JPH11123956A - Car speed control device for working vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reflect an operator's intention in the control by conducting the car speed control according to the newly caused change to various working environmental conditions and giving priority to manual operation of a car speed designating device when the operating position of the car speed designating device and the operating position of a continuously variable transmission mechanism substantially agree. SOLUTION: When a control on-off switch 25 for reading a setting signal of each lever or switch and a detection signal of every kind of sensor is 'on', the car speed control is executed. During the car speed control, the operating position L of a gear shift lever 21 is compared with the turning angle θ of a trunnion shaft of HST12 to judge whether or not the operating position L substantially agrees with the operating position LS corresponding to the turning angle θS of the trunnion shaft during deceleration control. If yes, the present car speed control mode is released, and the priority is given to the manual operation of the gear shift lever 21. That is, the deceleration target value θS of HST 12 is set to the turning angle θN of the trunnion shaft corresponding to the operating position LN of the present gear shift lever to conduct the control.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle speed control device for a working vehicle, and more particularly, to a vehicle speed control device for automatically controlling a vehicle speed according to a change in work environment conditions.

[0002]

2. Description of the Related Art In a relatively small work vehicle, there has been known a work vehicle in which the power of an engine is shifted by a continuously variable transmission mechanism such as a hydraulic transmission or a belt-type transmission. In this type of work vehicle, the continuously variable transmission mechanism can be changed to an arbitrary operating position by a vehicle speed specifying device such as a transmission lever, so that the vehicle speed can be continuously changed. When the engine speed decreases due to a high load during the operation, the continuously variable transmission mechanism is operated to reduce the vehicle speed in order to maintain the engine speed at the specified speed. Further, when turning at the end of the field, the work implement is raised and the continuously variable transmission mechanism is operated to reduce the vehicle speed. Alternatively, even when working on a slope, it is necessary to reduce the vehicle speed in accordance with the magnitude of the repetition frequency of the left-right inclination.

[0003]

However, under the ever-changing working environment conditions, it is important to control the vehicle speed on the basis of the conditions. In addition, there are various ways to cancel the control after the vehicle speed control is started. Conditions can be considered. It is difficult to perform all of these operations manually at the discretion of the operator.

[0004] Therefore, there arises a technical problem to be solved in order to automatically control the vehicle speed in accordance with the change of the working environment condition and to enable the control to be released by a simple operation. The purpose is to solve the problem.

[0005]

SUMMARY OF THE INVENTION The present invention has been proposed to achieve the above object, and is directed to a work vehicle equipped with a continuously variable transmission mechanism for continuously changing the vehicle speed in accordance with the operation of a vehicle speed designation device. Control means for controlling the vehicle speed by changing the operating position of the continuously variable transmission mechanism irrespective of the operation position of the vehicle speed specifying device, and responding to a change newly generated in response to various changes in work environment conditions. Vehicle speed control, and when the operation position of the vehicle speed designation device substantially coincides with the operation position of the continuously variable transmission mechanism, the automatic operation of the vehicle speed is released with priority given to the manual operation of the vehicle speed designation device. And a vehicle speed control device for a working vehicle.

[0006]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a lawn mower 10 as an example of a small work vehicle, in which an engine 11 is mounted on a front portion of the body, and the power of the engine 11 is a hydraulic transmission device (hereinafter, HST).
The speed is reduced by a continuously variable transmission mechanism such as 12) and the rear wheel 1
3 is transmitted. In addition to the HST, the continuously variable transmission mechanism may be a transmission mechanism having another configuration such as a belt-type transmission.

A mower 16 is suspended between the rear wheel 13 and the front wheel 14 via a link mechanism 15 at the lower part of the body, and a part of the engine power is transmitted from the front PTO shaft 17 to the mower 16. And actuator 1
By the operation of 8, the mower 16 can be moved up and down.

On the other hand, a throttle lever 20 is provided in the vicinity of the steering handle 19, and the rack position of an engine governor (not shown) is moved by rotating the throttle lever 20, so that the rotation speed of the engine 11 is reduced. Can be adjusted. Also, steering wheel 1
A speed change lever 21 as a vehicle speed designating device is provided at the lower side of the drive shaft 9, and by rotating the speed change lever 21, the trunnion shaft of the HST 12 rotates to change the rotation speed of the output shaft (that is, the vehicle speed). can do. Further, an elevating lever 23 is provided at the lower side of the driver's seat 22. By rotating the elevating lever 23, the elevating actuator 18 is operated, and the mower 16 is raised and lowered via the link mechanism 15.

A controller 24 is provided below the driver's seat 22. As will be described later, the controller 24 reads operation signals of various levers, detection signals of sensors, and the like as control means for controlling the vehicle speed. Outputs a control signal from the controller 24 to each actuator. Reference numeral 25 denotes a control on / off switch for selecting execution or cancellation of vehicle speed control.

FIG. 2 is a block diagram of a vehicle speed control system. Detectors such as potentiometers are attached to the throttle lever 20, shift lever 21 and lift lever 23, and the operating signals of the respective levers are detected by the respective detectors. Is sent to the controller 24. Also, the engine rotation sensor 26
, The rotation speed of the engine is detected, and the trunnion shaft angle sensor 27 detects the operating position of the HST 12 (the rotation angle of the trunnion shaft). Further, a steering angle of the front wheel 14 is detected by a steering angle sensor 28, a rolling angle of the machine body is detected by an inclination sensor 29, and a vertical position of the mower 16 is detected by a vertical sensor 30.

Based on these input signals, the controller 24 outputs a control signal to a rack actuator 31 of the engine governor by a control method described later to adjust the rotation speed of the engine 11 and outputs a control signal to the HST actuator 32. Then, the rotation angle of the trunnion shaft of the HST 12 is changed to increase or decrease the rotation speed (vehicle speed) of the output shaft. Further, a control signal is output to the lifting actuator 33, and the mower 1 is output.
6 is moved up and down.

FIG. 3 to FIG. 5 are main flowcharts of the vehicle speed control of the lawn mower 10. First, setting signals of each lever and switch and detection signals of various sensors are read (step 01). Then, when it is determined that the control ON / OFF switch 25 is ON (step 02), vehicle speed control is executed. When the deceleration control is being executed by turning on the control on / off switch (step 20), the vehicle speed control is continued when there is no condition for canceling the control, which will be described later, to prevent a rapid increase due to the cancellation of the control. .

Step 03 shows one condition for canceling the control.
The operation position L of the transmission lever 21 and the rotation angle θ of the trunnion shaft of the HST 12 are compared, and the operation position L of the transmission lever approximately matches the operation position L _S corresponding to the rotation angle θ _S of the trunnion shaft during deceleration control. It is determined whether or not. As shown in FIG. 6, in the normal operation and the rotation angle θ is changed in the trunnion-axis in proportion to the turning operation of the shift lever, for example, the rotation angle of the trunnion shaft at the operating position of the shift lever L ₁ is θ It becomes ₁ . However, as described later, when the deceleration by the vehicle speed control will be changed less only the rotation angle of the trunnion shaft to the deceleration target value theta _S by HST actuator 32, the shift lever remains in its original operating position L _1.

Now, the operator consciously operates the shift lever to release the deceleration state, and the operating position L of the shift lever is changed to the operating position L corresponding to the rotation angle θ _S of the trunnion shaft.
When the vehicle speed substantially coincides with _S , the current vehicle speed control mode is canceled (step 30). At this time, becomes a speed corresponding to the operating position L _S of the shift lever, the actual vehicle speed and the speed change operation is identical no discomfort of the operator, it can ensure safety during control release. Thereafter, giving priority to manual operation of the shift lever, and the rotation angle theta _N trunnion axis corresponding to deceleration target value theta _S of the HST to the operating position L _N of the current shift lever (Step 31).

If the operation position L of the shift lever does not coincide with the operation position L _S corresponding to the rotation angle θ _S of the trunnion shaft in step 03, it is determined whether the vehicle speed control is currently being performed in any vehicle speed control mode. (Step 04) If the vehicle speed control is being performed, the process proceeds to a subroutine for determining a vehicle speed control mode release condition (Step 05). The vehicle speed control mode is step 07
As described later, three types, an engine mode, a turning mode, and an inclination mode, are defined.

As shown in FIG. 7, in the vehicle speed control mode release condition determination subroutine, first, the current vehicle speed control mode is determined (step 051). Then, the turning mode release is set (step 053). On the other hand, if the repetition of the left-right tilt does not occur for the specified time or more in the tilt mode (step 058), the tilt mode release is set (step 059).

Here, when the current vehicle speed control mode is the engine mode, the operator operates the throttle lever 20 according to the contents of the work, and the reference rotation speed of the engine (maximum rotation speed under no load at the time of setting the work). a state with reduced N _K, i.e. if the throttle position change control in (step 054), when substantially matches the operating position L _S which operating position L of the shift lever corresponding to the rotational angle theta _S trunnion axis (Step 055), the engine mode release is set (step 056). On the other hand, when the throttle position change control is not being performed and the reference engine speed N _K is a normal high speed (for example, 2000 rpm or more), the engine speed N is about minus 100 rpm of the reference engine speed N _K. Upon returning to the above (step 057), the engine mode release is set (step 056).

As described above, the vehicle speed control mode release condition is determined in step 05 shown in FIG. 3, and if there is a release condition of the current vehicle speed control mode, the process proceeds from step 06 to step 30 and the current vehicle speed The control mode is released. On the other hand, if there is no release condition of the vehicle speed control mode in step 06, the process proceeds to a subroutine for determining a vehicle speed control mode entry condition (step 07).

As shown in FIG. 8, the subroutine for determining the vehicle speed control mode inrush conditions, firstly by the size of the reference rotation speed N _K of the engine, sets a start decision value of the vehicle speed control by engine mode (step 071). If the reference rotation speed N _K is a normal high rotational (or 2000 rpm),
The engine speed N is a start decision value when the drops below 1800 rpm, the reference rotation speed N _K is a low rotation (2000Rp
m), the decrease in the engine speed N is 200 rp.
When m (rotational speed difference) is exceeded, it is regarded as the inrush judgment value.

For example, when the engine speed N matches the judgment value (step 072), the vehicle speed control in the engine mode is set (step 073). Here, the new deceleration target operating position of the HST corresponding to the current engine speed N, that is, the rotation angle of the trunnion shaft is set to the new deceleration target value θ _SN . At the same time, the tilt mode and the turning mode are reset. Then, it is set that a new entry condition for the vehicle speed control mode has occurred (step 074).

On the other hand, at step 072, the engine speed N
Does not match the determination value, the inclination sensor 29 calculates the repetition frequency of the left-right inclination of the body (step 07).
5) If there is a large repetition of the left-right inclination (step 076), the vehicle speed control in the inclination mode is set (step 077). Here, HST at the time of inclination
_Is set, and the engine mode and the turning mode are reset. Step 074
Proceed to.

If there is no repetition of the large left-right inclination in step 076, it is determined whether or not the mower has been raised by the elevation sensor 30 (step 078).
When the mower has risen, the vehicle speed control in the turning mode is set (step 079). Here, a new deceleration target value θ _SN of the HST during turning is set, and the engine mode and the tilt mode are reset. Thereafter, the flow advances to step 074.

As described above, in step 07 shown in FIG. 3, the vehicle speed control mode entry condition is determined. Target value θ _{SO up to}
And the new deceleration target value θ _SN, and the lower one is selected as the current deceleration target value θ _S.

On the other hand, if there is no entry condition of the new vehicle speed control mode in step 07, it is determined whether or not the vehicle speed control is being performed in the engine mode (step 40). Proceed to the engine mode vehicle speed control subroutine to continue (step 4
1). If the vehicle speed is not being controlled in the engine mode but is being controlled in the turning mode (step 50), the process proceeds to a turning mode vehicle speed control subroutine (step 51) to continue this control. Further, if the vehicle speed control is not being performed in the turning mode but is being performed in the inclination mode (step 6).
0), the process proceeds to a subroutine of vehicle speed control in the inclination mode in order to continue this control (step 61).

In steps 40, 50 and 60,
If no vehicle speed control is being performed, the process proceeds to step 31,
A deceleration target value theta _S of the HST to the rotation angle theta _N current trunnion axis corresponding to the operating position L _N of the shift lever.

As shown in FIG. 9, in the engine mode vehicle speed control subroutine, first, it is determined whether or not the throttle lever 20 is operated to the deceleration side (step 40).
1) If the throttle lever is being operated to the deceleration side, the throttle position shift control is set (step 40).
2), the deceleration target value theta _S of the HST to hold the deceleration position at this time the rotation angle theta _N current trunnion axis (step 403).

Here, when the throttle lever is not being operated to the deceleration side and the throttle position change control is being performed (step 404), step 403 is performed until the throttle lever is operated to increase the speed (step 405). Then, the deceleration position at this time is held. Step 4
If the throttle lever is operated to increase the speed in step 05, the operation of increasing the speed of the throttle lever and changing the engine speed until the throttle lever returns to the original position (position where the engine speed is large) (step 406). H in response to the rise
The deceleration target value θ _S of ST is set (step 407),
When the throttle lever has reached the original position, the throttle position shift control is reset (step 409).

On the other hand, the process proceeds to step 408 if not in throttle position change control in step 404, the difference from the rotation reduction rate D between the reference rotational speed N and the current engine speed N _K of the engine (D = | ( _{N K -N) | / N K} ) is calculated, taking into account the rotation drop rate D to the rotation angle theta _N current trunnion shaft sets the deceleration target value theta _S of HST (θ _S ← θ _N × D).

As shown in FIG. 10, in the turning mode vehicle speed control subroutine, the current deceleration target value θ _S of the HST is maintained (step 501). Also, as shown in FIG. 11, the current deceleration target value θ _S of the HST is maintained in the subroutine of the inclination mode vehicle speed control (step 501).

Step 3 shown in FIG. 3 and FIG.
1, step 09, step 41, based on the deceleration target value theta _S of each set HST at step 51, step 61, in step 10 shown in FIG. 5, corresponding to the operating position L _N of the current shift lever Then, the difference between the rotation angle θ _N of the trunnion shaft and the deceleration target value θ _{S of the} HST is compared and the difference is determined. The acceleration output is turned on (step 11), and when a deceleration request is made for the current HST operation position, the deceleration output is turned on for the HST actuator (step 13). Also, the current H
Is to increase or decrease the output off when ST operating position coincides with the deceleration target value theta _S (step 12).

The present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.

[0032]

As described above, according to the present invention, when controlling the vehicle speed of a working vehicle in accordance with changes in various working environment conditions, the vehicle speed is controlled in accordance with a newly generated change, whereby the vehicle is controlled every moment. Automatic control suitable for changing work environment can be performed. Further, when the operation position of the vehicle speed designation device substantially coincides with the operation position of the continuously variable transmission mechanism, the automatic control of the vehicle speed is released, so that the intention of the operator to release the deceleration state can be reflected. Control can be reliably released.

Thus, the execution and release of the vehicle speed control can be smoothly performed.

[Brief description of the drawings]

 The figure shows an embodiment of the present invention.

FIG. 1 is a side view showing a lawn mower as an example of a small work vehicle.

FIG. 2 is a block diagram of a vehicle speed control system.

FIG. 3 is a main flowchart of vehicle speed control, part 1;

FIG. 4 is a main flowchart of vehicle speed control, part 2;

FIG. 5 is a main flowchart of vehicle speed control, part 3;

FIG. 6 is a graph showing a relationship between an operation position of a shift lever and a rotation angle of a trunnion shaft of the HST.

FIG. 7 is a flowchart of a subroutine for determining a vehicle speed control mode release condition.

FIG. 8 is a flowchart of a subroutine for determining a vehicle speed control mode entry condition.

FIG. 9 is a flowchart of a subroutine of engine mode vehicle speed control.

FIG. 10 is a flowchart of a subroutine for turning mode vehicle speed control.

FIG. 11 is a flowchart of a subroutine of a guard mode vehicle speed control.

[Explanation of symbols]

 Reference Signs List 10 Lawn mower 11 Engine 12 Hydraulic transmission (HST) 20 Throttle lever 21 Shift lever 24 Controller 25 Control on / off switch

Continued on the front page (51) Int.Cl. ⁶ Identification code FI // F16H 59:44

Claims (1)

[Claims] In a work vehicle equipped with a continuously variable transmission mechanism for continuously changing a vehicle speed in accordance with an operation of a vehicle speed specification device, an operation position of the continuously variable transmission mechanism is changed regardless of an operation position of the vehicle speed specification device. A control means for performing vehicle speed control by changing the vehicle speed is provided to perform vehicle speed control according to a newly generated change in response to changes in various working environment conditions, and to operate the operation position of the vehicle speed designation device and the operation of the continuously variable transmission mechanism. A vehicle speed control device for a working vehicle, wherein the automatic control of the vehicle speed is canceled by giving priority to the manual operation of the vehicle speed designation device when the position substantially coincides.