JPH09175789A - Hydraulic circuit in lift for vehicular maintenance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the pressure in a communication passage in an early stage and start the ascending of right/left lifts while synchronizing by only turning ON a push button switch for ascending the lift. SOLUTION: In the hydraulic circuit with a parent and child type cylinder system in which a supply passage 7 for sending an operation oil in the lower cylinder room of a drive side cylinder 1 from an oil tank 3 through a pump and the upper cylinder room of the drive side cylinder 1 is connected with the lower cylinder room of a driven side cylinder 2 by a communication passage 8 and also a return passage 9 to the oil tank by branching the communication passage are installed, the oil pressure from the pump is exerted until the pressure in the communication passage reaches a set pressure at an initial state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit for synchronously driving left and right lifts in a vehicle maintenance lift.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 2, as a hydraulic circuit in a vehicle maintenance lift, a lower cylinder chamber of a drive side cylinder 16 composed of a double-acting cylinder and an oil tank 17 are connected via a pump 18. A parent-child cylinder in which the upper cylinder chamber of the drive side cylinder 16 and the lower cylinder chamber of the driven side cylinder 19 are connected by a communication passage 20, and the communication passage 20 is branched to provide a return passage 21 for communicating with the oil tank. The method is adopted.

[0003]

In the above hydraulic circuit of the parent-child cylinder system, when the left and right lifts are lifted from the lowermost position, the pump is operated to move the working oil in the oil tank to the lower cylinder chamber of the drive side cylinder. When it is sent, the piston rises, the working oil in the communication passage that connects the upper cylinder chamber of the driving side cylinder and the lower cylinder chamber of the driven side cylinder, and both cylinder chambers is compressed accordingly, and the piston rises due to the resulting pressure, The left and right lifts will rise.

In the meantime, when the above operation is performed, the piston of the driven side cylinder tends to lag behind the driving side, and a step H occurs in the left and right lifts. That is, the area within the hatched area shown in FIG. 2 is compressed, and the step H is generated. And
This step difference H increases as the load W increases. Also, if the driven side piston reaches the lowermost end in a state where it is lower than the driving side piston (a step is present) and then the driving side reaches the lowermost end from behind, the pressure in the communication passage will drop and the apparent Above, the driving side and driven side pistons have the same height. When the lift is raised again from that state, the pressure in the communication passage is lower than the predetermined pressure in the initial state, and thus a step is generated between the driving side and the driven side. When the lift is raised while the step is still occurring, the vehicle placed on the lift naturally tilts, and if the tilt becomes large, an accident such as a fall may be caused. Correction means are sometimes provided to correct the step manually.

The correction means branches the return path and connects it to the supply path downstream of the pump, connects a solenoid valve in the return path between the supply path and the communication path, and operates the solenoid valve. Is operated by operating a dedicated switch. As a result, when a step occurs as described above,
Operate the switch for operating the solenoid valve described above,
The solenoid valve is actuated, hydraulic oil from the pump is sent to the communication passage, the hydraulic pressure in the lower cylinder chamber of the driven side cylinder rises, and the step is corrected. Therefore, conventionally, the switch is turned on to operate the solenoid valve, and the switch is turned off while visually observing the movement of the lift on the driven side, which is troublesome and nervous. is there. When the driven side lift reaches the lower limit while being higher than the driving side lift, the solenoid valve is turned on by operating the above-mentioned switch to lower the driven side lift to the lowermost end and drain the hydraulic oil in the communication passage. The action of reducing the pressure is performed. However, when the solenoid valve is operated to reduce the pressure, the driven-side lift is located at the lowermost end, but the pressure in the communication passage is not always maintained at a predetermined pressure.
If the pressure is lower than the predetermined pressure, there is a problem that a step is generated between the driving side and the driven side when the pressure is raised again as described above.

[0006] The present invention has been made in view of the above-mentioned problems of the prior art.
An object of the present invention is to provide a hydraulic circuit in which the pressure in the communication passage is initially controlled only by turning on a push button switch for raising the lift, and the left and right lifts start to rise in synchronization.

[0007]

To achieve the above object, the technical means taken by the present invention are a supply path for feeding hydraulic oil from an oil tank to a lower cylinder chamber of a drive side cylinder via a pump, and a drive side. In the hydraulic circuit of the parent-child type cylinder system in which the upper cylinder chamber of the cylinder and the lower cylinder chamber of the driven side cylinder are connected by a communication passage, and the communication passage is branched to provide a return passage to the oil tank, in the initial state, It is characterized in that the hydraulic pressure from the pump acts until the pressure in the communication passage reaches the set pressure. As a structure in which the hydraulic pressure of the pump is applied to the communication passage, the return passage is branched and connected to the supply passage, and the solenoid valve and the pressure switch are connected in the return passage between the supply passage and the communication passage. Characterize.

According to the above means, when the lift push button switch is turned on, the pump for feeding the working oil of the oil tank to the drive side cylinder and the supply path connecting the oil tank and the lower cylinder chamber of the drive side cylinder. The solenoid valve connected to is turned on, and further, the solenoid valve provided in the return path connecting the communication passage and the supply passage is turned on, the hydraulic pressure from the pump is sent into the communication passage, and the pressure in the communication passage is increased. Is controlled. Then, the solenoid valve in the return path is turned on until the pressure in the communication path becomes equal to or higher than the set pressure set by the pressure switch.
When it is opened (opened) and the pressure exceeds the set pressure of the pressure switch, the solenoid valve is turned off. After that, the left and right lifts are hydraulic oil fed into the supply passage, and the communication passage that connects the drive side cylinder and the driven side cylinder It is raised synchronously by the hydraulic oil inside.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An example of an embodiment of the present invention will be described below with reference to FIG. 1. In the figure, 1 is a drive side cylinder, 2 is a driven side cylinder, 3 is an oil tank, and the drive side is The lower cylinder chamber 1a of the cylinder 1 and the oil tank 3 are connected to each other by a pump 5 operated by a motor 4 and a supply path 7 to which a solenoid valve (SOL.2) 6 is connected, and the upper cylinder chamber 1b of the drive side cylinder 1 is connected. And the lower cylinder chamber 2a of the driven side cylinder 2 are connected by a communication passage 8, and the communication passage 8 and the oil tank 3 are connected by a return passage 9.

Further, a solenoid valve is branched in the middle of the return path 9 and connected to the supply path 7 downstream of the pump 5 so as to communicate therewith, and in the return path 9'connecting the supply path 7 and the communication path 8.
(SOL.3) 10 and its solenoid valve (SOL.3) A pressure switch (PS-1) 11 that controls the closing movement of the solenoid 10 is connected, and a solenoid valve for descending (SOL. 1) 13 is connected. The solenoid valve (SOL.2) 6 connected to the supply path 7 and the solenoid valve (SOL.3) 10 connected to the return path 9'are solenoid valves that operate both up and down. Valve (SOL.2) 6 and solenoid valve (SOL.2)
3) Filters 12 are installed on the upstream side and the downstream side of 10, respectively.

The vehicle maintenance lift shown in FIG. 1 is of a type in which a free wheel lift is provided on the main lift, and a hydraulic line 15 for operating the free wheel lift is connected to a solenoid valve (SOL. 4) Connected via 14.

Next, the operation sequence of the above hydraulic circuit will be described. First, when the push button switch for raising is lifted to raise the lift from the lowermost end, the pump 5 and the solenoid valve (SO
L.2) 6 is turned on, and the solenoid valve (SOL.3) 10 is turned on (open) until the pressure in the communication passage 8 becomes equal to or higher than the pressure set by the pressure switch. Acts on the passage 8. The pressure in the communication passage 8 is the pressure switch (PS-1).
When the pressure exceeds the set pressure of 11, the solenoid valve (SOL.3) 10 becomes OF
F (closed) to stop the hydraulic pressure of the pump 5 from acting on the communication passage 8. Then, the left and right lifts, that is, the drive-side cylinder 1 and the driven-side cylinder 2 rise in synchronization. Of course, when the push button switch for raising the lift is turned on, if the pressure in the communication passage is equal to or higher than the set pressure, the solenoid valves are not turned on and both lifts rise synchronously without causing a step.

[0013]

The hydraulic circuit of the vehicle maintenance lift according to the present invention has the structure described in claims 1 and 2, and the connecting circuit for connecting the driving side cylinder and the driven side cylinder only by turning on the upward pushbutton switch. The pressure in the passage is initially controlled to eliminate the level difference between the two lifts, and then both lifts rise in synchronism with each other, which enables stable ascent and descent. Further, since the above-mentioned correction is only required to operate the switch for activating the lift, it is released from the troublesome and nervous operation as in the conventional case.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram showing an example of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a conventional hydraulic circuit.

[Explanation of symbols]

1 ... Drive side cylinder 2 ... Driven side cylinder 3 ... Oil tank 5 ... Pump 7 ... Supply path 8 ... Communication path 9, 9 '... Return path 10 ... Solenoid valve (SO
L.3) 11 ... Pressure switch (PS-1)

Claims (2)

[Claims] 1. A supply passage for feeding hydraulic oil from an oil tank to a lower cylinder chamber of a drive side cylinder via a pump, an upper cylinder chamber of the drive side cylinder and a lower cylinder chamber of the driven side cylinder are connected by a communication passage, and In the parent-child cylinder type hydraulic circuit in which the communication passage is branched to provide a return passage to the oil tank, the hydraulic pressure from the pump is applied until the pressure in the communication passage reaches the set pressure in the initial state. A hydraulic circuit in a vehicle maintenance lift characterized by the following. 2. A supply passage for sending hydraulic oil from an oil tank to a lower cylinder chamber of a drive side cylinder via a pump, an upper cylinder chamber of the drive side cylinder and a lower cylinder chamber of the driven side cylinder are connected by a communication passage, and In a parent-child cylinder type hydraulic circuit in which the communication passage is branched to provide a return passage to an oil tank, the return passage is branched and connected to a supply passage, and a return passage between the supply passage and the communication passage is provided. A hydraulic circuit for a vehicle maintenance lift, characterized in that a solenoid valve and a pressure switch are connected therein.