JPH01220700A - Shock absober for fork lift - Google Patents

Abstract

PURPOSE:To soften a shock during travelling without losing the cargo handling operability by opening between an accumulator and a lift cylinder when a lift operating selector valve is at a a neutral position and a shock detecting sensor detects a shock. CONSTITUTION:In the case where lift operation is not conducted, a switch 5 interlocking with a lift operating lever 5 is turned on. Under such a condition, when a shock detecting sensor 13 detects a shock applied to a lift cylinder 6 from above, an electric current is let flow from a control amplifier 12 to a solenoid 11 of a buffering selector valve 1. By this operation, the buffering selector valve 10 is switched to an offset position to connect an accumulator 9 to the lift cylinder 6. Accordingly, a shock applied to the lift cylinder 9 is absorbed by the accumulator 9 using operating oil as a medium and softened. Then, operating oil passed from the lift cylinder 6 to the accumulator 9 is again returned to their interior of the lift cylinder 6 after a shock is removed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a hydraulic circuit for cargo handling in a forklift truck, and more specifically, to a system for alleviating the impact that a lift cylinder receives when traveling on a road surface with a difference in level. This relates to a shock absorber for

[Prior Art] There are various conventional types of cargo handling hydraulic circuits for operating the lift cylinders of forklifts, and a typical one is shown in FIG.

That is, in FIG. 2, hydraulic oil is pumped from an oil tank 3 to a lift operation switching valve 4 by a hydraulic pump 2 driven by an engine 1. This switching valve 4 can control the flow of hydraulic oil by tilting the lift operating lever 5.

The lift cylinder 6 and the lift operation switching valve 4 are connected by one pipe 7, and when the lift operation lever 5 is operated to send hydraulic oil to the lift cylinder 6 through this pipe 7, the piston rod of the lift cylinder 6 is connected. 8 extends and the mast (not shown) rises.In contrast, if the lift operation switching valve 4 is controlled to drain hydraulic oil from the lift cylinder 6, the piston rod 8 will be moved by the weight of the mast etc. falls, and the hydraulic oil is returned to the oil tank 3 from the lift cylinder 6 through the switching valve 4.

[Problems to be Solved by the Invention] In such a conventional configuration, no means is provided for absorbing and mitigating the impact acting on the lift cylinder 6.
Therefore, if a downward impact is applied to the lift cylinder 6 when the lift operation switching valve 4 is in the neutral position, the loaded object will jump on the fork, giving the driver a larger impact than that received from the wheels. This would lead to an unstable situation such as the rear wheels lifting up, which could cause problems in operating the machine.

Therefore, as shown in Fig. 3, a method of connecting the accumulator 9 to a pipe 7 connecting the lift cylinder 6 and a lift operation switching valve (not shown) can be considered, but this method eliminates the influence of the accumulator 9 during cargo handling operations. There is the problem of receiving it.

Accordingly, an object of the present invention is to provide a shock absorbing device capable of alleviating shocks during traveling without impairing the operability of cargo handling operations.

[Means for Solving the Problems] The M-town device for a forklift according to the present invention includes an accumulator connected to a conduit between a lift cylinder and a lift operation switching valve in a cargo handling hydraulic circuit, and an accumulator connected to a pipe between a lift cylinder and a lift operation switching valve. t'llll opens and closes against
an impact detection sensor that detects the impact acting on the lift cylinder, and a control means that switches the position of the buffer switching valve according to the signal from the impact detection sensor and the state of the lift operation switching valve. The control means switches the position of the buffer switching valve to open the gap between the accumulator and the lift cylinder when the lift operation switching valve is in the neutral position and the impact detection sensor detects an impact. It is characterized by the fact that

[Function] In the shock absorbing device according to the present invention configured as described above, when an impact is applied to the lift cylinder while the vehicle is running, the accumulator is connected to the lift cylinder, thereby absorbing and mitigating the impact.

[Embodiments] Hereinafter, preferred embodiments of a shock absorber for a forklift according to the present invention will be described in detail with reference to the drawings.

Note that the same reference numerals will be used to describe parts that are the same as or corresponding to the conventional configuration.

As shown in the first (21), the cargo handling hydraulic circuit related to the lift cylinder 6 includes an oil tank 3 and a hydraulic pump 2 that pumps hydraulic oil from the oil tank 3 and supplies it to the lift cylinder 6, as in the past. and a lift operation switching valve 4 that controls the flow of hydraulic oil.The lift operation switching valve 4 selects hydraulic oil for the lift cylinder 6 by manually operating a lift operation lever 5. supply and discharge.

The hydraulic oil discharged from the lift cylinder 6 is returned to the oil tank 3.

An MfR switching valve 10 is interposed in a conduit 7 that connects the lift operation switching valve 4 and the lift cylinder 6.

This switching valve 10 is a solenoid type, 3-bottom, 2-position type, and the solenoid 11 is not energized! At 'II (normal position), the lift cylinder 6 and the lift operation switching valve 4 are in communication. An accumulator 9, preferably a plug-type accumulator, is connected to the other boat of the buffer switching valve 10, and this accumulator 9 is closed when the switching valve 10 is in the normal position.

A solenoid 11 of the buffer switching valve 10 is connected to a control amplifier 12 which is a control means. The control amplifier 12 has a function of energizing the solenoid 11 of the buffer switching valve 10 in response to a signal from the impact detection sensor 13 to switch the valve position.

The impact detection sensor 13 may be mounted at any position as long as it can detect a vertical impact acting on the lift cylinder 6, but is preferably near the center of the front axle axis, for example.

The power source 14 of the control amplifier 12 uses an on-vehicle battery, and a switch 15 linked to the lift operation lever 5
Accordingly, the power supply 14 is controlled.

Next, in such a configuration, the present invention! The operation of the ffr device will be explained.

First, when a lift operation is being performed, that is, when the lift operation lever 5 is tilted so that the fork is raised or lowered, the switch 15 linked to the lift operation lever 5 is opened, and the control amplifier 11 is powered on. 1
4 is cut off. In this case, the buffer switching valve 10 remains in the normal position, and the lift cylinder 6 and the lift operation switching valve 4 are in communication, so that normal cargo handling operations can be performed. Further, since the accumulator 9 is separated from the cargo handling hydraulic circuit, the accumulator 9 does not affect the cargo handling operation.

When the lift operation is not performed, the switch 15 interlocked with the lift operation lever 5 is turned on.

In this state, when the impact detection sensor 13 detects an impact acting on the lift cylinder 6 from above, a current is passed from the control amplifier 12 to the solenoid 11 of the M section switching valve 10, thereby causing the illumination switching valve 10 to be offset. The accumulator 9 is connected to the lift cylinder 6. Therefore, the impact acting on the lift cylinder 6 is absorbed and alleviated by the accumulator 9 using the hydraulic oil as a medium. The hydraulic oil that has drained from the lift cylinder 6 into the accumulator 9 is returned into the lift cylinder 6 after the impact has disappeared.

The operating time during which the 1fFr switching valve 10 is in the offset position is determined by the magnitude of the impact and is adjusted by the control amplifier 12. In other words, if the impact is large,
The operating time becomes longer accordingly.

In the above embodiment, a three-bottom, two-position solenoid type switching valve is used as the buffer switching valve 10, but those skilled in the art will easily understand that the type is not limited to the one shown. It will be.

[Effects of the Invention] As described above, according to the present invention, the impact acting on the lift cylinder is alleviated, so that the loaded object does not jump on the fork during travel. Therefore, the impact on the driver is reduced, and an inoperable state such as the rear wheel lifting off does not occur, so safety is improved. Furthermore, since the accumulator is separated from the lift cylinder during cargo handling, cargo handling operations can be performed without being affected by the lift cylinder. Furthermore, since the shock absorber according to the present invention is not attached to the wheels like a car, the original function of the forklift will not be impaired.

[Brief explanation of the drawing]

Fig. 1 is a hydraulic circuit diagram showing an embodiment of a shock absorber for a forklift according to the present invention, Fig. 2 is a hydraulic circuit diagram of a conventional forklift, and Fig. 3 shows a conventional hydraulic circuit in which an accumulator is simply connected. In Figure 0, which is a hydraulic circuit diagram, 4... Lift operation switching valve 5... Lift operation lever 6... Lift cylinder 7
...Pipeline 9...Accumulator 10
...Buffer switching valve 11...Solenoid 12.
... Control amplifier (control means) 13 ... Shock detection sensor 14 ... Power supply 15 ... Switch

Claims (1)

[Claims] an accumulator connected to a pipe between a lift cylinder and a lift operation switching valve in a cargo handling hydraulic circuit of a forklift; a buffer switching valve that opens and closes the accumulator with respect to the lift cylinder; and a buffer switching valve that acts on the lift cylinder. an impact detection sensor that detects an impact; and a control means that switches the position of the buffer switching valve according to a signal from the impact detection sensor and a state of the lift operation switching valve, the control means controlling the lift operation switching valve. When the operating switching valve is in a neutral position and the impact detection sensor detects an impact, the position of the buffer switching valve is switched to open the gap between the accumulator and the lift cylinder. A forklift shock absorber featuring: