JPS6323440Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an automatic cargo handling forklift truck using a microcomputer.

FIG. 1 is an overall overview diagram showing an example of a forklift truck to which the present invention is applied, and in the figure, reference numeral 1 denotes a pair of left and right masts that are attached to the front of a forklift truck 2 so as to be able to tilt by a certain amount. It is. The mast 1 is composed of an outer mast and an inner mast that is raised and lowered along the outer mast. The inner mast can be moved up and down by the operation of the lift cylinder 6. Also 3
is a fork moored to a lifting member 4 that is raised and lowered along the mast 1, and 3a is the tip of the fork's horizontal portion 3b. Reference numeral 6 denotes a lift cylinder, and its operation causes the elevating member 4 to move up and down via the chain 5. A chain wheel support is fixed to the upper end of the piston 6a housed in the lift cylinder 6, and a chain wheel 10 is mounted on both sides of this chain wheel support.
is provided. As the chain 5 moves, the elevating member 4 is guided by the inner mast and slides upward and downward. Reference numeral 7 denotes a tail cylinder, which is operated by a tail control valve controlled by a tail servo (not shown), for example, to tilt the mast 1 forward or backward. 8 is the front wheel, 9
is a rear wheel, and 11 is a load (cargo) loaded on the fork horizontal portion 3b.

In a forklift truck with such a configuration, the automatic lifting operation of a forklift truck using a microcomputer with a built-in program control function for automatic lifting operation will be summarized using Fig. 2. do.

In FIG. 2, a microcomputer 22 is supplied with a pulse output (displacement pulse) from a lifting height sensor 21 for detecting the height of the fork and the cargo handling speed. Here, as the lift height sensor 21, for example, a pulse generator is linked via a gear etc. to the chain wheel 10 that moves as the fork 3 moves up and down, and a pulse output (displacement pulse) is sent out every time the chain wheel 10 moves forward. The height of the fork and the cargo handling speed are detected based on the number of pulses and repetition frequency of this pulse output. Therefore, when the above-mentioned pulse output of the lifting height sensor 21 is supplied to the microcomputer 22, the height of the fork and the cargo handling speed are calculated and detected based on the pulse number and repetition frequency based on this pulse output.

The microcomputer 22 has a built-in program control function for automatic lifting operation, and when the automatic lifting start button switch 22b provided on the microcomputer 22 is pressed, the control section 22a of the microcomputer 22 starts the automatic lifting operation. A control signal is supplied to the servo valve opening command section 23 according to the lift height operation program. The servo valve opening command section 23 is controlled by the microcomputer control section 22.
Based on the control command from a, a servo valve opening command signal is supplied to the bases of transistors 24a, 24b or 24c, 24d constituting the servo motor drive unit 24 to turn on and off the transistors and drive the servo motor 25. Control. 24e is a DC power supply. The lift valve 27 is controlled by the operation of the clutch 26 in conjunction with the servo motor 25, and the hydraulic pressure supplied from the hydraulic pump 28 to the lift cylinder 6 is controlled. The lift cylinder 6 moves the fork up and down in response to the up and down movement of the piston 6a. Based on the pulse output supplied from the lifting height sensor 21, the microcomputer 22 detects the height of the fork and the cargo handling speed, and based on these, the microcomputer 22 executes automatic lifting height program control.

However, conventionally, in an automatic cargo handling forklift truck using a microcomputer, when a certain target height position is specified and automatic lifting operation is started, a sensor for detecting the height (position) of the fork 3 is used, for example. If the lift height sensor 21 is abnormal, no information will be received even if loading or unloading operation is actually being performed, so even if the fork 3 reaches the target height, it will continue to go too far and eventually The fork runs out of control until it is mechanically locked at the upper or lower limit, causing the load 11 to fall or be damaged.
Also, when unloading, if you accidentally start the automatic lowering operation without noticing that the fork claw tip (tip) 3a is caught on the shelf where the cargo is stored, the mast 1 will lower, but the fork This was very dangerous as the chain 5 could not be lowered due to the shelf, the cargo 11 could tilt and fall, and the forklift truck itself could overturn.

Therefore, in order to solve these conventional problems, the present invention further aims to solve the problem when the signal from the lifting height sensor is not received within a certain time during automatic lifting operation, or when the automatic lifting operation is commanded to descend or ascend. However, the aim is to provide an automatic cargo handling forklift truck that sends out an abnormal output signal when a reverse rising or descending signal is received from a sensor, and issues a warning and automatically stops lifting operation. ,
This will be explained below using examples.

FIG. 3 shows an embodiment of an abnormality detection circuit in an automatic cargo handling forklift truck according to the present invention, in which I ₁ is an input terminal to which a pulse output is supplied from, for example, the lifting height sensor 21 of FIG. 2, and I ₂
is an input terminal to which an automatic lifting operation command signal (for example, power output +E ₁ ) issued by pressing a button switch 22b provided on the microcomputer 22 is supplied. PWL is a pulse width expansion circuit for expanding the pulse width supplied to input terminal _I1 , and this pulse width expansion circuit PWL connects resistors _R8 to
It consists of R ₁₀ , diode D ₂ , NAND circuit NAND ₁ , inverters IN ₁ and IN ₂ , and capacitor C ₂ . Tr ₁ and Tr ₂ are transistors, R ₁ to R ₇ , R ₁₁
is a resistor, D ₁ is a diode, C ₁ is a capacitor, CP
is a comparator, and a set voltage is applied to the negative terminal of comparator CP, and a capacitor is connected to the positive terminal.
The terminal voltage of _C1 is applied.
Therefore, the comparator CP sends out an abnormal output when the voltage input to the positive terminal (the terminal voltage of the capacitor _C1 ) exceeds the set voltage applied to the negative terminal. Note that + _E1 is a power supply.

To explain the operation, first, when the automatic lift start button switch 22b shown in FIG. The lift operation starts, but on the other hand, the automatic lift operation command signal (for example, power supply + E ₁ )
is applied to input terminal I ₂ and starts charging capacitor C ₁ . However, when automatic lifting operation starts, the pulse output from the lifting height sensor 21 shown in Fig. 2 is sent to the input terminal.
When supplied to I ₁ , the pulse width is expanded by the pulse width expansion circuit PWL and supplied to the base of transistor Tr ₁ , and this pulse causes the transistor to
Tr ₁ turns on, then Tr ₂ turns on, and the capacitor
Since both ends of C ₁ are almost short-circuited, the charge stored in capacitor C ₁ is discharged in the closed loop of capacitor C ₁ - resistor R ₅ - transistor Tr ₂ - capacitor C ₁ . When the transistor Tr ₁ is turned off until the next pulse input comes, the transistor Tr ₂ is also turned off and the capacitor C ₁ is charged again. And the next pulse is the transistor Tr _1
When supplied _to
The charge on capacitor _C1 is discharged. Therefore, for example, while pulses are constantly being sent from the lift height sensor 21, the terminal voltage of the capacitor _C1 is the same as the comparator CP.
does not reach the set voltage. However, the lift height sensor 21
If the pulse output is not received by the microcomputer 22, etc. due to damage or poor wiring contact, the pulse output is not supplied to the input terminal _I1 , and therefore the transistors _Tr1 and _Tr2 remain off. After a certain period of time (for example, 3 seconds), the terminal voltage of the capacitor _C1 , that is, the voltage applied to the positive terminal of the comparator CP, reaches the set voltage due to charging, and the comparator CP detects damage to the lift height sensor 21 or its wiring. Detects an abnormality such as a poor contact, and sends out an abnormal output signal. In this way, for example, when the pulse output from the lift height sensor 21 does not come at all for a certain period of time (for example, 3 seconds), the abnormality detection circuit in FIG. 3, that is, the comparator CP sends out the abnormal output signal. It issues a warning to the driver using a signal or lights up a warning light to warn the driver and also stops the automatic lifting operation.

In this case, the abnormality detection circuit shown in FIG. 3 may be incorporated into the microcomputer 22 shown in FIG. 2 or may be provided separately, and the abnormality detection circuit shown in FIG. A hardware configuration for extracting an abnormal output signal using the abnormality detection circuit shown in FIG. 3 can also be incorporated into the microcomputer 22 using software.

FIG. 4 shows another embodiment of the abnormality detection circuit for an automatic cargo handling forklift truck according to the present invention, in which case the abnormality detection circuit ADC of FIG. 3 is also included.

In FIG. 4, UDD is a rise/fall discrimination circuit for discriminating whether the lift is actually rising or falling during the automatic lift operation described above. For example, the lift sensor 21 in FIG. 2 detects whether the lift is rising or falling (for example, forward rotation in the case of the chain wheel 10 in FIG. 1,
Based on the two-phase signal (A-phase signal for up, B-phase signal for down) supplied (corresponding to whether the direction is reversed), the up/down discrimination circuit UDD discriminates whether the movement is in the up or down direction, and if it discriminates in the up direction, it sends a logic "1" output from the UP terminal to the AND circuit AND ₂ , and if it discriminates in the down direction, it sends a logic "1" output from the DOWN terminal to the AND circuit AND ₁ .
The direction of ascent or descent is determined based on the output of the AND circuit AND1, but the present invention is not limited to this. The direction of movement of the fork or the direction of movement of the mast or chain may be detected by a sensor, and the sensor output may be input to the ascent/descent determination circuit UDD to determine the direction of ascent or descent. A logic "1" output is supplied to the other input terminal _I3 of the AND circuit _AND1 when an ascent command is issued during automatic lifting operation, and a logic "1" output is supplied to the other input terminal _I4 of the AND circuit _AND2 when a descent command is issued during automatic lifting operation. Therefore, the AND circuit _AND1
Even if a command to raise the height is issued in the automatic raising operation, when information (actual operation) obtained from a sensor, for example, the height sensor 21, indicates a lowering operation, a logic "1" is input to the AND circuit _AND1 , so that the AND circuit AND1 outputs a logic "1" (abnormal output) from the output terminal _O1 via the OR circuit OR.
A logic "1" is input to AND ₂ when the information (actual operation) obtained from a sensor, such as the lift height sensor 21, indicates an upward movement even though a downward command is issued in the automatic lift operation. Therefore, the AND circuit AND ₂
sends out a logic "1" output from the output terminal _O1 via the OR circuit OR. Also, the abnormal output signal (logic "1") detected by the abnormality detection circuit ADC of FIG. ₃ is taken out from the output terminal _O1 via the OR circuit _OR .
If a logic "1" output (abnormal output signal) is sent from any of the abnormality detection circuits ADC in FIG. 3, it will be taken out from the output terminal _O1 via the OR circuit OR.

Using the abnormal output signal taken out from the output terminal _O1 , it is possible to issue a warning to the driver or turn on a warning light to warn the driver and to stop the automatic lifting operation.

The circuit shown in FIG. 4 may be incorporated into the microcomputer 22 shown in FIG. 2 or may be provided separately, and the circuit shown in FIG. The hardware configuration for extracting the abnormal output signal from the circuit shown in the figure is implemented by microcomputer 2.
2 can be combined with software.

By using the present invention described above, the following various effects can be achieved.

(1) If the output pulse is not received due to damage to a sensor such as a lift height sensor or a poor connection in its wiring, a warning is issued and automatic operation is stopped, preventing runaway cargo handling.

(2) When the fork gets stuck on a shelf or otherwise does not move, no pulse is generated from the sensor (such as a sensor that detects whether the fork is rising or falling), so a warning or automatic operation stop is also issued, preventing the occurrence of an accident. It can be prevented.

(3) When the fork fails to catch on a shelf etc., the chain becomes loose even though it is descending, and if an encoder connected to the chain wheel is used as a sensor (such as a sensor that detects whether the fork is ascending or descending), the ascending side It may rotate, but
At that time, a pulse is generated, albeit in the opposite direction for a while. Therefore, in this case, in the example, the third
Although the abnormal output is not taken out from the ADC circuit in the figure, according to the circuit in Figure 4, the abnormality is detected by the AND circuit AND ₂ and the abnormal output signal is taken out through the OR circuit OR, so a warning or warning is issued before the chain is disconnected. Automatic driving will be stopped, preventing accidents from occurring.

[Brief explanation of the drawing]

Fig. 1 is an overview of a forklift truck to which the present invention is applied, Fig. 2 is a configuration diagram of the main parts of the present invention for program control of automatic lifting operation using a microcomputer, and Fig. 3 is a schematic diagram of a forklift truck to which the present invention is applied. A circuit diagram showing one embodiment of the abnormality detection circuit in the automatic cargo handling forklift truck according to the present invention, FIG. 4 is a circuit diagram showing another embodiment of the abnormality detection circuit in the automatic cargo handling forklift truck according to the present invention, In the diagram, 1 is the mast, 2 is the forklift truck, 3 is the fork, 3a is the fork toe, 3
b is a fork horizontal part, 5 is a chain, 6 is a shift cylinder, 10 is a chain wheel, 11 is a load (load), 21 is a lift height sensor, 22 is a microcomputer, 22a is a microcomputer control unit, 22b is an automatic lift High start button switch,
23 is a servo valve opening command unit, 24 is a servo motor drive unit, 25 is a servo motor, 26 is a clutch, 27 is a lift valve, 28 is a hydraulic pump,
ADC is an abnormality detection circuit, AND ₁ and AND ₂ are AND circuits, UDD is a rise/fall discrimination circuit, OR is an OR circuit, and I ₁ to I ₄ are input terminals.

Claims (1)

[Scope of utility model registration request] A microcomputer inputs the pulse output from the lifting height sensor to detect the height of the fork and the cargo handling speed, and sends out a control signal for automatic lifting operation, and the servo valve opening is determined based on the control signal from this microcomputer. A servo valve opening command section that issues a command signal, a servo motor drive section that drives a servo motor under the control of the servo valve opening command signal from this servo valve opening command section, and a servo motor drive section that operates in conjunction with the servo motor. It has a clutch that operates, a lift valve that is controlled by the operation of this clutch, and a lift cylinder that is hydraulically controlled by this lift valve to move the fork up and down, and moves the fork up and down based on the output of the microcomputer. In the automatic cargo handling forklift truck which is operated by moving the vehicle to perform automatic lifting operation, the automatic cargo handling forklift truck is equipped with a comparator that sends out an abnormal output when a signal from the lifting height sensor is not received within a certain period of time during automatic lifting operation. An abnormality detection circuit, a lift operation rise/decrease determination circuit which is supplied with the output signal of the lift height sensor and determines whether the lift height is rising or falling based on this signal; A first AND circuit which sends out an abnormal output when the command is supplied to one input terminal and the lowering discrimination output from the discrimination circuit is supplied to the other input terminal and the AND condition of both input terminals is satisfied; When a descending command is issued, this descending command is supplied to one input terminal, and the rising discrimination output from the discrimination circuit is supplied to the other input terminal, and when the AND condition of both input terminals is satisfied, an abnormal output is generated. a second AND circuit that sends out an output; and an OR circuit that is supplied with the output of the abnormality detection circuit and the outputs of the first and second AND circuits and that sends out an abnormal output when any one of these circuits receives an output. Automatic cargo handling forklift truck.