JPS6222019B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is designed to prevent shock vibrations from rigid blocks such as the installation parts of machines such as presses, forging machines, and weaving machines that continuously generate shocks with almost constant cycles, machine foundations, etc. This relates to a dynamic vibration absorption method that alleviates the impact and thereby suppresses the force of impact transmission to the ground, etc.

Vibration isolation for this type of machine includes anti-vibration rubber,
One possible method is to install an anti-vibration spring between the machine and its installation foundation, but this method reduces the impact transmission force from the foundation to the ground due to impact input, even if the natural frequency of the support is as low as possible. cannot be suppressed. In order to solve this problem, we installed the machine on a floating base with an inertia block, lowered the natural frequency by using the buoyancy generated by floating it in a water tank, and also lowered the natural frequency by using the inertia block with a large inertia block. A method of absorbing the impact transmission force is known (for example, see Japanese Patent Publication No. 7727/1983). However, in this method, machines such as forging machines and inertia blocks are floated by buoyancy, so an air chamber and a water tank are required to accommodate the buoyancy, and this construction has the disadvantage of being large-scale, and is difficult to implement in practice. The above is not appropriate as a vibration isolation method for existing equipment.

On the other hand, it is also known that dynamic vibration absorbers installed auxiliary on the foundation are effective in absorbing the vibration transmission force from the installation foundation to the ground caused by machines with a steady vibration source. be. This method has a wide range of applications, and is used to prevent engine vibrations and overhead wires from vibrations caused by wind pressure. However, it is known that when an impact input is applied to a machine foundation, the impact transmission force to the ground cannot be suppressed, and that it is effective only in accelerating the damping vibration after the impact, that is, in suppressing residual vibration.

The present inventor took advantage of the fact that vibration absorption by a dynamic vibration absorber is simple in principle and has a large effect on steady vibration sources. As a result of continuing research on methods that can suppress vibrations, we have developed a dynamic vibration damping method that advances the phase by a certain amount of time from the moment the shock is applied to the foundation, for machines that apply sustained shocks to the foundation with almost constant cycles. When an impact is applied to the machine mass, the foundation becomes in a state where it has a negative transmission force to the ground due to the interaction with the dynamic vibration absorber, which cancels out the positive impact transmission force from the machine that is subsequently applied, and causes a large width. We have discovered that it is possible to suppress the impact transmission force, and based on this knowledge, we have developed the present invention.

A method for suppressing the impact transmission force from the foundation to the ground based on the present invention will be described in detail with reference to FIG. 1, which shows the basic concept of the present invention.

In Fig. 1, 1 represents the ground, 2 represents a machine that continuously generates an impact with a nearly constant period, 3 represents a rigid block such as the installation foundation of the machine, and 4 and 5 represent the relationship between the rigid block and the ground. The foundation that transmits the impact force between the ground system is assumed to be an equivalent spring and an equivalent dart pot. Reference numeral 6 denotes a dynamic vibration absorber auxiliary mounted on a rigid block in parallel with the machine, and is equipped with a mass 7, a spring 8, and a dash pot 9.

Now, in such a system, an impulsive input indicated by arrow A is applied by the machine 2 at approximately constant intervals. At this time, if the dynamic vibration absorber 6 is not installed, the impact transmission force from the rigid block 3 to the ground will occur repeatedly at the period of the impact input as so-called free damped vibration. Therefore, the natural frequency of the dynamic vibration absorber vibration system added auxiliary to the rigid block is set near the natural frequency of the above-mentioned free damped vibration, and the damping is set to 2 times the damping constant between the rigid block and the ground. Set at least twice as high as this to restrain the dynamic vibration reducer vibration system. Furthermore, the double-headed arrow B in the figure is the synchronous shock input introduced in the present invention. At this time, F ₀ : Size of impact generated by the machine αF ₀ : Size of synchronous impact input g ₁ (t): Impact transmission force from the foundation to the ground generated by the impact applied from the machine g ₂ ( t): Impact transmission force from the foundation to the ground caused by the synchronous impact applied to the dynamic vibration absorber T: Repetition period of the impact generated by the machine t _a : Advance time when applying the synchronous impact, the mechanical and dynamic vibration absorber Shock transmission force from the foundation to the ground during operation with synchronous control to the equipment x
(t) is x(t)=g ₁ (t)F ₀ +g ₂ (t+t _a ) αF ₀
...(1) becomes. Making this sufficiently small means suppressing the impact transmission force.Next, to do this, x(t) is squared integrated within one period T, and t _a , α is calculated to minimize it. Indicates that it exists. That is, J ₁₁ =∫ ^T ₀ g ² ₁ (t) dt ... (2) J ₁₂ (t _a ) = ∫ ^T ₀ g ₁ (t) g ₂ (t + t _a ) dt ... (3) J ₂₂ = ∫ ^T ₀ g ² ₂ (t + t _a ) dt ... (4) J = ∫ ^T ₀ x ² (t) dt ... (5) If defined as, J = {J ₁₁ +2J ₁₂ (t _a ) α + J ₂₂ α ² }F ² ₀
...(6) Therefore, α that minimizes this J is α ^* = −J ₁₂ (t _a )/J ₂₂ ...(7) At this time, J ^* = {J ₁₁ −J ² ₁₂ ( t _a )/J ₂₂ }F ² ₀ ...(8
) becomes. Here, J ₁₁ F ² ₀ is α = 0, that is, the square integral value of the shock transmission force generated in the mechanical foundation-dynamic absorber system when only the dynamic vibration absorber is installed (this value is the value when the dynamic vibration absorber is installed). It can be seen that the system to which synchronous control input is added is even smaller. Here, J ₁₂ (t _a ) defined earlier is the mutual interference term between the dynamic vibration absorber and the mechanical foundation system, and setting this to a large value is J 12 (t a ).
It can be seen that ^* can be made even smaller. Here t _a
The minimum value of J ^* is reached by changing several times, and t _a at this time is the advance of time during synchronous control, and with this t _a, for g ₁ (t) in equation (1),
g ₂ (t+t _a ) is in a state where an opposite transmission force is generated.

As a result of calculations assuming various cases, when the mass ratio of the dynamic vibration absorber and the rigid block is set to 1/20 to 1/10, t _a is 1/6 to 1/6 of the natural period of vibration of the rigid block.
It was found that it is sufficient to set 1/3 and α to 0.5 to 0.7. These can be determined strictly by calculation, but in the present invention, in the synchronous control circuit, α is kept constant and t
Adjust _a and set it to minimize the impact transmission force, that is, the shaking of the ground in this state, and then adjust α and set it so that the impact transmission force is further minimized. This state is the most effective operating time for suppressing shock transmission force, and it is possible to absorb shocks that are about 1/10th that of the case without a dynamic vibration absorber.

The configuration and operation of the apparatus implementing the present invention will be explained in more detail with reference to FIGS. 2 and 3. Figure 2 shows a case in which a forging machine is used as a machine that generates a sustained impact with a nearly constant period, and a hydraulic vibration device is used as an impact generator that generates a synchronous impact input shown by arrow B in Figure 1. I will explain about it. The principle method is the same even when other machines or impact generating devices are used.

In FIG. 2, reference numeral 11 is the ground, in which a foundation 13 corresponding to the rigid block is installed, and an impact generating machine, that is, a forging machine 1, is placed in the center of the foundation.
2 is installed. The impact force generated in this forging machine is based on forced impact by the piston rod 12a. Further, the dynamic vibration absorber 16 has a mass portion 17 and is restrained to the foundation 13 by a spring 18 and a dart pot 19. Here, a case is shown in which the same dynamic vibration absorbers 16 are installed in parallel on the left and right to maintain force balance on the foundation, but in this case, one dynamic vibration absorber explained in Fig. The mass, spring stiffness, and doss pot damping constant will each be adjusted to 1/2 compared to the case where it is installed.
The shock generating device 20 attached to the dynamic vibration absorber 16 includes a hydraulic cylinder 21, a piston 22 operated by the hydraulic cylinder 21, a servo valve 23 that controls the generation of periodic impact force on the dynamic vibration absorber 16, and a hydraulic power source 24. A striking impact is applied to the vibration absorber 16 by a piston 22.

In addition, an optical displacement meter 25 attached to the forging machine 12
This optical displacement meter 2 detects the moment when the piston rod 12a hits the workpiece.
An observation circuit 26 and a synchronous control circuit 27 are sequentially connected to the servo valve 5, and the synchronous control circuit 27 is further connected to a drive circuit 28 which generates a signal for driving the servo valve 23.

Next, suppression of impact transmission force based on the above configuration will be explained.

The impact from the forging machine 12 is applied to the foundation 13 as a repeated impact impact over time as shown in FIG. 3A, and generates an impact transmission force from the foundation 13 to the ground 11 as shown in FIG. . On the other hand, the impact impact is caused by the piston rod 12 in the forging machine 12.
Since it is added by the fall of a, the piston rod 1
The optical displacement meter 25 observes the moment when 2a hits the workpiece. This displacement meter output is
It is extracted as an on/off signal as shown in Figure B,
After a certain time delay, the pulse train is adjusted and shaped into the pulse train shown in FIG. 3C. The observation circuit 26 performs this
and a synchronous control circuit 27. This pulse train signal is sent to the drive circuit 28, which generates a drive signal for the servo valve 23 of the shock generator 20 according to the time period and height of the pulse (FIG. 3D), and this is sent to the servo valve 23. By operating the hydraulic piston 22 shown in FIG. 2, a synchronous impact force is generated on the dynamic vibration reducer. This impact is repeatedly applied as an impact force as shown in FIG. As shown in Figure 3G, the impact transmission force to is opposite to that shown in Figure 3(F). As a result, the impact transmission force from the foundation to the ground when the impact generator in the forging machine and dynamic vibration absorber is operated is greatly suppressed and reduced as shown in Figure 3H, minimizing ground shaking. be able to.

As is clear from the detailed description above, according to the present invention, there is no need for large-scale construction of the foundation itself, and external additional devices, such as auxiliary dynamic vibration absorbers, shock generators, synchronous control circuits, and drive circuits can be installed. All you need is space to install it, and there is no need to move existing forging machines or other machines, and there is no need to remove or reinstall them. Furthermore, since the method according to the present invention suppresses the impact transmission force from the foundation to the ground and at the same time suppresses the shaking of the foundation itself, it does not reduce the efficiency of material processing operations using a forging machine or the like.

[Brief explanation of the drawing]

Fig. 1 is a principle explanatory diagram of the dynamic vibration absorption method of the present invention, Fig. 2 is a configuration diagram of the case where the present invention is applied to vibration absorption for a forging machine, and Fig. 3 A to H
2 is a waveform diagram of an impact or a signal at each part in FIG. 2. FIG. 1, 11... Ground, 2... Machine, 3... Rigid block, 6, 16... Dynamic vibration absorber, 13... Foundation,
17... Mass part, 20... Impact generator.

Claims (1)

[Claims] 1. Shocks applied by a machine to the mass part of a dynamic vibration absorber attached in parallel to a rigid block such as a machine foundation on which a machine that generates a continuous shock with a nearly constant period is installed. By applying an impact by the impact generator with a certain time phase advance relative to the period of , a negative transmission force is generated from the rigid block to the ground in advance, thereby transmitting the impact in the positive direction from the subsequent impact from the machine. A method of dynamic damping of shock vibrations characterized by canceling forces and reducing the transmission of shock forces from rigid blocks.