JPH0336333A - Potential energy recovery and regeneration device for hydraulic excavators - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a device for recovering and regenerating potential energy that is possessed when a working machine of a hydraulic excavator ascends. The boom cylinder has a ram structure with an assist cylinder built into the rond (abbreviated as boom cylinder). When the boom is lowered, the oil discharged from the assist cylinder is stored in an accumulator, and when the boom is raised, it is released and utilized. The present invention relates to a potential energy recovery and regeneration device.

[Conventional technology]

Generally, when loading earth and sand with a hydraulic excavator, the weight of the machine must be lifted to the required height, so a boom cylinder that is larger than the loading capacity must be installed. The amount of work required to lift it to a predetermined height is wasted. For this reason, conventionally, the potential energy of the work equipment generated when lowering the work equipment is stored in an accumulator, and the boom raising force is constantly applied to the boom cylinder, and this is used when raising the work equipment. A working machine potential energy recovery and regeneration device has been proposed that can reduce the working oil pressure of the work machine and save energy.According to this, as shown in FIG. When the working machine is lowered, oil in the assist cylinder head side chamber 105a is allowed to flow into the accumulator 105, and the potential energy of the working machine is accumulated and recovered as pressure. When raising the work equipment, the work equipment itself is supported by the assist cylinder 115, so the weight of the work equipment is also absorbed by the boom cylinder 115.
The boom cylinder 101 is also small because it requires less work compared to the type that is lifted by 01.

In addition, Fig. 6 shows that the assist cylinder is not specially installed, and when the work equipment is lowered, the boom cylinder bottom side chamber 1
The oil 01a flows into the accumulator 105, and the potential energy of the work equipment becomes pressure and is recovered. When the work equipment is raised and the main operation valve 116 is operated, the hydraulic circuit 117 and the hydraulic circuit 11B are connected, and the hydraulic circuit 117 is connected to the hydraulic circuit 11B. The boom 110 is pushed up by the hydraulic pressure accumulated in the accumulator 110, but when the hydraulic pressure in the accumulator 105 acting on the pressure control switching valve 119 drops below the set pressure, the pressure control switching valve 119 switches and the pressure oil from the hydraulic pump 112 is switched. continues to flow into the boom cylinder bottom side chamber 101a to raise the working machine.

(Problem to be solved by the invention) However, in the conventional potential energy recovery and regeneration device shown in FIG. Therefore, a bracket must also be provided on the main body side, which increases manufacturing costs. In addition, in the conventional model shown in Fig. 6, when raising the work equipment, the oil stored in the accumulator first flows into the bottom side chamber of the boom cylinder, and then the pressure oil from the pump flows in, which is complicated. A four-position operating valve and a pressure control switching valve are required, which increases manufacturing costs, and the operating pressure when raising the boom is usually 70 to 80% of the relief setting pressure of the circuit.
In order to solve the above-mentioned problems, the present invention has the following drawbacks: boom cylinder 10
By making the inside of 1 a boom cylinder with a ram structure in which the assist cylinder rond that is fixed to the bottom wall of the boom cylinder slides, there is no need for a separate assist cylinder, and the operation valve can be of a simple shape. The purpose is to provide a potential energy recovery and regeneration device.

(Means for Solving the Problem) In order to achieve the above object, a hydraulic cylinder rond that moves the boom of a hydraulic excavator up and down is used as an assist cylinder, and an assist cylinder rond that is inserted into the assist cylinder so as to be movable forward and backward. has a ram structure in which the base end of the hydraulic cylinder is fixed to the bottom wall of the hydraulic cylinder, and
The assist cylinder oil chamber is communicated with an accumulator through a hydraulic circuit, and hydraulic pressure is stored in the accumulator when the hydraulic cylinder expands and contracts, thereby making it possible to recover and regenerate the potential energy of the working machine. The above-mentioned purpose is achieved by providing a switch valve operated by the accumulated pressure in the accumulator in the hydraulic circuit that connects the hydraulic circuit for raising the cylinder, so that the hydraulic circuit is brought into communication when the accumulated pressure gas in the accumulator is released. .

[For production]

With the above configuration, when the work equipment is lowered, the assist cylinder hydraulic oil flows into the accumulator and the pressure is accumulated. When the work equipment is raised, the switch valve is set to the direct state after the accumulator pressure has been discharged. , the pressure oil from the pump can also be allowed to flow into the assist cylinder oil chamber to prevent the boom lifting force from decreasing.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a hydraulic excavator according to an embodiment of the present invention, in which two boom cylinders 1 are connected to a main body 3a and a boom 1.
The boom cylinder 1 is installed between the boom cylinder 1 and the boom cylinder 1 so that the working machine 2 moves up and down as the boom cylinder 1 expands and contracts. In such a hydraulic excavator, the boom cylinder 1 has a ram structure in which an assist cylinder rod IC fixed to the boom cylinder bottom wall 16 slides inside the cylinder rod 1a, as shown in FIG. An assist cylinder oil chamber 1d is formed inside the cylinder rod 1a. Pressure oil from a hydraulic pump 12 is introduced into the bottom side chamber 1e and head side chamber if of the boom cylinder 1 via an expectation valve 13 by a hydraulic circuit 7.11. The assist cylinder oil chamber 1d and the accumulator 5 are connected by a hydraulic circuit 4, and a relief valve 6 is installed in the hydraulic circuit 4. A switch valve 9 is installed in the hydraulic circuit 8 that connects the hydraulic circuit 4 and the hydraulic circuit 7, and is operated by the accumulation of pressure in the accumulator 5. The valve 9 is structured to be held in a "closed" state.

Next, the operation will be explained. (1) When the boom is lowered, since the work implement 2 is in the direction of its own weight falling, the oil in the boom cylinder bottom side chamber 1e is discharged from the boat A to the tank 14 while being squeezed by the operation valve 13. Note that oil flows into the boom cylinder head side, boat B, from the hydraulic pump 12, but the operating pressure is very low.In this case, in the assist cylinder, since the boom cylinder 1 moves in the direction of contraction, the assist cylinder oil chamber 1d The oil in boat C
The initial sealing pressure Pa+ of the accumulator 5, which is sent to the accumulator and stored therein, and the cylinder pressure in the assist cylinder oil chamber 1d are the same, and as the cylinder stroke increases, the pressure in the accumulator 5 increases as shown in FIG. When the pressure increases and the boom is lowered by the cylinder stroke St, the oil pressure in the accumulator 5 becomes Pa, and the potential energy recovery of the work implement 2 corresponds to the shaded area El. When working with a hydraulic excavator, the full stroke of the boom cylinder is rarely used, so it is not necessary to install a large cylinder or emulator that can store the entire amount of oil in the accumulator when the cylinder is fully used. Since it is economical and expensive, an accumulator that can accumulate pressure according to the stroke amount during normal work is prepared, and when the stroke increases and the cylinder oil pressure (hydraulic pressure in the accumulator) exceeds the set pressure, the oil is released from the relief valve 6. In this way, the accumulator can be made smaller. (2) When raising the boom, the lifting force by the boom cylinder 1 is as shown in FIG. This is the resultant force of the force f8 that flows into the assist cylinder oil chamber 1d and stretches it, and the shaded part E2 is the regenerated energy.0 The cylinder stroke during normal operation is within the SL range, but if it is necessary to extend the cylinder further, That is, when the discharge of the pressure stored in the accumulator 5 is finished, the piston 5a of the accumulator 5 operates the switch valve 9 and changes the switch valve to a communicating state, so that the pressure oil that was acting on the boom cylinder bottom side chamber 1e is transferred to the hydraulic circuit. 8.4, it also flows into the assist cylinder oil chamber 1d, increasing the area of action of the pressure oil and exerting the same function (force) as a conventional boom cylinder without an assist cylinder IC installed. As a result, the assist cylinder rod IC is
Since it is located in the boom cylinder bottom side chamber 1e, the structure is such that it is possible to avoid a reduction in the operating area and a reduction in lifting force.

〔Effect of the invention〕

As explained above, according to the present invention, the assist cylinder is built into the boom cylinder, so there is no need to separately provide a bracket on the main body for mounting the assist cylinder, and the boom cylinder hydraulic circuit operating valve remains the same as before. can be used. Furthermore, by determining the relief valve setting pressure based on how the boom cylinder is used during normal work, it is possible to determine the most economical accumulator capacity. By providing a valve, the active area of the boom cylinder when raised can be made the same as that of conventional boom cylinders, making it possible to reduce manufacturing costs without reducing the potential energy recovery and regeneration function.

[Brief explanation of drawings]

Fig. 1 is a side view of a hydraulic excavator based on an embodiment of the present invention, Fig. 2 is a hydraulic circuit diagram of a potential energy recovery and regeneration device for a hydraulic excavator based on an embodiment of the present invention, and Fig. 3 is an assist cylinder. An explanatory diagram showing the stroke and the potential energy recovery state, FIG. 4 is an explanatory diagram showing the assist cylinder stroke and the potential energy regeneration state, FIGS. 5 and 6
The figure is a hydraulic circuit diagram of a potential energy recovery and regeneration device for a hydraulic excavator based on the prior art.

Claims (1)

[Scope of Claims] 1) The rod 1a of the hydraulic cylinder 1 that moves the boom 10 of the hydraulic excavator up and down is used as an assist cylinder, and the base end of the assist cylinder rod 1c is inserted into the cylinder so as to be movable forward and backward. In addition, the assist cylinder oil chamber 1d is connected to the accumulator 5 by the hydraulic circuit 4.
A potential energy recovery and regeneration device for a hydraulic excavator, characterized in that the potential energy of the working machine 2 can be recovered and regenerated by communicating with the hydraulic cylinder and accumulating hydraulic pressure in the accumulator when the hydraulic cylinder expands and contracts. . 2) A switch valve 9 operated by the accumulation of pressure in the accumulator 5 is provided in the hydraulic circuit 8 that connects the hydraulic circuit 4 and the boom cylinder raising hydraulic circuit 7, and the accumulator 5
2. The potential energy recovery and regeneration device for a hydraulic excavator according to claim 1, wherein the hydraulic circuit 4 and the hydraulic circuit 7 are brought into communication when the stored pressure gas is released.