Electrically driven vehicles

Abstract

To provide an electric driven vehicle which can increase the opportunities for generating regenerative electric power from a traveling motor and can reduce fuel consumption by utilizing the same.SOLUTION: A controller 100 controls invertors 33, 34 for traveling so that traveling motors 35, 36 generate regenerative electric power at least partially when a coasting state is detected, and operates a converter 60, calculates output power P of the converter 60 and drive power Q of motors 47 to 50 for auxiliary machines, controls invertors 43 to 46 for auxiliary machines and a charge / discharge controller 91 so that the output power P is supplied only for the motors 47 to 50 for auxiliary machines when the output power P is equal to or lower than the drive power Q, and controls the invertors 43 to 46 for auxiliary machines and the charge / discharge controller 91 so that the output power P is supplied for the motors 47 to 50 for auxiliary machines and a storage battery 90 when the output power P is equal to or higher than the drive power Q.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an electric drive vehicle such as a dump truck.

Background Art

[0002] An electric drive dump truck is based on a vehicle body with four wheels. A cab and a control box are installed at the upper front of the vehicle body frame, and an engine, a generator, and a hydraulic pump, which are power units, are arranged at the lower front of the vehicle body frame. A rear axle composed of a traveling motor and a speed reducer is installed at the lower rear of the vehicle body frame. A loading platform that can be lifted and lowered by a hydraulic cylinder is provided from the center to the rear of the upper part of the vehicle body frame. A large amount of transported objects such as crushed stones or earth and sand are loaded on the loading platform and transported.

[0003] A large amount of transported objects are loaded into the dump truck by a loader (for example, a hydraulic excavator). After the dump truck transports the transported objects to the destination and travels, by extending the hydraulic cylinder, the loading platform is lifted and lowered with the hinge pin as the rotation center, the transported objects are dumped, and the transportation is completed. Then, it returns to the loading area and repeats the above process.

[0004] The above dump truck generates electricity by an engine as a main generator, and the power is transmitted to an electric motor in the rear axle by an inverter and a controller to drive the electric motor. The tires rotate through a speed reducer to make the vehicle travel. When decelerating or stopping, a means (electric brake) for decelerating by regenerative braking by the electric motor is used. The regenerative power generated there is supplied to a heating resistor of a heat generating brake resistance device, converted into heat, and the heat is exhausted to the outside by a blower.

[0005] Furthermore, the generator and drive motor generate heat during operation and therefore require cooling, and a cooling system is installed for this purpose. The cooling system is primarily air-cooled, with a cooling blower driven by an electric motor that blows cooling air. The power to drive this system comes from an auxiliary generator separate from the main generator, and the auxiliary electric motor is driven and controlled by an inverter and controller to keep the objects to be cooled below a desired temperature.

[0006] Prior art documents disclosing electric-driven dump truck technology include, for example, Patent Documents 1 and 2. The hybrid dump truck described in Patent Document 1 stores the generated electricity or electricity regenerated during deceleration in a battery, and discharges it during acceleration to drive an electric motor and drive the truck.

[0007] Furthermore, in the hybrid vehicle described in Patent Document 2, when charging the battery with regenerative power during electric braking in the auto-cruise state on a downhill road where no driving force is required during driving, the regenerative power is used to drive an electric pump (auxiliary equipment) and consume the regenerative power before the battery's charge capacity overflows. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2000-299901 [Patent Document 2] Japanese Patent Publication No. 2017-30595 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] As described above, electric-driven dump trucks operate by accelerating, driving, decelerating, and stopping using the drive and braking of the drive motor to transport cargo. However, it is desirable to reduce the fuel consumption of dump trucks. To achieve this, efficient use of energy in the vehicle drive system is required. Here, as described in Patent Documents 1 and 2, it is possible to reduce fuel consumption by installing a storage battery, charging the battery with regenerative power during electric braking, and using that stored power to drive the motor through battery charge and discharge control. However, installing a storage battery reduces the amount of cargo that can be transported by the mass of the storage battery, thus reducing the transport efficiency.

[0010] To maintain the load capacity of the transported goods, it is necessary to either not install batteries or to install only a small amount of batteries. However, needless to say, without batteries, regenerative power during electric braking cannot be stored, and the fuel efficiency reduction effect cannot be obtained. Alternatively, if the amount of batteries installed is small, only a small amount of regenerative power can be stored, and some of the charge and discharge energy is converted into heat due to the charge and discharge losses of the batteries, so the fuel efficiency reduction effect is limited.

[0011] On the other hand, instead of storing the regenerative power generated during electric braking in a battery, there is a method of directly using it as auxiliary power for other vehicles. This method is energy efficient because there are no charge / discharge losses associated with using a battery, but the amount of time it can be used is limited, so the effect on reducing fuel consumption is limited.

[0012] In summary, to solve the challenge of reducing fuel consumption in electric-driven dump trucks, it is necessary to increase opportunities to generate regenerative power and immediately utilize it as auxiliary power, rather than prioritizing the storage of regenerative power generated during electric braking in a battery.

[0013] The present invention has been made in view of the above problems, and its purpose is to provide an electric drive vehicle that can reduce fuel consumption by increasing the opportunities for regenerative power generation from the drive motor and utilizing it. [Means for solving the problem]

[0014] To achieve the above objective, the present invention provides an engine, a main generator and an auxiliary generator driven by the engine, a main rectifier that converts the power generated by the main generator into DC power, an auxiliary rectifier that converts the power generated by the auxiliary generator into DC power, a main circuit to which DC power is supplied from the main rectifier, an auxiliary circuit to which DC power is supplied from the auxiliary rectifier, a storage battery, a charge / discharge controller that supplies power between the storage battery and the auxiliary circuit, a drive motor, and a device that converts the DC power of the main circuit into AC power to power the drive motor A drive inverter that supplies power to the main circuit, an auxiliary motor, an auxiliary inverter that converts the DC power of the auxiliary circuit into AC power and supplies it to the auxiliary motor, a converter that steps down the DC power of the main circuit and supplies it to the auxiliary circuit, an accelerator pedal that instructs the drive motor to increase speed, a brake pedal that instructs the drive motor to decelerate, and in response to input signals from the accelerator pedal and the brake pedal, the main generator, the auxiliary generator, the charge / discharge controller, the drive inverter, the auxiliary inverter, In an electric drive vehicle, the vehicle is equipped with a vehicle speed sensor for detecting vehicle speed, and the controller controls the converter, wherein the controller controls the drive inverter so that the drive motor generates regenerative power when the brake pedal is operated, the controller detects a state where neither the accelerator pedal nor the brake pedal is operated and the vehicle speed is above a predetermined threshold as a coasting state, and in at least part of the time when the coasting state is detected, the controller controls the drive inverter so that the drive motor generates regenerative power, operates the converter, calculates the output power of the converter and the drive power of the auxiliary motor, controls the auxiliary inverter and the charge / discharge controller so that the output power is supplied only to the auxiliary motor if the output power is less than or equal to the drive power, and controls the auxiliary inverter and the charge / discharge controller so that the output power is supplied to the auxiliary motor and the battery if the output power is greater than the drive power. The vehicle further comprises a cargo bed and a sensor for detecting the amount of cargo on the cargo bed. The controller detects the coasting state, and if the amount of cargo detected by the sensor is above a predetermined threshold value, it controls the drive inverter to prevent the generation of regenerative power and prevents the converter from operating. It shall be considered as such.

[0015] According to the present invention configured as described above, during coasting when neither the accelerator pedal nor the brake pedal is being operated, in addition to when the brake pedal is operated, regenerative power is generated by the driving motor, and this regenerative power is used to supply the driving power of the auxiliary motor, while surplus power exceeding the driving power of the auxiliary motor is charged into the storage battery, and the power stored in the storage battery is later used to drive the auxiliary motor, thereby suppressing the power generation of the auxiliary generator. As a result, since the load on the engine is reduced, it becomes possible to improve the fuel efficiency of the engine. Furthermore, according to the present invention, when coasting with a large load on the cargo bed, regenerative power is not generated and the drive motor does not generate braking force, thus preventing any impact on the driving operation.

Advantages of the Invention

[0016] According to the electric drive vehicle according to the present invention, it is possible to increase the opportunities for the regenerative power of the driving motor to be generated and use it to reduce the fuel consumption. Furthermore, when coasting with a large load on the cargo bed, regenerative power is not generated, and the drive motor does not produce braking force, thus preventing any impact on the vehicle's movement.

Brief Description of the Drawings

[0017] [Figure 1] Schematic diagram of a dump truck in the first embodiment of the present invention [Figure 2] Configuration diagram of an electric drive system in the first embodiment of the present invention [Figure 3] Control flowchart of an electric drive system in the first embodiment of the present invention [Figure 4] Configuration diagram of an electric drive system in the second embodiment of the present invention [Figure 5] Control flowchart of an electric drive system in the second embodiment of the present invention [Figure 6] Configuration diagram of an electric drive system in the third embodiment of the present invention [Figure 7] Control flowchart of an electric drive system in the third embodiment of the present invention

Modes for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each figure, equivalent elements are denoted by the same reference numerals, and redundant descriptions will be omitted as appropriate. Further, although this embodiment applies the electric drive vehicle according to the present invention to a dump truck, the application target of the present invention is not limited thereto.

Example

[0019] FIG. 1 is a side view of a dump truck in a first embodiment of the present invention. As shown in FIG. 1, the dump truck includes a vehicle body frame 1 and a loading platform 3 on which a load 2 such as earth and sand is placed. The vehicle body frame 1 and the loading platform 3 are connected by a hoist cylinder 4 and a hinge pin 5. By expanding and contracting the hoist cylinder 4, the loading platform 3 rotates vertically with respect to the vehicle body frame 1 about the hinge pin 5 as a fulcrum, and the load 2 can be dumped.

[0020] On the vehicle body frame 1, left and right front wheels 6L, 6R, left and right rear wheels 7L, 7R, a hydraulic oil tank (not shown), etc. are attached via mechanism parts not shown. On the rotating shaft portions of the rear wheels 7L, 7R, traveling motors 35, 36 (shown in FIG. 2) for driving the rear wheels 7L, 7R and a speed reducer for adjusting the rotational speed of the rear wheels 7L, 7R are housed.

[0021] The dump truck also includes a pair of front wheel suspension cylinders 9L, 9R on the front side of the vehicle body frame 1 and a pair of rear wheel suspension cylinders 10L, 10R on the rear side of the vehicle body frame 1. The front wheel suspension cylinders 9L, 9R are independent suspension cylinders that can independently move the left and right front wheels 6L, 6R up and down. The upper end side thereof is attached to the vehicle body frame 1, and the lower end side is attached to a wheel support member (not shown) that supports the left and right front wheels 6L, 6R. The rear wheel suspension cylinders 10L, 10R are independent suspension cylinders that can independently move the left and right rear wheels 7L, 7R up and down. The upper end side thereof is attached to the vehicle body frame 1, and the lower end side is attached to a wheel support member (not shown) that supports the left and right rear wheels 7L, 7R.

[0022] A deck 11, on which the operator can walk, is attached to the front of the vehicle frame 1. The top surface of the deck 11 is equipped with a cab 12 on which the operator sits to operate the dump truck, a control cabinet 13 housing various electrical equipment, and a grid box 14 for dissipating excess energy from the control cabinet 13 as heat. In addition, a power unit 15 consisting of a main generator 30, an auxiliary generator 40 (both shown in Figure 2), and a main pump (not shown) as a hydraulic power source for hydraulic equipment is mounted in the area hidden by the front wheels 6L and 6R.

[0023] Figure 2 is a diagram showing the configuration of the electric drive system in this embodiment. In Figure 2, the electric drive system comprises an engine 20, a main generator 30, a main rectifier 31, a main circuit 32, drive inverters 33 and 34, drive motors 35 and 36, a chopper 37, a thermal resistor 38, an auxiliary generator 40, an auxiliary rectifier 41, an auxiliary circuit 42, auxiliary inverters 43 to 46, auxiliary motors 47 to 50, a converter 60, an accelerator pedal 70, a brake pedal 71, a vehicle speed sensor 72, a suspension pressure sensor 76, and a controller 100.

[0024] The main generator 30 and the auxiliary generator 40 are driven by the engine 20. The main rectifier 31 converts the power generated by the main generator 30 into DC power and supplies it to the main circuit 32. The auxiliary rectifier 41 converts the power generated by the auxiliary generator 40 into DC power and supplies it to the auxiliary circuit 42. The power and voltage of the main circuit 32 and the auxiliary circuit 42 differ significantly, with the main circuit 32 having higher power and higher voltage.

[0025] The drive inverters 33 and 34 convert the DC power from the main circuit 32 into AC power and supply it to the drive motors 35 and 36. The drive motors 35 and 36 drive the rear wheels 7L and 7R, which are the drive wheels, via a reduction gear (not shown). In addition, by operating the drive motors 35 and 36 as generators, an electric braking force can be applied to the rear wheels 7L and 7R to decelerate the vehicle body. The regenerative power generated by the drive motors 35 and 36 at that time is power whose voltage and current fluctuate depending on the driving conditions, and is converted into DC power by the drive inverters 33 and 34 and supplied to the main circuit 32. Most of the regenerative power supplied to the main circuit 32 is supplied to the thermal resistor 38 via the chopper 37, and is converted into heat by the thermal resistor 38. A portion of the remaining regenerative power is supplied to the auxiliary circuit 42 via the converter 60. The regenerative power supplied to the auxiliary circuit 42 is converted into AC power by the auxiliary inverters 43-46 and supplied to the auxiliary motors 47-50. At this time, at least a portion of the drive power Q of the auxiliary motors 47-50 is covered by regenerative power, so the load on the engine 20 can be reduced by suppressing or stopping the power generation of the auxiliary generator 40.

[0026] Auxiliary inverters 43-46 convert the DC power of the auxiliary circuit 42 into AC power and supply it to the auxiliary motors 47-50. The auxiliary motors 47-50 drive auxiliary equipment such as cooling fans 80-83. Converter 60 is a step-down device that steps down the DC power of the main circuit 32 and supplies it to the auxiliary circuit 42. Controller 100 controls the engine 20, main generator 30, auxiliary generator 40, drive inverters 33, 34, auxiliary inverters 43-46, and converter 60 in response to input signals from the accelerator pedal 70, brake pedal 71, vehicle speed sensor 72, and suspension pressure sensor 76.

[0027] The controller 100 has a coasting detection unit 101 that detects the coasting state of the dump truck. The coasting detection unit 101 is a functional block that is realized by an arithmetic unit such as a CPU executing a program stored in a storage device such as ROM or RAM.

[0028] Figure 3 is a control flow diagram of the electric drive system in this embodiment. The processing of each step will be described in order below.

[0029] The controller 100 first determines whether or not the brake pedal 71 has been operated (step S101). If it determines No in step S101, it controls the drive inverters 33 and 34 to generate regenerative power corresponding to the amount the brake pedal 71 has been operated, turns on the chopper 37, turns on the converter 60, turns on the charging of the battery 90 (step S102), and ends the flow. As a result, an electric braking force corresponding to the amount the brake pedal 71 has been operated is generated by the drive motors 35 and 36, and the vehicle body decelerates. In addition, most of the regenerative power from the drive motors 35 and 36 is consumed by the thermal resistor 38, and a portion of the remaining regenerative power is stepped down by the converter 60 and then used to drive the auxiliary motors 47 to 50 and to charge the battery 90.

[0030] If the result in step S101 is Yes, then it is determined whether or not the accelerator pedal 70 has been operated (step S103). If the result in step S103 is No, then the engine 20, main generator 30, and drive inverters 33, 34 are controlled so that power corresponding to the amount the accelerator pedal 70 is operated is supplied to the drive motors 35, 36, and the converter 60 is turned OFF (step S104), ending the flow. As a result, the vehicle accelerates according to the amount the accelerator pedal 70 is operated.

[0031] If the result in step S103 is Yes, then it is determined whether the vehicle speed is above a predetermined threshold F (step S105). If the result in step S105 is No, then the process proceeds to step S104.

[0032] If the answer in step S105 is Yes, the drive inverters 33 and 34 are controlled to generate regenerative power, and the converter 60 is turned ON (step S106). The regenerative power referred to here is, for example, regenerative power generated in accordance with an electric braking force that does not affect coasting, and does not have to be constant. As a result, at least a portion of the drive power Q of the auxiliary motors 47 to 50 is supplied by regenerative power during coasting, so that the power generation of the auxiliary generator 40 can be stopped or suppressed.

[0033] Following step S106, the output power P of the converter 60 and the drive power Q of the auxiliary motors 47-50 are calculated (step S107). The output power P of the converter 60 is calculated based on the output voltage of the converter 60 detected by the voltage sensor 74 and the output current of the converter 60 detected by the current sensor 75. The drive power Q of the auxiliary motors 47-50 is obtained by integrating the output power of the auxiliary inverters 43-46. Note that since the drive power Q is approximately equal to the power generated by the auxiliary generator 40, the power generated by the auxiliary generator 40 may also be used as the drive power Q.

[0034] Following step S107, it is determined whether the output power P of the converter 60 is less than or equal to the drive power Q of the auxiliary motors 47-50 (step S108). If it is determined to be Yes in step S108, the charging of the storage battery 90 is turned OFF (step S109), and the flow is terminated. As a result, the regenerative power during coasting is stepped down by the converter 60 and then used to drive the auxiliary motors 47-50.

[0035] If the result in step S108 is No, the charging of the battery 90 is turned ON (step S110), and the flow is terminated. As a result, the regenerative power during coasting is stepped down by the converter 60 and then used to drive the auxiliary motors 47-50 and to charge the battery 90.

[0036] (summary) In this embodiment, the system includes an engine 20, a main generator 30 and an auxiliary generator 40 driven by the engine 20, a main rectifier 31 that converts the power generated by the main generator 30 into DC power, an auxiliary rectifier 41 that converts the power generated by the auxiliary generator 40 into DC power, a main circuit 32 to which DC power is supplied from the main rectifier 31, an auxiliary circuit 42 to which DC power is supplied from the auxiliary rectifier 41, a storage battery 90, a charge / discharge controller 91 that supplies power between the storage battery 90 and the auxiliary circuit 42, travel motors 35 and 36, and a drive unit that converts the DC power of the main circuit 32 into AC power and supplies it to the travel motors 35 and 36. The system includes drive inverters 33 and 34, auxiliary motors 47 to 50, auxiliary inverters 43 to 46 that convert the DC power of the auxiliary circuit 42 into AC power and supply it to the auxiliary motors 47 to 50, a converter 60 that steps down the DC power of the main circuit 32 and supplies it to the auxiliary circuit 42, an accelerator pedal 70 that instructs the drive motors 35 and 36 to increase speed, a brake pedal 71 that instructs the drive motors 35 and 36 to decelerate, and in response to input signals from the accelerator pedal 70 and the brake pedal 71, the main generator 30, auxiliary generator 40, charge / discharge controller 91, drive inverters 33 and 34, and auxiliary inverters The electric drive vehicle includes a controller 100 that controls the accelerator pedals 43-46 and the converter 60, and the controller 100 controls the drive inverters 33, 34 so that the drive motors 35, 36 generate regenerative power when the brake pedal 71 is operated, and includes a vehicle speed sensor 72 that detects the vehicle speed, and the controller 100 detects as a coasting state when neither the accelerator pedal 70 nor the brake pedal 71 is operated and the vehicle speed is above a predetermined threshold F, and in at least a portion of the cases when the coasting state is detected, the drive motor The system controls the traction inverters 33 and 34 so that the motors 35 and 36 generate regenerative power, activates the converter 60, calculates the output power P of the converter 60 and the drive power Q of the auxiliary motors 47 to 50, and controls the auxiliary inverters 43 to 46 and the charge / discharge controller 91 so that the output power P is supplied only to the auxiliary motors 47 to 50 if the output power P is greater than the drive power Q, controls the auxiliary inverters 43 to 46 and the charge / discharge controller 91 so that the output power P is supplied to both the auxiliary motors 47 to 50 and the battery 90.

[0037] According to this embodiment configured as described above, regenerative power is generated by the drive motors 35 and 36 not only when the brake pedal 71 is operated, but also when coasting and neither the accelerator pedal 70 nor the brake pedal 71 is operated. This regenerative power is used to supply the drive power Q of the auxiliary motors 47 to 50, and any surplus power exceeding the drive power Q of the auxiliary motor 47 is charged into the storage battery 90. The power stored in the storage battery 90 is then used to drive the auxiliary motors 47 to 50, thereby suppressing the power generation of the auxiliary generator 40. As a result, the load on the engine 20 is reduced, making it possible to improve the fuel efficiency of the engine 20.

[0038] Furthermore, the regenerative power generated during coasting is equivalent to the driving power of the auxiliary motors 47-50 (several tens of kW), and is very small compared to the regenerative power generated when the brake pedal 71 is pressed (several thousand kW), so it has almost no effect on driving operation. In addition, by directly using the regenerative power as the driving power for the auxiliary motors 47-50, the capacity of the battery used to store the regenerative power can be reduced. This ensures that the load capacity of the dump truck is maintained, and productivity can be maintained without reducing transportation efficiency. [Examples]

[0039] A second embodiment of the present invention will be described, focusing on the differences from the first embodiment. In the first embodiment, the drive motors 35 and 36 generate braking force during coasting, regardless of the inclination angle of the running surface. Here, during coasting on a downhill slope, gravity acts in the direction of acceleration of the vehicle body, so even if the drive motors 35 and 36 generate braking force, it does not affect the driving operation. On the other hand, if the drive motors 35 and 36 generate braking force during coasting on a slope other than a downhill slope, there is a risk that the vehicle speed will decrease significantly. This embodiment solves this problem.

[0040] Figure 4 is a diagram showing the configuration of the electric drive system in this embodiment. In Figure 4, the electric drive system further includes a suspension pressure sensor 76 that detects the pressure of the front suspension cylinders 9L, 9R and the rear suspension cylinders 10L, 10R, and the controller 100 further includes a descent angle calculation unit 104 that calculates the descent angle θ of the running surface.

[0041] Figure 5 is a control flow diagram of the electric drive system in this embodiment. In Figure 5, the processing of steps S201 to S205 is the same as steps S101 to S105 (shown in Figure 3) of the first embodiment.

[0042] If it is determined in step S205 that the vehicle speed is equal to or greater than the threshold F (Yes), then it is determined in step S206 whether the downward slope angle θ is equal to or greater than a predetermined threshold α (for example, 3°). The downward slope angle θ is calculated using the following formula.

[0043]

number

[0044] Here, the front wheel load Wf is determined from the pressures of the front suspension cylinders 9L and 9R, and the rear wheel load Wf is determined from the pressures of the rear suspension cylinders 10L and 10R.

[0045] If the result in step S206 is determined to be No, the process in step S204 is executed, and the flow is terminated. As a result, when coasting on an incline other than a downhill slope, regenerative power is not generated and the driving motors 35 and 36 do not generate braking force, thus preventing any impact on the driving operation.

[0046] If the result in step S206 is Yes, the processes from step S207 onwards are executed. The processes in steps S207 to S211 are the same as steps S106 to S110 of the first embodiment (shown in Figure 5).

[0047] (summary) In this embodiment, the electric-driven vehicle is equipped with a sensor (suspension pressure sensor 76) for detecting the downward slope angle θ of the running surface. The controller 100 detects a coasting state, and if the downward slope angle θ detected by the sensor is less than a predetermined threshold α, it controls the running inverters 33 and 34 to prevent regenerative power from being generated, and does not operate the converter 60.

[0048] According to this embodiment configured as described above, during coasting on slopes other than downhill slopes (where deceleration due to driving resistance is large), regenerative power is not generated and the driving motors 35 and 36 do not generate braking force, thus preventing any impact on driving operation. In this embodiment, the downhill slope angle θ was calculated using the output of the suspension pressure sensor 76, but it may also be calculated using the output of a tilt sensor mounted on the vehicle body. [Examples]

[0049] A third embodiment of the present invention will be described, focusing on the differences from the first embodiment. In the first embodiment, the drive motors 35 and 36 generate braking force during coasting, regardless of the load on the cargo bed 3. Here, the vehicle mass and the driving resistance are proportional, and the greater the vehicle mass, the greater the driving resistance. Therefore, if the drive motors 35 and 36 generate braking force during coasting with a large load on the cargo bed 3, the vehicle speed may decrease significantly. This embodiment solves this problem.

[0050] Figure 6 is a diagram showing the configuration of the electric drive system in this embodiment. In Figure 6, the controller 100 has a load amount calculation unit 105 that calculates the load amount W of the cargo bed 3, instead of the descent inclination angle calculation unit 104 (shown in Figure 4).

[0051] Figure 7 is a control flow diagram of the electric drive system in this embodiment. In Figure 7, the processing in steps S301 to S305 is the same as steps S201 to S205 in the second embodiment (shown in Figure 5).

[0052] If it is determined in step S305 that the vehicle speed is equal to or greater than the threshold F (Yes), then it is determined in step S306 whether the load capacity W of the cargo bed 3 is equal to or greater than a predetermined threshold M (for example, 100 tons). The load capacity W is determined by subtracting the sum of the front wheel load Wf and rear wheel load Wr in an unloaded state from the sum of the front wheel load Wf, determined from the pressure of the front wheel suspension cylinders 9L and 9R, and the rear wheel load Wr, determined from the pressure of the rear wheel suspension cylinders 10L and 10R.

[0053] If the result in step S306 is determined to be No, the process in step S304 is executed, and the flow is terminated. As a result, when coasting with a large load W, regenerative power is not generated and the drive motors 35 and 36 do not generate braking force, thus preventing any impact on the driving operation.

[0054] If the result in step S306 is "Yes", the processes from step S307 onwards are executed. The processes in steps S307 to S311 are the same as those in steps S207 to S311 of the second embodiment (shown in Figure 5).

[0055] (summary) In this embodiment, the electric-driven vehicle includes a cargo bed 3 and a sensor (suspension pressure sensor 76) for detecting the load amount W of the cargo bed 3. The controller 100 detects a coasting state, and if the load amount W detected by the sensor is greater than or equal to a predetermined threshold M, it controls the drive inverters 33 and 34 to prevent the generation of regenerative power and does not operate the converter 60.

[0056] According to this embodiment configured as described above, when coasting with a large load W (resulting in a large deceleration due to driving resistance), regenerative power is not generated, and the driving motors 35 and 36 do not generate braking force, thus preventing any impact on the driving operation. In this embodiment, the determination of whether or not to generate regenerative power during coasting is made based on the load W (step S306), but the determination may also be made based on the vehicle mass.

[0057] Although embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above and includes various modifications. For example, the embodiments described above are described in detail in order to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to having all the configurations described. Furthermore, it is possible to add parts of the configuration of one embodiment to the configuration of another embodiment, and it is also possible to delete parts of the configuration of one embodiment or replace parts of parts of another embodiment. [Explanation of symbols]

[0058] 1...Body frame, 2...Cargo, 3...Cargo bed, 4...Hoist cylinder, 5...Hinge pin, 6L, 6R...Front wheels, 7L, 7R...Rear wheels, 9L, 9R...Front suspension cylinders, 10L, 10R...Rear suspension cylinders, 11...Deck, 12...Cab, 13...Control cabinet, 14...Grid box, 15...Power unit, 20...Engine, 30...Main generator, 31...Main rectifier, 32...Main circuit, 33, 34...Inverter for traction, 35, 36...Traction motor, 37...Chopper, 38...Thermal resistor, 4 0...Auxiliary generator, 41...Auxiliary rectifier, 42...Auxiliary circuit, 43-46...Auxiliary inverter, 47-50...Auxiliary motor, 60...Converter, 70...Accelerator pedal, 71...Brake pedal, 72...Vehicle speed sensor, 74...Voltage sensor, 75...Current sensor, 76...Suspension pressure sensor, 80-83...Cooling fan, 90...Battery, 91...Charge / discharge controller, 100...Controller, 101...Coasting detection unit, 102...Output power calculation unit, 103...Auxiliary power calculation unit, 104...Descent slope angle calculation unit, 105...Load amount calculation unit.

Claims

1. The engine and The engine drives a main generator and an auxiliary generator, A main rectifier that converts the power generated by the main generator into DC power, An auxiliary rectifier that converts the power generated by the auxiliary generator into DC power, The main circuit is supplied with DC power from the aforementioned main rectifier, An auxiliary circuit supplied with DC power from the aforementioned auxiliary rectifier, Storage batteries and A charge / discharge controller that supplies power between the storage battery and the auxiliary circuit, The driving motor and A drive inverter that converts the DC power of the main circuit into AC power and supplies it to the drive motor, Auxiliary motor and An auxiliary inverter that converts the DC power of the auxiliary circuit into AC power and supplies it to the auxiliary motor, A converter that steps down the DC power of the main circuit and supplies it to the auxiliary circuit, An accelerator pedal that instructs the aforementioned drive motor to increase speed, A brake pedal that instructs the aforementioned drive motor to decelerate, The system includes a controller that controls the main generator, the auxiliary generator, the charge / discharge controller, the drive inverter, the auxiliary inverter, and the converter in response to input signals from the accelerator pedal and the brake pedal. In an electric vehicle, the controller controls the drive inverter so that the drive motor generates regenerative power when the brake pedal is operated, Equipped with a vehicle speed sensor that detects vehicle speed, The aforementioned controller, When neither the accelerator pedal nor the brake pedal is operated, and the vehicle speed is above a predetermined threshold, this is detected as a coasting state. In at least a portion of cases where the coasting state is detected, the drive inverter is controlled so that the drive motor generates regenerative power, the converter is activated, and the output power of the converter and the drive power of the auxiliary motor are calculated. If the output power is less than or equal to the drive power, the auxiliary inverter and the charge / discharge controller are controlled so that the output power is supplied only to the auxiliary motor. If the output power is greater than the drive power, the auxiliary inverter and the charge / discharge controller are controlled so that the output power is supplied to the auxiliary motor and the storage battery. The cargo bed and The vehicle further comprises a sensor for detecting the amount of cargo loaded on the cargo bed, The controller detects the coasting state and, if the load amount detected by the sensor is above a predetermined threshold value, it controls the drive inverter to prevent the generation of regenerative power and does not operate the converter. An electric-powered vehicle characterized by the following:

2. In the electric drive vehicle according to claim 1, Equipped with sensors to detect the downward slope angle of the running surface, The controller detects the coasting state and, if the downward slope angle detected by the sensor is less than a predetermined threshold, controls the drive inverter to prevent the generation of regenerative power and does not operate the converter. An electric-powered vehicle characterized by the following:

Images