AU2017204398A1 - Battery powered industrial vehicle - Google Patents

Abstract

A battery powered industrial vehicle includes a drive motor, a battery device, an inverter device, an accelerator lever, a motor rotation detector and a control device. In a drive continuation mode, the control device causes the drive motor to operate at a 5 target rotation speed when the output voltage from the battery device is higher than a third voltage range, the control device causes the drive motor to operate at or less than an upper rotation speed limit when the output voltage is within the third voltage range, the control device causes the drive motor to operate at or less than an upper rotation speed limit when the output battery is within a second voltage range, and the control o device causes the drive motor to perform the regenerating operation to stop when the output voltage from the battery device is within a first voltage range. 9218618_1 (GHMatters) P106246.AU 17{17R-- 12 {11L 16 18R 1808 I8 30 32 33A 40 42 ---- --- --- ---------- --- 23 Win 1 38 k F IC41: C31 :33B T41

Description

BATTERY POWERED INDUSTRIAL VEHICLE

BACKGROUND OF THE INVENTION

The present invention relates to a battery powered industrial vehicle having a battery device and a drive motor as a power source.

In recent years, a battery powered industrial vehicle such as an electric forklift truck has been widely used for indoor transportation of freight such as in a warehouse because an exhaust gas from an internal combustion engine is undesirable. The following will describe a reach type forklift truck as an example of a conventional battery powered industrial vehicle with reference to FIG. 1. The reach type forklift truck is designated by 10 in the drawing and will simply be referred to as forklift truck 10. The forklift truck 10 is of a standing ride type and driven by a battery device and a drive motor as a power source. It is noted that X, Y and Z axes of coordinate system shown in FIG. 1 extend perpendicular to each other and indicate front-rear, the left-right and the up-down directions of the forklift truck 10, respectively.

As shown in FIG. 1, the forklift truck 10 includes a reach 11, a mast assembly 17, a pair of forks 16, a pair of right and left driven wheels 18R, 18L, a steerable drive wheel 18D, a caster wheel 18C and an accelerator lever 12. The forklift truck 10 further includes an operation lever to control the paired forks 16 and the mast assembly 17 and a steering wheel, and a mechanical foot brake for parking (none of which being shown).

The reach 11 includes a pair of reach members 11R, 11L that are disposed on the right and left sides of the vehicle body, respectively, and formed extending frontward from the lower part of the vehicle body. The right and left driven wheels 18R, 18L are disposed in the reach members 11R, 11L, respectively. The mast assembly 17 includes a pair of mast members 17R, 17L extending vertically and is movable slidably along the reach 11 in the front-rear direction of the forklift truck 10 and also tiltable in the frontward and rearward directions. The paired forks 16 are slidably movable up and down along the mast assembly 17.

The right and left driven wheel 18R, 18L are disposed unsteerably at positions adjacent to the front ends of the respective right and left reach members 11R, 11L.

The steerable drive wheel 18D is turnable or steerable relative to the front-rear direction of the forklift truck 10 for turning and driven by the drive motor 21. In other words, the drive motor 21 drives the steerable drive wheel 18D so as to move the forklift truck 10 forward and backward. It is to be noted that the forklift truck 10 has only one steerable drive wheel 18D which may be disposed either on the right or the left side of the vehicle body. The caster wheel 18C is disposed on the opposite side from the steerable drive wheel 18D. The caster wheel 18C is turnable in the X-Y plane and rotatably supported by the forklift truck 10.

The accelerator lever 12 is tiltable forward and backward from the neutral position. When the accelerator lever 12 is tilted forward from the neutral position by an operator of the forklift truck 10, the drive motor 21 drives the steerable drive wheel 18D forward thereby to move the forklift truck 10 forward at a speed that is determined by the tilted angle of the accelerator lever 12. When the accelerator lever 12 is moved back to the neutral position from the forward tilted position, the operation of the drive motor 21 is changed from the driving operation to the regenerating control operation, so that the forklift truck 10 is subjected to slight braking thereby to reduce its speed gradually.

When the accelerator lever 12 is tilted backward from the neutral position, the forklift truck 10 is moved backward at a speed in accordance with the tilted angle of the accelerator lever 12. When the accelerator lever 12 is moved back to the neutral position from the backward tilted position, the operation of the drive motor 21 is changed from the driving operation to the regenerating operation, so that the forklift truck 10 is subjected to slight braking thereby to reduce its speed gradually. Furthermore, when the accelerator lever 12 is tilted in a direction reverse to either of the forward and backward moving directions of the forklift truck 10, the forklift truck 10 is controlled by the regenerating operation at a large regeneration force and subjected to a strong braking.

In other words, the movement of the forklift truck 10 is instructed by the angular position of the accelerator lever 12.

In order to increase the safety of the forklift truck 10, various control operations are employed in the battery powered industrial vehicle. Japanese Patent Application Publication 2013-198190 discloses an electric vehicle corresponding to the battery powered industrial vehicle that performs a regenerating operation so as to stop the electric vehicle safely. In this electric vehicle, for example, when it is detected by a controller device that an operator is away from the vehicle while the electric vehicle is travelling, with the accelerator lever tilted in the current moving direction of the electric vehicle, the motor of the electric vehicle performs the regenerating operation with a first regeneration force so as to stop the forklift truck safely. In addition, when it is detected that the operator is away from the vehicle while the electric vehicle is travelling with the accelerator lever tilted in the direction reverse to the moving direction of the electric vehicle, the motor of the electric vehicle performs the regenerating operation with a second regeneration force that is greater than the first regeneration force so as to stop the forklift truck safely.

The control operations to increase the safety of the battery powered industrial vehicle include a battery control operation when the battery is over-discharged. In a case in which the battery is over-discharged, the battery voltage is reduced, so that the operator’s intended speed may not be achieved on a climbing slope (e.g. when the vehicle moves from the first floor to the second floor). If the operator continues to drive the industrial vehicle without noticing the over-discharged battery, the battery voltage is further reduced to the level at which the battery device cannot function as a power source, thus the forklift truck being brought to a halt on the spot. This is disadvantageous for work efficiency, and the serviceable life of the battery may be affected by the use of the over-discharged battery. In addition, the battery device cannot function as a power source for the forklift truck in case of any battery abnormality such as the temperature of the battery device exceeding a predetermined temperature limit and the battery power input/output being cutting off.

Even if battery condition such as over-discharging or cutting off of the battery input/output is reported on the display device, there is a fear that the operator may not notice such report on the display when the operator is concentrated on the operation. Therefore, there has been a demand for more reliable method for reporting the battery condition.

The present invention, which has been made in light of the above-described problems, is directed to providing a battery powered industrial vehicle that assures the operator of the vehicle of being informed of battery condition such as over-discharging and cutoff of the battery input/output which may become over discharged or cutoff if the operation of the industrial vehicle is continued.

SUMMARY OF THE INVENTION

In accordance with an aspect of the present invention, there is provided a battery powered industrial vehicle including a drive motor that drives a drive wheel so as to move the battery powered industrial vehicle forward and backward, a battery device outputting electric power for a driving operation of the drive motor and to which electric power generated by a regenerating operation of the drive motor is input, an inverter device disposed between the battery device and the drive motor, an accelerator lever tiltable forward and backward so as to instruct the forward and backward movement of the battery powered industrial vehicle, respectively, a motor rotation detector detecting a rotation speed and a rotational direction of the drive motor. The battery powered industrial vehicle further includes a control device causing the drive motor to perform the driving operation, to perform the regenerating operation, or to stop the driving operation based on an output voltage from the battery device, an angular position of the accelerator lever, and the rotation speed and the rotational direction of the drive motor detected by the motor rotation detector. A first voltage range that is higher than the output voltage when the battery device is over-discharged, a second voltage range that is higher the first voltage range, and a third voltage range that is higher than the second voltage range are preset in the control device. The control device determines that the battery powered industrial vehicle to be in the drive continuation mode when the drive motor is being rotated forward and the accelerator lever is tilted for forward movement of the battery powered industrial vehicle, or when the drive motor is being rotated backward and the accelerator lever is tilted for backward movement of the battery powered industrial vehicle, and also determines a target rotation speed of the drive motor based on the movement of the accelerator lever. When the output voltage from the battery device is higher than the third voltage range, the control device controls the drive motor so as to operate at the target rotation speed and the rotational direction. When the output battery from the battery device is within the third voltage range, the control device overwrites the target rotation speed of the drive motor so as to operate at or less than an upper rotation speed limit that is set based on the output voltage from the battery device and in forward or backward movement. When the output battery from the battery device is within the second voltage range, the control device overwrites the target rotation speed of the drive motor so as to operate at or lower than a minimum upper rotation speed limit that is a minimum value of the upper rotation speed limit values within the third voltage range and in forward or backward movement. When the output voltage from the battery device is within the first voltage range in the battery powered industrial vehicle in the drive continuation mode, the control device causes the driving motor to perform the regenerating operation with respect to the forward and backward movement of the battery powered industrial vehicle so as to stop the battery powered industrial vehicle regardless of the target rotation speed and the rotational direction instructed by the angular position of the accelerator lever.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a battery powered reach type forklift truck as an industrial vehicle according to an embodiment of the present invention; FIG. 2 is a schematic block diagram showing input and output of a drive control system of the forklift truck of FIG. 1, including a battery device and a drive motor; FIG. 3 is a flow chart showing a control process performed by an operation controller of the drive control system of FIG. 2; FIG. 4 is a table showing various operating modes of the forklift truck that are determined depending on the state of the drive motor and the position of an accelerator lever; FIG. 5 is a chart showing various battery modes determined depending on the output voltage of the battery device; FIG. 6 shows flow charts showing the details of control processes SUB100, SUB200 and SUB 300 shown in the flow chart of the FIG. 3; FIG. 7 is a flow chart showing a control process performed by a battery controller of the drive control system of FIG. 2; and FIG. 8 is a flow chart showing a control process performed by an inverter controller of the drive control system of FIG. 2.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following will describe an embodiment of the present invention with reference to the accompanying drawings. The configuration of the reach type forklift truck 10 (hereinafter simply referred to as forklift truck 10) according to the embodiment of the present invention has been described and, therefore, the description thereof will be omitted. The forklift truck 10 corresponds to the battery powered industrial vehicle according to the present invention.

[Drive control system including a battery device and a drive motor]

Referring to FIG. 2, the forklift truck 10 has a drive control system including a battery device 30, an inverter device 40, a drive motor 21, a gear 22, the steerable drive wheel 18D, an operation controller 50, the accelerator lever 12 and a display device 55. The steerable drive wheel 18D corresponds to the drive wheel according to the present invention.

The battery device 30 includes a battery controller 31 and a battery 32 having a cutoff switch 38 and a plurality of battery module units 33. Alternatively, the cutoff switch 38 may be provided in each battery module unit 33. The battery module unit 33 includes a battery module 34 that includes a plurality of battery cells 36 such as lithium ion battery cell, a module controller 35 that controls the battery module 34, and a temperature detection device 37 such as a thermometer that detects the temperature of the battery module 34. The module controller 35 monitors the temperature of the battery module 34, and the condition of each battery cell 36 and controls charging and discharging of the battery cells 36.

The battery controller 31 is operable to transmit and receive various information to and from each module controller 35 through a line T31 and controls the cutoff switch 38 via the control signal line C31. The battery controller 31 is also operable to transmit and receive various information to and from the operation controller 50 through a line T53. When the drive motor 21 is driven for the driving operation, the battery device 30 outputs the electric power Wout 1 (direct current) through terminals 33A, 33B. When the drive motor 21 is driven for the regenerating operation, the charge power Win2 (direct current) is input to the battery 32 through the terminals 33A, 33B. In other words, the battery device 30 is configured to supply electric power to the drive motor 21 for driving operation and receive electric power generated by a regenerating operation of the drive motor 21.

The inverter device 40 includes an inverter controller 41 and an inverter 42 having an inverter circuit 43. The inverter device 40 is disposed between the battery device and the drive motor 21. When the drive motor 21 is driven for the driving operation, the inverter controller 41 generates a control signal that controls the inverter circuit 43 so that the power Woutl from the battery device 30 is converted to the drive power Wout2 (alternating current) which is output to the drive motor 21. When the drive motor 21 is driven for the regenerating operation, the inverter controller 41 generates a control signal that controls the inverter circuit 43 so that the regenerated power Win1 (alternating current) converted to the charging power Win2 (direct current) which is output to the battery device 30.

The inverter controller 41 is operable to transmit and receive various information to and from the operation controller 50 through a line T54. When the inverter controller 41 receives driving operation information such as instructions for the rotational direction of the drive motor 21 and a target rotation speed from the operation controller 50, the inverter controller 41 controls the inverter circuit 43 based on such driving operation information. In addition, when the inverter controller 41 receives regenerating operation information such as instructions for the rotational direction of the drive motor 21 and a regeneration force, the inverter controller 41 controls the inverter circuit 43 based on such regenerating operation information. The inverter controller 41 is configured to receive a detection signal from a motor rotation detector 23 thereby to determine the rotational direction and the rotation speed of the motor shaft of the drive motor 21. The motor rotation detector 23 is operable to detect the rotational direction of the drive motor 21 and the rotation speed.

During the driving operation, the drive motor 21 is driven to rotate forward or backward with the drive power Wout 2 from the inverter device 40. The rotation power, or torque, of the drive motor 21 is transmitted to the steerable drive wheel 18D through the gear 22. During the regenerating operation, the drive motor 21 is driven to rotate by the steerable drive wheel 18D through the gear 22 thereby to generate the regeneration electric power Win1.

The operation controller 50, which corresponds to the control device of the present invention, is operable to transmit and receive various information to and from the battery controller 31. For example, the operation controller 50 sends a battery information request to the battery device 30 and receives therefrom the requested battery information including the temperature, voltage and battery conditions. Furthermore, the operation controller 50 is operable to transmit and receive various information to and from the inverter controller 41 through the line T54. The operation controller 50 sends an inverter information request to the inverter controller 41 and receives therefrom the inverter information including the rotation speed and the rotational direction of the drive motor 21. When the operation controller 50 causes the drive motor 21 to perform the driving operation, the operation controller 50 sends the driving operation information including an instruction of driving operation, the rotation speed, and the rotational direction to the inverter controller 41. When the drive motor 21 is operated for the regenerating operation, the operation controller 50 sends the regenerating operation information including an instruction of regenerating operation, a regeneration force to the inverter controller 41.

The accelerator lever 12 is provided for the operator to drive and stop the forklift truck 10 and is kept at the neutral position when the accelerator lever 12 is not operated by the operator. The accelerator lever 12 is tiltable forward and backward from the neutral position. When the operator tilts the accelerator lever 12 forward from the neutral position while the forklift truck 10 is at a stop, the forklift truck 10 starts moving forward and is accelerated to a speed corresponding to the tilted angle of the accelerator lever 12 relative to the neutral position. When the operator tilts the accelerator lever 12 backward from the neutral position while the forklift truck 10 is at a stop, the forklift truck 10 starts moving backward and is accelerated to a speed corresponding to the tilted angle of the accelerator lever 12 relative to the neutral position. In other words, the movement of the forklift truck 10 is controlled by the angular position of the accelerator lever 12.

The display device 55 is provided by a liquid crystal monitor and disposed at a position where it can be seen easily from the operator. For example, the display device 55 may be disposed adjacent to the accelerator lever 12. Various information from the operation controller 50 may be displayed on the display device 55. The display device 55 need not necessarily be provided.

[Control process performed by operation controller]

The following will describe a control process, or control sequence, performed by the operation controller 50 with reference to the flow chart shown in FIG. 3. The operation controller 50 initiates the control process within a predetermined period of time (e.g. between a few milliseconds and a few tens milliseconds) and the control sequence proceeds to step S10.

At step 10, the operation controller 50 sends an inverter information request to the inverter controller 41 and receives therefrom the inverter information including the rotation speed and the rotational direction of the drive motor 21 and the control sequence proceeds to step S15.

At step S15, the operation controller 50 determines the angular position of the accelerator lever 12, i.e. forward, backward or the neutral position, and moved degree of the accelerator lever 12, or the angular position of the accelerator lever 12, and the control sequence proceeds to step S20.

At step S20, the operation controller 50 determines the operating mode based on the rotation of the drive motor 21, or specifically the rotation speed and rotational direction of the drive motor 21, and the angular position of the accelerator lever 12, or specifically the tilted direction and degree of the accelerator lever 12, and the operation controller 50 provisionally stores the determined operating mode for the operating mode. Based on the determined operating mode, the rotation of the drive motor 21 and the angular position of the accelerator lever 12, the operation controller 50 determines the rotational direction, the target rotation speed and the target torque and provisionally stores the determined rotational direction, the determined target rotation speed and the determined target torque for the rotational direction, the target rotation speed and the target torque, respectively. In addition, the operation controller 50 determines the target regeneration force and stores the determined target regeneration force for the target regeneration force and the control sequence proceeds to step S25. The determination of the operating mode and the storing of the provisional operating mode will be described in the following.

The following will describe the various operating modes of the forklift truck 10 which are determined based on the movement of the accelerator lever 12 and the rotation of the drive motor 21 with reference to FIG. 4. The operating modes include the stop mode, the start mode, the drive continuation mode, and the stop request mode.

The forklift truck 10 is determined to be in the stop mode when the drive motor 21 is stopped and the accelerator lever 12 is positioned at the neutral position. In the stop mode, the drive motor 21 is at a stop performing neither the driving operation nor the regenerating operation and, therefore, the forklift truck 10 is at a stop. When the operation controller 50 determines that the forklift truck 10 is in the stop mode, the determined stop mode is provisionally stored for the operating mode.

The forklift truck 10 is determined to be in the start mode when the drive motor 21 is stopped and the accelerator lever 12 is positioned for forward or backward movement.

In the start mode, the forklift truck 10 at a stop starts moving and the drive motor 21 is driven to operate in accordance with the angular position of the accelerator lever 12. When the operation controller 50 determines that the forklift truck 10 is in the start mode, the operation controller 50 provisionally stores the start mode and the rotational direction determined by the accelerator lever 12 position (forward or backward) for the operating mode and the rotational direction, respectively. In addition, the operation controller 50 provisionally stores the target rotation speed determined by the angular position (tilted angle) of the accelerator lever 12 for the target rotation speed and the torque corresponding to the target rotation speed for the target torque.

The forklift truck 10 is determined to be in the drive continuation mode when the drive motor 21 is in rotation for forward movement and the accelerator lever 12 is tilted forward, or when the drive motor 21 is in rotation for backward movement and the accelerator lever 12 is tilted backward. In other words, the forklift truck 10 is determined to be in the drive continuation mode when the forklift truck 10 is being moved in the same direction as the accelerator lever 12 is tilted. In the drive continuation mode of the forklift truck 10, the drive motor 21 is continued to be driven to rotate in the same direction at the rotation speed, or a torque, in accordance with the tilted angle of the accelerator lever 12. When the operation controller 50 determines that the forklift truck 10 is in the drive continuation mode, the operation controller 50 provisionally stores the drive continuation mode and the current rotating direction of the drive motor 21, or the direction instructed by the angular position of the accelerator lever 12, for the operating mode and the rotational direction, respectively. In addition, the operation controller 50 provisionally stores the target rotation speed determined by the tilted angle of the accelerator lever 12 for the target rotation speed and the torque corresponding to the determined target rotation speed for the target torque.

The forklift truck 10 is determined to be in the stop request mode in any one of the following three cases, namely when the accelerator lever 12 is placed in the neutral position while the drive motor 21 is rotating forward or backward, when the accelerator lever 12 is tilted backward while the drive motor 21 is rotating forward, and when the accelerator lever 12 is tilted forward while the drive motor 21 is rotating backward. In other words, the stop request mode is determined when the accelerator lever 12 is moved to the neutral position or in the direction that causes the forklift truck 10 to move reverse to the direction in which the forklift truck 10 is currently moving. With regard to the regenerating force, three different levels of regenerating force are set, namely the large level, medium level and small level of regeneration force. The forklift truck 10 which is subjected to a large braking force due to the large level of regenerating force is stopped within a relatively short distance. The forklift truck 10 when subjected to a medium breaking force due to the medium regenerating force is stopped within a relatively long distance. When the accelerator lever 12 is moved to the neutral position while the forklift truck 10 is moving forward or backward, the operation controller 50 instructs the stop request mode with the medium regeneration force in which the forklift truck 10 is subjected to the regenerating operation at the medium level of regeneration force and stopped within a relatively long distance. When the accelerator lever 12 is moved in the direction reverse to the moving direction of the forklift truck 10 while the forklift truck 10 is moving forward or backward, the operation controller 50 instructs the stop request mode at the large regeneration force in which the forklift truck 10 is subjected to the regenerating operation at the large regeneration force thereby to be stopped within the relatively short distance. The small regeneration force will be described in later part hereof along the description of the battery mode. The medium regeneration force and the small regeneration force correspond to the first regeneration force and the second regeneration force, respectively, according to the present invention. When the forklift truck 10 is determined to be in the stop request mode, the operation controller 50 provisionally stores the stop request mode and the current rotating direction of the drive motor 21 for the operating mode and the rotational direction. Furthermore, the operation controller 50 provisionally stores the medium regeneration force when the accelerator lever 12 indicates the neutral position for the target regeneration force. The operation controller 50 provisionally stores the large force when the accelerator lever 12 indicates it is tilted in the direction reverse to the rotational direction of the drive motor 21.

Referring now back to the flow chart in FIG. 3, at step S25, the operation controller 50 sends a battery information request to the battery controller 31 and received therefrom the battery information including its voltage and condition and the control sequence proceeds to step S30.

At step S30, the operation controller 50 determines whether or not the battery information includes any information that need be reported to the operator. If YES, the control sequence proceeds to step S35A. If NO, the control sequence proceeds to step S35B. If the battery information indicates that the battery voltage is lowered and the power supply from the battery will be stopped within n seconds, for example, the operation controller 50 determines that the information required to be reported is included in the battery information. The battery information that needs to be reported includes the battery being overheated, the battery voltage being less than the cutoff voltage, or information indicating any abnormality in the module controller 35.

At step S35A, the operation controller 50 performs reporting of the information required to be reported, and the control sequence proceeds to step S60D. Reporting may be carried out by displaying the information required to be reported on the display device 55. If the battery information includes, for example, an indication that the battery voltage is lowered and the power supply from the battery will be stopped within X seconds, the operation controller 50 generates an error code on the display device 55, and the control sequence proceeds to step S60D. It is noted that the provision of the information may be accomplished by a buzzer or a warning lamp.

At step S35B, the operation controller 50 performs no reporting of the information, and the control sequence proceeds to the step S40.

At step S40, the operation controller 50 determines the battery mode based on the data of battery voltage included in the battery information received from the battery controller 31, and the control sequence proceeds to step 45. The determination of the battery modes will be described in detail below.

The following will describe different battery modes that are determined based on the level of the output voltage from the battery device 30, with reference to FIG. 5. Symbols Vh, V3, V2, V1 and Vs represent different levels of the output voltage of the battery device 30. The voltage Vh indicates that the battery voltage is at a high level and the battery device 30 is in an initial state without any degradation and fully charged. The voltage Vs corresponds to the battery voltage of low level, which represents a threshold for the over-discharge level of the battery device 30. When the battery voltage is at or less than the voltage Vs, the battery device 30 is considered to be in an over-discharged state. The use of an over-discharged battery may affect the serviceable life of the battery. The third voltage V3 is lower than the voltage Vh, the second voltage V2 is lower than the third voltage V3, and the first voltage V1 is lower than the second voltage V2.

Referring to FIG. 5, the battery voltage is divided into the following five different voltage ranges (1) through (5), which correspond to the respective battery modes. (1) Low range of voltage in which the battery voltage is at or lower than the voltage Vs when the battery is over-discharged, which corresponds to the battery input/output cutoff mode. (2) First range of voltage in which the battery voltage is higher than the voltage Vs and at or lower than the first voltage V1, which corresponds to the safe stop mode. The first range is higher after the low range. (3) Second range of voltage in which the battery voltage is higher than the first voltage V1 and at or lower than the voltage V2, which corresponds to the minimum upper rotation speed limit mode. The second range is higher after the first range. (4) Third range voltage in which the battery voltage [being greater] higher than the voltage V2 and at or lower than the third voltage V3, which corresponds to the upper rotation speed limit reducing mode. The third battery range is higher after the second range. (5) High range of voltage in which the battery voltage is at or higher than the third voltage V3, which corresponds to the normal voltage mode.

At step S40, the operation controller 50 determines the battery mode (i.e. the above-described battery input/output cutoff mode, the safe stop mode, the minimum upper rotation speed limit mode, the upper rotation speed limit reducing mode or the normal voltage mode) based on the current battery voltage, and the control sequence proceeds to step S45.

At step S45, the operation controller 50 determines whether or not the battery mode determined at step S40 is the normal voltage mode. If YES, the control sequence proceeds to step S65. If NO, the control sequence proceeds to step S50.

At step S50, the operation controller 50 determines whether or not the battery mode determined at step S40 is the upper rotation speed limit reducing mode. If YES, the control sequence proceeds to step S60A. If NO, the control sequence proceeds to step S55.

At step S55, the operation controller 50 determines whether or not the battery mode determined at step S40 is the minimum upper rotation speed limit mode. If YES, the control sequence proceeds to step S60B. If NO, the control sequence proceeds to step S60C.

If the control sequence proceeds to step S60A, the operation controller 50 performs the control process SUB100 and the control sequence proceeds to step S65. The following will describe the control process SUB100 shown in FIG. 6.

Referring to the control process SUB100 in FIG. 6, at the first step S110, the operation controller 50 determines whether or not the operating mode provisionally stored at step S20 is the start mode. If YES, the control sequence proceeds to step S120. If NO, the control sequence proceeds to step S115.

At step S115, the operation controller 50 determines whether or not the operating mode provisionally stored at step S20 is the drive continuation mode. If YES, the control sequence proceeds to step S120. If NO, the operation controller 50 ends the control process SUB100 and the control sequence proceeds to step S65 in FIG. 3.

At step S120, the operation controller 50 calculates the upper rotation speed limit of the drive motor 21 based on the battery voltage and the control sequence proceeds to step S125. The upper rotation speed limit of the drive motor 21 is gradually reduced with a decrease of the battery voltage from the third voltage V3 to the second voltage V2, and the upper rotation speed limit of the drive motor 21 at the voltage V2 is set, for example, at 3600 rpm. With the operation of the drive motor 21 at 3600 rpm, the forklift truck 10 travels at or less than 8 km/h and the torque relative to the rotation speed is reduced, so that the operator feels lack of power. This allows the operator to recognize that the battery becomes over-discharged if the forklift truck operation is continued. In addition, the operator may avoid climbing a slope because of the lack of power.

At step S125, the operation controller 50 determines whether or not the target rotation speed provisionally stored at step S20 is greater than the calculated upper rotation speed limit calculated at step S120. If YES, the control sequence proceeds to step S130. If NO, the control process SUB100 ends, and the control sequence proceeds to step S65.

At step S130, the operation controller 50 overwrites the provisionally stored target rotation speed with the upper rotation speed limit calculated at step S120 and the provisionally stored target torque with the torque corresponding to the calculated upper rotation speed limit, and the control process SUB100 ends, and the control sequence proceeds to S65.

At step S60B, the operation controller 50 performs the control process SUB200 shown in FIG. 6 and the control sequence proceeds to step S65. The following will describe the control process SUB 200.

Referring to the control process SUB200 shown in FIG. 6, at step S210, the operation controller 50 determines whether not the operating mode provisionally stored at step S20 is the drive start mode. If YES, the control sequence proceeds to step S220. If NO, the control sequence proceeds to step S215.

At step S215, the operation controller 50 determines whether or not the operating mode provisionally stored at step S20 is the drive continuation mode. If YES, the control sequence proceeds to step S220. If NO, the control process SUB 200 ends and the control sequence proceeds to step S65 in FIG. 3.

At step S220, the operation controller 50 calculates the minimum upper rotation speed limit of the drive motor 21 and the control sequence proceeds to step S225. The minimum upper rotation speed limit is the minimum value of the upper rotation speed limit calculated at step S120 in the control process SUB100 and corresponds to the second voltage V2. The minimum upper rotation speed of the drive motor 21 at the second voltage V2 is set, for example, at 3600 rpm. With the minimum upper limit operation of the drive motor 21 set at 3600 rpm, the forklift truck 10 travels at or less than 8 km/h and with a torque that is low relative to the rotation speed, so that the operator feels lack of power. This allows the operator to recognize that the battery becomes over-discharged if the operation is continued. In addition, the operator may avoid climbing a slope because of the lack of power.

At step S225, the operation controller 50 determines whether or not the provisionally stored target rotation speed stored at step S20 is greater than the minimum upper rotation speed calculated at step S220. If YES, the control sequence proceeds to step S230. If NO, the control process SUB200 ends and the control sequence proceeds to step S65.

At step S230, the operation controller 50 overwrites the provisionally stored target rotation speed with the minimum upper rotation speed limit and also the provisionally stored target torque with a torque corresponding to the minimum upper rotation speed limit. Thus, the control process SUB200 ends and the control sequence proceeds to S65.

At the aforementioned step S60C, the operation controller 50 performs the control process SUB300 shown in FIG. 6 and the control sequence proceeds to step S65. The following will describe the control process SUB 300.

Referring to the control process SUB300 in FIG. 6, at step S310, the operation controller 50 determines whether not the operating mode provisionally stored at step S20 is the drive start mode. If YES, the control sequence proceeds to step S320B. If NO, the control sequence proceeds to step S315.

At step S315, the operation controller 50 determines whether or not the operating mode provisionally stored at step S20 is the drive continuation mode. If YES, the control sequence proceeds to step S320A. If NO, the control process SUB 300 ends and the control sequence proceeds to step S65 in FIG. 3.

At step S320A, the provisionally stored operating mode (or the drive continuation mode) and the target regeneration force are overwritten or replaced with the stop request mode and the target regeneration force at the small regeneration force, respectively. Then, the control process SUB300 ends and the control sequence proceeds to step S65. The small regeneration force, for example, is about one third of the medium regeneration force, which is performed when the operating mode is the stop request mode and the accelerator lever 12 is positioned at the neutral position, as shown in FIG. 4. The large regeneration force is shown in FIG. 4, for example, when the operating mode is the stop request mode while the accelerator lever is positioned for the forward movement. With the regenerating operation at the small regeneration force, the forklift truck 10 then traveling is braked gradually, so that the operator handling the accelerator lever 12 feels the speed of the forklift truck 10 being reduced. This allows the operator to recognize that the battery is becoming over-discharged or cutoff of the battery occurs if the forklift truck operation is continued.

At step S320B, the provisionally stored operating mode is overwritten or replaced with the stop mode. The control process SUB300 ends and the control sequence proceeds to step S65. In this state, the forklift truck 10 at a stop will not be moved by the operation of the accelerator lever 12 to start driving, which allows the operator to recognize that the battery is nearly over-discharged.

At step S60D, the operation controller 50 begins to perform the control process SUB300 shown in FIG. 6 and the control sequence proceeds to step S65. The control process SUB300 has been already described and, therefore, the description thereof will be omitted.

At step S65, the operation controller 50 overwrites or replaces the provisionally stored operating mode, the rotational direction, the rotation speed, the target torque and the target regeneration force with the final operating mode, the final rotational direction, the final rotation speed, the final target torque, and the final target regeneration force, respectively, and the control sequence proceeds to step S70.

At step S70, the operation controller 50 sends motor control information including the final operating mode, the final rotational direction, the final target rotation speed, the final target torque, the final target regeneration force to the inverter controller 41, and the control sequence ends. The operation of the inverter controller 41 after receiving such motor control information will be described later.

As has been described, when the operating mode and the battery mode are the drive continuation mode and the normal voltage mode, respectively, the operation controller 50 controls the drive motor 21 so as to operate at the target rotation speed for the drive continuation mode. When the operating mode and the battery mode are either the drive continuation mode and the upper rotation speed limit reducing mode (or the third voltage range), or the start mode and the upper rotation speed limit reducing mode, respectively, the operation controller 50 controls the drive motor 21 according to the control process SUB 100 to operate at or less than the rotation speed limit which is set in accordance with the output voltage from the battery device 30. When the operating mode and the battery mode are either the drive continuation mode and the minimum upper rotation speed limit mode (or the second battery voltage range), or the start mode and the minimum upper rotation speed limit mode, respectively, the operation controller 50 controls the drive motor 21 according to the control process SUB200 so as to operate at or less than the minimum upper rotation speed limit. When the operating mode and the battery mode are the drive continuation mode and the safe stop mode (or the first voltage range), respectively, the operation controller 50 controls the drive motor 21 according to the control process SUB 300 to perform regenerating operation at the small regeneration force, thereby safely stopping the forklift truck 10.

When the temperature of the battery device 30 is at or higher than a predetermined temperature and the forklift truck 10 is in the drive continuation mode, the drive motor 21 performs the regenerating operation at the small regeneration force instead of the driving operation, thereby causing the forklift truck 10 to stop safely.

When the operating mode and the battery mode are the start mode and the safe stop mode (or the first voltage range), respectively, electric power supply to the drive motor 21 is stopped according to the control process SUB300 of step S60C, thereby keeping the forklift truck 10 at a stop.

When the temperature of the battery device 30 is at or higher than the predetermined temperature and the operating mode is the start mode, the drive motor 21 is not driven and the electric power supply to the drive motor 21 is stopped according to step S30 and the control process SUB300 of step S60D, thereby keeping the forklift truck 10 at a stop.

The following will describe a control sequence performed by the battery controller 31 with reference to the flow chart shown in FIG. 7. The battery controller 31 initiates the battery control sequence shown in FIG. 7 within a predetermined period of time (between a few milliseconds and a few tens milliseconds) and the control sequence proceeds to step S410.

At step S410, the battery controller 31 determines whether or not the temperature of the battery detected by the temperature detection device 37 is at or higher than the predetermined temperature. If YES, the control sequence proceeds to step S415. If NO, the control sequence proceeds to step S425.

At step S415, the battery controller 31 sends warning message information to the operation controller 50 and the control sequence proceeds to step S420. The battery controller 31 sends warning message information indicating, for example, the battery temperature is increased and the battery will be cutoff within X seconds. After receiving the warning message information, the operation controller 50 performs reporting based on the received warning message information at step S35A shown in FIG. 3.

At step S420, the battery controller 31 determines whether not the battery temperature at or higher than the predetermined temperature has lasted for or longer than a predetermined period of time (for example, ten seconds). If YES, the control sequence proceeds to step S485. If NO, the control sequence proceeds to step S425.

At step S425, the battery controller 31 determines whether or not the battery voltage is at or lower than the cutoff voltage, or the voltage Vs. If YES, the control sequence proceeds to step S430. If NO, the control sequence proceeds to step S440.

At step S430, the battery controller 31 sends warning message information, such as “the battery voltage is lowered and the battery will be cutoff within X seconds”, and the control sequence proceeds to step S435. The operation controller 50 performs reporting based on the received warning message information at step S35A shown in FIG. 3.

At step S435, the battery controller 31 determines whether not the battery voltage at or less than the cutoff voltage has lasted for or longer than a predetermined period of time. If YES, the control sequence proceeds to step S485. If NO, the control sequence proceeds to step S440.

At step S440, the battery controller 31 determines whether or not it has received the battery information request from the operation controller 50. If YES, the control sequence proceeds to step S445. If NO, the battery control sequence ends.

At step S445, the battery controller 31 sends to the operation controller 50 the battery information including the battery voltage and the battery temperature and the control sequence ends.

At step S485, the battery controller 31 cuts off electric power output from the battery device 30 and electric power input to the battery device 30, and the battery control sequence ends. In this case, the battery controller 31 opens the cutoff switch 38. When the battery is cut off, the electric power supply to the battery controller 31, the inverter controller 41, and the operation controller 50 is stopped, thus stopping the operation.

As has been described, at steps S425 to S435, when the battery controller 31 of the battery device 30 determines that the battery voltage is reduced to or lower than the cutoff voltage, or the over-discharged range which is set as a range lower than the first voltage range, the battery controller 31 of the battery device 30 performs reporting, or providing warning message information, for a predetermined period of time and then, opens the cutoff switch 38, thereby cutting off the input/output of electric power.

At steps S410 to S420, when the battery controller 31 of the battery device 30 determines that the battery temperature is at or higher than the cutoff temperature, or the above-described predetermined temperature, the battery controller 31 of the battery device 30 performs reporting, or providing warning message information, for a predetermined period of time and then opens the cutoff switch 38, thereby cutting off the input/output of electric power.

The following will describe a control sequence performed by the inverter controller 41 with reference to FIG 8. The inverter controller 41 initiates the inverter control sequence within a predetermined period of time (between a few milliseconds and a few tens milliseconds) and the control sequence proceeds to step S510.

At step S510, the inverter controller 41 determines whether or not it has received an inverter information request. If YES, the control sequence proceeds to step S515.

If NO, the control sequence proceeds to step S520.

At step S515, the inverter controller 41 sends the inverter information including the rotation speed and the rotational direction of the drive motor 21 to the operation controller 50, and the control sequence proceeds to step S520.

At step S520, the inverter controller 41 determines whether or not it has received the motor control information form the operation controller 50. If YES, the control sequence proceeds to step S525. If NO, the control process ends.

At step S525, the inverter controller 41 determines whether or not the final operating mode in the received motor control information is the drive start mode. If YES, the control sequence proceeds to step S540A. If NO, the control sequence proceeds to step S530.

At step S530, the inverter controller 41 determines whether or not the final operating mode in the received motor control information is the drive continuation mode.

If YES, the control sequence proceeds to step S540A. If NO, the control sequence proceeds to step S535.

At step S535, the inverter controller 41 determines whether or not the final operating mode in the received motor control information is the stop request mode. If YES, the control sequence proceeds to step S540B. If NO, the control sequence proceeds to step S540C.

At step S540A, the inverter controller 41 controls the drive motor 21 to perform the driving operation based on the final rotational direction, the final target rotation speed and the final target torque included in the received motor control information and the control sequence ends.

At step S540B, the inverter controller 41 controls the drive motor 21 to perform the regenerating operation based on the final rotational direction and the final target regeneration force included in the received motor control information and the control sequence ends.

At step S540C, the inverter controller 41 stops electric power supply to the drive motor 21 and the control sequence ends.

The battery powered industrial vehicle of the present invention is not limited to above-described embodiment, but may be modified within the scope of the present invention.

The present invention is not limited to a reach type forklift truck, but it is applicable to any industrial vehicle provided with a battery device and a drive motor as driving power source.

The battery is not limited to lithium-ion battery, but any suitable battery such as a lead battery, a nickel hydrogen battery may be used for the battery device. The values for the battery voltages Vh, V3, V2, V1, Vs may be set suitably depending on the type of the battery material.

Although the control device of the battery powered industrial vehicle includes three separately provided controllers, namely the operation controller 50, the battery controller 31 and the inverter controller 41, in the above-described embodiment, the industrial vehicle may be equipped with one controller, or two or more controllers.

Motor control information is not limited to the information described with reference to the above embodiment, but any kinds of information such as final target speed may be included in the motor control information.

In the battery powered industrial vehicle according to the above-described embodiment, the target rotation speed of the drive motor 21 is reduced with a reduction of the battery voltage when the battery mode is the upper rotation speed limit reducing mode, but it may be so configured that the target torque of the drive motor 21 or the upper target speed limit of the battery powered industrial vehicle is used for controlling the operation of the battery powered industrial vehicle. Similarly, when the battery mode is the upper minimum rotation speed limit, the target torque or the upper target speed limit of the battery powered industrial vehicle may be used for controlling the operation of the battery powered industrial vehicle.

Any values used in the description of the present embodiment are examples and does not intend to limit the scope of the present invention. Additionally, limitation as expressed by, for example, “at or higher than” is explanatory and this may be replaced with “higher than.”

According to the present invention, the forklift truck 10 includes the drive motor 21 that drives the drive wheel so as to move the forklift truck 10 forward and backward, the battery device 30 that outputs electric power to the drive motor 21 for a driving operation and to which electric power generated by a regenerating operation of the drive motor 21 is input, the inverter device 40 that is disposed between the battery device 30, the drive motor 21, the accelerator lever 12 that is tiltable forward and backward so as to instruct the forward and backward movement of the forklift truck 10, and the motor rotation detector 23 that detects the rotation speed and the rotational direction of the drive motor 21. The forklift truck 10 further includes the operation controller 50 that causes the drive motor 21 to perform the driving operation, to perform the regenerating operation, or to stop the driving operation based on the output voltage from the battery device 30, the angular position of the accelerator lever 12, the rotation speed and the rotational direction of the drive motor 21 that are detected by the motor rotation detector 23. The first voltage range that is higher than the output voltage of the battery device 30 when the battery device 30 is over-discharged, the second voltage range that is higher the first voltage range, and the third voltage range that is higher than the second voltage range are preset in the operation controller 50. The operation controller 50 determines the target rotation speed of the drive motor 21 based on the angular position of the accelerator lever 12 when the forklift truck 10 is determined to be in the drive continuation mode at which the drive motor 21 is being rotated forward while the accelerator lever 12 is tilted forward for the forward movement of the forklift truck 10, or at which the drive motor 21 is being rotated backward while the accelerator lever 12 is tilted backward for the backward movement of the forklift truck 10. When the output voltage from the battery device 30 is higher than the third voltage range in the forklift truck 10 in the drive continuation mode, the operation controller 50 causes the drive motor 21 to operate at the target rotation speed and in the rotational direction instructed by the angular position of the accelerator lever. When the output voltage from the battery device 30 is within the third voltage range in the forklift truck 10 in the drive continuation mode, the operation controller 50 overwrites the target rotation speed of the drive motor 21 and causes the drive motor to performs the driving operation at or lower than the upper rotation speed limit that is set based on the output voltage from the battery device 30 and in the rotational direction instructed by the angular position of the accelerator lever 12. When the output battery from the battery device 30 is within the second voltage range in the forklift truck 10 in the drive continuation mode, the operation controller 50 overwrites the target rotation speed of the drive motor 21 and causes the drive motor to perform the driving operation at or lower than the minimum upper rotation speed limit that is a minimum value of the upper rotation speed limit within the third voltage range and in the rotational direction instructed by the angular position of the accelerator lever 12. When the output voltage from the battery device 30 is within the first voltage range in the forklift truck 10 in the drive continuation mode, the operation controller 50 causes the driving motor to perform the regenerating operation with respect to the forward and backward movement of the battery powered industrial vehicle so as to stop the battery powered industrial vehicle regardless of the target rotation speed and the rotational direction instructed by the angular position of the accelerator lever 12.

In the drive continuation mode of the forklift truck 10 in which the rotational direction of the drive motor 21 coincides with the movement of the forklift truck 10 instructed by the angular position of the accelerator lever 12, when the output voltage from the battery device 30 is within the third voltage range, the operation controller causes the drive motor 21 to perform the driving operation but gradually reduces the upper rotation speed limit of the drive motor 21 in accordance with the output voltage from the battery device 30. When the output voltage from the battery device 30 is within the second voltage range, the operation controller 50 causes the drive motor 21 to performs the driving operation but limits the upper rotation speed of the drive motor 21 at or less than the minimum upper rotation speed limit. When the output voltage from the battery device 30 is within the first voltage range, the operation controller 50 causes the drive motor 21 to stop the drive operation so as to safely stop the forklift truck 10 with the regenerating operation of the drive motor 21. When the output voltage from the battery device 30 is within the third and second voltage range, the upper rotation speed limit of the drive motor 21 and hence the speed of the forklift truck 10 is reduced gradually, which allows the operator to recognize that the battery device 30 becomes over-discharged in advance. In addition, when the output voltage from the battery device 30 is within the first voltage range, which is a state of the battery that is soon to be over-discharged, the operation controller 50 causes the drive motor 21 to perform the regenerating operation instead of the driving operation so as to stop the forklift truck 10 safely, which makes sure the operator to notice that the battery device 30 becomes over-discharged in due course.

When a temperature of the battery device 30 is at or higher than the predetermined temperature in the forklift truck 10 in the drive continuation mode, the operation controller 50 causes the drive motor 21 to performs the regenerating operation, instead of the driving operation, with respect to the forward and backward movement of the forklift truck 10 so as to stop the forklift truck 10 regardless of the output voltage from the battery device 30. In other words, when a temperature of the battery device 30 is at or higher than the predetermined temperature, the forklift truck 10 is stopped safely with the regenerating operation of the drive motor 21 even if the accelerator lever 12 is operated for the forward or backward movement of the forklift truck 10. This makes sure the operator to notice that the battery device becomes cutoff soon.

The accelerator lever 12 may be positioned at a neutral position at which the accelerator lever 12 instructs neither the forward movement nor the backward movement of the forklift truck 10. The forklift truck 10 is determined to be in a stop request mode when the accelerator lever 12 is positioned in the neutral position while the drive motor 21 is being rotated forward or backward. When the output voltage from the battery device 30 is higher than the first voltage range in the forklift truck 10 in the stop request mode, the operation controller 50 controls the drive motor 21 to operate the regenerating operation at the first regeneration force to stop the forklift truck 10. When the output voltage from the battery device 30 is within the first voltage range in the forklift truck 10 in the drive continuation mode, or when the temperature of the battery device 30 is at or higher than the predetermined temperature, the operation controller 50 controls the drive motor 21 to operate the regenerating operation at the second regeneration force which is lower than the first regeneration force to stop the forklift truck 10. The operator feels the deceleration of the forklift truck, so that the operator recognizes that the battery device becomes over-discharged soon.

In the start mode of the forklift truck 10 in which the drive motor 21 is at a stop and the forward movement or the backward movement of the forklift truck 10 is instructed by the angular position of the accelerator lever 12, the operation controller 50 calculates the target rotation speed of the drive motor based on the angular position of the accelerator lever 12. When the output voltage from the battery device 30 is within the third voltage range in the forklift truck in the start mode, the operation controller 50 causes the drive motor 21 to perform the driving operation at the target rotation speed and in the rotational direction instructed by the angular position of the accelerator lever 12. When the output voltage from the battery device 30 is within the second voltage range, the operation controller 50 overwrites the target rotation speed of the drive motor and causes the drive motor to perform the driving operation at or lower than the minimum upper rotation speed limit and in the rotational direction instructed by the angular position of the accelerator lever 12. When the output voltage from the battery device 30 is within the first voltage range, the operation controller 50 the control device causes no operation of the drive motor 21 regardless of the target rotation speed and the rotational direction instructed by the angular position of the accelerator lever 12

In the start mode of the forklift truck 10 in which the forklift truck 10 at a stop starts moving, when the output voltage from the battery device 30 is within the third voltage range, the operation controller 50 causes the drive motor 21 to perform the driving operation but gradually reduces the upper rotation speed limit of the drive motor 21 in accordance with the output voltage from the battery device 30. When the output voltage from the battery device 30 is within the second voltage range, the operation controller 50 causes the drive motor 21 to performs the driving operation but limits the upper rotation speed of the drive motor 21 at or less than the minimum upper rotation speed. When the output voltage from the battery device 30 is within the first voltage range, the operation controller 50 causes no operation of the drive motor 21.

Accordingly, when the output voltage from the battery device 30 is within the third and second voltage range, the upper rotation speed limit of the drive motor 21 and hence the speed of the forklift truck 10 is reduced gradually, which allows the operator to recognize that the battery device 30 becomes over-discharged in advance. In addition, when the output voltage from the battery device 30 is within the first voltage range, the operation controller 50 causes no operation of the drive motor 21 even if the accelerator lever 12 is positioned for the forward and backward movement of the forklift truck 10, so that the operator is well informed of that the battery device 30 becomes over-discharged in due course.

When the temperature of the battery device 30 is at or greater than the predetermined temperature in the forklift truck 10 in the start mode, the operation controller 50 stops the driving operation of the drive motor 21 regardless of the output voltage from the battery device 30. This allows the operator to recognize that the battery becomes over-discharged soon.

The battery device 30 cuts off the battery input and output when the output voltage from battery device 30 is at or lower than the predetermined cutoff voltage which is lower than the first voltage range. In such way, when the battery device is over-discharged, the use of the battery device is forcefully stopped, so that the serviceable life of the battery device 30 may be increased.

The battery device 30 includes a thermometer, and the battery device 30 cuts off the battery input and output when the temperature of the battery detected by the thermometer is at or higher than a predetermined cutoff temperature. When the battery device is over-discharged, the use of the battery device is forcefully stopped, so that the battery device 30 may be used more safely.

The battery device 30 performs reporting for a predetermined period of time before the battery device 30 cuts off the battery input and output. The forklift truck 10 may be safely stopped before the battery device is cutoff.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

Claims (8)

1. THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

   1. A battery powered industrial vehicle comprising: a drive motor driving a drive wheel so as to move the battery powered industrial vehicle forward and backward; a battery device outputting electric power for a driving operation of the drive motor and to which electric power generated by a regenerating operation of the drive motor is input; an inverter device disposed between the battery device and the drive motor; an accelerator lever tiltable forward and backward so as to instruct the forward and backward movement of the battery powered industrial vehicle, respectively; a motor rotation detector detecting a rotation speed and a rotational direction of the drive motor; and a control device causing the drive motor to perform the driving operation, to perform the regenerating operation, or to stop the driving operation based on an output voltage from the battery device, an angular position of the accelerator lever, and the rotation speed and the rotational direction of the drive motor detected by the motor rotation detector, wherein a first voltage range that is higher than the output voltage when the battery device is over-discharged, a second voltage range that is higher the first voltage range, and a third voltage range that is higher than the second voltage range are preset in the control device, the control device determines a target rotation speed of the drive motor based on the angular position of the accelerator lever when the battery powered industrial vehicle is determined to be in a drive continuation mode at which the drive motor is being rotated forward while the accelerator lever is tilted forward for the forward movement of the battery powered industrial vehicle, or at which the drive motor is being rotated backward while the accelerator lever is tilted backward for the backward movement of the battery powered industrial vehicle, when the output voltage from the battery device is higher than the third voltage range in the battery powered industrial vehicle in the drive continuation mode, the control device causes the drive motor to perform the driving operation at the target rotation speed and in the rotational direction instructed by the angular position of the accelerator lever, when the output voltage from the battery device is within the third voltage range in the battery powered industrial vehicle in the drive continuation mode, the control device overwrites the target rotation speed of the drive motor and causes the drive motor to perform the driving operation at or lower than an upper rotation speed limit that is set based on the output voltage from the battery device and in the rotational direction instructed by the angular position of the accelerator lever, when the output battery from the battery device is within the second voltage range in the battery powered industrial vehicle in the drive continuation mode, the control device overwrites the target rotation speed of the drive motor and causes the drive motor to perform the driving operation at or lower than a minimum upper rotation speed limit that is a minimum value of the upper rotation speed limit within the third voltage range and in the rotational direction instructed by the angular position of the accelerator lever, when the output voltage from the battery device is within the first voltage range in the battery powered industrial vehicle in the drive continuation mode, the control device causes the driving motor to perform the regenerating operation with respect to the forward and backward movement of the battery powered industrial vehicle so as to stop the battery powered industrial vehicle regardless of the target rotation speed and the rotational direction instructed by the angular position of the accelerator lever.
2. 2. The battery powered industrial vehicle according to claim 1, wherein when a temperature of the battery device is at or higher than a predetermined temperature in the battery powered industrial vehicle in the drive continuation mode, the control device causes the drive motor to perform the regenerating operation with respect to the forward and backward movement of the battery powered industrial vehicle so as to stop the battery powered industrial vehicle regardless of the output voltage from the battery device instructed by the angular position of the accelerator lever.
3. 3. The battery powered industrial vehicle according to claim 1 or 2, wherein the accelerator lever is positioned in a neutral position when the accelerator lever instructs neither the forward movement nor the backward movement of the battery powered vehicle, wherein the battery powered industrial vehicle is determined to be in a stop request mode when the accelerator lever is positioned in the neutral position while the drive motor is being rotated forward or backward, wherein when the output voltage from the battery device is higher than the first voltage range in the battery powered industrial vehicle in the stop request mode, the control device causes the drive motor to perform the regenerating operation at a first regeneration force to stop the battery powered industrial vehicle, and when the output voltage from the battery device is within the first voltage range, or wherein when the temperature of the battery device is at or higher than the predetermined temperature, in the battery powered industrial vehicle in the drive continuation mode, the control device causes the drive motor to perform the regenerating operation at a second regeneration force which is lower than the first regeneration force to stop the battery powered industrial vehicle.
4. 4. The battery powered industrial vehicle according to any one of claims 1 through 3, wherein the battery powered industrial vehicle is determined to be in a start mode when the drive motor is at a stop and the forward movement or the backward movement of the battery powered industrial vehicle is instructed by the angular position of the accelerator lever, wherein the control device calculates a target rotation speed of the drive motor based on the angular position of the accelerator lever in the battery powered industrial vehicle in the start mode, wherein when the output voltage from the battery device is higher than the third voltage range in the battery powered industrial vehicle in the start mode, the control device causes the drive motor to perform the driving operation at the target rotation speed and in the rotational direction instructed by the angular position of the accelerator lever, wherein when the output voltage from the battery device is within the third voltage range in the battery powered industrial vehicle in the start mode, the control device overwrites the target rotation speed of the drive motor and causes the drive motor to perform the driving operation at or less than the upper rotation speed limit and in the rotational direction instructed by the angular position of the accelerator lever, wherein when the output battery from the battery device is within the second voltage range in the battery powered industrial vehicle in the start mode, the control device overwrites the target rotation speed of the drive motor and causes the drive motor to perform the driving operation at or lower than the minimum upper rotation speed limit and in the rotational direction instructed by the angular position of the accelerator lever, and wherein when the output voltage from the battery device is within the first voltage range in the battery powered industrial vehicle in the start mode, the control device causes no operation of the drive motor regardless of the target rotation speed and the rotational direction instructed by the angular position of the accelerator lever.
5. 5. The battery powered industrial vehicle according to any one of claims 1 through 4, wherein when the temperature of the battery device is at or greater than the predetermined temperature in the battery powered industrial vehicle in the start mode, the control device causes no operation of the drive motor regardless of the output voltage from the battery device.
6. 6. The battery powered industrial vehicle according to any one of claims 1 through 5, wherein the battery device cuts off the battery input and output when the output voltage from battery device is at or lower than a predetermined cutoff voltage which is lower than the first voltage range.
7. 7. The battery powered industrial vehicle according to any one of claims 1 through 6, wherein the battery device includes a thermometer, and the battery device cuts off the battery input and output when the temperature of the battery detected by the thermometer is at or higher than a predetermined cutoff temperature.
8. 8. The battery powered industrial vehicle according to claim 6 or 7, wherein the battery device performs reporting for a predetermined period of time before the battery device cuts off the battery input and output.