JPH10246384A - Pulsation damping device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To damp pulsation which occurs in fluid which flows in pipes of pneumatic and hydraulic drive sources effectively by a compact device by providing a main flow passage of fluid and an auxiliary flow passage of fluid and forming an annular clearance in which the fluids meet again at an acute angle to the main flow passage from the auxiliary flow passage. SOLUTION: A flow-in port 3 of fluid is formed in a straight cylindrical part 2 drilled at the center of a first cylindrical body 1, a straight cylindrical part 5 having the same axis as the straight cylindrical part 2 and a conical cylindrical part 6 are drilled in a second cylindrical body 4, and an outlet 7 for fluid is formed at the other end of the conical cylindrical part 6. Moreover, a second branched pipe 9 linked to a first branched part 8 which branches a part of fluid and is formed in the straight cylindrical part 2 is formed in the second cylindrical body 4, and an auxiliary flow passage 20 is formed by these branched parts 8, 9. The fluid which is branched in the auxiliary flow passage 20 meets a main stream at an outlet of a clearance 12 formed on a cross section which goes straight with a flow line of fluid toward the flow passage from a peripheral groove 11 communicated with the second branched pipe 9. At this time, the clearance 12 is formed at an angle of about 30 degrees for a stream of fluid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for attenuating pulsation generated in a fluid flowing in a pipe of an oil / pneumatic drive source, for example.

[0002]

2. Description of the Related Art It is generally known that pulsation occurs in a hydraulic circuit in a hydraulic circuit, for example, a vane pump in a power steering system. The pulsation of the fluid is likely to induce noise, malfunction of the control device, and the like, and it is required to establish a means for effectively reducing the pulsation of the fluid.

However, as a method for reducing the pulsation of the fluid, the following method has conventionally been adopted. That is, one of them is based on the principle of λ / 4 tube,
Specifically, a bellows tube is inserted into the hose, the phase of the fluid flowing inside and the phase of the fluid flowing outside are shifted, and then, the fluids with the shifted phases are superimposed to obtain the damping effect. Things. Another method is to attenuate pulsation due to volume expansion. This method attaches a branch pipe with a volume expandable structure to the main circuit and attempts to absorb the pulsation by expanding the volume against the pulsation of fluid. It is. Specifically, there are a mini-reactor manufactured by NOK, a pulse generator manufactured by Nippon-Hatsujo, and the like.

However, the former structure has a disadvantage that the pressure loss in the pipe is large, and the latter structure has a relatively wide space for installing the branch pipe portion.
However, there is a drawback in that the internal structure is complicated, resulting in an expensive product. Further, it is customary to attach a high-pressure rubber hose to the apparatus. Even in this case, a new hose different from the flow path is provided in the branch pipe.
The cost was inevitably increased due to the need for hardware.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a device for attenuating a pulsation generated in a fluid flowing in a pipe of an oil / pneumatic drive source, for example, and a pulsation damping device contributing to downsizing of an oil / pneumatic circuit system. The purpose is to provide.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the gist of the present invention is to provide a main flow path for a fluid, a sub flow path for a fluid, and the main flow path from the sub flow path. Pulsation damping device comprising an annular gap that re-merges at an acute angle to the fluid, preferably wherein the main flow path downstream of the annular gap is a tapered conical cylindrical portion. And
The sub-flow path referred to here may be a completely separate flow path or a flow path branched from the main flow path of the fluid in terms of the relationship with the main flow path of the fluid.

More specifically, a straight cylindrical portion having a coaxial flow passage through which the fluid flows, a conical cylindrical portion, and an annular gap positioned therebetween are provided. A conical cylinder having a cross section orthogonal to a flow line of the fluid, the cross section of the conical cylinder decreasing continuously from upstream to downstream of the fluid, and connected to the first branch pipe; A second branch pipe therein, the second branch pipe being connected to the annular gap, and the annular gap being immediately after the straight cylindrical portion and on a cross section orthogonal to the fluid flow line; The present invention relates to a pulsation damping device, wherein a fluid passing through a branch pipe is merged with a main flow path at an acute angle. still,
It goes without saying that the annular gap referred to in the present invention includes a spiral groove or projection.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention regards the pulsating state of a fluid as an irregular flow state, converts the fluid in this state into a spiral flow, and imparts regularity to the fluid in this process to attenuate the pulsation. Provided is a device for damping a pulsation without installing a pulsation damping device or the like for a fluid flow. That is, the present invention provides a pulsation damping device that reduces the pulsating state of a fluid by giving a swirling component to the fluid. Generally, the pulsating state of the fluid is the turbulence intensity in the axial and radial directions, that is, the fluctuation component. Depends on size. In addition, the total value of the fluctuation speed in the axis, radius, and circumferential direction is constant. Therefore, when a swirl component is given to the fluid, the axial and radial fluctuation speeds transition to the swirl direction having the highest degree of freedom (easy to absorb the flow fluctuation component). As a result, the fluctuation speed in the axial and radial directions is reduced, and the pulsation is reduced. As described above, the feature of the present apparatus is that pulsation can be damped without installing a separate pulsation damping device or the like.

According to a further aspect of the present invention, the straight cylindrical portion is a portion having a branch pipe that straightens the fluid and opens at the same time in a direction perpendicular to the streamline. The annular gap is arranged before the next conical cylindrical portion and after the straight cylindrical portion, and has a function of joining the fluid flowing through the branch pipe to the main flow path, and the gap amount of this portion is The diameter is made smaller than the inner diameter of the straight cylindrical portion. If it is larger, the desired spiral flow cannot be obtained. Further, the conical cylindrical portion allows the fluid to be led out from the annular gap portion because the pressure decreases continuously along the cross-sectional area of the flow path along the downstream side of the flow.

The fluid that has passed through the branch pipe is merged into the main flow path at an acute angle. This angle varies depending on the properties of the fluid such as the viscosity and the flow rate of the fluid, but it is merged at an angle of about 10 to 40 degrees. Is good.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The pulsation damping device of the present invention will be described below in more detail with reference to the drawings. FIG. 1 is a half sectional view of a pulsation damping device according to the fourth aspect. In the figure, reference numeral 1 denotes a first cylindrical body, in which a straight cylindrical portion 2 is bored at the center,
A fluid inlet 3 is formed. A second cylindrical body 4 is set integrally with the first cylindrical body 1, and a straight cylindrical part 5 and a conical cylindrical part 6 coaxial with the straight cylindrical part 2 are bored. A fluid outlet 7 is formed at the other end of the conical cylindrical portion 6. A first branch pipe 8 for branching a part of the fluid is formed in the straight cylindrical portion 2, and a second cylindrical body 4 is connected to the second branch body 4 with respect to the first branch pipe 8.
Are formed, and a sub-flow path 20 is formed by these. Reference numeral 10 denotes a blind plug for closing the first branch pipe 8 and the second branch pipe 9. This second branch pipe 9
Is connected to the circumferential groove 11, an outlet of the gap 12 is formed on a cross section orthogonal to the fluid flow line from the circumferential groove 11 toward the flow path, and the fluid branched by the sub flow path 20 is formed here. It will merge with the main fluid. The circumferential groove 11 provides a so-called flow turbulence removing function. A gap 12 is formed at an angle of 30 degrees with respect to the flow of the fluid. The outlet of the annular gap 12 is located immediately after the straight cylindrical portion 5. Is located on a cross section orthogonal to the fluid flow line, whereby the fluid becomes a spiral flow and exhibits a rectifying effect as a whole.

In this figure, arrows a, b and c indicate the flow directions of the fluid. And the thread portion 13 of the fluid inlet and outlet,
Numeral 14 is for connecting the pulsation damping device in the oil / pneumatic circuit, and the inner diameter of the screw portion 14 does not become larger than the inner diameter of the screw portion 13 in order to increase the flow velocity of the fluid.

Further, as a specific example of the pulsation damping device, the straight cylindrical portion 2 is a first cylindrical body 1 having a diameter of 120 mm.
Is a hole having a diameter of 20 mm. And, the sub flow path 20
Is a hole having a diameter of 5 mm, which divides a plane orthogonal to the straight cylindrical portion 2 into four equal parts. One end penetrates the straight cylindrical portion 2, and the other end is a hole closed with a blind plug 10. is there. The first branch pipe 8 is bent at a right angle so as to be parallel to the straight cylindrical portion 2, and is used for connection with the second branch pipe 9. The second branch pipe 9 formed in the second cylindrical body 4 has a diameter of 5 mm.
This hole is connected to the first branch pipe 8, is drilled at a right angle from the hole, and has an end closed by a blind plug 10 like the first branch pipe 8. The second branch pipe 9 is connected to the circumferential groove 11. An annular gap 12 is formed from the circumferential groove 11, and in this example, the gap amount δ measured in the flow direction of the fluid is 1 mm, and the ejection angle β from the gap measured from the axial direction is 30 degrees. It is. still,
Although the blind plug 10 is used in this figure as a means for closing the branch pipes 8 and 9 constituting the sub flow path 20, it is needless to say that the plug member is welded or closed with an adhesive. It is also possible.

The conical cylindrical portion 6 has a diameter of 20 m on the inlet side of the fluid.
m, a conical hole with a diameter of 16 mm on the outlet side, which is designed to provide a pressure gradient in the fluid by such a structure and generate a strong spiral flow.

The following experiment was conducted to prove the effect of the pulsation damping device of the present invention. That is, in order to verify the effect of the pulsation damping device of the present invention in power steering, the pulsation damping device of the present invention was set in series between the hydraulic power source side and the actuator side as shown in FIG. Power steering oil was used as the fluid, and a comparison was made between the case where this device was used and the case where it was not used. The FFT method (high-speed Fourier transform method) was used for the measurement. In FIG. 2, the distance between A and C is 230 mm, the distance between C and B is 480 mm, and point B is A
Point, pulsation damping device, 100 mm higher than point C. In addition, as a pipe, a normal pressure of 210 kgf / cm ² ,
A high pressure hose having an inner diameter of 0.5 inch was used.

FIG. 3 is a measurement result showing the ratio of the pressure at point A on the hydraulic pressure source side to the point B on the downstream side of the pulsation damping device in FIG. 2 as a function of the frequency f. As can be seen from FIG. 3, the pulsation damping device according to the present invention provides a significant pulsation damping effect particularly at a frequency f = 450 Hz or more, and at f = 740 Hz, the damping reaches about 35 dB. Frequency f =
At 450 Hz or less, it can be seen that the degree of attenuation is higher when this apparatus is not used, but it is expected that the attenuation effect is mostly large as a whole, and the non-attenuation part can be solved by future improvements.

FIG. 4 is a half sectional view of a pulsation damping device according to a second embodiment of the present invention. In this example, the sub flow path 20 is provided with a flow path of a completely different system from the main flow path, and is directly connected to the circumferential groove 11. For this reason, the branch pipe 8 of the above example does not exist. Here, d denotes the flow of the fluid in the sub flow path, 21 denotes a thread portion, and the other points are the same as in the above-described example.

[0018]

The pulsation damping device of the present invention has a relatively small number of members disposed in a direction orthogonal to the flow path in terms of structure.
There is an advantage that contributes to downsizing of the pneumatic circuit system. For example, it can be used in series with an oil / pneumatic transmission system such as a high pressure hose connecting the actuator side such as a valve and a piston with an oil / pneumatic source causing a pulsation such as a pump. It is an excellent device which does not require a wide space for its installation.

[Brief description of the drawings]

FIG. 1 is a half sectional view of a pulsation damping device according to the present invention based on claim 4;

FIG. 2 is a conceptual diagram showing an installation example of a pulsation damping device of the present invention.

FIG. 3 is a measurement result in which the ratio of the pressure at point A on the hydraulic pressure side and the point B on the downstream side of the pulsation damper in the installation example of FIG. 2 is expressed as a function of frequency f.

FIG. 4 is a half sectional view of a pulsation damping device according to a second embodiment of the present invention.

[Explanation of Signs] 1 {first cylinder, 2} central straight cylinder of the first cylinder, 3} fluid inlet, 4} second cylinder, 5} A straight cylindrical portion of a cylindrical body of 2; a conical cylindrical portion of a second cylindrical body; a fluid outlet; a first branch pipe; a second branch pipe; Blind plug, 11 ‥‥ circumferential groove, 12 隙間 annular gap, 13 ‥‥ fluid inlet thread, 14 ‥‥ fluid outlet thread, 20 ‥‥ sub-channel, 21 ‥‥ thread.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Tanaka 1-1-1 Kyobashi, Chuo-ku, Tokyo Inside Bridgestone Flowtech Co., Ltd. (72) Inventor Kiyoyuki Horii 5-chome, Kameguro 5-chome, Meguro-ku, Tokyo No. 15-501

Claims (5)

[Claims] 1. A pulsation damping device for a fluid, comprising: a main flow path of a fluid; a sub flow path of the fluid; and an annular gap that joins the main flow path from the sub flow path at an acute angle. 2. The pulsation damping device according to claim 1, wherein the main flow path downstream of the annular gap is a tapered conical cylindrical portion. 3. The pulsation damping device according to claim 1, wherein the sub flow path of the fluid is a flow path branched from a main flow path of the fluid. 4. A first branch pipe comprising a straight cylindrical part having a coaxial axis with a flow path through which a fluid flows, a conical cylindrical part, and an annular gap located therebetween, and a part of the fluid branched into the straight cylindrical part. A second branch pipe connected to a first branch pipe, wherein the conical cylindrical portion is a conical body in which a cross-sectional area orthogonal to a flow line of the fluid decreases continuously from upstream to downstream of the fluid. Wherein the second branch pipe is connected to the annular gap,
In addition, the annular gap is located immediately after the straight cylindrical portion, is located on a cross section orthogonal to the streamline of the fluid, and joins the fluid passing through the branch pipe to the main flow path at an acute angle. . 5. The pulsation damping device according to claim 1, wherein the annular gap is a spiral groove or projection.