JP2010185484A - Shift controller for working vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a sense of incongruity of brake operation in a reverse directional travel state. <P>SOLUTION: This shift controller for a working vehicle includes a forward and rearward movement commanding means 9 for commanding forward and rearward movements of the vehicle, travel driving means 1-6 for transmitting the rotation of a prime mover 1 to wheels 6 via a torque converter 2 and a transmission 3, and for generating a travel driving force F2 in a direction commanded by the forward and rearward movement commanding means 9, in response to a control input of an acceleration pedal 7a, automatic shifting means 3a, 8, 10a-10c for conducting shift-up and shift-down in response to a speed ratio e of an input shaft to an output shaft of the torque converter 2 or a vehicle speed v, determination means 8, 9, 10c for determining the presence of the reverse directional travel state of vehicle travel reverse-directional to the direction commanded by the forward and rearward movement commanding means 9, deceleration means 1-6, 12a for imparting a deceleration force by an operation of an operator in the reverse travel, and a shift-up prohibiting means 8 for prohibiting the shift-up by the automatic shifting means, when the reverse directional travel state is determined by the determination means 8, 9, 10c. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a shift control device for a work vehicle such as a torque loader driven wheel loader.

  2. Description of the Related Art An apparatus is known in which engine output torque is transmitted to a transmission via a torque converter (hereinafter referred to as torque converter) to generate a driving force for driving (see, for example, Patent Document 1). In the apparatus described in Patent Document 1, forward / reverse travel of the vehicle is selected by a forward / reverse switching switch, and the transmission is switched in accordance with this selection, so that the vehicle travels forward or backward.

JP 2008-138700 A

  By the way, in such a work vehicle, when the forward drive is selected by the forward / reverse switching switch and the vehicle is traveling uphill, if the accelerator pedal is operated to return, the driving force decreases and the vehicle runs backward due to its own weight. There is. During reverse running, the driving force in the forward direction acts as a braking force, so that the braking force can be adjusted without operating the brake pedal by adjusting the depression amount of the accelerator pedal.

  However, during reverse running, for example, if the transmission automatically shifts up due to an increase in the vehicle speed, the forward driving force due to the accelerator pedal operation decreases, and the brake operability due to depression of the accelerator pedal becomes uncomfortable. .

  The shift control device for a work vehicle according to the present invention transmits a forward / reverse command means for commanding forward / reverse travel of the vehicle, and transmits the rotation of the prime mover to the wheels via a torque converter (torque converter) and a transmission, depending on the operation amount of the accelerator pedal. Travel drive means for generating travel drive force in the direction commanded by the forward / reverse command means, automatic transmission means for shifting up and down according to the speed ratio of the input shaft to the output shaft of the torque converter or the vehicle speed, and forward / backward travel A determination unit that determines whether or not the vehicle is traveling in the reverse direction to the direction commanded by the command unit; a deceleration unit that can apply a deceleration force by an operator's operation during reverse travel; and a determination unit A shift-up prohibiting unit that prohibits the upshifting by the automatic transmission unit when determined to be in the reverse running state.

  According to the present invention, since upshifting by automatic shifting is prohibited during reverse running, it is possible to prevent the brake operability from feeling uncomfortable.

The side view of the wheel loader concerning an embodiment of the invention. The figure which shows schematic structure of the speed-change control apparatus which concerns on embodiment of this invention. The figure which shows the relationship between the operation amount of an accelerator pedal, and a target engine rotational speed. FIG. 6 is a diagram illustrating a scooping operation. The figure for demonstrating reverse running of a vehicle. The figure which shows the relationship between a vehicle speed and driving force. (A) is a figure which shows the automatic transmission characteristic by torque converter speed ratio reference | standard, (b) is a figure which shows the automatic transmission characteristic by vehicle speed reference | standard. The flowchart which shows an example of the process in the controller which concerns on this Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
FIG. 1 is a side view of a wheel loader that is an example of a work vehicle to which the prime mover control device according to the present embodiment is applied. The wheel loader 100 includes a front vehicle body 110 having an arm 111, a bucket 112, a tire 113, and the like, and a rear vehicle body 120 having an operator cab 121, an engine compartment 122, a tire 123, and the like. The arm 111 rotates up and down (up and down) by driving the arm cylinder 114, and the bucket 112 rotates up and down (dump or cloud) by driving the bucket cylinder 115. The front vehicle body 110 and the rear vehicle body 120 are rotatably connected to each other by a center pin 101, and the front vehicle body 110 is refracted left and right with respect to the rear vehicle body 120 by expansion and contraction of a steering cylinder (not shown).

  FIG. 2 is a diagram showing a schematic configuration of the prime mover control device according to the present embodiment. An output shaft of the engine 1 is connected to an input shaft of a torque converter 2 (hereinafter referred to as torque converter), and an output shaft of the torque converter 2 is connected to a transmission 3 capable of shifting from 1st to 4th speed. The torque converter 2 is a fluid clutch including a known impeller, turbine, and stator, and the rotation of the engine 1 is transmitted to the transmission 3 via the torque converter 2. The transmission 3 has a hydraulic clutch that shifts its speed stage, and the rotation of the output shaft of the torque converter 2 is changed by the transmission 3. The rotation after the shift is transmitted to the tire 6 (113 and 123 in FIG. 1) via the propeller shaft 4 and the axle 5, and the vehicle travels.

  Although not shown in the figure, the wheel loader is provided with a working hydraulic pump driven by the engine 1, and pressure oil from the hydraulic pump is supplied to actuators such as the arm cylinder 114 and the bucket cylinder 115 to perform the work. Done.

  The controller 8 includes an arithmetic processing unit having a CPU, ROM, RAM, and other peripheral circuits. The controller 8 includes an accelerator operation amount detector 7 for detecting the operation amount of the accelerator pedal 7a, a forward / reverse selector switch 9 for instructing forward / reverse travel of the vehicle, and a rotational speed for detecting the rotational speed Ni of the input shaft of the torque converter 2. A detector 10a, a rotational speed detector 10b for detecting the rotational speed Nt of the output shaft of the torque converter 2, a rotational speed detector 10c for detecting the rotational speed of the output shaft of the transmission 3, that is, the vehicle speed v, and first to fourth speeds. A maximum speed stage selection switch 11 for instructing an upper limit of the speed stage between speeds and a brake operation amount detector 12a for detecting an operation amount of the brake pedal 12a are connected. The rotational speed detector 10c can detect not only the rotational speed but also the rotational direction (vehicle traveling direction). Note that the rotation direction may be detected by the rotation speed detector 10b.

  The controller 8 outputs a control signal to the engine control unit 1a, and controls the engine rotation speed to the target engine rotation speed Na corresponding to the operation amount of the accelerator pedal 7a. FIG. 3 is a diagram showing the relationship between the pedal operation amount and the target engine rotation speed Na. As shown in FIG. 3, when the accelerator pedal 7a is not operated, the target engine speed Na is the minimum value Nmin, and the target engine speed Na increases as the pedal operation amount increases. The target engine speed Na when the pedal is fully depressed is the maximum value Nmax.

  The torque converter 2 has a function of increasing the output torque Tout with respect to the input torque Tin, that is, a function of setting the torque ratio Tr (= Tout / Tin) to 1 or more. The torque ratio Tr changes according to a torque converter speed ratio e (output rotational speed Nt / input rotational speed Ni) which is a ratio of the rotational speed of the input shaft and the output shaft of the torque converter 2. The torque converter speed ratio e is a positive value when the rotational directions of the input shaft and the output shaft of the torque converter 2 are the same, and is a negative value when the rotational directions of the input shaft and the output shaft are different, that is, in the reverse running state. .

  The reverse running state in which the torque converter speed ratio e is e <0 occurs when running on a slope as shown in FIG. Hereinafter, this point will be described. FIG. 4 is a view showing a so-called scooping operation in which earth and sand in the bucket are piled up in a mountain shape by the wheel loader. When performing the lifting work, the operator switches the forward / reverse selector switch 9 to the forward position, and depresses the accelerator pedal 7a half to full. As a result, traveling driving force in the forward direction is generated, and the vehicle rises steeply. Thereafter, when the load in the bucket is released, the operator returns the accelerator pedal 7a to reduce the traveling driving force in the forward direction.

  Here, as shown in FIG. 5, the weight of the vehicle is W, the slope of the slope is θ, and the force that tries to descend the slope by its own weight (the force that turns the tire 6) is F. Furthermore, the rolling radius of the tire 6 is R, and the rolling resistance of the tire 6 is μ. At this time, a force F1 is applied to the vehicle to lower the slope due to its own weight, and F1 = W × (sin θ−μ × cos θ). Therefore, when the force F1 exceeds the forward driving force F2 by the operation of the accelerator pedal 7a, the vehicle runs backward and goes down the slope.

  The driving force F2 by the operation of the accelerator pedal 7a changes according to the vehicle speed v and the speed stage. FIG. 6 is a diagram showing the relationship between the vehicle speed v and the driving force F2 at each speed stage when the accelerator pedal 7a is depressed to the maximum, for example. The driving force F2 increases as the speed stage decreases and the vehicle speed v decreases.

  The transmission 3 is an automatic transmission having solenoid valves corresponding to the first to fourth speed stages. These solenoid valves are driven by a control signal output from the controller 8 to the transmission control unit 3a, whereby the speed stage of the transmission 3 is changed.

  FIG. 7 is a diagram showing the timing of automatic shift in the transmission 3. The automatic transmission control includes torque converter speed ratio reference control that shifts when the torque converter speed ratio e reaches a predetermined value as shown in FIG. 7A, and vehicle speed v reaches a predetermined value as shown in FIG. 7B. Then, there are two methods of vehicle speed reference control for shifting.

  In the torque converter speed ratio reference control shown in FIG. 7A, when the traveling load decreases and the torque converter speed ratio e increases and the torque converter speed ratio e becomes equal to or greater than a predetermined value e2, the speed stage is shifted up by one stage. On the other hand, when the traveling load increases and the torque converter speed ratio e decreases and the torque converter speed ratio e becomes equal to or less than a predetermined value e1, the speed stage is shifted down by one stage. During reverse running, the torque converter speed ratio e is negative. In this case, when the absolute value of the torque converter speed ratio e exceeds a predetermined value e2, the speed stage is shifted up by one stage, and when the absolute value of the torque converter speed ratio e becomes equal to or less than the predetermined value e1, the speed stage becomes one stage. Shift down. Even during reverse running, a shift up or down shift is similarly performed according to the torque converter speed ratio e.

  As a result, the speed stage of the transmission 3 is automatically changed between the first speed to the fourth speed according to the torque converter speed ratio e. At this time, automatic transmission is automatically performed with the speed stage selected by the maximum speed stage selection switch 11 as an upper limit. For example, when the second speed is selected by the maximum speed stage selection switch 11, the speed stage is the first speed or the second speed, and when the first speed is selected, the speed stage is fixed to the first speed.

  On the other hand, in the vehicle speed reference control shown in FIG. 7B, when the vehicle speed v increases and reaches the predetermined values vS1, vS2, and vS3, the speed stage is shifted up by one stage, and the vehicle speed v decreases and the predetermined value vS4. When vS5 and vS6 are reached, the speed stage is shifted down by one stage. In reverse running, the vehicle is similarly shifted up or down according to the vehicle speed v. Below, it demonstrates as what controls the speed stage of the transmission 3 by vehicle speed control. Note that the speed stage of the transmission 3 may be controlled not by vehicle speed control but by torque converter speed ratio reference control.

  In the present embodiment, when the accelerator pedal 7a is depressed during reverse running of the vehicle as shown in FIG. 4, the engine speed increases and the driving force F2 in the forward direction increases. As a result, the braking force against the force F1 descending the hill due to its own weight increases, and the vehicle speed during reverse running can be adjusted without operating the brake pedal 12a.

  During reverse running, when the vehicle speed v increases and exceeds the predetermined values vS1, vS2, and vS3 in FIG. 7B, the speed stage is automatically shifted up. As a result, the driving force F2 due to the operation of the accelerator pedal 7a, that is, the braking force during reverse running, decreases, and the operator feels uncomfortable with the brake operability. In order to prevent this, the speed change is controlled as follows in the present embodiment.

  FIG. 8 is a flowchart illustrating an example of processing executed by the CPU of the controller 8. The process shown in this flowchart is started, for example, when an engine key switch is turned on. Note that threshold values vS1 to vS6 serving as references for upshifting and downshifting are stored in advance in the memory.

  In step S1, signals from the various sensors 7, 10a to 10c, 12 and the switches 9, 11 in FIG. In step S2, it is determined whether or not the vehicle speed v detected by the rotational speed detector 10c has reached thresholds vS1, vS2, and vS3 (shift-up vehicle speeds) determined in advance corresponding to each speed stage. That is, in the case of the first speed stage, it is determined whether or not the vehicle speed v has reached the predetermined value vS1, and in the case of the second speed stage, it is determined whether or not the vehicle speed v has reached the predetermined value vS2. In this case, it is determined whether or not the vehicle speed v has reached a predetermined value vS3. If step S2 is positive, the process proceeds to step S3. In step S3, it is determined whether or not the current speed stage is at the maximum speed stage commanded by the maximum speed stage selection switch 11. If step S3 is affirmed, the process returns. If not, the process proceeds to step S4.

  In step S4, based on the signals from the forward / reverse selector switch 9 and the rotational speed detector 10c, whether the vehicle is in the reverse traveling state, that is, the vehicle traveling direction commanded by the forward / reverse selector switch 9 and the rotational speed detector 10c is detected. It is determined whether or not the vehicle traveling directions are different. If step S4 is affirmed, the process returns. If not, the process proceeds to step S5. In step S5, a control signal is output to the transmission control unit 3a, and the speed stage is shifted up by one stage.

  On the other hand, if step S2 is negative, the process proceeds to step S6. In step S6, it is determined whether or not the vehicle speed v detected by the rotational speed detector 10c has reached thresholds vS4, vS5, and vS6 (shift down vehicle speeds) determined in advance corresponding to each speed stage. That is, in the case of the second speed stage, it is determined whether or not the vehicle speed v has reached the predetermined value vS4. In the case of the third speed stage, it is determined whether or not the vehicle speed v has reached the predetermined value vS5. In this case, it is determined whether or not the vehicle speed v has reached a predetermined value vS6. If step S6 is positive, the process proceeds to step S7, and if step S6 is negative, the process returns. In step S7, a control signal is output to the transmission control unit 3a, and the speed stage is shifted down by one stage.

  The main operation of this embodiment will be described. When the vehicle speed v increases and reaches upshift vehicle speeds vS1, vS2, and vS3 during non-reverse running, the speed stage of the transmission 3 is shifted up with the speed stage commanded by the maximum speed stage selection switch 11 as the upper limit ( Step S4 → Step S5). On the other hand, even if the vehicle speed v increases during reverse running and reaches the upshift vehicle speeds vS1, vS2, and vS3, the speed stage of the transmission 3 is not shifted up and the current speed stage is maintained. As a result, it is possible to prevent the driving force F2 due to the operation of the accelerator pedal 7a, that is, the braking force from being reduced during reverse running, and the operator does not feel uncomfortable with the brake operability, and the brake operability is improved.

According to the present embodiment, the following operational effects can be achieved.
(1) The reverse running state of the vehicle is determined based on signals from the forward / reverse selector switch 9 and the rotational speed detector 10c, and when it is determined that the vehicle is in the reverse running state, the shift up by automatic shift is prohibited. Thereby, it is possible to prevent the driving force F2 in the forward direction from being reduced by the operation of the accelerator pedal 7a, and the brake operability by the accelerator pedal 7a is improved.
(2) Since a braking force is applied to the vehicle during reverse running by generating a forward driving force F2 corresponding to the amount of operation of the accelerator pedal 7a, the braking force can be adjusted without operating the brake pedal 12a. Thus, it is possible to easily perform a hoisting operation and the like that repeats climbing traveling and downhill traveling.

  In the above embodiment, the deceleration force is applied to the vehicle during reverse running by the driving force F2 corresponding to the operation amount of the accelerator pedal 7a. However, the deceleration means is not limited to this. For example, the braking force may be applied by operating the brake pedal 12a during reverse running. In this case as well, the shift-up is prohibited, so that a decrease in the driving force F2 in the forward direction can be suppressed, and the operator can be prevented from feeling uncomfortable with the brake operability. Although the vehicle forward / reverse command is commanded by the forward / reverse switching switch 9, the configuration of the forward / reverse command means is not limited to this. When forward movement is commanded by the forward / reverse selector switch 9, the rotation of the engine 1 is transmitted to the tire 6 via the torque converter 2, and the forward driving force corresponding to the operation amount of the accelerator pedal 1 a is generated. For example, any driving means may be used.

  Although the up-shifting or down-shifting is performed according to the vehicle speed v, the up-shifting or down-shifting may be performed according to the torque converter speed ratio e, and the automatic transmission means may have any configuration. Although the controller 8 determines the reverse running state of the vehicle by the signals from the forward / reverse selector switch 9 and the rotational speed detector 10c, the determination means is not limited to this. If the upshifting is prohibited when the reverse running state is determined, the processing in the controller 8 as the upshifting prohibiting means is not limited to the above.

  In the above, an example in which the present invention is applied to a wheel loader has been described. However, the present invention can be similarly applied to other work vehicles driven by a torque converter. That is, as long as the features and functions of the present invention can be realized, the present invention is not limited to the shift control device for a work vehicle according to the embodiment.

DESCRIPTION OF SYMBOLS 1 Engine 2 Torque converter 3 Transmission 3a Transmission control part 7 Accelerator operation amount detector 8 Controller 9 Forward / reverse changeover switch 10a-10c Rotation speed detector

Claims (2)

Forward / reverse command means for commanding forward / backward movement of the vehicle;
Travel drive means for transmitting the rotation of the prime mover to the wheels via a torque converter (torque converter) and a transmission, and generating a travel drive force in the direction commanded by the forward / reverse command means according to the operation amount of the accelerator pedal;
Automatic transmission means for shifting up and down depending on the speed ratio or vehicle speed of the input shaft and output shaft of the torque converter;
Determining means for determining whether or not the vehicle is running in the reverse direction that is the direction opposite to the direction commanded by the forward / reverse command means;
Deceleration means capable of applying a deceleration force by an operator's operation during reverse running;
A shift control apparatus for a work vehicle, comprising: a shift-up prohibiting unit that prohibits a shift-up by the automatic transmission unit when the determination unit determines that the vehicle is running in reverse. The shift control device for a work vehicle according to claim 1,
The speed reduction means applies a deceleration force during reverse running by generating a driving force in the direction commanded by the forward / reverse command means according to the amount of operation of the accelerator pedal. Control device.

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