Industrial vehicle

Abstract

To allow a rotational speed of a traveling motor to smoothly follow a target rotational speed.SOLUTION: An industrial vehicle includes: a traveling motor; an inverter for driving the traveling motor; and a controller for controlling the inverter. The controller calculates a deviation between a rotational speed of the traveling motor and a target rotational speed. The controller calculates an output ratio on the basis of the deviation between the rotational speed of the traveling motor and the target rotational speed, a proportional gain, and an integral gain. The controller multiplies the output ratio and a torque current curve together, thereby calculating a torque current command value. The controller converts the torque current command value into a command value for the inverter, thereby controlling the traveling motor so that the rotational speed of the motor follows the target rotational speed. When the industrial vehicle is braked, the controller sets the integral gain on the basis of a maximum value of the output ratio in a state where the rotational speed is equal to or less than a base rotational speed.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to industrial vehicles. [Background technology]

[0002] The vehicle disclosed in Patent Document 1 includes a travel motor, an inverter that drives the travel motor, and a control device that controls the inverter. The control device drives the vehicle by powering the travel motor. The control device brakes the vehicle by regenerating power from the travel motor. When the control device brakes the vehicle by regenerating power from the travel motor, feedback control is performed so that the rotation speed of the travel motor follows a target rotation speed. The feedback control is, for example, proportional-integral control. The industrial vehicle disclosed in Patent Document 2 transports loads. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-68596 A [Patent Document 2] JP 2023-46547 A Summary of the Invention [Problem to be solved by the invention]

[0004] When feedback control is performed as disclosed in Patent Document 1, a proportional gain and an integral gain are set. Then, control is performed based on the proportional gain and the integral gain, so that the rotation speed of the traveling motor follows the target rotation speed. When an integral gain is set when controlling an industrial vehicle as in Patent Document 1, the integral gain when stopping the industrial vehicle is set so that the rotation speed of the traveling motor smoothly follows the target rotation speed when no load is being transported. In this case, when stopping an industrial vehicle that is transporting a load, the rotation speed of the traveling motor may not smoothly follow the target rotation speed. [Means for solving the problem]

[0005] The industrial vehicle that solves the above problem is an industrial vehicle capable of transporting loads, and includes a traveling motor, an inverter that drives the traveling motor, and a control device that controls the inverter, wherein the control device calculates the deviation between the rotation speed of the traveling motor and a target rotation speed, calculates an output ratio based on the deviation, a proportional gain, and an integral gain, calculates a torque current command value by multiplying the output ratio by a torque current curve, and controls the traveling motor so that the rotation speed of the traveling motor follows the target rotation speed by converting the torque current command value into a command value for the inverter, and sets the integral gain based on the maximum value of the output ratio when the rotation speed of the traveling motor is below the base rotation speed when the industrial vehicle is braking.

[0006] When the rotation speed of the traveling motor is below the base rotation speed, the maximum value of the output rate changes according to the weight of the load. Therefore, by setting the integral gain based on the maximum value of the output rate when the rotation speed of the traveling motor is below the base rotation speed, it is possible to set the integral gain according to the weight of the load. By calculating the output rate using this integral gain, it is possible to make the rotation speed of the traveling motor smoothly follow the target rotation speed when the industrial vehicle is stopped.

[0007] For the above-mentioned industrial vehicle, the control device may hold the maximum value calculated while the rotation speed of the traveling motor is maintained below the base rotation speed, and when the output ratio is calculated while the rotation speed of the traveling motor is maintained below the base rotation speed, if the calculated output ratio is greater than the held maximum value, the calculated output ratio may be held as a new maximum value.

[0008] For the above industrial vehicle, the control device may set an unloaded integral gain as the integral gain when the maximum value is equal to or less than a no-load output ratio reference value, set a maximum load integral gain as the integral gain when the maximum value is equal to or greater than a maximum load output ratio reference value, and set a linear interpolation integral gain obtained by linearly interpolating between the no-load integral gain and the maximum load integral gain as the integral gain when the maximum value is greater than the no-load output ratio reference value and less than the maximum load output ratio reference value, wherein the no-load output ratio reference value is set so that the maximum value is equal to or less than the no-load output ratio reference value when the industrial vehicle is not transporting a load, and the maximum load output ratio reference value is set so that the maximum value is equal to or more than the maximum load output ratio reference value when the industrial vehicle is transporting a load of the maximum weight that the industrial vehicle can transport.

[0009] For the above industrial vehicle, the integral gain may be associated with each of a plurality of categories into which a range in which the maximum value can be taken is divided, and the control device may set the integral gain associated with the category to which the maximum value belongs.

[0010] The above industrial vehicle may be provided with only the travel motor as a braking device. Effect of the Invention

[0011] According to the present invention, the rotation speed of the traveling motor can be made to smoothly follow the target rotation speed. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view showing an industrial vehicle. [Diagram 2] FIG. 2 is a schematic diagram of an industrial vehicle. [Diagram 3] FIG. 3 is a schematic diagram showing the function of the output ratio determination unit. [Figure 4] FIG. 4 is a flowchart showing the maximum output ratio calculation control. [Diagram 5]FIG. 5 is a flowchart showing the integral gain calculation control. [Figure 6] FIG. 6 is a diagram showing the correspondence relationship between the rotation speed of the traveling motor and the output ratio when deceleration starts. [Figure 7] FIG. 7 is a diagram showing the correspondence relationship between the load and the maximum output rate. [Figure 8] FIG. 8 is a diagram showing the correspondence relationship between the maximum output rate and the integral gain. [Figure 9] FIG. 9 is a diagram showing the rotation speed command, the target rotation speed, the output ratio, and the actual rotation speed when an industrial vehicle transporting a load is stopped with the no-load integral gain set as the integral gain. [Figure 10] FIG. 10 is a diagram showing the rotation speed command, the target rotation speed, the output ratio, and the actual rotation speed when an industrial vehicle in an unloaded state is stopped on a flat road. [Figure 11] FIG. 11 is a diagram showing the rotation speed command, the target rotation speed, the output ratio, and the actual rotation speed when an industrial vehicle in a maximum load state is stopped on a flat road. [Figure 12] FIG. 12 is a diagram showing the rotation speed command, the target rotation speed, the output ratio, and the actual rotation speed when an industrial vehicle in a maximum load state is stopped on a slope. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] An embodiment of an industrial vehicle will be described below. <Industrial vehicles> As shown in FIG. 1, the industrial vehicle 10 is equipped with driving wheels 12 and steering wheels 13. The industrial vehicle 10 is a forklift. The forklift may be of a counter type or a reach type. The industrial vehicle 10 is equipped with forks 14. A load L is loaded on the forks 14. The industrial vehicle 10 is capable of transporting the load L loaded on the forks 14.

[0014] As shown in Fig. 2, the industrial vehicle 10 includes a battery 21. The battery 21 is formed by connecting a plurality of power storage devices, for example. Any power storage device may be used as long as it is capable of charging and discharging. The power storage device is, for example, a lead storage battery, a lithium ion secondary battery, or a nickel metal hydride storage battery.

[0015] The industrial vehicle 10 includes an inverter 22. The inverter 22 is, for example, a three-phase inverter that converts DC power into three-phase AC power. The inverter 22 is electrically connected to a battery 21. The inverter 22 converts DC power input from the battery 21 into AC power and outputs the AC power. The inverter 22 includes, for example, a switching element 23, and converts the DC power into AC power by the switching operation of the switching element 23.

[0016] The industrial vehicle 10 includes a travel motor 24. The travel motor 24 is, for example, a three-phase AC rotating electric machine. The travel motor 24 is driven by an inverter 22. When power is supplied from the inverter 22, the travel motor 24 operates as an electric motor to generate rotational driving force. This rotational driving force is transmitted to the drive wheels 12 through the axles, causing the industrial vehicle 10 to travel. When braking the industrial vehicle 10, the travel motor 24 operates as a generator to generate regenerative power. The power generated by the travel motor 24 is supplied to the battery 21 through the inverter 22 as regenerative power. In this way, the travel motor 24 is a motor generator that performs power running and regeneration.

[0017] The industrial vehicle 10 is braked by a regenerative braking force generated by the traveling motor 24. The industrial vehicle 10 is not equipped with a mechanical brake such as a disk brake or a drum brake. Therefore, the industrial vehicle 10 is equipped only with the traveling motor 24 as a braking device.

[0018] When the industrial vehicle 10 includes a plurality of drive wheels 12, a travel motor 24 may be provided for each drive wheel 12. In this case, the inverter 22 may be provided for each travel motor 24.

[0019] The industrial vehicle 10 includes an accelerator member 25. The accelerator member 25 is a member that is operated when the industrial vehicle 10 is driven. When the industrial vehicle 10 is a counter type forklift, the accelerator member 25 is, for example, an accelerator pedal. When the industrial vehicle 10 is a reach type forklift, the accelerator member 25 is, for example, a direction lever.

[0020] The industrial vehicle 10 is equipped with an accelerator sensor 26. The accelerator sensor 26 detects the amount of operation of the accelerator member 25. The accelerator sensor 26 outputs an electric signal according to the amount of operation of the accelerator member 25.

[0021] The industrial vehicle 10 is equipped with a rotation speed sensor 27. The rotation speed sensor 27 outputs an electric signal according to the rotation speed [rpm] of the traveling motor 24. The rotation speed sensor 27 is, for example, a resolver or an encoder.

[0022] The industrial vehicle 10 is equipped with a phase current detection unit 28. The phase current detection unit 28 detects the phase currents flowing through the travel motor 24. The phase current detection unit 28 detects the phase currents for at least two phases. It is also possible to detect the phase currents for two of the three phases, and calculate the phase current for the remaining phase from the phase currents for the two phases.

[0023] The industrial vehicle 10 includes a control device 30. The control device 30 includes a processor and a storage unit. The processor is, for example, a central processing unit (CPU), a graphics processing unit (GPU), or a digital signal processor (DSP). The storage unit includes a random access memory (RAM) and a read only memory (ROM). The storage unit stores a program for operating the industrial vehicle 10. The storage unit stores program code or instructions configured to cause the processor to execute processing. The storage unit, i.e., a computer-readable medium, includes any available medium accessible by a general-purpose or dedicated computer. The control device 30 may be configured by a hardware circuit such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA). The control device 30, which is a processing circuit, may include one or more processors that operate according to a computer program, one or more hardware circuits such as an ASIC or an FPGA, or a combination thereof.

[0024] The control device 30 obtains an electrical signal from the accelerator sensor 26. The control device 30 recognizes the accelerator operation amount from the electrical signal obtained from the accelerator sensor 26. The control device 30 obtains an electrical signal from the rotation speed sensor 27. The control device 30 recognizes the rotation speed of the traveling motor 24 from the electrical signal obtained from the rotation speed sensor 27. The rotation speed of the traveling motor 24 recognized by the rotation speed sensor 27 is appropriately referred to as the actual rotation speed. The sign of the actual rotation speed [rpm] is reversed (+ or -) depending on the rotation direction of the traveling motor 24. For example, if the actual rotation speed is +, it is a forward rotation, and if the actual rotation speed is -, it is a reverse rotation.

[0025] The control device 30 controls the inverter 22. The control device 30 includes an output ratio determination unit 41, a torque current command calculation unit 31, and a voltage command calculation unit 32. The output ratio determination unit 41, the torque current command calculation unit 31, and the voltage command calculation unit 32 are functional units that function as the control device 30 executes predetermined processing.

[0026] The output ratio determination unit 41 determines the output ratio [%]. The torque current command calculation unit 31 calculates a torque current command value. The torque current command value may also be referred to as a q-axis current command value. The torque current command calculation unit 31 calculates the torque current command value by multiplying the output ratio determined by the output ratio determination unit 41 by a torque current curve.

[0027] The voltage command calculation unit 32 calculates a voltage command value based on the deviation between the torque current command value and the torque current, and the deviation between the excitation current command value and the excitation current. The excitation current command value is calculated by the control device 30. The excitation current command value is sometimes referred to as a d-axis current command value. The torque current is a component of the current flowing through the traveling motor 24 that generates torque. The excitation current is a component of the current flowing through the traveling motor 24 that generates magnetic flux. The torque current and the excitation current can be calculated from the phase current. The voltage command calculation unit 32 calculates a voltage command value so that the deviation between the torque current command value and the torque current, and the deviation between the excitation current command value and the excitation current are reduced. The inverter 22 is controlled based on the voltage command value. The voltage command value is a command value for the inverter 22. In this way, the control device 30 converts the torque current command value into a command value for the inverter 22 to control the traveling motor 24 so that the rotation speed of the traveling motor 24 follows the target rotation speed.

[0028] As shown in FIG. 3, the output ratio determination unit 41 includes a target rotation speed calculation unit 42, a subtraction unit 43, an output ratio calculation unit 44, a proportional gain calculation unit 45, and an integral gain calculation unit 46. The target rotation speed calculation unit 42 calculates the target rotation speed based on a rotation speed command, an acceleration command, and a deceleration command. The rotation speed command is calculated based on, for example, an accelerator operation amount. The acceleration command is calculated based on, for example, a deviation between the target rotation speed and the actual rotation speed. The deceleration command is calculated based on, for example, a deviation between the target rotation speed and the actual rotation speed. The target rotation speed is a target value of the rotation speed that causes the actual rotation speed to follow the acceleration specified by the acceleration command or the deceleration specified by the deceleration command.

[0029] The subtraction unit 43 calculates a speed deviation, which is the deviation between the target rotation speed and the actual rotation speed. The output ratio calculation unit 44 calculates the output ratio based on the speed deviation, the proportional gain, and the integral gain. The output ratio calculation unit 44 calculates the output ratio based on the proportional gain and the integral gain so that the speed deviation approaches 0. The output ratio determination unit 41 calculates the output ratio by proportional-integral control as feedback control. When braking the industrial vehicle 10, the output ratio determination unit 41 performs control so that the integral term acts on the speed deviation when the target rotation speed is 0. When braking the industrial vehicle 10, the output ratio determination unit 41 performs control so that the integral term does not act on the speed deviation when the target rotation speed is a value other than 0.

[0030] When the traveling motor 24 is powered, the actual rotation speed and the output ratio are the same in sign. When the traveling motor 24 is regenerating, the actual rotation speed and the output ratio are different in sign. For example, when the traveling motor 24 is powered, if the actual rotation speed is a positive value, the output ratio is a positive value. When the traveling motor 24 is regenerating, if the actual rotation speed is a positive value, the output ratio is a negative value.

[0031] The proportional gain calculation unit 45 calculates the proportional gain. The proportional gain is calculated based on, for example, the accelerator operation amount and the actual rotation speed of the travel motor 24. The proportional gain is a coefficient of the proportional term used in proportional-integral control.

[0032] The integral gain calculation unit 46 calculates the integral gain. The integral gain is calculated based on the output ratio. The integral gain is a coefficient of an integral term used in proportional-integral control. The control performed by the integral gain calculation unit 46 will be described below.

[0033] <Maximum output ratio calculation control> The integral gain calculation unit 46 performs maximum output ratio calculation control at a predetermined control period. As shown in FIG. 4, in step S1, the integral gain calculation unit 46 judges whether the rotation speed command is 0 or not. The rotation speed command becomes 0 when the accelerator member 25 is not operated. Therefore, by judging whether the rotation speed command is 0 or not, it is possible to judge whether the accelerator member 25 has stopped being operated or is continuing to be operated. If the judgment result of step S1 is negative, the integral gain calculation unit 46 performs processing of step S21. In step S21, the integral gain calculation unit 46 sets the maximum output ratio to 0. That is, the integral gain calculation unit 46 resets the maximum output ratio and ends the maximum output ratio calculation control. The maximum output ratio is the maximum value of the output ratio. If the judgment result of step S1 is positive, the integral gain calculation unit 46 performs processing of step S2.

[0034] In step S2, the integral gain calculation unit 46 holds the previous value of the maximum output ratio. Next, in step S3, the integral gain calculation unit 46 judges whether the absolute value of the actual rotation speed is equal to or lower than the base rotation speed and whether the target rotation speed is a value different from 0. The base rotation speed is a rotation speed determined by the rotation speed-torque characteristic. The rotation speed-torque characteristic is a characteristic of the travel motor 24 when the horizontal axis is the rotation speed and the vertical axis is the torque. The torque remains constant up to a certain rotation speed, and when the rotation speed exceeds the certain rotation speed, it decreases as the rotation speed increases. In this way, the rotation speed that is the boundary with the region where the torque decreases as the rotation speed increases is the base rotation speed. If the judgment result of step S3 is negative, the integral gain calculation unit 46 performs the process of step S22. In step S22, the integral gain calculation unit 46 holds the previous value of the maximum output ratio and proceeds to step S10. If the judgment result of step S3 is positive, the integral gain calculation unit 46 performs the process of step S4.

[0035] In step S4, the integral gain calculation unit 46 determines whether the actual rotation speed is equal to or greater than 0. If the determination result in step S4 is positive, the integral gain calculation unit 46 performs processing in step S5. In step S5, the integral gain calculation unit 46 sets the output ratio multiplied by -1 as the output ratio local. If the determination result in step S4 is negative, the integral gain calculation unit 46 performs processing in step S6. In step S6, the integral gain calculation unit 46 sets the output ratio as the output ratio local.

[0036] In steps S4 to S6, when the actual rotation speed is positive, the negative side of the output ratio is the regenerative direction, so the output ratio is multiplied by -1. By performing the processing in steps S4 to S6, a positive value local output ratio can be obtained regardless of whether the actual rotation speed is positive or negative. In other words, the local output ratio is an output ratio that is always a positive value.

[0037] Next, in step S7, the integral gain calculation unit 46 determines whether the held maximum output ratio is less than the local output ratio. If the determination result in step S7 is positive, the integral gain calculation unit 46 performs processing in step S8. In step S8, the integral gain calculation unit 46 sets the maximum output ratio to the local output ratio. If the determination result in step S7 is negative, the integral gain calculation unit 46 performs processing in step S9. In step S9, the integral gain calculation unit 46 holds the previous value of the maximum output ratio.

[0038] In steps S7 to S9, if the local output ratio is greater than the maximum output ratio held, the integral gain calculation unit 46 sets the maximum output ratio to the local output ratio. That is, the maximum output ratio is updated to the local output ratio obtained in steps S4 to S6. Steps S7 to S9 are performed when the determination result in step S3 is positive. If the determination result in step S3 is negative, the process proceeds to step S10 without performing the processes in steps S7 to S9. If the actual rotation speed is equal to or lower than the base rotation speed, the maximum output ratio is updated in steps S7 to S9. Therefore, by continuing the processes in steps S7 to S9 until the determination result in step S3 is negative, the maximum output ratio in the state where the actual rotation speed is equal to or lower than the base rotation speed can be obtained. Then, when the determination result in step S3 is negative, the previous value of the maximum output ratio is held, so that the maximum output ratio is maintained at the maximum value of the output ratio in the state where the actual rotation speed is equal to or lower than the base rotation speed. When the determination result in step S7 is negative, the process of step S9 is performed, whereby the integral gain calculation unit 46 holds the maximum output ratio calculated while the rotation speed of the traveling motor 24 is maintained at or below the base rotation speed. When the determination result in step S7 is positive, the process of step S8 is performed, whereby when the output ratio is calculated while the rotation speed of the traveling motor 24 is maintained at or below the base rotation speed, the integral gain calculation unit 46 holds the calculated output ratio as a new maximum output ratio if the calculated output ratio is greater than the held maximum output ratio.

[0039] Next, in step S10, the integral gain calculation unit 46 judges whether the absolute value of the actual rotation speed is greater than the base rotation speed and the target rotation speed is 0. If the judgment result in step S10 is positive, the integral gain calculation unit 46 performs processing in step S11. In step S11, the integral gain calculation unit 46 sets the maximum output ratio to 100[%] and ends the maximum output ratio calculation control. If the judgment result in step S10 is negative, the integral gain calculation unit 46 ends the maximum output ratio calculation control. During regeneration, if the absolute value of the actual rotation speed is greater than the base rotation speed and the target rotation speed is 0, the output ratio calculated by the output ratio calculation unit 44 becomes 100[%]. Therefore, if the absolute value of the actual rotation speed is greater than the base rotation speed and the target rotation speed is 0, the maximum output ratio is maintained at 100%. This prevents the maximum output ratio from becoming less than 100 even if the absolute value of the actual rotation speed is greater than the base rotation speed and the target rotation speed is 0.

[0040] <Integral gain calculation control> The integral gain calculation unit 46 performs integral gain calculation control at a predetermined control period. The integral gain calculation control is control for calculating an integral gain from the maximum output rate held by the maximum output rate calculation control.

[0041] As shown in Fig. 5, in step S31, the integral gain calculation unit 46 determines whether the held maximum output ratio is equal to or less than a no-load output ratio reference value. The no-load output ratio reference value is a predetermined value. The no-load output ratio reference value will be described in detail below.

[0042] FIG. 6 shows the relationship between the output ratio and the rotation speed of the traveling motor 24 at the start of deceleration when the load value is changed. The load is the weight of the load L. In the example shown in FIG. 6, the load is set to 0 [kg], 500 [kg], 1000 [kg], 2000 [kg], or 2500 [kg]. In FIG. 6, ○ indicates 0 [kg], □ indicates 500 [kg], △ indicates 1000 [kg], × indicates 2000 [kg], and ◇ indicates 2500 [kg]. 0 [kg] is a state in which the industrial vehicle 10 is not carrying the load L. This state is an unloaded state. 2500 [kg] is a state in which the industrial vehicle 10 is loaded with the maximum weight of the load L that the industrial vehicle 10 can carry. This state is a maximum load state. The maximum weight of the load L that the industrial vehicle 10 can carry is determined, for example, by the specifications of the industrial vehicle 10.

[0043] In the range below the base rotation speed, the torque of the traveling motor 24 changes approximately linearly with an increase in the torque current. Therefore, if it is possible to derive the maximum possible output ratio below the base rotation speed, it is possible to estimate the load according to the magnitude of the output of the traveling motor 24.

[0044] As shown in Fig. 6, in the region below the base rotation speed, the lower the rotation speed of the traveling motor 24 at the start of deceleration, the lower the output ratio. Also, the heavier the load, the larger the maximum value of the output ratio in the region below the base rotation speed. Therefore, the load can be estimated from the maximum value of the output ratio in the region below the base rotation speed.

[0045] FIG. 7 shows the results of experimentally measuring the maximum output ratio in the no-load state in the range below the base rotation speed, and the maximum output ratio in the maximum load state in the range below the base rotation speed. From these results, the no-load output ratio reference value for determining the no-load state and the maximum load output ratio reference value for determining the maximum load state are set. For example, the maximum output ratio in the no-load state may be acquired multiple times, and the no-load output ratio reference value may be set based on the average value or median value of the maximum output ratio in the no-load state. The maximum output ratio in the maximum load state may be acquired multiple times, and the maximum load output ratio reference value may be set based on the average value or median value of the maximum output ratio in the maximum load state. The no-load output ratio reference value is set to, for example, 45[%]. The maximum load output ratio reference value is set to, for example, 98[%]. The no-load output ratio reference value and the maximum load output ratio reference value may be set to different values ​​depending on the type of the industrial vehicle 10 and the type of the travel motor 24. The no-load output ratio standard value is set so that the maximum output ratio in the range below the base rotation speed is equal to or less than the no-load output ratio standard value when the industrial vehicle 10 is not transporting a load L. The maximum load output ratio standard value is set so that the maximum output ratio in the range below the base rotation speed is equal to or more than the maximum load output ratio standard value when the industrial vehicle 10 is transporting a load L of the maximum weight that it can transport.

[0046] As shown in FIG. 8, the integral gain is set to vary according to the maximum output ratio held. The integral gain is set corresponding to the no-load output ratio reference value and the maximum load output ratio reference value. The integral gain corresponding to the no-load output ratio reference value is referred to as the no-load integral gain. The no-load integral gain is set to a value suitable for the industrial vehicle 10 in an unloaded state. That is, the no-load integral gain is set so that the actual rotation speed smoothly follows the target rotation speed when the industrial vehicle 10 in an unloaded state is stopped. The integral gain corresponding to the maximum load output ratio reference value is referred to as the maximum load integral gain. The maximum load integral gain is set to a value suitable for the industrial vehicle 10 in a maximum load state. That is, the maximum load integral gain is set so that the actual rotation speed smoothly follows the target rotation speed when the industrial vehicle 10 in a maximum load state is stopped.

[0047] 5, when the determination result in step S31 is positive, the integral gain calculation unit 46 performs the process of step S32. In step S32, the integral gain calculation unit 46 sets the no-load integral gain as the integral gain and ends the integral gain calculation control.

[0048] If the determination result in step S31 is negative, the integral gain calculation unit 46 performs a determination in step S33. In step S33, the integral gain calculation unit 46 judges whether the held maximum output ratio is equal to or greater than a maximum load output ratio reference value. The maximum load output ratio reference value is a predetermined value. If the judgment result in step S33 is positive, the integral gain calculation unit 46 performs processing in step S34. In step S34, the integral gain calculation unit 46 sets the maximum load integral gain as the integral gain and ends the integral gain calculation control.

[0049] If the determination result in step S33 is negative, the integral gain calculation unit 46 performs the process of step S35. In step S35, the integral gain calculation unit 46 sets the linear interpolation integral gain as the integral gain, and ends the integral gain calculation control.

[0050] As shown in Figure 8, the linearly interpolated integral gain is an integral gain obtained by linearly interpolating between the no-load integral gain and the maximum load integral gain. In the region below the base rotation speed, the maximum output ratio changes linearly with an increase in load. Therefore, by setting the linearly interpolated integral gain as the integral gain, the integral gain according to the load is set.

[0051] [Operation of this embodiment] When the industrial vehicle 10 is stopped, braking is performed by the regenerative braking force generated by the travel motor 24. At this time, the control device 30 controls the actual rotation speed so as to follow the target rotation speed.

[0052] 9 to 12 show the relationship between the rotation speed command, the target rotation speed, the actual rotation speed, and the output ratio. In Fig. 9 to Fig. 12, line L1 shows the rotation speed command, line L2 shows the target rotation speed, line L3 shows the actual rotation speed, and line L4 shows the output ratio.

[0053] FIG. 9 shows, as a comparative example, a change in the actual rotation speed when the industrial vehicle 10 transporting a load L is stopped with the unloaded integral gain set as the integral gain. The unloaded integral gain is an integral gain suitable for the industrial vehicle 10 not transporting the load L. For this reason, when the unloaded integral gain is set as the integral gain for the industrial vehicle 10 transporting the load L, it cannot be said that an appropriate integral gain is set. As a result, as shown in FIG. 9, a swing back occurs when the industrial vehicle 10 is stopped, and the actual rotation speed does not smoothly follow the target rotation speed.

[0054] Fig. 10 shows the change in actual rotation speed when the industrial vehicle 10 of this embodiment in an unloaded state is stopped on a flat road. In the unloaded state, the unloaded integral gain is set as an integral gain according to the maximum output ratio in the range below the base rotation speed. Then, when the industrial vehicle 10 is stopped, the actual rotation speed smoothly follows the target rotation speed.

[0055] Fig. 11 shows the change in actual rotation speed when the industrial vehicle 10 of this embodiment in a fully loaded state is stopped on a flat road. In the fully loaded state, the maximum load integral gain is set as an integral gain according to the maximum output ratio in the range below the base rotation speed. Then, when the industrial vehicle 10 is stopped, the actual rotation speed smoothly follows the target rotation speed.

[0056] 12 shows the change in actual rotation speed when the industrial vehicle 10 of this embodiment in a fully loaded state is stopped on a slope. In the fully loaded state, the maximum load integral gain is set as an integral gain according to the maximum output ratio in the range below the base rotation speed. Then, when the industrial vehicle 10 is stopped, the actual rotation speed smoothly follows the target rotation speed.

[0057] 10 to 12, the industrial vehicle 10 of this embodiment can be stopped smoothly when braking, regardless of the load. Moreover, the industrial vehicle 10 can be stopped smoothly when braking, regardless of whether the vehicle is on a flat road or a slope.

[0058] [Effects of this embodiment] (1) When braking the industrial vehicle 10, the control device 30 sets the integral gain based on the maximum output rate when the rotation speed of the traveling motor 24 is equal to or lower than the base rotation speed. In the region where the rotation speed of the traveling motor 24 is equal to or lower than the base rotation speed, the maximum output rate changes according to the weight of the load L. Therefore, by setting the integral gain based on the maximum output rate when the rotation speed of the traveling motor 24 is equal to or lower than the base rotation speed, it is possible to set an integral gain according to the weight of the load L. By calculating the output rate using this integral gain, the rotation speed of the traveling motor 24 can be made to smoothly follow the target rotation speed when the industrial vehicle 10 is stopped.

[0059] (2) The control device 30 holds the maximum output ratio calculated while the rotation speed of the traveling motor 24 is maintained at or below the base rotation speed. When the output ratio is calculated while the rotation speed of the traveling motor 24 is maintained at or below the base rotation speed, if the calculated output ratio is greater than the held maximum output ratio, the control device 30 holds the calculated output ratio as a new maximum output ratio. This allows the control device 30 to recognize the maximum output ratio calculated while the rotation speed of the traveling motor 24 is maintained at or below the base rotation speed.

[0060] (3) When the maximum output ratio is equal to or less than the no-load output ratio reference value, the control device 30 sets the no-load integral gain as the integral gain. When the maximum output ratio is equal to or greater than the maximum load output ratio reference value, the control device 30 sets the maximum load integral gain as the integral gain. When the maximum output ratio is greater than the no-load output ratio reference value and less than the maximum load output ratio reference value, the control device 30 sets the linear interpolation integral gain as the integral gain. This makes it possible to set an integral gain suitable for the weight of the load L. Also, if the no-load integral gain and the maximum load integral gain are determined in advance, the linear interpolation integral gain can be derived by linear interpolation. This eliminates the need to determine the integral gain individually according to the weight of the load L.

[0061] (4) The industrial vehicle 10 is equipped with only the traveling motor 24 as a braking device. When stopping the industrial vehicle 10 using only the braking force of the traveling motor 24, it is necessary to stop the industrial vehicle 10 by controlling the rotation speed of the traveling motor 24. In this case, it is necessary to make the rotation speed of the traveling motor 24 smoothly follow the target rotation speed. By setting an integral gain according to the weight of the load L as in this embodiment, it is possible to make the rotation speed of the traveling motor 24 smoothly follow the target rotation speed when stopping the industrial vehicle 10. Therefore, even an industrial vehicle 10 that does not have a mechanical brake can be stopped smoothly.

[0062] (5) In step S3, the integral gain calculation unit 46 judges whether the absolute value of the actual rotation speed is equal to or less than the base rotation speed and whether the target rotation speed is a value different from 0. When braking the industrial vehicle 10, the output ratio determination unit 41 performs control so that the integral term acts on the speed deviation when the target rotation speed is 0. This is because, if control is performed so that the integral term acts on the speed deviation even when the target rotation speed is different from 0, the deceleration will not be constant because the actual rotation speed will be made to follow the target rotation speed in a short time. In this case, the deceleration will not be constant, which leads to a deterioration in the operational feel of the industrial vehicle 10. In contrast, when braking the industrial vehicle 10, control is performed so that the integral term acts on the speed deviation when the target rotation speed is 0, thereby suppressing a deterioration in the operational feel of the industrial vehicle 10. In addition, by performing a process of updating the maximum output ratio when the target rotation speed is a value different from 0, the integral gain can be set before the integral term acts on the speed deviation.

[0063] (6) The integral gain calculation unit 46 can set an integral gain according to the weight of the load L. Even if a load sensor for measuring the weight of the load L is not provided, the integral gain can be set according to the weight of the load L, which reduces manufacturing costs compared to the case where a load sensor is provided.

[0064] [Example of change] The embodiment can be modified as follows: The embodiment and the following modified examples can be combined with each other to the extent that there is no technical contradiction.

[0065] ○ An integral gain may be associated with each of a plurality of ranges into which the maximum output ratio can be divided. For example, the range into which the maximum output ratio can be divided is 45% to 98%. In this case, the range of 45% to 98% is divided according to the load, such as a first range corresponding to 0 [kg], a second range corresponding to 500 [kg], a third range corresponding to 1000 [kg], and so on. Then, an integral gain suitable for each range is associated with each range. For example, an integral gain suitable for the industrial vehicle 10 in an unloaded state is associated with the first range. An integral gain suitable for the industrial vehicle 10 in a state in which it is transporting a load L of 500 [kg] is associated with the second range. An integral gain suitable for the industrial vehicle 10 in a state in which it is transporting a load L of 1000 [kg] is associated with the third range.

[0066] The control device 30 calculates the maximum output rate by the maximum output rate calculation control. Then, the control device 30 sets an integral gain associated with the category to which the maximum output rate belongs. For example, when the maximum output rate belongs to the above-mentioned first category, the control device 30 sets an integral gain associated with the first category.

[0067] The control device 30 may perform proportional-integral-derivative control as feedback control. In step S3, the integral gain calculation unit 46 may determine whether the absolute value of the actual rotation speed is equal to or lower than the base rotation speed. In other words, the integral gain calculation unit 46 does not need to determine whether the target rotation speed is a value different from 0.

[0068] The control device 30 may set the output rate when the rotation speed of the traveling motor 24 drops from a state where it is higher than the base rotation speed to a state where it is equal to or lower than the base rotation speed, as the maximum output rate when the rotation speed of the traveling motor 24 is equal to or lower than the base rotation speed.

[0069] The industrial vehicle 10 may be equipped with a mechanical brake. The industrial vehicle 10 may be a towing tractor that tows and transports a load L. [Explanation of symbols]

[0070] L...load, 10...industrial vehicle, 22...inverter, 24...travel motor, 30...control device.

Claims

1. An industrial vehicle capable of transporting loads, A travel motor; An inverter that drives the traveling motor; A control device for controlling the inverter, The control device includes: Calculating a deviation between the rotation speed of the traveling motor and a target rotation speed; Calculating an output ratio based on the deviation, a proportional gain, and an integral gain; calculating a torque current command value by multiplying the output ratio by a torque current curve; converting the torque current command value into a command value for the inverter to control the traveling motor so that the rotation speed of the traveling motor follows the target rotation speed; The integral gain is set based on a maximum value of the output rate when the rotation speed of the travel motor is equal to or lower than a base rotation speed during braking of the industrial vehicle.

2. The control device includes: The maximum value calculated while the rotation speed of the traveling motor is maintained at or below the base rotation speed is held, 2. The industrial vehicle according to claim 1, wherein when the output ratio is calculated while the rotation speed of the traveling motor is maintained at or below the base rotation speed, if the calculated output ratio is greater than the held maximum value, the calculated output ratio is held as a new maximum value.

3. The control device includes: When the maximum value is equal to or less than a no-load output ratio reference value, a no-load integral gain is set as the integral gain; When the maximum value is equal to or greater than a maximum load output ratio reference value, a maximum load integral gain is set as the integral gain; when the maximum value is greater than the no-load output ratio reference value and less than the maximum load output ratio reference value, a linearly interpolated integral gain obtained by linearly interpolating between the no-load integral gain and the maximum load integral gain is set as the integral gain; the no-load output ratio reference value is set such that the maximum value is equal to or less than the no-load output ratio reference value when the industrial vehicle is not transporting the load, 3. The industrial vehicle according to claim 1, wherein the maximum load output ratio standard value is set so that the maximum value is equal to or greater than the maximum load output ratio standard value when the industrial vehicle is transporting a load of the maximum weight that the industrial vehicle can transport.

4. a range in which the maximum value can be taken is divided into a plurality of ranges, and the integral gain is associated with each of the ranges; 3. The industrial vehicle according to claim 1, wherein the control device sets the integral gain in association with a category to which the maximum value belongs.

5. 3. The industrial vehicle according to claim 1, further comprising only the travel motor as a braking device.

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