Variable frequency compressor oil pumping amount adaptive regulation structure

Abstract

This invention provides an adaptive oil flow adjustment structure for a variable frequency compressor, relating to the field of compressor technology. It includes a crankshaft, a flow-limiting device, a spring, a limiting ring, and an oil pump. The crankshaft has a through-hole extending along its axis at its center, and a cylindrical cavity with a diameter larger than the oil hole is machined at its lower end. The flow-limiting device is coaxially disposed within the cavity, forming an annular step between the oil hole and the cavity. Multiple countersunk holes, each corresponding to a specific location, are evenly distributed circumferentially on the lower surface of the annular step and the upper surface of the flow-limiting device, forming an installation space. The spring is disposed within the installation space, with its two ends abutting against the bottom of the countersunk holes of the annular step and the bottom of the countersunk holes of the flow-limiting device, respectively. The outer wall of the flow-limiting device is clearance-fitted with the inner wall of the cavity, and the flow-limiting device can move axially up and down. A limiting ring is located below the flow-limiting device and is fixed to the inner wall of the crankshaft cavity. The lower end of the crankshaft is connected to the oil pump via a connecting structure. This invention provides feedback adjustment entirely based on the real-time speed of the compressor.

Description

Technical Field

[0001] This invention relates to the field of compressor technology, and more particularly to an adaptive oil pump quantity adjustment structure for a variable frequency compressor, used in the lubrication system of a vertical variable frequency compressor. Background Technology

[0002] Variable frequency compressors are widely used in modern refrigeration and air conditioning systems due to their high energy efficiency and wide adjustment range. Their operating speed can vary continuously over a large range to adapt to different load demands. However, this significant speed variation poses challenges to the compressor's lubrication system.

[0003] Compressor lubrication typically relies on an oil pump, which is usually directly driven by the compressor crankshaft. In traditional fixed-speed or limited-range compressors, the oil pump's oil supply capacity is designed primarily for rated operating conditions. However, for variable-frequency compressors, when operating at low speeds (low frequencies), the crankshaft speed is low, and the oil pump's pumping capacity decreases significantly. This can lead to insufficient oil delivery to the compressor's friction pairs (such as bearings and scroll plates), resulting in poor lubrication, increased wear, and even crankshaft seizure, severely impacting compressor reliability. Conversely, when the compressor operates at high speeds (high frequencies), excessive oil pumping can cause excessive refrigerant oil to circulate within the system. This not only increases compressor power consumption and reduces system energy efficiency but can also lead to decreased heat exchange efficiency and "oil stagnation" problems, where oil cannot easily return to the compressor. Long-term operation with excessive oil can also cause compressor damage due to oil shortage.

[0004] In existing technologies, some improved solutions exist to address the fuel supply contradiction at high and low speeds, such as using a variable displacement oil pump or adding an external pressure regulating valve. However, variable displacement oil pumps are complex in structure and expensive; while external pressure regulating valves have slow response and increase system complexity and leakage points. Additionally, there are solutions using fixed orifices in the oil circuit, but these cannot adapt to wide speed range variations, and the throttling effect is too strong at low speeds, exacerbating insufficient fuel supply. The flow characteristics of a fixed orifice can be simplified as follows:

[0005]

[0006] in, For traffic, For flow coefficient, For fixed circulation area, For pressure difference, Let be the oil density. It can be seen that under low speed and low pressure differential conditions, the flow rate... The significant reduction exacerbates the fuel shortage.

[0007] Therefore, it is essential to have a simple, fast-responding pump oil volume adaptive adjustment device that can be integrated into the compressor crankshaft system and automatically adjust the flow cross section according to the speed (oil pressure). Summary of the Invention

[0008] Based on the aforementioned technical problems encountered when variable frequency compressors operate over a wide speed range, traditional fixed oil pumps or existing adjustment schemes struggle to balance insufficient oil supply at low speeds and excessive oil supply at high speeds, leading to poor lubrication, reduced energy efficiency, and compromised reliability. This invention provides an adaptive oil quantity adjustment structure for variable frequency compressors. Integrated within the crankshaft, this invention utilizes the characteristic of oil pump outlet pressure varying with speed to automatically adjust the lubricating oil flow channel area, thereby achieving adaptive oil quantity balance. This ensures the compressor receives appropriate oil quantity across the entire speed range, balancing reliable lubrication at low speeds with energy efficiency at high speeds.

[0009] The technical means employed in this invention are as follows: An adaptive adjustment structure for oil pump volume of a variable frequency compressor includes a crankshaft, a flow limiting device, a spring, a limiting ring, and an oil pump; The crankshaft has a through-hole extending along its axis at its center, and a cylindrical cavity with a diameter larger than the oil hole is machined at its lower end. A flow-limiting device is coaxially disposed within the cavity, forming an annular step between the oil hole and the cavity. Multiple countersunk holes, each corresponding to a specific location, are evenly distributed circumferentially on the lower surface of this annular step and the upper surface of the flow-limiting device, forming an installation space. A spring is disposed within this installation space, with its two ends abutting against the bottom of the countersunk holes in the annular step and the bottom of the countersunk holes in the flow-limiting device, respectively. The outer wall of the flow-limiting device is clearance-fitted with the inner wall of the cavity, and the flow-limiting device can move axially up and down. A limiting ring is located below the flow-limiting device and is fixed to the inner wall of the crankshaft cavity. The lower end of the crankshaft is connected to the oil pump via a connecting structure. The spring is a compression spring, with a free length greater than the depth of the installation space, ensuring the spring remains in a pre-compressed state after installation. The flow-limiting device is a solid cylinder with multiple axially penetrating oil flow channels on its circumferential side. The guide portion of the flow limiting device forms a limiting structure with the crankshaft circumferential limiting surface to restrict the circumferential rotation of the flow limiting device.

[0010] Furthermore, the central part of the flow limiting device is a solid body, and the upper surface of the solid body is machined with multiple evenly distributed countersunk holes.

[0011] Furthermore, the main body of the flow limiting device has a cross-shaped cross section, and the outer diameter of the four flanges of the cross shape is in clearance fit with the inner diameter of the crankshaft cavity.

[0012] Furthermore, the flow limiting device is a star-shaped structure with a star-shaped cross-section and six radial protrusions evenly distributed thereon, and the radial protrusions are in clearance fit with the inner diameter of the crankshaft cavity.

[0013] Furthermore, the limiting ring is an elastic retaining ring, a retaining ring, or an annular component pressed into the crankshaft cavity through an interference fit.

[0014] Compared with the prior art, the present invention has the following advantages: Adaptive adjustment: It adjusts based entirely on the real-time speed (oil pressure) of the compressor, without the need for external control signals or complex mechanisms, thus achieving true self-adaptation.

[0015] Simple and reliable structure: All adjusting components are integrated inside the crankshaft, without increasing the external size and complexity of the compressor. Few moving parts, only the axial movement of the flow limiting device, resulting in high reliability.

[0016] Improved low-speed lubrication: Ensures minimal oil circuit resistance under low speed and low oil pressure conditions, prioritizes the supply of basic lubricating oil, and avoids the risk of low-speed oil shortage.

[0017] Optimized high-speed performance: Automatic throttling at high speeds avoids power loss and system oil return problems caused by excessive pumping oil, improving energy efficiency and operational stability under high loads.

[0018] High versatility: The structure has a clear principle and can be adapted to variable frequency compressors with different displacements and speed ranges by adjusting parameters such as spring stiffness, preload, and shape of the flow limiting device. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the overall axial cross-section assembly of the structure in this embodiment.

[0021] Figure 2 This is a three-dimensional sectional view of the crankshaft in this embodiment, showing the internal oil holes, annular stepped countersunk holes, and lower cavity structure.

[0022] Figure 3 This is a three-dimensional structural diagram of the current limiting device in Example 1, showing its cross-sectional shape and the countersunk hole on the upper end face.

[0023] Figure 4 This is a schematic diagram of the limiting ring in this embodiment.

[0024] Figure 5 This is a three-dimensional structural diagram of the oil pump outlet portion in this embodiment.

[0025] Figure 6 This is a schematic diagram of the crankshaft and the circumferential limiting device.

[0026] Figure 7 This is a schematic diagram of the current limiting device in Example 2.

[0027] In the diagram: 100, crankshaft; 101, oil hole; 102, first countersunk hole; 103, cavity; 104, crankshaft circumferential limiting surface; 200, flow limiting device; 201, second countersunk hole; 202, guide part; 300, spring; 400, limiting ring; 500, oil pump; 501, oil pump outlet. Detailed Implementation

[0028] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0031] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0032] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0033] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0034] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0035] like Figure 1-6As shown, the present invention provides a vertical variable frequency compressor oil pump quantity adaptive adjustment structure, including: crankshaft 100, flow limiting device 200, spring 300, limit ring 400, and oil pump 500.

[0036] The crankshaft 100 is the core rotating component of the compressor. It has an oil hole 101 that runs vertically through the center along the axis, which is used to guide the lubricating oil delivered by the oil pump 500 to the upper bearing and other parts that need lubrication.

[0037] At the lower end of the crankshaft 100, a cylindrical cavity 103 with a diameter larger than that of the oil hole 101 is formed by machining and enlarging. The flow limiting device 200 is coaxially disposed within this cavity 103. The outer wall of the flow limiting device 200 and the inner wall of the cavity 103 are fitted with a clearance fit, allowing the flow limiting device 200 to move freely up and down axially within the cavity 103. To achieve circumferential limiting, the cross-section of the flow limiting device is designed to be non-circular (such as cross-shaped or star-shaped), and anti-rotation is achieved by utilizing the fit between its outer edge and the cylindrical cavity 103.

[0038] At the junction of the oil hole 101 and the cavity 103, a ring-shaped step is naturally formed. Multiple first countersunk holes 102 are uniformly machined along the circumference on the lower surface of this ring-shaped step. Multiple second countersunk holes 201, precisely corresponding to the positions of the first countersunk holes 102, are uniformly distributed along the circumference on the upper surface of the flow-limiting device 200. The first countersunk holes 102 and the second countersunk holes 201 form an installation space for the spring 300. The two ends of the spring 300 abut against the bottom of the first countersunk holes 102 of the ring-shaped step and the bottom of the second countersunk holes 201 of the flow-limiting device 200, respectively. The spring 300 is a stainless steel compression spring, and its free length is greater than the depth of the installation space. Therefore, it is always in a pre-compressed state after installation, applying a downward elastic force to the flow-limiting device 200. The total spring stiffness k and the pre-compression amount x0 are determined according to the design oil pressure range. For example, if the target minimum operating oil pressure is Pmin, then k·x0≈Pmin·Ap-Fg must be satisfied, where Ap is the effective pressure-bearing area of ​​the flow-limiting device, and Fg is the weight of the flow-limiting device.

[0039] A limiting ring 400 is provided below the flow limiting device 200. The limiting ring 400 is an elastic steel wire retaining ring, installed in an annular groove machined near the bottom of the inner wall of the crankshaft cavity 103. When the flow limiting device 200 is not subjected to sufficiently large upward oil pressure, it falls to its lowest position under the action of the spring 300, and its lower surface abuts against the limiting ring 400. The limiting ring 400 is used to block the flow limiting device 200 and defines its lowest downward position (i.e., the maximum opening position).

[0040] Oil pump 500 is installed below crankshaft 100 to provide lubrication power to compressor. Oil pump 500 is an internal gear pump, which is screwed into the threaded section at the lower end of crankshaft 100 through its central threaded hole. Oil pump outlet 501 of oil pump 500 is aligned with the lower inlet of crankshaft oil hole 101.

[0041] The crankshaft 100 and the oil pump 500 can be connected by thread or flange bolts to ensure power transmission and oil circuit sealing.

[0042] Example 1: The flow limiting device 200 is made of powder metallurgy or machined. Its main body cross-section is designed in a cross shape. The outer diameter of the four flanges of the cross shape is clearance-fitted with the inner diameter of the crankshaft cavity 103, which can ensure smooth up and down movement and effectively prevent the flow limiting device 200 from rotating. The central part of the flow limiting device 200 is a solid body. On the upper end face of the flow limiting device 200, corresponding to the four first countersunk holes 102 on the annular step of the crankshaft 100, four second countersunk holes 201 are also machined. Four springs 300 are respectively installed in the installation space formed by the first countersunk holes 102 and the second countersunk holes 201.

[0043] Example 2: The flow limiting device 200 has a star-shaped structure with six radially distributed protrusions in its cross-section to provide a more uniform throttling effect and better guidance. Accordingly, the number of the first countersunk hole 102 and the second countersunk hole 201 is also changed to six, and six springs 300 are installed to match them.

[0044] The limiting ring 400 can also be replaced with a copper or steel annular gasket that is press-fitted into the crankshaft cavity 103. The connection between the crankshaft 100 and the oil pump 500 can be achieved by flange fitting and bolt fastening, with a sealing ring installed on the connection surface to enhance sealing reliability.

[0045] Working principle: When the compressor starts and runs at low speed, the oil pump 500 operates at a low speed, resulting in relatively low oil pressure. The upward oil pressure acting on the lower surface of the flow restrictor 200 is also relatively low. At this time, the sum of the preload of the spring 300 and the weight of the flow restrictor 200 is greater than the upward oil pressure. The flow restrictor 200 is pressed into its lowest position, i.e., in contact with the limiting ring 400. At this time, the gap between the upper surface of the flow restrictor 200 and the lower end face of the crankshaft oil hole 101 outlet is at its maximum, or the annular channel area formed by the side wall of the flow restrictor 200 and the inner wall of the oil hole 101 is at its maximum, resulting in minimal oil flow resistance. Lubricating oil can flow relatively smoothly, ensuring sufficient oil volume for upward lubrication even at low speeds.

[0046] As the compressor speed increases, the oil pump 500 speed increases synchronously, leading to an increase in outlet oil pressure. The upward oil pressure acting on the lower surface of the flow-limiting device 200 also increases accordingly. When the oil pressure exceeds the sum of the spring force and the weight of the flow-limiting device 200, the flow-limiting device 200 begins to move upward against the spring force. As the flow-limiting device 200 moves upward, the effective area blocking the oil hole 101 increases (for example, the upper conical or cylindrical surface of the flow-limiting device enters the oil hole, or the lateral channel narrows), causing the lubricating oil flow cross-section to gradually decrease and the flow resistance to increase. This essentially creates a dynamic throttling effect.

[0047] Work process: When the compressor starts at a low frequency of 30Hz, the oil pump speed is low, and the oil pressure is approximately 0.15MPa. This oil pressure exerts a small upward force, Foil=P·Ap, on the bottom surface of the flow restrictor 200. P is the oil pump outlet pressure, which cannot overcome the spring force Fs=k·(x0+x) and the flow restrictor's own weight Fg, where x is the upward displacement of the flow restrictor from its lower limit position. The flow restrictor remains at its lower limit position (x=0), forming four large fan-shaped flow channels between its cross-shaped flange and the crankshaft oil hole 101 outlet. The flow area Af=Amax, resulting in low oil flow resistance and ensuring a basic oil supply at low speeds.

[0048] When the compressor operates at a high frequency of 90Hz, the oil pump 500 speed triples, and the oil pressure rises to approximately 0.5MPa. This oil pressure (Foil) is significantly greater than the sum of the spring preload and the weight of the flow-limiting device 200, pushing the flow-limiting device 200 upward by approximately 3mm (i.e., x=3mm). As the flow-limiting device 200 moves upward, the upper part of its cross-shaped flange gradually enters the lower region of the oil hole 101, effectively blocking part of the flow channel and reducing the flow area by approximately 60%, i.e., Af(x)≈0.4Amax. The resulting throttling effect controls the upward oil volume at a reasonable level matching the high-frequency operation, avoiding excessive pumping. During this process, the change in flow rate Q with speed is smoothed out due to the decrease in Af.

[0049] The adaptive adjustment mechanism of this structure can be described by the following mechanical and fluid relationship: Equations of force balance: When the current limiting device 200 is in axial force equilibrium, it satisfies the following:

[0050] in, This refers to the oil pump outlet pressure. The effective pressure-bearing area of ​​the current-limiting device. For the total stiffness of the spring, This is the spring pre-compression amount. This refers to the upward displacement of the current limiting device from the lower limit position. The weight of the current limiting device.

[0051] Relationship between oil pressure and speed: For positive displacement oil pumps, the outlet oil pressure is approximately proportional to the square of the rotational speed:

[0052] in, This refers to the crankshaft (oil pump) angular velocity.

[0053] Relationship between flow area and displacement: Circulation area Displacement with current limiting device change:

[0054] This represents the maximum flow area when the current limiting device is at its lower limit. It is a function of the blocking area caused by displacement, and its form depends on the specific geometry of the current limiting device.

[0055] By adjusting the flow rate of the structure: Ignoring local losses, the flow rate through the regulating structure can be expressed as:

[0056] in, For flow coefficient, This is the upstream reference pressure (such as atmospheric pressure or low-pressure side pressure). This refers to the density of the lubricating oil.

[0057] Solving the above equations simultaneously, we can see that when the rotational speed... Changes cause oil pressure Displacement of the current limiting device during changes The corresponding adjustments will change the circulation area. Ultimately, traffic is achieved. Its adaptive adjustment keeps it stable within a reasonable range at different speeds.

[0058] Finally, under a certain high-speed operating condition, the flow-limiting device 200 moves upward to contact the top of the crankshaft cavity 103, reaching its upward limit position. At this time, the flow cross-section is reduced to a minimum, maximizing the throttling of the oil volume and preventing excessive oil pumping. The entire process is dynamically balanced: the oil pressure, spring force, and the device's own weight adjust the position of the flow-limiting device in real time according to the speed, thereby automatically controlling the amount of oil pumped to the upper part of the compressor within a reasonable range.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; 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; and these 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 variable frequency compressor oil pump quantity adaptive adjustment structure, characterized in that, This includes the crankshaft, flow restrictor, spring, limit ring, and oil pump; The crankshaft has a through-hole extending along its axis at its center, and a cylindrical cavity with a diameter larger than the oil hole is machined at its lower end. A flow-limiting device is coaxially disposed within the cavity, forming an annular step between the oil hole and the cavity. Multiple countersunk holes, each corresponding to a specific location, are evenly distributed circumferentially on the lower surface of this annular step and the upper surface of the flow-limiting device, forming an installation space. A spring is disposed within this installation space, with its two ends abutting against the bottom of the countersunk holes in the annular step and the bottom of the countersunk holes in the flow-limiting device, respectively. The outer wall of the flow-limiting device is clearance-fitted with the inner wall of the cavity, and the flow-limiting device can move axially up and down. A limiting ring is located below the flow-limiting device and is fixed to the inner wall of the crankshaft cavity. The lower end of the crankshaft is connected to the oil pump via a connecting structure. The spring is a compression spring, with a free length greater than the depth of the installation space, ensuring the spring remains in a pre-compressed state after installation. The flow-limiting device is a solid cylinder with multiple axially penetrating oil flow channels on its circumferential side. The guide portion of the flow limiting device forms a limiting structure with the crankshaft circumferential limiting surface to restrict the circumferential rotation of the flow limiting device.

2. The variable frequency compressor oil pump quantity adaptive adjustment structure according to claim 1, characterized in that, The central part of the flow limiting device is a solid body, and the upper surface of the solid body is machined with multiple evenly distributed countersunk holes.

3. The variable frequency compressor oil pump quantity adaptive adjustment structure according to claim 2, characterized in that, The main body of the flow limiting device has a cross-shaped cross section, and the outer diameter of the four flanges of the cross shape is in clearance fit with the inner diameter of the crankshaft cavity.

4. The variable frequency compressor oil pump quantity adaptive adjustment structure according to claim 2, characterized in that, The flow limiting device is a star-shaped structure with a star-shaped cross-section and six radial protrusions evenly distributed thereon. The radial protrusions are in clearance fit with the inner diameter of the crankshaft cavity.

5. The variable frequency compressor oil pump quantity adaptive adjustment structure according to claim 1, characterized in that, The limiting ring is an annular component that is pressed into the crankshaft cavity by an interference fit.

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