JP4376009B2 - Control device for work vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a work vehicle such as a wheel loader or a telescopic handler that drives a travel transmission by an engine and travels, and drives a hydraulic pump by the engine to operate a work actuator to perform a predetermined work.
[0002]
[Prior art]
Japanese Patent Publication No. 8-6613 and Japanese Patent No. 2968558 disclose conventional techniques for control devices in this type of work vehicle.
[0003]
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.
[0004]
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 secure 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.
[0005]
[Patent Document 1]
Japanese Patent Publication No. 8-6613 [Patent Document 2]
Japanese Patent No. 2968558 [0006]
[Problems to be solved by the invention]
As an example of work by a work vehicle such as a wheel loader or a telescopic handler, there is excavation work of earth and sand such as natural ground. In this excavation work, excavation is performed by advancing, and after excavation, the excavated earth and sand are lifted and moved backward. The excavation at the time of advance is performed while pushing the excavator of the front work device into the earth and sand by the traveling force (traveling traction force) and applying upward force to the excavator. In this case, since the excavating tool is pressed against the earth and sand by the traveling force at the time of forward movement, it is desirable to increase the traveling force as much as possible, and for that purpose, it is desirable to reduce the decrease in the engine speed. On the other hand, since excavation is not performed during reverse travel, a large traveling force is not required. On the other hand, it is desirable to increase the operating speed (front speed) of the front working device because the excavated sediment is lifted while moving backward.
[0007]
The prior art described in Japanese Patent Publication No. 8-6613 and Japanese Patent No. 2968558 does not control the forward time and the reverse time separately, and the optimum running force and front speed at the forward time and the reverse time. And can't get.
[0008]
SUMMARY OF THE INVENTION An object of the present invention is to provide a pump control device for a work vehicle that can obtain a large running force when moving forward and increase a front speed when moving backward by switching control characteristics between forward and reverse. .
[0009]
[Means for Solving the Problems]
(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, 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 , wherein the hydraulic pump is the maximum When the absorption torque is consumed, a traveling transmission in 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 the maximum absorption torque of the hydraulic pump is used for the traveling a pump torque switching means for varying in accordance with the reverse switching before transmission And a rotation speed detecting means for detecting a rotational speed of said engine, said pump torque switching means, wherein when the traveling transmission is in the forward, the maximum absorption torque of the hydraulic pump regardless of the rotational speed of the engine constant The pump torque control means is controlled so as to be the first maximum absorption torque, and when the traveling transmission is in reverse, the hydraulic pressure is determined in the high engine speed range based on the detected value of the engine speed detection means. A maximum absorption torque of the pump becomes a second maximum absorption torque that is larger than the first maximum absorption torque, and a third maximum absorption torque in which the maximum absorption torque of the hydraulic pump is lower than the second maximum absorption torque in the low engine speed range. The pump torque control means is controlled so that the absorption torque is obtained .
[0010]
By providing the pump torque switching means in this way and making the maximum absorption torque of the hydraulic pump variable according to the forward / reverse switching of the traveling transmission, the control characteristics can be switched between forward and reverse, so a large amount of travel during forward travel. Since the maximum pump absorption torque increases in the high engine speed range during reverse travel , the discharge flow rate of the hydraulic pump increases and the front speed can be increased . In addition, the maximum pump absorption torque is smaller in the low engine speed range during reverse travel than in the high engine speed range, and the engine torque for traveling is increased accordingly, so during acceleration traveling from the idle speed during reverse travel Good acceleration performance can be obtained without overtorque.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0016]
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.
[0017]
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 travel transmission 5 having a torque converter 4 is connected to the output shaft of the engine 1. The travel transmission 5 is driven by the engine 1 to drive the axle 6 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. The traveling transmission 5 can be switched forward and backward, and a forward / reverse selector switch 11 is provided as means for instructing switching of the forward / reverse travel. A signal from the forward / reverse selector switch 11 is input to the controller 10, and based on the input, the controller 10 outputs a control signal to the traveling transmission 5 to perform forward / reverse switching.
[0018]
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.
[0019]
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.
[0020]
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.
[0021]
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 work 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, a handlebar is 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.
[0022]
Further, the engine 1 and the hydraulic pump 15 shown in FIG. 1 are disposed in the vehicle body rear portion 102 together with the control valve 16, the torque control regulator 21 and the torque control valve 22, and the rear wheel 108 is connected to the engine 1 via the traveling transmission 5 and the axle 6. Driven by. The travel pedal 8 is provided on the floor of the operator cab 107, the forward / reverse selector switch 11 is provided in the front cabinet 113 of the operator cab 107, and the controller 10 is disposed in a suitable place in the operator cab 107, for example, below the driver seat 24. Has been.
[0023]
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.
[0024]
FIG. 3 is a functional block diagram showing the control contents related to the pump control of the controller 10.
[0025]
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 depending on whether the torque is forward or reverse, 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 that is switched by the selection unit 10c and selected. Yes.
[0026]
Of the two tables 10a and 10b, the table 10a is for forward travel, and the table 10b is for reverse travel. A constant maximum pump absorption torque is set in the table 10a for forward travel regardless of the engine speed. The constant maximum pump absorption torque is, for example, a magnitude TA comparable to the set value of the conventional torque control regulator. The reverse travel table 10b has the same magnitude TA as the maximum pump absorption torque of the forward travel table 10a in the low rotation range, and the maximum pump absorption torque of the forward travel table 10a in the high rotation range. The maximum pump absorption torque that gradually increases from TA to TB is set in the middle rotation region.
[0027]
The two tables 10a and 10b each input the number of rotations of the engine 1 detected by the rotation sensor 25 and determine the maximum absorption torque according to the input. The selector 10c receives a signal from the forward / reverse selector switch 11 and, when the signal indicates the forward time, selects the maximum pump absorption torque determined by the forward table 10a, and the forward / reverse selector switch 11 When the reverse signal indicates the reverse travel time, the maximum pump absorption torque determined by the reverse travel table 10b is selected.
[0028]
In the above, the torque control regulator 21 constitutes 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, the output unit 10d of the controller 10 and the torque control. The electromagnetic valve 22 constitutes a pump torque switching means that makes the maximum absorption torque of the hydraulic pump 15 variable according to the forward / reverse switching of the traveling transmission 5.
[0029]
FIG. 4 shows the discharge pressure (pump pressure) of the hydraulic pump 15 and the tilt of the hydraulic pump 15 (pump tilt) when the torque control regulator 21 is operated based on the set value variably controlled by the controller 10 and the torque solenoid valve 22. Shows the relationship. When the table 10a for forward travel is selected and when the table 10b for backward travel is selected and the engine 1 is in the low speed range, the maximum pump absorption torque of the hydraulic pump 15 is TA, and the table 10b for reverse travel is When the selected engine 1 is in the high speed range, the maximum pump absorption torque of the hydraulic pump 15 is TB. When the pump discharge pressure increases, the torque control regulator 21 decreases the pump tilt along the characteristic line of the maximum pump absorption torque, and the absorption torque of the hydraulic pump 15 is set to a set value (maximum absorption torque) TA or The tilt (capacity) of the hydraulic pump 15 is controlled so as not to exceed TB. Even if the pump pressure P1 is the same, when the maximum pump absorption torque increases from TA to TB, the pump tilt increases from q1 to q2, and the pump discharge flow rate also increases accordingly.
[0030]
FIG. 5 shows the relationship between the output torque (engine output torque) A of the engine 1 during forward travel, the maximum absorption torque (maximum pump absorption torque) B of the hydraulic pump 15 and the transmission torque C, and FIG. 6 shows the engine output during reverse travel. The relationship among torque A, maximum pump absorption torque B, and transmission torque C is shown. The magnitude of the maximum pump absorption torque B during forward movement is TA, and the magnitude of the maximum pump absorption torque B during backward movement is TA in the low rotation range and TB in the high rotation range.
[0031]
The transmission torque C is an input torque of the transmission 5 when the transmission 5 is driven by the engine 1, and the transmission torque C 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 rotational speed), transmission torque C increases as the speed ratio decreases. The transmission torque C shown in FIGS. 5 and 6 is at a certain transmission speed ratio.
[0032]
5 and 6, the torque (traveling engine output torque) D that can be used in the travel transmission 5 is reduced by the maximum pump absorption torque B with respect to the engine output torque A. The intersection M between the traveling engine output torque D and the transmission torque C is a matching point, which is the engine speed.
[0033]
As the maximum pump absorption torque B at the time of forward movement, the maximum pump absorption torque having the same magnitude TA as the conventional value determined by the table 10a shown in FIG. 3 is selected. Further, the maximum pump absorption torque B is constant throughout the entire rotation range. For this reason, the front working device can be moved at the same speed as the conventional one. In addition, the decrease in the engine output torque D for traveling is about the same as that in the past, and the engine output torque D for traveling and the engine speed at the matching point M are moderately decreased as in the conventional case. For this reason, at the time of advance, a large traveling force similar to the conventional one can be obtained, and excavation work can be performed efficiently.
[0034]
Since the maximum pump absorption torque B determined by the table 10b in FIG. 3 is selected as the maximum pump absorption torque B at the time of reverse travel, the maximum pump absorption torque B in the high rotation region becomes TB larger than the conventional one, and the low rotation region The maximum pump absorption torque B at is TA, and is between TA and TB in the middle rotation region.
[0035]
Therefore, from the middle rotation region to the high rotation region during reverse travel, the maximum tilt of the hydraulic pump 15 increases from q1 to q2 at the pump pressure P1 as described with reference to FIG. 4, and the discharge flow rate of the hydraulic pump 15 also increases. . As a result, the driving speed of the actuator 7 is increased, and the operating speed (front speed) of the front working device is increased. Therefore, when moving backward, the excavated sediment can be moved quickly while being lifted. Note that the decrease in the traveling engine output torque D from the middle rotation region to the high rotation region is increased accordingly, and the traveling engine output torque D and the engine speed at the matching point M are decreased as compared with the related art. However, there is no problem because the excavation is not carried out when going backward.
[0036]
Further, since the maximum pump absorption torque B is set to a TA lower than that in the high rotation region in the low rotation region, good acceleration performance can be obtained without overtorque during acceleration traveling from the idle rotation speed due to depression of the travel pedal 8. .
[0037]
As described above, according to the present embodiment, by switching the control characteristics between forward and reverse, a large running force can be obtained during forward travel, and the front speed can be increased during reverse travel, resulting in excavation work. It can be done efficiently. Also, good acceleration performance can be obtained without overtorque during acceleration running from idle speed.
[0038]
【The invention's effect】
According to the present invention, by switching the control characteristics between forward and reverse, a large running force can be obtained during forward travel, and the front speed can be increased during reverse travel, resulting in efficient excavation work. .
[0039]
In addition, according to the present invention, good acceleration performance can be obtained without over-torque during acceleration traveling from idle speed.
[Brief description of the drawings]
FIG. 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.
FIG. 2 shows an appearance of a wheel loader as an example of a work vehicle to which the present invention is applied.
FIG. 3 is a functional block diagram showing control contents related to pump control of the controller.
FIG. 4 is a diagram showing a relationship between pump pressure and pump tilt when torque is controlled by a torque control regulator.
FIG. 5 is a graph showing the relationship among engine torque, pump torque, and transmission torque during forward travel.
FIG. 6 is a diagram showing the relationship among engine torque, pump torque, and transmission torque during reverse travel.
[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 Forward / reverse changeover switch 15 Hydraulic pump 16 Control valve 17 Actuator 21 Torque control regulator 22 Torque control electromagnetic 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;
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 A traveling transmission that is distributed ,
Pump torque switching means for varying the maximum absorption torque of the hydraulic pump according to the forward / reverse switching of the traveling transmission ;
A rotational speed detection means for detecting the rotational speed of the engine ;
The pump torque switching means controls the pump torque control means so that the maximum absorption torque of the hydraulic pump becomes a constant first maximum absorption torque regardless of the engine speed when the traveling transmission is in a forward direction. When the traveling transmission is in reverse, the maximum absorption torque of the hydraulic pump is larger than the first maximum absorption torque in the high engine speed range based on the detection value of the engine speed detection means. The pump torque control means is controlled so that the maximum absorption torque of the hydraulic pump becomes a third maximum absorption torque lower than the second maximum absorption torque in the low engine speed range. A control device for a work vehicle.

Images