JPS594165Y2 - Construction machinery hydraulic circuit - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a hydraulic circuit for construction machinery in which an equivalent cylinder is provided in a closed circuit connected to a hydraulic cylinder to absorb a difference in flow rate due to a difference in pressure receiving area.

In hydraulic cylinders generally used in construction machinery,
The pressure receiving area is different between the rod side and the bottom side.

For this reason, when a hydraulic cylinder is connected to a closed circuit and an equal amount of hydraulic pressure flows to the rod side or the bottom side, there will be an excess on the rod side and an insufficient amount on the bottom side.

Therefore, various means for compensating for this have been proposed in the past, but all of them have the disadvantage that they are complicated in mechanism and require hydraulic cylinders and hydraulic motors of the same capacity, making them generally expensive.

This idea was made with the aim of eliminating such drawbacks, and by providing an equivalent cylinder with a small stroke in the closed circuit connected to the rod side or bottom side of the hydraulic cylinder, it absorbs the difference in flow rate due to the difference in pressure receiving area. The purpose of this project is to provide a hydraulic circuit for construction machinery that has been developed to simplify the structure and reduce costs.

This invention will be described in detail below with reference to an illustrated embodiment.

In the figure, 1 is a variable displacement pump, 2 is a hydraulic cylinder,
These are connected by closed circuits 3 and 4.

Furthermore, a relief valve 5, a shuttle valve 6, and a check valve 7 are provided between the closed circuits 3 and 4, and the oil that is insufficient due to leakage is pumped from the charge pump 8 through the check valve 7 to each closed circuit 3. and 4, and there is an equivalent cylinder 9 in the middle of the closed circuit 3 connected to one of the closed circuits 3 and 4, for example, the rod side chamber 2 of the hydraulic cylinder 2.
is provided.

The equivalent cylinder 9 consists of a cylinder 9a, a piston 9b housed in the cylinder 9a, and a piston rod 9C protruding from one end surface of the piston 9b.
The rod side chamber 9□ of the hydraulic cylinder 2 is connected to the rod side chamber 2 of the hydraulic cylinder 2, and the bottom side chamber 92 is connected to the variable displacement pump 1 side.

Also, the rod side chamber 2□ and bottom side chamber 2 of the hydraulic cylinder 2
The pressure receiving areas S1 and S2 of the cylinder 9 and the pressure receiving areas S1' and S2' of the rod side chamber 9□ and bottom side chamber 9□ of the equivalent cylinder 9 are set to be in a proportional relationship with each other.

It becomes.

Note that 10 is a piston valve built into the piston 9b of the equivalent cylinder 9, which is closed when the piston 9b moves, but when the piston 9b reaches the stroke end, the piston rod 10a is pushed by the cylinder end face and opens. The rod side chamber 9 □ and the bottom side chamber 9 □ are communicated with each other to perform a reset function of making the strokes of the hydraulic cylinder 2 and the equivalent cylinder 9 match when a difference occurs.

However, when the variable displacement pump 1 discharges a flow rate of Q into the closed circuit 4 in order to extend the hydraulic cylinder 2, the piston 2a of the hydraulic cylinder 2 has a speed of 1θ, and a flow rate of oil flows into the rod side chamber 9 of the equivalent cylinder 9. Suru.

Due to this, the piston 9b of the equivalent cylinder 9 moves to the side chamber 9□ at a speed of ``''C'', and the flow rate from the bottom side chamber 9□' (from equation (1) is transferred to the 4-displacement pump 1. It starts to flow out, and the rod side chamber 2 of the hydraulic cylinder 2
The equivalent cylinder 9 absorbs the difference in flow rate due to the difference in pressure receiving area between the bottom side chamber 22 and the bottom side chamber 22.

Further, when the hydraulic cylinder 2 is shortened, the flow is opposite to the above.

As shown in FIG. 3, the equivalent cylinder 9 may be provided in a closed circuit 4 connected to the bottom chamber 2□ side of the hydraulic cylinder 2.

As detailed above, this idea is based on the fact that an equivalent cylinder whose pressure receiving area is proportional to that of the hydraulic cylinder is provided in the middle of the closed circuit connected to the hydraulic cylinder, and the difference in the pressure receiving area between the rod side chamber and the bottom side chamber of the hydraulic cylinder is Since the difference in flow rate due to This not only simplifies the structure and reduces costs, but also makes it possible to easily install an equivalent cylinder in a small space such as an engine room, making it possible to change the design of existing construction machinery, or to reduce costs due to increased weight. No problems such as increased costs occur.

Furthermore, since the capacity in the closed circuit is small, the capacity of the charge pump and tank is also small, making it economical.

[Brief explanation of drawings]

The drawings show one embodiment of this invention, with FIG. 1 being a circuit diagram, FIG. 2 being a detailed view of an equivalent cylinder, and FIG. 3 being an explanatory diagram of another embodiment. 1 is a variable displacement pump, 2 is a hydraulic cylinder, 2. is the rod side chamber, 2□ is the bottom side chamber, 3 and 4 are closed circuits, 9 is the equivalent cylinder, 9□ is the rod side chamber, 9□ is the bottom side chamber, 10
is a piston valve.

Claims (2)

[Scope of utility model registration request] (1) In a system in which the variable displacement pump 1 and the hydraulic cylinder 2 are connected by closed circuits 3 and 4, the hydraulic cylinder 2 is connected to the rod side chamber 2□ and the bottom side chamber in the middle of the closed circuit 3 or the closed circuit 4. An equivalent cylinder 9 in which the pressure receiving area of 2□ is in a proportional relationship is connected to the rod side chamber 20 of each cylinder 2, 9,
9□ or bottom side chambers 2□ and 9□ are connected to each other in a hydraulic circuit for a construction machine. (2) In the piston 9b of the equivalent cylinder 9, the piston 9
A piston valve 10 opens when b reaches the stroke end to communicate the rod side chamber 9□ and the bottom side chamber 92.
A hydraulic circuit for a construction machine as set forth in claim (1) of the utility model registration, comprising: