JP2562645B2 - Boom energy regenerator for hydraulic excavator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention has a working machine movable by a hydraulic cylinder. The present invention relates to a potential energy recovery and utilization device that saves energy by recovering and reusing potential energy when a boom of a hydraulic excavator is lowered.

(Prior art) For a working machine of a hydraulic excavator, a large boom cylinder larger than the loading capacity was needed because the weight of the working machine itself had to be raised to a required height at the same time when loading earth and sand. However, as shown in FIG. 7, an auxiliary cylinder 11 is installed separately from the boom cylinder 5,
When raising the work implement, the oil from the hydraulic pump 16 driven by an engine (not shown) is supplied to the boom operation valve 17 and the conduit 22.
Through the boom cylinder 5 and the auxiliary cylinder 11, but when lowering the work machine, the oil from the hydraulic pump 16 flows into the cylinder head side chamber 5a, and the oil in the cylinder bottom side chamber 5b passes through the pipe line 22 and the boom operation valve 17. , Return to tank 23. However, the bottom side chamber 11 of the auxiliary cylinder 11
This oil cannot be returned to the tank 23 because it has the check valve 14, and is collected as pressure in the pressure accumulator 12 and is balanced with the weight of the working machine. Next, when the working machine is raised, the hydraulic pressure accumulated in the pressure accumulator 12 operates so as to raise the working machine.

(Problem to be Solved by the Invention) However, in the working machine 4, the position of the center of gravity of the working machine moves due to the extension amount of the arm cylinder 7, and the falling moment M = W × l of the working machine constantly changes.
The required holding pressure at 11 (when empty) also changes correspondingly. As shown in FIG. 3, the posture at the beginning of excavation, that is, when the arm cylinder 7 is shortest, the bucket cylinder 9 is longest, and the minimum reach state is reached, the hydraulic pressure accumulated in the pressure accumulator 12
Since it is necessary to prevent the work implement 4 from rising naturally, the set pressure of the relief valve 15a is set to a certain pressure or less, and when the pressure exceeds that pressure, the relief valve 15a is operated. When the boom cylinder 5 is contracted from the state before the excavation of the working machine 4 in FIG. 2, the working machine 4 descends and the oil in the auxiliary cylinder 11 is accumulated in the pressure accumulator 12, but when the relief valve set pressure is reached. While relieving, the working machine reaches the ground and is in the state of the excavation start shown in FIG. When horizontal excavation is performed from this state as shown in FIG. 4, the boom 6 is lowered while the Amoo cylinder 7 is extended, so that the auxiliary cylinder 11 is further contracted, but the pressure accumulator circuit 13a has already reached the relief hydraulic pressure. For auxiliary cylinder 11
Since the oil is not stored but the pressure is relieved, the efficiency of recovering the potential energy of the working machine 4 is lowered, and the energy saving effect is not so high. The present invention is directed to overcoming the above drawbacks.

(Means and Actions for Solving the Problems) In order to achieve the above object, a boom energy regeneration device for a hydraulic excavator according to the present invention includes a work machine including a boom, an arm, and a bucket that are sequentially connected to a vehicle body. A boom energy regeneration device for a hydraulic excavator, comprising: each cylinder that drives this work machine; and each operation valve that supplies the discharge oil discharged from the hydraulic pump to each cylinder,
An auxiliary cylinder arranged in parallel with the boom cylinders 5, 5, one of which is connected in parallel to the bottom side conduit of the boom cylinder 5, the pressure accumulator 12 and the variable relief valve 15, and the other of which is connected to the tank circuit. 11, a boom operation valve 17 that supplies and discharges the oil discharged from the hydraulic pump 16 to and from the boom cylinders 5, 5, a first detection unit 23 that detects a rotation angle of the boom 6 with respect to the vehicle body, and the boom 6 Second detecting means 24 for detecting the rotation angle of the arm 8 with respect to the first and second
The bottom side pressure of the boom cylinders 5, 5 is calculated in response to the signals from the detection means 23, 24, and the pressure accumulator is based on the calculation result.
It is configured to include a calculator 21 that outputs a command signal to a variable relief valve 15 that controls the accumulated pressure of 12.

According to the above configuration, the return oil when the boom is lowered is stored in the accumulator, and the stored pressure is reused and supplied to the auxiliary cylinder during the boom raising operation so that the auxiliary cylinder assists the drive of the boom cylinder. Therefore, it is possible to reduce the pump discharge pressure to the boom cylinder when the boom is raised.

(Example) An example of a potential energy recovery and utilization device according to the present invention will be specifically described with reference to the drawings. As shown in FIG. 1, in a hydraulic excavator 1 in which a turning body 3 is provided on a traveling device 2 so as to be freely turnable, a working machine 4 is attached to a front portion of the turning body 3. The working machine 4 sees a boom 6 that can be raised and lowered by a pair of boom cylinders 5. At the tip of the boom 6, an arm cylinder 7 is provided with an arm 8 so that the tip side can freely move forward and backward, and at the tip of the arm 8, Rotatable buckets 10 are attached by bucket cylinders 9, respectively. On the other hand, the boom cylinder 5 and the auxiliary cylinder 11 are supplied with oil pressure-fed from a hydraulic pump 16 driven by an engine (not shown) via a boom operation valve 17. Revolving car body 3 and boom 6
Between them, an auxiliary cylinder 11 is juxtaposed adjacent to the boom cylinder 5. A pair of boom cylinder 5 and auxiliary cylinder 11 are connected to the turning vehicle body 3 and boom 6 by pins 18 and 19, respectively.

The bottom side chamber 11a of the auxiliary cylinder 11 is connected to a pressure accumulator 12, a variable relief valve 15 and a check valve 14 by a pipe line 13.

The movement of the operating lever 20 is transmitted to the computing unit 21 as an electric signal. The computing unit 21 informs the boom operating valve 17 so that the instructed movement is performed in the working machine 4 by the operating direction and stroke of the lever 20. Since the electric signal is sent, the oil from the hydraulic pump 16 reaches the boom cylinder 5 and the auxiliary cylinder 11 through the boom operation valve 17 and the pipe line 22. When raising the boom 6, the command from the calculator 21 reaches the boom operating valve 17 by operating the operating lever 20 "up", so that the pressure oil from the hydraulic pump 16 is transferred to the boom cylinder 5.
And the auxiliary cylinder 11 and the pressure accumulator 12 circuit, the second
As shown in the figure, the boom and the auxiliary cylinder are in the fully extended state. From this state, lower the boom
In this state, the oil from the hydraulic pump 16 is fed into the rod side chamber 5a of the boom cylinder 5, but regardless of this, the falling moment M = W ×
The working machine 4 tries to fall due to the working of l. Therefore, since the cylinder is reduced, the oil in the bottom side chamber 5b of the boom cylinder is returned to the tank 23, but the oil in the bottom side chamber 11a of the auxiliary cylinder 11 is the check valve 14,
It cannot be returned to the tank, but is guided to the pressure accumulator 12 to compress and store the enclosed N ₂ gas. The degree of this pressure accumulation needs to be able to maintain the working machine 4 in a state of being suspended in the air by the hydraulic pressure generated in the auxiliary cylinder 11.

However, as is clear from FIGS. 2 to 4, the drop moment M = W × l is significantly different depending on the position of the working machine 4, so the set pressure of the relief valve must be changed according to the position of the working machine 4. I won't. Therefore, the boom angle detector 23,
The arm angle detector 24 is attached to the shaft supporting portions of the boom 6 and the arm 8, and the work machine position is calculated based on the signals from the angle detectors and the work machine weight W stored in advance. M is calculated in the calculator 21 according to the work machine control procedure shown in FIG. 5, and from the holding pressure equivalent to the boom cylinder when the work machine 4 is held only by the boom cylinder 5, the maximum pressure to be held by the auxiliary cylinder 11 hydraulic,
That is, the relief valve set pressure of the auxiliary cylinder 11 is calculated and is instructed to the variable relief valve 15. From the calculator 21 to the variable relief valve 15, P _ARO = P _AR Work machine movement, stop state P _ARO > P _AR Variable relief valve set pressure is small P _ARO <P _AR Variable relief valve set pressure is large The difference between the relief valve set pressure immediately before actuation and the required maximum hydraulic pressure instructs the variable relief valve to change its set pressure.

However, P _ARO is the relief valve set pressure immediately before operation, and P _AR is the maximum pressure to be retained by the auxiliary cylinder.

(Effects of the Invention) As described above, according to the boom energy regeneration device of the hydraulic excavator according to the present invention, the return oil when the boom is lowered is stored in the accumulator, and when the boom is raised,
This accumulated pressure is reused and supplied to the auxiliary cylinder so that the auxiliary cylinder assists in driving the boom cylinder, so the pump discharge pressure to the boom cylinder when the boom is raised can be reduced, and the hydraulic pump It reduces the horsepower consumption and saves energy.

[Brief description of drawings]

FIG. 1 is a control circuit diagram of a working machine according to an embodiment of the present invention,
2 is a side view showing a state before excavation of the hydraulic excavator, FIG. 3 is a side view showing a state at the beginning of excavation, FIG. 4 is a side view showing a state at the end of excavation, and FIG. FIG. 6 (a) is a flowchart showing the relationship between the boom cylinder stroke and the holding pressure at the maximum reach of the load according to the embodiment of the present invention, and FIG. FIG. 7 is a diagram showing the relationship between the boom cylinder stroke and the holding pressure at the maximum reach of the load according to the technology, and FIG. 7 is a control circuit diagram of the conventional working machine. 4 …… Work machine, 5 …… Boom cylinder 6 …… Boom, 11 …… Auxiliary cylinder 12 …… Accumulator, 14 …… Check valve 15 …… Variable relief valve, 16 …… Hydraulic pump 17 …… Boom control valve

Claims (1)

(57) [Claims] 1. A working machine comprising a boom, an arm and a bucket, which are sequentially connected to a vehicle body, cylinders for driving the working machine, and operating valves for supplying discharge oil discharged from a hydraulic pump to the cylinders. In the boom energy regeneration device of the hydraulic excavator equipped with, the boom cylinder 5,
5 is arranged in parallel, one of which is the bottom side pipe line of the boom cylinder (5), the pressure accumulator (12) and the variable relief valve (1
5) An auxiliary cylinder (11) that is connected in parallel to 5) and the other is connected to the tank circuit, and a boom operation that supplies and discharges the discharge oil from the hydraulic pump (16) to the boom cylinder (5, 5). A valve (17), a first detecting means (23) for detecting a rotation angle of the boom (6) with respect to the vehicle body, and a second detecting means (24) for detecting a rotation angle of the arm (8) with respect to the boom (6). ) And the first and second detection means (23, 2)
4) Receives the signal from the boom cylinder (5, 5) to calculate the bottom side pressure, and based on the calculation result, the accumulator (12)
And a calculator (21) that outputs a command signal to a variable relief valve (15) that controls the stored pressure of the boom energy regeneration device for a hydraulic excavator.