Work vehicle, control device for work vehicle, and method for controlling work vehicle

Abstract

This accelerator correction unit acquires a corrected accelerator operation amount by correcting an accelerator operation amount on the basis of an inching operation amount. This target vehicle speed determination unit determines a target vehicle speed on the basis of the corrected accelerator operation amount and a signal based on operation of a transmission operation member.

Description

Technical Field

[0001] The present invention relates to a work vehicle, a control device for a work vehicle, and a control method for a work vehicle. This application claims priority to Japanese Patent Application No. 2019-072102 filed in Japan on April 4, 2019, the content of which is incorporated herein by reference.

Background Art

[0002] Work vehicles such as wheel loaders equipped with continuously variable transmissions are known. Examples of continuously variable transmissions include HST (Hydraulic Static Transmission) and HMT (Hydraulic Mechanical Transmission). Patent Document 1 discloses a technique for determining the target rotational speed of an engine of a work vehicle equipped with a continuously variable transmission based on the operation amount of an accelerator pedal and the operation amount of a work implement operation lever.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a work vehicle, work by a work implement and traveling may be performed simultaneously. At this time, in the work vehicle disclosed in Patent Document 1, by operating a work implement operation lever and an accelerator pedal, it is possible to perform work by the work implement while traveling. At this time, the operator operates the work implement operation lever with an operation amount corresponding to the desired operating speed of the work implement, and operates the accelerator pedal with an operation amount corresponding to the desired traveling speed.

[0005] On the other hand, in work vehicles equipped with a torque converter type transmission rather than a continuously variable transmission, the engine speed is determined by the operation of the accelerator pedal. Therefore, if the operator wants to accelerate the work implement while suppressing the acceleration of the work vehicle, they will suppress the acceleration of the work vehicle by pressing the accelerator pedal while also pressing the inching pedal.

[0006] Therefore, operators accustomed to torque converter type transmissions may find it unfamiliar to operate a work vehicle where the work implement accelerates based on the amount of movement of the work implement control lever. The object of the present invention is to provide a work vehicle that controls engine drive based on the amount of operation of the work equipment operating lever and the accelerator pedal, and that enables suppression of acceleration by operating the inching pedal, a control device for the work vehicle, and a control method for the work vehicle. [Means for solving the problem]

[0007] According to one aspect of the present invention, a control device for a work vehicle is a control device for a work vehicle that controls engine output based on an accelerator operation amount and a work machine operation amount, and comprises an accelerator correction unit that obtains a corrected accelerator operation amount by correcting the accelerator operation amount based on an inching operation amount, and a target vehicle speed determination unit that determines a target vehicle speed based on the corrected accelerator operation amount and a signal based on the operation of a gear shift operating member. [Effects of the Invention]

[0008] According to the above embodiment, the control device for the work vehicle can control the engine drive based on the amount of operation of the work implement operating lever and the accelerator pedal, and can suppress acceleration caused by the operation of the inching pedal. [Brief explanation of the drawing]

[0009] [Figure 1] This is a side view of a work vehicle according to the first embodiment. [Figure 2] This diagram shows the internal configuration of the driver's cab according to the first embodiment. [Figure 3]This is a schematic diagram showing the power system of a work vehicle according to the first embodiment. [Figure 4] This is a schematic block diagram showing the configuration of the control device for a work vehicle according to the first embodiment. [Figure 5] This is a flowchart showing a control method for a work vehicle according to the first embodiment. [Figure 6] This figure shows a method for correcting the accelerator operation amount according to the first embodiment. [Figure 7] This figure shows the method for determining the target vehicle speed according to the first embodiment. [Figure 8] This figure shows a method for correcting the target vehicle speed according to the first embodiment. [Figure 9] This figure shows the vehicle speed-horsepower characteristic relationship between the vehicle speed and target input horsepower of a work vehicle according to the first embodiment. [Figure 10] This figure shows a method for determining the target engine speed according to the first embodiment. [Modes for carrying out the invention]

[0010] <First Embodiment> The embodiments will be described in detail below with reference to the drawings. Figure 1 is a side view of a work vehicle according to the first embodiment. The work vehicle 100 according to the first embodiment is a wheel loader. The work vehicle 100 comprises a body 110, a work machine 120, a front wheel section 130, a rear wheel section 140, and a driver's cab 150.

[0011] The vehicle body 110 comprises a front vehicle body 111, a rear vehicle body 112, and a steering cylinder 113. The front vehicle body 111 and the rear vehicle body 112 are rotatably mounted around a steering axis that extends vertically through the vehicle body 110. The front wheel section 130 is located at the lower part of the front vehicle body 111, and the rear wheel section 140 is located at the lower part of the rear vehicle body 112. The steering cylinder 113 is a hydraulic cylinder. The base end portion of the steering cylinder 113 is attached to the rear vehicle body 112, and the tip end portion is attached to the front vehicle body 111. The steering cylinder 113 defines the angle formed between the front vehicle body 111 and the rear vehicle body 112 by expanding and contracting with hydraulic oil. That is, the steering angle of the front wheel portion 130 is defined by the expansion and contraction of the steering cylinder 113.

[0012] The working machine 120 is used for excavating and transporting work objects such as earth and sand. The working machine 120 is provided at the front portion of the vehicle body 110. The working machine 120 includes a boom 121, a bucket 122, a bell crank 123, a lift cylinder 124, and a bucket cylinder 125.

[0013] The base end portion of the boom 121 is attached to the front portion of the front vehicle body 111 via a pin. The bucket 122 includes a blade for excavating a work object and a container for transporting the excavated work object. The base end portion of the bucket 122 is attached to the tip end portion of the boom 121 via a pin. The bell crank 123 transmits the power of the bucket cylinder 125 to the bucket 122. The first end of the bell crank 123 is attached to the bottom of the bucket 122 via a link mechanism. The second end of the bell crank 123 is attached to the tip end portion of the bucket cylinder 125 via a pin.

[0014] The lift cylinder 124 is a hydraulic cylinder. The base end portion of the lift cylinder 124 is attached to the front portion of the front vehicle body 111. The tip end portion of the lift cylinder 124 is attached to the boom 121. When the lift cylinder 124 expands and contracts with hydraulic oil, the boom 121 is driven in the upward or downward direction. The bucket cylinder 125 is a hydraulic cylinder. The base end portion of the bucket cylinder 125 is attached to the front portion of the front vehicle body 111. The tip end portion of the bucket cylinder 125 is attached to the bucket 122 via the bell crank 123. When the bucket cylinder 125 expands and contracts with hydraulic oil, the bucket 122 is driven in the tilt direction or the dump direction.

[0015] The cab 150 is a space where an operator boards and operates the work vehicle 100. The cab 150 is provided on the upper part of the rear vehicle body 112. FIG. 2 is a top view showing the internal configuration of the cab according to the first embodiment. Inside the cab 150, a seat 151, an accelerator pedal 152, a brake pedal 153, an inching pedal 154, a steering wheel 155, a forward / reverse changeover switch 156, a shift switch 157, a boom lever 158, and a bucket lever 159 are provided. In the first embodiment, the brake pedal 153 and the inching pedal 154 are provided separately, but it is not limited thereto. For example, in other embodiments, the brake pedal 153 and the inching pedal 154 may be a single pedal that acts as the inching pedal 154 in a region where the depression amount is shallow and acts as the brake pedal 153 in a region where the depression amount is deep.

[0016] The accelerator pedal 152 is operated to set the driving force (tractive force) of the running generated in the work vehicle 100. The greater the operation amount of the accelerator pedal 152, the higher the target driving force (target tractive force) is set. The operation amount of the accelerator pedal 152 takes a value of 0% or more and 100% or less. The accelerator pedal 152 is an example of an accelerator operation member. The brake pedal 153 is operated to set the braking force of the running generated in the work vehicle 100. The greater the operation amount of the brake pedal 153, the stronger the braking force is set. It takes a value of 0% or more and 100% or less. The inching pedal 154 is operated to set the degree of reduction of the running driving force. It takes a value of 0% or more and 100% or less. The work vehicle 100 according to the first embodiment does not include a clutch in the transmission 230. The inching pedal 154 is an example of an inching operation member. The steering wheel 155 is operated to set the steering angle of the work vehicle 100. The forward / reverse selector switch 156 is operated to set the direction of travel of the work vehicle 100. The direction of travel of the work vehicle is one of forward (F), reverse (R), or neutral (N). The shift switch 157 is operated to set the speed range of the power transmission system. By operating the shift switch 157, one speed range is selected from, for example, 1st gear, 2nd gear, 3rd gear, and 4th gear. A signal indicating the speed range set by the shift switch 157 is generated. The shift switch 157 is an example of a gear shift operating member. The boom lever 158 is operated to set the speed of raising or lowering the boom 121. The boom lever 158 accepts a lowering operation when tilted forward and an raising operation when tilted backward. The bucket lever 159 is operated to set the speed of the dumping or tilting operation of the bucket 122. The bucket lever 159 accepts a dumping operation when tilted forward and a tilting operation when tilted backward. The boom lever 158 and bucket lever 159 are examples of implement operating members.

[0017] 《Power system》 Figure 3 is a schematic diagram showing the power system of a work vehicle according to the first embodiment. The work vehicle 100 is equipped with an engine 210, a PTO (Power Take Off) 220, a transmission 230, a front axle 240, a rear axle 250, a variable displacement pump 260, and a brake pump 270.

[0018] Engine 210 is, for example, a diesel engine. Engine 210 is equipped with a fuel injector 211. The fuel injector 211 controls the driving force of engine 210 by adjusting the amount of fuel injected into the cylinders of engine 210.

[0019] The PTO 220 transmits a portion of the driving force from the engine 210 to the variable displacement pump 260 and the brake pump 270. In other words, the PTO 220 distributes the driving force from the engine 210 to the transmission 230, the variable displacement pump 260, and the brake pump 270.

[0020] The transmission 230 is a continuously variable transmission equipped with an HST 231 (hydrostatic continuously variable transmission). The transmission 230 may perform gear shifting control solely by the HST 231, or it may be an HMT (hydraulic mechanical continuously variable transmission) that performs gear shifting control by a combination of the HST 231 and a planetary gear mechanism. The transmission 230 shifts the driving force input to the input shaft and outputs it from the output shaft. The input shaft of the transmission 230 is connected to the PTO 220, and the output shaft is connected to the front axle 240 and the rear axle 250. In other words, the transmission 230 transmits the driving force of the engine 210 distributed by the PTO 220 to the front axle 240 and the rear axle 250. A speedometer 232 is provided on the output shaft of the transmission 230. The speedometer 232 measures the vehicle speed of the work vehicle 100 by measuring the rotational speed of the output shaft.

[0021] The front axle 240 transmits the driving force output by the transmission 230 to the front wheel section 130. This causes the front wheel section 130 to rotate. The rear axle 250 transmits the driving force output by the transmission 230 to the rear wheel section 140. This causes the rear wheel section 140 to rotate.

[0022] The variable displacement pump 260 is driven by the power from the engine 210. The discharge capacity of the variable displacement pump 260 is changed, for example, by controlling the tilt angle of a swash plate located inside the variable displacement pump 260. The hydraulic fluid discharged from the variable displacement pump 260 is supplied to the lift cylinder 124 and the bucket cylinder 125 via the control valve 261, and to the steering cylinder 113 via the steering valve 262. The hydraulic fluid discharged from the variable displacement pump 260 is also discharged via the relief valve 266. The variable displacement pump 260 is an example of a pump for a work machine. The control valve 261 controls the flow rate of hydraulic fluid discharged from the variable displacement pump 260 and distributes the hydraulic fluid to the lift cylinder 124 and the bucket cylinder 125. The steering valve 262 controls the flow rate of hydraulic fluid supplied to the steering cylinder 113. The relief valve 266 releases pressure and discharges the hydraulic fluid when the hydraulic fluid pressure exceeds a predetermined relief pressure. In other embodiments, the variable displacement pump 260 may consist of multiple pumps, or other power sources, such as a hydraulically driven fan (not shown), may be provided instead of or in addition to the variable displacement pump 260.

[0023] The brake pump 270 is a fixed-displacement pump driven by the power from the engine 210. The hydraulic fluid discharged from the brake pump 270 is supplied to the brake valve 271. The brake valve 271 controls the pressure of the hydraulic fluid supplied to the brake cylinders (not shown) built into each axle. When hydraulic fluid is supplied to the brake cylinders, the brake discs, which rotate with the rotation axes of the front wheel section 130 and the rear wheel section 140, are pressed against a non-rotating plate, generating braking force.

[0024] Control device The work vehicle 100 is equipped with a control device 300 for controlling the work vehicle 100. The control device 300 outputs control signals to the fuel injection device 211, transmission 230, variable displacement pump 260, and control valve 261 according to the amount of operation of each control device in the driver's cab 150 (accelerator pedal 152, inching pedal 154, forward / reverse selector switch 156, shift switch 157, boom lever 158, bucket lever 159).

[0025] Figure 4 is a schematic block diagram showing the configuration of the control device for a work vehicle according to the first embodiment. The control device 300 is a computer comprising a processor 310, main memory 330, storage 350, and interface 370.

[0026] Storage 350 is a tangible, non-temporary storage medium. Examples of storage 350 include HDDs (Hard Disk Drives), SSDs (Solid State Drives), magnetic disks, magneto-optical disks, CD-ROMs (Compact Disc Read Only Memory), DVD-ROMs (Digital Versatile Disc Read Only Memory), and semiconductor memory. Storage 350 may be an internal medium directly connected to the bus of the control device 300, or an external medium connected to the control device 300 via the interface 370 or a communication line. Storage 350 stores a program for controlling the work vehicle 100.

[0027] The program may be for implementing a part of the functions to be performed by the control device 300. For example, the program may perform functions in combination with other programs already stored in storage, or in combination with other programs implemented in other devices. In other embodiments, the computer may include a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device) in addition to, or instead of, the above configuration. Examples of PLDs include PAL (Programmable Array Logic), GAL (Generic Array Logic), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Array). In this case, some or all of the functions implemented by the processor may be implemented by the integrated circuit.

[0028] If the program is delivered to the control device 300 via a communication line, the control device 300 that receives the program may load it into the main memory 330 and execute the above processing. Furthermore, the program may be intended to implement some of the functions described above. In addition, the program may be a so-called differential file (differential program) that implements the functions described above in combination with other programs already stored in the storage 350.

[0029] The processor 310, by executing a program, includes an operation variable acquisition unit 311, a measurement value acquisition unit 312, an accelerator correction unit 313, a target vehicle speed determination unit 314, a deceleration correction unit 315, a target horsepower determination unit 316, a target engine speed determination unit 317, an engine control unit 318, a transmission control unit 319, and a pump control unit 320.

[0030] The operation amount acquisition unit 311 acquires signals based on the operation of the accelerator pedal 152, inching pedal 154, forward / reverse selector switch 156, shift switch 157, boom lever 158, and bucket lever 159. Hereinafter, the amount of movement of the accelerator pedal 152 will also be referred to as the accelerator operation amount. The amount of movement of the inching pedal 154 will also be referred to as the inching operation amount. The switching position of the forward / reverse selector switch 156 will also be referred to as the direction operation amount. The switching position of the shift switch 157 will also be referred to as the shift operation amount. Furthermore, the amounts of movement of the boom lever 158 and the bucket lever 159 will be collectively referred to as the implement operation amount. The measurement value acquisition unit 312 acquires the measured value of the vehicle speed from the vehicle speedometer 232.

[0031] The accelerator correction unit 313 corrects the accelerator operation amount based on the inching operation amount. Hereinafter, the corrected accelerator operation amount will also be referred to as the corrected accelerator operation amount. The corrected accelerator operation amount becomes smaller as the inching operation amount increases.

[0032] The target vehicle speed determination unit 314 determines the target vehicle speed based on the corrected accelerator operation amount, the directional operation amount, and the measured vehicle speed. The deceleration correction unit 315 corrects the target vehicle speed determined by the target vehicle speed determination unit 314 based on the inching operation amount. Hereinafter, the corrected target vehicle speed will also be called the corrected target vehicle speed. The corrected target vehicle speed approaches zero as the inching operation amount increases. In other words, the absolute value of the corrected target vehicle speed decreases as the inching operation amount increases.

[0033] The target horsepower determination unit 316 determines the target input horsepower to the HST231 based on the corrected accelerator operation amount, corrected target vehicle speed, shift operation amount, and measured vehicle speed, so that driving performance corresponding to the accelerator operation amount can be obtained.

[0034] The target engine speed determination unit 317 determines the target engine speed based on the target input horsepower, the amount of work implement operation, the corrected target vehicle speed, and the amount of accelerator operation. Specifically, the target engine speed determination unit 317 determines the target engine speed to be the largest of the following: the engine speed required to achieve the target input horsepower, the engine speed required to achieve work implement operation according to the amount of work implement operation, the minimum engine speed required to travel at the corrected target vehicle speed, and the engine speed according to the amount of accelerator operation.

[0035] The engine control unit 318 outputs a control command to the fuel injection device 211 so that the engine 210 is driven at the target engine speed determined by the target engine speed determination unit 317. The transmission control unit 319 outputs a control command to the transmission 230 so that the work vehicle 100 travels at the corrected target vehicle speed, based on the corrected target vehicle speed and target engine speed. The pump control unit 320 outputs a control command for the variable displacement pump 260 based on the amount of work machine operation, so that the work machine 120 can be operated according to the amount of work machine operation. In other embodiments, the variable displacement pump 260 may be controlled by hydraulics. In this case, the control device 300 does not need to include the pump control unit 320.

[0036] Control methods for work vehicles Figure 5 is a flowchart showing the control method for a work vehicle according to the first embodiment. In the following description, the control when the work vehicle 100 is moving forward (direction control amount F) will be described. The same control may be performed when the work vehicle 100 is moving backward (direction control amount R).

[0037] First, the operation amount acquisition unit 311 acquires the operation amount from the accelerator pedal 152, brake pedal 153, inching pedal 154, steering wheel 155, forward / reverse selector switch 156, shift switch 157, boom lever 158, and bucket lever 159 (step S1). In addition, the measurement value acquisition unit 312 acquires the vehicle speed measurement value from the vehicle speedometer 232 (step S2).

[0038] Accelerator input correction Next, the accelerator correction unit 313 corrects the accelerator operation amount AC based on the inching operation amount IN to obtain a corrected accelerator operation amount AC' (step S3). Here, a specific method for correcting the accelerator operation amount AC will be described. Figure 6 is a diagram showing the accelerator operation amount correction method according to the first embodiment.

[0039] The accelerator correction unit 313 determines the accelerator correction amount CR based on the inching operation amount IN acquired in step S1 (step S101). The accelerator correction amount CR takes a value between -100% and 0%. The accelerator correction amount CR decreases monotonically with respect to the inching operation amount IN. In this embodiment, "monotonically decreasing" means that when one value increases, the other value always decreases or remains unchanged (monotonically non-increasing). Similarly, "monotonically increasing" means that when one value increases, the other value always increases or remains unchanged (monotonically non-decreasing). When the inching operation amount is between 0% and a predetermined play operation amount, the accelerator correction amount becomes 0%.

[0040] The accelerator correction unit 313 adds the correction amount CR determined in step S101 to the accelerator operation amount AC obtained in step S1 (step S102). Since the correction amount CR determined in step S101 is a value of 0% or less, the value obtained by adding the correction amount CR to the accelerator operation amount AC will be less than or equal to the accelerator operation amount AC. The accelerator correction unit 313 determines the corrected accelerator operation amount AC' to be the larger of the value obtained in step S102 and 0% (step S103).

[0041] Determining the target vehicle speed Next, the target vehicle speed determination unit 314 determines the target vehicle speed Vt based on the corrected accelerator operation amount AC', the shift operation amount SH, and the measured value of the vehicle speed V (step S4). Here, a specific method for determining the target vehicle speed Vt will be described. Figure 7 is a diagram showing the method for determining the target vehicle speed according to the first embodiment.

[0042] The target vehicle speed determination unit 314 determines the target reference vehicle speed Vt_ref from the corrected accelerator operation amount AC' obtained in step S3 and the shift operation amount SH obtained by the operation amount acquisition unit 311 (step S201). The target reference vehicle speed Vt_ref is the vehicle speed set as the target target vehicle speed when the work vehicle 100 is traveling on level ground. The target reference vehicle speed Vt_ref increases monotonically with respect to the corrected accelerator operation amount. The relationship between the corrected accelerator operation amount AC' and the target reference vehicle speed Vt_ref is defined separately for each shift operation amount SH by the target vehicle speed determination unit 314. Even if the corrected accelerator operation amount AC' is the same, the higher the value of the shift operation amount SH, the greater the target reference vehicle speed Vt_ref increases.

[0043] Next, the target vehicle speed determination unit 314 calculates the vehicle speed deviation Ds by subtracting the target reference vehicle speed Vt_ref calculated in step S201 from the measured vehicle speed V obtained in step S2 (step S202). A negative vehicle speed deviation Ds means that the work vehicle 100 is accelerating. A positive vehicle speed deviation Ds means that the work vehicle 100 is decelerating. Next, the target vehicle speed determination unit 314 calculates the target acceleration based on the vehicle speed deviation Ds calculated in step S202 and the corrected accelerator operation amount AC' obtained in step S3 (step S203). The target acceleration decreases monotonically with respect to the vehicle speed deviation Ds and increases monotonically with respect to the corrected accelerator operation amount AC'. Next, the target vehicle speed determination unit 314 calculates the target speed change amount by multiplying the target acceleration calculated in step S203 by the time Δt related to the control cycle of the control device 300 (step S204).

[0044] The target vehicle speed determination unit 314 adds the target speed change amount calculated in step S204 to the measured vehicle speed V obtained in step S2 (step S205). The target vehicle speed determination unit 314 determines whether the vehicle speed deviation Ds calculated in step S202 is greater than 0 (step S206). If the vehicle speed deviation Ds is 0 or less, i.e., the work vehicle 100 is accelerating, the target vehicle speed determination unit 314 determines the target vehicle speed Vt to be the smallest of the target reference vehicle speed Vt_ref calculated in step S201 and the speed calculated in step S205 (step S207). On the other hand, if the vehicle speed deviation Ds is greater than 0, i.e., the work vehicle 100 is decelerating, the target vehicle speed determination unit 314 determines the target vehicle speed Vt to be the largest of the target reference vehicle speed Vt_ref calculated in step S201 and the speed calculated in step S205 (step S208). The target vehicle speed determination unit 314 sets the target vehicle speed Vt to 0 if the target vehicle speed Vt is negative.

[0045] Correction of target vehicle speed Next, the deceleration correction unit 315 corrects the target vehicle speed Vt determined in step S4 based on the inching operation amount IN to obtain a corrected target vehicle speed Vt' (step S5). Here, a specific method for determining the corrected target vehicle speed Vt' will be explained. Figure 8 is a diagram showing the method for correcting the target vehicle speed according to the first embodiment.

[0046] The deceleration correction unit 315 determines whether the target vehicle speed Vt calculated in step S4 is greater than the target reference vehicle speed Vt_ref (step S301). If the target vehicle speed Vt is less than or equal to the target reference vehicle speed Vt_ref, the deceleration correction unit 315 does not correct the target vehicle speed Vt. For convenience, even if the target vehicle speed is not corrected, the target vehicle speed output by the deceleration correction unit 315 will be called the corrected target vehicle speed Vt'.

[0047] On the other hand, if the target vehicle speed Vt is greater than the target reference vehicle speed Vt_ref, the deceleration correction unit 315 determines the inching ratio IR based on the inching operation amount IN obtained in step S1 (step S302). The inching ratio IR is greater than 0 and less than or equal to 1. The inching ratio IR decreases monotonically with respect to the inching operation amount IN. Note that if the inching operation amount is between 0% and a predetermined play operation amount, the inching ratio IR becomes 1. The deceleration correction unit 315 multiplies the target vehicle speed Vt calculated in step S4 by the inching ratio IR determined in step S302 (step S303). Then, the deceleration correction unit 315 determines the corrected target vehicle speed Vt' to be the largest of the target reference vehicle speed Vt_ref calculated in step S4 and the speed calculated in step S303 (step S304).

[0048] Determining the target input horsepower Next, the target horsepower determination unit 316 determines the target input horsepower Pt to the HST231 based on the corrected accelerator operation amount AC' and the corrected target vehicle speed Vt' (step S6). Figure 9 is a diagram showing the vehicle speed-horsepower characteristics that represent the relationship between the corrected target vehicle speed and the target input horsepower of a work vehicle according to the first embodiment. Figure 9 illustrates the vehicle speed-horsepower characteristics H100 when the corrected accelerator operation amount AC' is 100%, the vehicle speed-horsepower characteristics H80 when the corrected accelerator operation amount AC' is 80%, and the vehicle speed-horsepower characteristics H60 when the corrected accelerator operation amount AC' is 60%. As shown in Figure 9, regardless of the corrected accelerator input AC', the vehicle speed-horsepower characteristic has two inflection points p1 and p2. In the low-speed region R_low, where the corrected target vehicle speed is greater than or equal to zero and less than inflection point p1, the target input horsepower Pt increases monotonically with respect to the corrected target vehicle speed Vt'. In the medium-speed region R_mid, where the corrected target vehicle speed is greater than or equal to inflection point p1 and less than inflection point p2, the target input horsepower Pt remains constant regardless of the corrected target vehicle speed Vt'. In the high-speed region R_high, where the vehicle speed is greater than or equal to inflection point p2, the target input horsepower Pt decreases monotonically with respect to the corrected target vehicle speed Vt'. The target horsepower determination unit 316 determines the target input horsepower Pt from the corrected target vehicle speed Vt' based on the vehicle speed-horsepower characteristics identified from the corrected accelerator operation amount AC'.

[0049] Determining the target engine speed Next, the target engine speed determination unit 317 determines the target engine speed Nt based on the accelerator operation amount AC and work implement operation amount WI acquired in step S1, the corrected target vehicle speed Vt' determined in step S5, and the target input horsepower Pt determined in step S6 (step S7). Here, a specific method for determining the target engine speed Nt will be described. Figure 10 is a diagram showing the method for determining the target engine speed according to the first embodiment.

[0050] The target engine speed determination unit 317 determines the engine speed Nt_HST required to achieve the target input horsepower Pt from the target input horsepower Pt determined in step S6 (step S401). The target engine speed determination unit 317 determines the engine speed Nt_HST required to achieve the target input horsepower Pt such that the torque of the engine 210 and the absorbed torque of the HST 231 coincide at a predetermined matching point MP on the equihorsepower line corresponding to the target input horsepower Pt. In this embodiment, for the sake of simplicity of explanation, the absorbed torque of the HST 231 will be described without considering the shifting of the PTO 220.

[0051] The target engine speed determination unit 317 determines the engine speed Nt_WI required to operate the work implement 120 according to the work implement operation amount WI obtained in step S1 (step S402). The engine speed Nt_WI increases monotonically with respect to the work implement operation amount WI.

[0052] The target engine speed determination unit 317 determines the minimum engine speed Nt_V required for driving at the corrected target vehicle speed from the corrected target vehicle speed Vt' determined in step S5 (step S403). The target engine speed determination unit 317 determines the target engine speed for vehicle speed as a value obtained by multiplying the corrected target vehicle speed Vt' by a predetermined conversion coefficient c and the minimum transmission gear ratio R_tm. The conversion coefficient c is a coefficient for converting the corrected target vehicle speed Vt' to the rotational speed of the output shaft of the transmission 230. The conversion coefficient c may take into account the shifting at the PTO 220. The minimum transmission gear ratio R_tm is the minimum gear ratio of the transmission 230. The minimum transmission gear ratio R_tm corresponds to the input speed / output speed ratio when the transmission 230 is shifted to the highest speed within a predetermined shifting range.

[0053] The target engine speed determination unit 317 determines an engine speed Nt_AC that increases monotonically with respect to the accelerator operation amount AC, based on the accelerator operation amount AC obtained in step S1 (step S404).

[0054] The target engine speed determination unit 317 determines the target engine speed Nt as the largest of the engine speeds Nt_HST determined in step S401, Nt_WI determined in step S402, Nt_V determined in step S403, and Nt_AC determined in step S404 (step S405).

[0055] The engine control unit 318 outputs a control command to the fuel injector 211 so that the engine 210 is driven at the target engine speed Nt determined in step S7 (step S8). The transmission control unit 319 outputs a control command to the transmission 230 so that the work vehicle 100 is driven at the corrected target vehicle speed Vt' determined in step S5 and the target engine speed Nt determined in step S7 (step S9). The pump control unit 320 outputs a control command to the variable displacement pump 260 based on the work machine operation amount WI acquired in step S1 (step S10).

[0056] Action / Effect Thus, according to the first embodiment, the control device 300 corrects the accelerator operation amount based on the inching operation amount and determines the target vehicle speed based on the corrected accelerator operation amount and the shift operation amount. As a result, when an operator operates the accelerator pedal 152 and the inching pedal 154, as in the operation of a work vehicle with a torque converter type transmission, the control device 300 can suppress acceleration caused by the operation of the inching pedal 154. Therefore, the control device 300 can reduce the sense of unfamiliarity with operating the work vehicle 100 by an operator who is accustomed to a torque converter type transmission.

[0057] Furthermore, according to the first embodiment, the control device 300 further corrects the target vehicle speed based on the inching operation amount. When the inching pedal 154 is operated, the operator is highly likely to intend to actively decelerate the work vehicle 100. Therefore, by correcting the target vehicle speed based on the inching operation amount, the control device 300 can achieve a stronger braking force compared to simply releasing the accelerator pedal 152. In other embodiments, however, the control device 300 may not need to correct the target vehicle speed.

[0058] Furthermore, according to the first embodiment, the control device 300 determines the target engine speed based on the uncorrected accelerator operation amount and the work implement operation amount. The larger the inching operation amount, the closer the corrected accelerator operation amount and the corrected target vehicle speed approach zero. That is, the larger the inching operation amount, the smaller the absolute values ​​of the corrected accelerator operation amount and the corrected target vehicle speed become. Therefore, if the target engine speed is determined based on the corrected accelerator operation amount or the corrected target vehicle speed, the operator may feel that the engine speed of 210 is low in relation to the depression of the accelerator pedal 152. In contrast, according to the first embodiment, the control device 300 determines the target engine speed based on the uncorrected accelerator operation amount, thereby realizing engine speed 210 rotation in accordance with the depression of the accelerator pedal 152, and thus reducing the feeling of discomfort with the operation of the accelerator pedal 152. Note that the control device 300 according to other embodiments may determine the target engine speed without using the uncorrected accelerator operation amount.

[0059] Although one embodiment has been described in detail with reference to the drawings above, the specific configuration is not limited to that described above, and various design changes are possible. The work vehicle 100 according to the above embodiment is a wheel loader, but is not limited to this. For example, the work vehicle 100 according to other embodiments may be other work vehicles such as a dump truck, a motor grader, or a bulldozer. Furthermore, in other embodiments, the order of the above-described processes may be changed as appropriate. Also, some processes may be executed in parallel. [Industrial applicability]

[0060] According to the above disclosure of the present invention, the control device for a work vehicle can control engine drive based on the amount of operation of the work equipment operating lever and the accelerator pedal, and can suppress acceleration caused by the operation of the inching pedal. [Explanation of Symbols]

[0061] 100…Work vehicle 110…Body 111…Front body 112…Rear body 113…Steering cylinder 120…Work implement 121…Boom 122…Bucket 123…Bell crank 124…Lift cylinder 125…Bucket cylinder 130…Front wheel section 140…Rear wheel section 150…Driver's cab 151…Seat 152…Accelerator pedal 153…Brake pedal 154…Inching pedal 155…Steering wheel 156…Forward / reverse selector switch 157…Shift switch 158…Boom lever 159…Bucket lever 210…Engine 211…Fuel injection system 220…PTO 230…Transmission 231…HST 232…Speedometer 240…Front axle 250…Rear axle 260…Variable displacement pump 261…Control valve 262...Steering valve 266...Relief valve 270...Brake pump 271...Brake valve 300...Control unit 310...Processor 330...Main memory 350...Storage 370...Interface 311...Operational input acquisition unit 312...Measurement value acquisition unit 313...Accelerator correction unit 314...Target vehicle speed determination unit 315...Deceleration correction unit 316...Target horsepower determination unit 317...Target engine speed determination unit 318...Engine control unit 319...Transmission control unit 320...Pump control unit

Claims

1. An accelerator correction unit that obtains a corrected accelerator operation amount by adding a negative correction amount obtained from the inching operation amount to the accelerator operation amount, A target vehicle speed determination unit that determines the target vehicle speed based on the corrected accelerator operation amount and the signal based on the operation of the gear shift operating member, A deceleration correction unit obtains a corrected target vehicle speed by correcting the target vehicle speed based on the inching operation amount, Based on the corrected accelerator operation amount and the corrected target vehicle speed, the engine control unit outputs a control command to the fuel injection device. A control device for a work vehicle equipped with the following features.

2. A target horsepower determination unit that determines a target input horsepower to the transmission based on the corrected accelerator operation amount and the corrected target vehicle speed, A target engine speed determination unit determines the largest of the following as the target engine speed: the engine speed required to achieve the target input horsepower, the minimum engine speed required to drive at the corrected target vehicle speed, the engine speed corresponding to the accelerator operation amount, and the engine speed required to achieve the work equipment operation according to the work equipment operation amount. Equipped with, The engine control unit outputs the control command to the fuel injection device so that the engine is driven at the target engine speed. A control device for a work vehicle according to claim 1.

3. The engine and A transmission that changes the output of the aforementioned engine, A pump for a work machine driven by the aforementioned engine, A work machine driven by hydraulic fluid discharged from the aforementioned work machine pump, Accelerator operating member and Inching operating member and Gear shifting operating member, A work machine operating component, The control device according to claim 1 or claim 2 and A work vehicle equipped with the following features.

4. A step of obtaining a corrected accelerator operation amount by adding a negative correction amount obtained from the inching operation amount to the accelerator operation amount, The steps include determining a target vehicle speed based on the corrected accelerator operation amount and a signal based on the operation of the gear shift operating member, The steps include obtaining a corrected target vehicle speed by correcting the target vehicle speed based on the inching operation amount, The steps include outputting a control command to the fuel injection device based on the corrected accelerator operation amount and the corrected target vehicle speed, and A control method for a work vehicle equipped with the following features.

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