and the target maximum rotation speed in the B mode is larger than the target rotation speed and smaller than the first rotation speed. A case where the speed is set will be described as an example. Further, the case where the first vehicle speed is set as the target maximum vehicle speed in the A mode and the second vehicle speed slower than the first vehicle speed is set in the B mode will be described as an example.

  The rotational speed control mode selection operation unit 50 is used when switching between the first rotational speed control mode and the second rotational speed control mode. The first rotation speed control mode is a mode in which the control unit 40 controls the rotation speed and the vehicle speed of the engine 6 according to the mode selected by the A mode / B mode switching operation unit 49. Therefore, the control unit 40 controls the rotational speed of the engine 6 in the range from the target rotational speed to the target maximum rotational speed (first rotational speed or second rotational speed) according to the operation on the accelerator pedal 41, and the vehicle speed. Is controlled in a range from the current vehicle speed to the target maximum vehicle speed (first vehicle speed or second vehicle speed). On the other hand, the second rotation speed control mode is a mode in which the control unit 40 controls the rotation speed of the engine 6 regardless of the mode selected by the A mode / B mode switching operation unit 49. When the second rotation speed control mode is selected, the control unit 40 changes the rotation speed of the engine 6 from the target rotation speed to a predetermined rotation speed exceeding the target maximum rotation speed in accordance with an operation on the accelerator pedal 41. Control. The vehicle speed control when the second rotation speed control mode is selected will be described later.

  As the predetermined rotation speed, for example, an arbitrary rotation speed exceeding the target maximum rotation speed (the first rotation speed or the second rotation speed) can be set, such as the maximum rotation speed of the engine 6. Yes. Therefore, in this embodiment, the magnitude relationship between the rotational speeds is set so as to increase in the order of the target rotational speed, the second rotational speed, the first rotational speed, and the predetermined rotational speed.

Hereinafter, control of the rotational speed of the engine 6 by the control unit 40 will be described with reference to FIG.
The control unit 40 is configured to control the rotational speed of the engine 6 in accordance with an operation on the accelerator lever 42 and to control the rotational speed of the engine 6 in accordance with an operation on the accelerator pedal 41.

  When the A mode is selected by the A mode / B mode switching operation unit 49 and the first rotation speed control mode is selected by the rotation speed control mode selection operation unit 50, the control unit 40 controls the accelerator pedal 41. In accordance with the operation, the rotational speed of the engine 6 is controlled within a range H1 from the target rotational speed to the first rotational speed.

  When the A mode is selected by the A mode / B mode switching operation unit 49 and the second rotation speed control mode is selected by the rotation speed control mode selection operation unit 50, the control unit 40 controls the accelerator pedal 41. In accordance with the operation, the rotational speed of the engine 6 is controlled in a range H2 from the target rotational speed to a predetermined rotational speed exceeding the first rotational speed.

  When the B mode is selected by the A mode / B mode switching operation unit 49 and the first rotation speed control mode is selected by the rotation speed control mode selection operation unit 50, the control unit 40 controls the accelerator pedal 41. In accordance with the operation, the rotational speed of the engine 6 is controlled within a range H3 from the target rotational speed to the second rotational speed.

  When the B mode is selected by the A mode / B mode switching operation unit 49 and the second rotation speed control mode is selected by the rotation speed control mode selection operation unit 50, the control unit 40 controls the accelerator pedal 41. In accordance with the operation, the rotational speed of the engine 6 is controlled in a range H4 from the target rotational speed to a predetermined rotational speed exceeding the second rotational speed.

  The control unit 40 controls the rotational speed of the engine 6 in the first rotational speed control mode in both the A mode and the B mode, so that the target rotational speed is changed from the target rotational speed in accordance with the operation on the accelerator pedal 41. The rotational speed of the engine 6 can be controlled within a range up to (the first rotational speed or the second rotational speed). Thereby, even if the accelerator pedal 41 is largely depressed due to a driver's erroneous operation or the like, the rotational speed of the engine 6 does not exceed the target maximum rotational speed (first rotational speed or second rotational speed), and the engine 6 It is possible to prevent the rotational speed of the battery from being unexpectedly increased.

  In addition, the control unit 40 controls the rotational speed of the engine 6 in the second rotational speed control mode in both the A mode and the B mode, so that the target maximum rotational speed (first The rotational speed of the engine 6 can be increased to a range up to a predetermined rotational speed exceeding the rotational speed of 1 or the second rotational speed. Therefore, for example, when the lifting / lowering speed of the work implement 60 is slow and the work implement 60 cannot be operated in a desired operation state or when an engine stall occurs due to an increase in engine load or the like, the driver depresses the accelerator pedal 41 greatly. Thus, the rotational speed of the engine 6 can be increased to a range up to a predetermined rotational speed exceeding the target maximum rotational speed (the first rotational speed or the second rotational speed), and the work implement 60 can be operated in a desired operating state. It can be operated with or can avoid the engine stall.

  Regarding the control of the rotational speed of the engine 6 by the control unit 40, the case where either the A mode or the B mode is selected by the A mode / B mode switching operation unit 49 has been described. Switching is also possible when not selected. When neither the A mode nor the B mode is selected, the control unit 40 controls the governor device 31 so that the rotational speed of the engine 6 is set to the target rotational speed set by the accelerator lever 42 according to the operation on the accelerator lever 42. And the rotational speed of the engine 6 is controlled in a range from the target rotational speed to the maximum rotational speed of the engine 6 in accordance with the operation on the accelerator pedal 41.

  Next, the control of the vehicle speed of the vehicle body 2 by the control unit 40 will be described. As described above, regarding the vehicle speed control when the first rotation speed control mode is selected, the control unit 40 sets the vehicle speed to the current speed. Control is performed in a range from the vehicle speed to the target maximum vehicle speed (first vehicle speed or second vehicle speed). Therefore, the following description is added regarding the vehicle speed control when the second rotation speed control mode is selected.

  The control unit 40 controls the vehicle speed of the vehicle body unit 2 by selecting one of the first vehicle speed control mode and the second vehicle speed control mode. For example, when the speed change state of the subtransmission 25 is the low speed state, the control unit 40 selects the first vehicle speed control mode to control the vehicle speed of the vehicle body 2, and the speed change state of the subtransmission 25 is the high speed state. Sometimes, the control unit 40 selects the second vehicle speed control mode to control the vehicle speed of the vehicle body unit 2. Here, as to which of the first vehicle speed control mode and the second vehicle speed control mode is to be selected, for example, switching operation of the manually operated vehicle speed control mode is performed instead of the shift state of the auxiliary transmission 25. It can be changed as appropriate, for example, with a section.

  When the control unit 40 selects the first vehicle speed control mode, if the rotational speed of the engine 6 is a predetermined rotational speed, the control unit 40 switches the main transmission 23 so that the vehicle speed of the vehicle body unit 2 becomes a vehicle speed corresponding to the target rotational speed. Control. That is, the control unit 40 controls the main transmission 23 so that the vehicle speed of the vehicle body unit 2 becomes the vehicle speed corresponding to the target rotation speed regardless of the rotation speed of the engine 6. As a result, in the first vehicle speed control mode, even if the rotational speed of the engine 6 increases in the second rotational speed control mode, the vehicle speed of the vehicle body portion 2 is maintained at a constant vehicle speed corresponding to the target rotational speed.

  When the control unit 40 selects the second vehicle speed control mode, when the rotational speed of the engine 6 is a predetermined rotational speed, the main transmission 23 is set so that the vehicle speed of the vehicle body unit 2 becomes the vehicle speed corresponding to the target maximum rotational speed. To control. That is, when the rotational speed of the engine 6 is less than the target maximum rotational speed, the control unit 40 controls the main transmission 23 so that the vehicle speed is set according to the rotational speed of the engine 6 at that time. Then, when the rotational speed of the engine 6 becomes equal to or higher than the target maximum rotational speed, the control unit 40 has a vehicle speed corresponding to the target maximum rotational speed (for example, the first vehicle speed or the second vehicle speed that is the target maximum vehicle speed). The main transmission 23 is controlled. Thereby, when the rotational speed of the engine 6 is less than the target maximum rotational speed, a vehicle speed corresponding to the rotational speed of the engine 6 at that time is obtained, and the rotational speed of the engine 6 is set to the target by the second rotational speed control mode. When the maximum rotational speed is exceeded, the vehicle is maintained at a constant vehicle speed corresponding to the target maximum rotational speed (for example, the first vehicle speed or the second vehicle speed that is the target maximum vehicle speed).

[Another embodiment]
(1) In the above embodiment, both the A mode in which the target maximum rotation speed is set to the first rotation speed and the B mode in which the target maximum rotation speed is set to the second rotation speed can be executed. Only one of the A mode and the B mode can be executed.

(2) In the above embodiment, when the control unit 40 selects the second vehicle speed control mode and controls the vehicle speed of the vehicle body unit 2, when the rotational speed of the engine 6 is equal to or higher than the target maximum rotational speed, the target maximum rotational speed is obtained. The main transmission 23 is controlled so as to achieve a vehicle speed corresponding to the vehicle speed (for example, the first vehicle speed or the second vehicle speed that is the target maximum vehicle speed). For example, the vehicle speed according to the rotational speed of the engine 6 at that time It is also possible to control the main transmission 23 so that In this case, the vehicle speed of the vehicle body portion 2 increases as the rotational speed of the engine 6 increases.

(3) In the above-described embodiment, an example in which a continuously variable transmission is provided as the main transmission 23 has been shown. However, a gear-type transmission capable of shifting to a plurality of stages can be provided, and various transmissions can be applied. Is possible. Also, the auxiliary transmission 25 is not limited to a gear type, and various transmissions can be applied.

1 Tractor 2 Car body part 3 Front wheel (traveling part)
4 Rear wheels (travel section)
5 Bonnet 6 Engine (drive source)
21 Mission (Power transmission part)
40 Control part 41 Accelerator pedal (operation tool)
42 Accelerator lever (first setting part)
47 Maximum setting operation section (second setting section)
48 Rotational speed / vehicle speed switching operation section 49 A mode / B mode switching operation section

Claims (3)

A drive source provided in the vehicle body, a first setting unit that sets a target rotation speed of the drive source, a second setting unit that sets a target maximum rotation speed of the drive source, and driving according to an operation on the operation tool A control unit for controlling the rotational speed of the source,
The control unit is configured to control a rotation speed of the driving source in a range from the target rotation speed to the target maximum rotation speed in response to an operation on the operation tool, and to the operation tool. The rotational speed of the drive source is controlled by one of the second rotational speed control modes in which the rotational speed of the drive source is controlled in a range from the target rotational speed to a predetermined rotational speed exceeding the target maximum rotational speed according to an operation. A work vehicle characterized by controlling. A power transmission unit that transmits power of the drive source to a traveling unit provided in the vehicle body unit;
The control section controls the power transmission section so that the vehicle speed of the vehicle body section becomes a vehicle speed corresponding to the target rotation speed when the rotation speed of the drive source is the predetermined rotation speed. And a second vehicle speed control mode for controlling the power transmission unit so that the vehicle speed of the vehicle body becomes a vehicle speed corresponding to the target maximum rotation speed when the rotation speed of the drive source is the predetermined rotation speed. The work vehicle according to claim 1, wherein the vehicle speed of the vehicle body portion is controlled by any one of them. The second setting unit sets the target maximum rotation speed to a first rotation speed smaller than the predetermined rotation speed, and a second rotation smaller than the predetermined rotation speed and smaller than the first rotation speed. Can be set to one of the speeds,
When the control unit controls the rotation speed of the driving source in the second rotation speed control mode, the second setting unit sets the target maximum rotation speed to the first rotation speed and the second rotation speed. The rotation speed of the drive source is controlled in a range from the target rotation speed to the predetermined rotation speed in accordance with an operation on the operation tool. The work vehicle described.

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