An evaluation method and assembly method for low-noise crankcase assembly accuracy.

Abstract

The present invention belongs to the technical field of crankcase design and assembly, and in particular, relates to an evaluation method and an assembly method for low-noise crankcase assembly accuracy. The evaluation method includes the following contents: based on the dimensions of the current crankcase and the dimensions of the relevant parts of the current crankcase, a plane dimension chain with each cylinder as a closed ring is established respectively, and the dimension range of each cylinder closed ring in the current crankcase is calculated; if the dimension range of each cylinder closed ring in the current crankcase is within the set allowable range, the assembly accuracy of the current crankcase is qualified; otherwise, the assembly accuracy of the current crankcase is unqualified. The present invention accurately determines whether the assembly accuracy of the current crankcase is qualified by calculating the dimension range of each cylinder closed ring in the current crankcase at one time, thereby reducing the crankcase noise generated by low assembly accuracy.

Description

Technical Field

[0001] The invention belongs to the technical field of crankcase design and assembly, and in particular relates to an evaluation method for assembly accuracy of a low-noise crankcase and an assembly method. Background Art

[0002] As a fluid machine that increases gas pressure, reciprocating compressors play a very important role in many fields such as petroleum and chemical industry. However, the huge noise generated by reciprocating compressors during operation not only damages the physical and mental health of operators, affects production efficiency and quality, but also has a great negative impact on the environment of workshops and factories.

[0003] There are many reasons why reciprocating compressors generate noise. If these noise reasons are classified by parts, there is no doubt that the crankcase is an important part that generates noise. As one of the key components of the compressor, the crankcase, with the participation of the crankshaft, cooperates with the coupling shield, bearing seat, and connecting rod to complete the transmission of motor power, convert the crankshaft rotation into the reciprocating swing of the connecting rod, and cooperates with the cylinder and piston to achieve reciprocating motion to complete gas compression.

[0004] The crankcase, which closely interacts with other parts in the compressor, is a carrier of moving parts. The crankcase has a closed shell structure. If the crankcase with too low assembly accuracy is directly assembled with the crankcase-related parts, it will inevitably cause excessive noise in the crankcase due to inappropriate tolerances between the parts and inappropriate matching between the assembly contact parts. Therefore, in the process of assembling the crankcase and the crankcase-related parts, technicians often decide whether to adjust the size of the crankcase and the crankcase-related parts based on the actual tightness of each assembly part. However, disassembling the assembled parts for adjustment will also cause irreversible assembly damage to the crankcase and related parts, reducing the efficiency of the entire assembly process. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and to provide a method for evaluating the assembly accuracy of a low-noise crankcase. Before performing the actual assembly operation, the method can accurately determine whether the assembly accuracy of the current crankcase is qualified by calculating the size range of each cylinder closing ring in the current crankcase at one time, thereby reducing the crankcase noise caused by low assembly accuracy.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for evaluating the assembly accuracy of a low-noise crankcase includes the following contents:

[0008] Based on the dimensions of the current crankcase and its related parts, plane dimension chains with each cylinder as a closed ring are established to calculate the dimension range of each cylinder closed ring in the current crankcase. If the dimension range of each cylinder closed ring in the current crankcase is within the set allowable range, the assembly accuracy of the current crankcase is qualified; otherwise, the assembly accuracy of the current crankcase is unqualified.

[0009] Preferably, calculating the size range of any cylinder sealing ring in the current crankcase also includes the following sub-steps:

[0010] Step 11, calculate the intermediate deviation of each component ring in the current crankcase :

[0011] ;

[0012] in, Indicates the middle deviation of the component ring numbered n; represents the actual measured value of the pth component and / or crankcase in the production batch of the pre-assembled components and / or crankcases constituting the component ring numbered n, 1≤p≤N and p is a positive integer, that is, the total number of components corresponding to the current batch is N; Indicates the predicted value of the production batch of the pre-assembled parts and / or crankcases constituting the component ring number n;

[0013] Step 12: Establish the plane dimension chain of the crankcase according to the matching relationship and calculate the closed loop Middle Deviation:

[0014] ;

[0015] in, Represents a closed loop The middle deviation of represents the transmission coefficient of the component ring numbered n; Represents the relative asymmetry coefficient of the constituent ring numbered n; Indicates the tolerance of the component ring numbered n; D1~D 10 Indicates the component rings numbered 1 to 10;

[0016] Step 13, calculate the closed ring size range CL of the cylinder by probability method:

[0017] ;

[0018] in, Indicates the corresponding component ring The nominal size of the closed loop; k0 represents the relative distribution coefficient of the closed loop; Indicates the corresponding component ring The relative distribution coefficient.

[0019] Preferably, the crankcase includes a case body, which is a polyhedron with a number of faces greater than or equal to 5, and includes an upper bottom surface, a first side surface, a second side surface, a third side surface and a fourth side surface, two coaxial bearing seat holes are respectively arranged on the first side surface and the second side surface, an air inlet hole is opened on the upper bottom surface, and a first exhaust hole and a first-stage cylinder guide hole are opened on the third side surface; a noise reduction structure for reducing noise inside the case body is arranged on the inner wall of the case body.

[0020] Preferably, the noise reduction structure includes reinforcing ribs and mesh protrusions, and the reinforcing ribs and the mesh protrusions are both arranged on the inner wall of the box body; the reinforcing ribs include circular reinforcing ribs and strip reinforcing ribs, and the circular reinforcing ribs are arranged around each hole; the extension lines of the strip reinforcing ribs on the first side surface and the second side surface pass through the center of the bearing seat hole, and a plurality of strip reinforcing ribs parallel to the length direction of the crankshaft are arranged on the upper bottom surface, the third side surface and the fourth side surface; the box body, the inner wall reinforcing ribs and the mesh protrusions are all sprayed with sound-absorbing material.

[0021] Preferably, the first exhaust hole is arranged directly below, directly above, or on a side of the first primary cylinder guide hole away from the air inlet hole; the second exhaust hole and the second primary cylinder guide hole are provided on the fourth side, and the second exhaust hole is provided directly below, directly above, or on a side of the second primary cylinder guide hole away from the air inlet hole; the first secondary cylinder guide hole is also provided on the third side, and the first secondary cylinder guide hole is provided on a side of the first exhaust hole away from the air inlet hole; the second secondary cylinder guide hole is also provided on the fourth side, and the second secondary cylinder guide hole is provided on a side of the second primary cylinder guide hole close to the air inlet hole; an air inlet pipeline extends from the outside of the box through the air inlet hole into the inner cavity of the box, and the first exhaust pipeline and the second exhaust pipeline extend from the outside of the box through the first exhaust hole and the second exhaust hole into the inner cavity of the box respectively; the outer diameter of each pipeline is the same as the diameter of the corresponding air inlet hole or exhaust hole.

[0022] Preferably, a plane parallel to the upper bottom surface, perpendicular to the third side surface and passing through the center of the first-stage cylinder guide hole is recorded as a first plane, a plane parallel to the upper bottom surface, perpendicular to the third side surface and passing through the center of the first-stage cylinder guide hole is recorded as a second plane, a plane parallel to the upper bottom surface, perpendicular to the fourth side surface and passing through the center of the second-stage cylinder guide hole is recorded as a third plane, and a plane parallel to the upper bottom surface, perpendicular to the fourth side surface and passing through the center of the second-stage cylinder guide hole is recorded as a fourth plane, then the first plane does not overlap with the second plane, and the third plane does not overlap with the fourth plane.

[0023] Preferably, the crankcase-related components include bearings, bearing seats, crankshafts, connecting rods, connecting rod big end bearings, connecting rod small end bearings, cylinders, pistons and piston pins; D1 represents the distance from the outer end surface of the crankcase body to the bottom surface of the bearing mounting hole inside the bearing seat; D2 represents the width of the bearing, D3 represents the distance between the bearing mounting surface on the crankshaft and the connecting rod big end bearing mounting surface; D4 represents the distance between the connecting rod big end bearing end surface and the plane passing through the bearing center point and perpendicular to the axis; D5 represents the distance between the connecting rod small end bearing end surface and the plane passing through the small end bearing center point and perpendicular to the axis; D6 represents the distance between the inner hole end surface of the piston pin seat and the center section of the piston; D7 represents the piston radius, D8 represents the gap between the piston and the cylinder; D9 represents the inner radius of the cylinder center hole; D 10 It indicates the distance between the center axis of the cylinder and the first side mounting surface of the crankcase; △D indicates the distance between the end face of the connecting rod small end bearing and the end face of the inner hole of the piston pin seat.

[0024] Preferably, obtaining the finished crankcase before assembly includes the following steps:

[0025] S1, after obtaining the initialized crankcase, simulating the external noise of the initialized crankcase under the working environment, and collecting the external noise parameters on the initialized crankcase;

[0026] S2, after calculating the optimal values ​​of several specification parameters in the initialized crankcase according to the external noise parameters, the corresponding specification parameters of the initialized crankcase are adjusted to obtain a finished crankcase.

[0027] Preferably, in S1: the external noise parameter includes the sound pressure of the forward sound wave of the first exhaust hole , the sound pressure of the reverse sound wave of the first exhaust hole , the sound pressure of the forward sound wave of the second exhaust hole , the sound pressure of the reverse sound wave of the second exhaust hole , the sound pressure of the forward sound wave at the air intake , Sound pressure of reverse sound wave at the air inlet , an area S1 of the first exhaust hole, an area S2 of the second exhaust hole, and an area S4 of the air inlet hole;

[0028] In S2, the following sub-steps are also included:

[0029] S21, the first exhaust hole and the second exhaust hole are opened at the same time, and the sound pressure compensation constraint condition and the sound elimination amount objective function are constructed according to the external noise parameters:

[0030] The sound pressure cancellation constraint is:

[0031] ;

[0032] The objective function of sound attenuation is:

[0033] ;

[0034] Among them, e is a natural constant; Indicates the amount of sound attenuation; Indicates the sound pressure of the forward sound wave at the geometric center of the box; represents the reverse sound pressure at the geometric center of the box; S3 represents the expansion chamber area, which is the cross-sectional area of ​​the side parallel to the bearing seat hole at the geometric center of the box; m represents the expansion ratio, m=S3 / S2; L is the first spacing, which represents the straight-line distance between the center of the air inlet hole and the center of the first exhaust hole; K represents the noise wave number; i represents the harmonic number of the noise;

[0035] S22, under the constraint of sound pressure cancellation, find the maximum value of the noise reduction objective function max And the corresponding optimal reverse sound wave sound pressure at the geometric center of the box , the best forward sound wave sound pressure at the geometric center of the box , optimal expansion chamber area S 3,best and the optimal first spacing L best ;

[0036] S23, based on the optimal expansion chamber area S 3,best and the optimal first spacing L best Adjust the corresponding specification parameters of the initialized crankcase to obtain a finished crankcase.

[0037] The present invention also provides a method for assembling a low-noise crankcase, comprising the following steps:

[0038] Step 1: using the above-mentioned evaluation method for the assembly accuracy of a low-noise crankcase to determine whether the assembly accuracy of the current crankcase is qualified;

[0039] Step 2: If the assembly accuracy of the current crankcase is qualified, the current crankcase and various parts related to the crankcase are directly assembled; if the assembly accuracy of the current crankcase is unqualified, the technician adjusts the size of the crankcase and / or various parts related to the crankcase, and returns to step 1 until the assembly accuracy of the crankcase is qualified.

[0040] The beneficial effects of the present invention are:

[0041] (1) The present invention provides a method for evaluating the assembly accuracy of a low-noise crankcase. By calculating the size range of each cylinder sealing ring in the current crankcase at one time, the method can accurately determine whether the assembly accuracy of the current crankcase is qualified, thereby reducing the crankcase noise generated by low assembly accuracy.

[0042] (2) The structure of the low-noise crankcase of the present invention has a good noise reduction effect and can reduce the noise transmitted from the inside of the crankcase to the outside; and there is no need to increase the thickness of the case body. By arranging air inlet holes and exhaust holes on the case body and limiting the positions of the air inlet holes and exhaust holes on the case body, the heat in the case body and the compressed gas leaked from the cylinder during operation can be promptly taken out of the crankcase through the two air flow directions in the case body, thereby ensuring that the air pressure and temperature in the crankcase are always appropriate, dissipating heat in time, efficiently compressing the air, and extending the life of the crankcase.

[0043] (3) The structure of the low-noise crankcase of the present invention has a good noise reduction effect, which is also reflected in the following aspects:

[0044] ①The eccentric design of the cylinder hole reduces the lateral force on the cylinder and reduces the noise generated when the crankcase assembly moves.

[0045] ② A noise reduction structure including reinforcing ribs and mesh protrusions is provided on the inner wall of the case, and sound-absorbing material is sprayed on the noise reduction structure. Compared with the prior art of overall thickening of the crankcase, the noise reduction structure and its arrangement method in the present invention require very little space, so the volume of the crankcase does not need to be increased and the rotating area inside it will not be compressed, thereby improving the space utilization rate in the crankcase and avoiding increasing the space occupied by the compressor. In addition, the resistive silencer in the case of the present invention will only slightly increase the weight of the crankcase, but can greatly enhance the case strength and rigidity of the crankcase, and can also greatly reduce the noise generated by the crankcase and the noise transmitted from the crankcase.

[0046] ③ The air intake pipe extends from the outside of the housing through the air intake hole to the inner cavity of the housing, and the first exhaust pipe and the second exhaust pipe extend from the outside of the housing through the first exhaust hole and the second exhaust hole to the inner cavity of the housing respectively. The air intake pipe, the exhaust pipe and the housing are equivalent to two series-connected internal expansion chamber silencers in the process of propagation of external noise. The noise reduction structure and the inner wall of the housing sprayed with sound-absorbing material make the entire inner cavity of the housing become a resistive silencer. That is, on the basis of the crankcase forming an expansion chamber silencer with the air intake pipe and the exhaust pipe, the housing is also set as a resistive silencer, which not only avoids the increase of noise caused by the resonance of the crankcase, but also converts the sound energy into heat energy due to friction during the propagation of the noise sound wave in the housing, so that the noise decays with the propagation distance, and the timely heat dissipation function of the crankcase of the present invention can also ensure that the friction heat generated in the silencer process will be taken out of the crankcase from the exhaust hole by the airflow, so the crankcase of the present invention can well prevent the external noise from being transmitted from the crankcase, and also ensure that the air pressure and temperature in the crankcase are always suitable.

[0047] (4) In the present invention, the technician designs the crankcase when the working noise is determined, and modifies the specification parameters on the initialized crankshaft to obtain a finished crankcase with the best noise reduction effect.

[0048] (5) The assembly method of the prior art will assemble the crankcase and some parts related to the crankcase when the assembly accuracy is too low. Even if the crankcase and some parts are disassembled and adjusted later, irreversible assembly damage will occur to the crankcase and some parts related to the crankcase, thereby reducing the adjustment efficiency, and further reducing the efficiency of the entire assembly process; and the assembly accuracy after adjustment can only be relatively improved, reducing some noise caused by low assembly accuracy. The assembly method of the present invention accurately controls whether the assembly accuracy between the crankcase and some parts related to the crankcase is qualified by calculating multiple cylinder closed rings before assembly. Only the crankcase and some parts related to the crankcase with qualified assembly accuracy can be assembled. In this way, it is ensured that the crankcase and some parts related to the crankcase only need to be assembled once, without multiple disassembly and adjustment, avoiding assembly damage to reduce the adjustment efficiency, and the efficiency of the entire assembly process is high. In addition, the assembly method of the present invention greatly improves the assembly accuracy and greatly reduces the crankcase noise caused by low assembly accuracy, further reducing the crankcase noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a schematic diagram of the overall structure of the low-noise crankcase of the present invention;

[0050] Figure 2 It is a front view of the low noise crankcase of the present invention;

[0051] Figure 3 It is a rear view of the low noise crankcase of the present invention;

[0052] Figure 4 It is a left side view of the low noise crankcase of the present invention;

[0053] Figure 5 A top view of the low noise crankcase of the present invention;

[0054] Figure 6 A bottom view of the low noise crankcase of the present invention;

[0055] Figure 7 for Figure 5 AA section view in;

[0056] Figure 8 for Figure 5 BB section view in;

[0057] Fig. 9 for Figure 2 CC section view in;

[0058] Fig.10 It is a schematic diagram of the rotating area in the low-noise crankcase;

[0059] Fig.11 It is a schematic diagram of the reticulated protrusion;

[0060] Fig.12 for Figure 7 The enlarged schematic diagram of F in FIG.

[0061] Fig.13 for Figure 8 The enlarged schematic diagram of G in FIG.

[0062] Fig.14 for Fig. 9 The enlarged schematic diagram of H in FIG.

[0063] Fig.15 It is a schematic diagram of the plane dimension chain of the crankcase;

[0064] Fig.16 For the relevant parts in the crankcase Fig. 9 Schematic diagram of the position under viewing angle;

[0065] Fig.17 for Fig.16 Enlarged view of the point α in the middle Figure Ⅰ ;

[0066] Fig.18 for Fig.16 Enlarged view of the point α in the middle Figure II ;

[0067] Fig.19 The present invention is a flowchart of a method for evaluating the assembly accuracy of a low-noise crankcase.

[0068] The actual correspondence between the reference numerals and component names of the present invention is as follows:

[0069] 1. Bearing seat hole;

[0070] 2. Box body;

[0071] 31. First exhaust hole; 32. First stage cylinder guide hole;

[0072] 41. Second exhaust hole; 42. Second first-stage cylinder guide hole;

[0073] 5. Air intake hole;

[0074] 61. First and second level cylinder guide hole; 62. Second and second level cylinder guide hole;

[0075] 7. Top mounting hole; 71. First top mounting hole; 72. Second top mounting hole;

[0076] 9. Bottom mounting hole;

[0077] 101, reinforcing ribs; 102, mesh convexities;

[0078] J1, bearing; J2, bearing seat; J3, crankshaft; J4, connecting rod; J5, connecting rod big end bearing; J6, connecting rod small end bearing; J7, cylinder; J8, piston; J9, piston pin; DETAILED DESCRIPTION

[0079] In order to make the technical solution of the present invention clearer and more specific, the present invention is clearly and completely described below in conjunction with the accompanying drawings. Any equivalent replacement of the technical features of the technical solution of the present invention and any solution derived by conventional reasoning by ordinary technicians in the field without making any creative work shall fall within the protection scope of the present invention.

[0080] Example 1

[0081] like Figure 1 FIG. 1 is a schematic diagram of the overall structure of the low-noise crankcase of the present invention. Figure 2 to Figure 6 Various views of the low-noise crankcase, including Figure 4 The left view of the crankcase and the right view of the low-noise crankcase are Figure 4 same.

[0082] A low-noise crankcase includes a case body 2, which is a polyhedron with a number of faces greater than or equal to 5. When the number of faces of the case body 2 is greater than or equal to 6, a top mounting hole 7 and an air inlet 5 are provided on the upper bottom surface of the case body 2, and a bottom mounting hole 9 is provided on the lower bottom surface of the case body 2.

[0083] In this embodiment, the top mounting holes 7 include a first top mounting hole 71 and a second top mounting hole 72 . The specific number of the top mounting holes 7 is not intended to limit the present invention.

[0084] After the parts in the crankcase are installed, the top mounting holes 7 and the bottom mounting holes 9 will be closed with a cover plate to prevent dust from entering, thereby further preventing the noise in the crankcase from being transmitted to the outside of the case 2 through the top mounting holes 7 and the bottom mounting holes 9.

[0085] If the compressor in which the crankcase is located is an oil compressor, the oil pool is fixedly arranged on the lower bottom surface of the crankcase. Specifically, the oil pool is fixedly arranged on a cover plate used to close the bottom mounting hole 9.

[0086] When the number of faces of the box body 2 is equal to 5, the box body 2 is in the shape of a triangular prism, the first side surface and the second side surface are both triangles, and the box body 2 has only an upper bottom surface but no lower bottom surface.

[0087] Two bearing seat holes 1 are respectively opened on two opposite sides of the housing 2, the two bearing seat holes 1 are coaxially arranged, a bearing seat is installed at the bearing seat hole 1, the center of the bearing seat is a bearing, a crankshaft is arranged in the cavity of the crankcase, and the two ends of the crankshaft are respectively connected to the two bearings. The sides where the two bearing seat holes 1 are located are respectively recorded as the first side surface and the second side surface.

[0088] In addition to the side where the bearing seat hole 1 is located, the housing 2 includes at least two or more other side surfaces, one of which is provided with a first exhaust hole 31 and a first-stage cylinder guide hole 32, and this side surface is recorded as a third side surface.

[0089] Optionally, the first exhaust hole 31 is arranged directly below the first-stage cylinder guide hole 32 or directly above the first-stage cylinder guide hole 32 , or on a side of the first-stage cylinder guide hole 32 away from the air inlet hole 5 .

[0090] Optionally, first and second cylinder guide holes 61 are also provided on the third side surface.

[0091] Optionally, the first-secondary cylinder guide hole 61 is arranged on a side of the first exhaust hole 31 away from the air inlet hole 5 .

[0092] Optionally, a side surface of the box body 2 other than the first side surface, the second side surface and the third side surface is recorded as a fourth side surface, and a second exhaust hole 41 and a second-stage cylinder guide hole 42 are opened on the fourth side surface.

[0093] Optionally, the second exhaust hole 41 is arranged directly below the second-stage cylinder guide hole 42 or directly above the second-stage cylinder guide hole 42 , or on a side of the second-stage cylinder guide hole 42 away from the air inlet hole 5 .

[0094] Optionally, a second secondary cylinder guide hole 62 is also provided on the fourth side surface.

[0095] Optionally, the second secondary cylinder guide hole 62 is arranged on a side of the second primary cylinder guide hole 42 close to the air inlet hole 5 .

[0096] Optionally, relative to the distance between the bearing seat hole 1 and the first exhaust hole 31, or the distance between the bearing seat hole 1 and the second exhaust hole 41, the distance between the same bearing seat hole 1 and the air inlet hole 5 is the closest or farthest.

[0097] Optionally, the outer surface of the box body 2 where the bearing seat hole 1, the first exhaust hole 31, the first primary cylinder guide hole 32, the second exhaust hole 41, the second primary cylinder guide hole 42, the air inlet hole 5, the first secondary cylinder guide hole 61, the second secondary cylinder guide hole 62, the top mounting hole 7 and the bottom mounting hole 9 are located are partially thickened. Because the local strength of the box body 2 is reduced after the holes are opened, the deformation of the hole position will increase when the force is applied, and the local thickening can reduce the deformation at the hole position, avoiding the hole position from being subjected to a large stress due to the large force. If it is not thickened, the hole position may be fatigued and damaged under continuous action.

[0098] In this embodiment, there are two-stage cylinders in total, two first-stage cylinders, respectively recorded as the first first-stage cylinder and the second first-stage cylinder; there are also two second-stage cylinders, respectively recorded as the first second-stage cylinder and the second second-stage cylinder, and the cylinder diameter of the second-stage cylinder is smaller than that of the first-stage cylinder.

[0099] The first primary cylinder is fixedly arranged in the first primary cylinder guide hole 32 along its length direction, that is, a part of the first primary cylinder is located in the inner cavity of the box body 2, and the other part is located outside the box body 2; the second primary cylinder is fixedly arranged in the second primary cylinder guide hole 42 along its length direction, the first secondary cylinder is fixedly arranged in the first secondary cylinder guide hole 61 along its length direction, and the second secondary cylinder is fixedly arranged in the second secondary cylinder guide hole 62 along its length direction.

[0100] One end of the connecting rod of each cylinder is connected to the piston in the cylinder, and the other end is sleeved on the crankshaft to form a crank-connecting rod mechanism. When the motor outside the crankcase is energized, the crankshaft is driven to rotate. The crank-connecting rod mechanism converts the rotational motion of the crankshaft into the reciprocating linear motion of the connecting rod, driving the piston in the cylinder to also perform reciprocating linear motion, and the air in the cylinder is compressed. In this embodiment, the primary cylinder and the secondary cylinder on the same side are connected outside the crankcase, and a pressure relief valve is provided on the connecting pipeline, and the pistons in the primary cylinder and the secondary cylinder on the same side move in opposite directions. Taking air as an example, on the same side, when the first-level cylinder inhales air, the air in the environment enters the first-level cylinder, and at the same time, the second-level cylinder compresses the gas and discharges the second-level compressed gas. The second-level compressed gas discharged from the second-level cylinder is subsequently processed and stored in the gas tank; after the first-level cylinder compresses the air to obtain the first-level compressed gas, the first-level compressed gas is discharged, and at the same time, the second-level cylinder inhales air, that is, the first-level compressed gas flows out of the first-level cylinder, flows through the pressure relief valve, and then enters the second-level cylinder; subsequently, when the second-level cylinder compresses the gas and discharges the second-level compressed gas, the first-level cylinder starts to inhale new air again, and this is repeated continuously to complete the compression of the gas, so the air in this embodiment is compressed in two stages.

[0101] After the crankshaft, cylinder and other parts are installed into the crankcase, except for the air inlet 5 and the first exhaust hole 31 and the second exhaust hole 41, all other holes of the crankcase are sealed. However, the compressed gas in the cylinder will enter the crankcase body 2 along the inner wall of the piston and the cylinder body. If the air inlet 5 and the first exhaust hole 31 and the second exhaust hole 32 are also sealed, the temperature and pressure in the crankcase will gradually increase, which will not only reduce the viscosity of the lubricating oil on the crankshaft, causing the lubrication performance to deteriorate and increase the wear of the crankshaft and related parts, but also the temperature increase in the crankcase will accelerate the oxidation, deterioration and carbonization of the lubricating oil, further increase the wear of the crankshaft and related parts, and directly affect the gas compression efficiency of the compressor; even when the temperature and pressure in the crankcase are too high, it will increase the risk of crankcase explosion.

[0102] Therefore, the crankcase of the present invention is provided with an air inlet 5 and a first exhaust hole 31 and a second exhaust hole 41. The air inlet pipeline extends from the outside of the case 2 through the air inlet 5 to the inner cavity of the case 2. The first exhaust pipeline and the second exhaust pipeline extend from the outside of the case 2 through the first exhaust hole 31 and the second exhaust hole 41 to the inner cavity of the case 2 respectively. The outer diameters of all pipelines are the same as the diameters of the corresponding air inlet / exhaust holes, and all pipelines and the corresponding air inlet holes or exhaust holes are sealed. The inner cavity of the case 2 is negative pressure relative to the atmospheric environment outside the case 2. The room temperature gas enters the inner cavity of the case 2 from the air inlet 5 and is then discharged from the first exhaust hole 31 or the second exhaust hole 41. Not only does it maintain the negative pressure in the inner cavity of the case 2, but it also takes away the heat in the inner cavity of the case 2. In this way, even if the compressed gas in the cylinder enters the case 2 of the crankcase along the inner wall of the piston and the cylinder body, it will not increase the temperature and pressure in the case 2.

[0103] After many tests by technicians, the crankcase of the present invention has made special restrictions on the position setting of the air intake hole and the exhaust hole: relative to the same bearing seat hole 1, the distance between the air intake hole 5 and it is the smallest or largest. For the convenience of description, the smallest distance between the air intake hole 5 and the same bearing seat hole 1 is taken as an example:

[0104] The first exhaust hole 31 on the third side is closer to the air inlet hole 5 than the second exhaust hole 41 on the fourth side. Therefore, there are two air flow directions in the box body 2: ① flowing into the box body 2 from the air inlet hole 5 and then discharged from the first exhaust hole 31; ② flowing into the box body 2 from the air inlet hole 5 and then discharged from the second exhaust hole 41. For the first air flow direction, the first and second cylinder guide holes 61 are arranged on the side of the first exhaust hole 31 away from the air inlet hole 5, and the first exhaust hole 31 is arranged directly below the first and second cylinder guide hole 32 or directly above the first and second cylinder guide hole 32, or on the side of the first and second cylinder guide hole 32 away from the air inlet hole 5; so on the third side, in order from near to far from the air inlet hole 5, the first exhaust hole 31 and the first and second cylinder guide hole 32 are arranged side by side, and then the first and second cylinder guide hole 61; or the first and first cylinder guide hole 32, then the first exhaust hole 31, and finally the first and second cylinder guide hole 61; or the first and first cylinder guide hole 32, then the first and second cylinder guide hole 61, and finally the first exhaust hole 31. For the second type of air flow direction, the second secondary cylinder guide hole 62 is arranged on the side of the second primary cylinder guide hole 42 close to the air inlet 5, and the second exhaust hole 41 is arranged directly below the second primary cylinder guide hole 42 or directly above the second primary cylinder guide hole 42, or on the side of the second primary cylinder guide hole 42 away from the air inlet 5; so on the fourth side, in order from near to far from the air inlet 5, the second secondary cylinder guide hole 62, then the second exhaust hole 41 and the second primary cylinder guide hole 42; or the second secondary cylinder guide hole 62, then the second primary cylinder guide hole 42, and finally the second exhaust hole 41. Therefore, in the present invention, the crankcase uses two airflows each biased to one side to efficiently take away the compressed gas and heat leaked from the case 2, and at the same time, the friction heat generated by the crankshaft during rotation will also be taken out of the case 2 by the two airflows with different directions. Furthermore, the first exhaust hole 31 is closer to the air inlet 5 than the second exhaust hole 41, so the heat and compressed gas in the half of the space in the housing 2 near the air inlet 5 will be firstly taken out by the airflow from the first exhaust hole 31, and the negative pressure and temperature in the housing 2 will be ensured immediately; the heat and compressed gas in the other half of the space in the housing 2 away from the air inlet 5 will be taken out by the airflow from the second exhaust hole 41. That is, the crankcase of the invention can ensure that the heat in the housing 2 and the compressed gas leaked from the cylinder will be efficiently taken out of the crankcase during operation, ensuring that the air pressure and temperature in the crankcase are always appropriate, and ensuring efficient compression of air.

[0105] The first exhaust hole 31 and the second exhaust hole 41 can be opened in different time periods or at the same time. That is to say, during the operation of the crankcase, there may be only the first airflow direction, only the second airflow direction, or both the first and second airflow directions at the same time.

[0106] There are two main reasons for the noise in the crankcase: pneumatic noise and mechanical noise. Pneumatic noise is mainly caused by gas flow and gas leakage. For example, pneumatic noise is generated at the valve on the cylinder or crankcase. These pneumatic noises will enter the box body 2 through the cylinder guide hole, the air inlet hole and the exhaust hole. For example, pneumatic noise is also generated when the airflow flows through the box body 2. Mechanical noise is mainly caused by mechanical collision, mechanical friction, etc., such as the mechanical noise generated by the piston and the cylinder during the piston movement, or the mechanical noise generated by the crankshaft drive sleeve during the rotation of the crank connecting rod mechanism on it; for example, the single component of the crankcase is precisely controlled, so that there is an inappropriate tolerance between the crankcase and the bearing seat and other components. Under the tolerance accumulation, the original single size tolerance of the crankcase is affected by the tolerance of multiple components, resulting in a serious mismatch between its original design tolerance and the actual assembly tolerance, which indirectly affects the positional relationship of each friction pair, making the friction pair wear uneven, the local wear aggravated, and the mechanical noise getting bigger and bigger. Whether it is pneumatic noise or mechanical noise inside the crankcase, it will be transmitted from the crankcase to the outside.

[0107] Optionally, a plane parallel to the upper bottom surface, perpendicular to the third side surface and passing through the center of the first primary cylinder guide hole 32 is recorded as a first plane; a plane parallel to the upper bottom surface, perpendicular to the third side surface and passing through the center of the first secondary cylinder guide hole 61 is recorded as a second plane; a plane parallel to the upper bottom surface, perpendicular to the fourth side surface and passing through the center of the second primary cylinder guide hole 42 is recorded as a third plane; a plane parallel to the upper bottom surface, perpendicular to the fourth side surface and passing through the center of the second secondary cylinder guide hole 62 is recorded as a fourth plane; then the first plane does not overlap with the second plane, and the third plane does not overlap with the fourth plane.

[0108] For the sake of convenience, this situation is called the eccentric design of the cylinder hole. The eccentric design of the cylinder hole in the present invention can indeed reduce the lateral force on the cylinder and reduce the noise generated when the crankcase assembly moves. After a comparison test by the technicians, it was confirmed that the crankcase with the eccentric cylinder hole design has lower noise during use when other specifications of the crankcase remain unchanged.

[0109] In the inner cavity of the box body 2, as Figure 7 to Figure 9 As shown in the cross-sectional view, a noise reduction structure is provided on the inner wall of the box body 2, and the noise reduction structure includes a reinforcing rib 101 and a mesh protrusion 102. In order to facilitate viewing and distinguish from the cross-section, Figure 7 to Figure 9 In the cross-sectional view, only the reinforcing rib 101 is drawn, and the mesh protrusion 102 is not drawn; the mesh protrusion 102 is shown in the enlarged schematic diagram at F, G, and H, that is, Figure 12 to Figure 14 , and Fig.11 The enlarged schematic diagram of the reticulated protrusions is shown. Figure 12 to Figure 14In the figure, the mesh protrusions are represented by two different sizes of grids because the large grids represent the mesh protrusions 102 arranged on the inner wall of the box body, while the small grids represent the mesh protrusions 102 arranged on the reinforcing ribs 101. The drawings in the specification of the present invention are only for ease of viewing, but the grids, regardless of their size, represent the mesh protrusions 102.

[0110] In this embodiment, the crankcase body 2 is a hexahedron. In the spatial rectangular coordinate system, the upper and lower bottom surfaces of the body 2 are located in the X-axis direction; the length direction of the crankshaft is located in the Z-axis direction, that is, the side where the two bearing seat holes 1 are located is located in the Z-axis direction; the third side and the fourth side where the two cylinder guide holes are located are arranged opposite to each other and are located in the Y-axis direction.

[0111] The reinforcing ribs 101 are fixedly arranged on the inner wall of the housing 2. The reinforcing ribs 101 include circular reinforcing ribs and strip reinforcing ribs. The circular reinforcing ribs are arranged around each hole. The extension lines of the strip reinforcing ribs on the side where the two bearing seat holes 1 are located will pass through the center of the circle of the bearing seat hole 1. In addition, a number of strip reinforcing ribs parallel to the length direction of the crankshaft are arranged on the side where the two bearing seat holes 1 are located. The circular reinforcing ribs make the inner surface of the housing 2 corresponding to each hole locally thickened, that is, the inner and outer surfaces of the housing 2 corresponding to each hole on the housing 2 are locally thickened. The reinforcing ribs 101 are made of aluminum alloy.

[0112] The mesh protrusion 102 is arranged on the inner wall of the box body 2 without the reinforcing rib 101. The grids in the mesh protrusion 102 can be rhombus, circular, etc., and the shape of the grid is not a limitation to the present invention.

[0113] Optionally, the reinforcing rib 101 is also provided with a mesh protrusion 102 .

[0114] Optionally, the inner wall of the box body 2, the reinforcing ribs 101 and the mesh protrusions 102 are all sprayed with sound absorbing material. In this embodiment, the sound absorbing material is a Teflon composite sound absorbing material.

[0115] In this embodiment, the height h1 of the reinforcing rib 101 is ≤5 mm, and the height h2 of the mesh protrusion 102 is ≤2 mm.

[0116] The noise reduction structure of the present invention is arranged on the inner wall of the crankcase body 2, and the noise reduction structure includes reinforcing ribs 101 and mesh protrusions 102. When the reinforcing ribs 101 are arranged alone, the structural strength and rigidity of the crankcase body 2 can be increased, and when the mesh protrusions 102 are arranged alone, the local strength and rigidity of the arranged position in the body 2 can be increased; and at the reinforcing ribs 101 provided with the mesh protrusions 102, it was found through multiple tests and experiments by technical personnel that not only the strength and rigidity of the reinforcing ribs 101 are further improved, but also the local strength and rigidity of the mesh protrusions 102 around the reinforcing ribs 101 are further improved, and the overall structural strength and rigidity of the body 2 are greatly improved. Furthermore, part of the high-frequency noise is directly absorbed by the sound-absorbing material, and the noise reduction structure and the inner wall of the box body 2 sprayed with the sound-absorbing material make the entire inner cavity of the box body 2 a resistive silencer, which not only avoids the increase of noise caused by the resonance of the crankcase, but also the noise sound waves will convert the sound energy into heat energy due to friction during the propagation of the noise in the box body 2, so that the noise will decay with the propagation distance, thereby achieving the effect of reducing noise. At the same time, the frictional heat generated during the silencer process will be carried out of the crankcase from the exhaust hole by the airflow.

[0117] The interior of the crankcase is viewed from the side where the bearing seat hole 1 is located. Fig.10 As shown in the middle rectangle, Fig.10 The middle circular area is the rotation area that must be reserved for the rotational movement of the crankshaft and other parts, and the intake and exhaust pipes extending to the inside of the housing 2 are all outside the rotation area (i.e., the shaded area). Compared with the prior art of overall thickening of the crankcase, the prior art will not only greatly increase the weight of the crankcase, but also, in order to ensure that the rotation area in the crankcase is not compressed, the crankcase can only increase in volume, which will directly lead to a further increase in the volume of the compressor equipped with the crankcase, and increase the space occupied by the compressor. The noise reduction structure and its setting method in the present invention have extremely small space requirements, so the volume of the crankcase does not need to be increased and the rotation area inside it will not be compressed, which improves the space utilization rate in the crankcase and avoids increasing the space occupied by the compressor. The resistive muffler in the housing 2 of the present invention will only slightly increase the weight of the crankcase, but can greatly enhance the strength and rigidity of the crankcase, and can also greatly reduce the noise generated by the crankcase and the noise transmitted from the crankcase. Compared with the prior art, the noise reduction structure in the present invention also saves material usage and reduces manufacturing costs.

[0118] One end of the intake pipe is connected to the external environment, and the other end of the intake pipe extends to the inside of the case 2, while one end of the exhaust pipe extends to the inside of the case 2, and the other end of the exhaust pipe is connected to the compressor cylinder head. The noise generated by other parts of the compressor mainly enters the crankcase along the exhaust pipe from the end of the exhaust pipe connected to the cylinder head, and then is transmitted to the air along the intake pipe. In this process, the noise entering the crankcase also belongs to the noise inside the crankcase, and the noise transmitted from the crankcase belongs to the noise transmitted from the crankcase, although they are not actually generated and transmitted in the crankcase. For the sake of convenience of description, the noise of this propagation path is recorded as external noise. Because the cross-sectional area of ​​the interior of the housing 2 in any direction is greater than or equal to the circumferential cross-sectional area of ​​the intake pipe or the exhaust pipe, and the change in the cross-sectional area is abrupt, it will change the structural acoustic impedance, thereby causing reflection and interference of sound waves. Therefore, the intake pipe, the exhaust pipe and the housing 2 are equivalent to two series-connected internally inserted expansion chamber mufflers (exhaust pipe→inside the housing 2, inside the housing 2→intake pipe) during the propagation of external noise. That is, the present invention not only forms an expansion chamber muffler with the crankcase, the intake pipe and the exhaust pipe, but also sets the housing 2 as a resistive muffler, which can effectively prevent external noise from being transmitted from the crankcase.

[0119] While keeping the total volume of the crankcase unchanged, the technicians compared the effects of the prior art crankcase and the crankcase of the present invention in various aspects. The prior art crankcase reduces noise by thickening the crankcase body, while the crankcase of the present invention is provided with noise reduction structural reinforcement ribs and sprayed with sound absorbing materials. Compared with the prior art crankcase, the weight increase of the crankcase of the present invention is -11%, the stiffness increase is -0.12%, and under the same working conditions, the noise around the crankcase is reduced by 10.56%. It can be seen that the crankcase of the present invention has greatly reduced the weight and noise of the crankcase while maintaining the same stiffness compared with the prior art crankcase, saving manufacturing costs.

[0120] The crankcase of the present invention does not need to increase the thickness of the case body. By arranging air inlet holes and exhaust holes on the case body and limiting the positions of the air inlet holes and exhaust holes on the case body, the heat in the case body 2 and the compressed gas leaked from the cylinder during operation can be promptly brought out of the crankcase through the two air flow directions in the case body, thereby ensuring that the air pressure and temperature in the crankcase are always appropriate, dissipating heat in time, efficiently compressing the air, and extending the life of the crankcase.

[0121] Therefore, the crankcase of the present invention will not produce a situation where the pressure in the case 2 is too high, thereby avoiding damage to gaskets and seals and oil leakage caused by the excessive pressure in the case 2.

[0122] The crankcase of the present invention has a good noise reduction effect:

[0123] ①The eccentric design of the cylinder hole reduces the lateral force on the cylinder and reduces the noise generated when the crankcase assembly moves.

[0124] ② A noise reduction structure including reinforcing ribs 101 and mesh protrusions 102 is provided on the inner wall of the housing 2, and sound-absorbing material is sprayed on the noise reduction structure. Compared with the prior art of overall thickening of the crankcase, the noise reduction structure and its arrangement method in the present invention require very little space, so the volume of the crankcase does not need to be increased and the rotating area inside it will not be compressed, thereby improving the space utilization rate inside the crankcase and avoiding increasing the space occupied by the compressor. In addition, the resistive silencer in the housing 2 of the present invention will only slightly increase the weight of the crankcase, but can greatly enhance the strength and rigidity of the crankcase, and can also greatly reduce the noise generated by the crankcase and the noise transmitted from the crankcase.

[0125] ③ The air intake pipe extends from the outside of the box body 2 through the air intake hole 5 to the inner cavity of the box body 2, and the first exhaust pipe and the second exhaust pipe extend from the outside of the box body 2 through the first exhaust hole 31 and the second exhaust hole 41 to the inner cavity of the box body 2 respectively. The air intake pipe, the exhaust pipe and the box body 2 are equivalent to two series-connected inner-insertion-tube expansion chamber silencers in the process of propagation of external noise. The noise reduction structure sprayed with sound-absorbing material and the inner wall of the box body 2 make the entire inner cavity of the box body 2 a resistive silencer. That is, on the basis of forming an expansion chamber muffler with the intake pipe and the exhaust pipe, the present invention also sets a resistive muffler in the case 2, which not only avoids the increase of noise caused by the resonance of the crankcase, but also converts the sound energy into heat energy due to friction during the propagation of the noise sound wave in the case 2, so that the noise decays with the propagation distance. The timely heat dissipation function of the crankcase of the present invention can also ensure that the frictional heat generated during the muffler process will be carried out of the crankcase from the exhaust hole by the airflow. Therefore, the crankcase of the present invention can effectively prevent external noise from being transmitted from the crankcase, while also ensuring that the air pressure and temperature in the crankcase are always suitable.

[0126] Example 2

[0127] The present invention also provides a method for designing a low-noise crankcase, which further designs a low-noise crankcase as described in Example 1 to improve its noise reduction effect, comprising the following steps:

[0128] S1, after obtaining the initialized crankcase, simulating the external noise of the initialized crankcase under the working environment, and collecting the external noise parameters on the initialized crankcase;

[0129] S2, after calculating the optimal values ​​of several specification parameters in the initialized crankcase according to the external noise parameters, the corresponding specification parameters of the initialized crankcase are adjusted to obtain a finished crankcase.

[0130] In S1, the initialized crankcase is a low-noise crankcase as described in Example 1, the case body 2 is a hexahedron, and the third side is opposite to the fourth side, the third side is provided with a first exhaust hole 31, the fourth side is provided with a second exhaust hole 41, and a noise reduction structure is provided in the case body 2.

[0131] In S1, the external noise parameters on the crankcase are collected and initialized, including the sound pressure of the forward sound wave of the first exhaust port 31 , the sound pressure of the reverse sound wave of the first exhaust hole 31 , the sound pressure of the sound wave forward of the second exhaust hole 41 , the sound pressure of the reverse sound wave of the second exhaust hole 41 , Sound pressure of the forward sound wave at the air inlet 5 , Sound pressure of reverse sound wave at air inlet 5 , an area S1 of the first exhaust hole 31 , an area S2 of the second exhaust hole 41 , and an area S4 of the air inlet hole 5 .

[0132] The initialized crankcase can be obtained through finite element simulation, and the external noise simulation of the initialized crankcase under the working environment is also carried out through simulation, and the external noise parameters on the initialized crankcase can also be directly obtained in the simulation; the initialized crankcase can also be a physical object made by technicians based on experience, and the external noise simulation of the initialized crankcase under the working environment is for technicians to simulate the external noise generated by other parts of the compressor to propagate in the initialized crankcase, and the external noise parameters are collected through sound pressure sensors set at corresponding positions.

[0133] In S2, the following sub-steps are also included:

[0134] S21, when the first exhaust hole 31 and the second exhaust hole 41 are opened at the same time, the sound pressure cancellation constraint condition and the sound elimination amount objective function are constructed according to the external noise parameters:

[0135] The sound pressure cancellation constraint is:

[0136] ;

[0137] The objective function of sound attenuation is:

[0138] ;

[0139] Among them, e is a natural constant; Indicates the amount of sound attenuation; Indicates the sound pressure of the forward sound wave at the geometric center of the box; It represents the reverse sound pressure of the acoustic wave at the geometric center of the housing 2; S3 represents the cross-sectional area of ​​the side parallel to the bearing seat hole 1 at the geometric center of the housing 2, which is also the area of ​​the expansion chamber; m represents the expansion ratio, m=S3 / S2; L is the first spacing, which represents the straight-line distance between the center of the air inlet 5 and the center of the first exhaust hole 31; K represents the noise wave number, and K is determined as long as the noise is determined; i represents the harmonic number of the noise, which is divided into 1, 2, 3, ... according to the multiples of the fundamental frequency.

[0140] S22, under the constraint of sound pressure cancellation, find the maximum value of the noise reduction objective function max And the corresponding optimal reverse sound wave sound pressure at the geometric center of box 2 , the best forward sound wave sound pressure at the geometric center of box 2 , optimal expansion chamber area S 3,best and the optimal first spacing L best .

[0141] S23, based on the optimal expansion chamber area S 3,best and the optimal first spacing L best Adjust the corresponding specification parameters of the initialized crankcase to obtain a finished crankcase.

[0142] In S22, the Lagrange multiplier method may be used to find the maximum value of the noise reduction target function. The specific method for finding the maximum value of the noise reduction target function is not intended to limit the present invention.

[0143] The expansion chamber area and the first spacing are both specifications of the crankcase.

[0144] During the process of designing the crankcase, technicians can determine the noise data in the working environment based on experience and data collection of the crankcase working environment. For the convenience of description, it will be uniformly referred to as working noise in the following. That is, the technicians design the crankcase when the working noise is determined, and modify the specification parameters on the initialized crankshaft to obtain the finished crankcase with the best noise reduction effect.

[0145] The technicians usually preset the area S1 of the first exhaust hole 31, the area S2 of the second exhaust hole 41 and the area S4 of the intake hole 5 according to their experience, and then combine the determined working condition noise to obtain all the external noise parameters on the current initialization crankcase, and then use a design method of a low-noise crankcase in this embodiment to obtain the optimal expansion chamber area S corresponding to the current initialization crankcase. 3,best and the optimal first spacing L best Then the technician adjusts the expansion chamber area S3 on the initial crankcase and the first spacing L to the optimal expansion chamber area S3. 3,best and the optimal first spacing L bestAfter that, you can get the finished crankcase with the best noise reduction effect.

[0146] When all external noise parameters on the currently initialized crankcase are determined, the technicians obtain multiple corresponding test crankcases by arbitrarily taking values ​​of the expansion chamber area S3 and the first spacing L multiple times. Then, after detecting the noise around each test crankcase under operating noise, it is found that the noise around all test crankcases is more than 5% greater than the noise around the finished crankcase obtained by the design method of this embodiment. This shows that the design method of this embodiment can indeed further enhance the noise reduction effect of the low-noise crankcase described in Example 1, and reduce the noise transmitted from the inside to the outside of the crankcase.

[0147] Optionally, replace S22~S23 with S22´:

[0148] S22', record the initial crankcase with known expansion chamber area S3 and first spacing L as the known crankcase, and record the noise reduction amount calculated by the current known crankcase according to the sound pressure compensation constraint condition and the noise reduction amount objective function as the rated noise reduction amount △L * , if the rated noise reduction volume △L * If the noise reduction value is less than the set noise reduction threshold value △L0, the specification parameters of the currently known crankcase are adjusted and the rated noise reduction value is calculated again until the rated noise reduction value is above the set noise reduction value threshold value △L0. At this time, the specification parameters of the known crankcase are the optimal values, and the known crankcase at this time is the finished crankcase.

[0149] If the technician presets all the specification parameters in the initialized crankcase, which is the case described in S22', the initialized crankcase becomes a known crankcase. However, in order to ensure the noise reduction effect, we still need to calculate whether the rated noise reduction of the current known crankcase meets the set noise reduction threshold. If not, the technician still needs to modify one or more specification parameters in the known crankcase until the modified crankcase meets the set noise reduction threshold. At this time, the known crankcase is a finished crankcase. That is, the design method of a low-noise crankcase in this embodiment can also provide guidance for the improved design of improving the noise reduction effect of the known crankcase.

[0150] Noise reduction It can also be used to reflect the noise reduction performance of a known crankcase. The larger it is, the better the muffler performance of the crankcase is known to be.

[0151] Example 3

[0152] The present invention also provides a method for evaluating the assembly accuracy of a low-noise crankcase, which is applied to a finished low-noise crankcase obtained in Example 1, or a finished low-noise crankcase obtained by a design method for a low-noise crankcase in Example 2.

[0153] Fig.16 The relevant parts in the crankcase Fig. 9 Schematic diagram of the position under viewing angle, because Fig.16 The main purpose is to illustrate the positional relationship of the relevant components in the crankcase. For ease of viewing, the crankcase is simplified (for example, the bottom mounting holes 9 are not drawn, and the noise reduction structure in the crankcase is not drawn, etc.). Fig.16 In the housing 2, the cylinder J7 is installed in the cylinder guide hole, the piston J8 is installed in the cylinder J7, the piston pin J9 is arranged in the piston pin seat of the piston J8, the bearing seat J2 is partially nested in the bearing seat hole 1 on the first side, the bearing J1 is nested in the bearing seat J2, the bearing J1 is sleeved on one end of the crankshaft J3, the small end of the connecting rod J4 is connected to the piston J8, and the big end of the connecting rod J4 is connected to the crankshaft J3. Specifically, the connecting rod big end bearing J5 is nested in the big end of the connecting rod J4, the connecting rod big end bearing J5 is sleeved on the crankshaft J3, the connecting rod small end bearing J6 is nested in the small end of the connecting rod J4, and the connecting rod small end bearing J6 is sleeved on the piston pin J9 in the piston J8.

[0154] Therefore, "parts and components related to the crankcase" include bearing J1, bearing seat J2, crankshaft J3, connecting rod J4, connecting rod big end bearing J5, connecting rod small end bearing J6, cylinder J7, piston J8 and piston pin J9. "Parts and components related to the crankcase" and the crankcase can together form a component ring and / or a closed ring in the plane dimension chain.

[0155] Fig.16 The cylinder J7 is installed in the second-level cylinder guide hole 42. The cylinder J7 of this embodiment can also be installed in the first-level cylinder guide hole 32, or the first-level cylinder guide hole 61, or the second-level cylinder guide hole 62; that is, the cylinder J7 in this embodiment can be the first-level cylinder, the first-level cylinder, the second-level cylinder, or the second-level cylinder.

[0156] Fig.15 It is the schematic diagram of the plane dimension chain of the crankcase, D1~D 10 Indicates the constituent rings numbered 1 to 10, The closed ring is made by connecting each component ring with the closed ring end to end. The plane dimension chain of the crankcase parts is established according to the matching relationship. The specific meanings of each component ring and the closed ring are combined. Figure 16 to Figure 18 To explain, Figure 17-18 for Fig.16 The enlarged schematic diagram of the position α in the middle: D1 represents the distance from the outer end surface of the crankcase to the bottom surface of the bearing mounting hole inside the bearing seat. Fig.16 Indicated by red line segment; D2 represents the width of the bearing, D3 represents the distance between the crankshaft bearing mounting surface and the connecting rod big end bearing mounting surface, Fig.16Indicated by the blue line segment; D4 represents the distance between the end face of the connecting rod big end bearing and the plane passing through the center point of the bearing and perpendicular to the axis. Fig.16 Indicated by purple line segment; D5 represents the distance between the end face of the connecting rod small end bearing and the plane passing through the center point of the small end bearing and perpendicular to the axis. Fig.17 Indicated by yellow line segment; D6 represents the distance between the inner hole end face of piston pin seat and the center section of piston. Fig.17 Indicated by brown line segment; D7 represents the piston radius, D8 represents the gap between the piston and the cylinder, Fig.18 Indicated by orange line segment; D9 represents the inner radius of the cylinder center hole. Fig.18 Indicated by black line segment; D 10 Indicates the distance between the center axis of the cylinder and the first side mounting surface of the crankcase. Fig.16 Indicated by pink line segments; Indicates the distance between the end face of the connecting rod small end bearing and the end face of the inner hole of the piston pin seat. Fig.18 Indicated by red line segments.

[0157] A method for evaluating the assembly accuracy of a low-noise crankcase, such as Fig.19 As shown, the following steps are included:

[0158] Based on the dimensions of the current crankcase and its related parts, plane dimension chains with each cylinder as a closed ring are established to calculate the dimension range of each cylinder closed ring in the current crankcase. If the dimension range of each cylinder closed ring in the current crankcase is within the set allowable range, the assembly accuracy of the current crankcase is qualified; otherwise, the assembly accuracy of the current crankcase is unqualified.

[0159] Calculating the size range of any cylinder sealing ring in the current crankcase also includes the following sub-steps:

[0160] Step 11, calculate the intermediate deviation of each component ring in the current crankcase :

[0161] ,

[0162] in, Indicates the middle deviation of the component ring numbered n; represents the actual measured value of the p-th component and / or crankcase in the production batch of the pre-assembled components and / or crankcases constituting the component ring numbered n, 1≤p≤N and p is a positive integer, that is, the total number of components corresponding to the current batch is N; Represents the predicted value of the production batch of pre-assembled parts and / or crankcases constituting the component ring number n.

[0163] For example, the component ring D7 of the component number 7 is the piston J8, then represents the actual measured radius of the pth piston in a production batch of N pistons (i.e., pre-assembled parts) that we want to assemble; Represents the predicted value of the piston radius for the production batch of pistons (i.e. pre-assembled parts) that we want to use for assembly.

[0164] To calculate the intermediate deviation of a component ring in a crankcase, a batch of parts and / or crankcases manufactured by a manufacturer is used. Based on the design dimensions of the parts and / or crankcases and the knowledge of the manufacturer, the technician can determine the predicted value of the current batch of parts and / or crankcases. The total number of parts and / or crankcases in the current batch of the parts is recorded as N. For the same part, if the manufacturer is different, then Different manufacturers have different control over processing accuracy, so the corresponding Also different.

[0165] The manufacturer's control over processing accuracy will affect assembly accuracy.

[0166] Step 12: Establish the plane dimension chain of the crankcase according to the matching relationship and calculate the closed loop Middle Deviation:

[0167] ,

[0168] in, Represents a closed loop The middle deviation of represents the transmission coefficient of the component ring numbered n, represents the relative asymmetry coefficient of the constituent ring numbered n, Indicates the tolerance of the component ring numbered n.

[0169] A person skilled in the art can determine the following when the closed loop and the constituent loop are determined: , and The specific calculation process will not be described in detail.

[0170] Step 13, calculate the closed ring size range CL of cylinder J7 by probability method:

[0171] ,

[0172] in, Indicates the corresponding component ring The nominal size of the closed loop; k0 represents the relative distribution coefficient of the closed loop; Indicates the corresponding component ring The relative distribution coefficient.

[0173] Repeat steps 11 to 13, and then the first-level cylinder closed ring size range, the first-level cylinder closed ring size range, the second-level cylinder closed ring size range and the second-level cylinder closed ring size range under the current crankcase specification parameters can be calculated respectively, that is, the calculation of the cylinder closed ring size range in the current crankcase is completed.

[0174] In this embodiment, the setting allowable range of the first and second stage cylinders is 1 mm. 0.2mm, the setting range of the first and second cylinders is 0.9mm 0.2mm.

[0175] In the assembly accuracy evaluation method of this embodiment, before the actual assembly operation is performed, the size range of each cylinder closing ring in the current crankcase is calculated once to accurately determine whether the assembly accuracy of the current crankcase is qualified, thereby reducing the crankcase noise caused by low assembly accuracy.

[0176] Example 4

[0177] The present invention also provides a method for assembling a low-noise crankcase, comprising the following steps:

[0178] Step 1: using a low-noise crankcase assembly accuracy evaluation method as described in Example 3 to determine whether the assembly accuracy of the current crankcase is qualified;

[0179] Step 2: If the assembly accuracy of the current crankcase is qualified, the current crankcase and various parts related to the crankcase are directly assembled; if the assembly accuracy of the current crankcase is unqualified, the technician adjusts the size of the crankcase and / or various parts related to the crankcase, and returns to step 1 until the assembly accuracy of the crankcase is qualified.

[0180] If the size range of the closed ring of the first-stage cylinder, the first-stage cylinder, the second-stage cylinder or the second-stage cylinder in the current crankcase is within the corresponding set allowable range, it is determined that the assembly accuracy of the current crankcase meets the low noise requirement, that is, the assembly accuracy of the current crankcase is qualified, and the crankcase and various parts related to the crankcase do not need to modify their sizes and can be directly assembled; otherwise, it means that the assembly accuracy of the current crankcase does not meet the low noise requirement, and the assembly accuracy of the current crankcase is unqualified. The technician recalculates the assembly accuracy of the crankcase after adjusting the sizes of the crankcase and / or various parts related to the crankcase until the crankcase and various parts related to the crankcase do not need to modify their sizes and can be directly assembled.

[0181] During the assembly process, the dimensional modification range of the crankcase-related components is very small. For example, the distance between the crankshaft bearing mounting surface and the connecting rod big end bearing mounting surface is reduced by 0.1 mm. This modification is for the convenience of assembly and is far from comparable to the rule parameter modification range performed by the design method in Example 2.

[0182] Because the crankcase needs to be installed in the compressor for subsequent use, and the parts related to the crankcase also need to be installed in the crankcase. Although the various design tolerances of the crankcase and these parts are marked on the design drawings, different parts manufacturers have different controls on processing accuracy, which will lead to inappropriate tolerances between the crankcase and related parts. Not only is the assembly accuracy low, but also due to the accumulation of tolerances, the original single size tolerance of the crankcase is affected by the tolerances of multiple components, indirectly affecting the positional relationship of each friction pair, making the wear of the friction pairs uneven, the local wear more serious, and the mechanical noise getting louder and louder.

[0183] The assembly method of a low-noise crankcase using the present embodiment can ensure that only the crankcase and the crankcase-related components whose assembly accuracy meets the low-noise requirements can be directly assembled. Otherwise, the technicians will need to adjust the dimensions of the crankcase and the crankcase-related components to meet the low-noise requirements.

[0184] Assembly method of prior art: During the assembly of the crankcase and its related parts, if it is found that the assembly error is too large and the position is inaccurate due to low assembly accuracy, the related parts are disassembled and the dimensions of the crankcase and / or the related parts are slightly adjusted.

[0185] The assembly method of the prior art will assemble the crankcase and some parts related to the crankcase when the assembly accuracy is too low. Even if it is disassembled and adjusted later, the crankcase and related parts will be irreversibly damaged, thereby reducing the adjustment efficiency, and further reducing the efficiency of the entire assembly process; and the assembly accuracy after adjustment can only be relatively improved, reducing some noise caused by low assembly accuracy. Before assembly, the assembly method of the present invention accurately controls whether the assembly accuracy between the current crankcase and some parts related to the crankcase is qualified by calculating the size range of all cylinder sealing rings in the current crankcase. Only the crankcase with qualified assembly accuracy and some parts related to the crankcase can be assembled, so that the crankcase and some parts related to the crankcase only need to be assembled once, without multiple disassembly and adjustment, avoiding assembly damage to reduce the adjustment efficiency, and the efficiency of the entire assembly process is high. The assembly method of the present invention greatly improves the assembly accuracy and greatly reduces the crankcase noise caused by low assembly accuracy. The crankcase noise is further reduced on the basis of reducing the crankcase noise by the design method of embodiment 2.

[0186] It has been confirmed through multiple tests by technical personnel that, compared with the assembly method of the prior art, the assembly method of this embodiment improves the assembly efficiency by an average of more than 23.6% and the noise reduction by an average of more than 4.5%.

[0187] The techniques, shapes, and structural parts not described in detail in the present invention are all well-known techniques.

[0188] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for evaluating the assembly accuracy of a low-noise crankcase, characterized in that: Includes the following: Based on the dimensions of the current crankcase and the relevant parts of the current crankcase, plane dimension chains with each cylinder as a closed ring are established respectively, and the dimension range of each cylinder closed ring in the current crankcase is calculated; if the dimension range of each cylinder closed ring in the current crankcase is within the set allowable range, the assembly accuracy of the current crankcase is qualified; otherwise, the assembly accuracy of the current crankcase is unqualified; Calculating the size range of any cylinder sealing ring in the current crankcase also includes the following sub-steps: Step 11, calculate the intermediate deviation of each component ring in the current crankcase : = ， in, Indicates the middle deviation of the component ring numbered n; represents the actual measured value of the pth component and / or crankcase in the production batch of the pre-assembled components and / or crankcases constituting the component ring numbered n, 1≤p≤N and p is a positive integer, that is, the total number of components corresponding to the current batch is N; Indicates the predicted value of the production batch of the pre-assembled parts and / or crankcases constituting the component ring number n; Step 12, establish the plane dimension chain of the crankcase according to the matching relationship, and calculate the intermediate deviation of the closed loop △D: ， in, Indicates the middle deviation of the closed loop △D; represents the transmission coefficient of the component ring numbered n; Represents the relative asymmetry coefficient of the constituent ring numbered n; Indicates the tolerance of the component ring numbered n; D1~D 10 Indicates the component rings numbered 1 to 10; Step 13, calculate the closed ring size range CL of the cylinder by probability method: ， in, Indicates the corresponding component ring The nominal size of the closed loop; k0 represents the relative distribution coefficient of the closed loop; Indicates the corresponding component ring The relative distribution coefficient of The crankcase comprises a case body (2), the case body (2) being a polyhedron having a number of faces greater than or equal to 5, the case body (2) comprising an upper bottom surface, a first side surface, a second side surface, a third side surface and a fourth side surface, two coaxial bearing seat holes (1) being respectively arranged on the first side surface and the second side surface, an air inlet hole (5) being provided on the upper bottom surface, and a first exhaust hole (31) and a first first-stage cylinder guide hole (32) being provided on the third side surface; a noise reduction structure for reducing noise inside the case body is provided on the inner wall of the case body (2); The first exhaust hole (31) is arranged directly below or directly above the first first-stage cylinder guide hole (32) or on a side of the first first-stage cylinder guide hole (32) away from the air inlet hole (5); a second exhaust hole (41) and a second first-stage cylinder guide hole (42) are provided on the fourth side surface, and the second exhaust hole (41) is arranged directly below or directly above the second first-stage cylinder guide hole (42) or on a side of the second first-stage cylinder guide hole (42) away from the air inlet hole (5); A second secondary cylinder guide hole (62) is also provided on the fourth side surface, and the second secondary cylinder guide hole (62) is arranged on a side of the second primary cylinder guide hole (42) close to the air inlet hole (5).

2. The method for evaluating the assembly accuracy of a low-noise crankcase according to claim 1, characterized in that: The noise reduction structure comprises reinforcing ribs (101) and mesh protrusions (102), wherein the reinforcing ribs (101) and the mesh protrusions (102) are both arranged on the inner wall of the housing (2); the reinforcing ribs (101) comprise two types, namely circular reinforcing ribs and strip reinforcing ribs, wherein the circular reinforcing ribs are arranged around each hole; the extension lines of the strip reinforcing ribs on the first side surface and the second side surface pass through the center of the circle of the bearing seat hole (1), and a plurality of strip reinforcing ribs parallel to the length direction of the crankshaft are arranged on the upper bottom surface, the third side surface and the fourth side surface; the housing (2), the inner wall reinforcing ribs (101) and the mesh protrusions (102) are all sprayed with sound absorbing material.

3. The method for evaluating the assembly accuracy of a low-noise crankcase according to claim 1, characterized in that: A first and second-stage cylinder guide hole (61) is also provided on the third side surface, and the first and second-stage cylinder guide hole (61) is arranged on a side of the first exhaust hole (31) away from the air inlet hole (5); An air intake pipeline extends from the outside of the housing (2) through the air intake hole (5) into the inner cavity of the housing (2); a first exhaust pipeline and a second exhaust pipeline extend from the outside of the housing (2) through the first exhaust hole (31) and the second exhaust hole (41) into the inner cavity of the housing (2); and the outer diameter of each pipeline is the same as the diameter of the corresponding air intake hole or exhaust hole.

4. The method for evaluating the assembly accuracy of a low-noise crankcase according to claim 3, characterized in that: A plane parallel to the upper bottom surface, perpendicular to the third side surface and passing through the center of the first primary cylinder guide hole (32) is recorded as a first plane, a plane parallel to the upper bottom surface, perpendicular to the third side surface and passing through the center of the first secondary cylinder guide hole (61) is recorded as a second plane, a plane parallel to the upper bottom surface, perpendicular to the fourth side surface and passing through the center of the second primary cylinder guide hole (42) is recorded as a third plane, and a plane parallel to the upper bottom surface, perpendicular to the fourth side surface and passing through the center of the second secondary cylinder guide hole (62) is recorded as a fourth plane. The first plane does not overlap with the second plane, and the third plane does not overlap with the fourth plane.

5. The method for evaluating the assembly accuracy of a low-noise crankcase according to claim 3, characterized in that: The crankcase-related components include bearings, bearing seats, crankshafts, connecting rods, connecting rod big end bearings, connecting rod small end bearings, cylinders, pistons and piston pins; D1 represents the distance from the outer end surface of the crankcase to the bottom surface of the bearing mounting hole inside the bearing seat; D2 represents the width of the bearing, D3 represents the distance between the bearing mounting surface on the crankshaft and the connecting rod big end bearing mounting surface; D4 represents the distance between the connecting rod big end bearing end surface and the plane passing through the bearing center point and perpendicular to the axis; D5 represents the distance between the connecting rod small end bearing end surface and the plane passing through the small end bearing center point and perpendicular to the axis; D6 represents the distance between the inner hole end surface of the piston pin seat and the center section of the piston; D7 represents the piston radius, D8 represents the gap between the piston and the cylinder; D9 represents the inner radius of the cylinder center hole; D 10 It indicates the distance between the center axis of the cylinder and the first side mounting surface of the crankcase; △D indicates the distance between the end face of the connecting rod small end bearing and the end face of the inner hole of the piston pin seat.

6. A method for evaluating the assembly accuracy of a low-noise crankcase according to any one of claims 3 to 5, characterized in that: Obtaining a finished crankcase prior to assembly involves the following steps: S1, after obtaining the initialized crankcase, simulating the external noise of the initialized crankcase under the working environment, and collecting the external noise parameters on the initialized crankcase; S2, after calculating the optimal values ​​of several specification parameters in the initialized crankcase according to the external noise parameters, the corresponding specification parameters of the initialized crankcase are adjusted to obtain a finished crankcase.

7. The method for evaluating the assembly accuracy of a low-noise crankcase according to claim 6, characterized in that: In S1: the external noise parameters include the sound pressure of the forward sound wave of the first exhaust hole (31) , the sound pressure of the reverse sound wave of the first exhaust hole (31) , the sound pressure of the forward sound wave of the second exhaust hole (41) , the sound pressure of the reverse sound wave of the second exhaust hole (41) 、Intake hole (5) Sound pressure of the forward sound wave 、Sound pressure of reverse sound wave at air inlet (5) , an area S1 of the first exhaust hole (31), an area S2 of the second exhaust hole (41), and an area S4 of the air inlet hole (5); In S2, the following sub-steps are also included: S21, the first exhaust hole (31) and the second exhaust hole (41) are opened simultaneously, and a sound pressure cancellation constraint condition and a sound attenuation target function are constructed according to the external noise parameters: The sound pressure cancellation constraint is: ， The objective function of noise reduction is: ×lg[ + ]; Among them, e is a natural constant; Indicates the amount of sound attenuation; represents the sound pressure of the forward sound wave at the geometric center of the box (2); represents the reverse sound wave pressure at the geometric center of the housing (2); S3 represents the expansion chamber area, which is the cross-sectional area of ​​the side parallel to the bearing seat hole (1) at the geometric center of the housing (2); m represents the expansion ratio, m=S3 / S2; L is the first spacing, which represents the straight-line distance between the center of the air inlet (5) and the center of the first exhaust hole (31); K represents the noise wave number; i represents the harmonic number of the noise; S22, under the constraint of sound pressure cancellation, find the maximum value of the noise reduction objective function △L max And the corresponding optimal reverse sound wave sound pressure at the geometric center of the box (2) , the optimal forward sound wave pressure at the geometric center of the box (2) , optimal expansion chamber area S 3,best and the optimal first spacing L best ; S23, based on the optimal expansion chamber area S 3,best and the optimal first spacing L best Adjust the corresponding specification parameters of the initialized crankcase to obtain a finished crankcase.

8. A method for assembling a low-noise crankcase, characterized in that: The following steps are involved: Step 1, using a low-noise crankcase assembly accuracy evaluation method as described in any one of claims 1 to 7 to determine whether the assembly accuracy of the current crankcase is qualified; Step 2: If the assembly accuracy of the current crankcase is qualified, the current crankcase and various parts related to the crankcase are directly assembled; if the assembly accuracy of the current crankcase is unqualified, the technician adjusts the size of the crankcase and / or various parts related to the crankcase, and returns to step 1 until the assembly accuracy of the crankcase is qualified.

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