JP2011046499A - Cargo handling control device of forklift - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce an operational burden of an operator by reducing a shock in stopping by preventing an abrupt drop of a lift. <P>SOLUTION: This forklift has a fork 33 for mounting a cargo, a hydraulic cylinder 23 for driving the fork, and a hydraulic pump 27 for driving the hydraulic cylinder, and regenerates the potential energy of the cargo to a power source of a power converter 25 when driving the mounted cargo in the lowering direction. A controller 100 for controlling the converter has a target speed arithmetic operation part for limiting a lowering speed so that the sum of an arithmetically operated load and an inertia force becomes a tractive force or smaller determined by the allowable torque of a motor for driving the hydraulic pump by arithmetically operating the load of the cargo and the inertia force of the cargo. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a cargo handling control device for a forklift, and more particularly to a cargo handling control device for a forklift that takes into account the inertial force of the cargo.

  A cargo handling device such as a forklift is composed of a hydraulic circuit as shown in FIG. FIG. 17 is a view showing the appearance of the forklift. In these drawings, the operator can drive the forklift by stepping on the accelerator pedal 36 to drive the wheels 42. Further, by operating the lift lever 21, the fork 33 can be raised or lowered by extending or contracting the hydraulic cylinder 23.

  For example, when the lift lever 1 is operated to the lift-up side (right side in the figure), the control valve 2 moves to the side where the hydraulic pump 3 communicates with the hydraulic cylinder 4, and the cargo handling electric motor 5 drives the hydraulic pump 3. The hydraulic pump 3 supplies oil in the oil tank 7 to the hydraulic cylinder 4 via the check valve 6 and the control valve 2. Here, a relief valve 8 is provided between the hydraulic pump 3 and the check valve 6 so that the discharge pressure of the hydraulic pump 3 does not exceed the pressure resistance of the piping.

  The hydraulic cylinder 4 is extended by the supplied oil, lifts the movable pulley 9, and raises the fork 11 through the chain 10 hung on the movable pulley 9. At this time, the cargo handling electric motor 5 is driven at a substantially constant output, and the operator can adjust the opening degree of the control valve 2 and control the lift-up speed by adjusting the inclination of the lift lever 1. . When the lift lever 1 is operated to the lift-down side (left side in the figure), the control valve 2 moves to the side where the oil tank 7 and the hydraulic cylinder 4 are communicated. The hydraulic cylinder 4 is compressed by the weight of the fork 11 and the load of a load (not shown), and returns the oil to the oil tank 7 via the control valve 2 and the check valve 12. At this time, the electric motor 5 for cargo handling is stopped, and the operator can adjust the opening degree of the control valve 2 and adjust the lift-down speed by adjusting the inclination of the lift lever 1.

  As described above, in the conventional cargo handling device, the pressure loss is generated by adjusting the opening degree of the control valve 2, and the lift speed is adjusted. Therefore, when the control valve 2 is closed during lift lifting, the oil inflow and outflow to the cylinder 4 are blocked, and the lift stops suddenly. For this reason, a shock may occur in the fork 11, the luggage and the entire vehicle. Further, since the lift speed is adjusted by generating a pressure loss (energy loss), that is, when the lift is down, the potential energy of the fork 11 and the load is not regenerated, so there is room for energy efficiency improvement. .

  With regard to such a problem, Patent Document 1 discloses a forklift loading / unloading device including a loading / unloading motor stopping unit that stops a loading / unloading motor before the control valve is closed in order to reduce a shock when the loading / unloading operation is stopped. Yes. Further, Patent Document 2 discloses a forklift provided with a control unit that reversely controls a hydraulic motor in order to accurately control the lift-down speed and regenerate and effectively use the potential energy at the time of lift-down.

JP-A-10-310395 JP 2003-252586 A JP 2007-120716 A

  However, the cargo handling control device disclosed in Patent Document 1 does not necessarily take into account the handling motor stop means at the time of lift-down, and may give a shock to the fork, luggage and the entire vehicle when stopping the lift from the lift-down. is there.

  Further, the control means disclosed in Patent Document 2 does not necessarily take into account the output limit of the electric motor for cargo handling, and there is a possibility that the lift-down speed is set regardless of the load of the load. For this reason, when the lift-down speed is too high, the load due to the load and the load due to inertial force cannot be supported by the electric motor for cargo handling, and there is a problem in controlling the lift-down speed.

  Also, when the vehicle speed is decelerated simultaneously with the lift-down during traveling, the regenerative power is generated from the traveling electric motor in addition to the regenerative power from the cargo handling electric motor, so the lift-down is performed while the vehicle is stopped. The voltage of the power storage device becomes higher than that, and the internal voltage of the driving device for the electric motor for cargo handling, for example, an inverter or a chopper becomes higher.

  As described above, when the lift-down speed increases, the internal voltage may exceed the withstand voltage of the driving device for the cargo handling electric motor. In such a case, the torque of the cargo handling electric motor may decrease. Problems arise in controlling the lift-down speed. For this reason, the operator needs to carefully operate the lift lever so that the lift-down speed does not become too high.

  The present invention has been made in view of such problems, and in a cargo handling control device that regenerates potential energy at the time of lift-down, the sudden drop of the lift is prevented and the shock at the time of stop is reduced. An object of the present invention is to provide a cargo handling control device capable of reducing the operation burden.

  In order to solve the above problems, the present invention employs the following means.

  A fork for loading a load, a hydraulic cylinder for driving the fork, and a hydraulic pump for driving the hydraulic cylinder, wherein the hydraulic pump is driven through a power converter and the loaded load is driven in a downward direction. In a forklift that regenerates the potential energy of the power converter to the power source of the power converter, the controller that controls the converter calculates the load of the load and the inertial force of the load, and the sum of the calculated load and inertial force is the hydraulic pressure A target speed calculation unit is provided for limiting the lowering speed so that the traction force is less than or equal to the traction force determined by the allowable torque of the motor driving the pump.

  Since the present invention has the above-described configuration, it is possible to prevent a sudden drop of the lift, reduce a shock at the time of stop, and reduce an operation burden on the operator.

It is a figure explaining the cargo handling control apparatus of the forklift concerning a 1st embodiment. It is a figure explaining the detail of a controller. It is a figure explaining the structure of a cargo handling motor control part. It is a figure which shows the example of the target speed calculation performed in a target speed calculating part. It is a figure explaining the example of the method of calculating lift speed limit value _{vl_lmt} . It is a figure explaining the example of the torque command calculation performed by the torque command value calculating part shown in FIG. It is a figure explaining the example of valve control performed by a valve control part. It is a figure which shows the operation example of the conventional cargo handling control apparatus in the state which loaded the load. It is a figure which shows the operation example of the cargo handling control apparatus of this embodiment in the state which loaded the load. It is a figure explaining the cargo handling control apparatus of the forklift truck concerning 2nd Embodiment. It is a figure which shows the control structure of a controller. It is a figure explaining the example of the traveling control performed in a traveling control part. It is a figure which shows the structural example of a cargo handling motor control part. It is a figure explaining the example of the control which the target speed calculating part shown in FIG. 13 performs. It is a figure explaining the example of traveling control. It is a figure explaining the conventional hydraulic circuit used for a cargo handling apparatus. It is a figure which shows the external appearance of a forklift.

[Embodiment 1]
FIG. 1 is a diagram for explaining a forklift cargo handling control apparatus according to a first embodiment. The controller 100 receives a lever signal corresponding to the operation amount of the lift lever 21 from a potentiometer (not shown) attached to the lift lever 21, and receives a pressure sensor signal corresponding to the pressure of the hydraulic cylinder 23 from the pressure sensor 22. The cargo handling motor rotation speed is received from an encoder (not shown) attached to the cargo handling electric motor 24.
The controller 100 calculates a cargo handling motor torque command and a valve opening signal according to the received lever signal, pressure sensor signal, and cargo handling motor rotation speed, and shows the interior of the valve 26 and the cargo handling motor driver (not shown) attached to the inverter 25. Not supplied to each valve drive circuit. A method for calculating a cargo handling motor torque command and a valve opening signal performed by the controller 100 will be described later.

  The inverter 25 drives the cargo handling electric motor 24 in accordance with the cargo handling motor torque command. The valve 26 is a lift position holding means, and is a normally closed on / off valve in order to reduce pressure loss. The valve 26 opens when the valve open signal is ON, and closes when the valve open signal is OFF.

  When the operator operates the lift lever 21 to the lift-up side (right side in the figure), the controller 100 opens the valve and connects the hydraulic pump 27 and the hydraulic cylinder 23. The inverter 25 drives the cargo handling electric motor 24 using the electric power of the battery 28, and drives the hydraulic pump 27 directly connected to the cargo handling electric motor 24. The hydraulic pump 27 supplies the oil in the oil tank 29 to the hydraulic cylinder 23 via the valve 26.

  Here, a relief valve 30 is provided between the hydraulic pump 27 and the valve 26 so that the discharge pressure of the hydraulic pump does not exceed the pressure resistance of the piping. The hydraulic cylinder 23 is extended by the supplied oil, lifts the movable pulley 31, and raises the fork 33 via the chain 32 hung on the movable pulley 31. At this time, the controller 100 controls the speed of the cargo handling electric motor 24 according to the inclination of the lift lever 21 to adjust the lift-up speed.

  On the other hand, when the operator operates the lift lever 21 to the lift-down side (left side in the figure), the controller 100 opens the valve 26 and connects the hydraulic pump 27 and the hydraulic cylinder 23. The hydraulic cylinder 23 is compressed by the weight of the fork 33 and the load of a load (not shown), and causes the oil to flow backward to the hydraulic pump 27 via the valve 26. The hydraulic pump 27 is reversely driven by oil, and reversely drives the cargo handling electric motor 24. At this time, the controller 100 controls the rotational speed of the hydraulic pump 27 and adjusts the lift-down speed by causing the electric motor 24 for cargo handling to generate torque in the direction opposite to the rotational direction. For this reason, regenerative power is supplied from the electric motor 24 for cargo handling to the battery 28 via the inverter 25. That is, the operator can control the lift-up speed and the lift-down speed by adjusting the inclination of the lift lever 21.

  FIG. 2 is a diagram for explaining the details of the controller 100. The controller 100 includes an estimation unit 110, a cargo handling motor control unit 120, and a valve control unit 130, and outputs a cargo handling motor torque command and a valve opening signal in accordance with a lever signal or the like. Hereinafter, the estimation unit 110, the cargo handling motor control unit 120, and the valve control unit 130 will be described.

The estimating unit 110, a load estimation value m _l of the following (1) based on the pressure sensor signal, based on the inverter DC current I _ml of (2) T _ml handling motor torque estimate from equation handling motor The lift speed estimated value v _l is calculated from the equation (3) based on several _nml .

Here, p _c is the hydraulic cylinder pressure calculated based on the pressure sensor signal, a _c is the effective sectional area of the hydraulic cylinder 23, g is the gravitational acceleration, m ₀ is the mass of the fork, _mi is the piston of the hydraulic cylinder 23 and This is the total mass of the movable pulley 31 that moves integrally with the piston and the inner frame of the mast (not shown). K _ml is a torque constant of the cargo handling motor and is obtained in advance by experiments or the like. Further, D _p is the displacement per unit angle of the hydraulic pump.

  FIG. 3 is a diagram illustrating the configuration of the cargo handling motor control unit 120. The cargo handling motor control unit 120 includes a target speed calculation unit 121, a target torque calculation unit 122, and a torque command calculation unit 123, and outputs a cargo handling motor torque command based on a lever signal or the like. Details of the control performed by the target speed calculation unit 121 and the torque command calculation unit 123 will be described later.

The target torque calculation unit 122 performs known feedback control such as PID control based on the lift speed target value v _{l_t} and the lift speed estimated value v _l so that the lift speed estimated value v _l approaches the lift speed target value v _{l_t.} The cargo handling motor torque target value T _{ml_t0} is calculated.

FIG. 4 is a diagram illustrating an example of target speed calculation performed by the target speed calculation unit 121. Step S141 before correction from the following equation based on a lever signal s _l in calculating the lift speed target value _v l_t0.

Here, k _ll when the lever signal s _l a proportional constant is maximum, the pre-correction lift speed target value v _{L_t0} is preset so that the maximum lift speed. Positive when the lever signal s _l tilting the lift lever 21 to lift-up side, since the negative tilting the lift lever 21 to the lift-down side, the pre-correction lift speed target value v _{L_t0} positive when lifted up, negative when lifted down It becomes.

_If the sign of the lift speed target value v _{l_t0} before correction is 0 or more (lift up) in step S142, the process proceeds to step S143, and if it is less than 0 (lift down), the process proceeds to step S144. In step S143, the lift speed target value v _{l_t0} before correction is set as the lift speed target value v _{l_t} as it is, and the target speed calculation is terminated. Step S144 based on load estimation value m _l In calculating the inertial force F _i from the following equation.

Here, a _{s_t} is a stop deceleration target value, and is set in advance as a deceleration at which the lift operation can be stopped safely, for example, a _{s_t} = 10.0.

Then load estimation value m _l in step S145, calculates the estimated load torque T _{Lp_ary} from the following equation based on the inertial force F _i.

Here, v _{l_ary} is an array of lift speeds, for example, [0, −0.1,..., −0.5], and the predicted load torque T _{lp_ary} is also obtained as an array corresponding to the lift speed array v _{l_ary} . However, _cf is a proportional constant of the friction force of the hydraulic cylinder 23 generated according to the lift speed and the resistance force due to the pressure loss of the valve 26, and is set to an appropriate value in advance.

In step S146, the lift speed limit value _{vl_lmt} is calculated based on the predicted load torque _{Tlp_ary} . Details of the calculation method of the lift speed limit value v _{l_lmt} will be described later. In step S147, the uncorrected lift speed target value v _{l_t0} and the lift speed limit value v _{l_lmt} are compared, and the smaller absolute value is set as the lift speed target value v _{l_t} to complete the target speed calculation.

FIG. 5A is a diagram illustrating an example of a method for calculating the lift speed limit value v _{l_lmt} . In FIG. 5A, the horizontal axis represents the lift speed (absolute value of the lift speed), and the vertical axis represents the motor torque. Here, the motor torque allowable value T _{mla_ary} indicates the output limit of the motor torque corresponding to the lift speed array v _{l_ary} . That is, on the right side of the figure (the side where the lift speed increases), with the stop limit lift speed v _{l_lmt0} corresponding to the intersection (torque intersection in the figure) of the motor torque allowable value T _{mla_ary} and the predicted load torque T _{lp_ary} as The predicted load torque T _{lp_ary} is larger than the motor torque allowable value T _{mla_ary} and the motor torque is insufficient. For this reason, it is indicated that the lift cannot be stopped at the preset stop deceleration target value a _{s_t} .

Therefore, in order to make it possible to stop the lift at a _preset stop deceleration target value a _{s_t} , the lift speed limit value v _{l_lmt} is set to the left side of the figure (the side where the lift speed becomes smaller) from the stop limit lift speed v _{l_lmt0} . . Here, the value obtained by dividing the stop limit lift speed v _{l_lmt0} by the safety factor (for example, 1.2) may be _used as the lift speed limit value v _{l_lmt.} However, if the safety factor is increased too much, the lift speed can be suppressed more than necessary, and the work efficiency May get worse. For this reason, it is desirable to set the lift speed limit value v _{l_lmt} in the vicinity of the stop limit lift speed v _{l_lmt0} .

Although the present embodiment has been described as calculating the lift speed limit value v _{L_lmt} the estimated load torque T _{Lp_ary} group, calculates the lift speed limit value v _{L_lmt} from load estimation value m _l using a map set in advance It may be simplified as follows.

  Here, the correspondence relationship between the lever signal and the lift speed target value will be described with reference to FIG. FIG. 5B shows the lever signal on the horizontal axis and the lift speed target value on the vertical axis. If the lever signal is positive, the lift speed target value is also positive (lift lift side), and if the lever signal is negative. The lift speed target value is also negative (lift lowering side). When no load is loaded, the lift speed target value is set to a value corresponding to the lever signals from A1 to B1 on the solid line L.

  On the other hand, when a load is loaded, a lift speed limit value calculated based on the estimated load value is set, and when the lever signal decreases (increases in the negative direction), the lift speed target value is changed from point O to B2. The point decreases to the point as in the case where no load is loaded, but moves from B2 point to B3 and does not decrease to B1 point. Therefore, since the lower limit value of the lift speed target value is set according to the mass of the load, the lift speed when the lift is lowered can be reliably controlled. Also, up to point B2, the same lift speed as when no load is loaded according to the lever operation can be obtained, so that it is not necessary to largely tilt the lever according to the mass of the load, and the operation burden on the operator can be reduced.

FIG. 6 is a diagram for explaining an example of the torque command calculation performed by the torque command value calculation unit 123 shown in FIG. At step S151, the lever signal s _l of absolute value the threshold s _{L_min} more or valve opening signal s _v preset is determined whether ON, the lever signal s threshold absolute value preset of _l s _{L_min} If the valve opening signal _sv is ON, or if the operator intends to perform a lift operation or the valve 26 is open, it is determined that it is necessary to generate torque in the electric motor 24 for cargo handling. Then, the process proceeds to step S152. Otherwise, it is determined that the cargo handling electric motor 24 may be stopped, and the process proceeds to step S153.

In step S152, the cargo handling motor torque target value _{Tml_t0} is _{used as it} is as the cargo handling motor torque command _{Tml_t} , and the torque command calculation is terminated. In step S153, in order to stop the electric motor for cargo handling, the cargo handling motor torque command T _{ml_t} is gradually decreased from the previous value (value before one control cycle) to zero.

FIG. 7 is a diagram illustrating an example of valve control performed by the valve control unit 130. Previous value of the valve opening signal s _v In step S161, it is determined whether an ON, the step S163 if the previous value is ON, the previous value proceeds to step S162 if turned OFF. In step S162, it determines whether the absolute value of the lever signal s _l is the threshold value s _{L_min} than a preset, if more than a threshold value, it is determined that there is intended to lift operation to the operator proceeds to step S163 Otherwise, the process proceeds to step S166.

In step S163, if the threshold value T _{Ml_min} than the threshold n _{Ml_max} less and cargo handling motor torque estimate T _ml absolute value of the load handling motor rotational speed n _ml is previously set preset to step S164, and otherwise the step The process proceeds to S166.

Here, it is determined that the larger the absolute value of the load handling motor rotational speed n _ml cargo handling electric motor are overspeed, also, it is determined that not carry the weight of a load smaller motor torque estimate T _ml Step In S166, the valve 26 is closed. Therefore, according to the stop limit lift speed v _{L_lmt0} and load estimation value m _l shown in FIG. 5, it may be set to be larger threshold n _{Ml_max} larger the absolute value of the stop limit lift speed v _{L_lmt0,} threshold T _{Ml_min} larger the load estimation value m _l may be set so as also increased.

It is determined whether the absolute value of the threshold n _{Ml_min} more or lever signal s _l absolute value of the load handling motor rotational speed n _ml previously set is the threshold value s _{L_min} than the preset in step S164, if the above threshold In step S165, otherwise, it is determined that the cargo handling electric motor is stopped, and the process proceeds to step S166. Here, it is needless to say that the threshold value n _{Ml_min} a value smaller than the threshold value _n ml_max. In step S165, in order to open the valve 26, the valve opening signal _sv is turned ON. In step S166, in order to close the valve 26, the valve opening signal _sv is turned OFF.

  8 and 9 are diagrams showing examples of the lift operation. All show time-series data of a valve opening signal, a cargo handling motor torque, a lift speed, and a lift head when an operation of lift up → stop → lift down → stop is performed. Further, in lift-down and lift-up, the operator's lever operation amount is full lever operation.

  FIG. 8 is a diagram illustrating an operation example of a conventional cargo handling control apparatus in a state where a load is loaded. Due to lift-up at time 0 seconds, when the lever signal is turned on, the valve opening signal is also turned on and the motor torque is increased. At this time, the output limit value is smaller than the cargo handling motor torque command, and the actual motor torque does not reach the cargo handling motor torque command. For this reason, although the deviation remains between the lift speed target value and the actual lift speed, the lift can be raised to the target ascending position only by suppressing the actual lift speed.

  On the other hand, in the liftdown from the time 7.5 seconds, when the cargo handling motor torque command exceeds the output limit value and the actual motor torque does not reach the cargo handling motor torque command, the actual lift speed is faster than the lift speed target value ( (Absolute value is large). If the actual lift speed increases, the rotation speed of the cargo handling electric motor also increases.As a result, the output limit value is further reduced, resulting in an increase in the actual lift speed, which makes it impossible to control the lift speed and causes a sudden drop in the lift. Yes.

  After that, even if the lever signal is set to 0 when the target lowering position is reached, the lift cannot be stopped by the cargo handling electric motor. Therefore, the lift is stopped by turning off the valve open signal and closing the valve. A large vibration is generated in the lift speed by stopping.

  FIG. 9 is a diagram illustrating an operation example of the cargo handling control device of the present embodiment in a state where a load is placed. The operation from time 0 seconds until reaching the target lift-up stop position is the same as the operation example of the conventional cargo handling control device shown in FIG.

  On the other hand, in the lift-down from time 7.5 seconds, since it is set smaller than the lift speed target value (b in the figure) when no load is placed, the actual lift speed is suppressed and the output limit is reduced. Thus, there is no shortage of torque. In addition, the lift speed target value is set so that insufficient torque does not occur in consideration of the inertia force generated when the lift is stopped, so the lift can be stopped by the electric motor for cargo handling, and the lift speed is adjusted when the lift stops. Large vibrations do not occur.

  As described above, according to the present embodiment, the lowering speed of the lift is limited according to the load applied to the lift so that the lowering speed of the lift is smaller as the load is larger. For this reason, when the potential energy at the time of lift-down is regenerated, a sudden drop of the lift can be prevented, and the operation burden on the operator can be reduced.

  Moreover, the valve | bulb 26 as a lift position holding means which can hold | maintain the height of a lift is provided. When stopping, first, the lift is stopped by bringing the rotational speed of the electric motor for cargo handling close to 0. When the rotational speed of the electric motor for cargo handling 24 becomes almost zero, the lift position holding means is operated to increase the lift height. Keep it. Thereby, the shock at the time of a lift stop can be reduced.

[Embodiment 2]
FIG. 10 is a view for explaining a forklift cargo handling control apparatus according to the second embodiment. In addition to the signals received by the controller 100 described in the first embodiment, the controller 200 is attached to the shift signal from the shift switch 35, an accelerator signal from a potentiometer (not shown) attached to the accelerator pedal 36, and the brake pedal 37. A brake signal from a potentiometer (not shown) and a traveling motor rotation speed signal from an encoder (not shown) attached to the traveling electric motor 38 are received.

  FIG. 11 is a diagram illustrating a control configuration of the controller 200. The controller 200 includes a travel control unit 210, a cargo handling motor control unit 220, an estimation unit 110, and a valve control unit 130. The estimation unit 110 and the valve control unit 130 are the same as those in the first embodiment.

  In addition to the signal transmitted by the controller 100 described in the first embodiment, a shift motor, an accelerator signal, a brake signal, and a travel motor torque command signal calculated according to the travel motor rotation speed are attached to the inverter 39. Not sent to the motor driver for running. A method for calculating a cargo handling motor torque command, a valve opening signal, and a traveling motor torque command performed by the controller 200 will be described later.

  The lift operation of the cargo handling control device of this embodiment is the same as that of the first embodiment. When the operator steps on the accelerator pedal 36, the controller 200 causes the traveling electric motor 38 to generate torque corresponding to the amount of depression of the accelerator pedal 36. The torque generated by the traveling electric motor 38 is decelerated by the speed reducer 40 and is transmitted to the left and right wheels 42a and 42b via the differential mechanism 41 to drive the wheels 42a and 42b.

  At this time, if the operator operates the shift switch 35 to the forward side (the left side in the figure), the traveling electric motor 38 generates torque in the direction in which the wheels 42a and 42b rotate forward (the direction in which the vehicle advances), When operated to the reverse side (right side in the figure), the traveling electric motor 38 generates torque in the direction in which the wheels 42a and 42b reverse (the direction in which the vehicle moves backward). Further, when the operator operates the shift switch 35 to the neutral position, the traveling electric motor 38 does not generate torque.

  On the other hand, when the operator steps on the brake pedal 37, the controller 200 causes the traveling electric motor 38 to generate torque corresponding to the amount of depression of the brake pedal 37. The brake pedal 37 is mechanically connected to a well-known friction brake (not shown), and the wheels 42a and 42b have a torque from the traveling electric motor 38 and a friction torque from the friction brake according to the depression amount of the brake pedal 37. Will be added.

FIG. 12 is a diagram illustrating an example of travel control performed by the travel control unit 210. Accelerator signal using a map set in advance in step S231 s _a, calculates the target driving torque T _{Mrd_t} from the traveling motor speed n _mr. In step S232, the target braking torque T _{mrb_t} is calculated from the brake signal s _b and the traveling motor rotational speed n _mr using a preset map. Here, it is desirable to set the map so that the target driving torque T _{mrd_t} and the target braking torque T _{mrb_t} become larger as the depression amounts of the accelerator pedal 36 and the brake pedal 37 are larger. In step S233, a travel motor torque command T _{mr_t} is calculated from the following equation based on the target drive torque T _{mrd_t} , the target drive torque T _{mrd_t} , the shift signal s _s and the travel motor rotation speed n _mr .

However, sign is a sign function that returns the sign of the number in parentheses. In step S234, the travel regeneration amount P _rin is calculated from the following equation based on the travel motor torque command T _{mr — t} and the travel motor rotation speed n _mr .

  FIG. 13 is a diagram illustrating a configuration example of the cargo handling motor control unit 220. The cargo handling motor control unit 220 includes a target speed calculation unit 221, a target torque calculation unit 122, and a torque command calculation unit 123. Here, the target torque calculator 122 and the torque command calculator 123 are the same as those in the first embodiment.

FIG. 14 is a diagram illustrating an example of control performed by the target speed calculation unit 221 illustrated in FIG. Since step S241 is added between step S145 and step S146 except that step S241 is added, only the parts different from the first embodiment will be described here. In step S241, the motor torque allowable value T _{mla_ary} is calculated using the following equation based on the travel regeneration amount p _rin .

Here, p _bain is the allowable regenerative power of the battery, and is set in advance in consideration of the battery life, the withstand voltage of the inverters 25 and 39, and the like. Further, _{nml_ary} is an array of the rotation speeds of the electric motor for cargo handling corresponding to the array of lift speeds v _{l_ary} of the first embodiment. That is, in the target speed calculating part of the present embodiment, the traveling amount of regeneration p _rin and variable motor torque tolerance value T _{Mla_ary} depending on, traveling regeneration amount p _rin is too large lift speed target value so as to reduce the lift-down speed v _{Calculate l_t} .

  As described above, the cargo handling control device according to the present embodiment restricts the lowering speed of the lift so that the lowering speed of the lift decreases as the traveling speed of the vehicle (the absolute value of the traveling speed) increases. While regenerating the potential energy, a sudden descent of the lift can be prevented, and the operation burden on the operator can be reduced.

In this embodiment, the travel regeneration amount P _rin is calculated using the equation (8). However, the travel regeneration amount P _rin is calculated from a map set in advance based on the travel motor torque command T _{mr_t} and the travel motor rotation speed n _{mr. Alternatively} , the travel regeneration amount P _rin may be calculated using the following simplified formula.

Here, K _prin is a traveling regeneration proportional constant, and is set in advance so that the traveling regeneration amount P _rin calculated using Equation (10) is larger than the traveling regeneration amount P _rin calculated using Equation (8). deep. Here, by calculating the travel regeneration amount P _rin using the equation (10), when the travel electric motor 38 rotates, that is, when the vehicle travels, the travel regeneration amount according to the vehicle speed. Since P _rin is calculated and the lift speed limit value v _{l_lmt} is set higher (absolute value is smaller) in advance than when the vehicle is stopped, it is possible to prevent the lift down speed from rapidly changing according to the deceleration of the vehicle. .

In the present embodiment, the control illustrated in FIG. 12 is used as an example of the travel control performed by the travel control unit 210, but the travel control illustrated in FIG. 15 can be used. Steps S231 to S233 are the same as the travel control shown in FIG. Step S331 is a traveling regeneration prediction means of the present invention, when the accelerator signal s _a is smaller than the threshold s _{a_min} set in advance, or the product of the travel motor rotation speed n _mr and the shift signal s _s is negative (advanced wheel If it is rotating in the opposite direction), it is determined that there is a possibility of traveling regeneration, and the process proceeds to step S332. Otherwise, the process proceeds to step S333. In step S332, the travel regeneration amount P _rin is calculated using the above-described equation (10). In step S333, the traveling regeneration amount P _{rin is set} to zero.

  Although Embodiment 1 and Embodiment 2 demonstrated the cargo handling apparatus as a hydraulic type using a hydraulic cylinder and a hydraulic pump, this invention is not limited to this, The cargo handling apparatus is described in patent document 3. Such a rotation / linear motion conversion device may be used. When using a rotation / linear motion conversion device, a normal ON type friction brake is applied to the electric motor for cargo handling as the lift position holding means, the friction brake is released during the lift operation, and the friction brake is engaged when the lift is stopped. The valve 26 described in the first and second embodiments can be substituted.

  As described above, according to the embodiment of the present invention, the lowering speed of the lift is limited according to the load applied to the lift so that the lowering speed of the lift is smaller as the load is larger. Also, there is a lift position holding means for holding the lift position. First, the lift is stopped by bringing the rotation speed of the electric motor for cargo handling close to zero, and the lift position is maintained when the rotation speed of the electric motor for cargo handling becomes almost zero. Hold the lift height by means. In addition, the vehicle is provided with a traveling control means for controlling the traveling speed of the vehicle by powering and regeneratively braking the traveling electric motor. Restrict. Thereby, while regenerating the potential energy at the time of lift-down, a sudden drop of the lift can be prevented, and the operation burden on the operator can be reduced.

DESCRIPTION OF SYMBOLS 1 Lift lever 2 Control valve 3 Hydraulic pump 4 Hydraulic cylinder 5 Electric motor for cargo handling 6 Reverse support valve 7 Oil tank 8 Relief valve 9 Dynamic pulley 10 Lift chain 11 Fork 12 Check valve 21 Lift lever 22 Pressure sensor 23 Hydraulic cylinder 24 For cargo handling Electric motor 25 Inverter 26 Valve 27 Hydraulic pump 28 Battery 29 Oil tank 30 Relief valve 31 Moving pulley 32 Lift chain 33 Fork 35 Shift switch 36 Accelerator pedal 37 Brake pedal 38 Electric motor for traveling 39 Inverter 40 Reducer 41 Differential mechanism 42 Wheel 100, 200 controller

Claims (6)

A fork for loading a load, a hydraulic cylinder for driving the fork, and a hydraulic pump for driving the hydraulic cylinder, wherein the hydraulic pump is driven through a power converter and the loaded load is driven in a downward direction. In the forklift that regenerates the potential energy of the power converter power source,
The controller that controls the converter calculates the load of the load and the inertial force of the load, and the sum of the calculated load and the inertial force is equal to or less than the traction force determined by the allowable torque of the motor that drives the hydraulic pump. A forklift characterized by comprising a target speed calculator for limiting the descending speed. The forklift according to claim 1,
It has a lift lever that controls the ascending or descending speed of the fork according to its inclination,
The target value calculation unit is configured to limit the descending speed of the fork to the limit value regardless of the lift lever position after the descending speed of the fork with respect to the lift lever position reaches the limit value of the descending speed. forklift. The forklift according to claim 1,
A forklift characterized in that a control valve is provided in a pipe line connecting the hydraulic pump and the hydraulic cylinder, and the control valve is closed to hold the position of the fork when rotation of the hydraulic pump is stopped. The forklift according to claim 1,
A forklift comprising a traveling speed sensor for detecting a traveling speed of the forklift, wherein the lowering speed of the fork is set to be smaller as the traveling speed is higher. The forklift according to claim 1,
When the amount of depression of the accelerator petal is less than the predetermined value, or the combination of the traveling motor rotation direction and the shift lever position signal indicates that the wheel of the forklift is rotating in the direction opposite to the traveling direction, the fork A forklift characterized in that the lowering speed of the vehicle is set to be small. A fork for loading the load, a hydraulic cylinder for driving the fork, and a hydraulic pump for driving the fork, the position of the load when the hydraulic pump is driven by an inverter and the loaded load is driven in the downward direction In the control method of a forklift that regenerates energy to the power supply of the inverter,
Calculates the load of the load and the inertial force that occurs when the fork carrying the load stops descending, and limits the descending speed so that the sum of the calculated load and inertial force is less than the set value. A method for controlling a forklift characterized by mitigating an impact on the forklift.