JP4886068B2 - Shock absorber shock absorber - Google Patents

Description

  The present invention relates to an excavator that uses vibration generated by an exciter, or a pile / sheet pile driving device that uses vibration to prevent the vibration of the exciter from being transmitted to the main body. The present invention relates to a shock absorber.

An excavator that uses both vibration and rotation transmits vibration to the rotating excavation shaft, but vibration is transmitted to the prime mover and reduction gear such as a hydraulic motor that drives the excavation shaft to rotate. Therefore, a shock absorber that prevents transmission of vibration is necessary. As the shock absorber, a rubber damper that can obtain a good shock absorbing action with a simple configuration is often used. Further, as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. Hei 8-232570), in an air hammer drill, there is an air shock absorber (air damper) that uses an air cylinder instead of rubber.
JP-A-8-232570

A rubber damper has a natural frequency, and depending on the frequency, resonance occurs and cannot absorb vibration. In addition, in a rotary / vibration type excavator, the pressing force of the excavation bit on the excavation surface during excavation is large. As a result, the solid rubber damper cannot sufficiently absorb vibration, and the buffering action may be insufficient.
In the case of an air shock absorber (air damper), the natural frequency of the air spring is expressed by equation (1).
K = γ ・ p ・ A ² / v (1)
Where K: Spring constant γ: Polytropic index p: Air cylinder internal pressure
A: Piston area v: Cylinder volume.
According to equation (1), the force to push the cylinder increases, the air cylinder internal volume (v) decreases, and the cylinder internal pressure (p) increases, so the spring constant (K) increases. Therefore, since the natural frequency can be changed according to the external condition (external force) received by the shock absorber, it can be used as a shock absorber for a vibration exciter that is used by changing the vibration frequency, and gas is used. Since it is a device, it can cope with high vibrations as compared with a shock absorber using rubber.

As shown in FIG. 6, the vibration exciter 1 incorporated in a drilling device or the like rotates two eccentric weights 11 and 11 arranged in parallel in opposite directions to cancel horizontal vibrations in the vertical direction. It is a device that extracts only vibration. In the conventional shock absorber 2 incorporated in the vibration generator 1, a frame 28 provided with a shock absorbing rubber receiving plate is installed on the upper part of the case 10 of the eccentric weight 11, and between the frame 28 and the inner surface of the slider 29. The vibration-providing device 1 is fixed to the slider 29 via the shock-absorbing rubber 24.
A spindle 3 that is rotatably mounted is connected to the lower end of the vibration generator 1, and a lower part of the spindle 3 is connected to a speed reducer 4 that can move up and down, and a prime mover provided in the speed reducer 4. (Hydraulic motor) 5 has a structure in which a rotational force is applied via a gear.

The vibration generated by the vibration generator 1 is transmitted from the vibration generator 1 to a spindle 3 and a drilling bit (not shown) at the tip of a boring rod (not shown). In the speed reducer 4, the spindle 3 is movable in the vertical direction, and the vibration is buffered and not transmitted to the speed reducer 4.
The upper portion of the case 10 of the vibration generator 1 is fixed to a slider 29 via a buffer rubber 24, and the generated vibration is attenuated by the buffer rubber 24.
The shear stress (τ) of rubber, which is a shock absorber, is
Since τ = G · δ / L, this spring constant (k) is k = A · G / L.
Here, τ: Shear stress G: Shear elastic modulus L: Rubber thickness δ: Deflection amount A: Shear area of rubber.

As described above, since the shock absorber using rubber has a natural frequency, it is an integral multiple of the natural frequency of the device in order to buffer so as not to generate resonance and transmit vibration to the main body. It is necessary to design the shock absorber appropriately so as not to vibrate at a frequency of. However, since the vibration frequency of the vibration generator may be changed according to the situation, a shock absorber using rubber that inevitably generates a natural frequency is not preferable. In addition, rubber has a drawback that it cannot absorb high frequency vibrations.
As an air damper using air as a shock absorber, as shown in Patent Document 1 (Japanese Patent Laid-Open No. 8-232570), an air spring composed of an air cylinder is used, and pressure air is supplied to the air cylinder, It has been proposed to change the natural frequency by adjusting the spring coefficient based on the equation (1).
This method is not particularly problematic for large-scale equipment, but the installation of an air compressor is an obstacle in terms of cost and miniaturization in small equipment, and the spring coefficient is not required even if an air compressor is required. There is a demand for an air shock absorber capable of changing the above.

A shock absorber consisting of an air cylinder and a piston used in combination with a vibration generator, and a one-way valve is provided at the intake and exhaust ports provided in the air cylinder, and the atmosphere moves into the air cylinder by the relative movement of the air cylinder and piston. In addition to being introduced into the air cylinder, it is automatically enclosed in an air cylinder to exert a buffering action.
In general, a shock absorber using air cannot be replenished with air leaking from a packing portion or the like unless air is supplied by a compressor or the like. However, a drill head including a vibration generator equipped with a shock absorber is moved up and down along the mast. Because the exciter connected to the piston is heavy, the shock absorber piston is lowered by raising the drill head, and the air is sucked into the air cylinder. By arranging the one-way valve, the outflow of air when the air in the air damper chamber is compressed is prevented.
Further, by providing an elastic body such as rubber or a spring at the bottom of the air cylinder, the impact when the piston collides with the bottom of the air cylinder is buffered, and the generation of vibration and noise are suppressed.

Sectional drawing of the state which integrated the shock absorber into the excavator which has a vibration generator. The expanded sectional view of the buffering device of the present invention. Operation | movement explanatory drawing which incorporated the shock absorber in the excavator which has a vibration generator. Sectional drawing of the state which incorporated the shock absorber which consists of two air cylinders into an excavator. Detailed sectional drawing of the shock absorber which consists of two air cylinders. Sectional drawing of the conventional shock absorber.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shaking device 10 Case 11 Eccentric weight 13 Non-rotating 2 Buffering device 21 Piston 22 Air cylinder 23 Air damper chamber 24 Rubber (elastic body)
25 Check valve 26 Piston rod 271 hole 28 Packing 3 Spindle 4 Reducer 5 Motor (hydraulic motor)
6 Inlet

In the soil contamination investigation machine, it is not preferable that the collected sample is disturbed by water. Therefore, unlike normal excavation, the excavation is performed without water. In the case of anhydrous excavation, the excavated sediment cannot be discharged to the ground using water, so the excavation of the excavated sediment is insufficient, so the excavated sediment needs to be pressed into the formation around the excavation hole, The excavation bit is excavated in a state where it is constantly pressed against the excavation surface. For this reason, the direction of the vibration to buffer is only one direction, and it is only necessary to make the buffer action effective only in the excavation direction.
As shown in FIG. 1, the vibration exciter 1 rotates two eccentric weights 11 housed in a case 10 in opposite directions, cancels horizontal vibrations, and takes out only vertical vibrations. Yes.

  A spindle 3 is rotatably attached to a lower portion of the vibration generator 1 via a thrust bearing 31 and a journal bearing 32, and vibration generated by the vibration generator 1 is transmitted to the spindle 3. The spindle 3 is mounted on a speed reducer 4 so as to be movable up and down. The rotation of a prime mover 5 such as a hydraulic motor provided in the speed reducer 4 is transmitted to the spindle 3 via a gear 41, and the spindle 3 vibrates. And rotate.

  The shock absorber 2 composed of the piston 21 and the air cylinder 22 shown in detail in FIG. 2 is fixed to the lower side of the vibration generator 1, and the piston 21 and the air cylinder 22 are provided with a packing 28 for keeping airtightness. is there. An air inlet 6 is provided in the upper part of the air cylinder 22, and a check valve 25 that allows only intake air is provided in the air inlet 6. When the piston 21 is lowered, air is sucked into the air cylinder 22 and is an air damper. Although the chamber 23 is filled with air, the air inside the air damper chamber 23 is not discharged even when the cylinder 21 is raised.

As shown in FIG. 1, the case 10 and the air cylinder 22 are connected by a detent 13 to prevent the vibration generator 1 from rotating due to the rotation of the spindle 3. The detent 13 has one end fixed to the case 10 with a bolt, and the other end provided with an enormous portion for retaining is inserted into a hole provided in the overhang provided in the air cylinder 22, The air cylinder 22 can move up and down with respect to the vibration generator 1.
As shown in FIG. 2, a cushioning rubber 24 is provided at the bottom of the air cylinder 22, and the surface thereof is uneven to adjust the spring constant. The rubber 24 can alleviate the impact when the piston 21 collides with the bottom of the air cylinder 22 to some extent, and an anti-vibration effect is obtained.

A drill head D including a vibration generator 1, a shock absorber 2, and a speed reducer 4 is attached to a mast M provided in a mobile machine so as to be movable up and down as shown in FIG.
A boring rod is connected to the lower end of the spindle 3 with a lower screw, and the vibration generated by the vibration generator 1 is transmitted to the boring rod and further to the excavating bit via the spindle 3 and excavation proceeds. The pressing force of the excavation bit necessary for excavation on the ground is obtained by the force when the drill head D is lowered along the mast M.

The operation of the shock absorber according to the present invention will be described below.
When the drill head D is raised along the mast M at the start of excavation, the air cylinder 22 is raised, the piston 21 is relatively lowered, the air damper chamber 23 is formed, and the surrounding atmosphere is sucked through the check valve 25. The air damper chamber 23 is filled with air.
Next, when the drill head D is lowered, since the excavation bit is in contact with the excavation surface, the piston 21 cannot be lowered, and the air cylinder 22 is lowered relative to the piston 21. However, since the check valve 25 does not release air to the atmosphere side, the air in the air damper chamber 23 is compressed. When the force that lowers the drill head D and the force (cross-sectional area × air pressure) obtained by the pressure in the air damper chamber 23 are balanced, the descent of the drill head D stops.

The natural frequency of the air damper is determined based on Equation (1) depending on the state at this time.
By oscillating the vibration generator 1 and adjusting the pressing force of the excavation bit against the excavation surface, the vibration is buffered and excavation can be performed with an appropriate vibration isolation effect.
As described above, instead of supplying air to the air damper chamber by the compressor, by raising the drill head D along the mast M, air is sucked into the air damper chamber 23 through the check valve 25 and filled with air. Since the natural frequency of the shock absorber can be changed by adjusting the force that lowers the drill head D, the vibration frequency of the vibration generator can be changed without causing resonance.

Example In a polluted soil survey, etc., in order to collect a high-quality soil sample, excavation sampling is performed without performing water transfer for discharging soil from the excavation hole, and the excavated soil is pressed against the surrounding ground by compaction. Since it does not discharge to the ground, the excavation bit is pressed against the excavation surface for excavation, and the direction of vibration to be buffered is only one direction.
On the other hand, in general boring fields such as construction of water wells and grounding work, water can be sent for soil removal. For this reason, a part of the weight of the boring rod or the like may be received by the drill head and excavation may be required while pulling the boring rod upward.
The vibration generated by the vibration generator 1 can be buffered by the air shock absorber even when a certain amount of weight of the boring rod or the like is lifted upward by the drill head. The apparatus will be described.

As shown in FIGS. 4 and 5, the vibration generator 1 is the same as that shown in FIG. 1. A shock absorber 2 including a piston 21 and an air cylinder is provided on both sides of the case 10 of the vibration generator 1, and a piston rod 26 of the shock absorber 2 is connected to the case 10 with a pin. A packing 28 is provided to keep the airtight state between the piston 21 and the air cylinder 22.
An intake port 60 is provided in the lower part of the air cylinder 22 of the shock absorber 2, and a check valve 61 having a structure in which air can be sucked into the lower part of the air cylinder 22 and cannot be exhausted. The pressurized air generated by an air compressor (not shown) or the like is pumped to the piston 21, the piston 21 is raised by the pressurized air, and an air damper chamber 23 'is formed.

A groove is formed in the middle of the air cylinder 22, and a hole 271 that communicates with the atmosphere is provided in the groove. When the piston 21 rises and the packing 28 fixed to the outer periphery of the piston 21 passes through the hole 271, the pressurized air inside the air damper chamber 23 ′ passes through the groove through the oblique groove 211 of the wear ring 210 of the piston 21. The pressure in the air damper chamber 23 'is released to the atmosphere from the hole 271 and the pressure in the air damper chamber 23' decreases to atmospheric pressure. Therefore, the piston that has risen falls because the pressure drops, and the area of the groove that is open to the atmosphere is throttled, and the air pressure corresponding to the weight that the drill head D lifts upward is maintained at the equilibrium position. Stop.
At this equilibrium position, the vibration generated by the vibrator 1 is transmitted to the shock absorber 2 through the case 10, and the vibration is absorbed.

That is, assuming that the pressure b (MPa) for supporting the piston 21 with the air cylinder 22 is A (cm ² ), the upward force F is F = 100 × b × A (N). With this force, the drill head is lifted to absorb vibrations and exhibit a buffer function. The maximum holding force is when the support air pressure reaches the maximum pressure (P) of the compressor. When the required holding force exceeds the maximum pressure (P), the piston 21 descends, but the check valve at the lower end of the air cylinder 22 61 operates to increase the pressure in the air damper chamber 23 'and increase the holding force. If the required holding force is more than that, it cannot be held only by air pressure, and the piston 21 descends and presses the rubber damper 24 provided at the lower part of the air cylinder 22, and the elastic force of the rubber damper compensates for the shortage.
When the air damper chamber 23 ′ is not filled with compressed air, the air damper chamber 23 can be used to absorb vibrations in only one direction by introducing air from the atmosphere.

  The shock absorber of the present invention can be used as a shock absorber for a machine that uses vibration, and is applicable not only to a vibration / rotation excavator but also as a shock absorber for a vibration-type driving device in which a construction member such as a sheet pile is built. Is possible.

Claims (2)

A shock absorber consisting of an air cylinder and a piston used in combination with a vibration generator, and a one-way valve that can only be inhaled is provided at the intake port provided at the top of the air cylinder and provided at the bottom of the air cylinder. A one-way valve that can only be inhaled is provided at the intake port, and a groove with a hole communicating with the atmosphere is formed in the middle of the air cylinder, and pressurized air is introduced from the intake port at the bottom. Shock absorber. 2. The shock absorber according to claim 1, wherein rubber having a surface provided with irregularities for adjusting a spring constant is provided at the bottom of the air cylinder.

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