Broadband pressure pulsation suppression plunger, axial plunger pump and working method of axial plunger pump

Abstract

The invention discloses a broadband pressure pulsation suppression plunger, an axial plunger pump and working methods of the broadband pressure pulsation suppression plunger and the axial plunger pump. A hollow plunger cavity is formed in the plunger, a Helmholtz resonant cavity and a spring vibration absorption unit are arranged on the side wall of the plunger cavity in the axial direction, the Helmholtz resonant cavity is used for absorbing high-frequency harmonic energy, and the spring vibration absorption unit is used for absorbing low-frequency vibration energy in a graded mode. Through the synergistic effect of the Helmholtz resonant cavity and the spring vibration absorption unit, effective suppression of broadband pressure pulsation is achieved; meanwhile, the gravity and the restoring force of the spring are used for achieving active oil emptying, the problem that a traditional damping structure is prone to oil trapping is solved, and the advantages of being compact in structure, self-adaptive in response, thorough in oil discharging and the like are achieved.

Description

Technical Field

[0001] This invention belongs to the field of piston pump vibration reduction and noise reduction technology, specifically relating to a wideband pressure pulsation suppression piston and an axial piston pump and their working method. Background Technology

[0002] Axial piston pumps are the core power components of hydraulic systems. With their advantages of compact structure, high power density, and high working pressure, they are widely used in the automotive, construction machinery, and equipment manufacturing industries.

[0003] During operation, the plunger chamber periodically switches between the suction port and the discharge port as the piston reciprocates. The instantaneous changes in chamber volume and the compressibility of the oil cause backflow and pressure shocks, resulting in significant pressure pulsations. These pulsations are a major cause of vibration, noise, and fatigue damage to critical components in hydraulic systems.

[0004] Existing noise reduction measures mostly employ damping grooves on the distribution plate to passively suppress vibration by throttling and reducing the rate of pressure change. However, this approach has two major limitations: first, the damping groove dimensions are fixed, making it difficult to adapt to a wide range of speed and load variations, and it is prone to backflow or pressure overshoot under high-pressure conditions; second, it lacks targeted absorption of specific harmonics that have entered a steady state, making it difficult to achieve effective vibration suppression over a wide frequency range.

[0005] Therefore, there is an urgent need for an innovative plunger structure that can be integrated inside the plunger, has wide-band vibration absorption capabilities, and possesses adaptive adjustment functions, in order to fundamentally eliminate pressure pulsation, reduce noise, and improve system reliability. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a wideband pressure pulsation suppression plunger and an axial plunger pump and their working method, which solves the problems of narrow pressure pulsation suppression bandwidth and poor adaptability of plunger pumps in the above-mentioned background art.

[0007] The technical solution adopted by this invention to solve its technical problem is as follows: a wideband pressure pulsation suppression plunger is provided, including a plunger body, the plunger body having a hollow plunger cavity inside; at least one row of Helmholtz resonant cavities are arranged axially on the sidewall of the plunger cavity, the size of the Helmholtz resonant cavities in the same row changing sequentially; a plurality of spring vibration damping units are arranged axially on the bottom of the plunger cavity, the spring vibration damping unit including a piston, a spring and a limiting structure, the equivalent stiffness of the spring decreasing from the oil discharge end to the oil discharge end along the axial direction of the plunger cavity, so as to adapt to the working condition of large pulsation near the outlet and realize graded buffering of pressure pulsation.

[0008] In a preferred embodiment of the present invention, the Helmholtz resonant cavity includes a cavity body and a channel communicating with the plunger cavity. The centerline of the channel is located in the radial direction of the plunger cavity. The cavity body is embedded in the side wall of the plunger cavity. The dimensions of the cavity body and the channel increase sequentially from the oil suction end to the oil suction end.

[0009] In a preferred embodiment of the present invention, the structural parameters of the Helmholtz resonant cavity satisfy the Helmholtz resonant frequency formula. By designing different cavity volumes and channel sizes, its resonant frequency corresponds to the main high-frequency harmonic frequencies in oil pressure pulsations. Specifically, the calculation method for the resonant cavity parameters is as follows:

[0010] A Helmholtz resonator typically consists of a closed cavity with a finite volume and a narrow, elongated channel communicating with the outside. When external sound waves act on this structure, under low-frequency conditions (where the wavelength of the sound wave is much larger than the characteristic dimensions of the cavity and channel), the sound pressure within the cavity can be approximated as spatially uniformly distributed, and the air within the channel participates in the vibration as a whole, thus causing the system to exhibit typical single-degree-of-freedom resonant characteristics. Under the assumption of small-amplitude linear acoustics, a Helmholtz resonator can be equivalently represented as a mass-spring system, where the inertia of the air column within the channel corresponds to the equivalent mass, and the compressibility of the air within the cavity corresponds to the equivalent spring.

[0011] First, consider the equivalent mass of the air column inside the duct. Let the cross-sectional area of ​​the duct be... The geometric length is air density is Since the air at both ends of the channel exchanges momentum with the external air during vibration, the actual length of the air participating in the vibration should include an end correction. Thus, the effective channel length is defined as Under the low-frequency approximation, the air inside the channel can be considered as a rigid body reciprocating motion, and its equivalent mass can be expressed as:

[0012] .

[0013] Next, we analyze the elastic effect of the air inside the cavity. When the air inside the channel undergoes a small displacement... When this happens, it will cause a change in the volume of the cavity, and the amount of volume change is... Since the timescale of sound wave propagation is much smaller than that of heat conduction, the compression and expansion of air inside the cavity can be approximated as an adiabatic process, and its thermodynamic relationship satisfies... ,in This refers to gas pressure. Let be the adiabatic index of the gas. Linearizing this relationship near equilibrium, we obtain the relationship between pressure change and volume change within the cavity as follows:

[0014]

[0015] in For environmental static pressure, Let V be the volume of the cavity. Substituting into the above equation, we obtain the change in intracavitary pressure as follows:

[0016]

[0017] The pressure change within the cavity will act on the cross-section of the channel, thus generating a restoring force on the air column within the channel. The magnitude of this restoring force is equal to the product of the pressure change and the cross-sectional area, i.e.:

[0018]

[0019] This shows that the restoring force is related to the displacement. This is directly proportional, indicating that the compressibility of the air inside the cavity is equivalent to that of a linear spring, with an equivalent stiffness of:

[0020]

[0021] Using the relationship between the speed of sound in air and thermodynamic parameters The above stiffness expression can be further written as:

[0022]

[0023] After obtaining the equivalent mass and equivalent stiffness, the differential equations of motion for the system can be established. The dynamic equation of the air column in the duct is:

[0024]

[0025] Will and Substituting and simplifying, we get:

[0026]

[0027] This equation is the standard equation for simple harmonic motion, and its natural angular frequency is:

[0028]

[0029] Therefore, the resonant frequency of the Helmholtz resonator can be expressed as:

[0030]

[0031] The effective duct length is expressed as the sum of the geometric length and the end correction, ultimately yielding the standard form widely used in engineering and theoretical analysis:

[0032]

[0033] Let the resonant frequency The parameters of the resonant cavity can be further determined by finding the main harmonic frequency in the oil pressure pulsation, allowing the resonant cavity with different parameters to absorb oil of different frequencies. It is the resonant frequency. It's the speed of sound. It is the volume of the cavity. It is the effective length of the channel. It is the cross-sectional area of ​​the opening of the channel.

[0034] In a preferred embodiment of the present invention, a plurality of grooves are formed at the bottom of the plunger cavity, and the spring vibration damping unit is arranged in the grooves.

[0035] In a preferred embodiment of the present invention, the piston is slidably installed in the groove, the side surface of the piston facing the plunger cavity is an arc surface or a plane, and the outer diameter of the piston and the inner diameter of the groove form an interference fit to form a sealing structure, preventing oil from entering the lower space where the spring is located.

[0036] In a preferred embodiment of the present invention, the spring is disposed in a closed space on the side of the piston away from the plunger cavity, and its two ends are respectively connected to the piston and the bottom of the groove.

[0037] In a preferred embodiment of the present invention, the limiting structure includes a boss located at the bottom of the piston. The boss is made of an elastic material and is used to limit the maximum stroke of the piston and buffer impact.

[0038] In a preferred embodiment of the present invention, the groove is cylindrical, the boss is annular and designed along the inner wall of the groove, the spring passes through the hollow area of ​​the annular boss and connects to the bottom, and the piston, spring and groove are coaxially arranged.

[0039] The present invention also provides an axial piston pump, which is equipped with a wideband pressure pulsation suppression piston as described above.

[0040] The present invention also provides a method for suppressing wideband pressure pulsation, which uses the above-mentioned wideband pressure pulsation suppression plunger or axial plunger pump for oil suction and discharge in the hydraulic system.

[0041] The method of this invention utilizes the alternation of high-frequency resonance absorption and low-frequency spring damping in time and the mutual complementation in space to achieve synchronous suppression of pressure pulsations across the entire frequency band. Specifically, it includes the following steps:

[0042] S1. During the oil suction stroke of the hydraulic system, the oil enters the plunger cavity and then enters the Helmholtz resonance cavity located on the side wall of the plunger cavity.

[0043] S2. Utilizing the resonant acoustic characteristics of the Helmholtz resonant cavity at high frequency within its size variation range, the high-frequency pressure pulsation energy in the oil is converted into heat energy and dissipated.

[0044] S3. During the oil discharge stroke, the oil applies pressure to the spring damping unit located at the bottom of the plunger cavity, pushing the piston to compress the spring, and achieving graded damping of low-frequency impacts based on the gradient stiffness of the spring.

[0045] S4. At the end of the oil discharge stroke, the stored potential energy of the spring is released, so that the piston is reset under the combined action of the spring reset force and gravity, and the oil inside the spring vibration damping unit is actively discharged back to the plunger cavity to prevent dead volume oil from accumulating and to achieve active oil discharge.

[0046] Compared with the prior art, this technical solution has the following advantages:

[0047] 1. This invention utilizes a resonant cavity to capture and eliminate high-frequency harmonics, while a spring system absorbs low-frequency impacts; the two work together to achieve full-frequency band pulsation suppression.

[0048] 2. The gradient stiffness spring assembly at the bottom of the plunger cavity in this invention can automatically respond in stages according to the changes in pressure inside the plunger cavity (different speeds and loads); the hard springs are for high-pressure impacts, and the soft springs are for small fluctuations, which significantly improves the adaptability of the system under multiple working conditions.

[0049] 3. In this invention, at the end of the oil discharge stroke and at the beginning of the oil suction stroke, the oil in the resonant cavity flows back under the action of gravity and pressure; when the spring is released, the piston resets, actively draining the oil in the spring unit back into the plunger cavity, effectively eliminating dead volume oil and improving the pump's volumetric efficiency.

[0050] 4. This invention integrates all vibration damping devices into the plunger body, resulting in a compact structure that eliminates the need to modify the pump housing or distribution plate, facilitating retrofit upgrades and on-site maintenance of existing hydraulic pumps. Attached Figure Description

[0051] Figure 1 This is a structural diagram of the broadband pressure pulsation suppression plunger used in an embodiment.

[0052] Figure 2 for Figure 1 Enlarged view of section I in the middle.

[0053] Figure 3 This is a cross-sectional view of the Helmholtz resonant cavity in the embodiment.

[0054] Figure 4 This is a cross-sectional view of the spring vibration damping unit in the embodiment.

[0055] Figure 5 This is a flowchart illustrating the working method of an embodiment.

[0056] Figure 6 This is a comparison chart of the pressure pulsation suppression effects of the example and existing technologies.

[0057] Figure descriptions: 1. Plunger body; 2. Plunger cavity; 3. Helmholtz resonant cavity; 4. Cavity; 5. Channel; 6. Spring vibration damping unit; 7. Piston; 8. Spring; 9. Limiting structure. Detailed Implementation

[0058] In the following description of the embodiments, the terms "top," "bottom," "inner," "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0059] Example

[0060] like Figure 1 This embodiment is a broadband pressure pulsation suppression plunger integrating a resonant cavity and a spring vibration damping unit. It includes a plunger body 1 and an axially penetrating plunger cavity 2 inside it. At the top of the plunger cavity 2, a row of Helmholtz resonant cavities 3 are arranged axially. At the bottom of the plunger cavity 2, a number of spring vibration damping units 6 are arranged axially.

[0061] like Figure 1 and Figure 3 In this embodiment, multiple Helmholtz resonant cavities 3 are arranged along the plunger axis, and each Helmholtz resonant cavity 3 is composed of a cavity 4 and a channel 5. The channel 5 directly connects the cavity 4 and the plunger cavity 2, and the cavity 4 and the channel 5 are positioned coaxially. The dimensions of the cavity 4 or the channel 5 of each resonant cavity 3 are not exactly the same to correspond to different vibration absorption frequencies. The structural parameters of the Helmholtz resonant cavity satisfy the Helmholtz resonant frequency formula. By designing different cavity volumes and channel dimensions, their resonant frequencies correspond to the main high-frequency harmonic frequencies in oil pressure pulsations.

[0062] ;

[0063] in, It is the resonant frequency. It's the speed of sound. This is the volume of cavity 4. It is the effective length of channel 5. It is the cross-sectional area of ​​the opening of channel 5.

[0064] like Figure 2 and Figure 4The spring-loaded vibration damping unit 6 is disposed in a cylindrical groove at the bottom of the plunger cavity. Each spring-loaded vibration damping unit 6 includes a piston 7, a spring 8, and a limiting structure 9. The piston 7 is slidably installed in the groove, and its side facing the plunger cavity 2 is an arc surface or a flat surface. The outer surface and the inner wall of the groove are press-fitted to form a reliable seal, effectively preventing oil from entering the lower space where the spring 8 is located. The piston 7 is made of a material with high sealing performance, high wear resistance, and resistance to oil corrosion to ensure the sealing reliability and durability of long-term operation. The spring 8 is disposed on the side of the piston 7 away from the plunger cavity 2, and its two ends are respectively connected to the bottom surface of the piston 7 and the bottom of the groove. Along the plunger axis, the stiffness of the springs 8 in the multiple spring-loaded vibration damping units 6 decreases sequentially towards the oil discharge end to adapt to the working condition of large pressure pulsation at the outlet. When the pressure in the plunger cavity 2 increases, the preload of different springs 8 can be overcome sequentially according to the pressure value, pushing the corresponding piston 7 to compress the springs 8 in stages, realizing adaptive buffering and vibration absorption of low-frequency pressure pulsation. The limiting structure 9 is an annular boss made of elastic material located at the bottom of the spring-loaded vibration-absorbing unit 6. It is used to limit the maximum displacement of the piston 7 and buffer the impact of the piston 7. The spring 8 passes through the hollow area of ​​the annular boss and connects to the bottom. The piston 7, spring 8, and limiting structure 9 are coaxially positioned and fixed as a whole.

[0065] In this embodiment, four Helmholtz resonant cavities 3 with gradually varying sizes are arranged axially at the top of the plunger cavity 2. Each Helmholtz resonant cavity 3 consists of a cylindrical cavity 4 and a cylindrical channel 5 coaxially connected to it, and is positioned and fixed coaxially. The dimensions of the four resonant cavities increase sequentially from left to right, with the following specific parameters: the radii of the cavity 4 are 0.75mm, 1mm, 1.25mm, and 1.5mm, and the heights are 1mm, 1.1mm, 1.2mm, and 1.3mm, respectively; the radii of the channel 5 are 0.25mm, 0.3mm, 0.35mm, and 0.45mm, and the depths are 0.75mm, 0.85mm, 0.95mm, and 1.05mm, respectively. Each Helmholtz resonant cavity 3 is independent of each other and is evenly distributed axially, with a center-to-center distance of 1mm between adjacent channels 5. Three spring-loaded vibration-absorbing units 6 are arranged axially at the bottom of the plunger cavity 2. Each spring-loaded vibration damping unit 6 is located within a cylindrical groove with a radius of 2.5 mm and a depth of 3 mm. The center distance between adjacent spring-loaded vibration damping units 6 is 12.5 mm. Each spring-loaded vibration damping unit 6 consists of a piston 7, a spring 8, and a limiting structure 9. The piston 7 has an arc-shaped structure, and its outer diameter is interference-fitted with the inner diameter of the spring-loaded vibration damping unit 6. It is made of a material with high sealing performance, high wear resistance, and resistance to oil corrosion, ensuring a reliable seal between the piston 7 and the inner wall of the spring-loaded vibration damping unit 6, preventing oil from entering the lower space of the spring-loaded vibration damping unit 6. The bottom surface of the piston 7 is connected to the spring 8. The stiffness coefficients of the three springs 8 decrease sequentially from left to right along the piston axis, being 12 N / mm, 10 N / mm, and 8 N / mm, respectively. The lower end of the spring 8 is inserted into the bottom of the cavity of the spring-loaded vibration damping unit 6 and is positioned and fixed coaxially. The limiting structure 9 is an annular boss located at the bottom of the spring vibration damping unit 6. The ring is 0.85mm wide and 0.5mm thick, and is made of elastic material. It is used to limit the maximum stroke of the piston 7 and to buffer the impact of the piston 7 by its own elastic deformation.

[0066] In this embodiment, the plunger is applied to an axial plunger pump, enabling wide-band pressure pulsation suppression in the hydraulic system. The specific working method is as follows: During oil suction, the oil enters the plunger chamber 2 and flows into the Helmholtz resonant chamber 3. Through resonance, the main high-frequency harmonic energy is converted into heat dissipation. Simultaneously, the oil enters the spring-absorbing unit 6, which overcomes different spring preloads according to the pressure magnitude, pushing the piston 7 to compress the corresponding spring 8 to absorb low-frequency vibrations. The piston stroke is limited by the limiting structure 9. During oil discharge, the oil in the Helmholtz resonant chamber 3 flows back under the action of pressure and gravity. At the end of the discharge, the spring 8 releases energy to push the piston 7 to reset, discharging the oil in the spring-absorbing unit 6 back to the plunger chamber 2, avoiding trapped oil residue. Ultimately, through the synergistic effect of resonance absorption and spring buffering, wide-band pressure pulsation suppression is achieved.

[0067] Figure 6This figure compares the pressure pulsation suppression performance of the wideband pressure pulsation suppression plunger in this embodiment with that of a conventional plunger. The data in the figure shows that, within the indicated frequency range, the pressure pulsation amplitude of the plunger in this embodiment remains at a low level overall, especially at most test frequencies where it remains below 0.1 MPa, indicating its excellent pressure pulsation suppression performance. This result demonstrates that the integrated Helmholtz resonant cavity and gradient stiffness spring vibration-absorbing unit structure used in this invention can work synergistically across a wide frequency range. Through the combination of resonant absorption and graded buffering, it achieves suppression of wide-range pressure pulsation, thereby significantly improving the system's pressure stability and operational smoothness.

[0068] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A broadband pressure pulsation suppression plunger, characterized in that: The device includes a plunger body, the plunger body having a hollow plunger cavity inside; at least one row of Helmholtz resonant cavities are arranged axially on the sidewall of the plunger cavity, the size of the Helmholtz resonant cavities in the same row changing sequentially; several spring damping units are arranged axially on the bottom of the plunger cavity, each spring damping unit including a piston, a spring and a limiting structure, the equivalent stiffness of the spring decreasing along the axial direction of the plunger cavity from the oil discharge end to the oil discharge end.

2. The broadband pressure pulsation suppression plunger according to claim 1, characterized in that: The Helmholtz resonant cavity includes a cavity body and a channel communicating with the plunger cavity. The centerline of the channel is located in the radial direction of the plunger cavity. The cavity body is embedded in the side wall of the plunger cavity. The dimensions of the cavity body and the channel increase sequentially from the oil suction end to the oil suction end.

3. The broadband pressure pulsation suppression plunger according to claim 2, characterized in that, The structural parameters of the Helmholtz resonant cavity satisfy the following relationship: ； in, It is the resonant frequency. It's the speed of sound. It is the volume of the cavity. It is the effective length of the channel. It is the cross-sectional area of ​​the opening of the channel.

4. The broadband pressure pulsation suppression plunger according to claim 1, characterized in that: Several grooves are formed at the bottom of the plunger cavity, and the spring vibration damping unit is arranged in the grooves.

5. A broadband pressure pulsation suppression plunger according to claim 4, characterized in that: The piston is slidably installed in the groove, and the side surface of the piston facing the plunger cavity is an arc surface or a plane. The outer diameter of the piston and the inner diameter of the groove form an interference fit.

6. A broadband pressure pulsation suppression plunger according to claim 4, characterized in that: The spring is located in a closed space on the side of the piston away from the plunger cavity, and its two ends are connected to the piston and the bottom of the groove, respectively.

7. A broadband pressure pulsation suppression plunger according to claim 4, characterized in that: The limiting structure includes a boss located at the bottom of the piston, the boss being made of an elastic material.

8. An axial piston pump, characterized in that: The device is equipped with a broadband pressure pulsation suppression plunger as described in any one of claims 1 to 7.

9. A method for suppressing broadband pressure pulsation, characterized in that: The hydraulic system uses a wideband pressure pulsation suppression plunger as described in any one of claims 1 to 7 or an axial plunger pump as described in claim 8 for oil suction and discharge.

10. A method for suppressing broadband pressure pulsation according to claim 9, characterized in that, Includes the following steps: S1. During the oil suction stroke of the hydraulic system, the oil enters the plunger cavity and then enters the Helmholtz resonance cavity located on the side wall of the plunger cavity. S2. Utilizing the resonant acoustic characteristics of the Helmholtz resonant cavity at high frequency within its size variation range, the high-frequency pressure pulsation energy in the oil is converted into heat energy and dissipated. S3. During the oil discharge stroke, the oil applies pressure to the spring damping unit located at the bottom of the plunger cavity, pushing the piston to compress the spring, and achieving graded damping of low-frequency impacts based on the gradient stiffness of the spring. S4. At the end of the oil discharge stroke, the stored potential energy of the spring is released, so that the piston is reset under the combined action of the spring reset force and gravity, and the oil inside the spring vibration damping unit is actively discharged back to the plunger cavity to prevent dead volume oil from accumulating and to achieve active oil discharge.

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