Construction machinery

Abstract

To shorten execution time of warm-up operation and, as a result, shorten charging time of a power storage device.SOLUTION: The construction machine includes an electric motor that drives a hydraulic pump, a power storage device that supplies electric power to the electric motor, a charger that charges the power storage device, and a control device that controls the charger. Based on at least a temperature of the power storage device, the control device determines whether to perform a warm-up operation in which charging and discharging of the power storage device are repeated. Then, the control device performs warm-up operation by changing the magnitude of a charging current and a discharging current during warm-up operation according to a relation between the temperature of the power storage device and a charging rate of the charger.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to construction machinery.

Background Art

[0002] In recent years, from the perspective of suppressing global warming, the electrification of automobiles has been rapidly progressing, and electrification has also begun to progress mainly in Europe in construction machinery. As a power source for an electric motor, which is a drive source enabling electrification, a power storage device is mainly used as in automobiles.

[0003] Since electric construction machinery is used in a harsh environment exposed to the outside air, the power storage device is greatly affected by the external environment. In order to supply power from the power storage device to the electric motor, it is necessary to previously store power in the power storage device.

[0004] Due to the characteristics of the power storage device, there is a limit to the allowable current value that can flow through the power storage device, and this allowable current value further decreases at low temperatures. Since a sufficient current value cannot flow during charging, there is a problem that the charging time becomes long. Therefore, by performing a warm-up operation to warm the power storage device, the allowable current value is increased, and thereby the charging time is shortened. The warm-up operation is, for example, executed by intentionally repeating charging and discharging of the power storage device. The power storage device can be warmed by the heat generated by the charge and discharge current during the warm-up operation (see, for example, Patent Documents 1 and 2).

[0005] However, in the prior art, it only determines whether or not to execute the warm-up operation according to the detected temperature, and the execution time of the warm-up operation cannot be sufficiently shortened.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention provides a construction machine capable of shortening the execution time of a warm-up operation and, as a result, shortening the charging time of a power storage device.

Means for Solving the Problems

[0008] To solve the above problems, a construction machine according to the present invention includes an electric motor that drives a hydraulic pump, a power storage device that supplies power to the electric motor, a charger that charges the power storage device, and a control device that controls the charger. The control device determines whether to execute a warm-up operation in which charging and discharging of the power storage device are repeated based on at least the temperature of the power storage device. Then, the control device executes the warm-up operation by changing the magnitudes of the charging current and the discharging current during the warm-up operation according to the relationship between the temperature of the power storage device and the charging rate of the charger.

Effects of the Invention

[0009] According to the present invention, it is possible to provide a construction machine capable of shortening the execution time of a warm-up operation and, as a result, shortening the charging time of a power storage device.

Brief Description of the Drawings

[0010]

Figure 1

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Figure 7

Mode for Carrying Out the Invention

[0011] Hereinafter, this embodiment will be described with reference to the accompanying drawings. In the accompanying drawings, functionally identical elements may sometimes be denoted by the same reference numerals. Note that the accompanying drawings show embodiments and implementation examples in accordance with the principles of the present disclosure, but these are for the purpose of understanding the present disclosure and are not used to limit the interpretation of the present disclosure in any way. The description in this specification is merely a typical example and does not limit the scope of the claims or application examples of the present disclosure in any sense.

[0012] In this embodiment, although the description is made in sufficient detail for those skilled in the art to implement the present disclosure, other implementations and forms are possible, and it is necessary to understand that changes in configuration and structure and replacement of various elements can be made without departing from the scope and spirit of the technical idea of the present disclosure. Therefore, the following description should not be construed as being limited thereto.

[0013] As shown in the external structure diagram of FIG. 1, the construction machine 10 of this embodiment is, for example, a hydraulic excavator, and includes, for example, an upper revolving structure 1110, a lower traveling structure 1120, a working machine 1130, a slewing mechanism 1140, and a cylinder 1160.

[0014] The upper revolving structure 1110 is a part of the vehicle body that is rotatably attached to the upper part of the lower traveling structure 1120 via a slewing mechanism 1140, and is provided with a cab 1111 for an operator to perform driving. The cab 1111 is provided with a door D that can be partitioned and opened / closed from the outside. The door D is configured to be lockable with a physical key.

[0015] The upper swing body 1110 swings with respect to the lower traveling body 1120 about a rotation axis parallel to the height direction of the construction machine 10. The upper swing body 1110 houses, for example, a hydraulic pump and a hydraulic control device. The lower traveling body 1120 includes, for example, crawlers 1121 driven by a hydraulic pump (not shown) and travels the construction machine 10 under the control of the control device. As will be described later, this construction machine 10 also incorporates a motor that drives this hydraulic control device, a power storage device that supplies power to the motor, and other electrical systems.

[0016] The working machine 1130 is provided, for example, at the front of the upper swing body 1110 and is driven by a cylinder 1160 to perform operations such as excavation work. The working machine 1130 has, for example, a boom 1131, an arm 1132, and a bucket 1133. The swing mechanism 1140 has a hydraulic motor (not shown) and swings the upper swing body 1110 with respect to the lower traveling body 1120 about a rotation axis parallel to the height direction of the construction machine 10 under the control of the hydraulic control device.

[0017] Generally, the construction machine 10 supplies power to various movable parts with a hydraulic pump or the like. Such a hydraulic pump or the like is connected to an electric motor, and the hydraulic pump is rotated by the power from the electric motor to generate pressure. The opening and closing degree of the solenoid of the hydraulic valve is adjusted to operate various movable parts. The opening and closing degree of the solenoid can be operated with an operation lever or a pedal in the driver's seat.

[0018] With reference to the block diagram of FIG. 2, a configuration example of an electric motor that drives a hydraulic control device and an electrical system that supplies power to the electric motor provided in the construction machine 10 will be described. In FIG. 2, power lines for supplying power are shown by solid lines, and communication signal lines for transmitting and receiving control signals and the like are shown by dotted lines.

[0019] This construction machine 10 includes an electric motor (motor) 2 that drives a hydraulic control device 1, an inverter 3 for controlling the electric motor 2, a high-voltage power storage device 4 that supplies power to the electric motor 2 via the inverter 3, and a charger 5 that charges the high-voltage power storage device 4. Further, a controller 6 (control device) is provided to control these devices and to control, monitor, and protect the overall operation of the electrical system. Furthermore, a junction box 9 is provided for making electrical connections between these devices. The junction box 9 provides a dustproof and waterproof function for the connection of various devices and is equipped with OCP (Over current protection) such as relays and fuses from the perspective of protection against misuse and failure.

[0020] As described above, there is a limit to the allowable current value that can flow through the power storage device 4, and the value of this allowable current (discharge current, charge current) further decreases at low temperatures. Therefore, the power storage device 4 of the present embodiment is configured to be able to perform a warm-up operation by repeatedly charging and discharging at low temperatures. The determination of whether to execute the warm-up operation is made by the controller 6 based on the temperature of the power storage device 4. Note that the necessity of executing the warm-up operation may be determined taking into account not only the temperature of the power storage device 4 but also other determination factors. As will be described later, the values of the charge current and discharge current in the warm-up operation are appropriately updated according to changes in the situation.

[0021] A power conversion device 7 is connected to the power storage device 4 via the junction box 9. The power conversion device 7 converts the voltage supplied from the power storage device 4 and generates a control voltage for each device. A low-voltage (e.g., 12 / 24V) power storage device 8 is connected to the power conversion device 7.

[0022] The low-voltage power storage device 8 generates a control voltage for controlling each device. Further, various warning lights are installed on the construction machine 10. The power storage device 8 is provided as a power storage device for supplying the low voltage used for such warning lights and the like.

[0023] Inverter 3 converts the DC power output by the power storage device 4 into AC power in order to control the motor 2 at an arbitrary rotational speed. In order for the power storage device 4 to supply power, it is necessary to store power in advance. The charger 5 is connected to the utility power supply equipment and charges the power storage device 4 under the control of the controller 6.

[0024] Inside the power storage device 4, a current sensor 11 as a current measurement unit for measuring the current flowing through the power storage device 4, a voltage sensor 12 as a voltage measurement unit for measuring the voltages of the battery cells constituting the power storage device 4, and a temperature sensor 13 as a temperature measurement unit for measuring the temperatures of the battery cells of the power storage device 4 are respectively attached.

[0025] Each of the various sensors 11 to 13 may be provided in plurality in one power storage device 4. When a plurality of the same type of sensors are provided in one power storage device 8, the measured values can be output as an average value, a maximum value, a minimum value, a median value, etc. The controller 6 calculates the power storage amount of the power storage device 8 according to the current, voltage, temperature, etc. measured by the various sensors 11 to 13, and further calculates the state of charge (SOC) from the power storage amount.

[0026] With reference to FIGS. 3 and 4, the relationship between the state of charge (SOC) and the allowable current during charging and discharging of the power storage device 4 will be described. The allowable current means the current that the power storage device 4 can pass under certain conditions.

[0027] As shown in FIGS. 3 and 4, it can be seen that when the power storage device 4 is at a high temperature, the allowable current of the charging current and the allowable current of the discharging current are larger than those at a low temperature.

[0028] Also, as shown in FIGS. 3 and 4, when the power storage device 4 is at a low temperature, the allowable current of the discharge current increases as the charge rate (SOC) increases. On the other hand, as shown in FIG. 3, when the power storage device 4 is at a low temperature, the increase in the allowable current of the charge current is minute with respect to the increase in the charge rate (SOC). Considering that more heat generation can be promoted by flowing a large current, when performing charge and discharge as the warm-up operation of the power storage device 4, it is desirable that the temperature be raised to about normal temperature (up to about 25° C.), and it is desirable that the charge rate (SOC) be maintained high.

[0029] As can be seen from FIGS. 3 and 4, the allowable current during charging and discharging of the power storage device 4 varies depending on the charge rate (SOC) of the power storage device 4 and also varies depending on the temperature of the power storage device 4. Therefore, in the present embodiment, according to the combination of the charge rate (SOC) of the power storage device 4 and the temperature T of the power storage device 4, the value x of the charge current and the value y of the discharge current during the warm-up operation are determined, and according to the determined values x and y, the warm-up operation of the power storage device 4 is controlled. The controller 6 sequentially calculates or measures the charge rate SOC and the temperature T, and sets a charge current and a discharge current suitable for the calculated or measured charge rate (SOC) and temperature T to execute the warm-up operation.

[0030] As an example, the controller 6 includes a table for determining the values x and y of the charge current during the warm-up operation as shown in FIG. 5. This table stores the value x of the charge current and the value y of the discharge current for each combination of the charge rate (SOC) of the power storage device 4 and the temperature T of the power storage device. The controller 6 refers to the table based on the calculated charge rate (SOC) and the measured temperature T of the power storage device 4, determines the value x of the charge current and the value y of the discharge current, and controls the warm-up operation. Note that the discharge power based on the discharge current during the warm-up operation can be regenerated to the power source that supplies the charging power to the charger 5.

[0031] In the table of FIG. 5, for each combination of the state of charge (SOC) and temperature T, the values of the charging current x (x11, x12, ··· x99) and the values of the discharging current y (y11, y12, ··· y99) are determined. However, in any combination, the value of the charging current x is set to be larger than the value of the discharging current y. The values of x and y are appropriately updated during the warm-up operation, but the relationship x > y is always maintained according to the stored values in the table of FIG. 5. By maintaining the relationship x > y during the warm-up operation, the state of charge (SOC) increases monotonically during the execution of the warm-up operation. The higher the state of charge (SOC), the larger the allowable current, and accordingly, the values of x and y can be set to larger values. Therefore, maintaining the relationship x > y is preferable for shortening the charging time of the power storage device 4. However, depending on the operating conditions, a time period during which x ≤ y may be set in part.

[0032] In the table of FIG. 5, it is preferable that the values of x and y are set such that the ratio of the value of the charging current x to the value of the discharging current y increases as the state of charge (SOC) increases. Thereby, the ratio of the charging current to the discharging current during the warm-up operation is increased as the state of charge (SOC) increases, and thereby, the charging time of the power storage device 4 can be shortened. Also, in the table of FIG. 5, it is preferable that the values of x and y are set such that the ratio of the value of the charging current x to the value of the discharging current y increases as the temperature T increases. Thereby, the ratio of the charging current to the discharging current during the warm-up operation is increased as the temperature T increases, and thereby, the charging time of the power storage device 4 can be shortened.

[0033] With reference to the flowchart of FIG. 6 and the graph of FIG. 7, the operation of the warm-up operation in the construction machine 10 of the embodiment will be described.

[0034] First, in step S10, the temperature T of the power storage device 4 is detected. Then, in step S11, it is determined whether the detected temperature T is lower than the threshold temperature Tth at which warm-up operation is required. If T < Tth, it is determined that warm-up operation is required, and the process proceeds to step S12, where the preparation for warm-up operation is started. If T ≥ Tth, it is determined that warm-up operation is not required, and normal operation (charging) is executed (step S24).

[0035] In the subsequent step S12, based on the measured values of the current sensor 11 and the voltage sensor 12, the power storage amount of the power storage device 4 is calculated, and further the state of charge (SOC) is calculated. The controller 6 refers to the table in FIG. 5 based on the measured temperature T and the calculated state of charge (SOC), and sets (or updates) the value x of the charging current and the value y of the discharging current as the conditions (conditions 1 to 5) of the charging and discharging currents during warm-up operation (step S13), and warm-up operation is performed (step S14).

[0036] As shown in FIG. 7, warm-up operation is started at time t0, and charging and discharging of the power storage device 4 in the warm-up operation are repeated in a short period according to the determined values of the charging current and the discharging current. The top graph in FIG. 7 shows the change over time of the charging and discharging current to the power storage device 4, with the discharging current on the + side and the charging current on the - side. The middle graph in FIG. 7 shows the change over time of the state of charge (SOC). By repeating charging and discharging by the warm-up operation, the state of charge (SOC) also repeats increasing and decreasing. However, since the value of the charging current x is basically set to be larger than the value of the discharging current y, the state of charge (SOC) also increases over time as a whole. In FIG. 7, conditions 1 to 5 indicate the conditions during the execution of the warm-up operation, including the value x of the charging current and the value y of the discharging current set by referring to the table shown in FIG. 5 according to the state of charge (SOC) and the temperature T. The contents of conditions 1 to 5 change according to the change of the situation. In FIG. 7, an example where conditions 1 to 5 are set is illustrated, but the number of conditions set (updated) during warm-up operation is not limited to this.

[0037] Returning to the flowchart of FIG. 6 and explaining, after starting the warm-up operation according to the set conditions, the temperature T and the state of charge (SOC) of the power storage device 4 are detected or calculated at predetermined time intervals (steps S20, S21).

[0038] In the subsequent step S22, it is determined whether the temperature T detected in step S21 exceeds the next target temperature Tg (Tg1, Tg2,...). If T > Tg, as long as the temperature T has not reached the final target temperature Tmax (No in step S23), the process returns to step S13, and the charge and discharge current conditions are updated based on the table in FIG. 5. When the determination in step S23 is Yes, the warm-up operation ends, and the operation switches to the normal operation, that is, the normal charging operation of the power storage device 4.

[0039] If it is determined in step S22 that T ≤ Tg, then in step S32, it is determined whether the state of charge (SOC) calculated in step S21 exceeds the next target state of charge SOC (SOC1, SOC2...). If Yes, the process proceeds to step S33. If No, the process returns to step S14, and the warm-up operation continues under the same charge and discharge conditions.

[0040] In step S33, it is determined whether the state of charge (SOC) has reached the final target state of charge SOCmax. If not (No in step S33), the process returns to step S13, and the charge and discharge current conditions are updated based on the table. When the determination in step S33 is Yes, it is determined that the charging is complete, and the charging operation ends.

[0041] As described above, according to the present embodiment, even after the start of the warm-up operation, the state of charge (SOC) and the temperature T are continuously calculated or measured, the values x of the charging current and the values y of the discharging current are determined according to the combination of the state of charge (SOC) and the temperature T, and the conditions of the warm-up operation are appropriately updated. Thereby, the warm-up operation is executed under optimal conditions, and the charging operation of the power storage device 4 can be completed in a shorter time.

[0042] The present invention is not limited to the above-described embodiments, but includes various other modifications. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Also, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Further, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

Description of Reference Numerals

[0043] 1... Hydraulic control device, 2... Electric motor, 3... Inverter, 4... Energy storage device, 5... Charger, 6... Controller, 7... Power conversion device, 8... Energy storage device, 9... Junction box, 10... Construction machine, 11... Current sensor, 12... Voltage sensor, 13... Temperature sensor, 1110... Upper slewing body, 1111... Operator's cab, 1120... Lower traveling body, 1121... Crawler, 1130... Working machine, 1131... Boom, 1132... Arm, 1133... Bucket, 1140... Slewing mechanism, 1160... Cylinder.

Claims

1. An electric motor that drives a hydraulic control device, A power storage device that supplies power to the electric motor, A charger that charges the power storage device, A control device that controls the charger are provided, The control device determines whether to execute a warm-up operation in which charging and discharging of the power storage device are repeated based on at least the temperature of the power storage device, executes the warm-up operation by changing the magnitudes of the charging current and the discharging current during the warm-up operation according to the relationship between the temperature of the power storage device and the state of charge of the power storage device, In the warm-up operation, the control device increases the ratio of the charging current to the discharging current as the state of charge of the power storage device increases, A construction machine characterized by the above.

2. An electric motor that drives a hydraulic control device, A power storage device that supplies power to the electric motor, A charger that charges the power storage device, A control device that controls the charger are provided, The control device determines whether to execute a warm-up operation in which charging and discharging of the power storage device are repeated based on at least the temperature of the power storage device, executes the warm-up operation by changing the magnitudes of the charging current and the discharging current during the warm-up operation according to the relationship between the temperature of the power storage device and the state of charge of the power storage device, In the warm-up operation, the control device sets the charging current to a value larger than the discharging current, increases the ratio of the charging current to the discharging current as the temperature of the power storage device increases, increases the ratio of the charging current to the discharging current as the state of charge of the power storage device increases, A construction machine characterized by the above.

3. An electric motor that drives a hydraulic control device, A power storage device that supplies power to the electric motor, A charger that charges the power storage device, A control device that controls the charger are provided, The control device determines whether to execute a warm-up operation in which charging and discharging of the power storage device are repeated based on at least the temperature of the power storage device, executes the warm-up operation by changing the magnitudes of the charging current and the discharging current during the warm-up operation according to the relationship between the temperature of the power storage device and the state of charge of the power storage device, The power storage device regenerates the discharge power based on the discharge current during the warm-up operation to a power supply that supplies power to the charger, A construction machine characterized by the above.

4. The construction machine according to claim 1 or 3, wherein in the warm-up operation, the control device sets the charging current to a value larger than the discharging current.

5. The construction machine according to claim 1 or 3, wherein the control device increases a ratio of the charging current to the discharging current as the temperature of the power storage device increases during the warm-up operation.

6. The control device includes a table storing values of the charging current and the discharging current for each combination of the temperature of the power storage device and the state of charge, and determines the values of the charging current and the discharging current by referring to the table based on the obtained temperature and the state of charge. The construction machine according to any one of claims 1 to 3.

7. After setting the charging current and the discharging current in the warm-up operation, the control device updates conditions of the warm-up operation including the charging current and the discharging current based on the newly measured or calculated temperature and the state of charge. The construction machine according to any one of claims 1 to 3.

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