JP2770310B2 - Malfunction prevention device for forward / reverse switching circuit in industrial vehicles - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for preventing malfunction of a forward / reverse switching circuit in an industrial vehicle.

[Conventional technology]

Generally, in industrial vehicles such as small shovel loaders,
In the case where the variable displacement pump and the variable displacement motor are used in the traveling system hydraulic circuit, the forward / backward and stop and the change of the vehicle speed are performed by the control lever. This lever is operated to switch between three stages of a forward position, a stop position and a reverse position, and the inclination direction of the swash plate of the pump is changed accordingly.

That is, when the lever is at the forward position, for example, as shown in FIG. 4, the common terminal (C
When the OM) 41 and the A contact terminal (NO) 42 are connected, the electromagnetic forward valve 43 is excited, the swash plate of the pump is inclined toward the forward side, and the hydraulic motor is rotated at a low speed.
The low-speed forward running of the vehicle is performed.

When the vehicle is to be driven forward or backward at a high speed, the high-speed solenoid 51 is excited by the operation of one of the forward and reverse 2-speed switches SW1 and SW2 by a high-speed instruction operation of the lever, and the variable displacement motor is operated. The vehicle runs at high speed by adjusting the inclination angle of the swash plate and increasing the rotation speed of the motor.

And in the above state, the reverse limit switch LS2
Is connected to its COM44 and B contact terminal (NC) 45 and NO46
Is shut off, and the reverse valve 47 is demagnetized. next,
When the lever is turned to the reverse position in order to move the vehicle backward, the movement of this lever connects the COM44 and NO46 of the reverse limit switch LS2 as shown by the two-dot chain line, and the reverse valve 47 is excited. At the same time, COM41 of the forward limit switch LS1 is connected to NC48, NO42 is shut off, and the forward valve 43 is demagnetized, whereby the swash plate of the pump is tilted backward, the back buzzer 49 and the back lamp 50
The vehicle moves backward while displaying the reverse visually.

Also, when the lever is held at the neutral position, the COM41, 44 of both limit switches LS1, LS2 are shut off from NO42, 46,
When the valves 43 and 47 are demagnetized, the swash plate of the pump is held at the stop position, the rotation of the motor is stopped, and the running of the vehicle is stopped.

[Problems to be solved by the invention]

However, forward and reverse limit switches LS1, LS
In No. 2, NO42, 46 may be heated by the current flowing when the valves 43, 47 are driven from the COM41, 44 via NO42, 46, and these may be welded to the ends of the contacts. Therefore, despite the fact that the forward / reverse switching or the stop of traveling is attempted by the lever switching operation, each of the limit switches LS1, LS
2 is not switched, the swash plate angle of the oil pump is not changed, and the vehicle may travel in the wrong direction or continue traveling in response to the stop instruction.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a device for preventing malfunction of a forward / reverse switching circuit in an industrial vehicle capable of avoiding defective traveling of the vehicle and guaranteeing reliable stopping of traveling. Is to do.

[Means for solving the problem]

In order to solve the above-described problems, the present invention provides a variable displacement pump that drives a hydraulic motor for traveling a vehicle, and rotates the hydraulic motor in a direction in which the swash plate tilt direction of the variable displacement pump is changed to one and the vehicle moves forward. First changing means for changing the direction of inclination of the swash plate of the variable displacement pump to the other, and rotating the hydraulic motor in a direction for moving the vehicle backwards; ,
An instruction operating means for selectively instructing reverse and stop, based on a forward instruction of the instruction operating means, is switched to a direction in which the first changing means is driven, and based on a backward instruction and a stop instruction of the instruction operating means, First switching means for switching in a direction in which the first changing means is stopped, and switching in a direction for driving the second changing means on the basis of a backward instruction of the instruction operating means; A forward / reverse switching circuit for an industrial vehicle, comprising: a second switching unit that switches in a direction to stop the second changing unit based on a stop instruction, wherein the first switching unit drives the first changing unit. Direction, and when the second switching means is switched to the direction for driving the second changing means,
First forcible stopping means for forcibly stopping both of the change means, and second forcible stopping means for forcibly stopping both of the changing means in response to a stop instruction of the instruction operation means, regardless of a switching state of the both switching means. The gist of the provision is

[Action]

According to the present invention, when the above-mentioned means is employed, when the operator gives a forward instruction by the instruction operating means, the first switching means is switched to the direction for driving the first changing means,
The inclination direction of the swash plate of the variable displacement pump is changed to one, and the hydraulic motor is rotated in a direction for moving the vehicle forward. Also, when the operator gives a reverse command using the command operating device, the second switching device is switched to the direction in which the second changing device is driven,
The inclination direction of the swash plate of the variable displacement pump is changed to the other direction, and the hydraulic motor is rotated in a direction for moving the vehicle backward.

Here, when the first switching means or the second switching means is in a state where both of the switching means are switched in a direction for driving both of the changing means, the first forcible stopping means causes the two switching means to change. The means is forcibly stopped.

Further, when the operator gives a stop instruction by the instruction operation means, the second forcing means is forcibly stopped by the second forcible stopping means irrespective of the switching state of the two switching means.
As described above, when at least one of the two switching units is out of order, the vehicle can be reliably stopped.

〔Example〕

Hereinafter, an embodiment of the present invention will be described in detail with reference to the electric circuit diagrams shown in FIGS. This electric circuit drives and controls the hydraulic circuit of the traveling system of an industrial vehicle such as a small shovel loader to control the forward / backward and stop of the vehicle and the adjustment of the traveling speed. The function of will be described.

In FIG. 1, a circuit 3 for switching and stopping a traveling direction of a vehicle and a circuit 4 for controlling a vehicle speed are connected to a power source 1 as a driving source via a protective fuse 2. The circuit 3 is provided with a stop opening / closing switch 5 as a second forced stopping means which is always open, and the opening / closing switch 5 has a normally open contact ma1, forward and reverse.
a parallel circuit composed of electromagnetic forward and reverse valves 6 and 7 as first and second changing means connected respectively to ma2, and a first switching means and a second switching means A connection line C1 as first forcible stop means connecting the B contact terminals (NC) 8, 9 of the forward and reverse limit switches LS1, LS2 is connected in series. A reverse buzzer 11 and a reverse lamp 12 are connected in parallel to the reverse valve 7 via a fuse 10.

The stop opening / closing switch 5 is driven by operating a control lever 13 as an instruction operating means together with forward and backward limit switches LS1 and LS2. When the lever 13 is at the neutral position, the open / close switch 5 is opened, and the common contacts (COM) 14, 15 of the forward and reverse limit switches LS1, LS2 and the NC 8, 9 are respectively contacted by the contacts X, Y. It is to be connected.

When the control lever 13 is moved to the forward position or the reverse position, the open / close switch 5 is closed, and the COM14, 15 of the forward / reverse limit switches LS1, LS2 are connected to the A terminal contact (NO) 1.
No.6,17 are connected via contacts, respectively.
Forward and reverse contactor relays MA1, M connected to 7
A2 is excited to close the corresponding normally open contacts ma1 and ma2, and the valves 6 and 7 connected thereto are respectively operated.

These valves 6 and 7 change the inclination direction of the swash plate of the variable displacement pump P of the hydraulic circuit, and change and stop the rotation direction of the motor for rotating the driving wheels of the vehicle by this changing operation.

Further, COM14 and COM15 of the forward / reverse limit switches LS1 and LS2 are connected by a connection line C2 as first forcible stop means, and NO
The neutral safety relays 24 and 16 are connected via reverse voltage prevention diodes 18 and 19, respectively.

The neutral safety relay 24 enables the engine to be started only when the control lever 13 is in the neutral position, that is, the stop position, to ensure a reliable starting operation.

Further, when the circuit 4 is briefly described, the second-speed limit switches 20 and 21 connected in parallel to the power supply 1 are driven in accordance with a high-speed instruction operation of the control lever 13. That is, when the lever 13 is in the forward position and gives a high-speed command, the electromagnetic high-speed control valve 25 is excited by the closed high-speed limit switch 20, and the swash plate inclination angle of the oil motor M is adjusted. The oil suction amount is reduced, and the motor is driven to rotate at high speed. When the lever 13 gives a high-speed command when the vehicle is moving backward, the limit switch 21 is driven and the motor is rotated at a high speed. The limit switches 20 and 21 are connected to a neutral safety relay 24 via a reverse voltage prevention diode 22.

The operation of the forward / reverse switching circuit configured as described above will be described below.

When the lever 13 is in the forward position, the open / close switch 5 is closed as shown in FIG. 1, and the COM14 of the forward limit switch LS1 is connected to NO16. At this time, from the power supply 1 via the open / close switch 5,
LS2 NC9 → COM15 → Connection line C2 → Forward limit switch L
A circuit of COM14 → NO16 of S1 is formed, and the relay MA1 is excited. Therefore, the normally open contact ma1 is closed, and the swash plate of the pump P is tilted forward by the operation of the valve 6. As a result, the motor rotates in the forward direction, and the vehicle travels forward.

Next, when the lever 13 is switched to the reverse position, as shown in FIG. 2, the connection between COM14 and NO16 of the forward limit switch LS1 is cut off, the normally open contact ma1 is opened, and the reverse limit switch LS2 is opened. COM15 and NO17 are connected. Therefore, the normally open contact ma2 by the relay MA2 excited by the current flowing through the circuit of the on / off switch 5, the connection line C1, the NC8 of the forward limit switch LS1, the COM14, the connection line C2, the reverse switch LS2, and the NO17. Is closed. Therefore, while the valve 6 is stopped, the valve 7
Is driven, the swash plate of the pump P is inclined to the reverse side, and the motor is rotated in the reverse direction, so that the vehicle moves backward.

Further, although the lever 13 is switched from the forward position to the reverse position, as shown in FIG. 3, the contact X is contacted by heating the NO16 of the forward limit switch LS1 or the like.
Is welded, COM14 and NO16 are not blocked, and lever 13
COM15 and NO of the limit switch LS2 for reverse
17 is described.

At this time, the connection line C1 connected to the open / close switch 5 and the connection line C2 connecting the two COMs 14 and 15 are cut off.
No current flows from NO16 and NO17 to relays MA1 and MA2. Therefore, both valves 6 and 7 are stopped, and pump P
By holding the swash plate at the stop position, the supply of hydraulic oil to the motor is stopped, and the running of the vehicle is stopped.

Also, when a connection failure occurs due to the heating of NO17 on the reverse limit switch LS2 side, both valves 6 and 7 are not driven in the same manner as described above, the supply of hydraulic oil to the motor is stopped, and the pump P Is held at the stop position and the vehicle is stopped.

When the lever 13 is moved to the stop position in the state shown in FIG. 3, the open / close switch 5 is opened despite the fact that the COM14 and NO16 of the forward limit switch LS1 cannot be cut off. The valve 6 is not driven via the valve. Therefore, the swash plate of the pump P is held at the stop position, and the vehicle is reliably stopped.

Further, normally open contacts ma1, ma2 according to the operation of relays MA1, MA2.
Unlike the conventional product that directly drives the valves 6 and 7, since the valves 6 and 7 are operated by closing the circuit, the COM of the forward and reverse limit switches LS1 and LS2 is different.
It is possible to set a low current value between 14, 15 and NO16, NO17. Therefore, extreme heating of NO16, 17 is prevented, and the welding of contacts X, Y to NO16, 17 is greatly reduced. Thereby, the malfunction of the vehicle is extremely reduced.

〔effect〕

As described in detail above, the present invention exerts an excellent effect of avoiding defective running of the vehicle and guaranteeing reliable stopping of the running.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing a switching state when the vehicle is moving forward, FIG. 2 is an electric circuit diagram showing a switching state when the vehicle is moving backward, and FIG. FIG. 4 is an electric circuit diagram showing a conventional example. A stop opening / closing switch 5 as a second forcible stop means, a forward valve 6 as a first change means, a reverse valve 7 as a second change means, a control lever 13 as an instruction operation means, a first Connection line C as forcible stop means
1, C2, forward limit switch as first switching means
LS1, reverse limit switch L as second switching means
S2, variable displacement pump P, variable displacement motor M.

Claims (1)

(57) [Claims] 1. A variable displacement pump for driving a hydraulic motor for driving a vehicle, and first changing means for changing the inclination direction of the swash plate of the variable displacement pump to one direction and rotating the hydraulic motor in a direction for moving the vehicle forward. Second changing means for changing the swash plate inclination direction of the variable displacement pump to the other direction and rotating the hydraulic motor in a direction for moving the vehicle backward, and operated by an operator to select forward, backward and stop of the vehicle. An instruction operation means for instructing the first operation means, and a direction for driving the first change means based on a forward instruction of the instruction operation means, and a first change means based on a backward instruction and a stop instruction of the instruction operation means. A first switching unit that is switched to a direction in which the second operation unit is driven, based on a backward instruction of the instruction operation unit, and a forward instruction of the instruction operation unit. And a second switching means for switching the second changing means in a direction for stopping the second changing means based on the stop instruction. A forward / reverse switching circuit for an industrial vehicle, wherein the first switching means drives the first changing means. A first forcible stop means for forcibly stopping the two change means when the second change means is switched to a direction for driving the second change means, and a stop instruction of the instruction operation means. And a second forced stop means for forcibly stopping both of the change means regardless of the switching state of the both change means.