JP2014156307A - Forklift - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a forklift in which overvoltage of a battery due to regenerative power can be prevented without giving discomfort to an operator and a surrounding person and without implementation of unintended operation of a cargo gear.SOLUTION: A forklift which comprises: a battery 2; a traveling motor M; a hydraulic motor M; a power conversion part 3 for the traveling motor Mthat converts DC power supplied from the battery 2 to AC power to supply to the traveling motor Mand regeneratively charges the regenerative power obtained from the traveling motor Mto the battery 2; a power conversion part 4 for a hydraulic motor that applies switching to DC power by switching means to supply to the hydraulic motor M; and a control part 5. In the forklift, the control part 5 controls the switching means of the power conversion part 4 for a hydraulic motor and lets the hydraulic motor Mconsume at least a part of the regenerative power without rotating the hydraulic motor Mso that the battery voltage does not exceed a preset first threshold value due to regenerative power.

Description

  The present invention relates to a forklift that can prevent a battery from being overvoltage due to regenerative electric power obtained from a traveling motor.

  In general, in a forklift driven by a battery, when regenerative braking is performed during traveling, regenerative electric power obtained from the traveling motor is regenerated to the battery and the battery voltage rises. In particular, the battery immediately after charging has a significant voltage rise, and if regenerative braking is continuously performed, the battery voltage may exceed the withstand voltage of the elements constituting the control unit and the like.

  As a forklift capable of preventing such an overvoltage of the battery, for example, a forklift described in Patent Document 1 is known. In the forklift described in Patent Document 1, when the battery voltage becomes equal to or higher than a preset starting voltage due to regenerative power, the hydraulic motor for driving the cargo handling device is rotated to consume part or all of the regenerative power. This prevents the battery from becoming overvoltage.

Japanese Patent No. 4348774

  However, in the conventional forklift, the hydraulic motor is rotated in order to consume regenerative electric power, and thus the rotational sound gives an unpleasant feeling to the operator and those around. In addition, in the conventional forklift, the hydraulic oil rotates due to the rotation of the hydraulic motor, so that the cargo handling device may perform an unintended operation when the cargo handling operation is started (for example, the fork suddenly rises). was there.

  The present invention has been made in view of the above circumstances, and the subject of the present invention is the use of regenerative power without causing discomfort to the operator or those around him or performing unintended operations of the cargo handling device. An object of the present invention is to provide a forklift that can prevent overvoltage of a battery.

  In order to solve the above problems, a forklift according to the present invention includes (1) a battery mounted on a vehicle, a travel motor for traveling the vehicle, and a hydraulic motor for driving a cargo handling device provided on the vehicle. A DC motor supplied from the battery is switched by the switching means to be converted into AC power and supplied to the travel motor, while a power conversion unit for the travel motor that regenerates the regenerative power obtained from the travel motor to the battery, A hydraulic motor power converter that supplies at least DC power supplied from the battery to the hydraulic motor by switching using a switch, and a controller that controls the power converter for the travel motor and the power converter for the hydraulic motor. In the forklift, the control unit does not exceed the first threshold value set in advance by the regenerative power. Sea urchin, characterized in that to consume at least a portion of the regenerative power by the hydraulic motor without rotating the hydraulic motor by controlling the switching means for the hydraulic motor power converting unit.

  According to this configuration, since at least a part of the regenerative power is consumed by the hydraulic motor without rotating the hydraulic motor, uncomfortable feelings for the operator and the surrounding people, or the cargo handling device performs an unintended operation. In addition, overvoltage of the battery due to regenerative power can be prevented.

  In the forklift of the above (1), (2) the control unit controls the hydraulic pressure so that when the battery voltage becomes equal to or higher than the second threshold set lower than the first threshold, at least a part of the regenerative power is consumed by the hydraulic motor. It can be configured to start controlling the switch means of the motor power converter and to increase the duty ratio of the switch means as the battery voltage approaches the first threshold value.

  In the forklift of (2), (3) the control unit can be configured to increase the duty ratio in a range in which the regenerative current flowing through the switch means of the hydraulic motor power conversion unit does not exceed the allowable current value of the switch means. .

  In the forklift of (3) above, (4) when the hydraulic motor is composed of a three-phase induction motor, the control unit switches the switch means of the hydraulic motor power conversion unit so that the regenerative current flows between any two phases of the hydraulic motor. Can be configured to control.

  In the forklifts of the above (1) to (4), (5) the control unit controls the switch means of the power conversion unit for the travel motor to generate the regenerative torque of the travel motor when the battery voltage exceeds the first threshold. Can be configured to restrict.

  ADVANTAGE OF THE INVENTION According to this invention, the forklift which can prevent the overvoltage of the battery by regenerative electric power can be provided, without giving an unpleasant feeling to an operator and the surrounding person, or performing operation | movement which a cargo handling apparatus does not intend.

It is a block diagram of the overvoltage control mechanism with which the forklift which concerns on one Embodiment of this invention was equipped. It is a figure which shows the path | route of the regenerative current which flows through the inverter for hydraulic motors in one Embodiment of this invention. It is a flowchart which shows operation | movement of the control part in one Embodiment of this invention.

  Hereinafter, preferred embodiments of a forklift according to the present invention will be described with reference to the accompanying drawings.

(Constitution)
A forklift according to an embodiment of the present invention includes an overvoltage control mechanism 1 shown in FIG. As shown in the figure, the overvoltage control mechanism 1 includes a battery 2, a travel motor inverter 3 corresponding to the “travel motor power converter” of the present invention, and a “hydraulic motor power converter” of the present invention. The hydraulic motor inverter 4 is equivalent to the control unit 5, and includes a traveling motor M ₁ and a hydraulic motor M ₂ .

  The battery 2 is a lead battery in which a plurality of lead battery cells are connected in series. The battery 2 has a battery voltage that rises to a maximum of about 63V during charging, and stabilizes at about 52V in a fully charged state. A voltage sensor V is connected to the battery 2 in parallel. The voltage sensor V detects a battery voltage output from the battery 2 and transmits a detection result to the control unit 5.

Traveling motor M ₁ is a motor for driving the vehicle, the hydraulic motor M ₂ is a motor for driving the cargo apparatus of the fork or the like. Traveling motor M ₁ and the hydraulic motor M ₂ are both a three-phase induction motor.

As shown in FIG. 2, the hydraulic motor inverter 4 includes six semiconductor switching elements (the “switch” of the present invention) on the U phase, the U phase, the V phase, the V phase, the W phase, and the W phase. has the means _") Q 1 ~Q _6. When driving the cargo handling device, the hydraulic motor inverter 4 converts the supplied DC power into three-phase AC power by the switching operation of the semiconductor switching elements Q _{1 to} Q ₆ performed under the control of the control unit 5. It is supplied to the hydraulic motor _{M 2,} to rotate the hydraulic motor _{M 2.} As the semiconductor switching elements Q _{1 to} Q ₆ , elements capable of high-speed switching operation such as MOS type FET (Field Effect Transistor) and IGBT (Insulated Gate Bipolar Transistor) are used, for example.

Referring again to FIG. 1, current sensors A ₁ and A ₂ are provided on the U-phase and V-phase connection lines among the connection lines between the hydraulic motor inverter 4 and the hydraulic motor M ₂ . The current sensors A ₁ and A ₂ detect a current flowing between the hydraulic motor inverter 4 and the hydraulic motor M ₂ . Also provided is a pulse generator (not shown) in the vicinity of the hydraulic motor M _2. Pulse generator detects the rotational speed of the hydraulic motor M _2. These detection results are all transmitted to the control unit 5.

Similar to the hydraulic motor inverter 4, the traveling motor inverter 3 has six semiconductor switching elements. The traveling motor inverter 3 converts the DC power supplied from the battery 2 into three-phase AC power to the traveling motor M ₁ during the powering operation by the switching operation of the semiconductor switching element performed under the control of the control unit 5. supplied, during regenerative operation, and supplies the three-phase AC power obtained from the travel motor M ₁ that functions to direct-current power is converted to (regenerative power) battery 2 or the hydraulic motor inverter 4 as a generator.

Current sensors A ₃ and A ₄ are provided on the U-phase and V-phase connection lines among the connection lines between the travel motor inverter 3 and the travel motor M ₁ . The current sensors A ₃ and A ₄ detect a current flowing between the traveling motor inverter 3 and the traveling motor M ₁ . Also provided is a pulse generator (not shown) in the vicinity of the traveling motor M _1. Pulse generator detects the rotational speed of the traveling motor M _1. These detection results are all transmitted to the control unit 5.

Control unit 5 determines a command torque of the traveling motor M _1, a power running torque of the driving motor M ₁ (or regenerative torque) to match the indicated torque, the semiconductor switching element included in the travel motor inverter 3 Control the duty ratio. Command torque of the traveling motor M ₁ has a traveling speed obtained from a rotation speed traveling motor M ₁ detected by the pulse generator is determined by the PID control of the target speed obtained from the amount of depression of the accelerator pedal. As described below, traveling a regeneration time of the motor M _1, and the first threshold is a battery voltage detected by the voltage sensor V is set in advance (for example, 63V is the maximum battery voltage during charging) beyond If it is, the control unit 5, in order to lower the regenerative torque of the driving motor M ₁ (limit), by subtracting the predetermined torque set in advance from the instruction torque determined by the PID control, the final instruction Determine the torque.

The control unit 5 also controls the duty ratios of the semiconductor switching elements Q _{1 to} Q ₆ included in the hydraulic motor inverter 4. In particular, when to consume the regenerative electric power at the hydraulic motor M ₂ during regeneration the traveling motor M ₁ is a hydraulic motor M ₂ to control the duty ratio of the semiconductor switching element Q ₁ to Q ₆ so as not to rotate. Details of this control will be described later. The control unit 5 determines the traveling direction of the vehicle set by the operation of the directional lever, and a polarity of the determined indicated torque, whether driving motor M ₁ is regenerated either by powering.

(Operation of control unit during regeneration)
Then, with reference to FIG. 2 and FIG. 3, operation | movement of the control part 5 at the time of regeneration is demonstrated. In FIG. 2, the controller 5, the traveling motor M ₁ , the voltage sensor V, and the current sensors A _{1 to} A ₄ are omitted.

3, the control unit 5, when the running motor M ₁ is determined to be regenerated (Start), (in this embodiment, 55V) battery voltage detected by the voltage sensor V and the second threshold value and Are compared (S1). When the control unit 5 determines that the battery voltage is less than the second threshold value in the comparison in step S1 (NO in S1), the control unit 5 determines the semiconductor switching elements Q _{1 to} Q ₆ of the hydraulic motor inverter 4 unless the cargo handling device is driven. duty ratio (as hydraulic motor inverter 4 does not operate) to be zero, it controls the semiconductor switching element Q ₁ ~Q ₆ (S2). Thereby, all of the regenerative power is regenerated in the battery 2, and the battery voltage rises.

Then, the control unit 5, the regenerative track motors M ₁ to determine whether continued (S3). Control unit 5, the travel motor when the regeneration M ₁ is determined to be completed (in S3 NO), the control is terminated at the time of regeneration of the travel motor inverter 3 (End). On the other hand, if the regeneration of the traveling motor M ₁ is determined to be continued (YES in S3), the control unit 5 again compares the battery voltage and a second threshold value (S1).

When the control unit 5 determines that the battery voltage is equal to or higher than the second threshold value in the comparison in step S1 (YES in S1), the control unit 5 compares the battery voltage with the first threshold value (63V) (S4). Control unit 5, without the battery voltage in the comparison of step S4 when it is determined that less than the first threshold value (NO at S4), and limiting the regenerative torque of the traveling motor M ₁ (without limiting regenerative power), running The semiconductor switching element of the motor inverter 3 is controlled. Furthermore, the control unit 5 controls the semiconductor switching elements Q _{1 to} Q ₆ of the hydraulic motor inverter 4 so that at least a part of the regenerative power is supplied to the hydraulic motor M ₂ (S5).

Specifically, the control unit 5 sets the duty ratios of the semiconductor switching elements Q _{2 to} Q ₄ and Q ₆ to zero so that the regenerative current flows from the U phase to the V phase of the hydraulic motor M ₂ as shown in FIG. The semiconductor switching elements Q ₁ and Q ₅ are turned on at a predetermined (non-zero) duty ratio while the semiconductor switching elements Q _{2 to} Q ₄ and Q ₆ are turned off. Accordingly, the regenerative current flows through the U-V phases of the hydraulic motor M ₂ as a DC current. As a result, the forklift according to the present embodiment, without rotating the hydraulic motor M _2, it is possible to consume regenerative electric power at the hydraulic motor M _2.

The duty ratio is set according to the battery voltage and the allowable current value of the semiconductor switching elements Q _{1 to} Q ₆ . Specifically, the control unit 5, to the extent that regenerative current flowing through the semiconductor switching element Q _1, Q ₅ does not exceed the allowable current value of the semiconductor switching element Q _1, Q _5, the battery voltage is close to the first threshold value The duty ratio is set so as to increase. That is, when the battery voltage is close to the second threshold value and the possibility of damaging elements constituting the control unit 5 or the like is low, the control unit 5 sets the duty ratio to a small value and sets the hydraulic motor M _2. Is reduced (the regenerative power regenerated in the battery 2 is increased). On the other hand, when the battery voltage is close to the first threshold value and there is a high possibility that the elements constituting the control unit 5 and the like will be damaged, the control unit 5 sets the duty ratio to a large value and sets the hydraulic motor M _2. The regenerative power consumed by the battery 2 is increased (the regenerative power regenerated by the battery 2 is reduced). As a result, the forklift according to the present embodiment, while minimizing wasteful consumption of regenerative power by the hydraulic motor M _2, can be prevented in the battery 2 overvoltage (the battery voltage exceeds the first threshold value) and Become.

However, if the regenerative power is very large, be set to (the largest value in the range of or regenerative current does not exceed the allowable current value of the semiconductor switching element Q ₁ to Q ₆₎ the duty ratio is 100%, A part of the regenerative power may be regenerated by the battery 2 and the battery voltage may exceed the first threshold value. In such a case, the control unit 5 determines that the battery voltage exceeds the first threshold in the comparison in step S4 (YES in S4).

Control unit 5, if the battery voltage is determined to exceed the first threshold, the battery voltage is such that the first threshold value, which is preset by the command torque of the traveling motor M ₁ which is determined by the PID control predetermined by subtracting the torque to determine the final indication torque of the traveling motor M _1. Then, the control unit 5, the regenerative torque of the driving motor M ₁ is to match the final indication torque, controls the duty ratio of the semiconductor switching element included in the travel motor inverter 3. This limits the regenerative torque of the driving motor M ₁ is, regenerative electric power obtained from the travel motor M ₁ is reduced.

When regenerative electric power obtained from the travel motor M ₁ is reduced, the control unit 5, so that at least a portion of the reduced regenerative power is supplied to the hydraulic motor M _2, the semiconductor switching elements of the hydraulic motor inverter 4 controlling the Q ₁ ~Q ₆ (S7). In the case already regenerative power is being supplied to the hydraulic motor M ₂ at the time of step S6, the step S7 is omitted.

Then, the control unit 5, the regenerative track motors M ₁ to determine whether continued (S3). Control unit 5, when the regeneration of the traveling motor M ₁ is determined to be completed (in S3 NO), ends the control of the travel motor inverter 3 (End). On the other hand, if the regeneration of the traveling motor M ₁ is determined to be continued (YES in S3), the control unit 5 again compares the battery voltage and a second threshold value (S1).

After all, according to the forklift according to the present embodiment, it is possible to consume the regenerative electric power at the hydraulic motor M ₂ without rotating the hydraulic motor M _2, or discomfort to a person of the operator and surrounding, cargo handling device However, overvoltage of the battery 2 due to regenerative power can be prevented without performing an unintended operation.

  The preferred embodiment of the forklift according to the present invention has been described above, but the present invention is not limited to the above embodiment.

For example, the control unit 5 in the above embodiment, the battery voltage is equal to or greater than the second threshold value, but by consuming regenerative power at the hydraulic motor M ₂ by controlling the hydraulic motor inverter 4, instead of this, the battery when the voltage reaches a first threshold value, it may be consumed the regenerative power in the hydraulic motor M ₂ by controlling the hydraulic motor inverter 4 as the battery voltage does not exceed the first threshold value.

  In the above embodiment, the first threshold value is set to 63V and the second threshold value is set to 55V. If it is above (however, the first threshold> the second threshold), the first threshold and the second threshold can be arbitrarily changed.

  In the above embodiment, the battery voltage is compared with the second threshold value in step S1, and the battery voltage is compared with the first threshold value in step S4. However, these comparisons may be performed simultaneously.

In the above embodiment, in order to consume the regenerative electric power at the hydraulic motor M ₂ without rotating the hydraulic motor M _2, although passing a regenerative current to the V-phase from the U-phase of the hydraulic motor M _2, U-phase and V any regenerative current between two phases of the hydraulic motor M ₂ is not limited to phase can flow. Furthermore, after flowing the regenerative current from the U phase to the V phase, the regenerative current is flowed from the U phase to the W phase, and the regenerative current is again flowed from the U phase to the V phase. while, the hydraulic motor M ₂ may also be consumed the regenerative power in the hydraulic motor M ₂ so as not to rotate.

In the above embodiment, the semiconductor switching elements Q ₁ and Q ₅ are turned on with a predetermined duty ratio when a regenerative current (DC current) flows between the U and V phases of the hydraulic motor M _2. The semiconductor switching element Q ₅ (or Q ₁ ) may be turned on with a predetermined duty ratio while the switching element Q ₁ (or Q ₅ ) is turned on.

In the present invention, if it is possible to consume the regenerative electric power at the hydraulic motor M ₂ without rotating the hydraulic motor M _2, the duty ratio of the semiconductor switching element Q ₁ to Q ₆ can be arbitrarily changed.

1 Overvoltage control mechanism 2 Battery 3 Travel motor inverter (travel motor power converter)
4 Hydraulic motor inverter (hydraulic motor power converter)
5 Control unit M ₁ Travel motor M ₂ Hydraulic motor

In order to solve the above problems, a forklift according to the present invention includes (1) a battery mounted on a vehicle, a travel motor for traveling the vehicle, and a hydraulic motor for driving a cargo handling device provided on the vehicle. A DC motor supplied from the battery is switched by the switching means to be converted into AC power and supplied to the travel motor, while a power conversion unit for the travel motor that regenerates the regenerative power obtained from the travel motor to the battery, A hydraulic motor power converter that supplies at least DC power supplied from the battery to the hydraulic motor by switching using a switch, and a controller that controls the power converter for the travel motor and the power converter for the hydraulic motor. In the forklift, the control unit does not exceed the first threshold value set in advance by the regenerative power. Sea urchin, causes to consume at least a portion of the regenerative power by the hydraulic motor without rotating the hydraulic motor by controlling the switching means for the hydraulic motor power conversion unit, the battery voltage is set lower than the first threshold value 2 When the threshold value is exceeded, control of the switch means of the hydraulic motor power conversion unit is started so that at least part of the regenerative power is consumed by the hydraulic motor, and the duty ratio of the switch means is increased as the battery voltage approaches the first threshold value. It is characterized by increasing .

In the forklift of ( 1 ), ( 2 ) the control unit can be configured to increase the duty ratio within a range in which the regenerative current flowing through the switch means of the hydraulic motor power conversion unit does not exceed the allowable current value of the switch means. .

In the forklift of ( 2 ), ( 3 ) when the hydraulic motor is composed of a three-phase induction motor, the control unit switches the switching means of the hydraulic motor power conversion unit so that the regenerative current flows between any two phases of the hydraulic motor. Can be configured to control.

In the forklift of the above (1) to (3), (4) the control unit, when the battery voltage exceeds the first threshold value, the regenerative torque of the traveling motor by controlling the switching means of the power conversion unit for driving the motor Can be configured to restrict.

Claims (5)

A battery mounted on the vehicle;
A travel motor for traveling the vehicle;
A hydraulic motor for driving a cargo handling device provided in the vehicle;
DC power supplied from the battery is switched by switch means to be converted into AC power and supplied to the travel motor, while a power conversion unit for travel motor that regenerates the regenerative power obtained from the travel motor to the battery. When,
A power conversion unit for a hydraulic motor that switches at least DC power supplied from the battery by a switch means and supplies the DC motor to the hydraulic motor;
A control unit for controlling the power conversion unit for the travel motor and the power conversion unit for the hydraulic motor;
A forklift with
The control unit rotates the hydraulic motor by controlling the switch unit of the hydraulic motor power conversion unit so that the battery voltage of the battery does not exceed a preset first threshold value due to the regenerative power. A forklift characterized in that at least a part of the regenerative power is consumed by the hydraulic motor.   When the battery voltage is equal to or higher than a second threshold value set lower than the first threshold value, the control unit is configured so that at least a part of the regenerative power is consumed by the hydraulic motor. 2. The forklift according to claim 1, wherein the duty ratio of the switch means is increased as the battery voltage starts to be controlled and the battery voltage approaches the first threshold value.   The said control part increases the said duty ratio in the range in which the regenerative current which flows into the said switch means of the said electric power conversion part for hydraulic motors does not exceed the allowable electric current value of the said switch means. Forklift. The hydraulic motor is a three-phase induction motor,
The forklift according to claim 3, wherein the control unit controls the switch means of the hydraulic motor power conversion unit so that the regenerative current flows between any two phases of the hydraulic motor.   The said control part controls the regenerative torque of the said traveling motor by controlling the said switch means of the electric power conversion part for said traveling motor, when the said battery voltage exceeds the said 1st threshold value. The forklift in any one of 1-4.

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