JPH01199002A - Position energy recovering activating device for hydraulic excavator - Google Patents

Abstract

PURPOSE:To increase an amount of recovered energy, by a method wherein a pressure accumulator, a variable relief valve, and a check valve are coupled to the chamber on the bottom side of an auxiliary cylinder mounted in parallel to a boom cylinder. CONSTITUTION:An auxiliary cylinder 11 is situated in parallel to a boom cylinder 5, and a pressure accumulator 12, a variable relief valve 15, and a check valve 14 are coupled to a chamber 11a on the boom side of the auxiliary cylinder through a line 13. During an excavation work, a signal equivalent to the holding pressure of the boom cylinder 5 is guided to the variable relief valve 15, and since the set pressure of the valve 15 is automatically changed according to drop moment of a working machine, the efficiency of energy recovery is improved and it serves to save energy.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention includes a working machine that is moved by a hydraulic cylinder. This invention relates to a potential energy recovery and utilization device that saves energy by recovering and reusing potential energy when lowering the boom of a hydraulic excavator.

(Conventional technology) For hydraulic excavator work equipment, when loading earth and sand, the weight of the work equipment itself must be lifted to the required height at the same time, so a boom cylinder larger than the loading capacity was required. However, as shown in FIG. 7, an auxiliary cylinder 11 is installed separately from the boom cylinder 5,
When raising the work equipment, oil is supplied from the hydraulic pump 16 driven by an engine (not shown) to the boom cylinder 5 and the auxiliary cylinder 1 through the boom operation valve 17 and the pipe 22.
However, when lowering the working 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 pull valve 17 and returns to the tank 23. However, because of the check valve 14, the oil in the bottom side chamber 11 of the auxiliary cylinder 11 cannot return to the tank 23, but is accumulated and recovered as pressure in the pressure accumulator 12, and is balanced with the weight of the work machine. The next time the working machine is raised, the hydraulic pressure accumulated in the pressure accumulator 12 is activated to raise the working machine.

(Problem to be Solved by the Invention) However, in the work machine 4, the center of gravity of the work machine moves due to the amount of extension of the arm cylinder 7, and the falling moment of the work machine M-W)/! Since the pressure constantly changes, the required holding pressure (when unloaded) in the auxiliary cylinder 11 also changes correspondingly. As shown in FIG. 3, when the position at the start of excavation is the minimum reach state with the arm cylinder 7 at its shortest and the packet cylinder 9R at its length, the work implement 4 naturally rises due to the hydraulic pressure accumulated in the pressure accumulator 12. Since it is necessary to prevent this, the set pressure of the relief valve 15a is set to a certain level below Shobara, and if the pressure exceeds that level, the work machine 4 that is operating the relief valve 15a is set to When the boom cylinder 5 is retracted from the state of
The pressure of the oil in the auxiliary cylinder 11 is accumulated in the pressure accumulator 12, but when it reaches the set pressure of the relief valve, it is relieved and the working machine reaches the ground and enters the state of starting excavation as shown in Fig. 3.

When horizontal excavation is performed from this state as shown in Fig. 4, the boom 6 is lowered while extending the arm linder 7, so the auxiliary cylinder 11 is further compressed, but the pressure accumulator circuit 13a has already reached the relief hydraulic pressure. As a result, the oil is not pressured and is relieved by the amount that the auxiliary cylinder 11 is compressed, so the recovery efficiency of the potential energy of the work la4 is low, and the energy saving effect is not very high. It aims to solve the problem.

(Means and effects for solving the problem) The gist of the present invention is that in a hydraulic excavator having a working machine 4 that is moved by a hydraulic cylinder, an auxiliary cylinder 11 is provided in parallel with a boom cylinder 5, and the bottom side chamber 11a of the hydraulic excavator is provided with an auxiliary cylinder 11 in parallel with a boom cylinder 5. By connecting the pressure accumulator 12, the variable relief valve 15 and the check valve 14 through the conduit 13, and changing the set pressure of the variable relief valve 15 according to the position of the work equipment 4, operations 41 to 14 can be performed.
Potential energy recovery for a hydraulic excavator, characterized in that hydraulic pressure is generated in the pressure accumulator 12 to balance the weight of the hydraulic excavator.
It is a utilization device.

During excavation work, a signal corresponding to the holding pressure of the boom cylinder 5 is guided to the variable relief valve 15, and the set pressure of the valve is automatically changed according to the drop key of the work equipment (M=WXZ). Increases collection efficiency and helps save energy.

(Example) An example of the potential energy recovery and utilization device based on the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, in a hydraulic excavator 1 in which a swinging vehicle body 3 is provided on a traveling device 2 so as to be able to freely turn, a work implement 4 is attached to the front part of the swinging vehicle body 3. The machine 4 has a boom 6 that can be raised and lowered freely by a pair of boom cylinders 5. At the tip of the boom 6, there is an arm 8 whose tip side can be moved back and forth by an arm cylinder 7. At the tip of the arm 8, a packet can be A rotatable packet 10 is attached to each cylinder 9. On the other hand, boom cylinder 5
Oil is supplied to the auxiliary cylinder 11 via a boom operation valve 17, which is pumped by a hydraulic pump 16 driven by an engine (not shown). Between the swing vehicle body 3 and the boom 6, an auxiliary cylinder 11 is arranged adjacent to the boom cylinder 5. A pair of boom cylinders 5 and auxiliary cylinders 11 are connected to the swing vehicle body 3 and the boom 6 by pins 18 and 19, respectively.

A bottom chamber 11a of the auxiliary cylinder 11 is connected to a pressure accumulator 12, a variable relief valve 15, and a check valve 14 via a conduit 13.

The movement of the operating lever 20 is transmitted as an electrical signal to the computing unit 21, and the computing unit 21 controls the boom operating valve 17 so that the instructed movement is performed in the work equipment 4 according to the operating direction and stroke of the lever 20. Since the electric signal is sent, the oil from the hydraulic pump 16 is transferred to the boom operation valve 17.
, and reaches the boom cylinder 5 and the auxiliary cylinder 11 through the conduit 22. When raising the boom 6, the command from the calculator 21 reaches the boom operation valve 17 by operating the operation lever 20 "up", so that the pressure oil from the hydraulic pump 16 flows into the boom cylinder 5, auxiliary cylinder 11 and pressure accumulator 12. The circuit is filled and the boom and auxiliary cylinder are fully extended, as shown in FIG. When the boom is lowered from this state, oil from the hydraulic pump 16 is sent into the rod side chamber 5a of the boom cylinder 5, but regardless of this, the falling moment due to the weight of the work equipment 4) M= WXjl! works and the work equipment 4 tries to fall.For this reason, the cylinder is reduced, so 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 Because of the check valve 14, it cannot return to the tank, but is led to the pressure accumulator 12, where the sealed nitrogen gas is compressed and accumulated.The degree of this pressure accumulation is determined by
It is necessary that the working machine 4 can be maintained in a suspended state by the hydraulic pressure generated within.

However, as is clear from FIGS. 2 to 4, the falling moment M=WXj2 significantly differs depending on the position of the working machine 4, so the set pressure of the relief valve must be changed depending on the position of the working machine 4.

For this reason, the boom angle detector 23 and the arm angle detector 2
4 is attached to the shaft support of the boom 6 and arm 8, and the falling moment M of the work equipment is calculated from the calculation of the work equipment position based on the signals from the respective angle detectors and the work equipment 1■i1W stored in advance. Calculator 2I according to the work equipment control procedure shown in Figure 5.
Calculate the maximum hydraulic pressure to be held in the auxiliary cylinder 11, that is, the relief valve set pressure of the auxiliary cylinder 11, from the boom cylinder equivalent holding pressure when the work equipment 4 is set to be held only by the boom cylinder 5. The variable relief valve 15 is instructed to do so. From the calculator 21 to the variable relief valve 15, P Mllllll ” P All → Movement of work equipment, stop state PAIIO > PAIL → Variable relief variable valve leaf valve set pressure P□. <PAll → Variable relief variable valve leaf valve set pressure The set pressure of the variable relief valve is instructed to be changed based on the difference between the required maximum oil pressure and the relief valve set pressure immediately before activation.

However, PARo is the relief valve set pressure immediately before activation, PAR
indicates the maximum pressure to be maintained in the auxiliary cylinder.

(Effects of the Invention) In the present invention, the set pressure of the variable relief valve is controlled according to the falling moment of the working machine, so compared to the case where the conventional relief valve is installed, the set pressure of the variable relief valve is controlled in accordance with the falling moment of the working machine. ), the amount of energy recovered in the pressure accumulator increases, which can be used as lifting force when lifting the work equipment.
Great energy savings can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a control circuit diagram of a working machine in an embodiment of the present invention;
Figure 2 is a side view showing the state of the hydraulic excavator before excavation, Figure 3 is a side view showing the state at the beginning of excavation, Figure 4 is a side view showing the state of the excavation road, and Figure 5. 6(a) is a flowchart of the work equipment control according to the embodiment of the present invention, FIG. 6(a) is a diagram showing the relationship between boom cylinder stroke and holding pressure at the time of maximum load reach, and FIG. 6(b) is FIG. 7 is a diagram showing the relationship between the boom cylinder stroke and the holding pressure at the time of the maximum reach of a load according to the prior art, and FIG. 7 is a control circuit diagram of the conventional work machine. 4...Work i 5...Boom cylinder 6...Boom 11...Auxiliary cylinder 1
2... Pressure accumulator 14... Check valve 15.
...Variable relief valve 16...Hydraulic pump 17...
Boom operation valve patent applicant Komatsu Ltd. Agent (patent attorney) Oka 1) Kazuki (a) (b) Figure 6 Figure 7

Claims (1)

[Claims] In a hydraulic excavator having a working machine 4 that is moved by a hydraulic cylinder, an auxiliary cylinder 11 is provided in parallel with the boom cylinder 5, and a pressure accumulator 12, a variable relief valve 15, and a check valve 14 are connected to a conduit 13 in a bottom side chamber 11a of the auxiliary cylinder 11. Hydraulic excavation characterized in that hydraulic pressure that balances the weight of the working equipment 4 is generated in the pressure accumulator 12 by connecting the working equipment 4 with the working equipment 4 and changing the set pressure of the variable relief valve 15 according to the position of the working equipment 4. Potential energy recovery and utilization device for machines.