A synchronous unloading structure for gear pump single and double tooth oil trapping

Abstract

The application provides a synchronous unloading structure for single-tooth and double-tooth oil trapping of a gear pump, two stepped unloading grooves are arranged on the inner side surfaces of two end plates as symmetrical surfaces of vertical surfaces, and each stepped unloading groove is a mirror-symmetrical shape with a flow direction surface as a symmetrical surface; each stepped unloading groove comprises a rectangular deep groove and a rectangular shallow groove which are communicated with each other, and the depth of the rectangular shallow groove is smaller than that of the rectangular deep groove; the rectangular shallow groove is located on one side of the rectangular deep groove which faces the vertical surface; and one side of each stepped unloading groove which is away from the vertical surface penetrates the outer circumferential surface of the end plate. The synchronous unloading structure can sufficiently reduce the pressure amplitude and the peak-to-peak value of the single-tooth and double-tooth oil trapping regions, so that the maximum single-tooth oil trapping pressure is reduced by 35.2%, the maximum double-tooth oil trapping pressure is reduced by 45.2%, and the oil trapping phenomenon of the gear pump is fully and sufficiently relieved. In addition, by using the application, the input power of the gear pump can be reduced by about 5.4% and the output flow can be improved while the oil trapping phenomenon is relieved.

Description

Technical Field

[0001] This application belongs to the field of gear pumps, and specifically relates to a synchronous unloading structure for single and double gear oil trapping in gear pumps. Background Technology

[0002] Gear pumps are positive displacement pumps that achieve liquid transport or pressurization through changes and movement of their working volume. Based on their driving method, gear pumps are divided into external gear pumps and internal gear pumps. The commonly referred to "general gear pump" refers to an external gear pump. During the operation of an involute gear pump (a common type of external gear pump), the two meshing points on the working surface of the gears and the side clearance (usually a large side clearance) on the non-working surface together form a closed space. The volume of this space changes periodically with the rotation of the gears, causing some hydraulic oil to become trapped within it; this is called trapped oil. The rate of change of its volume is called the trapped oil flow rate, and the trapped oil pressure rises and falls periodically accordingly; this is the "trapped oil phenomenon." The trapped oil phenomenon severely affects the working performance of gear pumps and shortens their service life, becoming a key bottleneck restricting the development of gear pump technology. To address the problem of trapped oil, the commonly used solution in existing technologies is to install unloading grooves on the front and rear plates of the pump body. Among these, the double rectangular unloading grooves (referred to as double rectangular unloading grooves) arranged symmetrically about the center line are the most widely used and can alleviate the trapped oil phenomenon to a certain extent.

[0003] Existing research has confirmed that there are two types of oil trapping phenomena in gear pumps: one is the "double (meshing) tooth oil trapping phenomenon," which is formed by the closure of two meshing points and one non-working surface side clearance; the other is the "single (meshing) tooth oil trapping phenomenon," which is formed by the closure of one meshing point and two non-working surface side clearances. Currently, the industry pays very little attention to the single tooth oil trapping phenomenon. Existing structural innovations and optimization designs of unloading grooves are all focused on the double tooth oil trapping phenomenon, failing to effectively alleviate the single tooth oil trapping phenomenon, resulting in the oil trapping problem in gear pumps not being completely solved.

[0004] Therefore, it is necessary to develop an unloading structure that can solve the oil trapping phenomenon of single teeth, especially that can adapt to both single-tooth and double-tooth oil trapping phenomena, in order to further solve the oil trapping problem of gear pumps. Utility Model Content

[0005] To address the problem of significant oil trapping in gear pumps due to insufficient attention paid to single-tooth oil trapping in existing technologies, this application proposes a synchronous unloading structure for single and double-tooth oil trapping in gear pumps. The structure includes a drive gear shaft, a drive gear integrally formed on the drive gear shaft, a driven gear shaft, a driven gear integrally formed on the driven gear shaft, and two end plates, a front end plate and a rear end plate. The drive gear and driven gear are collectively referred to as gears. Both ends of the drive gear shaft and driven gear shaft are rotatably mounted in shaft holes of one end plate. A tooth end gap exists between the gear end face and the inner surface of the adjacent end plate. The drive gear and driven gear mesh with each other and together form a gear pair. The midpoint of the line connecting the center lines of the two shaft holes on the inner surface of the rear end plate is represented by O. An XYZ rectangular coordinate system is constructed with O as the origin. The XOY plane is called the flow plane, and the XOZ plane is called the vertical plane. The thickness direction of the end plate extends along the X-axis. The central axes of the drive gear shaft and driven gear shaft are parallel to each other and both lie within the vertical plane.

[0006] Two stepped unloading grooves are provided on the inner side of each end plate with the vertical plane as the plane of symmetry. The stepped unloading grooves are formed by the indentation of the inner side of the end plate along the X-axis, and each stepped unloading groove is mirror-symmetrical with the flow plane as the plane of symmetry. Each stepped unloading groove includes an interconnected rectangular deep groove and a rectangular shallow groove, and the depth of the rectangular shallow groove is less than the depth of the rectangular deep groove. In the same stepped unloading groove, the rectangular shallow groove is located on the side of the rectangular deep groove facing the vertical plane. The side of each stepped unloading groove away from the vertical plane penetrates the outer periphery of the end plate.

[0007] In a gear pump, the driving gear and driven gear have the same structure and dimensions. The driving gear and its shaft can be either separate or integrated. Similarly, the driven gear and its shaft can also be either separate or integrated. This application preferably adopts an integrated structure for both the driving gear and its shaft, and for both the driven gear and its shaft.

[0008] Because two stepped unloading grooves are set on the same end plate, it is called a double-stepped unloading groove structure. The rectangular deep groove is the double-tooth oil trapping unloading groove in the prior art, which uses the orifice flow method in fluid mechanics through the groove area to alleviate the oil trapping of the double tooth as the main method and the oil trapping of the single tooth as the auxiliary method. On this basis, the rectangular shallow groove of the stepped unloading groove is the single-tooth oil trapping unloading groove, which mainly uses the gap flow method of two parallel flat plates in the shallow groove depth area to further alleviate the oil trapping of the single tooth as the main method and the oil trapping of the double tooth as the auxiliary method.

[0009] The double-step unloading groove structure can significantly reduce the pressure amplitude and peak-to-peak value in the oil-trapping regions of single and double teeth, resulting in a 35.2% reduction in maximum oil-trapping pressure for single teeth and a 45.2% reduction for double teeth, thus comprehensively and effectively alleviating the oil-trapping phenomenon in gear pumps. Furthermore, this application, while alleviating the oil-trapping phenomenon, can also reduce the input power of the gear pump by approximately 5.4% and slightly increase the output flow rate, providing a new technical approach for optimizing gear pump performance.

[0010] Furthermore, each end plate is mirror-symmetrical about the flow plane and also mirror-symmetrical about the vertical plane. That is, all structures on the same end plate are symmetrical about both the flow plane and the vertical plane to meet the matching requirement that the gear pair and its oil-trapping area are also symmetrical about both the flow plane and the vertical plane.

[0011] Specifically, the two end plates have identical structures and are mounted on both sides of the gear pair in a mirror-symmetrical manner. This design doubles the oil trapping and unloading capacity.

[0012] Furthermore, within the same stepped unloading groove, the rectangular shallow groove and the rectangular deep groove have the same width along the Z-axis, and the width of both the rectangular shallow groove and the rectangular deep groove along the Z-axis is 1.2 to 1.5 times the tooth height of the gear. This design ensures that the unloading groove completely covers the entire trapped oil area along the Z-axis.

[0013] Specifically, the depth of the rectangular deep groove is 0.8 to 1.2 times the gear module, and the depth of the rectangular shallow groove is 0.1 to 0.3 times the depth of the rectangular deep groove. These limitations on the depth of the rectangular deep groove effectively control the increased energy loss and decreased flow stability caused by excessive orifice flow velocity. The specific dimensions of the rectangular shallow groove depth can be adjusted as needed in specific applications to flexibly adapt to the oil trapping and unloading requirements under different conditions.

[0014] Specifically, on the same end plate, the distance between the two rectangular deep grooves in the Y-axis is equal to the product of the base circle pitch of the gear and the cosine of the meshing angle, and the distance between the two rectangular shallow grooves in the Y-axis is 0.5 times the distance between the two rectangular deep grooves in the Y-axis. This design can avoid the reduction in volumetric efficiency caused by the direct connection between the inlet and outlet media through the single-tooth oil-trapping area; at the same time, it can also avoid the reduction in volumetric efficiency caused by the direct connection between the inlet and outlet media through the double-tooth oil-trapping area.

[0015] Furthermore, to ensure smooth flow of fluid within the rectangular shallow tank, the rectangular shallow tank is formed by expanding along the Y-axis towards the vertical plane from the top of the inner wall of the rectangular deep tank facing the vertical plane within the same stepped unloading tank. This design allows the side of the rectangular shallow tank away from the vertical plane to be fully connected to the rectangular deep tank, enabling the oil and other fluids within the rectangular shallow tank to smoothly enter the rectangular deep tank for successful unloading of the single-tooth trapped oil area. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of an embodiment of this application.

[0017] Figure 2 This is a schematic diagram of the double-step unloading groove on the rear end plate in this application.

[0018] Figure 3 This is a geometrical diagram of the double-step unloading groove in this application.

[0019] Figure 4 for Figure 3 The right view.

[0020] Figure 5 This is a schematic diagram of the structure of a double rectangular unloading groove in the prior art.

[0021] Figure 6 This is a schematic diagram showing the setup of observation points for flow field simulation in this application.

[0022] Figure 7 To adopt Figure 5 The pressure change curve of the medium inside the gear pump is shown in the double rectangular unloading groove diagram.

[0023] Figure 8 To adopt Figure 2 The pressure change curve of the medium inside the gear pump is shown in the double-step unloading tank diagram. Detailed Implementation

[0024] The following section first describes the combined structure used in this application for synchronous unloading of trapped oil in single-tooth and double-tooth gear pumps. Please refer to [link / reference needed]. Figures 1-3 The combined structure includes a drive gear shaft 1, a drive gear 2 fixedly mounted on the drive gear shaft 1, a driven gear shaft 3, a driven gear 4 fixedly mounted on the driven gear shaft 3, and two end plates, namely a front end plate 5 and a rear end plate 6. In this embodiment, the drive gear shaft and the drive gear are an integral structure, and the driven gear shaft and the driven gear are also an integral structure. As structural components of the gear pump, the drive gear and the driven gear have the same structure and dimensions; for ease of description, the drive gear and the driven gear are collectively referred to as gears. Both ends of the drive gear shaft and the driven gear shaft are rotatably connected to the shaft holes of an end plate, and there is a tooth end gap between the gear end face and the inner surface of the adjacent end plate. The drive gear 2 and the driven gear 4 mesh with each other and together form a gear pair. One end of the drive gear shaft passes through the front end plate and can be connected to the output shaft of the drive device.

[0025] An XYZ rectangular coordinate system is constructed with the midpoint of the line connecting the center lines of the two shaft holes on the inner side of the rear end plate 6 as the origin. The midpoint of the line connecting the center lines of the two shaft holes on the inner side of the rear end plate is represented by O. The XOY plane is called the flow plane, and the XOZ plane is called the vertical plane. The thickness direction of the end plate extends along the X-axis. The central axes of the driving gear shaft and the driven gear shaft are parallel to each other and both are located in the vertical plane, so that the driving gear shaft and the driven gear shaft both extend along the X-axis.

[0026] The two end plates have identical structures and are mounted on both sides of the gear pair in a mirror-symmetrical manner. In this embodiment, each end plate has a mirror-symmetrical shape with the flow plane as the plane of symmetry, and each end plate has a mirror-symmetrical shape with the vertical plane as the plane of symmetry.

[0027] Two stepped unloading grooves are provided on the inner side of each end plate with the vertical plane as the symmetrical plane. The stepped unloading grooves are formed by the indentation of the inner side of the end plate along the X-axis, and the two stepped unloading grooves on the same end plate are mirror symmetrical with the flow plane as the symmetrical plane. Each stepped unloading groove includes a rectangular deep groove 7 and a rectangular shallow groove 8 that are connected to each other, and the depth of the rectangular shallow groove is less than the depth of the rectangular deep groove.

[0028] In the same stepped unloading groove, the rectangular shallow groove is located on the side of the rectangular deep groove facing the vertical plane. The rectangular shallow groove is formed by the expansion of the top of the inner wall of the rectangular deep groove facing the vertical plane along the Y-axis towards the vertical plane. This allows the rectangular deep groove and rectangular shallow groove of the same stepped unloading groove to be interconnected, making the stepped unloading groove a stepped groove with a single-sided step. The side of each stepped unloading groove away from the vertical plane penetrates the outer periphery of the end plate it is located on.

[0029] Furthermore, within the same stepped unloading groove, the rectangular shallow groove and the rectangular deep groove have the same width B along the Z-axis, meaning that the width of either the rectangular shallow groove or the rectangular deep groove along the Z-axis can also serve as the width of the stepped unloading groove. The width of the stepped unloading groove is 1.4 times the tooth height of the gear, meaning the width of the stepped unloading groove is 1.4 times the tooth height of either the driving gear or the driven gear. The second depth H of the rectangular deep groove is 1.05 times the module of the gear, meaning the second depth H of the rectangular deep groove is 1.05 times the module of either the driving gear or the driven gear, and the first depth h of the rectangular shallow groove is 0.1 times the second depth H of the rectangular deep groove.

[0030] In this embodiment, within the same end plate, the second distance A between two rectangular deep grooves is equal to the product of the base circle pitch of the gear and the cosine of the meshing angle; that is, the second distance A between two rectangular deep grooves is equal to the product of the base circle pitch of the driven gear or the driving gear and the cosine of the meshing angle. The first distance a between two rectangular shallow grooves is 0.5 times the second distance A between two rectangular deep grooves; that is, the first distance a between two rectangular shallow grooves is equal to half the product of the base circle pitch of the gear and the cosine of the meshing angle.

[0031] The following simulation calculation is performed on a gear pump using the above-mentioned combined structure. The specific parameter settings are as follows: the number of teeth of both the driving gear and the driven gear is 10, the module is 4.75 mm, the pressure angle is 20°40′, the tooth tip height coefficient is 1.0, the tip clearance coefficient is 0.25, the displacement coefficient is 0.11, and the tooth width is 20 mm; the inlet pressure is 1 atm, and the outlet pressure is 20 atm; the counterclockwise rotational speed of the driving gear 2 is 2000 rpm; the dynamic viscosity of the medium is 0.09 Pa·s, the density is 850 kg / m3, the bulk modulus of elasticity is 1.5 × 109 Pa, and the saturated vapor pressure is 400 Pa; the gap parameters are tooth flank clearance 0.2 mm, tooth tip gap 0.05 mm, tooth meshing gap 0.04 mm, and tooth tip gap 0.1 mm; the structural dimensions of the stepped unloading groove are A = 12.8 mm, a = 6.40 mm, B = 15 mm, H = 5 mm, h = 0.5 mm, and D = 20 mm. Where D is the diameter of the shaft holes on the two end plates of the driving gear shaft and the driven gear shaft.

[0032] For ease of comparison, the stepped unloading grooves on the two end plates have been replaced with the double rectangular unloading grooves found in existing technology. Please refer to [link / reference needed]. Figure 5 For ease of description, the end plate in the prior art is referred to as end plate S61. Two rectangular unloading grooves 71 are formed on the inner side of end plate S61, which are symmetrically arranged with respect to the virtual plane. The width of the rectangular unloading grooves 71 is 15 mm, the depth is 5 mm, and the distance between the two rectangular unloading grooves is 12.8 mm.

[0033] CFD simulations of the internal flow field of gear pumps employing this application and existing technologies were conducted using PUMPLINX software. The geometric models used in the simulations were created using UGNX software. To monitor pressure changes within the pump's flow domain, four observation points were set in the mesh model. (See [link to relevant documentation]). Figure 6 The four observation points specifically include the inlet static point i, the outlet static point o, the synchronous rotation dynamic point p1 at the root of the driving gear tooth groove, and the synchronous rotation dynamic point p2 at the root of the driven gear tooth groove.

[0034] Simulation results and analysis:

[0035] Trapped oil pressure: The pressure curve of the flow area using the existing technology of double rectangular unloading trough is as follows. Figure 7 As shown, the flow basin pressure curve using the double-step unloading trough of this application is as follows: Figure 8 As shown. Figure 7 and Figure 8As shown, when using the existing double-rectangular unloading groove, the maximum oil trapping pressure of a single tooth is 4.03 MPa, the maximum oil trapping pressure of a double tooth is 4.49 MPa, and the minimum oil trapping pressure across the entire range is 4278 Pa. When using the double-step unloading groove of this application, the maximum oil trapping pressure of a single tooth is 2.61 MPa, the maximum oil trapping pressure of a double tooth is 2.46 MPa, and the minimum oil trapping pressure is 4756 Pa. Compared with the existing double-rectangular unloading groove, the maximum oil trapping pressure of a single tooth in this application decreases by 35.2%, the maximum oil trapping pressure of a double tooth decreases by 45.2%, and the minimum oil trapping pressure increases by 11.2%. The results show that the oil trapping and unloading effect of the gear pump is significant when using the double-step unloading groove of this application.

[0036] Power and Flow Rate: When using the existing double rectangular unloading trough, the total average input power is 2440.2 W; when using the double-step unloading trough of this application, the total average input power is 2307.7 W, a decrease of 5.4% compared to the existing double rectangular unloading trough. When using the existing double rectangular unloading trough, the average output volumetric flow rate is 14.18 GPM; when using the double-step unloading trough of this application, the average output volumetric flow rate is 14.28 GPM, an increase of 0.71% compared to the existing double rectangular unloading trough.

Claims

1. A synchronous unloading structure for single and double toothed oil trapping in a gear pump, characterized in that, The device includes a drive gear shaft, a drive gear integrally formed on the drive gear shaft, a driven gear shaft, a driven gear integrally formed on the driven gear shaft, and two end plates, which are a front end plate and a rear end plate, respectively. The drive gear and the driven gear are collectively referred to as gears. Both ends of the drive gear shaft and the driven gear shaft are rotatably mounted in the shaft holes of one end plate. There is a tooth end gap between the end face of the gear and the inner side of the adjacent end plate. The drive gear and the driven gear mesh with each other and together form a gear pair. The midpoint of the line connecting the center lines of the two shaft holes on the inner side of the rear end plate is represented by O. An XYZ rectangular coordinate system is constructed with O as the origin. The XOY plane is called the flow plane, and the XOZ plane is called the vertical plane. The thickness direction of the end plate extends along the X-axis. The central axes of the drive gear shaft and the driven gear shaft are parallel to each other and both are located in the vertical plane. Two stepped unloading grooves are provided on the inner side of each end plate with the vertical plane as the symmetry plane. The stepped unloading grooves are formed by the indentation of the inner side of the end plate along the X-axis, and each stepped unloading groove is mirror-symmetrical with the flow plane as the symmetry plane. Each stepped unloading groove includes an interconnected rectangular deep groove and a rectangular shallow groove, and the depth of the rectangular shallow groove is less than the depth of the rectangular deep groove. In the same stepped unloading groove, the rectangular shallow groove is located on the side of the rectangular deep groove facing the vertical plane. The side of each stepped unloading groove away from the vertical plane penetrates the outer periphery of the end plate.

2. The synchronous unloading structure according to claim 1, characterized in that, Each end plate is mirror-symmetrical about the flow plane and also mirror-symmetrical about the vertical plane.

3. The synchronous unloading structure according to claim 1, characterized in that, The two end plates have the same structure and are assembled on both sides of the gear pair in a mirror-symmetrical manner.

4. The synchronous unloading structure according to claim 1, characterized in that, In the same stepped unloading groove, the rectangular shallow groove and the rectangular deep groove have the same width in the Z-axis direction. The width of the rectangular shallow groove and the rectangular deep groove in the Z-axis direction is 1.2 to 1.5 times the tooth height of the gear.

5. The synchronous unloading structure according to claim 1, characterized in that, The depth of the rectangular deep groove is 0.8 to 1.2 times the module of the gear, and the depth of the rectangular shallow groove is 0.1 to 0.3 times the depth of the rectangular deep groove.

6. The synchronous unloading structure according to claim 1, characterized in that, On the same end plate, the distance between the two rectangular deep grooves in the Y-axis is equal to the product of the base circle pitch of the gear and the cosine of the meshing angle, and the distance between the two rectangular shallow grooves in the Y-axis is 0.5 times the distance between the two rectangular deep grooves in the Y-axis.

7. The synchronous unloading structure according to claim 1, characterized in that, In the same stepped unloading groove, the rectangular shallow groove is formed by the expansion of the top of the inner wall of the rectangular deep groove toward the vertical plane along the Y-axis.

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