Control system for industrial use vehicles

Abstract: A control system for industrial use vehicles comprising travel signal input means (7) for inputting an output signal of an accelerator for travel, cargo-handling signal means (8,9,10) for inputting a cargo-handling signal, monitor voltage input means (11) for detecting a voltage at each monitor point and inputting a detected signal, sensor input means (12) for inputting an output signal of each sensor, monitor input means (13) for inputting an output signal of each monitor, and a microprocessor controller (14) for receiving the output signals of the respective means and outputting predetermined control signals.

Description: The present invention relates to a control system for industrial use vehicles (hereinafter referred to as a battery driven fork-lift truck) of the type in which when an abnormality is found in the controls of travel, cargo-handling, and electric power steering, the control for preventing interference among the controls, and travel, cargo-handling, steering, battery liquid level, and the like, a trouble location is displayed on a display screen, under a synthetic control of a microcomputer. Such a control system as indicated in the precharacterizing part of claim 1 is disclosed in US-A-4 547 844. In a conventional control technique, individual control units are provided for the travel, the cargo-handling and the power steering, respectively. To effect the interference preventive control for preventing interference among the controls of the travel, cargo-handling, steering, and the controls relating to the monitor display control, the prior control technique requires an increased number of sensors, and terminals for signal transmission/reception. Further, those controls are interconnected by different control units. Accordingly, a control system for effecting such controls based on the prior control technique is complicated in construction, and inherently involves the following problems. 1) Since the individual control units are installed, it is difficult to prevent the interference among the respective controls, and the combination of them for monitoring is intricated. 2) When the travel and the cargo-handling are concurrently performed, a large current flows and hence a battery voltage drops. This results in insufficient motor power and instable control. 3) At the time of braking, although a braking power results from a plugging, kinetic energy can not be returned to electric energy. In this respect, poor energy saving can be attained. The large current flow through the motor causes great weariness of the brush and the commutator. Where for solving the problem, regeneration is used, an automatic regenerative/power travel check system of a very high response or a high operation feeling is required. 4) A number of contacts to open and close circuits are used. Full power is used for exciting the contacts. After the contacts are attracted, the energy saving can not be expected. Because of a large amount of heat generated, the contact size is large and consumes large spaces. This is problematic when the components are mounted. 5) Because of individual control units for the control of the battery driven fork-lift truck and the monitor control for checking whether or not parts are normal for maintenance, it is impossible to synthetically monitor. Further, there is no display to provide detailed monitor data and easy-to-understanding of the monitor data. It is the object of the invention to provide a control system for industrial use vehicles in which a simple regenerative/power travel check system for energy saving can be used. According to the present invention this object is solved by the features as claimed in claim 1. In the control system for industrial use vehicles, when receiving the output signals of the travel signal input means and the cargo-handling signal input means, the microprocessor controller sets a reference time point in a fixed period generated therein at an OFF point of one of the travel signal or the cargo-handling signal, and sets at an ON point of the other. In the control system for industrial use vehicles, the microprocessor controller receives an output signal of the travel signal input means, and checks whether or not a plugging current exceeds a preset value within a predetermined period when a travel chopper starts to operate, and produces a control signal to select a regenerative braking mode when the plugging current exceeds the preset value. Further, in the control system for industrial use vehicles, the microprocessor controller receives a voltage of a battery contained in the monitor voltage input means, and produces a control signal to apply a fixed average exciting voltage to an exciting coil of each contact even if a battery voltage varies. Other objects, features and advantages of the present invention will be apparent from the following description taken connection with the accompanying drawings, in which: Fig. 1 shows a side view of a battery driven fork-lift truck incorporating a control system according to the present invention; Fig. 2 shows a block diagram of a control system used in the fork-lift truck of Fig. 1; Fig. 3 is a circuit diagram showing the details of a control section in the control system of Fig. 2; Fig. 4 shows a timing diagram useful in explaining an operation of the fork-lift truck when a travel operation and a cargo-handling operation are concurrently performed; Fig. 5 shows a timing diagram useful in explaining an operation of a conventional fork-lift truck when a travel operation and a cargo-handling operation are concurrently performed; Fig. 6 is a circuit diagram formed when a power travel mode is switched to a regenerative mode; Fig. 7 is a timing chart useful in explaining the mode switching operation of Fig. 6; Figs. 8 and 9 are circuit diagrams of contact choppers; Fig. 10 shows a front view of a display panel in which a display window displays a normal state of the fork-lift; and Fig. 11 shows a front view of a display panel in which a display window displays an abnormal statement. A preferred embodiment of a control system for industrial use vehicles according to the present invention will be described with reference to Figs. 1 through 11. Fig. 1 shows a side view of a battery driven fork-lift truck incorporating the control system according to the present invention. In the figure, reference numeral 1 designates a vehicle body; 2, a fork for cargo-handling, which is lifted by oil pressure; 3, a drive wheel; 4, a load wheel; 5, a steer handle, 6, a display panel for displaying monitor data and defective parts data, and the like; BA indicates a battery. Although not illustrated, a circuit board including a travel main circuit, a cargo-handling main circuit, a power steering main circuit, and a control circuit containing a microprocessor (MPU) to be given later, and various types of sensors are mounted on the vehicle body 1. Fig. 2 shows a block diagram of a control system used in the fork-lift truck of Fig. 1. In the figure, a travel signal input means 7 is arranged so as to control a travel speed in accordance with a tilt angle of an accelerator (referred to as a travel lever), which is located near a driver seat on the upper side of the body 1. Cargo-handling signal input means 8, 9 and 10 are constructed with a plurality of cargo-handling operation levers located near the driver seat on the upper side of the body 1. The means 8 is a lift lever for lift operation; the means 9, a reach lever for reach operation; the means 10, a tilt lever for tilt operation. The operation of lift, reach and tilt may be exercised by manually operating those levers. Reference numeral 11 designates a monitor voltage input means; 12, sensor input means; 13, monitor input means; 14 a MPC controller which receives the output signals of the above means and produces given control signals; 15, a contactor system containing a group of contactors, such as a travel system contactor, a cargo-handling contactor, and a power steering contactor. The contactor system 15 operates under control of control signals outputted from the MPU controller 14. Reference numeral 16 designates a travel main circuit; 17, a cargo-handling main circuit; 18, a power steering main circuit. Fig. 3 is a circuit diagram showing the details of a control section in the control system of Fig. 2. The travel main circuit 16 is arranged as described below. In the figure, reference numeral 16A designates an armature of a travel motor; Mg, a contact of a regenerative/power travel select contactor; 16W, a field winding for the motor; Mf and Mr, contacts of a forward contactor and a reverse selector contactor by which the polarity of the field winding 16W is changed; 16CH, a switching element for controlling a duty of a current fed to the motor in a regenerative mode and a power travel mode. Those components are coupled with a battery BA. A plugging diode Dp allows a plugging current Ip to flow to the armature 16A only when the motor is reversely turned. A plugging current detect resistor Rp detects an amplitude of the plugging current Ip. An armature current detect resistor Ra is connected in series to the armature 16A, and detects an amplitude of the plugging current Ip. A regenerative diode Dg allows a regenerative current in a regenerative mode. Mb represents a contact of a by-pass contactor. The cargo-handling main circuit 17 is arranged as described below. Numeral reference 17A designates an armature of a cargo- handling hydraulic motor (hereinafter referred to as a hydraulic motor); 17B, a field winding of the hydraulic motor; 17CH, a cargo- handling switching element which is driven by a control signal from the MPU controller 14 through microswitches Sl, Sre, and St that are operated by tilting the cargo-handling lever. Those components are connected in series. Mpb stands for a contact of the cargo-handling by-pass contactor, which is connected in parallel to the cargo-handling switching element 17CH. The power steering main circuit 18 is arranged as described below. Mts designates a contact of a contactor, which is operated by a power steering control signal outputted from the MPU controller 14; 18C, a power steering control circuit. An exciting circuit for the contactor will be described in detail. When a key switch KS is operated, the exciting circuit for the contractor is ready for operation. Sf designates a forward microswitch operated when the travel lever 7 is tilted to a forward position; Sr a reverse microswitch operated when the lever 7 is tilted toward a reverse position. When the lever 7 is tilted toward the forward position, the switch Sf operates to send a signal to the MPU controller 14. In turn, the controller 14 produces an output signal, which in turn is applied to the base Q1 of a travel transistor PT1. Then, the transistor PT1 energizes an exciting coil MF of the forward contactor, that is connected in series to the forward microswitch Sf. Then, the fork-lift truck starts to travel forwardly. When the lever 7 is tilted toward the reverse position, the switch Sr operates to send a signal to the MPU controller 14. In turn, the controller 14 produces an output signal, which in turn is applied to the base Q1 of the travel transistor PT1. Then, the transistor PT1 energizes an exciting coil MR of the reverse contactor, that is connected in series to the forward microswitch Sr. Then, the fork-lift truck starts to travel reversely. When the lever 7 is turned to the full, the by-pass microswitch Sb operates. Then, this switch sends a signal to the MPU controller 14. An output signal of the controller 14 is applied to the base Q2 of the by-pass transistor PT2. In turn, the transistor PT2 energizes an exciting coil MB of the by-pass contactor, that is connected in series to the by-pass microswitch Sb. Then, a by-pass travel of the fork-lift truck starts. MG designates an exciting coil of the regenerative/power travel select contactor. When the lever 7 is turned to one side, an output signal of the controller 14 is applied to the base Q3 of the regenerative/power travel select transistor PT3. Then, a circuit to exercise a power travel operates. When the plugging current Ip exceeds a preset value within a period from the start of a power travel, the controller 14 stops a control signal to be applied to the base Q3 of the transistor PT3. This will be described in detail later. Accordingly, the transistor TP3 is turned off. An exciting current flowing into the exciting coil MG stops. A contact Mg of the regenerative/power travel select contactor is open. The present operation of the fork-lift truck shifts to a regenerative mode. S1 denotes a lift microswitch operated when the lift lever 8 is tilted; Sre, a reach microswitch operated when the reach lever 9 is tilted; St, a tilt microswitch operated when the tilt lever 10 is tilted. Those components are connected in parallel to a reverse current block diode D. An exciting coil MP of the cargo-handling contactor is connected in series to a cargo transistor PT4. When the lift lever 8 is tilted, the lift microswitch S1 operates to send a signal to the MPU controller 14. The controller in turn sends a signal to the base Q4 of the transistor PT4. Then, the exciting coil MP is energized. A cargo bypass microswitch S1h is not operated until the lift lever 8 is turned fully. When the lever 8 is turned so, the microswitch S1h operates to send a signal to the controller 14. Then, the controller 14 sends a signal to the base Q5 of the cargo bypass transistor PT5. The transistor energizes the exciting coil MPB. A contact Mpb of a cargo bypass contactor operates to short the cargo switching element 17CH. A power steering auxiliary circuit is arranged as described below. An exciting coil MST of a power steering control contactor is connected in series to a power steering transistor PT6. A signal, which is outputted from a power steering sensor 20 when a steering handle 5 is operated, is inputted to the MPU controller 14. The controller sends a signal to the base Q6 of the transistor PT6. Then, a contact Mst of the power steering control contactor is closed. The power steering control circuit 18C starts to operate. The sensor input means contains a power steering sensor 20, a battery voltage sensor 21, a battery liquid level sensor 22, an oil float sensor 23, and a hydraulic sensor 24. The sensor detects a tilt angle of the travel lever 7. A travel accelerator angle data means 25, which controls a travel speed of the truck in response to the output signal of the sensor, is connected as an input means to the controller 14. The MPU controller 14 receives the output signals of the various types of sensors, and the operating signals from the various types of input means, and produces individually contact operation signals (Q1 to Q6), a travel chopper gate signal (G1), a cargo chopper gate signal (G2), a power steering chopper gate signal (G3), and monitor display signals or produces concurrently some of those signals. An operation of the fork-lift truck when a travel operation and a cargo-handling operation (cargo-handling operation depends mainly on the hydraulic operation, and hence it will be referred to an hydraulic control), concurrently progress, and ON pulses G1 and G2 do not overlap, will be described with reference to Fig. 4. As a vehicle for comparison, a corresponding operation of a conventional system is illustrated in Fig. 5. As shown in a timing chart of Fig. 4, a pulse width modulation (PWM) system is employed in which the ON pulses G1 and G2 are synchronized with each other, with a fixed period (4ms, in this instance). An OFF point of a travel control pulse is positioned at a reference time point "to" in the fixed period, , while an ON point of the hydraulic control pulse is positioned. Accordingly, an ON point of the travel control pulse is located before the reference time point "to", and an OFF point of the oil pressure control pulse is located after the time point "to". At this time, a travel motor current, an oil pressure motor current, a battery current, and a battery voltage are as shown in Fig. 2. When a large current is consumed, for example, when the fork-lift starts up, a current control operates to limit the width of each ON pulse so as to prevent the ON periods of the pulses from overlapping. In a stationary state, the currents of both the travel motor and the hydraulic motor settles down to be small. Accordingly, the ON width of the pulse is widened, and the ON periods may overlap. If so, a battery voltage little drops and no problem arises. If required, the ON point of the travel control pulse may be set at the reference time point "to", while the OFF point of the hydraulic control pulse may be set at the time point "to". A time chart describing an operation of the fork-lift truck based on a conventional control system in which the pulse generation timings are not synchronized with each other, is shown in Fig. 5. As shown, during a period that the pulses G1 and G2 overlap, the current is simultaneously applied to the travel motor and the hydraulic motor. Accordingly, a battery current remarkably increases, and a battery voltage greatly drops. As seen from the foregoing description, the control system for industrial use vehicles according to the present invention prevents the ON pulses from overlapping. Accordingly, a great drop of the battery voltage will never occur. Then, a voltage drop in the main circuit is small. Therefore, the improper control problem, which is due to an insufficient drive power of motor and a voltage drop, is solved. No large current consumption ensures a long lifetime of the battery. The control system according to the present invention is also featured by the switching between the power travel mode and the regenerative mode. This feature will be described with reference to Fig. 6. Immediately after the travel lever 7 is turned in a direction, the MPU controller 14 sets up an operation mode like the normal power travel mode, as shown in Fig. 6. That is, it turns on the contact Mf of the forward contactor, and the contact Mg of the regenerative/power travel select contactor. Then, it applies the same ON pulse as that in the normal power travel mode, to the travel switching element 17CH. Consequently, a current Ib flows from the battery BA to the armature 17A. During an OFF period succeeding to the supply of the ON pulse, when the travel motor reverses its rotation, allowing the regeneration, a voltage is induced in the right direction in the armature 17A . As a result, as indicated by a broken line, a plugging current Ip flows in a closed loop consisting of the plugging diode Dp and the contact Mg (closed) of the contactor. Accordingly, the regenerative mode or the power travel mode can be determined by checking whether or not the plugging current Ip exceeds a preset level within a predetermined period (to be given later). If it exceeds the preset level, control determines that the regenerative mode is allowed, and opens the contact Mg, and effects the regenerative control. If it is below the preset level within that period, control determines that the power travel mode is allowed, continues the power travel control. The regenerative/power travel check operation will be described with reference to Fig. 7 showing a timing chart. In the figure, when the lever 7 is operated, the controller 14 produces and ON pulse G at a fixed period of 4 ms toward the switching element 17CH. In synchronism with this, the armature current Ia flows during the ON period, while the exciting current If and the plugging current Ip flow during the OFF period, as shown. In this instance, the plugging current Ip exceeds the preset value immediately after the third pulse G. Accordingly, control determines that the regerative mode is allowed. Upon this determination, the contact Mg is opened. During a period of about 8ms to open the contact, the pulse G is locked. The period for the regenerative/power travel check is a fixed period immediately after the ON pulse G is generated by operating the travel lever 7, e.g., 16 ms or less. Subsequently, the control on the basis of the determination result, that is, the control of the regerative mode or the power travel mode, will be performed. When the regenerative determination is made during the above check period, the check period terminates. For the OFF period of the travel switching element 17CH, the armature current Ia is expressed by Ia = Ip + If where Ip : plugging current, and If : exciting current. If the travel motor is not reversed, Ip = 0 (zero), and hence Ia = If . If it is reversed (regenerative), Ip =/ 0 (zero), the plugging current Ip is proportional to the induced voltage E of the armature, and is Ip = E/rA The induced voltage E is E = k x If x N where K is proportional constant, and N is the number of revolutions. Thus, the plugging current Ip is proportional to the number of revolutions. Therefore, the plugging current exceeds the preset level after one pulse when the motor runs at a high speed, after two to three pulses when it reversely runs at a medium speed, and after three to four pulses when it reversely runs at a low speed. As described above, if the pulse period is 4 ms, it can be determined within 4 to 16 ms. Particularly in the high speed reverse run of the motor requiring a steep deceleration response, the determination is made within 4 ms. Since the slip-off time of the contact Mg is 8 ms, a switch time to the regenerative mode in the high speed reverse run, is 4 + 8 = 12 ms. A maximum switch time in the low speed run is 16 + 8 = 24 ms. Thus, a high response switching to the regenerative mode is realized. In the power travel acceleration, there is no time lag, ensuring a high response control of the fork-lift truck. Additionally, the plugging current Ip flows only when the motor reversely runs, ensuring a reliable determination. An embodiment of the present invention in which electric power consumed by an exciting col of a contactor is saved by chopper controlling the exciting coil of a contactor, will be described with reference to Figs. 8 and 9. In a circuit arrangement shown in Fig. 8, an exciting voltage of the exciting coil MF (forward) or the exiting coil MR (reverse) of the travelling contactor is detected by a comparator 19. The detected signal is applied through an A/C converter 20 to an MPU controller 14. A chopper duty ratio is selected so that a full voltage is applied to the exciting coil during a predetermined period from an instant that the exciting of the exciting coil starts, and subsequently a voltage Vs slightly higher than a minimum contact hold voltage is maintained. The travelling switching element 17CH is chopping controlled by an output signal of the controller 14 that depends on the chopper duty ratio. Thus, in the Fig. 8 circuit, the exciting current of the coil MF (forward) or MR (reverse) is detected and the exciting coil voltage is controlled and maintained at a fixed value. In a circuit arrangement shown in Fig. 9, a battery voltage variation is directly detected. By using the detected battery voltage, the chopper duty ratio is appropriately corrected and consequently the exciting coil voltage is maintained at a fixed value. A monitor display additionally featuring the present invention will be described. The monitor display provides a message of management information using characters, for example, when the fork-lift truck normally operates, and provides a trouble message by characters and the like for each symbol representing various monitor locations when the truck is abnormal. A display board for such displays is shown in Fig. 10. A display of Fig. 10 is for the normal fork-lift truck. A battery liquid level indicator 29 is a level meter using a plurality of LEDs. A monitor display 30 is contructed with an LCD. Seven symbols 31 to 37 under the monitor display indicate items to be checked in daily inspection or when the truck is operated. When the truck is normal, a character display line 38 displays a message of management information of hour meter by alphanumeric and/or Japanese characters. A message of a trouble is displayed in Fig. 11. In this instance, a fuse in an oil-pressure circuit is burned out. In this case, the indicator 32 attendant with "HYD" representing a hydraulic system flickers to give an alarm. At the same time, a detailed message "Fuse in hydraulic system" indicating a trouble location is also displayed. The message flows from left to right when displayed. Display of up to ten digits is possible. The control of the above display is performed at the input/output of the MPU control 14.

Claims: A control system in a battery fork lift having a control device (14) for controlling a travel mode and a cargo-handling; said control system comprising: travel indication means (7) for indicating a travel direction and a travel speed by a travel accelerator (7); cargo indication means (8,9,10) for indicating a cargo-handling such as lift and tilt by a cargo-handling lever (8,9,10); a travel main circuit (16) for driving a travel motor (16A,16W), said travel main circuit being capable of switching between a power travel mode and a regenerative brake mode; characterized by: plugging current detection means (Rp) for detecting a plugging current (Ip) flowing into a plugging diode (Dp) connected in parallel to an armature (16A) of said travel motor (16A,16W); and control means for determining whether the plugging current (Ip) exceeds a predetermined value during an OFF pulse period within a predetermined period after said travel main circuit (16) starts to operate, or not, once said travel main circuit (16) operates in said power travel mode in response to a signal representative of the travel direction indicated by said travel indication means (7), and for producing a control signal to select said regeneration brake mode if the plugging current (Ip) exceeds said predetermined value, and to continue said power travel mode if the plugging current (Ip) does not exceed said predetermined value. A control system in accordance with claim 1, wherein said control means producing a control signal to set a reference time point in a fixed period generated therein at an OFF point of a pulse of a travel signal or a cargo signal, and to set at an ON point of a pulse of the other when said travel indication means (7) and said cargo indication means (8,9,10) output said travel signal and said cargo signal simultaneously, to make an overlap of said travel signal and said cargo signal minimum. A control system in accordance with claim 1 or 2, wherein a travel main circuit (16) includes said travel motor (16A,16W) and contactors (Mg,Mf,Mr) for performing an open/close operation and reversal operation of a travel motor circuit, and a regenerative/power travel selection; a cargo main circuit (17) including a cargo motor (17A,17W) and an open/close contactor (Mp) within a cargo motor circuit; battery voltage detection means (21) for detecting a voltage of a battery (VB); and said control means correcting the voltage, which is detected by said battery voltage detection means, of an exciting coil (MG,MF,MR,MP) of the contactors (Mg,...Mp) included in said travel main circuit (16) and said cargo main circuit (17) to be constant exciting voltage, even if the voltage of said battery (VB) is changed.

Inventors: KIKUCHI SAMPEI, MAKINO NORIAKI, KIKUCHI, SAMPEI, MAKINO, NORIAKI
Applicants: NIPPON YUSOKI CO LTD, NIPPON YUSOKI CO.,LTD
Application year: 1989
Main classification: B66F9
IPC codes: B66F9, G07C5