JP2024022759A - Electrically-driven work vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrically-driven work vehicle capable of further reducing fuel consumption when the capacity of a secondary battery is comparatively small.

SOLUTION: An electrically-driven work vehicle includes: a main generator and an auxiliary generator driven by an engine; an electric motor for traveling driven by electric power supplied from the main generator; an auxiliary machine device driven by electric power supplied from the auxiliary generator; a regenerative device for supplying regenerative electric power generated at the time of vehicle braking of the electric motor for traveling, to the auxiliary machine device; and a battery capable of storing electric power to be supplied from the regenerative device and the auxiliary generator to the auxiliary machine device. The regenerative device determines a first electric discharge interval for discharging the battery according to a fuel consumption rate of the engine, and a second electric discharge interval for discharging the battery according to a magnitude of energy consumption of the vehicle, on the basis of a travel pattern of the electrically-driven work vehicle and the fuel consumption rate of the engine, and supplies electric power from the battery to the auxiliary machine device or the electric motor for traveling, on the basis of the first and second electric discharge intervals.

SELECTED DRAWING: Figure 9

COPYRIGHT: (C)2024,JPO&INPIT

Description

TECHNICAL FIELD The present invention relates to electrically driven work vehicles.

At work sites such as mines, many large dump trucks are in operation to transport ore and stripped soil from loading sites to dumping sites. At a work site, the route from the loading area to the dumping area is fixed, and if multiple dump trucks of the same vehicle size are on one route, they may operate 24 hours a day and travel back and forth repeatedly. This is intended to improve conveyance efficiency.

As described above, when operating a plurality of large dump trucks for a long period of time, emphasis is placed on transport efficiency, which is expressed as the amount of work (amount of energy) per unit cost (initial cost + running cost). In dump trucks, various measures are taken to reduce initial costs and running costs in order to improve transport efficiency. Of these, running costs can be reduced by reducing the engine's fuel consumption rate [g/kWh] using an electric drive system, which is a type of drive system that is highly efficient and requires relatively low maintenance costs. It is possible.

A dump truck's mechanical drive system uses a torque converter and transmission to transmit power from the engine to the tires, whereas an electric drive system uses the engine to drive a generator, which uses the generated electricity. This drives an electric motor connected to the tire shaft. In an electric drive system, a highly efficient electric motor is used and the engine can be driven at an operating point with high combustion efficiency, so an improvement in fuel consumption rate [g/kWh] (so-called fuel efficiency) can be expected. In addition, with electric drive systems, regenerative power can be obtained by generating electrical braking force with the electric motor for driving on the slopes (downhill slopes) that exist in many work sites such as mines, and this regenerative power can be used. By using it, further improvement in fuel efficiency can be expected. Specifically, the regenerated power generated during braking can be used to drive auxiliary equipment, or it can be used to temporarily charge a secondary battery and use it to drive the vehicle or auxiliary equipment during normal driving. It is possible to do so.

As described above, as a technology related to an electric drive system that utilizes a secondary battery, for example, the technology described in Patent Document 1 is known. Patent Document 1 discloses an engine, a generator driven by the engine, a motor that drives wheels using electric power, and a structure configured to be able to charge the electric power generated by the motor, and supply the charged electric power to the motor. A hybrid dump truck for mining, comprising: a power storage device; and a control device that controls charging to the power storage device and discharging from the power storage device; A hybrid dump truck for mining use is disclosed that includes a signal switch that selects a first discharge gain K1 when the load amount is larger than a threshold value, and selects a second discharge gain K2 when the load amount is smaller than a threshold value.

Japanese Patent Application Publication No. 2018-103984

In the above conventional technology, a relatively large capacity secondary battery is installed, and power from a generator driven by the engine is stored in the secondary battery, so that large engine power is required for driving the vehicle uphill. The aim is to reduce fuel consumption by supplying power from secondary batteries when the vehicle is in use.

On the other hand, if the capacity of the installed secondary battery is limited, such as in a system whose purpose is to drive auxiliary equipment using regenerated electric power generated by a traveling electric motor, it is necessary to secure the capacity of the secondary battery. Although costs are suppressed, even if the above-mentioned conventional technology is applied, the effect of improving the fuel efficiency of the engine is likely to be limited.

The present invention has been made in view of the above, and aims to provide an electrically driven work vehicle that can further improve the fuel consumption rate [g/kWh] of the engine even when the capacity of the secondary battery is relatively small. purpose.

The present application includes a plurality of means for solving the above problems, and one example thereof is an engine, a main generator and an auxiliary generator driven by the engine, and an electric power supplied from the main generator. a traveling electric motor to be driven, an auxiliary device driven by electric power supplied from the auxiliary generator, and a regeneration device supplying regenerative power generated when the electric traveling motor brakes the vehicle to the auxiliary device; In the electric drive work vehicle, the electric drive work vehicle includes the regeneration device and a battery capable of storing electric power supplied from the auxiliary generator to the auxiliary equipment device. a first discharging section that defines a section in which the battery is discharged according to the fuel consumption rate of the engine based on a traveling section or time of the electric drive vehicle; and a magnitude of energy consumption of the vehicle. The section in which the battery is discharged is determined as a traveling section of the electrically driven vehicle or a second discharge section defined by time, and the battery is discharged from the auxiliary machine based on the first and second discharge sections. Electric power shall be supplied to the device or the traveling electric motor.

According to the present invention, the fuel consumption rate of the engine can be further improved when the capacity of the secondary battery is relatively small.

FIG. 1 is a side view schematically showing the appearance of a dump truck that is an example of an electrically driven work vehicle. FIG. 2 is a diagram schematically showing a part of the electric drive system along with its peripheral components. FIG. 2 is a diagram showing an example of fuel efficiency characteristics of a diesel engine. FIG. 2 is a diagram showing a driving pattern of a dump truck in a mine, which is an example of a work site, as a change in vehicle speed. FIG. 5 is a diagram illustrating an example of a change in charge amount (charging/discharging characteristics) in the driving pattern illustrated in FIG. 4 . FIG. 5 is a diagram illustrating an example of changes in the fuel consumption rate of the engine in the driving pattern illustrated in FIG. 4 . FIG. 2 is a functional block diagram showing the processing contents of a functional unit related to a discharge section determination process that determines a discharge section among the processing functions of the regeneration control device. It is a flowchart which shows the processing content of the discharge area determination process in a regeneration control apparatus. FIG. 5 is a diagram illustrating an example of a case where a fuel efficiency threshold is set for the transition of the fuel consumption rate of the engine in the driving pattern shown in FIG. 4 and first and second discharge sections are set. A diagram showing an example of the change in the amount of charge (charging/discharging characteristics) when the engine fuel efficiency threshold is set as shown in FIG. 9 and the first and second discharge sections are set in the driving pattern shown in FIG. 4. It is. It is a figure explaining the improvement situation of the fuel consumption rate with respect to the prior art of this Embodiment. FIG. 2 is a diagram schematically illustrating a part of an electric drive system of a comparative example along with its peripheral configuration.

Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, a dump truck having a loading platform for loading objects will be described as an example of an electrically driven work vehicle, but the present invention can also be applied to other electrically driven working vehicles having wheels such as a wheel loader. It is possible to apply the invention.

FIG. 1 is a side view schematically showing the appearance of a dump truck, which is an example of an electrically driven work vehicle according to the present embodiment.

In FIG. 1, a dump truck 100 includes a body frame 18 that extends in the front-rear direction and forms a support structure, and is arranged on the upper part of the body frame 18 so as to operate in the front-rear direction, and the lower part of the rear end is connected to a pin joint. A loading platform (vessel) 7 that is tiltably provided on the vehicle body frame 18 via 7a, a pair of driven wheels 4L (4R) provided on the lower front left and right sides of the vehicle body frame 18, and a pair of driven wheels 4L (4R) provided on the lower rear left and right sides of the vehicle body. A pair of drive wheels 5L (5R) provided on the vehicle body frame 18, a driver's seat 6 provided on the upper front side of the vehicle body frame 18, an engine 1 (for example, a diesel engine) disposed on the vehicle body frame 18, and a vehicle driven by the engine 1. The main generator 2 (see FIG. 2 later) drives the wheels (drive wheels 5L, 5R) using electric power, and the electric drive system includes electric drive motors 3L, 3R, etc. There is. In FIG. 1, only one of a pair of left and right driven wheels and driving wheels is shown and given a reference numeral, and the other is shown in parentheses only and not shown.

FIG. 2 is a diagram schematically showing a part of the electric drive system along with its peripheral components.

In FIG. 2, the electric drive system includes a main generator 2 and an auxiliary generator 14 driven by an engine 1, a rectifier 8 that rectifies the current (AC power) output from the main generator 2, and a rectifier 8 that rectifies the current (AC power) output from the main generator 2. The electric power supplied from the main generator 2 via the rectifier 8 and the inverter 9 is used. electric motors 3L and 3R for driving drive wheels 5L and 5R (wheels), an auxiliary rectifier 11 that rectifies the current (AC power) output from an auxiliary generator 14, and auxiliary equipment such as a cooling blower. an auxiliary motor 13, an auxiliary inverter 12 that converts the current (DC current) rectified by the auxiliary rectifier 11 into an AC power drive signal, and supplies it to the auxiliary motor 13 (auxiliary equipment); Conversion of power between the circuit downstream of the rectifier 8 on the generator 2 side (hereinafter referred to as the main circuit) and the circuit downstream of the auxiliary rectifier 11 on the auxiliary generator 14 side (hereinafter referred to as the auxiliary circuit) and a DC-DC converter 10 (hereinafter also referred to as a regeneration device) that performs transfer and reception, a secondary battery 17 that stores power of the auxiliary circuit, and a secondary battery 17 that converts power between the auxiliary circuit and the secondary battery 17. A bidirectional converter 16 that controls the storage (charging) and discharging of the secondary battery 17, an external resistor 15 that consumes surplus power on the main circuit side as necessary, and the overall operation including the regenerative operation of the electric drive system. It generally includes a regeneration control device 20 for controlling. The dump truck 100 is equipped with multiple sets of cooling blowers (auxiliary inverter 12 and auxiliary motor 13) as auxiliary equipment, but in FIG. 2, one set of auxiliary equipment is shown for simplicity. Only the device is illustrated.

The DC-DC converter 10 converts (steps down) power on the main circuit side, such as regenerative power generated by the driving electric motors 3L and 3R when the dump truck 100 is braked, and supplies it to the auxiliary circuit side, and supplies it to the auxiliary circuit side. It is used to drive the auxiliary motor 13 via. This makes it possible to use the regenerated electric power generated during braking of the dump truck 100 to drive the auxiliary equipment, thereby reducing fuel consumption accordingly.

In addition, the DC-DC converter 10 converts (steps down) power on the main circuit side, such as regenerative power generated by the driving electric motors 3L and 3R when braking the dump truck 100, and supplies it to the auxiliary circuit side. Power is stored in the secondary battery 17 via the converter 16. The electric power stored in the secondary battery 17 is supplied to the auxiliary equipment during operations other than the regeneration of the traveling electric motors 3L and 3R (for example, the power operation of the dump truck 100). That is, in this embodiment, a portion of the surplus power that is generated by the traveling electric motors 3L and 3R and is not used for driving the auxiliary equipment is not consumed by the external resistor 15. It is collected and stored in the secondary battery 17, and is supplied to the auxiliary equipment except when the traveling electric motors 3L and 3R are regenerated. This can further improve overall energy efficiency and reduce fuel consumption.

Here, the basic principle of setting the power capacity of the secondary battery and setting the timing of power assist in this embodiment will be explained.

First, the setting of the power capacity of the secondary battery 17, which is the object of this embodiment, will be explained.

Hybrid systems installed on electrically driven work vehicles such as dump trucks include systems that are equipped with a storage device of a relatively large capacity and can run only on electricity (so-called strong hybrid type), and systems that use an electric energy source. This is a system that mainly uses regenerated energy to assist the engine and drive auxiliary equipment, that is, a system that does not assume that the vehicle will be driven solely by the power supply from the power storage device (the so-called mild hybrid type). ) is known.

Generally speaking, the regenerative power of the driving electric motor of large dump trucks operating in mines etc. is approximately several thousand kW, whereas the power required for auxiliary equipment is approximately 100 kW. The difference in size is an order of magnitude. Therefore, the regenerated power of the dump truck is larger than the power required by the auxiliary equipment, and cannot be absorbed by simply supplying power to the auxiliary equipment via the regeneration device when braking the vehicle. Therefore, by consuming a portion of the regenerated power with an external resistor, the regenerated power that is surplus to the power supply to the auxiliary device is handled.

In large dump trucks, by installing a secondary battery in the output section of the regeneration device, a portion of the power consumed by the external resistor is charged into the secondary battery, and the power is utilized when the vehicle is running. It is possible to do so. However, for the dump truck 100 targeted in this embodiment, the amount of cargo transported is the most important basic performance index, so the more batteries that are heavy, the more the cost not only increases, but also the basic performance This results in a loss of conveyance amount.

Therefore, in this embodiment, a relatively small secondary battery that is considered to exhibit the most cost performance when applied to a dump truck, that is, a secondary battery with a relatively small battery capacity is mounted.

Next, setting of the timing of power assist will be explained.

In the present embodiment, the driving pattern of the dump truck 100 at the work site is defined on a time axis, and the driving pattern is determined based on the fuel efficiency of the engine 1. The secondary battery 17 is discharged according to the timing of discharging the secondary battery 17 (first discharge section) and the amount of energy consumed by the dump truck 100. The timing (second discharge period) is set. Here, the first and second discharge sections are sections (i.e., periods) defined based on the elapsed time from a predetermined timing (for example, the start of travel in a cycle of transportation work), and The start and end of the second discharge section are respectively defined based on the elapsed time. In the following explanation, the case where the first and second discharge sections in which electric power assist is performed as described above are defined by time will be explained as an example. The discharge section may be set between specific positions in the discharge section.

First, a case will be described in which the timing (first discharge period) for performing electric power assist is set according to the fuel consumption rate [g/kWh] (hereinafter also referred to as fuel efficiency) of the engine 1.

FIG. 3 is a diagram showing an example of the fuel efficiency characteristics of a diesel engine, and is an equal fuel efficiency map where the vertical axis shows the torque [N・m] of the diesel engine and the horizontal axis shows the rotation speed [rpm] of the diesel engine. The fuel efficiency characteristics are shown as follows.

As shown in FIG. 3, the fuel efficiency characteristics of a diesel engine tend to be such that as the output (torque×rotation speed) increases, the fuel efficiency improves, and as the output decreases, the fuel efficiency decreases. In order to improve the fuel efficiency of diesel engines, it is effective to drive auxiliary equipment by supplying electricity from the secondary battery (hereinafter referred to as power assist) in regions where fuel efficiency is poorer (in which output is smaller). It is.

Therefore, in the present embodiment, the first discharge (power assist) for discharging from the secondary battery 17 takes into account the timing when the engine 1 (diesel engine) is operating in a region with a smaller output. Set the interval.

Next, a case will be described in which the timing (first discharge section) for performing electric power assist is set according to the energy consumption of the dump truck 100.

FIG. 4 is a diagram showing the driving pattern of a dump truck at a mine, which is an example of a work site, as a change in vehicle speed. The vertical axis represents vehicle speed [km/h], and the horizontal axis represents time [h]. It shows.

As shown in FIG. 4, changes in the vehicle speed of the dump truck 100 at the mine repeat almost the same traveling pattern. For example, a dump truck 100 in a mine repeatedly moves to a loading location and loads the cargo, and moves to a discharge location and discharges the cargo. During this time, the dump truck 100 repeatedly goes up and down the slope of the mine and accelerates and decelerates, so the traveling electric motors 3L and 3R repeat power operation and regeneration operation. Regenerative power used in power assist is obtained through regenerative operation.

FIG. 5 is a diagram showing an example of the change in charge amount (charge/discharge characteristics) in the driving pattern shown in FIG. 4, with the vertical axis representing the charge amount [kwh] of the secondary battery and the horizontal axis representing time [h]. are shown respectively.

FIG. 5 shows the charging of the secondary battery when the dump truck travels in the driving pattern shown in FIG. It shows the change in amount (charge/discharge characteristics). In this case, charging and discharging are almost completed in the initial section of the driving pattern, and considering the overall energy balance, there is a possibility of further improvement.

FIG. 6 is a diagram showing an example of changes in the fuel consumption rate of the engine in the driving pattern shown in FIG. 4, with the vertical axis showing the fuel consumption rate [g/kwh] and the horizontal axis showing time [h]. There is.

The driving pattern of the dump truck shown in Fig. 4 exhibits characteristics that include two types of sections: sections where the vehicle speed is high and the output is considered to be relatively large, and sections where the vehicle speed is low and the output is considered to be relatively small. Correspondingly, FIG. 6 also shows a characteristic in which there are sections where the fuel consumption rate is good and sections where the fuel consumption rate is poor.

Here, as shown in Fig. 5, if the secondary battery is discharged in such a way that charging and discharging are almost completed during the initial period of the driving pattern, the fuel efficiency of the engine is good in the section shown in Fig. 6. In this case, electric power assist is performed from the secondary battery, and it is thought that the contribution of electric power assist to improving fuel efficiency is not large. In other words, in Figure 6, while suppressing the implementation (discharging) of electric power assist in the more fuel efficient sections seen in the first half of the driving pattern, it is possible to suppress the implementation (discharge) of electric power assist in the more fuel efficient sections seen in the latter half of the driving pattern. By carrying out this process (discharging), further reductions in fuel consumption can be expected.

This embodiment aims at reducing fuel consumption by setting the first and second discharge sections based on the above knowledge. In other words, when focusing only on the fuel efficiency of the engine, it is important to charge the regenerative power obtained from the electric braking of the electric motor for driving into a secondary battery and use this power to assist the electric drive unit. It is desirable to implement electric power assist in sections where fuel efficiency is poor. However, diesel engines generally have a characteristic of poor fuel efficiency in the low output range, so if you set the power assist interval by considering only the engine's fuel efficiency, it will not be possible to use up all of the regenerated power recovered in the secondary battery. This leaves room for further reductions in fuel consumption. Therefore, as shown in Fig. 6, in a dump truck driving pattern that has two types of sections, one with relatively good engine fuel efficiency and the other with relatively poor fuel efficiency, regardless of whether the fuel efficiency is good or bad, The second discharge section is a section in which the secondary battery is discharged (power assist) and adjusted to balance charging and discharging in the driving cycle of the dump truck (hereinafter also referred to as "other discharge section"). Set.

As described above, in this embodiment, the first discharge section is set according to the fuel consumption of the engine 1, and the second discharge section is set in which discharge is performed regardless of the fuel consumption, thereby reducing the fuel consumption. can be further reduced.

FIG. 7 is a functional block diagram showing the processing contents of a functional unit related to a discharge section determination process that determines a discharge section among the processing functions of the regeneration control device.

In FIG. 7, the regeneration control device 20 includes an engine fuel efficiency point threshold adjustment unit 21, a driving pattern generation unit 22, and a secondary battery charge/discharge balance information calculation unit as functional units related to the discharge interval determination process that determines the discharge interval. 23, and a battery discharge section determining section 24.

The engine fuel efficiency point threshold adjustment unit 21 sets a fuel efficiency threshold for use in determining the first discharge interval based on engine fuel efficiency information acquired from the ECU 1a that controls the operation of the engine 1, and the battery discharge interval determination unit Output to 24.

The driving pattern generation unit 22 uses position information (traveling point information) of the dump truck 100 acquired from a GNSS (Global Navigation Satellite System) (not shown) provided in the dump truck 100, and GNSS and inclination information (not shown). Based on slope information of the dump truck 100 acquired from sensors etc., vehicle speed information of the dump truck 100 acquired via CAN communication etc., and running torque information calculated based on information from the ECU 1a etc. By generating the latest running pattern of the truck 100 at the work site and outputting it as a running pattern signal to the battery discharge section determining section 24, the running pattern used for processing in the battery discharging section determining section 24 is updated.

The secondary battery charging/discharging balance information calculation unit 23 calculates the amount of electricity during a predetermined period (for example, one cycle of the driving pattern of the dump truck 100) based on information regarding the current and voltage (current/voltage information) acquired from the secondary battery 17. Information indicating the balance of power charged and discharged by the secondary battery 17 (secondary battery charging/discharging balance information) is generated and output to the battery discharge section determination unit 24 . Note that one cycle of the driving pattern of the dump truck 100 at a work site such as a mine is, for example, from a reference point on the running path of the dump truck 100 to a loading position for loading earth and sand, and a discharge position for discharging earth and sand. This is a series of running motions until returning to . However, the reference point may be provided at the loading position or the earth releasing position, or one cycle may be a traveling operation that passes through the loading position or the earth releasing position a plurality of times.

The battery discharge section determining unit 24 uses engine fuel efficiency information acquired from the ECU 1a, a fuel efficiency threshold from the engine fuel efficiency point threshold adjusting unit 21, a driving pattern acquired as a driving pattern signal from the driving pattern generating unit 22, and a secondary battery. Based on the secondary battery charging/discharging balance information acquired from the charging/discharging balance information calculation unit 23, two types of discharge intervals, first and second discharge intervals, are determined, and a signal for permitting discharge of the secondary battery 17 is generated. (discharge permission signal) is output to the bidirectional converter 16 only in the first and second discharge sections. The bidirectional converter 16 discharges the secondary battery 17 only while the discharge permission signal is output from the battery discharge interval determination unit 24 in the first and second discharge intervals, and in other cases discharges the secondary battery 17. Charge the battery.

Note that, in reality, the driving pattern at a work site such as a mine where the dump truck 100 operates can be roughly predicted in advance before the dump truck 100 is introduced. The initial value of the driving pattern generated by the driving pattern generating section 22 can be set in advance based on the predicted driving pattern, and the initial value of the driving pattern generated by the driving pattern generating section 22 can be set in advance based on the predicted driving pattern. The initial values of the two types of discharge sections can also be provisionally set when the dump truck 100 is initially installed at the site.

FIG. 8 is a flowchart showing the processing contents of the discharge section determination process in the regeneration control device.

In FIG. 8, the regeneration control device 20 first collects information used by the engine fuel efficiency point threshold adjustment unit 21 and the battery discharge interval determination unit 24 (information on engine fuel efficiency and fuel consumption [l/h]), and the driving pattern generation unit 22. (step S100) . Note that the various information acquired in step S100 is sequentially updated, for example, in the minimum processing cycle of the arithmetic device that constitutes the regeneration control device 20, regardless of the cycle of the discharge section determination process.

After acquiring various information in step S100, it is then determined whether the engine fuel consumption [l/h] has improved compared to the previous cycle (step S110).

If the determination result in step S110 is YES, that is, if it is determined that the engine fuel consumption has improved compared to the previous cycle, it is determined that there is room for further improvement (improvement amount), The first discharge section is adjusted by lowering the engine fuel efficiency threshold by a predetermined value (step S111), and then the second discharge section is adjusted (secondary Adjustments are made to match the charge/discharge balance of the battery 17 (step S120), and the process ends. Such processing in step S111 increases the power energy discharged from the secondary battery 17 in the first discharge section, and as a result, it is possible to increase the fuel reduction effect.

In addition, if the determination result in step S110 is NO, that is, if it is determined that the engine fuel consumption has not improved (in other words, has deteriorated) from the previous cycle, the second half of the driving pattern It is determined that there is a section with poor fuel efficiency and that it is necessary to limit the discharge from the secondary battery 17 in the first discharge section, and the engine fuel efficiency threshold is increased by a predetermined value to adjust the first discharge section. (Step S112), and then, in accordance with the adjustment of the engine fuel efficiency threshold in Step S112, the second discharge section is adjusted (adjusted to match the charging and discharging balance of the secondary battery 17) (Step S120), Finish the process. Such processing in step S112 reduces the power energy discharged from the secondary battery 17 in the first discharge period, and as a result, it is possible to increase the fuel consumption reduction effect.

Note that the adjustment width of the engine fuel efficiency threshold in steps S111 and S112 can be set as appropriate in consideration of the amount of change in the fuel consumption rate of the dump truck 100; Let the fuel consumption rate [g/kwh] be the change value for each cycle of the fuel consumption threshold.

The regeneration control device 20 repeats the processing of steps S100 to S120 every cycle as the discharge section determination processing. As a result, the combination of the first and second discharge sections that provides the minimum (best) fuel consumption of the engine is set.

FIG. 9 is a diagram showing an example of a case where a fuel consumption threshold is set for the transition of the fuel consumption rate of the engine in the driving pattern shown in FIG. 4, and first and second discharge sections are set. The rate [g/kwh] is shown on the horizontal axis, and the time [h] is shown on the horizontal axis.

As shown in FIG. 9, when the engine fuel efficiency threshold of this embodiment is set and the first and second discharge periods are set, the secondary battery discharge (power assist) is applied to the auxiliary equipment accordingly. Implemented.

FIG. 10 shows the change in the amount of charge (charging and discharging characteristics) when the engine fuel efficiency threshold is set as shown in FIG. 9 in the driving pattern shown in FIG. 4, and the first and second discharge sections are set. It is a figure showing an example, and the vertical axis shows the charge amount [kwh] of the secondary battery, and the horizontal axis shows time [h].

As shown in FIG. 10, the charging/discharging characteristics of the secondary battery 17 in the present embodiment are such that the regenerative power obtained by braking the vehicle is used for powering the next vehicle without applying the control according to the present embodiment. Compared to the charging/discharging characteristics when the battery is immediately discharged (see Figure 5), the amount of charge in the secondary battery 17 remains until the latter half of the driving pattern, and the discharge during the section with poor engine fuel efficiency in the latter half of the driving pattern. It can be confirmed that (power assist) is being performed. Furthermore, since the charging and discharging balance per cycle is adjusted, fuel consumption can be reduced by using electric energy efficiently. As described above, in the present embodiment, the driving pattern of the dump truck 100 is repeatedly calculated according to the situation at the work site, and the engine fuel efficiency threshold (first discharge section) and the second discharge section are set accordingly. By setting this, it becomes possible to reduce engine fuel consumption by utilizing regenerated power.

Note that although FIG. 10 illustrates the charging and discharging characteristics (charging and discharging balance) per cycle of the driving pattern based on the state where the charge amount is 0 (zero), in reality, the charging and discharging characteristics (charging and discharging balance) of the secondary battery Considering the influence of deterioration during charging and discharging in No. 17, it is desirable to operate the battery by setting the reference point to about 50% of the fully charged amount, or by setting the average value in one cycle to about 50%.

The effects of this embodiment configured as described above will be explained using a comparative example.

FIG. 12 is a diagram schematically showing a part of an electric drive system shown as a comparative example along with its peripheral configuration.

In FIG. 12, the electric drive system of the comparative example includes a main generator 2 and an auxiliary generator 14 driven by an engine 1, a rectifier 8 that rectifies the current (AC power) output from the main generator 2, and a rectifier An inverter 9 converts the rectified current (DC power) into an AC power drive signal and supplies it to the driving electric motors 3L and 3R, and a current is supplied from the main generator 2 via the rectifier 8 and the inverter 9. A driving electric motor 3L, 3R that uses electric power to drive drive wheels 5L, 5R (wheels), an auxiliary rectifier 11 that rectifies the current (AC power) output from an auxiliary generator 14, a cooling blower, etc. An auxiliary motor 13 that is an auxiliary device, and an auxiliary inverter 12 that converts the current (DC current) rectified by the auxiliary rectifier 11 into an AC power drive signal and supplies it to the auxiliary motor 13 (auxiliary device). It has roughly the following.

When applying the electric drive system of the comparative example shown in Fig. 12 to a dump truck operated at a work site such as a mine, it is necessary to use a highly efficient electric motor and drive the engine at an operating point with high combustion efficiency. Therefore, a reduction in fuel consumption can be expected. However, in this electric drive system, the external resistor 15 consumes regenerative power when electric braking force is generated by the electric motor for traveling on slopes (downhill slopes) that exist in many work sites such as mines. However, further improvements were a challenge.

Another conventional technology to solve this problem is to install a relatively large capacity secondary battery, store power from a generator driven by the engine in the secondary battery, and use it to perform tasks such as when a vehicle runs uphill. BACKGROUND ART When large engine power is required, devices have been devised to reduce fuel consumption by supplying power from a secondary battery. On the other hand, if the capacity of the installed secondary battery is limited, such as in a system where the purpose is to drive auxiliary equipment using regenerated power generated by the electric motor for driving, it is necessary to secure the capacity of the secondary battery. Although the required cost is suppressed, even if the above-mentioned conventional technology is applied, the effect of reducing fuel consumption may be limited.

On the other hand, in this embodiment, the engine 1, the main generator 2 and the auxiliary generator 14 driven by the engine, and the driving electric motors 3L and 3R driven by the electric power supplied from the main generator. , the auxiliary equipment (for example, the auxiliary inverter 12 and the auxiliary motor 13 that constitute the cooling blower) driven by the electric power supplied from the auxiliary generator, and the regenerative power generated when the vehicle is braked by the electric motor for driving are used as the auxiliary equipment. It includes a regeneration device (for example, a DC-DC converter 10) that supplies the device, and a battery (for example, a secondary battery 17) that can store electric power supplied to the auxiliary equipment from the regeneration device and the auxiliary generator. In the electrically driven work vehicle (for example, the dump truck 100), the regeneration device includes a first discharge section in which the battery is discharged according to the fuel efficiency of the engine, based on the driving pattern of the electrically driven work vehicle and the fuel consumption rate of the engine. and a second discharge period in which the battery is discharged according to the amount of energy consumption of the vehicle, and a discharge period from the battery to the auxiliary equipment or the electric motor for driving is determined based on the first and second discharge periods. Since the configuration is configured to supply electric power, fuel consumption can be further reduced when the capacity of the secondary battery is relatively small.

FIG. 11 is a diagram illustrating the improvement status of the fuel consumption rate and fuel consumption amount of this embodiment over the conventional technology. The left vertical axis shows the fuel consumption rate [g/kwh], and the right vertical axis shows the fuel consumption amount. [l] (integrated amount) is shown on the horizontal axis, and time [h] is shown on the horizontal axis.

As shown in FIG. 11, in this embodiment, in sections a and c (sections with high (poor) fuel consumption rates), electric power is assisted from the secondary battery 17 to the auxiliary equipment. Fuel consumption can be further reduced compared to the previous model. On the other hand, in the present embodiment, in section b (section where the fuel consumption rate is low), power assistance is not provided from the secondary battery 17 to the auxiliary equipment, so that the amount of fuel per unit time is higher than in the conventional technology. Consumption will increase slightly. However, since section b is a section where the fuel consumption rate is low (good), the amount of increase in fuel consumption per unit time is small. The total fuel consumption in sections a, b, and c can be reduced compared to the conventional technology.

<Additional notes>
Note that the present invention is not limited to the above-described embodiments, and includes various modifications and combinations within the scope of the invention. Furthermore, the present invention is not limited to having all the configurations described in the above embodiments, but also includes configurations in which some of the configurations are deleted. Moreover, each of the above-mentioned configurations, functions, etc. may be realized in part or in whole by, for example, designing an integrated circuit. Furthermore, each of the above configurations, functions, etc. may be realized by software by a processor interpreting and executing a program for realizing each function.

For example, in the present embodiment, an auxiliary device such as a cooling blower is illustrated as a power supply destination for discharging a secondary battery (power assist), but the present invention is not limited to this, and for example, a regeneration device (DC-DC converter) By making 10) a bidirectional DC-DC converter, it is also possible to supply electric power to the traveling electric motors 3L and 3R during discharge of the secondary battery (power assist), and in such a case, By increasing the capacity of the secondary battery, the fuel efficiency improvement effect can be further expanded.

1... Engine, 2... Main generator, 3L, 3R... Electric motor for traveling, 4L, 4R... Driven wheel, 5L, 5R... Driving wheel, 6... Driver's seat, 7... Loading platform (vessel), 7a... Pin connection part , 8... Rectifier, 9... Inverter, 10... DC-DC converter, 11... Auxiliary rectifier, 12... Auxiliary inverter, 13... Auxiliary motor, 14... Auxiliary generator, 15... External resistor, 16... Bidirectional Converter, 17... Secondary battery, 18... Vehicle body frame, 20... Regeneration control device, 21... Engine fuel efficiency point threshold adjustment section, 22... Driving pattern generation section, 23... Secondary battery charge/discharge balance information calculation section, 24... Battery Discharge section judgment unit, 100...dump truck

Claims (4)

engine and
a main generator and an auxiliary generator driven by the engine;
a traveling electric motor driven by electric power supplied from the main generator;
an auxiliary device driven by electric power supplied from the auxiliary generator;
a regeneration device that supplies regenerative power generated by the traveling electric motor when the vehicle is braked to the auxiliary device;
An electric drive working vehicle comprising: a battery capable of storing electric power supplied from the regeneration device and the auxiliary generator to the auxiliary device;
The regeneration device is
Based on the driving pattern of the electric drive work vehicle and the fuel consumption rate of the engine,
a first discharging section in which a section in which the battery is discharged according to a fuel consumption rate of the engine is defined by a traveling section or time of the electric drive vehicle;
determining a section in which the battery is discharged according to the magnitude of energy consumption of the vehicle as a traveling section of the electrically driven vehicle or a second discharging section defined by time;
An electrically driven work vehicle characterized in that electric power is supplied from the battery to the auxiliary device or the traveling electric motor based on the first and second discharge sections. The electrically driven work vehicle according to claim 1,
The regeneration device is
Repeatedly calculating the driving pattern and the fuel consumption amount of the engine,
determining the discharge timing of the battery so that the fuel consumption of the engine in the driving pattern is minimized;
An electrically driven work vehicle characterized in that power is supplied from the battery to the auxiliary device based on the discharge timing. The electrically driven work vehicle according to claim 1,
The regeneration device is
determining a section in which the fuel consumption rate of the engine is greater than a predetermined fuel efficiency threshold as the first discharge section;
The electrically driven working vehicle is characterized in that the second discharge section is determined so that energy consumption of the electrically driven working vehicle is balanced in a travel cycle. The electrically driven work vehicle according to claim 3,
The regeneration device is
After determining the first discharge section by adjusting the fuel efficiency threshold so that the fuel consumption of the engine in the driving pattern is small,
The electrically driven working vehicle is characterized in that the second discharge section is determined so that energy consumption of the electrically driven working vehicle is balanced in a travel cycle.

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