JP4376018B2 - Control device for work vehicle - Google Patents

Description

  The present invention relates to a control device for a work vehicle such as a wheel loader or a telescopic handler that drives a transmission by an engine and travels, drives a hydraulic pump by the engine, and operates a work actuator to perform a predetermined work.

  Japanese Patent Publication No. 8-6613 and Japanese Patent No. 2968558 disclose conventional techniques for control devices in this type of work vehicle.

  The prior art described in Japanese Examined Patent Publication No. 8-6613 prepares two types of engine output characteristics, an engine output characteristic suitable for working and an engine output characteristic suitable for traveling, depending on whether the working state or the traveling state. When the engine output characteristics are switched and the engine output is controlled, the fuel injection amount is controlled so that the transmission torque does not exceed the torque in the working state when the engine is running and the torque converter speed ratio is low (low speed) Thus, the excessive torque applied to the torque converter is prevented from being generated.

  In the prior art described in Japanese Patent No. 2968558, when the sum of the load of the travel drive device and the actuator is smaller than the output torque of the engine, the pump absorption torque is increased to ensure the work amount, and the sum of the load is the engine output. When the torque is larger than the torque, the pump absorption torque is decreased to ensure a large traveling torque and maintain a large traction force.

Japanese Patent Publication No. 8-6613

Japanese Patent No. 2968558

  When combined with traveling and front work equipment on a work vehicle such as a wheel loader or telescopic handler, the sum of the hydraulic pump absorption torque and transmission torque (traveling torque) may exceed the engine output torque. In many such operating conditions, the engine output torque is used in preference to the hydraulic pump, and the rest is used for traveling.

  By the way, work vehicles such as wheel loaders and telescopic handlers have speed switching means for switching the transmission reduction ratio (gear ratio) from low to high, and the operator performs work by switching the reduction ratio according to the work contents. . For example, in excavation work of earth and sand such as natural ground, the excavator is pressed against the earth and sand by running force, so the operator switches the transmission to a low speed, reduces the speed ratio of the torque converter, and increases the running torque. In this case, it is desirable that the running torque is as large as possible. On the other hand, when carrying the excavated earth and sand to the destination, the transmission is switched to high speed so that it can run at high speed. In this case, it is preferable not to require a very large running torque, but rather to increase the engine output torque to the hydraulic pump so that the front device can be moved quickly.

  The prior art described in Japanese Patent Publication No. 8-6613 and Japanese Patent No. 2968558 does not change the distribution of the pump absorption torque and the running torque according to the transmission reduction ratio, and is optimal for the reduction ratio. The driving force and front speed could not be obtained.

  The object of the present invention is to change the distribution of the pump absorption torque and the running torque depending on whether the transmission reduction ratio is high speed or low speed, thereby obtaining the optimum pump absorption torque and running torque matching according to the reduction ratio. It is providing the control apparatus of a work vehicle.

(1) In order to achieve the above object, the present invention provides an engine, a fuel injection device for controlling the output torque and the rotational speed of the engine , a variable displacement hydraulic pump driven by the engine, A hydraulic actuator driven by discharged oil, first pump torque control means for controlling the absorption torque of the hydraulic pump not to exceed a maximum absorption torque, and a torque converter driven by the engine , When the maximum absorption torque is consumed, a traveling transmission to which a traveling engine output torque that is lower than the engine output torque by the maximum absorption torque of the hydraulic pump is distributed, and a reduction ratio of the transmission a speed switching instruction means for instructing the fast and slow switching, by pre-Symbol rate switching instruction means The said one select the at least first and second two pump absorption torque characteristic preset according to the reduction ratio of the transmission shown, controlling the maximum absorption torque of said hydraulic pump based on the pump absorption torque 2 pump torque control means , wherein the second pump torque control means has a maximum absorption torque of the hydraulic pump based on the first pump absorption torque characteristic when the transmission gear ratio is high. When the first pump torque control means is controlled so as to be 1 maximum absorption torque, and the transmission gear ratio is low, the maximum absorption torque of the hydraulic pump is determined based on the second pump absorption torque characteristic. The second maximum absorption torque is smaller than the maximum absorption torque, and the maximum absorption torque of the hydraulic pump and the traveling The first point is such that the matching point with the transmission torque, which is the input torque of the transmission, is maintained on the higher engine speed side than when the maximum absorption torque of the hydraulic pump becomes the first maximum absorption torque. It is assumed that the pump torque control means is controlled .

In this way, the second pump torque control means is provided, and the pump absorption torque characteristic is selected according to the transmission reduction ratio and the maximum absorption torque of the hydraulic pump is controlled, so that the pump absorption depends on whether the transmission reduction ratio is high or low. The distribution of the torque and the running torque changes, and the optimum pump absorption torque and running torque matching according to the reduction ratio can be obtained.
In addition, when the reduction ratio is set to a low speed, the maximum absorption torque of the hydraulic pump is small, so the engine output torque distributed to traveling increases, and the excavator can be pushed with a large traveling force during excavation work, etc. Will improve. In addition, the matching point between the maximum pump absorption torque and transmission torque when the reduction ratio is reduced is kept on the high engine speed side, so that the fuel efficiency of the engine can be improved and the engine speed can be reduced. Therefore, operator fatigue can be reduced. On the other hand, when the speed reduction ratio is increased, the maximum absorption torque of the hydraulic pump is large. Therefore, when carrying the excavated earth and sand to the destination, the front can be moved quickly, and the working efficiency is improved.

  According to the present invention, the optimal pump absorption torque and running torque matching according to the reduction ratio can be obtained by changing the distribution of the pump absorption torque and the running torque depending on whether the reduction ratio of the transmission is high speed or low speed. It is possible to perform efficient work while effectively using the engine output horsepower.

  In addition, since the matching point M at the time of low speed is maintained on the high speed side as compared with the conventional case, the fuel consumption of the engine 1 can be improved. Furthermore, since the decrease in engine speed is small, operator fatigue can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a system configuration diagram of an entire drive apparatus including a work vehicle control apparatus according to an embodiment of the present invention.

  In FIG. 1, a work vehicle according to the present embodiment includes a diesel engine (hereinafter simply referred to as an engine) 1 as a prime mover, and an engine 1 is provided with an electronic fuel injection device 2. The output torque of 1 and the rotational speed are controlled. A traveling transmission 5 having a torque converter 4 is connected to the output shaft of the engine 1. When the transmission 5 is driven by the engine 1, the axle 6 is driven to travel. A travel pedal 8 is provided as means for instructing the target rotational speed of the engine 1. A signal from the travel pedal 8 is input to the controller 10, and a control signal is output from the controller 10 to the electronic fuel injection device 2 based on the input to control the fuel injection amount. Further, the transmission 5 can switch the reduction ratio between high speed and low speed, and a speed change switch 11 is provided as means for instructing the switching. The signal of the speed changeover switch 11 is input to the controller 10, and based on the input, the controller 10 outputs a control signal to the transmission 5 to switch the reduction ratio.

  Further, a variable displacement hydraulic pump 15 is connected to the output shaft of the engine 1, and the hydraulic pump 15 is driven by the engine 1 to discharge pressure oil. A control valve 16 is connected to the discharge oil passage of the hydraulic pump 15. The control valve 16 is operated by operating means such as an operating lever and supplies pressure oil to the actuator 17. The actuator 17 is, for example, a hydraulic cylinder that drives a front working device of a wheel loader.

  The hydraulic pump 15 is provided with a torque control regulator 21. When the discharge pressure of the hydraulic pump 15 increases, the torque control regulator 21 decreases the tilt (capacity) of the hydraulic pump 15 accordingly, and the absorption torque of the hydraulic pump 15 exceeds the set value (maximum pump absorption torque). The tilting (capacity) of the hydraulic pump 15 is controlled so as not to occur. The set value (maximum pump absorption torque) of the torque control regulator 21 is variable and is controlled by the torque control solenoid valve 22. The torque control electromagnetic valve 22 is an electromagnetic proportional valve that operates using the discharge pressure of the hydraulic pump 15 as a hydraulic pressure source, and operates according to a control signal output from the controller 10.

  Further, the engine 1 is provided with a rotation sensor 25 for detecting the engine speed, and a signal from the rotation sensor 25 is also input to the controller 10.

  FIG. 2 shows an appearance of a wheel loader that is an example of a work vehicle to which the present invention is applied. In FIG. 2, reference numeral 100 denotes a wheel loader. The wheel loader 100 includes a vehicle body front portion 101 and a vehicle body rear portion 102, and the vehicle body front portion 101 and the vehicle body rear portion 102 are connected to each other via a connecting device 103 so as to be bent. Yes. A front working device 105 and a vehicle transfer (front wheel) 106 are provided in the vehicle body front portion 101, a driver's cab 107 and wheels (rear wheels) 108 are provided in the vehicle body rear portion 102, and a driver's seat 110 and a steering wheel are provided in the driver's cab 107. 111 and an operation lever 112 are provided. The front work device 105 includes a bucket 120 and a lift arm 121, and the bucket 120 is tilted and dumped by expansion and contraction of the bucket cylinder 122, and the lift arm 121 is moved up and down by expansion and contraction of the arm cylinder 123.

  Further, the engine 1 and the hydraulic pump 15 shown in FIG. 1 are arranged in the rear part 102 of the vehicle body together with the control valve 16, the torque control regulator 21 and the torque control valve 22, and the rear wheel 108 is driven by the engine 1 through the transmission 5 and the axle 6. Driven. The traveling pedal 8 is provided on the floor of the cab 107, the speed change switch 11 is provided in the front cabinet 113 of the cab 107, and the controller 10 is disposed in a suitable place in the cab 107, for example, below the driver seat 24. ing.

  The actuator 17 shown in FIG. 1 represents the bucket cylinder 122 and the arm cylinder 123, and the front working device 105 can be operated by driving them.

  FIG. 3 is a functional block diagram showing the control contents related to the pump control of the controller 10.

  The controller 10 has two tables 10a and 10b for determining the maximum absorption torque (maximum pump absorption torque) of the hydraulic pump 15 based on the engine speed, and the maximum pump absorption determined by the two tables 10a and 10b. A selection unit 10c that switches the torque depending on whether the reduction ratio of the transmission 5 is high speed or low speed, and an output unit 10d that outputs a command signal to the torque control solenoid valve 22 so as to obtain the maximum pump absorption torque selected by the selection unit 10c. And.

  Of the two tables 10a and 10b, the table 10a is for high speed and the table 10b is for low speed. The high speed table 10a has a pump absorption torque characteristic in which the maximum pump absorption torque is a constant value TA regardless of the engine speed. The constant value TA of the maximum pump absorption torque is, for example, the same magnitude as the set value of the conventional torque control regulator. The low speed table 10b also has a pump absorption torque characteristic in which the maximum pump absorption torque becomes a constant value TB regardless of the engine speed. The constant value TB of the maximum pump absorption torque is a value smaller than the constant value TA of the maximum pump absorption torque set in the high speed table 10b (that is, a value smaller than the set value of the conventional torque control regulator). If the maximum pump absorption torque of the high-speed and low-speed tables 10a and 10b is smaller in the latter than in the former (TA> TB), it may be variable according to the engine speed.

  Each of the two tables 10a and 10b inputs one rotation speed of the engine 1 detected by the rotation sensor 25, and determines the maximum pump absorption torque corresponding to it. The selector 10c receives a signal from the speed changeover switch 11, and when the signal indicates a high speed reduction ratio, selects the maximum pump absorption torque determined by the high speed table 10a, and the speed changeover switch 11 When the signal from S indicates a low speed reduction ratio, the maximum pump absorption torque determined by the low speed table 10b is selected.

  In the above, the torque control regulator 21 constitutes the first pump torque control means for controlling the absorption torque of the hydraulic pump 15 so as not to exceed the maximum absorption torque, and the tables 10a and 10b, the selection unit 10c, and the output unit 10d of the controller 10 The torque control solenoid valve 22 selects one of at least two pump absorption torque characteristics set in advance according to the reduction ratio of the transmission 5 instructed by the speed changeover switch 11 serving as a speed changeover instruction means, and sets the pump absorption torque as the pump absorption torque. Based on this, the second pump torque control means for controlling the maximum absorption torque of the hydraulic pump 1 is configured.

  FIG. 4 shows the discharge pressure (pump pressure) of the hydraulic pump 15 at which the torque control regulator 21 operates based on the set value variably controlled by the controller 10 and the torque solenoid valve 22 and the tilt (pump tilt) of the hydraulic pump 15. Show the relationship. When the high speed table 10a is selected, the maximum pump absorption torque of the hydraulic pump 15 is TA, and when the low speed table 10b is selected, the maximum pump absorption torque of the hydraulic pump 15 is TB. When the pump discharge pressure rises, the torque control regulator 21 reduces the pump tilt accordingly, and the hydraulic pump 15 tilts so that the absorption torque of the hydraulic pump 15 does not exceed the set value (maximum absorption torque) TA or TB. Control the rotation (capacity). Even at the same pump pressure P1, when the maximum pump absorption torque decreases from TA to TB, the pump tilt decreases from q2 to q1, and the pump discharge flow rate also decreases accordingly.

  FIG. 5 shows the output torque of the engine 1 (engine output torque), the maximum absorption torque of the hydraulic pump 15 (maximum pump absorption torque), and the transmission torque when the pump absorption torque determined by the high speed table 10a is selected. FIG. 6 shows the relationship between the engine output torque, the maximum pump absorption torque, and the transmission torque when the low-speed table 10b is selected. In the figure, A is the engine output torque, B is the maximum pump absorption torque, and the maximum pump absorption torque B corresponds to the pump absorption torque of the tables 10a and 10b. C is the maximum transmission torque at each transmission reduction ratio. The transmission torque is an input torque of the transmission 5 when the transmission 5 is driven by the engine 1, and the transmission torque increases as the engine speed increases. Further, when defining transmission speed ratio = output rotational speed of transmission 5 / input rotational speed of transmission 5 (= engine speed), transmission torque increases as the speed ratio decreases, and the speed reduction ratio is lower than high speed. However, since the speed ratio is small, the maximum transmission torque is larger at the high speed shown in FIG. 5 than at the low speed shown in FIG.

  5 and 6, the torque (traveling engine output torque) D distributed to the transmission 5 by the amount corresponding to the maximum pump absorption torque B with respect to the engine output torque A becomes lower. The intersection M between the traveling engine output torque D and the transmission torque C is a matching point between the maximum pump absorption torque and the transmission torque, and this is the engine speed.

  As shown in FIG. 5, when the signal from the speed changeover switch 11 indicates a high speed reduction ratio, the maximum pump absorption torque of the size TA determined by the high speed table 10a is selected as the maximum pump absorption torque B. Is done. The size of TA at this time is about the same as before, the decrease in engine output torque D for driving is also about the same as before, and the maximum when the driving load increases due to the combined operation of driving and front work device The matching point M between the pump absorption torque and the transmission torque is the same as in the prior art.

  Therefore, in work performed by switching the speed change switch 11 at a high speed, such as when carrying excavated earth and sand to the destination, the front work device can be moved quickly, and work efficiency is improved.

  As shown in FIG. 6, when the signal from the speed changeover switch 11 indicates a low speed reduction ratio, the maximum pump having a size TB (<TA) determined by the low speed table 10b as the maximum pump absorption torque B. Since the absorption torque is selected, the amount of decrease in the traveling engine output torque D is less than that at high speed. That is, the engine output torque D distributed to traveling increases. As a result, the matching point M between the maximum pump absorption torque and the transmission torque is maintained on the high torque, high rotation side, and a large running force can be obtained. Further, since the matching point M is kept on the high speed side and the decrease in the engine speed at the matching point M is small, the output horsepower of the engine can be used effectively.

  Therefore, in an operation performed by switching the speed changeover switch 11 to a low speed such as excavation work, the excavator can be pushed in with a large traveling force, and an efficient operation can be performed while effectively using the engine output horsepower.

  For comparison, FIG. 7 shows the relationship among the engine output torque, the maximum pump absorption torque, and the transmission torque in the prior art when the signal from the speed changeover switch 11 indicates a low speed reduction ratio.

  In the prior art, even when the signal from the speed changeover switch 11 indicates a low speed reduction ratio, the pump maximum absorption torque B is the same TA as at high speed, so the speed ratio becomes small at low speed and the transmission torque C Therefore, the matching point M between the maximum pump absorption torque and the transmission torque is greatly moved to the low speed side, the engine speed at the matching point M is greatly reduced, and the traveling engine torque is also greatly reduced. As a result, the running power decreased and the engine output horsepower could not be used effectively.

  As described above, according to the present embodiment, by changing the distribution of the pump absorption torque and the running torque depending on whether the reduction ratio of the transmission is high speed or low speed, the optimum pump absorption torque and running torque according to the reduction ratio can be obtained. Thus, efficient operation can be performed while effectively using the engine output horsepower.

  In addition, since the matching point M at the time of low speed is maintained on the high speed side as compared with the conventional case, the fuel consumption of the engine 1 can be improved. Furthermore, since the decrease in engine speed is small, operator fatigue can be reduced.

  In the above-described embodiment, the speed changeover switch 11 can switch the reduction ratio between two stages of high speed and low speed, but it may be switchable to three or more stages.

1 is a system configuration diagram of an entire drive device including a control device for a work vehicle according to an embodiment of the present invention. An appearance of a wheel loader which is an example of a work vehicle to which the present invention is applied is shown. The control contents related to the pump control of the controller are shown in a functional block diagram. It is a figure which shows the relationship between pump pressure and pump tilting when torque control is performed by a torque control regulator. It is a figure which shows the relationship between the engine torque at the time of high speed, a pump torque, and a transmission torque. It is a figure which shows the relationship between the engine torque at the time of low speed, a pump torque, and a transmission torque. It is a figure which shows the relationship between the engine torque in the prior art at the time of low speed, a pump torque, and a transmission torque.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Electronic fuel injection apparatus 4 Torque converter 5 Transmission 6 Axle 8 Traveling pedal 10 Controller 10a, 10b Table 10c Selection part 10d Output part 11 Speed change switch 15 Hydraulic pump 16 Control valve 17 Actuator 21 Torque control regulator 22 Torque control solenoid valve 25 Rotation sensor

Claims (1)

Engine,
A fuel injection device for controlling the output torque and the rotational speed of the engine;
A variable displacement hydraulic pump driven by the engine;
A hydraulic actuator driven by the oil discharged from the hydraulic pump;
First pump torque control means for controlling the absorption torque of the hydraulic pump so as not to exceed the maximum absorption torque;
A torque converter driven by the engine , and when the hydraulic pump is consuming the maximum absorption torque, the engine output torque for traveling is lower than the output torque of the engine by the maximum absorption torque of the hydraulic pump There a transmission for traveling to be dispensed,
Speed switching instruction means for instructing switching between a high speed and a low speed of a reduction ratio of the transmission ;
Selecting one of the at least first and second two pump absorption torque characteristic preset according to the reduction ratio of the transmission indicated by the pre-Symbol rate switching instruction means, said hydraulic pump based on the pump absorption torque and a second pump torque control means for controlling the maximum absorption torque of,
The second pump torque control means is configured to cause the maximum absorption torque of the hydraulic pump to be the first maximum absorption torque based on the first pump absorption torque characteristic when the transmission gear ratio is high. 1 pump torque control means is controlled, and when the transmission gear ratio is low, the maximum absorption torque of the hydraulic pump is smaller than the first maximum absorption torque based on the second pump absorption torque characteristic. The matching point between the maximum absorption torque of the hydraulic pump and the transmission torque, which is the input torque of the traveling transmission, is greater than when the maximum absorption torque of the hydraulic pump is the first maximum absorption torque. The first pump torque control means is controlled so as to be kept on the high engine speed side. Control device for a working vehicle, characterized in that that.

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