Work vehicles

Abstract

To provide a work vehicle configured so that electric power generated when the vehicle is braked is adjusted in accordance with a state of an engine, which can supply power from the engine more smoothly when the vehicle is braked and the started, in modulate operation.SOLUTION: A work vehicle is equipped with an electric motor for running that makes a vehicle body run by electric power from an electricity generator that is driven by an engine, a forward / backward running-switching switch, and an external resistor that consumes regenerative electric power from the electric motor for running, which when a running direction of the vehicle body shown by the forward / backward running-switching switch is different from a running direction of the vehicle body shown by a rotating direction of the electric motor for running, controls the electric power generator so that electric power generated by the electricity generator increases, when a difference between a preset fuel injection limit value and a fuel injection volume which are preset for the engine is larger than a first threshold, and controls the electricity generator so that electric power generated by the electricity generator decreases, when the difference between fuel injection limit value and the fuel injection amount is smaller than the first threshold.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a work vehicle.

Background Art

[0002] Some work vehicles drive a motor generator with an engine to generate electricity, and use the power from the motor generator to rotationally drive wheels with a traveling motor. For example, in Patent Document 1, there are a power generation motor electrically connected to an engine, a power generation inverter that controls the power generation amount of the power generation motor based on a power generation voltage command, a traveling motor that drives a vehicle body, a traveling inverter that controls the torque of the traveling motor based on a motor torque command, a forward / backward switching device that switches the forward / backward movement of the vehicle body, a brake resistor, and a chopper circuit that is electrically connected to the power generation inverter and the traveling inverter and consumes the power generated by the power generation motor and the traveling motor by electrically connecting the power generation inverter and the traveling inverter to the brake resistor when the input voltage exceeds a set voltage. Also disclosed is an electric drive type work vehicle that outputs a power generation voltage command for driving the power generation motor with the engine to generate a voltage exceeding the set voltage to the power generation inverter while the electric drive type work vehicle performs a modulation operation when the forward / backward switching device selects a direction opposite to the traveling direction of the vehicle body.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] One example of a work vehicle is a wheel loader, which excavates and transports soil and other materials using the bucket section of a hydraulic work device at the front of the vehicle while it is moving, and then loads them onto dump trucks or other vehicles. For wheel loaders, work efficiency, such as the amount of material transported per unit time, is one indicator of the vehicle's performance. To improve the work efficiency of a wheel loader, it is necessary to move the vehicle as quickly as possible and perform the work quickly.

[0005] For example, one of the operations performed by a wheel loader during work is known as modulated motion, which involves suddenly braking, then switching the direction of travel in the opposite direction and accelerating rapidly when moving between an excavation position and a loading position.

[0006] In the conventional technology described above, power generation is performed during modulo operation without considering the engine state. As a result, when the vehicle starts moving after braking, the engine output may become excessive, causing the engine speed to decrease and potentially preventing a smooth start. Furthermore, if the generated power is reduced to avoid a decrease in engine speed, it may take time to supply the power necessary for starting the vehicle, resulting in a delayed start.

[0007] The present invention has been made in view of the above, and aims to provide a work vehicle that can supply power from the engine more smoothly when starting after braking by adjusting the generated power during vehicle braking in accordance with the engine state during modulated operation. [Means for solving the problem]

[0008] The present invention includes several means for solving the above problems, but to give one example, in a work vehicle comprising a generator driven by an engine, a traction motor that drives the vehicle body using electricity from the generator, a forward / reverse switch for switching the direction of travel of the vehicle body between forward and reverse, an external resistor that consumes regenerative power from the traction motor, and a vehicle control device, the vehicle control device shall, when there is a difference between the direction of travel of the vehicle body indicated by the forward / reverse switch and the direction of travel of the vehicle body indicated by the rotation direction of the traction motor, perform a preset fuel injection for the engine above The generator's output power shall be controlled to increase or decrease based on the difference between the limit value and the fuel injection amount. [Effects of the Invention]

[0009] According to the present invention, in modulated operation, the generated power during vehicle braking is adjusted according to the engine state, thereby enabling a smoother supply of power from the engine when starting after braking. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic side view showing the external appearance of a wheel loader. [Figure 2] This diagram schematically shows the configuration of the electric drive system for a wheel loader. [Figure 3] This figure shows an example of how a wheel loader operates. [Figure 4] This diagram schematically illustrates the flow of electricity in fuel efficiency improvement control. [Figure 5] This diagram schematically illustrates the power flow in a control system designed to improve work efficiency. [Figure 6] This is a functional block diagram showing the processing details in the controller function unit of a generator inverter. [Figure 7] This is a functional block diagram showing the functional parts related to the control of the power drive system of a vehicle control device. [Figure 8]It is a flowchart showing the processing contents of the modulation determination unit and the MG control mode switching unit of the vehicle control device. [Figure 9] It is a functional block diagram showing the processing contents in the power generation amount calculation unit of the vehicle control device. [Figure 10] It is a diagram showing the state quantities of each part during the modulation operation in the prior art shown as a comparative example. [Figure 11] It is a diagram showing the state quantities of each part during the modulation operation. [Figure 12] It is a functional block diagram showing the processing contents of the regenerative power limit processing.

Mode for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 12.

[0012] In the following description, a wheel loader is exemplified as an example of a work vehicle, but the present invention is not limited to this, and the present invention can also be applied to other work machines adopting a so-called diesel-electric type.

[0013] FIG. 1 is a side view schematically showing the appearance of the wheel loader according to the present embodiment. In the following description, unless otherwise specified, the front, rear, left, and right of the wheel loader are based on the viewpoint of an operator who rides on the wheel loader and operates it.

[0014] In FIG. 1, the wheel loader 100 is composed of a front frame 102 arranged in the front (left direction in FIG. 1) constituting the vehicle body and a rear frame 103 arranged in the rear (right direction in FIG. 1). The front frame 102 and the rear frame 103 are connected by a center pin 109 so as to be rotatable in the left-right direction.

[0015] The front frame 102 is equipped with a pair of left and right lift arms 108 whose proximal ends are connected to the front frame 102 so as to be rotatable in the vertical direction, a bucket 107 whose distal end is connected to the distal ends of the lift arms 108 so as to be rotatable in the vertical direction, and a pair of left and right wheels (front wheels 11a, 11b). The lift arms 108 and the bucket 107, together with a lift cylinder 52, a bucket cylinder 51, etc., constitute a hydraulic working device 5 for the front portion that performs excavation work such as earth and sand.

[0016] The lift arm 108 and the front frame 102 are connected by a lift cylinder 52. When the lift cylinder 52 expands and contracts, the lift arm 108 is rotated integrally with the bucket 107 in the vertical direction.

[0017] The bucket 107 and the lift arm 108 are connected by a bucket cylinder 51. When the bucket cylinder 51 expands and contracts, the bucket 107 is rotated in the vertical direction.

[0018] The rear frame 103 is equipped with a cab 104 on which an operator rides and a pair of left and right wheels (rear wheels 12a, 12b). Inside the cab 104, a forward and reverse switching switch 104a for switching the traveling direction of the wheel loader between forward and reverse is arranged.

[0019] The front frame 102 and the rear frame 103 are connected by a pair of left and right steering cylinders 53. By extending one of the pair of left and right steering cylinders 53 and retracting the other simultaneously, the front frame 2 and the rear frame 3 are bent in the left - right direction around the center pin 109.

[0020] Figure 2 is a diagram schematically showing the configuration of the electric drive system of the wheel loader.

[0021] In Figure 2, the electric drive system is roughly composed of a generator 6 (motor generator: MG) connected to the output shaft of an engine 1 (e.g., a diesel engine) located on the rear frame 103 and driven by the engine 1, a generator inverter 7 that controls the operation of the generator 6, a drive motor 9 that uses the power from the generator 6 to rotate and drive the propeller shaft 8 related to the drive of the wheel loader 100 with the propeller shaft as its output shaft, a drive motor inverter 10 that controls the operation of the drive motor 9 by controlling the power supplied from the generator 6 to the drive motor 9 via the generator inverter 7, an external resistor 14 for consuming regenerative power from the drive motor 9, and a vehicle control device 15 that controls the overall operation of the electric drive system.

[0022] A hydraulic pump 4, driven by engine 1, is connected to the output shaft of engine 1. By controlling the flow rate and direction of the pressurized oil discharged from the hydraulic pump 4 with a control valve 50, the extension and retraction of the bucket cylinder 51, lift cylinder 52, and steering cylinder 53 are controlled.

[0023] The propeller shaft 8, which is rotationally driven by the drive motor 9, has the front wheels 11a and 11b attached to it via a center joint 13 (CJ), differential gear 11e (Dif), and gears 11c and 11d, and the rear wheels 12a and 12b attached via a differential gear 12e (Dif), and gears 12c and 12d (G).

[0024] In the electric drive system of this embodiment, the engine 1 drives the generator 6, and the power generated by the generator 6 is used as input to generate torque in the travel motor 9, which is transmitted to the wheels 11a, 11b, 12a, and 12b via the propeller shaft 8, etc., thereby rotating and driving the wheel loader 100. At this time, the voltage of the DC coupling section (i.e., the DC bus voltage) that electrically connects the generator inverter 7 that controls the generator 6 and the travel motor inverter 10 that controls the travel motor 9 is controlled.

[0025] Here, we will explain the basic operation of the wheel loader 100 at the work site.

[0026] Figure 3 shows an example of the operation of a wheel loader.

[0027] As shown in Figure 3, the basic operation of a wheel loader is called V-shaped excavation. In V-shaped excavation, the wheel loader 100 first moves forward towards the object to be excavated, such as a pile of soil, and loads the material to be transported, such as soil, into the bucket 107 by inserting the hydraulic work device 5 into the object to be excavated 200. After that, it reverses to return to its original position and moves forward towards a transport vehicle such as a dump truck 300 while operating the steering and raising the bucket 107 of the hydraulic work device 5. After loading the transport material onto the transport vehicle (discharging the soil from the bucket 107), it reverses again and returns to its original position. In this way, the basic operation of the wheel loader 100 is called V-shaped excavation because it repeats this operation while drawing a V-shaped trajectory, and it is the operation that accounts for the majority of the wheel loader 100's working time. The operation in which the wheel loader 100 suddenly brakes and then reverses direction and suddenly accelerates when moving between the excavation position and the loading position is called modulated operation.

[0028] One of the basic performance indicators for the wheel loader 100 in V-shaped excavation work is work efficiency [t / h] (where t is the weight of the material being transported and h is the working time). To improve work efficiency [t / h] in V-shaped excavation work, one could increase the amount of soil and other materials [t] loaded into the bucket 107, or improve the driving performance during operation to shorten the working time [t].

[0029] In this embodiment, the aim is to improve work efficiency [t / h] by shortening the work time [t]. The shortening of the work time [t] for V-shaped excavation work by the wheel loader 100 can be achieved, for example, by performing a rapid transition from reverse to forward (modulation operation). Specifically, when the wheel loader 100 is in a state of sudden braking from a reverse state (for example, a full brake state in the reverse state), the direction of travel instruction signal (FNR signal) from the forward / reverse selector switch 104a is switched to the direction of travel (i.e., the forward / reverse selector switch 104a is switched to forward), and the work time [t] can be shortened by transitioning to a rapid start in the forward direction. Hereafter, this type of control will be referred to as work efficiency improvement control.

[0030] Another basic performance indicator for the wheel loader 100 in V-shaped excavation work is the ratio of the weight of the transported material to the fuel consumption (so-called fuel efficiency). To improve fuel efficiency in V-shaped excavation work, it is conceivable to efficiently generate electricity using the generator 6. Specifically, fuel efficiency can be improved by not generating electricity with the generator 6 during braking, when regenerative power is generated by the travel motor 9 and consumed by the external resistor 14. Hereafter, this type of control will be referred to as fuel efficiency improvement control.

[0031] In this embodiment, a control ON / OFF switch 104b is provided inside the cab 104 to switch between enabling and disabling the work efficiency improvement control. When the control ON / OFF switch 104b is ON, work efficiency improvement control is performed, and when it is OFF, fuel efficiency improvement control is performed. That is, when prioritizing the work efficiency of the work performed by the wheel loader 100, the operator turns the control ON / OFF switch 104b ON and performs the work. Also, when the work performed by the wheel loader 100 is time-considered, the operator turns the control ON / OFF switch 104b OFF and performs the work, taking fuel efficiency into consideration.

[0032] Figure 4 schematically illustrates the power flow in fuel efficiency control, showing the regenerative power flow during braking in the modulated operation of V-shaped excavation work. Note that some components have been added or omitted in Figure 4 for the sake of simplicity.

[0033] As shown in Figure 4, in the fuel efficiency improvement control, during braking in modulated operation, a braking force is applied to the drive motor 9 from the wheel side, and the drive motor 9 generates electricity due to the braking force. The power generated from the drive motor 9 (regenerative power) is consumed by the external resistor 14 and by rotating the generator 6 (motoring). At this time, the rotation of the generator 6 rotates the output shaft of the engine 1, so the rotation of the output shaft of the engine 1 increases, and as a result the engine 1 suspends fuel injection during that time. In the case of modulated operation, that is, when transitioning from sudden braking to sudden acceleration, the engine 1 has suspended fuel injection, so it is not possible to immediately produce a large engine output and accelerate suddenly. In other words, the effect of shortening the time required for modulated operation is not obtained, and therefore no improvement in work efficiency [t / h] is expected, but the deterioration of fuel efficiency is expected to be suppressed.

[0034] Figure 5 schematically illustrates the power flow in the work efficiency improvement control system, showing the regenerative power flow during braking in the modulated operation of V-shaped excavation work. Note that some components have been added or omitted in Figure 5 for the sake of simplicity.

[0035] As shown in Figure 5, in the work efficiency improvement control, during braking in modulated operation, the output of engine 1 is increased in advance so that the large output of engine 1 necessary for the transition to sudden acceleration after sudden braking can be immediately produced. In other words, by suppressing the delay in the output of engine 1, it becomes possible to perform sudden acceleration in modulated operation, and thus a reduction in the time required for modulated operation, i.e., an improvement in work efficiency [t / h], can be expected.

[0036] Here, we will explain in detail the control methods for improving the operational efficiency of power-driven systems.

[0037] Figure 6 is a functional block diagram showing the processing details in the controller function unit of a generator inverter.

[0038] In Figure 6, the controller function unit of the generator inverter 7 includes a voltage control unit 71 that calculates a command value such that the difference between the DC bus voltage command and the DC bus voltage is small, a conversion gain calculation unit 72 that calculates a command value corresponding to the MG torque command, a command value selection unit 73 that selects either the command value of the voltage control unit 71 or the conversion gain calculation unit 72 according to the MG mode control command from the vehicle control device 15, a current limiting unit 74 that defines the upper limit of the command value selected by the command value selection unit 73, and a current control unit 75 that calculates and outputs a command value (MG inverter voltage command) that controls the operation of the generator inverter 7 such that the difference between the MG current command via the current limiting unit 74 and the MG current is small.

[0039] As shown in Figure 6, when the MG control mode command instructs voltage control (described later), the generator inverter 7 selects a command value from the voltage control unit 71 in the command value selection unit 73 and performs feedback control so that the voltage of the DC bus electrically connecting the generator inverter 7 and the travel motor inverter 10 becomes the desired voltage (the voltage indicated by the DC bus voltage command).

[0040] Furthermore, when the MG control mode command instructs torque control (described later), the generator inverter 7 selects a command value from the conversion gain calculation unit 72 in the command value selection unit 73 and controls the output torque of the generator 6 to match the value indicated by the MG torque command from the vehicle control device 15.

[0041] Figure 7 is a functional block diagram showing the functional parts related to the control of the power drive system of the vehicle control device.

[0042] In Figure 7, the vehicle control device 15 includes a modulate determination unit 151 that determines whether the wheel loader 100 is performing modulate operation based on the vehicle speed obtained from CAN communication, etc. and the signal from the forward / reverse selector switch 104a; an MG control mode switching unit 152 that outputs an MG control mode command to the generator inverter 7 instructing either voltage control or torque control according to the determination result of the modulate determination unit 151; a power generation amount calculation unit 153 that calculates a target value for the amount of power generated by the generator 6 based on the fuel injection upper limit value and engine torque obtained from CAN communication, etc.; and an MG torque calculation unit 154 that calculates an MG torque command and outputs it to the generator inverter 7 based on the target value of power generation calculated by the power generation amount calculation unit 153 and the engine speed obtained from CAN communication, etc.

[0043] Figure 8 is a flowchart showing the processing contents of the modulate determination unit and the MG control mode switching unit of the vehicle control device.

[0044] As shown in Figure 8, the vehicle control device 15 first receives a vehicle speed signal from CAN communication or the like in the modulate determination unit 151, as well as a signal from the forward / reverse selector switch 104a (step S101).

[0045] Next, it is determined whether the vehicle speed and the direction of travel indicated by the signal from the forward / reverse switch 104a are of the same sign, that is, whether the current direction of travel of the wheel loader 100 is the same as the direction of travel indicated by the operator using the forward / reverse switch 104a (step S102).

[0046] If the result of the determination in step S102 is YES, that is, if the direction indicated by the forward / reverse switch 104a matches the direction of travel of the wheel loader 100 (in the case of non-modulated operation), an MG control mode command instructing voltage control of the generator 6 is generated and output to the generator inverter 7 (step S103), and the process ends.

[0047] Furthermore, if the result of the determination in step S102 is NO, that is, if the direction indicated by the forward / reverse switch 104a and the direction of travel of the wheel loader 100 are different (indicating a possible modulated operation), it is determined whether or not the vehicle speed is above a predetermined threshold (step S104).

[0048] If the result of the determination in step S104 is NO, that is, if the vehicle speed is less than the threshold, it is determined that a rollback on a slope or the like is occurring (non-modulated operation), and an MG control mode command instructing voltage control of the generator 6 is generated and output to the generator inverter 7 (step S103), and the process ends.

[0049] Furthermore, if the result of the determination in step S104 is YES, that is, if the vehicle speed is above the threshold (in the case of non-modulated operation), an MG control mode command instructing torque control of the generator 6 is generated and output to the generator inverter 7 (step S103), and the process ends.

[0050] Thus, in this embodiment, the calculation of the MG torque command when the generator 6 is set to torque control is performed in parallel with the determination process of the MG control mode command based on the detection of modulated operation. By calculating the MG torque command, the amount of power generated by the generator 6 during regenerative operation in the modulated operation of the wheel loader 100 can be optimized, enabling a highly responsive and smooth starting operation without reducing the rotational speed of the engine 1 even during subsequent rapid starts.

[0051] Next, we will explain in detail the processing details of the power generation calculation unit 153.

[0052] Figure 9 is a functional block diagram showing the processing details in the power generation calculation unit of the vehicle control device.

[0053] As shown in Figure 9, the power generation calculation unit 153 determines the power generated by the generator 6 based on the fuel injection state (output ratio of engine torque) of the engine 1. First, the power generation calculation unit 153 receives the fuel injection upper limit value and engine torque (more precisely, a value corresponding to the fuel injection amount obtained from a table determined in advance by measuring the relationship between engine torque and fuel injection amount for engine 1) included in the CAN signal from the engine ECU (not shown) and determines the power generation amount. At this time, the calculation unit 153a finds the difference between the fuel injection upper limit value and the engine torque (both in units of [%], for example, showing a ratio to the rated value), and the determination unit 153b determines the power generation amount according to the magnitude of the difference. For example, if the difference between the fuel injection upper limit value and the engine torque is small, it indicates that the output of engine 1 is close to the upper limit, and if it tries to produce more output, the rotational speed of engine 1 may decrease. On the other hand, if the difference between the fuel injection upper limit value and the engine torque is large, it indicates that the engine output has a large margin over the upper limit, and it may take some time to increase the output. Therefore, in modulated operation of the wheel loader 100, when a relatively large output is required, that is, when transitioning from a sudden braking state to a sudden acceleration state, it is effective to maintain an appropriate difference between the fuel injection upper limit and engine torque.

[0054] The power generation calculation unit 153 receives the fuel injection upper limit value and engine torque, which are state variables output via CAN communication from the engine ECU (not shown), and calculates the difference in the calculation unit 153a. The determination unit 153b then determines a provisional value for the power generation command to increase or decrease the power generation amount of the generator 6 according to the calculated difference. For example, if the difference is greater than a threshold X1 (e.g., 20 [%]), the provisional value of the power generation command is increased by a preset appropriate value (e.g., +α [kW]) to increase the power generation amount further. If the difference is less than a threshold X2 (e.g., 10 [%]), the output of the engine 1 is considered to be close to the upper limit, and the power generation amount of the generator 6 is decreased by an appropriate value to further decrease the power generation amount. Furthermore, if the difference between the fuel injection upper limit value and the engine torque is less than or equal to the threshold X1 and greater than or equal to X2, the power generation amount is determined to maintain the current output.

[0055] The thresholds X1 and X2 mentioned above are values ​​that can be arbitrarily adjusted according to the vehicle's acceleration. For example, threshold X1 could be set to a value where the difference between the fuel injection upper limit and the engine torque is relatively large (a difference large enough to cause a delay in starting when the vehicle moves to a standstill), while threshold X2 could be set to a value where the difference between the fuel injection upper limit and the engine torque is relatively small (a difference large enough to cause a decrease in engine speed when the vehicle moves to a standstill). In this embodiment, the amount of power generated by the generator 6 is increased or decreased by αkW (an arbitrary value). This is to suppress fluctuations in rotational speed caused by sudden changes in the load on the engine 1.

[0056] The power generated by the generator 6 (generated power) is consumed by the external resistor 14 together with the regenerative power from the drive motor 9. Therefore, as shown in Figure 12, it is necessary to limit the sum of the power generated by the generator 6 and the regenerative power from the drive motor 9 so as not to exceed the capacity (rated) of the external resistor 14. When the wheel loader 100 is braking, limiting the regenerative power of the drive motor 9 may reduce the vehicle's motion (braking) performance, so priority is given to maintaining the regenerative power of the drive motor 9, and the power generated by the generator 6 is limited. Note that the regenerative power of the drive motor 9 decreases as the vehicle speed decreases during regeneration, so the power generated by the generator 6 should be increased accordingly.

[0057] The effects and advantages of this embodiment, configured as described above, will be explained with reference to the drawings.

[0058] Figure 10 shows the state quantities of each part during modulated operation in the prior art, presented as a comparative example. Figure 11 shows the state quantities of each part during modulated operation in this embodiment.

[0059] figure 10As shown, in the comparative example, regenerative power is generated from the drive motor 9 during deceleration (Figure (a)), and this regenerative power is consumed (motorized) by the generator 6, so the MG power becomes positive, the rotational speed of the engine 1 increases, and the engine 1 stops fuel injection. In other words, the engine torque becomes zero. Subsequently, at the start of acceleration (Figure (b)), power generated from the generator 6 is suddenly needed, and the engine 1 is put under load, so the rotational speed of the engine 1 decreases, and thereafter, the MG power does not increase smoothly (Figure (c)), and as a result the vehicle starts slowly.

[0060] In contrast, in this embodiment, Figure 11 As shown, regenerative power is generated from the drive motor 9 during deceleration (Figure (a)), but the generator 6 is not motorized, and forced power generation is started in the generator 6 as well, so the MG power gradually increases to the negative side (power generation side). As a result, the engine 1 continues fuel injection, increasing engine torque, and when the wheel loader moves into forward motion, it can continue output smoothly without causing a sudden change in output, that is, without causing an unintended decrease in the rotational speed of the engine 1. As a result, it can respond to sudden acceleration after sudden braking of the vehicle.

[0061] Thus, in this embodiment, when the modulated operation of the wheel loader 100 is detected, the generator 6 is made to generate power at an amount that takes into account the state of the engine 1 during braking (regeneration), making it possible to smoothly output the power needed for the subsequent sudden acceleration from the engine 1. In other words, by adjusting the generated power during vehicle braking according to the state of the engine during modulated operation, power can be supplied from the engine more smoothly when starting after braking.

[0062] <Note> It should be noted that the present invention is not limited to the embodiments described above, and includes various modifications and combinations that do not depart from the spirit of the invention. Furthermore, the present invention is not limited to having all the configurations described in the embodiments described above, and includes configurations in which some of the configurations are omitted. In addition, some or all of the above configurations, functions, etc. may be realized by designing, for example, an integrated circuit. Furthermore, each of the above configurations, functions, etc. may be realized in software by having a processor interpret and execute a program that realizes each function. [Explanation of symbols]

[0063] 1…Engine, 2…Front frame, 3…Rear frame, 4…Hydraulic pump, 5…Hydraulic work equipment, 6…Generator, 7…Generator inverter, 8…Propeller shaft, 9…Traction motor, 10…Traction motor inverter, 11a,11b…Front wheels, 11c,11d…Gears, 11e…Differential gear, 12a,12b…Rear wheels, 12c,12d…Gears, 12e…Differential gear, 13…Center joint, 14…External resistor, 15…Vehicle control device, 50…Control valve, 51…Bucket cylinder, 52…Lift cylinder, 53…Steering cylinder, 71…Electric Pressure control unit, 72...Conversion gain calculation unit, 73...Command value selection unit, 74...Current limiting unit, 75...Current control unit, 100...Wheel loader, 102...Front frame, 103...Rear frame, 104...Cab, 104a...Forward / reverse selector switch, 104a...Forward / reverse selector switch, 104b...Control ON / OFF switch, 107...Bucket, 108...Lift arm, 109...Center pin, 151...Modulate determination unit, 152...MG control mode switching unit, 153...Power generation amount calculation unit, 153a...Calculation unit, 153b...Determination unit, 154...MG torque calculation unit, 200...Excavation target, 300...Dump truck

Claims

1. A generator driven by an engine, A traction motor that drives the vehicle body using electricity from the aforementioned generator, A forward / reverse switch for switching the direction of travel of the vehicle body between forward and reverse, An external resistor that consumes regenerative power from the aforementioned traction motor, In a work vehicle equipped with a vehicle control device, If there is a difference between the direction of travel of the vehicle body indicated by the forward / reverse selector switch and the direction of travel of the vehicle body indicated by the rotation direction of the traction motor, If the difference between the predetermined fuel injection upper limit and the fuel injection amount for the engine is greater than the first threshold, the generator's power output is controlled to increase. A work vehicle characterized in that, when the difference between the fuel injection upper limit and the fuel injection amount is less than a second threshold value that is set in advance as a value less than the first threshold value, the generator is controlled to reduce the power generated by the generator.

2. A generator driven by an engine, A traction motor that drives the vehicle body using electricity from the aforementioned generator, A forward / reverse switch for switching the direction of travel of the vehicle body between forward and reverse, An external resistor that consumes regenerative power from the aforementioned traction motor, In a work vehicle equipped with a vehicle control device, The aforementioned vehicle control device is A work vehicle characterized in that, when there is a difference between the direction of travel of the vehicle body indicated by the forward / reverse selector switch and the direction of travel of the vehicle body indicated by the rotation direction of the traction motor, the control of the generator is switched from voltage control to torque control.

3. A generator driven by an engine, A traction motor that drives the vehicle body using electricity from the aforementioned generator, A forward / reverse switch for switching the direction of travel of the vehicle body between forward and reverse, An external resistor that consumes regenerative power from the aforementioned traction motor, In a work vehicle equipped with a vehicle control device, The aforementioned vehicle control device is If there is a difference between the direction of travel of the vehicle body indicated by the forward / reverse selector switch and the direction of travel of the vehicle body indicated by the rotation direction of the traction motor, The generator's power output is increased or decreased based on the difference between a preset fuel injection upper limit and the fuel injection amount for the aforementioned engine. A work vehicle characterized by limiting the power generated by the generator so that the sum of the power generated by the generator and the regenerative power from the traction motor does not exceed the rated power of the external resistor.

4. A generator driven by an engine, A traction motor that drives the vehicle body using electricity from the aforementioned generator, A forward / reverse switch for switching the direction of travel of the vehicle body between forward and reverse, Control ON / OFF switch, An external resistor that consumes regenerative power from the aforementioned traction motor, In a work vehicle equipped with a vehicle control device, The aforementioned vehicle control device is When the control ON / OFF switch is in the ON state, if there is a difference between the direction of travel of the vehicle body indicated by the forward / reverse selector switch and the direction of travel of the vehicle body indicated by the rotation direction of the drive motor, The generator's power output is increased or decreased based on the difference between a preset fuel injection upper limit and the fuel injection amount for the aforementioned engine. A work vehicle characterized in that, when the control ON / OFF switch is in the OFF state, if there is a difference between the direction of travel of the vehicle body indicated by the forward / reverse selector switch and the direction of travel of the vehicle body indicated by the rotation direction of the traction motor, the generator will not generate electricity.

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