FR2801847A1 - LIFT TRUCK CONTROL APPARATUS - Google Patents

Abstract

In this control apparatus, a CPU (27) derives the speed and acceleration of the main forklift chassis from the number of engine revolutions detected by a rotation detection part (22). When the main chassis stop is recognized, a directional lever is established in a neutral position and the accelerator pedal deactivation state is detected by an acceleration pedal detection part to maintain the chassis speed main at a given low speed in accordance with the speed and acceleration of the main chassis when it descends along a slope due to a failure to apply the parking brake, the output command value of a induction motor which uses a differentiation and proportionality control is calculated and on this basis, a PWM pulse output portion (28) is controlled to control the number of revolutions of the induction motor.

Description

BACKGROUND OF THE INVENTION

  1. Field of the Invention The present invention relates to a forklift control apparatus which converts the continuous output power of a battery transported on board the main chassis of a forklift truck to an alternating power using an inverter, which applies alternating power to an induction motor to power it and which controls the induction motor using a control part in order to thus implement normal motor operation or operation

  forklift regenerator.

2. Description of the prior art

  Normally, to run a forklift of the battery activated type, for example as shown in Figure 12, power can be applied to a DC motor 3 to run the forklift using a battery 2 which is transported to edge of main frame 1 of the forklift. During this rolling operation, by activating a directional lever (or a directional switch) 4 which makes it possible to switch and establish a transmission means (not shown) for transmitting the driving power of the motor 3 to the wheels of the lift truck according to either the forward operating state, or the reverse operating state, or the neutral position state, the transmission means is switched to either the forward operating state, or the reverse operating state, or the neutral state in which the lift truck is parked, and the main lift truck chassis 1 is steered by activating a lever 5. Thus, in FIG. 12, respectively, a reference index 6 designates a mast which is arranged in the front part of the main forklift chassis 1, a reference index 7 designates a lifting console which is mounted on the mast 6, a reference index 8 designates two forks which are respectively mounted on the console lifting 7 and an index of

  reference 9 designates an accelerator pedal.

  First, we will describe a problem in the case of

  maintenance of the lift truck in the stop condition on a slope.

  In a DC type forklift mentioned above

  before, for example, when the forklift stops in the middle of a slope, in the case where a parking brake is not activated but an operator lifts his foot from the accelerator pedal, there is a problem consisting of the main forklift chassis starting to roll by itself, i.e. the main forklift chassis starting to descend along the slope at its own discretion and the speed of descent of the forklift chassis

gradually increases.

  Furthermore, recently, a forklift has been proposed of a type which uses an alternating current motor as its power source, that is to say an induction motor in place of the DC motor mentioned above. -before 3. In the case of this type of forklift, ie the induction motor type, for example as shown in FIG. 13, by activating a main switch 11, the continuous power output of a battery 2 is smoothed by a smoothing capacitor 12 and at the same time, the power is also converted into an alternating power by a three-phase bridge inverter 13 which is constituted by six field effect transistors connected in full bridge T1 to T6; and the alternating power is applied to a three-phase induction motor 14, which makes it possible to use the braking control against the current of the

induction motor 14.

  Due to the counter-current braking control of the induction motor 14, as described above, when the main chassis of forklift 1 (see Figure 12) stops in the middle of a slope, even in the if the operator lifts his foot from the accelerator pedal without applying a parking brake, the induction motor 14 is braked by counter-current, which consequently prevents the

  forklift chassis 1 does not descend along the slope.

  However, in order to be able to apply this braking against

  couarnt, it is necessary to continue applying a given voltage to the induction motor 14, which means that the power of the battery 2 continues to be consumed. In the case where such a condition is left unchanged as it is, the battery 2 is exhausted and consequently, the braking against the current by means of the induction motor 14 quickly becomes inoperative so that the main chassis of forklift 1 begins down along the slope and that the sliding speed of the main carriage frame

  riser 1 gradually increases.

  Furthermore, even in the case where the operator lifts his foot from the accelerator pedal without applying a parking brake, due to the counter-current braking produced by the induction motor 14, the main chassis of the forklift can be kept stationary in the middle of the slope; and therefore, the operator is unaware that the parking brake has not been applied. This gives rise to a problem that the abovementioned descent of the forklift chassis 1 after the exhaustion of the

  battery 2 cannot be prevented.

  Secondly, the following problem is described which occurs in the case of the movement of the lift truck from a flat road in

a slope.

  In the forklift which uses the induction motor 14 as its power source, in the case where the forklift is traveling from the flat road to the slope, as a method of controlling the speed of the forklift when an operator stops his depressing action on the accelerator pedal while the lift truck is running just before the lift truck is traveling downhill, thereby switching the lift truck driving mode to what is called a neutral mode , there is a method by which a regenerative control is implemented so as to limit the rolling speed downhill from the forklift to a given speed determined beforehand or less. In the event that the regenerative command is not executed, the speed of the forklift gradually increases due to the weight of the forklift as the forklift rolls down the slope, the result being that loads transported on the forklift may fall while the forklift goes downhill and when braking, a greater braking distance than the operator expects is

necessary.

  When the rate of travel downhill from the forklift is limited to a given speed or less, despite the fact that the operator has to set the speed of the forklift to a desired speed just before the forklift drives in the slope, in the case where the forklift begins to roll down the slope, the forklift rolls down the slope at a given speed which is different from the desired speed so that the operator cannot roll the forklift on the slope at the speed desired by the operator, so that the operator

feels an inconvenience.

  Thirdly, another problem will be described which concerns the actuation of the accelerator pedal in the case of displacement.

  of the forklift from the flat road on the slope.

  As one of the methods for controlling the rolling operation of a forklift, a rolling control method is known in which an accelerator pedal is depressed so as to apply acceleration to the forklift. to this rolling control method, even in the case where the accelerator pedal is depressed continuously at a given angle, the speed of the forklift truck increases. That is, even if the accelerator pedal is depressed continuously at a certain depressing value, the speed of the forklift is not controlled so as to correspond to the depressing value of the accelerator pedal but a difference between the accelerator pedal depressing values is controlled as

  difference between the acceleration values.

  Consequently, in accordance with the present taxiing control method, it can be understood that the forklift can be accelerated in an unrestricted manner by depressing the accelerator pedal. However, during the actual rolling operation of the forklift, in the forklift, rolling resistance occurs, which includes the friction resistance of the tires, the air resistance and other resistance categories and the acceleration mentioned above can balance with such rolling resistance, which

  makes it possible to roll the forklift at a constant speed.

  And in the case where an engine output control value when the accelerator pedal is fully depressed is established as a control value to balance the rolling resistance at the maximum speed of the forklift, the maximum speed of the truck

elevator can be established.

  The present control method has the advantages of the fact that the speed of travel of the forklift can be adjusted in accordance with the depressing value of the accelerator pedal so as to cause the forklift to roll with a feeling of driving. which is close to that obtained during the

  driving an automobile and at the same time as described above

  before, the maximum speed of the forklift can be limited.

  However, in accordance with the present driving control method, it is true that the limitation of the maximum speed is effective when the forklift is traveling on a level road but when the forklift is traveling down a slope, the limitation of the maximum speed is canceled. That is, when the forklift goes down the slope, the forklift is accelerated little by little regardless of the depressing value of the accelerator pedal and therefore the speed of the forklift exceeds

  the maximum speed previously established.

  Furthermore, the rolling control method mentioned above

  forward is a process whereby the depressing value of the accelerator pedal is proportional to the acceleration value of the forklift. However, another type of taxi control method is also known, according to which the depressing value of the accelerator pedal is proportional to the speed of the forklift. That is to say, it is a control method in which the forklift can be controlled so as to obtain a driving speed which corresponds to the depressing value of the accelerator pedal and consequently, in the case where an operator continues to depress the accelerator pedal at a given angle, the forklift is caused to roll at a speed which corresponds to the

  depressing value of the accelerator pedal.

  According to the present control method, in the case where the driving speed of the forklift when the accelerator pedal is fully depressed is established as the maximum of the forklift, the forklift can be controlled so that its speed taxiing is limited to its maximum speed or less; in particular, not only when the forklift is traveling on a level road but also when it descends a slope, since the maximum speed of the forklift is determined in accordance with the depressing value of the accelerator pedal, the forklift can be prevented from being accelerated. However, according to the present driving control method, since the driving speed of the forklift corresponds to the depressing value of the accelerator pedal, unlike the feeling of driving an automobile (the feeling obtained during driving a car at low speed), in the event that an operator is not used to the present driving control method, the operator experiences difficulties in driving the forklift using the present control method rolling; and in the case where the operator lifts his foot from the accelerator pedal, the depressing value of the accelerator pedal becomes equal to zero and consequently, the rolling speed of the corresponding forklift truck also becomes equal to zero, the result being that the forklift is suddenly stopped (a state in which the engine is suddenly regenerated). In other words, unless the operator stops depressing the accelerator pedal, the speed of the lift truck can be limited to maximum speed or less. However, according to the general driving sensation of an automobile, when the forklift which is rolling on a flat road descends a slope at the speed at which it is, naturally, the forklift is accelerated and by Consequently, the operator releases the accelerator pedal or in the case where the acceleration is significant, the operator lifts his foot from the accelerator pedal. In the event that the operator lifts his foot from the accelerator pedal in accordance with the driving sensation mentioned above, the lift truck is suddenly stopped on the slope and the operator is also in danger and in the at the same time, since the forklift carries loads in its front part, there is a risk that the loads may fall; and the fact that the forklift often rolls over a narrow passage, there is a risk that the fallen goods may

  damage peripheral property.

  As described above, preferably during normal operation of a forklift, it is possible to obtain the acceleration corresponding to the depressing value of the accelerator pedal until time o the forklift reaches its maximum speed (i.e. from zero speed to maximum speed); and in the case where the forklift exceeds the maximum speed, the forklift can be caused to roll so that the rolling speed of the forklift can be limited to the maximum speed or less. In the first example mentioned above of the conventional forklift control apparatus, the operator can operate the forklift so that the operator himself can control the depressing value of the pedal. accelerator so as to obtain an acceleration which corresponds to a depressing value of the accelerator pedal. However, when the forklift accelerates on a slope, the rolling speed of the forklift cannot be limited to the maximum speed or less. Furthermore, in the last example of the conventional forklift control device mentioned above, even when going down a slope, the forklift can roll in a state in which its maximum speed is limited but because that the rolling speed of the forklift corresponds to the depressing value of the accelerator pedal, the driving sensation which is obtained until the moment the forklift reaches maximum speed (i.e. say during the time that goes from the speed of zero to the maximum speed) is different from the feeling of driving an automobile and even when the forklift goes down the slope, in the case where the operator takes his foot off the accelerator pedal, there is a risk that

  the forklift may stop suddenly.

SUMMARY OF THE INVENTION

  In view of the above, an object of the invention is to provide a forklift control device which, after a forklift has stopped in the middle of a slope, when the pushing action of the accelerator pedal by an operator is removed without applying a parking brake, can control the rate of descent of the main frame of the forklift and can also inform the operator that the parking brake has not

not been applied.

  Another object of the invention is to provide a forklift control apparatus which allows a forklift to roll down a slope at the speed which is desired by a

operator.

  It is also an object of the invention to provide a forklift control apparatus which not only allows a forklift to roll with an acceleration which corresponds to the depressing value of an accelerator pedal until the rolling speed of the forklift reaches its maximum speed but which also, when the rolling speed of the forklift exceeds the maximum speed, can limit the rolling speed of the forklift to maximum speed or less and can exercise the command to limit maximum speed regardless of state

  activating and deactivating the accelerator pedal.

  To achieve the object mentioned above, according to a first aspect of the invention, there is provided a forklift control device which is structured so that the continuous output power of a battery on board the main chassis of a forklift is converted to alternating power by an inverter and is applied to an induction motor to power it, and the induction motor is controlled using a control portion of the forklift controller to thus implementing normal operation or regenerative operation of the forklift, o, after the main forklift chassis stops, while an accelerator pedal is not depressed, the command value of induction motor output which uses differential and proportionality control is calculated in accordance with the speed and acceleration of the main chassis forklift when the main forklift chassis rolls by itself so that the main chassis speed can be maintained

  forklift at a given low value or less.

  According to this structure, after the main forklift chassis stops, the output command value of the induction motor is calculated according to the speed and acceleration of the main forklift chassis when it is traveling by itself while the accelerator pedal is not depressed and the induction motor is controlled in accordance with the output control value thus calculated, hence the possibility of maintaining the speed of the main chassis of forklift at a value less than or equal to a given low value. Thanks to this, when the main forklift chassis stops in the middle of a slope, even in the case where the depressing action of the accelerator pedal by an operator is suppressed without applying a parking brake, the main forklift chassis slowly descends along the slope at a given low speed or less. Therefore, not only is the downhill speed of the main forklift chassis prevented from increasing as in the conventional forklift controller, but in addition, an operator can observe that the main forklift chassis slowly descends. , which informs the operator

  because the operator forgot to apply the parking brake; that is

  say that this control device can inform the operator of

  failure to apply the parking brake.

  Furthermore, in accordance with a second aspect of the invention, there is provided a forklift control apparatus such as according to the first aspect of the invention, which comprises a rotation detection part for detecting the number of revolutions of the engine at induction, a drift part to derive the speed and acceleration of the main forklift chassis from a detected value which is obtained by the rotation detection part, a switching part to switch and establish a transmission to transmit the driving force of the induction motor to a wheel of the main forklift chassis in either a forward state, a reverse state, or a neutral state, an accelerator pedal detecting portion for detecting whether a accelerator pedal is in the activated state or in the deactivated state, and a control part which, subject to the condition that when the rotation detection part detects that the main forklift chassis stops, that the switching part is established in the neutral state and that the accelerator pedal deactivation state is detected by the detection part accelerator pedal, calculates the output control value of the induction motor using the differentiation and proportionality control according to the speed and acceleration of the main forklift chassis when the forklift chassis is traveling by it - even to keep the speed low

predetermined or less.

  According to this structure, under given conditions, the output control value of the induction motor is calculated in accordance with the speed and acceleration of the main forklift chassis when it is rolling by itself and the induction motor. is controlled in accordance with the output command value thus calculated, hence the possibility of maintaining the speed of the main forklift chassis which rolls by itself at a value of

given low speed.

  Furthermore, according to a third aspect of the invention, in a forklift control apparatus according to the second aspect of the invention, the control part calculates the output command value in a forward direction and the value output control in a reverse direction, respectively, in accordance with the directions of the speed derived by

the drift part.

  According to this structure, depending on whether the main forklift chassis rolls by itself on the slope in the forward direction or in the reverse direction, the motor output command value can be calculated by taking

  take into account the direction of rotation of the motor.

  In accordance with a fourth aspect of the invention, there is provided a forklift control device structured so that the continuous output power of a battery on board the chassis of a forklift is converted to an alternative power by an inverter and be applied to an induction motor for power and the induction motor is controlled using a control portion of the forklift controller to thereby perform normal or regenerative chassis operation forklift, o, when an accelerator pedal is deactivated (that is, when the driving action exerted by the operator is removed) in order to change the mode of the forklift to a neutral mode, that the speed of the forklift when transitioning to neutral mode is established as the target speed and that the speed of the forklift has reaches or exceeds the target speed, the output control value of the induction motor which uses a differentiation and proportionality control is calculated in accordance with the target speed as well as in accordance with the speed and acceleration of the forklift in order to be able to maintain target speed when forklift speed reaches or exceeds

target speed.

  According to this structure, in the case where the operator takes his foot off the accelerator pedal (that is to say he deactivates the accelerator pedal) during the rolling operation of the forklift in order to '' thus putting the forklift in neutral mode, the output command value of the induction motor which uses a differentiation and proportionality command is calculated in accordance with the target speed during the transition to neutral mode as well as in accordance with the speed and acceleration of the forklift and the induction motor is controlled according to the calculated output command value, which allows to maintain

  forklift speed at target speed or less.

  Therefore, for example, when the forklift is rolling down the slope at the same speed as it is moving from a flat road on the slope, in case the accelerator pedal is deactivated just before the forklift is moving down the slope, the speed then being established as the target speed, the forklift is driven to descend the slope while the rolling speed of the forklift is maintained at the target speed or less . In other words, if the operator adjusts the speed of the forklift to the speed desired by the operator just before the forklift goes downhill, the forklift can roll down the slope to this

same speed.

  Furthermore, in accordance with a fifth aspect of the invention, there is provided a forklift control apparatus according to the fourth aspect of the invention, which forklift control apparatus includes a rotation detecting portion for detecting the number of revolutions of the induction motor, a drift part to derive the speed and acceleration of the forklift truck from a detected value which is obtained by the rotation detection part, an accelerator pedal detection part to detect if an accelerator pedal is in the activated state or in the deactivated state, and a control part for switching the lift truck to a neutral mode when the not depressed state of the accelerator is detected by the detection part accelerator, to establish the speed of the forklift when transitioning into neutral mode as the target speed and to calculate the value of com induction motor output command using the differentiation and proportionality control in accordance with the target speed as well as in accordance with the speed and acceleration of the forklift derived by the drift part in order to maintain the target speed when

  the forklift speed reaches or exceeds the target speed.

  According to this structure, in the case where the deactivated state (the state not depressed) of the accelerator pedal is detected by the accelerator pedal detection part and o the forklift truck has thus gone into neutral mode , the output command value of the induction motor is calculated in accordance with the target speed during the transition to neutral mode as well as in accordance with the speed and acceleration of the forklift as obtained by the drift part. Therefore, by controlling the induction motor according to the calculated output control value, the speed of the forklift can be maintained at the target speed or less when

transition to neutral state.

  Furthermore, according to a sixth aspect of the invention, in a forklift control apparatus according to the second aspect of the invention, the control part calculates the output command value in a forward direction and the value output control in a reverse direction, respectively, in accordance with the directions of the speed derived by the drift portion. According to this structure, the motor output command value while the motor direction of rotation is taken into account can be calculated depending on whether the forklift chassis rolls by itself down the slope in the direction

  forward or in reverse direction.

  In accordance with a seventh aspect of the invention, there is provided a forklift control apparatus making it possible to control a rolling engine by means of a power applied in a battery on board a main chassis of a forklift, which forklift controller includes an accelerator pedal detecting portion for detecting the depressing value of an accelerator pedal, a forklift speed sensor for detecting a forklift speed value corresponding to the driving speed of the main forklift chassis, a forklift speed calculating part for calculating a driving speed of the main forklift chassis from the forklift speed value which is obtained by the speed sensor forklift truck, a setting part to establish the maximum speed of the main chassis of cha riot forklift, a comparison and calculation part to compare and calculate the driving speed which is obtained by the forklift speed calculation part and the maximum speed established by the setting part, and a control part which, as a result of the comparison which is carried out in the comparison and calculation part, when the running speed is equal to or less than the maximum speed, calculates an engine output control value to supply to the main forklift chassis an acceleration which is proportional to the depressing value of the accelerator pedal which is obtained by the accelerator pedal detection part and when the driving speed exceeds the maximum speed, calculates an engine output control value for

  limit driving speed to maximum speed or less.

  According to the structure presented above, as long as the driving speed of the main forklift chassis has not reached its maximum speed, the forklift truck can roll with acceleration corresponding to the depressing value of the pedal. accelerator and when the lift truck speed exceeds the maximum speed, the taxi speed may be limited to the maximum speed or less. Thanks to this, during the normal rolling operation of the forklift, not only the rolling operation of the forklift can be controlled by means of a driving sensation which is such as that which can be obtained when driving a car but also, in the case where the speed of the forklift becomes higher than the maximum speed, for example when the forklift is traveling down a slope, the speed of the taxi may be limited to the maximum speed or less, this which allows to exercise a rolling command which is such that it allows

  maintain the safety of the lift truck.

  Furthermore, in accordance with an eighth aspect of the invention, there is provided a forklift control apparatus making it possible to control a driving engine by means of a power which is applied from a battery on board a main chassis d a forklift, the present forklift control apparatus comprising an accelerator pedal detecting portion for detecting the on / off states of an accelerator pedal and the depressing value therefor, a sensor for forklift speed for detecting a forklift speed value corresponding to the driving speed of the main forklift chassis, a forklift speed calculating part for calculating a driving speed of the main forklift chassis from the value of forklift speed which is obtained by the forklift speed sensor, p setting up part for establishing the maximum speed of the main forklift chassis, a comparison and calculation part for comparing and calculating the rolling speed which is obtained by the forklift speed calculation part and the maximum speed established by the setting part, and a control part which, as a result of the comparison which is carried out in the comparison and calculation part, when the running speed is equal to or less than the maximum speed, calculates a value of engine output control to provide the main forklift chassis with acceleration which is proportional to the depressing value of the accelerator pedal which is obtained by the accelerator pedal sensing portion and when the driving speed exceeds maximum speed, calculates an engine output command value to limit driving speed to maximum speed or less i nDepending on the activation / deactivation states of the accelerator pedal. According to the structure mentioned above, similarly to the structure according to the first aspect of the invention, during normal rolling operation of the forklift, not only the rolling operation of the forklift can be controlled by means of a feeling of driving which is such as that which can be obtained when driving an automobile but also, in the case where the rolling speed of the forklift becomes greater than the maximum speed, for example when the forklift is rolling downhill a slope, the rolling speed can be limited to the maximum speed or less, which makes it possible to exercise a rolling control which is such that it makes it possible to maintain the safety of the forklift. In addition to these effects, according to the present structure, the driving speed of the forklift truck can be limited to the maximum speed or less independently of the activation and deactivation states of the accelerator pedal. Therefore, even in the case where an operator releases his foot from the accelerator pedal while driving the forklift on a slope, the driving speed can be limited to the maximum speed or less, which allows the operator to release or release his foot from his hold on the accelerator pedal in the

  slope similar to when the operator drives an automobile.

  Consequently, not only can the operator drive the forklift with the same driving sensation as that in which the operator drives a car, but also the driving speed can be limited, i.e. the forklift safety can

be increased.

  In addition, in accordance with a ninth aspect of the invention, there is provided a forklift control apparatus for driving a driving engine by means of a power which is applied from a battery on board a main chassis d a forklift, the present forklift control apparatus comprising an accelerator pedal detecting portion for detecting the on / off states of an accelerator pedal and the depressing value therefor, a sensor for forklift speed for detecting a forklift speed value corresponding to the driving speed of the main forklift chassis, a forklift speed calculating part for calculating a driving speed of the main forklift chassis from the forklift speed value which is obtained by the forklift speed sensor, a part setting e to establish the maximum speed of the main forklift chassis, a comparison and calculation part to compare and calculate the rolling speed which is obtained by the forklift speed calculation part and the maximum speed established by the setting part, and a control part which, as a result of the comparison which is carried out in the comparison and calculation part, when the driving speed exceeds the maximum speed, calculates an output control value of engine to limit driving speed to maximum speed or less regardless of the accelerator pedal activation / deactivation states. In accordance with the structure mentioned above, the driving speed of the forklift truck can be limited to the maximum speed or less regardless of the activation / deactivation states of the accelerator pedal. Thanks to this, even in the case where the operator releases his foot from holding the accelerator pedal on a slope, the driving speed of the forklift can be limited to the maximum speed or less. Therefore, not only the operator can drive the forklift with the same driving feeling

  than that experienced when the operator drives an automobile,

  say that the operator can release or remove his foot from his support on the accelerator pedal on the slope, but in addition, the rolling speed of the forklift can be limited, that is to say the safety of the

  forklift can be increased.

  Still further, in accordance with a tenth aspect of the invention, in a forklift controller according to any one of the seventh to ninth aspects of the invention, the present forklift controller further includes a portion of rotation detection for detecting the number of revolutions of the rolling engine, and a drift part for deriving the speed and acceleration of the main forklift chassis from a detected value which is obtained by the part for detecting rotation, where the control part derives the speed and acceleration of the main forklift chassis from the number of engine revolutions obtained by the rotation detection part and in accordance with the derived speed and acceleration, calculates the output command value. In accordance with the structure presented above, since the motor output control value is calculated in accordance with the speed and acceleration of the forklift while it is moving, controlling the motor in accordance with the output control value of the motor thus calculated, the self-rolling speed of the carriage

  elevator can be limited to an established value or less.

  Still further, in accordance with an eleventh aspect of the invention, in a forklift controller according to any of the seventh to tenth aspects of the invention, the present forklift controller further includes a portion switch for switching and establishing a transmission for transmitting the driving force of the driving motor to a wheel in either a forward state, a reverse state or a neutral state, or the control part, in accordance with the states switched from the transmission by the switching part, calculates the output control value for a forward direction and the output control value for a reverse direction, respectively. According to the structure presented above, depending on whether the forklift is traveling in a forward direction or a reverse direction, the motor output command value while the direction of rotation of the motor is taken into account is calculated; and the rolling speed of the forklift truck may be limited to the maximum speed or less as established by the establishment part both in the forward direction and in the direction of

reverse.

  What is more, in accordance with a twelfth aspect of the invention, in a forklift control apparatus according to any one of the seventh to tenth aspects of the invention, the above-mentioned rolling motor is constituted by a motor induction and the continuous output power of the battery mentioned above is converted to alternating power by an inverter and then is

  applied to this induction motor.

  In accordance with the above-mentioned structure, a control signal from the inverter which arrives at the induction motor can be controlled so that the motor output control value can become the output control value which is calculated by the control part. Thanks to this, on a flat road, the induction motor can be controlled so as to implement normal operation and on a slope, the induction motor can be controlled so as to implement regenerative operation, which makes possible to limit speed

  of the lift truck traveling at maximum speed or less.

BRIEF DESCRIPTION OF THE DRAWINGS

  Figure 1 is a block diagram of an embodiment of a forklift control apparatus according to the invention; Figure 2 is a flowchart for explaining the operation of the embodiment presented above; Figure 3 is a flowchart for explaining the operation of the embodiment presented above; Figure 4 is a flowchart for explaining the operation of the embodiment presented above; Figure 5 is a flowchart for explaining the operation of the embodiment presented above; Figure 6 is a flowchart for explaining the operation of the embodiment presented above; Figure 7 is a flowchart for explaining the operation of the embodiment presented above; Figure 8 is a flowchart for explaining the operation of the embodiment presented above; Figure 9 is a flowchart for explaining the operation of the embodiment presented above; Figure 10 is a flowchart for explaining the operation of the embodiment presented above; Figure 11 is a flow chart for explaining the operation of the control apparatus in accordance with the embodiment of the invention; Figure 12 is a side view of a conventional forklift of the DC type; and Figure 13 is a circuit diagram of a control circuit

  which is used in a conventional three-phase induction motor.

  DETAILED DESCRIPTION OF THE FIRST EMBODIMENT

OF THIS INVENTION

  Now, a description of a first embodiment

  according to which the present invention is applied to a forklift of a type with counter-current braking will be presented with reference to Figures 1 to 4. Here, Figure 1 is a block diagram of a control apparatus according to the mode of embodiment of the invention and FIGS. 2 to 4 are respectively flow diagrams for the explanation of the operation of the forklift control apparatus which

is shown in figure 1.

  Here, the forklift truck of a type with counter-current braking is the same in terms of structure as the forklift truck shown in FIG. 12 except that an induction motor is used in place of the DC motor 3 and therefore

  in the description which follows, reference will also be made to the figure

  12. Furthermore, according to the present embodiment, similarly to the induction motor 14 which is represented in FIG. 13, a three-phase induction motor is used and an inverter which is used to drive the three-phase induction motor is identical from the point of view of the structure with the three-phase bridge inverter 13 shown in FIG. 13; therefore, reference will also be made to Figure 13 in the

description which follows.

  As shown in FIG. 1, a detection signal from an accelerator pedal detection part (not shown) proportional to the depressing value of an accelerator pedal 9 is converted according to a digital signal by an analog / digital (A / D) conversion part 21 so that a central processing unit or CPU which will be discussed later can detect the activation and deactivation states and the depressing value of a pedal accelerator based on an action

  depressing the accelerator pedal 9 exerted by an operator.

  Furthermore, as shown in FIG. 13, on the rotating shaft of the induction motor 14 is arranged a rotation detection part, which rotation detection part consists of a rotary encoder; and output pulses from the rotation detection part 15 are counted by a counter 22 and from the value thus counted, the number of revolutions of the induction motor 14

  can be detected by the CPU, which will be discussed later.

  In addition, the switched state of a directional lever or gear lever 4 which acts as a switching part which switches and establishes the transmission means (not shown) for transmitting the driving power of the induction motor 14 to the wheels of the forklift in either the forward operating state, the reverse operating state or the neutral position state is entered via a parallel input part (P1) 23 into the CPU, of which it will be discussed later and the CPU appreciates the state in which the directional lever 4 is established, namely either the forward operating state, or the reverse operating state, or the state

from neutral.

  Not only data such as the depressing value of the accelerator pedal 9, the number of revolutions of the induction motor and the switched state of the directional lever 4, but also data such as activation / deactivation data of brake to be detected by a brake detection part (not shown in FIG. 1) and parking brake activation or non-activation data intended to be detected by a parking brake detection part are temporarily stored in a random access memory or RAM 25; and in accordance with a given control program which is stored beforehand in a read only memory or ROM 26, the CPU 27 outputs PWM control pulses from a pulse width modulation pulse output part (PWM) 28 on the control terminals of the respective transistors T1 to T6 of an inverter 13 in order to control the output current of the induction motor 14, hence the control of normal operation or of the

  regenerative operation of the forklift.

  Thus, in the CPU 27, subject to the condition that, when the speed and acceleration of the main chassis of forklift 1 are derived from the number of engine revolutions detected by the rotation detection part 15 and when the stopping of the main forklift chassis 1 is recognized from the output of the rotation detection part 15, the directional lever 4 is established in the neutral state and the deactivation states of the accelerator pedal and of the brake are detected respectively by the accelerator pedal detecting part and the brake detecting part, the output control value of the induction motor 14 which uses a differentiation and proportionality (PD) control is calculated according to the speed and acceleration of the main forklift chassis 1 when driving by itself because the operator forgets to apply the parking brake , i.e. when the main chassis of forklift 1 descends along the slope at its own discretion, in order to be able to maintain the speed of the main chassis of forklift 1 at a given low speed (e.g. about 5 km / h). Here it goes without saying that the speed limit using the PD command is not limited

at the 5 km / h mentioned above.

  The pulse output part PWM 28 is controlled in accordance with the output control value thus calculated so as to thus control the number of revolutions of the induction motor 14 so that the command in regenerative operation of the motor to

  induction 14 can be performed.

  In this case, depending on the direction of the main forklift chassis 1, i.e. depending on whether the main forklift chassis 1 rolls by itself in the forward direction or the direction of reverse, the CPU 27 derives the positive direction or the negative direction of the speed also, and in accordance with the derived speed direction, it calculates the output command value of the induction motor 14 according to the positive direction of rotation of the motor at induction 14 (for the forward operation of the main forklift chassis 1) or in the negative direction of rotation of the induction motor 14 (for the reverse operation of the main forklift chassis 1). The speed and acceleration bypass processing by means of the CPU 27 corresponds to a bypass part while the output command value calculation processing of the induction motor 14 corresponds

to an order part.

  Furthermore, the calculation of the output command value by means of the CPU 27 can be carried out in accordance with the following two equations, that is to say: Mf = kl x V + k2 x G (in the case of forward) (1) Mb = - kl x V - k2 x G (in the case of reverse) (2) o the gains (coefficients) of a control system are expressed as kl, k2 , the output control value of the induction motor 14 in the case where the self-driving direction of the main forklift chassis is the forward direction is expressed as Mf and the output value of the motor induction 14 in the case where the self-driving direction of the main forklift chassis is the reverse direction is expressed as Mb. Here, the first right member terms of the above-mentioned equations (1) and (2) respectively express proportionality control components (P) at the level of the differentiation and proportionality control (PD) while the second terms of these same equations express respectively

  differentiation control components (D).

  Then a description of the operation of the

  forklift control mentioned above will be presented below

  after with reference to the organizational charts which are respectively

  shown in Figures 2 to 4.

  As shown in FIG. 2, first of all, the control device which includes the RAM 25 is initialized by the CPU 27 (Sl), a signal which is proportional to the depressing value of the accelerator pedal is sought from the accelerator pedal detection part (S2), the switched state of the directional lever 4 is entered via P123 (S3), a count value is sought from the counter 22 (S4 ) and the output of the brake detection part is sought (S5). And it is checked whether the accelerator pedal is activated (i.e. if it is depressed) or not (S6). If it turns out that the result of the check is YES, then it is checked whether the switched state of the directional lever 4 is either the forward state, the reverse state, or the neutral state. (S7). If it is found that the directional lever 4 is in a state taken from the forward operating state and the reverse operating state, then a descent indicator which is constituted by a register incorporated in the CPU 27 is reset to l initial state (S8), a normal taxi control processing is implemented (S9) and then the

  processing proceeds to a step S16 which will be discussed later.

  Here, with reference to the normal rolling processing of step S9, this processing is a processing (S20) which, as shown in FIG. 3, multiplies a gain (a coefficient) given by the depressing value of the pedal d accelerator 9 so as to find a command value of

  engine output during normal driving operation.

  Then if the result of the verification at step S6 mentioned above turns out to be NO, then the accelerator pedal is deactivated (i.e. it is not depressed) and by Consequently, it is checked whether or not the speed of the main chassis of forklift 1 which is derived from the counting value sought in step S3 is zero or not (S10). If this verification result turns out to be YES, that is to say if the speed of the main chassis of forklift 1 turns out to be zero and therefore, it is found that the main chassis 1 is at stop, then it is checked from the output of the brake detection part sought in step S5 whether the brake is activated or not (S1 1). If this verification result turns out to be YES, then the descent indicator of the CPU 27 is established (S12) and the output command value of the induction motor 14 is established at zero (S13) and then, the processing proceeds to step S16 which will be discussed later. Thus, according to a variant, the processing mentioned above can also be carried out in the following manner: that is to say that while omitting the processing of steps 5 and 11, it is checked whether the speed of the main chassis of forklift 1 is zero or not and if the verification result turns out to be YES, then the descent indicator of the CPU 27is established (S 12).

  Furthermore, if the verification result of the step mentioned above

  before S10 is NO, then it is appreciated that the main chassis of forklift 1 is rolling at a certain speed and at step S14, it is checked whether the descent indicator is set or not (S14 ). If this verification result is NO, then it can be appreciated that a descent command which will be discussed later is not necessary and therefore, in association with a case in which the verification result of the step mentioned above before Sl 1 is NO, the processing proceeds to the step mentioned above S13. On the other hand, if the verification result at step S14 is YES, then the processing proceeds to step S15 and the descent control processing is executed (S15). At the level of the descent control processing, as shown in FIG. 4, in accordance with the speed V and the acceleration G of the main chassis of forklift 1 derived from the count value of the counter 22 sought at the level of l step S4, it is checked whether the speed V is positive or negative (S25) and if the speed V turns out to be positive, then the output control value Mf of the induction motor 14 is calculated according to the equation mentioned above. - forward (1) for the forward operation (S26); and if the speed V turns out to be negative, then the output control value Mb of the induction motor 14 according to the above-mentioned equation (2) for the reverse operation

  (S27) is calculated and then, similarly to the case mentioned above

  before which the processing of step S26 is carried out, the processing

  returns to the main program shown in Figure 2.

  As shown in FIG. 2, after the processing operations of the above-mentioned steps S19, S13 and S15 are executed, the processing proceeds to the next step S16 at which level, in accordance with the output control value of the motor to induction 14 calculated at the above-mentioned step S9, the pulse output part PWM 28 is controlled by the CPU 27 and thus, the number of revolutions of the induction motor 14 is controlled so as to produce a speed which corresponds to the insertion value of the

accelerator pedal (S16).

  Furthermore, in the case of step S13, the induction motor 14 is controlled so that the output of the induction motor 14 is equal to zero, that is to say that the induction motor 14 is controlled so as to stop (S16). Furthermore, in the case of step S15, in accordance with the output control value Mf or Mb which is calculated in step S15, the pulse output part PWM 28 is controlled by the CPU 27 and thus, the number of revolutions of the induction motor 14 is controlled so that the speed of the main chassis of the forklift 1 becomes equal to or less than a given preset low speed, for example around 5 km / h (S16)

  and then the processing returns to the above-mentioned step S2.

  Consequently, when the main chassis of forklift 1 stops in the middle of the slope, even in the case where the operator takes his foot off the accelerator pedal without applying the parking brake, by calculating the command value of output Mf or Mb of the induction motor 14 in accordance with the speed and acceleration of the main chassis of forklift 1 when it descends along the slope and then by controlling the induction motor 14 in accordance with the output value thus calculated, the lowering speed of the main chassis of forklift 1 can be maintained at a given preset value,

for example 5 km / h or less.

  Therefore, in accordance with the above-mentioned embodiment, the fact that the descent speed of the main forklift chassis 1 does not increase too much as in the conventional forklift controller, the fear that the main chassis forklift 1 can descend at a high speed and collide with a wall or a fixed object and thus the

breaking can be reduced.

  Furthermore, in the case where the operator can see that the main chassis of forklift 1 is going down at a low speed, this descent at low speed of the main chassis of forklift 1 can have the effect that the operator is put at

  aware that the operator forgot to apply the parking brake.

  That is, in accordance with this embodiment, it is possible to obtain a notification effect of non-application of

parking.

  Furthermore, in accordance with the present embodiment, the risk that the battery 2 will be exhausted during the braking operation can be prevented, which occurs in the conventional forklift control apparatus when the main forklift chassis 1 is brought to a complete stop due to regenerative braking which uses the induction motor. That is, it is possible to eliminate the

  disadvantages generated by the depletion of the battery 2.

  Thus, according to the embodiment mentioned above, the

  description of the case in which the induction motor 14 is constituted

  by a three-phase induction motor was presented. However, of course, the induction motor 14 is not limited to the three-phase induction motor but it can also be constituted by a two-phase or two-phase induction motor or by an induction motor comprising

four or more phases.

  Furthermore, according to the embodiment mentioned above, the

  description of the case in which the invention is applied to the carriage

  riser of a reverse braking type has been presented.

  However, the application of the invention is not limited to the forklift of a type with counter-current braking but of course, the invention can also be applied to other types of forklifts, for example a forklift of a carrier type and a forklift which uses an induction motor of any other type as its power source. In this case also, the effect which is equivalent to that of the embodiment can be obtained.

mentioned above.

SECOND EMBODIMENT

  Now a description of a second embodiment

  according to which the present invention is applied to a forklift of a type with counter-current braking will be presented with reference to Figures 1 as well as 5 to 10. Here, Figure 1 is a block diagram of a control apparatus in accordance in the embodiment of the invention and FIGS. 5 to 10 are respectively flow diagrams for the explanation of the operation of the control device for

  forklift which is shown in figure 1.

  Here, the forklift truck of a type with counter-current braking is the same from the structural point of view as the forklift truck which is shown in FIG. 12 except that an induction motor is used instead and place of the DC motor 3 and therefore,

  in the description which follows, reference will also be made to the figure

  12. Furthermore, according to the present embodiment, similarly to the induction motor 14 which is shown in FIG. 13, a three-phase induction motor is used and an inverter which is used to drive the three-phase induction motor is identical from the point of view of the structure with the three-phase bridge inverter 13 which is represented in FIG. 13. By

  Consequently, reference will be made to FIG. 13 in the description which

  follows. As shown in FIG. 1, a detection signal which is produced from an accelerator pedal detection part (not shown) and which is proportional to the depressing value of an accelerator pedal 9 is converted according to a digital signal by an analog-digital (A / D) conversion part 21 so that the activation and deactivation states of the accelerator pedal 9 as well as its depressing value are detected by a unit central processing unit or CPU which will be discussed later. Furthermore, as shown in FIG. 13, on the rotating shaft of the induction motor 14 is disposed a rotation detection part 15 which is constituted by a rotary encoder and output pulses coming from the rotation detection part 15 are counted by a counter 22 and from the value thus counted, the number of revolutions of the induction motor 14 can be detected by the CPU of which it will be

discussed later.

  In addition, the switched state of a directional lever 4 which acts as a switching part which switches and establishes the transmission means (not shown) for transmitting the driving power of the induction motor 14 to the wheels of the forklift according to a state taken from the forward and reverse states or according to a neutral state is entered via a parallel input part (P1) 23 in the CPU which will be discussed later and the CPU assesses the state in which the directional lever 4 is established, namely a state taken from the forward state, the reverse state

and the neutral state.

  Data such as the depressing value of the accelerator pedal 9, the number of revolutions of the induction motor and the switched state of the directional lever 4 are temporarily stored in a random access memory or RAM 25 and in accordance with a program of given command which is stored beforehand in a read only memory or ROM 26, the CPU 27 outputs PWM control pulses from a pulse width modulation pulse output part (PWM 28) on the control terminals of the respective transistors T1 to T6 of an inverter 13 in order to control the output current of the induction motor 14, thereby controlling the normal operation or the regenerative operation of the forklift. In this context, in the CPU 27, the speed and acceleration of the main forklift chassis 1 are derived from the number of revolutions of the engine detected by the rotation detection part 15. Furthermore, in the case where, when the deactivation state (not depressed) of the accelerator pedal is detected by the accelerator pedal detection part, the forklift truck is switched to neutral mode and the speed of the forklift truck during the transition in the neutral mode is established as the target speed, on the basis of the current target speed as well as on the basis of the forklift speed and acceleration which are derived by the CPU 27, the CPU 27 calculates the value for controlling the output of the induction motor 14 using a differentiation and proportionality (PD) control so as to be able to maintain the target speed when the speed of the

  forklift exceeds target speed.

  The PWM pulse output portion 28 is controlled in accordance with the output control value thus calculated so as to control the number of revolutions of the induction motor 14 so that the regenerative operation control of the motor to

  induction 14 can be performed.

  In this case, depending on the direction of the main chassis of forklift 1, i.e. depending on whether the main chassis 1 rolls by itself in the forward direction or in the reverse direction , the CPU 27 derives the positive direction or the negative direction of the speed also and in accordance with the derived speed direction, it calculates the output command value of the induction motor 14 according to the positive direction of rotation of the induction motor 14 ( for the forward operation of the main forklift chassis 1) or in the negative direction of rotation of the induction motor 14 (for the reverse operation of the main forklift chassis 1). The speed and acceleration bypass processing by means of the CPU 27 corresponds to a drift part while the command value calculation processing of

  output of the induction motor 14 corresponds to a control part.

  Furthermore, the calculation of the output command value by the CPU 27 can be carried out in accordance with the following two equations: Mf = kl x (V -Vt) + k2 x G (in the case of forward gear) Mb = - kl x (V - Vt) k2 x G (in the case of reverse) o the speed during the transition to neutral mode is expressed as Vt, the input speed and acceleration which are derived from the output of the rotation detection part 15 by the CPU 27 are expressed respectively as V and G, the gains (the coefficients) of a control system are expressed as kl, k2, the value of the output control of the induction motor 14 in the case where the self-rolling direction of the chassis is the forward direction is expressed as Mf and the output control value of the induction motor 14 in the case o the chassis self-driving direction is the reverse direction is expressed as Mb. Here, the

  first terms of the right members of the two equations presented above

  before respectively express control components of

  proportionality (P) at the proportionality control -

  differentiation (PD) while the second related terms express

  respectively differentiation control components (D).

  Then a description of the operation of the

  forklift control mentioned above will be presented below

  after with reference to the organizational charts which are respectively

  shown in Figures 5 to 10.

  First, the description of a main program of the

  operation of this forklift controller will be presented below. As shown in FIG. 5, first of all, the respective devices of the forklift controller including the RAM 25 are initialized by the CPU 27 and a mode indicator which is constituted by registers incorporated in the CPU 27 is set to "neutral" (S101), a signal which is proportional to the depressing value of the accelerator pedal 9 is sought from the accelerator pedal detection part (S102), the switched state of the directional lever 4 is entered via P123 (S103), a count value is sought from counter 22 (S104) and the mode indicator is sought to determine whether it represents "forward" or not ( S105). If the verification result turns out to be YES (S106), then a forward control command processing which will be discussed later is executed (S106); and if the verification result turns out to be NO, then the mode indicator is checked to determine whether it represents "reverse" or not (S107). If the verification result turns out to be YES, then a reverse command processing which will be discussed later is executed (S 108); and if the verification result turns out to be NO, then the mode indicator is verified to determine whether it represents "speed regeneration controlled by going downhill in forward gear" or not (S109). If the verification result turns out to be YES, then a speed regeneration command processing commanded by forward descent of the slope which will be discussed later is executed (S 1 0); and if the verification result turns out to be NO, then the mode indicator is verified so as to determine whether it represents a "speed regeneration controlled by going downhill in reverse" or not (S 11). If the verification result turns out to be YES, then a speed regeneration command processing commanded by going downhill in reverse which will be discussed later is executed (Si 12); and if the verification result turns out to be NO, then the processing proceeds to neutral mode processing (S113). Then, the processing returns to step S102 in a similar manner to after the steps mentioned above S106,

  S108, S1 10 and Sl 12 are respectively processed.

  Then a description of the processing in neutral mode at the level of

  step S113 represented in FIG. 5 will be presented below with reference to FIG. 6. Here, when the processing has gone into neutral mode, the speed of the forklift which is derived from the count value of the counter 22 sought at step S104 shown in Figure 5 is assumed to be a target speed Vt. First, as shown in Figure 6, the target speed Vt is established as the input speed V (S121) and on the basis of a signal from the accelerator pedal detecting part which is sought at step S103 shown in FIG. 5, it is checked whether the accelerator pedal is activated (is depressed) or not

(S122).

  If this verification result turns out to be YES, then it is checked whether the switching state of the directional lever 4 is "forward" or "reverse" or "neutral" (S123). If the switched state turns out to be "forward", then the mode indicator is set for "forward" (S124); if it turns out to be "reverse", then the mode indicator is set for "reverse" (S125); and if it turns out to be "neutral", then the processing goes to step S126 in a similar manner to the case where the verification result of step S122 turns out to be NO, case in which it is

  checked whether the input speed V is positive or negative (S126).

  If the verification result at the verification step mentioned above S106 turns out to be YES, then it can be appreciated that the forklift was advancing at the moment of transition to neutral mode and therefore, the mode indicator is set for "speed regeneration controlled by going downhill in forward" (S127). On the other hand, if the verification result turns out to be NO, then it is checked whether the input speed V is positive or negative (S128). If the verification result turns out to be YES, then it can be appreciated that the forklift was moving in reverse at the time of transition to neutral mode and therefore the mode indicator is established for "speed regeneration controlled by running downhill

rear "(S129).

  Furthermore, if the verification result of the step mentioned above

* before S128 is NO, then similarly to after the steps mentioned above S124, S125, S127 and S129, the processing goes to a step S130 at which the output of the induction motor 14 is controlled so as to be deactivated (S131). Then the

  processing returns to the main program shown in Figure 5.

  Here, a description of the forward command processing

  in step S106 of FIG. 5 will be presented hereinafter with reference to FIG. 7. As shown in FIG. 7, the engine output control value during forward travel operation can be calculated from the product of a given gain (a positive coefficient) and the accelerator pedal depressing value, and the output of the induction motor 14 can be controlled in accordance with the output command value thus calculated ( S141). And according to a signal from the accelerator detection part, it is checked whether the accelerator pedal is activated or not (S142). If the verification result turns out to be YES, it is checked if the switched state of the directional lever 4 is "forward"

  or "reverse" or "neutral" (S143).

  If the verification result of the above mentioned step S142 turns out to be NO and if the verification result of the above mentioned step S143 turns out to be "reverse" or "neutral", the processing passes in step 144 and the mode indicator is set to "neutral" (S144). Then, similarly to the case where the verification result of step S143 turns out to be "forward", the processing returns to

  main program which is shown in figure 5.

  Furthermore, the description of the order processing in

  reverse at step S108 of Figure 5 will be shown below with reference to Figure 8. As shown in Figure 8, the engine output control value during a reverse run operation may be calculated from the product of a given gain (a negative coefficient) and the accelerator pedal depressing value, and the output of the induction motor 14 is controlled in accordance with the output value thus calculated (S151). And according to a signal from the accelerator pedal detecting part, it is checked whether the accelerator is activated or not (S152). If the verification result turns out to be YES, then it is checked whether the switched state of the directional lever 4 is "forward" or "on

rear "or" neutral "(S153).

  If the result of verification of the step mentioned above S152 turns out to be NO and if the verification result of the step mentioned above S153 turns out to be "reverse" or "neutral", then the processing go to step S154 and the mode indicator is set to "neutral" (S154). Then, similarly to the case where the verification result of step S153 turns out to be "reverse", the processing

  returns to the main program which is shown in figure 5.

  In addition, a description of the order processing of

  speed regeneration controlled by going downhill in forward direction of step S110 of FIG. 5 will be presented below with reference to FIG. 9. As shown in FIG. 9, first of all, it is checked whether the speed target Vt is greater than the input speed V or not (S161). If the verification result turns out to be YES, then the target speed Vt is established as the input speed V (S162) and then, similarly to the case where the verification result of step S161 turns out being NO, the processing goes to step S163 at which the output control value Mf of the induction motor 14 in the case of forward travel relative to the target speed Vt is calculated and at the same time, the The output of the induction motor 14 is controlled in accordance with the thus calculated output control value Mf (S163). In this context, when the output command value Mf is less than zero, the output command value Mf

is treated as zero.

  According to a signal from the accelerator detection part, it is checked whether the accelerator is activated or not (S164). If the verification result turns out to be YES, then it is checked whether the switched state of the directional lever 4 is "forward" or "reverse" or "neutral" (S165). If the switched state turns out to be "neutral", then similarly to the case where the verification result of the step mentioned above S164 turns out to be NO, the processing proceeds to a step S166 at which it is checked whether the input speed V which is established in step S162 is equal to or less than zero or

no (S166).

  If the verification result turns out to be YES, similarly to the case where the verification result of step S165 turns out to be "forward" or "reverse", the processing proceeds to step S167 at

  level at which the mode indicator is set to "neutral" (S167).

  Then, similarly to the case where the verification result of step S166 turns out to be NO; processing returns to the main program which

  is shown in Figure 5. In addition, a description of the processing of

  speed regeneration command controlled by going downhill in reverse in step S112 of FIG. 5 will be presented below with reference to FIG. 10. In this case, since the speed during a running operation in operation forward is assumed to be positive, the speed during a reverse driving operation is negative. As shown in Fig. 10, firstly, it is checked whether the target speed Vt is lower than the input speed V or not (S171). If the verification result turns out to be YES, then the target speed Vt is established as the input speed V (S172) and then, similarly to the case where the verification result of step S171 turns out being NO, the processing goes to a step S173 at which the output control value Mb of the induction motor 14 in the case of reverse operation with respect to the target speed Vt is calculated and at the same time , the output of the induction motor 14 is controlled in accordance with the thus calculated output control value Mb (S173). In this context, when the output command value Mb is greater than zero, the output command value Mf

  is considered to be zero.

  According to a signal from the accelerator detection part, it is checked whether the accelerator pedal is activated or not (S174). If the verification result turns out to be YES, then it is checked whether the switched state of the directional lever 4 is "forward" or "reverse" or "neutral" (S175). If the switched state turns out to be "neutral", then similarly to the case where the verification result of the step mentioned above S171 turns out to be NO, the processing goes to a step S176 at which it is checked whether the input speed V which is established in step S162 is equal to or greater than zero or not (S176). If the verification result turns out to be YES, similarly to the case where the verification result of step S175 turns out to be "forward" or "reverse", the processing proceeds to step S177 at

  level at which the mode indicator is set to "neutral" (S177).

  Then, similarly to the case where the verification result of step S176 turns out to be NO, the processing returns to the main processing which

is shown in Figure 5.

  As described above, in the case where the accelerator is deactivated by switching during normal operation of the lift truck and o the lift truck is thus switched to neutral mode, the output control value of the induction motor 14 is calculated in accordance with the target speed Vt during the transition to neutral mode as well as in accordance with the speed V and the acceleration G of the forklift, and the induction motor 14 is controlled in accordance with the output command value thus calculated. For example, when an operator drives the forklift at the same speed as the forklift travels from a flat road on a slope, in case the accelerator pedal is deactivated just before the forklift advance in the slope, the speed in forward direction in the slope being considered as target speed Vt, the forklift is brought down the slope without acceleration while the speed of the forklift is

  maintained at target speed Vt or less.

  Consequently, in accordance with the embodiment mentioned above, in the case where the operator sets the depressing value of the accelerator pedal 9 just before the forklift enters the slope in order to thereby adjust the speed of the forklift at the desired speed, the forklift can roll in

  descending the slope at the speed then in effect.

  In this context, according to the embodiment mentioned above

  before, a description of the case in which the induction motor 14 is

  consisting of a three-phase induction motor was presented. However, of course, the induction motor 14 is not limited to the three-phase induction motor but it can also be constituted by a two-phase or two-phase induction motor or by a motor with

  induction with four or more phases.

  Furthermore, according to the embodiment mentioned above,

  a description of the case in which the invention is applied to the carriage

  riser of a reverse braking type has been presented.

  However, the application of the invention is not limited to the forklift of a type with counter-braking but of course, the invention can also be applied to other types of forklift, for example a forklift of a carrier type and a forklift which uses an induction motor of any type as its power source. In this case also; we can get the effect which is equivalent to that of the embodiment

mentioned above.

THIRD EMBODIMENT

  Now a description of a third embodiment

  of a forklift control device according to the invention when the invention is applied to a forklift of a type with counter-current braking will be presented with reference to Figures 1, 3 as well as 11 to 13. In a way more specifically, Figure 12 is a schematic view of a forklift to which the present forklift control apparatus according to the invention is applied, Figure 13 is a circuit diagram of part of this carriage control apparatus Figure 1 is a block diagram of the present forklift control apparatus and Figures 3 and 11 are flowcharts respectively to explain the

  operation of this forklift control unit.

  As shown in FIG. 12, in order to make a forklift roll, power can be applied to a rolling engine 3 from a battery 2 which is loaded on board the main chassis 1 of the forklift. During this operation, a transmission means (not shown) which is used to transmit the driving power of the running engine 3 to the wheels is switched to one of its operating states, that is to say a state forward / reverse and a neutral state for parking by activating a directional lever (or a directional switch) 4 which is used to switch the transmission means into one of the forward / reverse and neutral states while the forklift is steered using a steering wheel 5. In this context, in FIG. 12, a reference index 6 represents a mast which is arranged in the front part of the chassis 1, a reference index 7 represents a lifting console which is arranged on the mast 6, a reference index 8 represents 2 forks which are arranged on the lifting console and a reference index 9

  represents an accelerator pedal, respectively.

  The running motor 3 is constituted for example by a three-phase induction motor which is an alternating current motor. That is, as shown in FIG. 13, in the case where a main switch 11 is activated by switching, the continuous output power of the battery 2 is smoothed by a smoothing capacitor 12 and is also converted according to an alternating power by a three-phase bridge inverter 13, which is constituted by 6 field effect transistors T1 to T6 which are connected together like a full bridge while the alternating power is applied to a motor

three-phase induction 14.

  Then a description of the structure of this device

  Forklift control will be presented below. As shown in FIG. 1, a detection signal which is supplied from an accelerator detection part (not shown) and which is proportional to the depressing value of the accelerator pedal 9 is converted according to a digital signal by an analog / digital converter (A / D) part 21 while the activation / deactivation states and the depressing value of the accelerator pedal 9 can be detected by a central processing unit or CPU which will be discussed later. Furthermore, as shown in FIG. 13, on the rotating shaft of the induction motor 14 is arranged a rotation detection part 15 which is constituted by a rotary encoder; an output pulse from the rotation detection part 15 is counted by a counter 22, and from the count value of the counter 22, the number of revolutions of the induction motor 14 is detected by the CPU (of which

it will be discussed later).

  In addition, the switched state of the directional lever 4 which acts as a switching part for switching the transmission means (not shown) for transmitting the driving power of the induction motor 14 to the wheels in one of the operating states. forward / reverse and neutral has entered the CPU which will be discussed later so that the CPU appreciates the switched state of the directional lever 4, i.e. the CPU checks whether the directional lever 4 is switched and established in the direction of travel

  forward, reverse or neutral.

  Furthermore, an establishment part 24 which is constituted for example by an establishment switch and which is used to establish a ceiling speed according to three levels, ie for example 5 km / h, km / h and 15 km / h is planned, and the ceiling speed which is established by switching the setting part 24 is sought by the CPU which will be discussed later and the rotation of the induction motor 14 is controlled so that the actual running speed of the forklift can be limited to the speed limit or can be set at

  a lower speed by switching the setting part 24.

  The data concerning the depressing value of the accelerator pedal 9, the number of revolutions of the engine, the switched state of the directional lever 4 and the top speed as established by the setting part 24 are stored and maintained in a random access memory or RAM 25. According to a given control program which is stored beforehand in a read only memory or ROM 26, a CPU 27 allows a pulse output part with pulse width modulation (PWM: pulse width modulation) 28 to output PWM control pulses on the control terminals of the respective transistors T1 to T6 of the inverter 13 so that the output current of the induction motor 14 is controlled so as to implement a command normal rolling operation or command

regenerative operation.

  In this context, the CPU 27, during the running operation of the forklift, operates and derives the running speed and the acceleration of the chassis 1 from the number of revolutions of the engine (the value for detecting forklift speed) detected by the rotation detection part 15 which acts as a forklift speed sensor; and in accordance with the speed and the driving acceleration thus derived from the main chassis 1, the CPU 27 calculates the output command value of the induction motor 14 using proportionality - differentiation (PD) so as to be able to limit the speed of taxiing at the ceiling speed or at a lower speed established by the setting part 24. During this operation, the driving speed and the ceiling speed established by the setting part 24 are compared with each other by the CPU 27. For example, in the case where the ceiling speed is established at the speed of 15 km / h, the output control value of the induction motor 14 is calculated so that the driving speed cannot exceed 15 km / h and in accordance with the output command value thus calculated, the pulse output part PWM 28 is controlled so as to be able to

  control the number of revolutions of the induction motor 14.

  During this operation, at the same time, the CPU 27 can derive the positive and negative directions of the driving speed in accordance with whether the self-driving direction of the main chassis 1 is in the forward direction or the direction of reverse and in accordance with the driving speed direction, the output command value of the induction motor 14 which corresponds to the direction of rotation of the forward gear (forward state) of the induction motor 14 or to the reverse direction of rotation (reverse state) of the induction motor 14 can be calculated. Furthermore, the output command values obtained by means of the CPU 27 are respectively calculated by means of the following equations: Mf = kl x (V -Vs) + k2 x G (in the case of forward gear) Mb = - kl x (V - Vs) - k2 x G (in the case of reverse) o Vs represents the ceiling speed established by the setting part 24, V represents the derived driving speed, G represents the acceleration, kl and k2 represent the gains (the coefficients) of the control system, Mf represents the output control value of the induction motor 14 in the case where the driving direction is the forward direction and Mb represents the control value of output of the induction motor 14 in the case where the driving direction is the reverse direction. Here, the first terms of the right members of the two equations mentioned above represent components of proportionality control (P) at the level of the proportionality command - differentiation (PD) while the second terms of the right members represent components of

differentiation command (P).

  Then a description of the operation of this device

  forklift control will be presented below with reference to

  a flowchart which is shown in Figure 11.

  As shown in FIG. 11, first of all, the CPU 27 initializes the forklift control unit taken as a whole which includes the RAM 25 (S201), it searches for a signal proportional to the depression value of the accelerator pedal from the accelerator pedal detection part (S202), it enters the switched state of the directional lever 4 via the P123 (S203), and it searches for the count value which is obtained by the counter 22 and it calculates the running speed V and the running acceleration G of the main chassis 1 from the desired count value (S204). The calculation of the driving speed V by the CPU 27 corresponds to a part of the speed calculation of

forklift.

  Then it is checked whether the running speed V which is calculated in step S204 is lower than the ceiling speed Vs or not (S205). If the result of the check is YES, then it can be appreciated that there is no need to put any limit on the driving speed V and therefore, normal taxi control processing is executed (S206). Then the treatment goes to a stage

  S210 which will be discussed later. And the treatment mentioned above

  before at the level of step S205 carried out by the CPU 27 corresponds to a

comparison and calculation part.

  Here, the normal taxi control processing in step S206 is a processing (S220) according to which, as shown in FIG. 3, a motor output control value in the normal rolling operation of the forklift is calculated by multiplying a given gain (coefficient) and the depressing value of the accelerator pedal. That is to say, it is a processing according to which the depressing value of the accelerator pedal 9 is detected by the accelerator pedal detecting part and the output control value of the engine. induction 14 which is proportional to the depressing value of the accelerator pedal 9 is calculated. This

  processing performed by the CPU 27 corresponds to a control part.

  On the other hand, if the verification result in step S205 is NO, then it can be appreciated that the current driving speed of the forklift is equal to or greater than the ceiling speed and that it is necessary to set a limit at the speed of travel. Therefore, it is checked whether the switched state of the directional lever 4 is a forward state or a reverse state (S207). If the verification result is the forward state, then the output control value Mf of the induction motor 14 is calculated in accordance with the above-mentioned equation of the output control value Mf of the induction motor 14 in the case of forward engine operation (S208). Otherwise, if the verification result is the reverse state, then the output control value Mb of the induction motor 14 according to the above-mentioned equation of the output control value Mb of the motor induction 14 in the case of reverse operation (S209) is calculated. This processing for calculating the output control values of the induction motor 14 carried out by the CPU 27 in the case where the running speed is equal to or greater than the ceiling speed also corresponds to the control part. And after the processing operations of steps S206, S209 have been carried out, the processing proceeds to the next step S210 at which the pulse output part PWM 28 is controlled by the CPU 27 in accordance with the output control value of the induction motor 14 which is calculated in step S206 and thus, the number of revolutions of the induction motor 14 is controlled so that the rolling speed of the forklift becomes equal to the speed which corresponds to the value d depressing the accelerator pedal

(S210).

  Furthermore, in the case of step S208, the pulse output part PWM 28 is controlled by the CPU 27 so that the output of the induction motor 14 becomes equal to Mf and in the case of step S209, the PWM pulse output portion 28 is controlled by the CPU 27 such that the output of the induction motor 14 becomes equal to Mb; and thus, the number of revolutions of the induction motor 14 is controlled so that the rolling speed of the forklift becomes equal to the value corresponding to the depressing value of the accelerator pedal (S210) and then, the

  processing returns to the above-mentioned step S202.

  Thanks to the control procedures mentioned above, even in the case where an operator applies the accelerator pedal strongly, the maximum driving speed of the forklift can be limited to the ceiling speed of for example 15 km / h which is established by the setting part 24. In this case, when the depressing value of the accelerator pedal is low and therefore the actual driving speed does not reach the ceiling speed, the induction motor

  14 is maintained in the normal operating control state.

  Furthermore, even in the case where the forklift is traveling from a flat road on a slope while the accelerator pedal is depressed, the driving speed of the forklift when it arrives on the slope may be limited to the ceiling speed , or 15 km / h. When the driving speed is limited to the ceiling speed or to a lower value as mentioned above, the induction motor 14 is maintained in the regenerative operation control state. Therefore, according to the embodiment which is mentioned above, even in the case where the forklift is traveling from a flat road on a slope while the accelerator pedal is depressed, since the rolling speed of the forklift can be limited to the ceiling speed, it is not possible that the forklift can accelerate gradually as in the conventional forklift controller, which eliminates the fear that the loads transported on board the forklift can fall and this also eliminates the need to establish an additional braking distance when braking the forklift. Thanks to this, the

  forklift can descend the slope at safety speed.

  In this context, according to the embodiment presented above

  front, at step S207 which is shown in FIG. 11, checking whether the switched state of the directional lever 4 is the forward state or the reverse state, the output command value of motor Mf in the case of forward operation and the motor output control value Mb in the case of reverse operation are calculated. However, according to a variant, at step S204, it is assessed whether the switched state of the directional lever 4 is the forward state or the reverse state from the direction of the speed derived at from the counter count value and in accordance with the result of this assessment, the engine output control value Mf in the case of forward operation and the engine output control value Mb in the

  reverse operation can be calculated.

  Furthermore, according to the embodiment mentioned above, the rolling speed of the forklift is limited to the ceiling speed or

  to a lower value established by the establishment part 24.

  However, of course, the driving speed of the forklift can also be limited to the speed which is slightly higher than

  the ceiling speed (for example the ceiling speed +1 kmlh).

  In addition, according to the embodiment mentioned above, a

  description of the case in which the ceiling speed is established according to three

  levels by establishment part 24 was presented. However, it goes without saying that the ceiling speed can also be established according to

  two levels or according to four or more levels.

  Still further, according to the embodiment presented above,

  the description of the case in which the induction motor 14 is used in

  as a power source for the forklift has been presented.

  However, even in the case of a forklift which uses a DC motor as its power source, the present invention can also be applied in a similar manner and effects which are equivalent to those obtained can also be obtained.

  level of the embodiment presented above.

  What is more, in the embodiment presented above, the

  description of the case in which the invention is applied to the carriage

  riser of a reverse braking type has been presented.

  However, the invention is not limited to the forklift truck of a type with reverse current braking. For example, the invention can also be applied to other types of forklifts including a carrier type forklift and a forklift which uses any other type of induction motor as its power source and in these cases also, it is possible to obtain the effect equivalent to that

  obtained at the level of the embodiment presented above.

  In addition, the invention is not limited to the embodiment mentioned above, but there are various variants and modifications.

  possible without departing from the scope of patent claims

attached here.

  As has been described so far, in accordance with the first aspect of the invention, when the chassis of the forklift stops in the middle of the slope, even in the case where the operator takes his foot off the accelerator pedal without applying the parking brake, the main forklift chassis is made to descend slowly along the slope at a given low speed or at a lower speed, which prevents the lowering speed of the main forklift chassis elevator does not increase gradually, and thus the operator can maintain the descent speed at a constant level. Furthermore, since the operator has the possibility of observing that the main chassis of the forklift is slowly descending, the operator can be made aware that he has forgotten to apply the parking brake; that is, the operator can be informed of his failure to apply the parking brake. This makes it possible to increase security

  at the level of the lift truck running.

  Furthermore, it is possible to prevent the battery from being exhausted during the lowering operation carried out by the main forklift chassis so that the life of the battery can

be extended.

  According to the second aspect of the invention, since the engine output control value is calculated in accordance with the speed and acceleration of the main forklift chassis when it is driving by itself by controlling the engine in accordance with the output control value thus calculated, the self-rolling speed of the main forklift chassis can be maintained at a

given low speed value.

  Furthermore, in accordance with the third aspect of the invention, the motor output control value while the direction of rotation of the motor is taken into account can be calculated as a function of the direction of the main forklift chassis which rolls through it. - even on the slope, i.e. either the forward direction or the

reverse direction.

  According to the fourth aspect of the invention, in the case where the accelerator pedal is deactivated, by considering the current speed as a target speed, the forklift truck is then authorized to drive while the speed of the forklift truck is in progress. to be maintained at the target speed or at a lower speed. Thanks to this, for example during a forward drive on a slope, in the case where an operator sets the speed of the forklift truck to a desired speed just before advancing on the slope, the forklift truck can descend the rolling slope while its speed remains unchanged; that is, in this case it can be prevented that the speed of the forklift accelerates to be faster than that which the operator expects so that the forklift is brought to

  descend by rolling the slope at an optimum speed for the operator.

  According to the fifth aspect of the invention, in the case where the accelerator pedal detection part detects the deactivated state of the accelerator pedal and o the operating mode of the forklift truck is thus switched to the neutral mode, the motor output control value is calculated in accordance with the target speed during the transition to neutral mode as well as in accordance with the speed and acceleration of the forklift which are derived by means of the bypass portion; and therefore, by controlling the induction motor in accordance with the output control value so calculated, the speed of the forklift can be maintained at the target speed when transitioning to neutral mode or less In addition, in accordance with the sixth aspect of the invention, the motor output control value while the direction of rotation of the motor is taken into account can be calculated as a function of the direction of travel of the chassis of the forklift, that is to say as a function of if the main forklift chassis is

to move forward or backward.

  In accordance with the seventh aspect of the invention, at the speed of travel of the lift truck up to its ceiling speed, the lift truck is caused to roll by means of an acceleration which corresponds to the depressing value of the accelerator pedal and when the driving speed of the forklift exceeds the ceiling speed, the driving speed may be limited to the ceiling speed or less. Thanks to this, during the normal rolling operation of the forklift, not only the rolling operation of the forklift can be controlled by means of a driving sensation which is such as that which can be obtained when driving an automobile but also moreover, in the case where the rolling speed of the forklift becomes greater than the ceiling speed, for example when the forklift is traveling down a slope, the rolling speed may be limited to the ceiling speed or less, which allows thus to exercise a rolling control which is such that it allows

  ensure the safety of the lift truck.

  Furthermore, in accordance with the eighth aspect of the invention, in addition to the effects which are obtained by means of the first aspect of the invention mentioned above, the driving speed of the forklift can be limited to the ceiling speed or less independently activation and deactivation states of the accelerator pedal. Therefore, even in the case where an operator takes his foot off the accelerator pedal on a slope, the rolling speed of the forklift can be limited to the ceiling speed or less, which allows the operator to relax. or take your foot off the accelerator pedal on a slope similar to when the operator drives a car. Consequently, not only can the operator drive the forklift with the same driving sensation as when the operator drives an automobile, but also the rolling speed of the forklift can be limited, i.e. safety of the forklift as well as that of the operator can be increased. Furthermore, in accordance with the ninth aspect of the invention, the driving speed of the forklift truck can be limited to the ceiling speed or less independently of the activation and deactivation states of the accelerator pedal. Thanks to this, even in the case where the operator takes off his foot which is held on the accelerator pedal on a slope, the driving speed of the forklift can be limited to the ceiling speed or less. Consequently, not only can the operator drive the forklift with the same driving sensation as that obtained by the operator when driving an automobile, i.e. the operator can remove or remove his foot of the accelerator pedal on the slope but in addition, the rolling speed of the forklift may be limited, that is to say the safety of the forklift as well

  than that of the operator can be increased.

  Furthermore, in accordance with the tenth aspect of the invention, since the motor output control value is calculated in accordance with the speed and acceleration of the forklift while it is moving, controlling the motor in accordance with the value of motor output command calculated in this way, the auto-rolling speed of the carriage

  elevator can be limited to an established value or less.

  Still further, in accordance with the eleventh aspect of the invention, depending on whether the forklift is traveling in a forward direction or a reverse direction, the engine output command value while the direction of rotation of the engine is taken into account is calculated; and the rolling speed of the forklift may be limited to the ceiling speed or less which is established by the setting part at once in the direction of travel

  before and in the reverse direction.

  Furthermore, in accordance with the twelfth aspect of the invention, a control signal from the inverter which arrives on the induction motor can be controlled so that the output control value of the motor can become the control value output calculated by the control part. Thanks to this, on a flat road, the induction motor can be controlled so as to implement normal operation and on a slope, the induction motor can be controlled so as to implement regenerative operation, which makes possible to limit speed

  of the lift truck traveling at ceiling speed or less.

Claims (12)

  1. Forklift control apparatus in which a continuous power output from a battery (2) mounted on a main forklift chassis (1) is converted into alternating power by an inverter (13) to be applied to a induction motor (14); and in which the induction motor is controlled by a control portion of the forklift so as to implement normal operation or regenerative operation of the main chassis of the forklift (1), characterized in that: after the chassis main forklift (1) stops, an induction motor output control value (14) which uses a differentiation and proportionality control is calculated according to a speed and acceleration of the main forklift chassis ( 1) when the main forklift chassis is running while an accelerator pedal (9) is not depressed in order to   maintain the speed at a predetermined value or less.   2. Forklift control apparatus according to claim 1, characterized in that it comprises: a rotation detection part (22) for detecting the number of revolutions of the induction motor (14); a drift part for deriving the speed and acceleration of the main forklift chassis (1) from a detected value which is obtained by the rotation detection part; a switching part for switching and establishing a transmission for transmitting the driving force of the induction motor (14) to a wheel of the main forklift chassis (1) in either a forward or a reverse state, either a neutral state; an accelerator pedal detecting portion for detecting whether an accelerator pedal (9) is in the activated state or in the deactivated state; and a control part which, subject to the condition that, when the rotation detection part (22) detects that the main forklift chassis (1) stops, that the switching part is established in the neutral state and the deactivation state of the accelerator pedal (9) is detected by the accelerator pedal detecting part, calculates the output command value of the induction motor (14) using the command of differentiation and proportionality according to the speed and acceleration of the main forklift chassis (1) when the forklift chassis is running in order to maintain the speed at a predetermined low value or less. 3. Forklift control apparatus according to claim 2, characterized in that the control part calculates the output control value in the forward direction and the output control value in the reverse direction, so respective, according to the directions of the speed derived by the drift part.   4. Forklift control apparatus in which a continuous power output from a battery (2) mounted on a main forklift chassis (1) is converted into alternating power by an inverter (13) to be applied to a induction motor (14); and in which the induction motor is controlled by a control portion of the lift truck so as to implement normal operation or regenerative operation of the main lift truck chassis (1), characterized in that: when a pedal accelerator (9) is no longer pressed by an operator during the running operation of the lift truck and the lift truck is thus switched to a neutral mode and that the speed of the lift truck during the transition to the neutral mode in as long as the target speed reaches or exceeds the target speed, the output control value of the induction motor (14), using a differentiation and proportionality control, is calculated in accordance with the target speed as well as in accordance with a speed and acceleration of the forklift in order to be able to maintain target speed.   5. Forklift control apparatus according to claim 4, characterized in that it comprises: a rotation detection part (22) for detecting the number of revolutions of the induction motor (14); a drift part for deriving the speed and acceleration of the forklift (1) from a detected value which is obtained by the rotation detection part; an accelerator pedal detecting portion for detecting whether an accelerator pedal (9) is in the activated state or in the deactivated state; and a control part for switching the lift truck to a neutral mode when the un depressed state of the accelerator is detected by the accelerator detection part, for establishing the speed of the lift truck during the transition to the neutral mode as a target speed and to calculate the output control value of the induction motor (14) using the differentiation and proportionality control in accordance with the target speed as well as in accordance with the speed and acceleration of the forklift derived by the drift portion to maintain the target speed when   the forklift speed reaches or exceeds the target speed.   6. Forklift control apparatus according to claim 5, characterized in that the control part calculates the output control value in the forward direction and the output control value in the reverse direction, so respective, according to the directions of the speed derived by the drift part.   7. Forklift control apparatus for controlling a driving engine by means of a power which is applied from a battery (2) which is mounted on a main forklift chassis (1), the control apparatus for forklift being characterized in that it comprises: an accelerator pedal detecting part for detecting the depressing value of an accelerator pedal (9); a forklift speed sensor for detecting a forklift speed value corresponding to the driving speed of the main forklift chassis (1); a forklift speed calculating part for calculating a driving speed of the main forklift chassis (1) from the forklift speed value which is obtained by the forklift speed sensor; a setting part for establishing the maximum speed of the main forklift chassis; a comparison and calculation part for comparing and calculating the driving speed which is obtained by the forklift speed calculating part and the maximum speed established by the setting part; and a control part which, as a result of the comparison which is carried out in the comparison and calculation part, when the running speed is equal to or less than the maximum speed, calculates an engine output control value for providing the main forklift chassis with acceleration which is proportional to the depressing value of the accelerator pedal (9) which is obtained by the accelerator pedal detecting part and when the driving speed exceeds the maximum speed , calculates a motor output command value to limit the speed of   driving at maximum speed or less.   8. Forklift control apparatus for driving a rolling engine by means of a power which is applied from a battery (2) which is mounted on a main chassis of a forklift (1), the control apparatus forklift truck being characterized in that it comprises: an accelerator pedal detection part for detecting the activation / deactivation states of an accelerator pedal (9) and the corresponding depressing value; a forklift speed sensor for detecting a forklift speed value corresponding to the driving speed of the main forklift chassis (1); a forklift speed calculating part for calculating a driving speed of the main forklift chassis (1) from the forklift speed value which is obtained by the forklift speed sensor; a setting part for establishing the maximum speed of the main forklift chassis; a comparison and calculation part for comparing and calculating the driving speed which is obtained by the forklift speed calculating part and the maximum speed established by the setting part; and a control part which, as a result of the comparison which is carried out in the comparison and calculation part, when the running speed is equal to or less than the maximum speed, calculates an engine output control value for providing the main forklift chassis with an acceleration which is proportional to the depressing value of the accelerator pedal (9) which is obtained by the accelerator pedal detection part and when the driving speed exceeds the maximum speed , calculates a motor output command value to limit driving speed to maximum speed or less regardless of the states   activation / deactivation of the accelerator pedal.   9. Forklift control apparatus for driving a driving engine by means of a power which is applied from a battery (2) which is mounted on a main chassis of a forklift (1), the control apparatus for forklift being characterized in that it comprises: an accelerator pedal detection part for detecting the activation / deactivation states of an accelerator pedal (9) and the corresponding depressing value; a forklift speed sensor for detecting a forklift speed value corresponding to the driving speed of the main forklift chassis (1); a forklift speed calculating part for calculating a driving speed of the main forklift chassis (1) from the forklift speed value which is obtained by the forklift speed sensor; a setting part for establishing the maximum speed of the main forklift chassis; a comparison and calculation part for comparing and calculating the driving speed which is obtained by the forklift speed calculating part and the maximum speed established by the setting part; and a control part which, as a result of the comparison which is carried out in the comparison and calculation part, when the driving speed exceeds the maximum speed, calculates an engine output control value to limit the speed of driving at maximum speed or less regardless of conditions   activation / deactivation of the accelerator pedal.   10. Forklift control apparatus according to one   any one of claims 7, 8 and 9, characterized in that it   further comprises: a rotation detection part (22) for detecting the number of revolutions of the rolling motor (14); and a drift part for deriving the speed and acceleration of the main forklift chassis (1) from a detected value which is obtained by the rotation detection part, where the control part derives the speed and l acceleration of the main forklift chassis (1) from the number of engine revolutions obtained by the rotation detection part and in accordance with the derived speed and acceleration, calculates the output command value. 11. Forklift control apparatus according to one   any one of claims 7, 8, 9 and 10, characterized in that it   further comprises: a switching part for switching and establishing a transmission for transmitting the driving force of the running motor (14) to a wheel in either a forward state, a reverse state, or a neutral state, the control part, in accordance with the switched states of the transmission by the switching part, calculates the output command value for a forward direction and the output command value for a reverse direction, respectively. 12. Forklift control apparatus according to one   any of claims 7, 8, 9, 10 and 11, characterized in that the   driving motor comprises an induction motor (14) and the continuous output power of the battery (2) is converted into alternating power by an inverter to be applied to the induction motor.