WO2011115290A1

WO2011115290A1 - Working vehicle engine control device and engine control method

Info

Publication number: WO2011115290A1
Application number: PCT/JP2011/056723
Authority: WO
Inventors: 雅明今泉
Original assignee: 株式会社小松製作所
Priority date: 2010-03-19
Filing date: 2011-03-22
Publication date: 2011-09-22

Abstract

The disclosed device is provided with: a torque limit mode switch (112); an accelerator pedal sensor (105) which detects the accelerator opening degree; and a transmission controller (106). When the torque limit mode switch (112) has designated an output torque limit, if the accelerator opening degree is less than a threshold value (Os), the transmission controller (106) limits the output torque of the engine in accordance with an equal horsepower characteristic curve (LN0) which constitutes the horsepower passing through the maximum output torque point (P1) during the idle revolution of the engine, and if the accelerator opening degree is not less than a threshold value (Os), the transmission controller (106) limits the output torque of the engine in accordance with an in-travel torque limit characteristic curve (LN1) wherein the limit torque gradually increases according to the increase of the accelerator opening degree, from an intersection point (P2) between the equal horsepower characteristic curve (LN0) and the absorption torque curve of a travel system, toward a matching point (M1) between a maximum torque line and the absorption torque curve of the travel system. Thus, the fuel consumption for a part of surface of a region (R1) is suppressed more than during engine control by the maximum torque line (Tmax), thus fuel consumption can be reduced.

Description

Engine control apparatus and engine control method for work vehicle

The present invention relates to an engine control device and an engine control method for a work vehicle that drives a traveling system and a work machine system with a common engine output.

Conventionally, construction machines that control engine output according to the amount of operation of an accelerator pedal are known. In the present specification, “construction machine” refers to a driving system for driving a vehicle and a working machine system such as a loader or a steering mechanism by a common engine output. A loader, a skid steer loader, etc. can be illustrated.

This type of construction machine is required to operate stably regardless of its work load when the work machine is operated. Against this background, in this type of construction machine, the engine control device controls the fuel injection amount of the engine so that the fluctuation of the engine speed with respect to the fluctuation of the work load becomes small. In such engine control, the engine speed is determined according to the amount of operation of the accelerator pedal, and the engine output torque is controlled to the maximum torque that can be output so as to maintain the engine speed (see Patent Document 2). (See FIG. 5). On the other hand, in traveling, the engine control device follows the engine torque curve indicating the maximum torque of the engine from the current engine speed to the engine speed corresponding to the amount of operation of the accelerator pedal. And output torque of the engine is controlled toward a matching point where the absorption torque of the torque converter of the traveling system is balanced. According to such a construction machine, it is possible to stabilize the traveling speed and the operation of the work machine system against the fluctuation of the engine load.

JP 2001-090574 A Japanese Patent Laying-Open No. 2008-180203 (FIG. 5)

By the way, when the accelerator pedal operation amount is not the maximum operation amount, such as when driving at low speed, so-called half accelerator operation, the output torque as much as the maximum torque is often not required, and acceleration Sex is not so required. However, the construction machine described above outputs the maximum torque until it reaches the engine speed corresponding to the operation amount of the accelerator pedal, regardless of the required output torque amount. For this reason, in the construction machine described above, even when the output torque as much as the maximum torque is not required, the maximum torque is output until the engine speed corresponding to the accelerator pedal is reached. However, since fuel is injected in a region where the efficiency of the torque converter is not good, fuel is wasted and this is one of the factors that deteriorate fuel consumption.

The present invention has been made in view of the above, and an object thereof is to provide an engine control device and an engine control method for a work vehicle that can reduce fuel consumption.

In order to solve the above-described problems and achieve the object, an engine control device for a work vehicle according to the present invention includes an operation amount detection unit that detects an operation amount of the work vehicle, and an operation detected by the operation amount detection unit. Control means for limiting the output torque of the engine in accordance with an equal horsepower characteristic curve that is a horsepower passing through a maximum output torque point when the engine is idling when the operation amount of the vehicle is less than a threshold value. .

The engine control method for a work vehicle according to the present invention includes an operation amount detection step for detecting an operation amount of the work vehicle, and an engine amount when the operation amount of the work vehicle detected by the operation amount detection step is less than a threshold value. And a control step for limiting the output torque of the engine in accordance with an equal horsepower characteristic curve that is a horsepower passing through the maximum output torque point during idle rotation.

According to the present invention, when the operation amount of the work vehicle is less than the threshold value, the engine output torque is limited according to an equal horsepower characteristic curve that is a horsepower passing through the maximum output torque point at the time of engine idle rotation. The fuel efficiency can be reduced while maintaining the required driving performance.

FIG. 1 is a schematic side view showing the overall configuration of a wheel loader according to an embodiment of the present invention. FIG. 2 is a block diagram showing a configuration of a control system of the wheel loader shown in FIG. FIG. 3 is a diagram showing the relationship between engine output torque, engine speed, and accelerator pedal opening in conventional engine control processing. FIG. 4 is a diagram showing the relationship between the torque limit value, the engine speed, and the accelerator pedal opening when torque limit control is performed using the accelerator opening. FIG. 5 is a flowchart showing an engine control processing procedure according to an embodiment of the present invention. FIG. 6 is a diagram showing the relationship between the target value of the hydraulic pump absorption torque of the work implement and the opening degree of the accelerator pedal. FIG. 7 is a diagram showing the relationship between the torque limit value, the engine speed, and the accelerator pedal opening when torque limit control is performed using the engine speed. FIG. 8 is a diagram showing the relationship between the torque limit value, the engine speed, and the accelerator pedal opening when the torque limit control is performed by combining the accelerator opening and the engine speed. FIG. 9 corresponds to FIG. 4 and is an explanatory diagram for explaining fuel efficiency improvement when torque limit control is performed using the accelerator opening. FIG. 10 corresponds to FIG. 7 and is an explanatory diagram for explaining fuel efficiency improvement when torque limit control is performed using the engine speed. FIG. 11 corresponds to FIG. 8 and is an explanatory diagram for explaining fuel efficiency improvement when torque limit control is performed by combining the accelerator opening and the engine speed. FIG. 12 is a diagram illustrating temporal changes in the accelerator opening, the engine speed, and the limit torque when the torque limit control according to the present embodiment is applied to the V shape work of the wheel loader.

Hereinafter, a configuration of a wheel loader according to an embodiment of the present invention and a flow of an engine control process thereof will be described with reference to the drawings. The scope of application of the present invention is not limited to the wheel loader, and can be similarly applied to any work vehicle in which a common engine output is distributed to the traveling system and the work machine system.

[Wheel loader overall configuration]
First, an overall configuration of a wheel loader that is one embodiment of the present invention will be described with reference to FIG.

FIG. 1 is a schematic side view showing the overall configuration of a wheel loader according to an embodiment of the present invention. As shown in FIG. 1, a wheel loader 1 according to an embodiment of the present invention includes a work machine 2, a frame unit 3, and a vehicle body 4.

The work machine 2 includes a lift arm 5. The lift arm 5 is attached to the frame portion 3 with a base end portion freely swingable. The frame portion 3 and the lift arm 5 are connected by a pair of lift cylinders 6. The lift arm 5 swings as the lift cylinder 6 expands and contracts according to the operation of the work implement lever by the operator. A bucket 7 is swingably attached to the tip of the lift arm 5. The work machine 2 includes a bell crank (tilt lever) 8. The bell crank 8 is rotatably supported at a substantially central portion of the lift arm 5. One end portion of the bell crank 8 and the frame portion 3 are connected by a tilt cylinder 9. The other end of the bell crank 8 and the bucket 7 are connected by a tilt rod 10. The bucket 7 swings as the tilt cylinder 9 expands and contracts according to the operation of the work implement lever by the operator.

The vehicle body 4 is equipped with a traveling device for traveling the wheel loader 1 and an engine 11 for supplying drive output to the traveling device. The traveling device includes a PTO mechanism 12, a torque converter (T / C) 13, a transmission 15 that can be switched forward and backward and a plurality of shift speeds, a transfer 16, and a speed reducer 19 that drives a front wheel 17 and a rear wheel 18. Is provided. The drive output of the engine 11 is transmitted to the transfer 16 through the PTO mechanism 12, the T / C 13, and the transmission 15 in this order, and is transmitted to the speed reducer 19 on the front wheel 17 and rear wheel 18 side by the transfer 16. The speed reducer 19 transmits the drive output of the engine 11 transmitted by the transfer 16 to the front wheels 17 and the rear wheels 18.

The vehicle body 4 is equipped with a variable displacement hydraulic pump 20 that supplies pressure oil to the lift cylinder 6 and the tilt cylinder 9 via a work machine control valve (not shown). The hydraulic pump 20 is connected to the engine 11 via the PTO mechanism 12 and is driven using a part of the drive output of the engine 11. The pump capacity of the hydraulic pump 20 is variably controlled by changing the inclination angle of the swash plate of the hydraulic pump 20 by a controller (not shown). A driver's cab 21 is provided in the upper part of the vehicle body 4. A driving operation device 22 including a transmission shift lever, an accelerator pedal, a brake pedal, and a work implement lever for operating the work implement 2 operated by the driver is provided in the cab 21. The driver can operate the driving operation device 22 to perform forward / reverse switching of the wheel loader 1, adjustment of traveling speed (acceleration and deceleration), and operation of the work machine 2.

[Configuration of engine control unit]
Next, the configuration of the engine control device that controls the operation of the engine 11 will be described with reference to FIG.

FIG. 2 is a block diagram showing a configuration of an engine control device that controls the operation of the engine 11 of the wheel loader 1 shown in FIG. As shown in FIG. 2, the engine control apparatus 100 includes an engine speed sensor 101, a speed stage sensor 103, a work implement lever sensor 104, an accelerator pedal sensor 105, a transmission controller 106, an engine controller 107, a work implement controller 111, and torque. A restriction mode switch 112 is provided.

The engine speed sensor 101 is attached to the output rotation shaft of the engine 11 and detects the engine speed. The engine speed sensor 101 inputs an electric signal indicating the engine speed to the transmission controller 106.

The speed stage sensor 103 detects the operation position of the speed stage lever 108 for switching the speed stage of the transmission 15 and inputs an electric signal indicating the detected operation position to the transmission controller 106. The work machine lever sensor 104 detects an operation amount of the work machine lever 109 for operating the work machine 2 and inputs an electric signal indicating the detected operation amount to the work machine controller 111.

The accelerator pedal sensor 105 detects an operation amount of the accelerator pedal 110 and inputs an electric signal indicating the detected operation amount to the transmission controller 106. The work machine controller 111 controls the pump capacity of the hydraulic pump 20 by driving the swash plate actuator 20 a based on the electrical signal input from the work machine lever sensor 104 and controlling the inclination angle of the swash plate of the hydraulic pump 20. To do. The pressure oil discharged from the hydraulic pump 20 drives the lift cylinder 6, the tilt cylinder 9, and the like. The engine speed sensor 101 and the accelerator pedal sensor 105 function as an operation amount detection unit according to the present invention.

The transmission controller 106 is realized by a microcomputer including a CPU, a RAM, a ROM, an input / output circuit, and the like. In the ROM of the transmission controller 106, a control program, a map 106a indicating the relationship between the output torque limit value of the engine 11 and the accelerator opening, and a map indicating the relationship between the work machine pump torque target value and the accelerator opening. 106b is stored.

The CPU in the transmission controller 106 loads the control program into the RAM, and executes the control program loaded into the RAM, whereby the engine speed sensor 101, the speed stage sensor 103, the accelerator pedal sensor 105, and the work machine. A control signal for controlling the operation of the engine 11 is output to the engine controller 107 in accordance with the electrical signal input from the controller 111. The transmission controller 106 functions as control means according to the present invention.

The engine controller 107 is realized by a microcomputer including a CPU, a RAM, a ROM, an input / output circuit, and the like. A control program is stored in advance in the engine controller 107. The CPU in the engine controller 107 loads the control program into the RAM and executes the control program loaded in the RAM, thereby controlling the operation of the engine 11 according to the control signal input from the transmission controller 106. Specifically, the CPU in the engine controller 107 controls the operation of the fuel injection device 11 a that controls the fuel injection amount of the engine 11 in accordance with a control signal input from the transmission controller 106.

The torque limit mode switch 112 is an operator operated by an operator, and is a switch for selecting and instructing a torque limit mode in which fuel efficiency is emphasized without requiring so much acceleration according to an operation by the operator. The torque limit mode switch 112 inputs a torque limit mode selection instruction signal to the work machine controller 111.

In the present embodiment, the transmission controller 106, the engine controller 107, and the work machine controller 111 are configured separately, but the transmission controller 106, the engine controller 107, and the work machine controller 111 may be configured integrally. Also, the signals input from the sensors are not limited to the controller input in the present embodiment, and data may be obtained through communication between the controllers. The control programs and maps stored in the transmission controller 106 and the engine controller 107 are files that can be installed or executed, and can be read by computers such as CD-ROMs, flexible disks, CD-Rs, and DVDs. The recording medium may be recorded and provided. Further, the control program and the map may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. Moreover, you may comprise so that a control program and a map may be provided or distributed via telecommunication lines, such as the internet.

[Engine control processing]
Next, the flow of engine control processing for reducing the fuel consumption of the wheel loader 1 will be described with reference to FIGS. 3 to 8.

FIG. 3 is a diagram showing the relationship between engine output torque, engine speed, and accelerator pedal opening (accelerator opening) in conventional engine control processing. In FIG. 3, symbol A is an output torque curve showing a change in engine output torque accompanying the operation of the accelerator pedal. Symbol Tmax (broken line) is an engine torque curve indicating the maximum torque that can be output by the engine. Reference numeral N ₀ is an engine speed that is normally referred to as an idling speed, in which an accelerator opening is zero and a minimum speed at which the engine does not stall is set. Reference numerals C1 to C3 are equal horsepower curves showing the relationship between the engine output torque at which the engine output horsepower becomes constant, the engine speed and the accelerator opening. The horsepower gradually increases from the equal horsepower curves C1 to C3. The output horsepower of the engine increases in order from the equal horsepower curve C1 toward the equal horsepower curve C3. Incidentally, equal horsepower curve C1 is a curve passing through the maximum torque point when the engine rotational speed N is close to _0. Reference symbol D represents an absorption torque curve of T / C13. The absorption torque curve D rises and falls according to the speed stage of the transmission 15, the roadbed state, the flat road running, the uphill running, and the downhill running, in other words, according to the magnitude of the load related to the running. The absorption torque curve D shown in FIG. 3 is obtained when the speed stage of the transmission 15 is at the maximum speed stage and traveling on flat ground. Reference numerals L1 to L6 are examples of the regulation line for each accelerator opening used when adjusting the speed (adjusting the fuel injection amount so as to achieve the target engine speed), and depressing the accelerator pedal greatly. For example, if the accelerator opening increases, the regulation line L1 changes to L6, and if the depression amount is Full, the engine torque curve Tmax is obtained. The illustrated relationship between the engine speed and the accelerator pedal depression amount (accelerator opening) is an example of the embodiment, and the engine speed and the accelerator opening that are the maximum output torque of the regulation line are expressed as follows. You may associate. Further, the accelerator opening degree Full need not correspond to the maximum engine speed. For example, the accelerator opening degree Full may pass through the engine torque curve Tmax line at an accelerator opening degree of 80%. Further, although the regulation lines are discretely shown from L1 to L6, it does not prevent the regulation line from changing linearly according to the change in the operation amount of the accelerator pedal.

In the conventional engine control process, as shown by the solid line (arrow A) of the output torque curve in FIG. 3, when the accelerator pedal is operated, the engine output torque is the engine speed near the engine speed N ₀ . Is controlled to the maximum torque that can be output and rises as shown by a solid line, and the engine output torque and the absorption torque curve of the traveling system along the engine torque curve Tmax indicating the maximum torque as the engine speed increases. Control is performed toward a matching point M with D. Here, the output torque of the engine that contributes to actual traveling is the lower part of the absorption torque curve D of the traveling system, and the upper part contributes to acceleration until shifting to the matching point M. For this reason, in the conventional engine control process, the maximum torque is output until the engine speed reaches the matching point M. Therefore, the output corresponding to the area of the region R0 shown in FIG. The horsepower is used to improve acceleration, and is absorbed by the torque converter in an inefficient state, which is one of the factors that deteriorate fuel consumption.

Suppose further that the maximum speed is not required and the accelerator pedal is half-accelerated. If the engine control is performed so that the engine output torque moves on the regulation line L4 by the half accelerator operation, the matching point with the absorption torque curve D of the traveling system is M ′, and the output torque curve is indicated by an arrow. The engine is controlled so as to decrease the output torque along the regulation line L4. That is, in the half accelerator operation, the torque required for traveling is about the output torque at the matching point M ′, and the maximum output torque of the engine is not required. Therefore, in the case of half-acceleration operation, the degree of deterioration of fuel consumption due to excessive consumption of fuel in a low speed region lower than the desired speed (speed obtained by the engine speed at the matching point M ′). Is getting fierce.

Thus, in the wheel loader 1 according to the embodiment of the present invention, the transmission controller 106 limits the output torque of the engine, thereby suppressing fuel consumption and reducing fuel consumption. That is, as shown in FIG. 4, when the accelerator opening is less than Os (threshold), an equal horsepower characteristic curve that is a horsepower passing through the maximum output torque point P1 at the time of engine idling (idle engine speed N ₀ ). The engine output torque is limited according to an equal horsepower torque limit curve LN0 which is a part of C1. The accelerator opening degree Os is an accelerator opening degree corresponding to a regulation line Ls passing through the intersection P2 between the absorption torque curve D and the equal horsepower characteristic curve C1 shown in FIG. In addition, when the accelerator opening is equal to or greater than Os, the limit torque gradually increases as the accelerator opening increases from the intersection point P2 toward the matching point M1 between the absorption torque curve D of the traveling system and the maximum torque line Tmax. The engine output torque is limited according to the hour torque limit characteristic curve LN1. Further, when the accelerator opening is equal to or greater than Os and the work implement lever operation amount detected by the work implement lever sensor 104 exceeds a predetermined value, the intersection P2 is changed to the maximum horsepower point M2 on the maximum torque line Tmax. The engine output torque is limited in accordance with a torque limitation characteristic curve LN2 during operation that gradually increases as the accelerator opening increases.

That is, when the accelerator opening is greater than or equal to Os and the work implement lever operation amount is less than or equal to a predetermined value, the engine output torque is in accordance with the torque limit curve TL1 including the equal horsepower torque limit curve LN0 and the running torque limit characteristic curve LN1. When the accelerator opening is greater than or equal to Os and the working machine lever operation amount exceeds a predetermined value, the engine output torque is determined according to the torque limit curve TL2 composed of the equal horsepower torque limit curve LN0 and the working torque limit characteristic curve LN2. Limited. When traveling with the working machine lever operation amount being a predetermined value or less, torque limitation is performed to minimize the absorption torque of the hydraulic pump 20 that drives the working machine 2. Conversely, the limit on the absorption torque of the hydraulic pump 20 is released only when the accelerator opening is equal to or greater than Os and the work implement lever operation amount exceeds a predetermined value. That is, as shown in the map 106b in FIG. 6, when the accelerator opening is less than Os, the working machine hydraulic pump torque target value is set to the minimum value (L10), and the accelerator opening is Os or more. Even when the work implement lever operation amount is equal to or less than the predetermined value, the work implement hydraulic pump torque target value is set to the minimum value (L12), the accelerator opening is equal to or greater than Os, and the work implement lever operation amount is the predetermined value. When exceeding, the working machine hydraulic pump torque target value is set to the maximum value (L11). Here, the torque limit of the hydraulic pump 20 is controlled by a swash plate actuator 21a that controls the swash plate angle of the swash plate. The running torque limit characteristic curve LN1 preferably corresponds to the absorption torque curve D of the traveling system, but the absorption torque curve D of the traveling system varies depending on the speed stage, for example, the absorption torque curve of the first forward speed, the forward 2 There is a fast absorption torque curve. Here, the running torque limit characteristic curve LN1 is preferably a curve equal to or higher than the absorption torque curve of the fourth forward speed, for example, because high speed operation is performed in the high engine speed range.

Hereinafter, an engine control processing procedure for limiting engine output torque by the transmission controller 106 will be described with reference to a flowchart shown in FIG. FIG. 5 is a flowchart showing an engine control processing procedure for limiting the output torque of the engine by the transmission controller 106. The engine control process by the transmission controller 106 starts at the timing when the ignition switch of the wheel loader 1 is switched from the off state to the on state, and proceeds to the process of step S1.

First, in the process of step S1, the transmission controller 106 detects the operation amount (accelerator opening) of the accelerator pedal 110 via the accelerator pedal sensor 105, and determines the work implement lever operation amount detected by the work implement lever sensor 104. Detecting via the work machine controller 111.

Thereafter, the transmission controller 106 determines whether or not the torque limit mode switch 112 is turned on via the work machine controller 111 (step S2). When the torque limit mode switch 112 is on, it indicates that the torque limit mode is in the selection instruction state. If the torque limit mode switch 112 is not on (step S2, No), the engine output torque is not limited (step S3), and this process is terminated. When the engine output torque is not limited, the matching point is reached through the maximum torque line Tmax with high acceleration as shown in FIG.

On the other hand, when the torque limit mode switch 112 is on (step S2, Yes), the transmission controller 106 refers to the map 106b shown in FIG. 6 and controls the swash plate of the hydraulic pump 20 via the swash plate actuator 20a. The pump absorption torque is limited to the minimum by minimizing the inclination angle (step S4). That is, the working machine hydraulic pump torque target value is initially set to TPmin.

Thereafter, the transmission controller 106 determines whether or not the accelerator opening is less than the threshold value Os (step S5). When the accelerator opening is less than the threshold value Os (step S5, Yes), the torque limit value on the equal horsepower torque limit curve LN0 corresponding to the accelerator opening is acquired with reference to the map 106a shown in FIG. S6). For example, when the accelerator opening is Ox, the intersection Mx between the regulation line Lx of the engine speed Nx corresponding to the accelerator opening Ox and the equal horsepower torque limit curve LN0 is obtained, and the torque limit value Tx of this intersection Mx is obtained. get. Thereafter, the process proceeds to step S11.

On the other hand, when the accelerator opening is equal to or greater than the threshold value Os (step S5, No), the transmission controller 106 further determines whether or not the work machine lever operation amount exceeds a predetermined value Bmin (step S7). This predetermined value Bmin is a value for determining whether or not the work implement lever is operated, and is, for example, a value of 5% of the lever stroke. When the work machine lever operation amount is equal to or smaller than the predetermined value Bmin (step S7, No), the torque limit value on the running torque limit characteristic curve LN1 corresponding to the accelerator opening is referred to with reference to the map 106a shown in FIG. Obtain (step S8). For example, when the accelerator opening is Oy, an intersection My1 between the regulation line Ly of the engine speed Ny corresponding to the accelerator opening Oy and the running torque limit characteristic curve LN1 is obtained, and the torque limit value Ty1 of the intersection My1 To get. Thereafter, the process proceeds to step S11.

When the working machine lever operation amount exceeds the predetermined value Bmin (step S7, Yes), the torque limit value on the working torque limit characteristic curve LN2 corresponding to the accelerator opening is acquired with reference to the map 106a shown in FIG. (Step S9). For example, when the accelerator opening is Oy, an intersection My2 between the regulation line Ly of the engine speed Ny corresponding to the accelerator opening Oy and the working torque limit characteristic curve LN2 is obtained, and the torque limit value Ty2 of the intersection My2 is obtained. To get. Thereafter, the transmission controller 106 releases the restriction that minimized the pump absorption torque by minimizing the inclination angle of the swash plate of the hydraulic pump 20 (step S10). That is, in the map 106b shown in FIG. 6, since the accelerator opening is equal to or greater than Os (region R11) and the working machine lever operation amount exceeds the predetermined value Bmin, the limit of the pump absorption torque is released, and the working machine The hydraulic pump torque target value is allowed up to TPmax (L11). Thereafter, the process proceeds to step S11. Even when the accelerator opening is equal to or greater than Os (region R11), when the operating lever operating amount is equal to or smaller than a predetermined value Bmin, the accelerator is initially set and the pump absorption torque is limited (see FIG. 6 L12). Further, when the accelerator opening is less than Os (region R10), it is in an initially set state, and the pump absorption torque is limited (L10 in FIG. 6). Note that the processing order of step S9 and step S10 may be interchanged.

In step S11, the engine output torque is limited according to the torque limit values Tx, Ty1, Ty2 obtained in steps S6, S8, S9, respectively (step S11). That is, the torque limit value is output from the transmission controller 106 to the engine controller 107, and the engine controller 107 controls the output torque of the engine 11 based on the torque limit value. In order to perform control corresponding to the regulation line determined from the accelerator opening, the engine controller 107 determines the fuel injection amount so as to output torque on the regulation line corresponding to the engine speed at that time. Here, when the torque limit value is input from the transmission controller 106, the engine controller 107 determines the fuel injection amount using the torque limit value as the output torque, not the output torque on the regulation line. For this reason, when the torque limit values are Tx, Ty1, and Ty2, the engine speed and output torque of the engine 11 rise at the idling engine speed N ₀ so as to pass the paths X, Y1, and Y2 shown in FIG. The engine speed is controlled to increase while maintaining the output torques Tx, Ty1, Ty2, respectively. And it will go to matching point Mx, My1, My2 according to the accelerator opening, respectively.

In this embodiment, since the regulation line is determined by the accelerator opening, the map 106a of the torque limit value with respect to the accelerator opening described in FIG. 4 is a numerical table with the accelerator opening as a variable. You can also In addition, since the relationship between the accelerator opening and the regulation line is used even in normal engine control without torque limitation, a map showing the relationship between the accelerator opening and the regulation line is provided in the engine controller 107 and selected. It is also possible to cause the transmission controller 106 to read out the regulation line.

In the embodiment described above, the running torque limit characteristic curve LN1 is the same as the absorption torque curve D of the running system. However, the running torque limit characteristic curve LN1 is not limited to the absorption torque curve D of the running system, and may be any curve that gradually increases toward the matching point M1 as the accelerator opening increases. Further, a plurality of torque limiting characteristic curves are further provided between the running torque limiting characteristic curve LN1 and the working torque limiting characteristic curve LN2, and for example, a plurality of threshold values are provided for the work machine lever operation amount to correspond to each threshold value. You may make it transfer to a some torque limitation characteristic curve.

In the above-described embodiment, the fixed torque limit value is calculated based on the accelerator opening, but the torque limit value may be calculated sequentially based on the engine speed. In this case, in the ROM of the transmission controller 106, a map showing the relationship between the output torque limit value (torque limit value) of the engine 11 and the accelerator opening as shown in FIG. A map to which is added is stored. In the map shown in FIG. 7, the torque limit values are the torque limit curve TL1 composed of the equal horsepower torque limit curve LN0 and the running torque limit characteristic curve LN1, the equal horsepower torque limit curve LN0, and the working torque limit characteristic curve LN2. It changes in accordance with a torque limit curve TL2 consisting of The torque limit curves TL1 and TL2 are the same as those shown in FIG. 4 from the viewpoint that the regulation line is determined by the accelerator opening. On the other hand, it can be explained as follows from the viewpoint of the engine speed. That is, the torque limit value changes according to the equal horsepower torque limit curve LN0 when the engine speed is less than the threshold value Ns ′, and when the engine speed becomes equal to or greater than the threshold value Ns ′, the running torque limit characteristic curve LN1 or the working torque. According to the limiting characteristic curve LN2, it increases with an increase in the engine speed. The threshold Ns ′ is the engine speed at the intersection P2 between the absorption torque curve D and the equal horsepower characteristic curve C1 shown in FIG.

In this case, in step S1 shown in FIG. 5, the engine speed is detected instead of the accelerator opening. In step S5, it is determined whether the engine speed is less than Ns'. Further, in steps S6, S8, and S9, torque limit values on the curves LN0, LN1, and LN2 corresponding to the engine speeds are acquired. For example, in steps S6, S8, and S9, the respective intersections of the engine speeds Ns ′, Ny1 ′, and Ny2 ′ with the equal horsepower torque limiting curve LN0, the running torque limiting characteristic curve LN1, and the working torque limiting characteristic curve LN2. The matching points Mx, My1, and My2 are obtained, and the torque limit values at this time are obtained.

An operation amount of the work vehicle, when processing the engine speed instead of the accelerator opening, the engine controller 107, as shown in FIG. 7, first, on the equal horsepower torque limit curve LN0 at idling engine speed N ₀ of It moves to the intersection P1, and then reaches the matching point along the torque limit curves TL1 and TL2. For example, when moving to matching points Mx, My1, My2 (engine speeds Ns ′, Ny1 ′, Ny2 ′), the paths X ′, Y1 ′, Y2 ′ shown in FIG.

Note that torque limit control using the accelerator opening and torque limit control using the engine speed may be combined. For example, as shown in FIG. 8, when the accelerator opening is less than Os (the engine speed is less than Ns ′), torque limit control using the accelerator opening is performed, and the accelerator opening is greater than or equal to Os (the engine speed is Ns ′ or higher), torque limit control using the engine speed is performed. In this case, when the accelerator opening is less than Os and the transition is made to the matching point Mx, the torque is limited by the torque limit value Tx of the matching point Mx and reaches the matching point Mx (path X ″), and the torque is limited by the accelerator opening. This is the same as the control, but when the accelerator opening is Os or more and the transition is made to the matching point My1, until the transition to the intersection My1 ″ between the torque limit value Ty1 of the matching point My1 and the equal horsepower torque limit curve LN0. After the intersection My1 ″, the transition is made to the matching point My1 along the equal horsepower torque control curve LN0 and the running torque limit characteristic curve LN1 after the intersection My1 ″. Arrive (path Y1 ″).

In the above-described embodiment, when the accelerator opening or the engine speed is less than the threshold, the engine output torque is limited according to the equal horsepower characteristic limit curve LN0, and the accelerator opening or the engine speed is equal to or greater than the threshold. When the working machine lever operation amount is less than or equal to the predetermined value, the engine output torque is limited according to the running torque limit characteristic curve LN1, and the accelerator opening or the engine speed is greater than or equal to the threshold value. When the operation amount exceeds a predetermined value, the engine output torque is limited according to the working torque limit characteristic curve LN2.

Therefore, when the accelerator opening degree or the engine speed is less than the threshold value, the torque is limited by the equal horsepower characteristic, so that the engine output torque can be lowered and the fuel consumption can be improved while maintaining the required acceleration. When the accelerator opening or the engine speed is equal to or greater than the threshold value and the work implement lever operation amount is equal to or less than a predetermined value, the traveling system torque limit characteristic curve LN1 is a limited torque curve that is equal to or greater than the traveling system absorption torque curve. Therefore, fuel consumption can be improved while ensuring the required running torque. Further, when the accelerator opening or the engine speed is equal to or greater than the threshold value and the working machine lever operation amount exceeds a predetermined value, the fuel consumption is ensured while ensuring sufficient working torque below the working torque limit characteristic curve LN2. Can be improved. In addition, in this case, since the matching point M2 is the maximum horsepower point, the maximum horsepower can be reliably obtained, and the work is not hindered.

Further, in this embodiment, when the accelerator opening degree or the engine speed is less than the threshold value, and when the accelerator opening degree or the engine speed is the threshold value or more and the work implement lever operation amount is not more than a predetermined value, that is, When it is considered that the work implement lever is not operated, the pump absorption torque is limited to the minimum, so the engine output is supplied with priority over the running torque. The fuel efficiency can be improved without impeding the running performance. In addition, when the accelerator opening or the engine speed is greater than or equal to the threshold value and the working machine lever operation amount exceeds a predetermined value, that is, when the working machine lever is operated, the limit to minimize the pump absorption torque Since the torque is released, fuel consumption can be improved while reliably obtaining the torque required for the work.

FIGS. 9 to 11 are diagrams respectively corresponding to FIGS. 4, 7, and 8 and are explanatory diagrams for explaining fuel consumption improvement according to the present embodiment. FIG. 9 shows the torque limit control using the accelerator opening, and the fuel efficiency corresponding to the region R1 is improved when shifting to the matching point My1 as compared to the case of passing through the conventional maximum torque line Tmax. The Further, FIG. 10 shows the time of torque limit control using the engine speed, and the fuel consumption corresponding to the region R2 is greater when the transition to the matching point My1 is made than when the conventional maximum torque line Tmax is passed. Improved. Further, FIG. 11 shows the time of torque limit control using a combination of the accelerator opening and the engine speed, and the fuel efficiency corresponding to the region R3 is improved as compared with the case of passing through the conventional maximum torque line Tmax. The The region R3 in FIG. 11 is larger than the regions R1 and R2, and further fuel economy is improved.

FIG. 12 is a diagram showing temporal changes in the accelerator opening, the engine speed, and the limit torque when the torque limit control according to the present embodiment is applied to the V shape work of the wheel loader. The V-shape work by the wheel loader is to move forward to the ground and excavate the earth and sand (W1), raise the boom after excavation and move backward (W2), move forward when reaching the direction change position (W3), Is a series of operations in which the waste is dumped into a hopper or dump truck and loaded (W4) through a V-shaped route. Here, L103 is a conventional output torque, and this conventional output torque has a portion exceeding the limit torque L102. In the present embodiment, since the torque limit is performed by the limit torque L102, in the case of this V-shaping work, the fuel consumption can be improved as compared with the conventional engine control.

The torque limit mode switch 112 described above is for selecting and instructing the torque limit mode when turned on. However, the torque limit mode is not limited to this, and is normally controlled in the torque limit mode, and is canceled when turned off. May be.

Further, the torque limit mode switch 112 is a mode in which the torque is limited only by the torque limit curve TL1 that is a combination of the equal horsepower torque limit curve LN0 and the running torque limit characteristic curve LN1, and the equal horsepower torque limit curve LN0 and the torque limit characteristic during work. There are a plurality of modes such as a mode in which torque is limited only by the torque limit curve TL2 combined with the curve LN2, and a mode in which the travel time torque limit characteristic curve LN1 and the work time torque limit characteristic curve LN2 are switched according to the work machine lever operation amount as described above. This mode may be selected and instructed.

In addition, when a plurality of different maximum torque lines Tmax are set depending on the mode, a torque limit mode corresponding to each of them may be provided. Further, when the maximum torque line Tmax itself has a normal work mode and an economy work mode in which torque is limited on the high engine speed side, the torque limit mode may be selected simultaneously with the selection of the economy work mode. The torque limit mode may be selectable when the economy work mode is selected.

Furthermore, although various operations such as excavation and loading are performed on the work vehicle, the torque limit mode may be automatically selected according to these various operations.

As mentioned above, although the embodiment to which the invention made by the present inventors was applied has been described, the present invention is not limited by the description and the drawings that form part of the disclosure of the present invention according to the above embodiment. For example, for the torque limit curve, only the speed stage of the transmission that can produce the maximum speed was described, but even if this control is applied only to the maximum speed stage, a torque limit curve is set for each speed stage. Thus, this control may be applied to each speed stage. Furthermore, even if the torque limit curves are different from each other so that a smoother acceleration / shifting feeling can be obtained, such as acceleration of a work vehicle to which the present invention is applied and when shifting from 2nd speed to 3rd speed. good. Further, the torque limit value has been described using an example of the numerical value of the engine output torque. However, the torque limit is limited by a ratio so that the maximum output torque value at the engine speed is 100% and the output torque is 80%. It may be a map. As described above, other embodiments, examples, operation techniques, and the like made by those skilled in the art based on the above-described embodiments are all included in the scope of the present invention.

In the above-described embodiment, the construction machine has been described as an example. However, in general work vehicles including an industrial vehicle such as a forklift and an agricultural machine such as a tractor that drives a traveling system and a work machine system with a common engine output. Can be applied.

1 Wheel loader 11 Engine 13 Torque converter (T / C)
DESCRIPTION OF SYMBOLS 11a Fuel injection apparatus 12 PTO mechanism 20 Hydraulic pump 20a Swash plate actuator 100 Engine control apparatus 101 Engine speed sensor 103 Speed stage sensor 104 Work implement lever sensor 105 Accelerator pedal sensor 106

Transmission controller

106a, 106b Map 107 Engine controller 108 Speed stage lever 109 Work implement lever 110 Accelerator pedal 111 Work implement controller 112 Torque limit mode switch

Claims

An operation amount detecting means for detecting an operation amount of the work vehicle;
Control means for limiting the output torque of the engine according to an equal horsepower characteristic curve that is a horsepower passing through the maximum output torque point during idling of the engine when the operation amount of the work vehicle detected by the operation amount detection means is less than a threshold value. When,
An engine control device for a work vehicle.
A torque limit mode switch for selecting and instructing engine output torque limit
In a state where the torque limit mode switch instructs the output torque limit and the operation amount of the work vehicle detected by the operation amount detection means is less than a threshold value, the control means is configured to output a maximum output torque during idle rotation of the engine. The engine control device for a work vehicle according to claim 1, wherein the engine output torque is limited according to an equal horsepower characteristic curve that is a horsepower passing through a point.
When the operation amount of the work vehicle detected by the operation amount detection means is greater than or equal to a threshold value in a state where the torque limit mode switch instructs the output torque limit, the control means and the absorption torque curve of the traveling system and the like In accordance with the running torque limit characteristic curve in which the limit torque gradually increases as the operation amount of the work vehicle increases from the intersection with the horsepower characteristic curve toward the matching point between the absorption torque curve and the maximum torque line of the traveling system. The engine control device for a work vehicle according to claim 2, wherein the output torque is limited.
The engine control apparatus for a work vehicle according to claim 3, wherein the running torque limit characteristic curve is a running absorption torque curve.
The operation amount detection means detects the operation device lever operation amount including the operation amount,
The control means is a case where the operation amount of the work vehicle detected by the operation amount detection means is greater than or equal to a threshold value in a state where the torque limit mode switch instructs output torque restriction, and the work implement lever operation amount Exceeds the predetermined value, the limit torque gradually increases as the operation amount of the work vehicle increases from the intersection of the absorption torque curve of the traveling system and the equal horsepower characteristic curve toward the maximum horsepower point on the maximum torque line. The engine control device for a work vehicle according to claim 2 or 3, wherein the output torque of the engine is limited according to a torque limitation characteristic curve during operation.
The control means limits a pump absorption torque of a work implement hydraulic pump when the work implement lever operation amount is equal to or less than the predetermined value in a state where the torque limit mode switch instructs an output torque limit. Item 6. The engine control device for a work vehicle according to Item 5.
The control means is a case where the operation amount of the work vehicle detected by the operation amount detection means is greater than or equal to a threshold value in a state where the torque limit mode switch instructs output torque restriction, and the work implement lever operation amount The engine control device for a work vehicle according to claim 6, wherein when the value exceeds the predetermined value, the restriction on the pump absorption torque of the work implement hydraulic pump is released.
The engine control device for a work vehicle according to claim 6, wherein the control means limits the pump absorption torque to a minimum.
The engine control device for a work vehicle according to claim 1, wherein the operation amount detection means detects an opening degree of an accelerator pedal as an operation amount of the work vehicle.
The engine control device for a work vehicle according to claim 1, wherein the operation amount detection means detects an engine speed as an operation amount of the work vehicle.
An operation amount detection step for detecting an operation amount of the work vehicle;
A control step of limiting the engine output torque according to an equal horsepower characteristic curve that is a horsepower passing through the maximum output torque point at the time of idling of the engine when the operation amount of the work vehicle detected by the operation amount detection step is less than a threshold value. When,
An engine control method for a work vehicle characterized by comprising:
Including an instruction determination step of determining whether or not the engine output torque limit selection instruction state;
In the control step, when the output torque limit is in a selection instruction state and the operation amount of the work vehicle detected by the operation amount detection step is less than a threshold, the horsepower passes through the maximum output torque point during idling of the engine. A control step for limiting the output torque of the engine in accordance with an equal horsepower characteristic curve;
The engine control method for a work vehicle according to claim 11, comprising:
In the control step, when the output torque limit is in a selection instruction state and the operation amount of the work vehicle detected by the operation amount detection step is equal to or greater than a threshold value, the intersection of the absorption torque curve of the traveling system and the equal horsepower characteristic curve The engine output torque is limited according to a running torque limit characteristic curve in which the limit torque gradually increases in accordance with an increase in the operation amount of the work vehicle toward the matching point between the absorption torque curve of the travel system and the maximum torque line. The engine control method for a work vehicle according to claim 12.
In the operation amount detection step, the operation machine lever operation amount is detected and detected.
The control step is a case where the output torque limit is in a selection instruction state, and the operation amount of the work vehicle detected by the operation amount detection step is equal to or greater than a threshold value, and the operation device lever operation amount exceeds a predetermined value. A torque limiting characteristic curve during operation in which the limiting torque gradually increases as the operation amount of the work vehicle increases from the intersection of the absorption torque curve of the traveling system and the equal horsepower characteristic curve toward the maximum horsepower point on the maximum torque line. The engine output torque of the work vehicle according to claim 12 or 13, wherein the output torque of the engine is limited according to the above.
15. The operation according to claim 14, wherein the control step limits the pump absorption torque of the work implement hydraulic pump when the output torque limit is in a selection instruction state and the work implement lever operation amount is equal to or less than the predetermined value. Vehicle engine control method.