Impeller for a compressor, method of machining an impeller for a compressor, method of manufacturing an impeller for a compressor, and rolling device

Abstract

Impeller for a compressor comprising a back disc, a hub and blades, wherein the hub is configured in one piece with the back disc and the hub is integrally connected to the roots of the blades at an outer rim, wherein a transition fillet is present between the outer rim of the hub and the roots of the blades, wherein at each transition fillet a rolled region is provided in which a dent is produced as a result of the rolling. By providing a rolled region at the transition fillet of the impeller of the compressor in which a residual compressive stress is produced as a result of the rolling, a "pizza cut" failure can be inhibited or slowed down at the transition fillet region as a result of fatigue when the impeller is in operation. Furthermore, a method for machining an impeller of a compressor, a method for manufacturing an impeller of a compressor and a rolling apparatus are proposed.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of impellers of compressors. In particular, the present invention relates to an impeller of a compressor, a method of machining an impeller of a compressor, a method for manufacturing an impeller of a compressor, and a rolling device.

[0002] The present invention relates to a method of machining an impeller of a rotary machine. The present invention also relates to a fixture for fixing a rotary machine during machining. Furthermore, the present invention relates to a blade for a rotary machine. BACKGROUND

[0003] Impellers of compressors are used for compressing air in turbochargers. The impellers often rotate during operation at speeds of several hundred thousand revolutions per minute, so that fatigue resistance is of great importance.

[0004] There are currently three failure modes of impellers of compressors: "pizza cut", hub burst and backplate failure. In all three fatigue failure modes, the failure is initiated by tensile stresses at the fatigue initiation point.

[0005] For hub burst, in this failure mode, the fatigue crack starts from the hub center bore. Currently, the introduction of residual compressive stresses by a bore expansion process of the hub center bore can suppress crack initiation and propagation in the hub region of the impeller, so that this failure is controlled to some extent.

[0006] For backplate failure, in this failure mode, the fatigue crack starts from the backplate. This failure can be controlled by means of an optimization of the backplate geometry, by means of a surface treatment of the backplate, by means of a finite element analysis and the like.

[0007] As for "pizza cut", in this failure mode, the fatigue crack starts at the hub fillet of the impeller. For this failure mode, there are currently still attempts to find an effective solution or to control the progression of this fatigue failure. SUMMARY

[0008] The present invention was completed in view of the above technical problems, and its task is to provide an impeller for a compressor, which can effectively suppress or slow down the occurrence of the "pizza cut" failure mode at the hub fillets of the impeller. This task is solved by an impeller as described below: The impeller comprises a backplate, a hub and blades, wherein the hub is configured in one piece with the backplate and the hub is integrally connected at an outer rim to the roots of the blades of the impeller, there being a hub fillet between the outer rim of the hub and the root of the blade, the impeller being provided at each hub fillet with a rolled region in which indentations have been produced as a result of rolling.

[0009] In the impeller for a compressor according to the present application, by providing a rolled region at the transition fillet between the outer edge of the hub of the impeller and the root of the blade, the region is formed with a dent due to the deformation caused by the rolling and residual compressive stress is introduced due to the rolling, and these introduced residual compressive stresses are gradually released in the subsequent use of the impeller, can offset the tensile stress generated in operation, inhibit or slow down the "pizza cut" failure due to fatigue at the transition fillet region of the hub of the impeller with the rotation of the impeller, and enhance the resistance of the impeller to the "pizza cut" failure mode.

[0010] Preferably, the depth of the dent in the transition fillet region of the hub of the impeller due to rolling is 0.03 to 0.05 mm.

[0011] It has been found that the permanent dent with a depth in the above range produced by rolling the transition fillet region of the hub of the impeller makes it possible to effectively inhibit the occurrence of "pizza cut" failure in the subsequent operation of the impeller on the one hand, and on the other hand, also avoids that the dent depth produced by the rolling process is too deep to affect the strength of the impeller itself, such as causing a fracture, while also avoiding that the dent depth produced by the rolling process is insufficient to introduce sufficient residual compressive stress, and thus cannot be expected to offset the tensile stress generated during operation of the impeller to inhibit or slow down the occurrence of "pizza cut" failure.

[0012] Preferably, the rolled region of the impeller is located in the range between 0.8 times the outer diameter to 1 times the outer diameter of the impeller.

[0013] It has been found that rolling the transition fillet region of the impeller within the above range to produce a dent can effectively inhibit the occurrence of "pizza cut" failure, and also avoids that the range of the rolled impeller is too large to adversely affect the strength of the impeller itself.

[0014] In an advantageous embodiment of the present application, the rolled region of the impeller is provided such that the surface roughness thereof is superior to that of the unrolled region of the root of the blade of the impeller.

[0015] Here, the rolled transition fillet region of the impeller is provided with a surface roughness that is superior to that of the unrolled region. A superior surface roughness means that there are fewer surface defects such as micro-cracks, scratches, dents, etc. in the rolled region, and these surface defects can become stress concentration points that are prone to become the starting point of fatigue cracks during operation of the impeller. Therefore, a superior surface roughness makes it possible to reduce the stress concentration points that can exist in the transition fillet region of the impeller where "pizza cut" failure is prone to occur.

[0016] Particularly preferably, the rolled region of the impeller has a surface roughness superior to Ra0.4.

[0017] It has been found that the surface roughness of the area of the rolled transition fillet of the impeller is preferably better than Ra 0.4 to better inhibit the occurrence of the "pizza cut" failure during operation of the impeller, while also having a higher cost benefit ratio for the rolling machining of the impeller itself.

[0018] The application also proposes a method for machining an impeller of a compressor. The machining method comprises the following steps: fixing the impeller of the compressor by means of a fixture, wherein the hub of the impeller is integrally connected to the root of the blades of the impeller at the outer edge, and there is a transition fillet between the outer edge of the hub and the root of the blades; positioning a rolling body to align a target area of the transition fillet of the impeller; loading the target area by means of the rolling body and performing at least one rolling, thereby producing indentations in the rolled area.

[0019] The compressed impeller produced by means of the method for machining an impeller of a compressor according to the application can reduce or avoid the occurrence of the "pizza cut" failure mode at the transition fillet of the machined impeller during operation. Specifically, in the method, by performing at least one rolling on the target area of the transition fillet of the impeller of the compressor, thereby producing deformation in the target area where rolling is performed, forming permanently deformed indentations, and introducing residual compressive stress in the target area. During subsequent operation of the machined impeller of the compressor, the introduced residual compressive stress counteracts the tensile stress during operation of the impeller, inhibiting or slowing down the tendency of the "pizza cut" failure to occur at the transition fillet area of the hub of the impeller, thereby improving the resistance of the impeller of the compressor machined by the above-mentioned method to the "pizza cut" failure.

[0020] The application also proposes a method for manufacturing an impeller of a compressor. The manufacturing method comprises the following steps: fixing a blank of the impeller of the compressor by means of a fixture, machining the blank to form a hub of the impeller, blades, so that the hub is integrally connected to the root of the blades at the outer edge, and there is a transition fillet between the outer edge of the hub and the root of the blades; positioning a rolling body to align a target area of the transition fillet of the impeller; loading the target area by means of the rolling body to perform at least one rolling, thereby producing indentations in the rolled area.

[0021] By means of the method for manufacturing an impeller of a compressor according to the present application, an impeller can be manufactured from a blank of an impeller of a compressor, which has a dent formed by rolling and residual compressive stress introduced in the area of the transition fillet of the hub of the impeller, and which can inhibit or slow down the occurrence of "pizza cut" failure at the transition fillet of the hub of the impeller during subsequent operation by the residual compressive stress counteracting the tensile stress generated during operation. In other words, in the manufacturing method, at least one rolling is performed on the target area of the transition fillet between the outer edge of the hub of the impeller and the root of the blade manufactured from the impeller blank, so as to introduce residual compressive stress in the rolled area of the transition fillet. The residual compressive stress is gradually released with the operation of the impeller, so as to inhibit or slow down the occurrence of "pizza cut" failure at the transition fillet of the hub of the impeller.

[0022] In further aspects of the above-mentioned aspects of the method, it is provided that the target area of the transition fillet is rolled 5 to 10 times by means of the rolling body.

[0023] It has been found that in the process of machining or manufacturing the impeller, by performing rolling in the target area of the transition fillet of the impeller within the above-mentioned number of times, sufficient residual compressive stress can be introduced to slow down or inhibit the occurrence of "pizza cut" failure, without affecting the strength of the machined or manufactured impeller due to excessive load applied by a single rolling operation.

[0024] Optionally, in the 5 to 10 times of rolling on the same target area, the load applied by each rolling can be the same, or the first load applied by the first several preliminary rollings can be the same, and the second load applied by the final rolling can be the same, and the first load and the second load are different in size, which is advantageous for forming a dent with a desired depth in the target area of the transition fillet.

[0025] Preferably, in any of the above-mentioned aspects of the method, the method further comprises a step of cooling the rolled area after the target area of the hub of the impeller is loaded for at least one rolling.

[0026] In the method according to the present application, by cooling the rolled area, if necessary, after each rolling, overheating is prevented from occurring at the target area of the transition fillet of the impeller being rolled, which can cause ablation or undesirably introduce cracks in the rolled area, thereby damaging the quality of the machined or manufactured impeller.

[0027] Preferably, in the impeller of the turbine obtained according to any of the above-mentioned aspects of the method, the depth of the dent formed in the rolled area is 0.03 to 0.05 mm.

[0028] It has been found that, in the method for machining or manufacturing a turbine wheel from a blank, the creation of a notch in the target area of the transition fillet of the wheel by rolling, with a depth in the above-mentioned range, makes it possible to effectively inhibit the occurrence of the "pizza cut" failure mode of the turbine wheel being machined or manufactured, on the one hand, and, on the other hand, the notch depth formed in the above-mentioned range limits the number of rolling passes and the magnitude of the load applied during rolling by the machining or manufacturing method claimed when rolling the target area, so that it is possible both to prevent the notch depth created by rolling from being too deep to affect the strength of the wheel itself, for example by causing it to break, and to avoid the notch depth ultimately formed being insufficient to introduce sufficient residual compressive stress and thus to ideally inhibit the occurrence of the "pizza cut" failure at the hub of the wheel being machined or manufactured.

[0029] Preferably, in the variant of any of the above-mentioned methods, it is provided that the rolled area of the fillet transition region of the hub of the wheel is located in a range between 0.8 times the outer diameter and 1 times the outer diameter of the wheel.

[0030] It has been found that, in the machining or manufacturing method according to the application, the rolling of the transition fillet region of the wheel being machined or manufactured in the above-mentioned range makes it possible to effectively inhibit the occurrence of the "pizza cut" failure in the transition fillet region of the hub of the wheel obtained, which avoids the range rolled in the rolling step being too large to adversely affect the strength of the wheel itself, and guarantees the efficiency of the machining or manufacturing method according to the application.

[0031] Preferably, in the variant of the method for manufacturing a compressor wheel from a blank according to the application, it is also provided that the method further comprises, after rolling the target area of one of the transition fillets of the wheel being manufactured from a blank, repositioning the rolling body with respect to the blank to align the area to be rolled of the next transition fillet.

[0032] After the target region of one of the transition fillets of the blank is rolled, the rolling body is repositioned relative to the blank so that it can be aligned with the next transition fillet, for example, the transition fillet adjacent to the previously processed transition fillet in the clockwise direction or in the counterclockwise direction. Specifically, the rolling body is aligned with the target region of the next transition fillet to be rolled so that the rolling body can be positioned to roll against the target region of the next transition fillet to introduce residual compressive stress in the target region of the next transition fillet as well. Finally, the rolling of all the transition fillets of the impeller of the compressor manufactured from the blank is completed by repeating the above steps to introduce residual compressive stress at all the transition fillets of the impeller, thereby suppressing or avoiding the occurrence of the "pizza cut" failure at the transition fillets of the hub of the impeller of the manufactured compressor. Such a manufacturing method of rolling the transition fillets of the manufactured impeller one by one is particularly suitable for manufacturing the impeller of the compressor in an existing manufacturing device of the impeller of the compressor, for example, a CNC machining center, by only adjusting the control unit of the device to add the rolling and repositioning steps without introducing additional machining tools or providing a special device to roll the impeller.

[0033] The present application also proposes a rolling device for the impeller of a compressor, comprising: a fixing device for fixing the impeller of the compressor; a plurality of rolling bodies for rolling; and a control unit configured to process the impeller fixed on the fixing device according to the method of processing the impeller of the compressor to load and roll against the target regions of the transition fillets of the impeller by the plurality of rolling bodies to produce indentations in the rolled regions.

[0034] Therefore, the present application proposes a rolling device specially designed for the impeller of a compressor, and the impeller of the compressor rolled by the specially designed rolling device can introduce residual compressive stress due to the loading or rolling of the plurality of rolling bodies against the target regions of the transition fillets of the impeller to counteract the tensile stress generated when the impeller is in rotation, thereby slowing down or suppressing the occurrence of the "pizza cut" failure at the transition fillets of the hub of the impeller of the compressor processed by the rolling device.

[0035] In the rolling device according to the present application, the target regions of the plurality of transition fillets of the impeller can be rolled and processed to introduce residual compressive stress by controlling the plurality of rolling bodies of the rolling device by the control unit configured to perform the method according to the present application, thereby enabling the target regions of the plurality of transition fillets of the impeller to be simultaneously rolled and processed in one processing, ensuring efficient rolling of the impeller of the compressor, i.e., ensuring efficient introduction of residual compressive stress, and the rolling device is particularly suitable for batch processing of a plurality of impellers of the compressor to improve work efficiency.

[0036] In the context of the present application, "one-time processing" refers to the rolling of the transition fillet of the impeller of the compressor to obtain the desired indentation. In the "one-time processing", the target area of the transition fillet of the impeller of the compressor can be rolled once or multiple times to obtain the desired indentation. Whether the "one-time processing" is completed is determined by whether the desired indentation is obtained, which refers to the indentation having the desired depth / surface roughness and the like.

[0037] Preferably, the depth of the indentation produced by the rolling body of the rolling device according to the present application in the target area of the transition fillet of the impeller is 0.03 to 0.05 mm.

[0038] It has been found that, by means of the rolling device according to the present application, the rolling of the rolling body in the target area of the transition fillet of the impeller produces an indentation with a depth in the above-mentioned range, which can effectively suppress the "pizza cut" failure of the rolled impeller at the transition fillet of the hub during operation, while avoiding the indentation depth being too deep to affect the strength of the impeller itself, such as causing the rolled impeller to break or significantly weaken the strength at the rolled area, and also avoiding the indentation depth being insufficient to introduce sufficient residual compressive stress in the transition fillet area of the impeller, thereby failing to suppress or slow down the occurrence of "pizza cut" failure during subsequent rotation of the impeller.

[0039] Preferably, the rolled area rolled by the rolling body of the rolling device according to the present application is located in the range of 0.8 times the outer diameter to 1 times the outer diameter of the impeller.

[0040] It has been found that the residual compressive stress introduced by rolling the transition fillet of the impeller in the above-mentioned range can prevent the occurrence of "pizza cut" failure during subsequent operation of the rolled impeller, while avoiding the rolling range of the rolling body being too large to adversely affect the strength of the impeller itself, and the rolling range also ensures the working efficiency of the rolling body.

[0041] Preferably, the rolling device according to the present application has a rolling body with a radius size determined to be the same as the radius of the transition fillet of the rolled impeller.

[0042] Here, the radius size of the rolling body of the rolling device is determined to be the same as the radius of the transition fillet of the impeller, which can achieve the highest efficiency in rolling processing of the target area of the transition fillet of the impeller. Therefore, the rolling device can have multiple sets of rolling bodies, each set of rolling bodies having rolling bodies with the same radius, while the rolling bodies of different sets have different radii from each other, so that the rolling device can provide rolling bodies with different sizes according to the radius size of the transition fillet of the compressor impeller being rolled during rolling processing, improving the efficiency of rolling operation of the rolling device, and enabling the rolling device to have a wider range of applications.

[0043] Preferably, the rolling device according to the present application further comprises a cooling device for cooling the rolled surface of the impeller.

[0044] The cooling device of the rolling device can cool the rolled surface of the impeller, and if necessary, the rolling device can further comprise a sensing device for real-time monitoring of the surface temperature of the impeller, so as to prevent overheating in the target area of the transition fillet of the impeller being rolled, which can cause ablation of the surface or introduce cracks in the rolling area, which can damage the quality, especially the strength, of the impeller being rolled.

[0045] Preferably, the hardness of the rolling body in the rolling device according to the present application is at least 20 HRC higher than the hardness of the material of the impeller.

[0046] It has been found that, in the case where the hardness of the rolling body of the rolling device is at least 20 HRC higher than the hardness of the material of the impeller being rolled, residual compressive stress can be effectively introduced into the impeller being rolled and indentations can be formed, so as to inhibit or slow down the occurrence of "pizza cut" failure at the transition fillet of the hub of the impeller during subsequent operation of the impeller by the introduced residual compressive stress counteracting the tensile stress. Similarly, the rolling device can have multiple groups of rolling bodies, each group of rolling bodies having the same hardness, usually being made of the same material, and different groups of rolling bodies having different hardnesses from each other, and the hardness range of the rolling bodies can be selected according to the hardness range of the materials of common turbine impellers, so as to achieve a hardness at least 20 HRC higher than the hardness of the material of the impeller. This makes it possible to quickly select a group of rolling bodies meeting the above hardness requirement according to the hardness of the impeller being rolled when the rolling device is rolling, improves the efficiency of the rolling operation of the rolling device, and makes the rolling device have a wider range of applications.

[0047] For example, in a non-limiting embodiment of the present application, the hardness of the rolling body of the rolling device is 35-40 HRC, for rolling an impeller made of aluminum alloy.

[0048] For example, in another non-limiting embodiment of the present application, the hardness of the rolling body of the rolling device is 55-60 HRC, for rolling an impeller made of titanium alloy.

[0049] It has been found that, for common impellers made of aluminum alloy or titanium alloy, the hardness of the rolling body of the rolling device is configured within the above hardness range, which can effectively introduce residual compressive stress into the impeller being rolled, so as to inhibit or slow down the occurrence of the "pizza cut" failure mode in the impeller during subsequent operation of the impeller by the release of the introduced residual compressive stress.

[0050] Preferably, the rolling device according to the present application further comprises a supporting device for supporting the back disc of the impeller being rolled.

[0051] Here, the supporting device can support the back disc of the impeller of the processed compressor to avoid the load applied by the rolling body affecting the back disc of the impeller and causing deformation when the rolling device rolls the transition fillet area of the impeller. In addition, the arrangement of the supporting device can also fix the back disc to avoid the shaking of the back disc affecting the accuracy of the rolling body when rolling the transition fillet area of the impeller, which will adversely affect the effect of the rolling process.

[0052] In a non-limiting embodiment of the present application, the rolling device further comprises a plurality of loading arms, and the rolling bodies are respectively arranged at the free ends of the loading arms, and the loading arms are configured to drive the rolling bodies to move relative to the impeller.

[0053] Here, the design configuration of the rolling device comprising a plurality of loading arms enables the rolling pressure of the plurality of rolling bodies to be accurately output by the loading arms respectively, so as to ensure that the plurality of rolling bodies uniformly apply the required pressure at each transition fillet area of the rolled impeller, and also ensures that each rolling body is accurately positioned relative to the transition fillet to be rolled and processed.

[0054] Additional features and advantages are described in, and will be apparent from, the following DETAILED DESCRIPTION, which includes the following sections: BRIEF DESCRIPTION OF DRAWINGS

[0055] The technical features of the present application are described in the following claims with reference to the above objects, and the advantages thereof will be apparent from the following detailed description with reference to the attached drawings, which show by way of example the preferred embodiments of the present application, without limiting the scope of the inventive concept.

[0056] Figure 1 a compressor impeller is shown in perspective view;

[0057] Figure 2 a compressor impeller is shown in perspective view;

[0058] Figure 3 a compressor impeller is shown in front view; Figure 2 a compressor impeller is shown in perspective view;

[0059] Figure 4 a compressor impeller is shown in rear view; Figure 2 a compressor impeller is shown in perspective view;

[0060] Figure 5 a flowchart showing the process of processing an impeller in a dedicated rolling device according to the method of the present application;

[0061] Figure 6a flow chart showing the integration of the method according to the present application in the machining of an impeller in a CNC; and

[0062] Figure 7 a flow chart showing the integration of another method according to the present application in the machining of an impeller in a CNC.

[0063] List of reference signs

[0064] 100 impeller

[0065] 101 hub

[0066] 102 blade

[0067] 110 target area

[0068] OD outer diameter DETAILED DESCRIPTION

[0069] Reference will now be made in detail to various embodiments of the present application, examples of which are illustrated in the accompanying drawings and described below. While the present application will be described in conjunction with the exemplary embodiments, it should be understood that the present application is not limited to those exemplary embodiments. On the contrary, the present application is intended to cover all alternatives, modifications, equivalents and other embodiments that can be included within the spirit and scope of the present application as defined by the appended claims. For the purposes of the present application, the terms "upper", "lower", "inner" and "outer" are used to describe the relative positions of features of the exemplary embodiments shown in the figures.

[0070] The inventors have found that, in order to delay the occurrence of "pizza cut" failure of an impeller of a compressor, the fatigue resistance of the impeller can be improved, and the occurrence of "pizza cut" failure can be delayed, by introducing and / or increasing residual compressive stresses in the fillet region between the hub and the root of the blades of the impeller of the compressor.

[0071] In particular, residual compressive stresses can be introduced in the impeller of the compressor by means of a rolling process performed on the transition fillet between the hub and the root of the blades of the impeller. By means of such residual compressive stresses, the occurrence of the "pizza cut" failure mode can be inhibited. Such attempts to create residual compressive stresses by means of a rolling process to avoid the occurrence of fatigue failure have proven to be effective in the field of fasteners, for example, and it has been found that such treatment can significantly extend the service life of the rolled fasteners.

[0072] For the rolling machining of the impeller of the turbomachine, the rolling can be performed in a special device specifically designed and configured for rolling the transition fillet of the impeller, or in a CNC machining center. This will be further explained below.

[0073] Figure 1 A impeller 100 is schematically shown in a perspective view. The impeller 100 has a hub 101 and a plurality of blades 102. The area between the outer rim of the hub 101 to the root of the blades 102 is referred to as the transition fillet or transition fillet area.

[0074] Figure 1 A plurality of ellipses schematically show the areas in the wheel transition fillet of the impeller 100 that need to be rolled, also referred to as the areas to be rolled or target areas, which have reference numerals 110.

[0075] Figure 2 The impeller 100 is schematically shown in another perspective view.

[0076] Figure 3 and Figure 4 The impeller 100 is shown in an elevation view and a rear view, respectively. As can be seen in Figure 3 As can be seen in the figures, the areas to be rolled of the transition fillet of the hub of the impeller 100 are located in the range between 0.8 times the outer diameter OD to 1 times the outer diameter OD of the impeller.

[0077] The surface roughness of the rolled areas of the transition fillet of the impeller is superior to the surface roughness of the unrolled transition fillet. For example, the surface roughness of the rolled areas of the transition fillet of the impeller is superior to Ra 0.4.

[0078] The depth of the indentations in the rolled areas of the transition fillet of the impeller due to the rolling is 0.03 to 0.05 mm.

[0079] The following embodiments are explained with reference to Figure 5 , Figure 6 , Figure 7 The embodiments of the rolling process of the target areas of the transition fillet of the impeller 100 in the above-mentioned range in a dedicated rolling apparatus and in a CNC machining center are explained below.

[0080] Embodiment 1 Rolling the impeller in a dedicated rolling apparatus

[0081] As shown in the flowchart of Figure 5 The method of rolling a shaped impeller of a compressor in a dedicated rolling apparatus, which is specifically designed and constructed for rolling the transition fillet of the impeller of the compressor, comprises at least the following steps:

[0082] 1.1 Fixing the impeller of the compressor in the fixing means of the rolling apparatus;

[0083] 1.2 Adjusting the loading arm so that the loading arm is aligned with the areas to be rolled of the transition fillet of the impeller fixed between the outer rim of the hub and the root of the blades;

[0084] 1.3 The area of the fillet to be rolled is rolled by means of the rolling body arranged at the end of the loading arm, so that the indentation is produced in the rolled area by the rolling;

[0085] 1.4 The impeller whose indentation in the area of the fillet has been formed is removed.

[0086] If there are multiple impellers to be rolled, the next impeller to be rolled can be fixed into the fixing device of the rolling device, and the above steps 1.1-1.4 are repeated to complete the rolling of the fillet of the next impeller. By rolling the fillet between the hub and the blade root of the impeller of the compressor, the residual compressive stress is introduced in the rolled area, so that the fatigue resistance of the area of the fillet between the outer edge of the hub and the root of the blade can be improved by means of the introduced compressive stress, the occurrence of "pizza cut" failure is inhibited, and the service life of the impeller is prolonged.

[0087] It should be noted that the rolling in the above step 1.3 means that the pressure- applying rolling body at the end of the loading arm rolls at least once in the area of the fillet of the impeller to be rolled, and in order to produce the required indentation in the area of the fillet, and the indentation is completely formed, it is usually necessary for one rolling body to repeatedly roll 5 to 10 times at one fillet of the impeller.

[0088] The special rolling device also has a supporting device for the back disc of the rolled impeller, so as to provide a supporting force for the back disc. This can prevent the back disc from moving and deforming during the rolling of the rolling body on the fillet of the impeller, and further affecting the future use of the impeller.

[0089] Therefore, in the rolling device, the impeller can be fixed by means of the above-mentioned supporting device and fixing device, such as the mandrel for the inner hole of the hub of the impeller, to provide support during rolling of the impeller and avoid deformation, especially irreversible deformation, of other parts of the impeller due to the rolling process.

[0090] The rolling device usually has more than one pressure- applying and rolling component, which is composed of a loading arm and a rolling body arranged at the end of the loading arm. The rolling body contacts the surface of the machined impeller during rolling and rolls to leave an indentation and introduce a compressive stress. The rolling device has multiple such components so that each fillet of an impeller can be rolled in one machining step by means of one rolling device, improving the efficiency of the rolling process.

[0091] The above method and the specially designed rolling device are suitable for scenarios where a large number of impellers need to be machined, can be operated in a streamlined manner, realize synchronous rolling of all fillets of a single impeller, and shorten the single-piece machining cycle.

[0092] The rolling body of the rolling device is designed to contact the transition fillet of the impeller and to apply pressure to the impeller via the loading arm. The rolling body is, for example, a roller, a roller wheel or the like provided at the free end of the loading arm. The rolling body should have the same radius as the transition fillet of the hub of the impeller to be rolled.

[0093] Generally, the rolling device can include a plurality of sets of rolling bodies having different radius sizes so as to facilitate selection of a suitable rolling body to roll the transition fillet according to the different radius sizes of the transition fillet to be rolled of different sizes of impellers to ensure high efficiency of the rolling process.

[0094] Generally, the rolling device can also include rolling bodies having different hardness ranges made of different materials, the reason being that in order to ensure that rolling of the transition fillet of the impeller can cause deformation of the surface of the transition fillet of the impeller and introduce residual compressive stress, the hardness of the rolling body should be at least 20 HRC (Rockwell hardness) higher than the hardness of the material of which the impeller is made. For an impeller made of aluminum alloy, the hardness of the roller is desirably 35 to 40 HRC. For an impeller made of titanium alloy, the hardness of the roller is desirably 55 to 60 HRC. Having rolling bodies made of materials of different hardnesses enables selection of a suitable rolling body according to the hardness of the impeller to be rolled processed, ensuring the quality and efficiency of the rolling process.

[0095] The rolling device also has a driving source for driving the loading arm to move to complete positioning of the area to be rolled of the transition fillet of the impeller and to align the rolling body with the area to be rolled, and for driving the rolling body to apply sufficient load to the transition fillet of the hub of the impeller and to roll.

[0096] The rolling device also includes a cooling unit for cooling the impeller in rolling, particularly the area of the transition fillet being rolled, to avoid the occurrence of ablation or the introduction of cracks caused by high temperature in the rolled area, thereby causing damage to the impeller.

[0097] The surface roughness of the rolled transition fillet of the impeller is superior to that of the unrolled transition fillet.

[0098] The surface roughness of the rolled transition fillet of the impeller is superior to Ra 0.4.

[0099] The depth of the indentation produced in the rolled surface of the transition fillet of the impeller is 0.03 to 0.05 mm. The depth of the indentation can be achieved by adjusting the load applied via the rolling body.

[0100] The rolled area of the transition fillet of the impeller is between 0.8 times the outer diameter and 1 times the outer diameter of the impeller.

[0101] The speed of each rolling body along the surface of the impeller in each single rolling operation is determined by the output power of the driving source of the rolling device, the cooling power of the cooling unit of the rolling device, and other factors.

[0102] Embodiment 2 Integrated machining in CNC

[0103] As shown in the flowchart of Figure 6 In addition to the embodiment 1 explained above, the rolling of the area of the transition fillet of the impeller to produce the indentation also introduces the compressive residual stress in the process of producing the impeller from the blank, that is, when the impeller is produced by machining the blank in the CNC, the rolling machining of the transition fillet of the machined impeller blank can be directly performed in the CNC.

[0104] The machining method comprises at least the following steps:

[0105] 2.1 Fixing the bar or forged blank for manufacturing the impeller in the CNC;

[0106] 2.2 Machining the bar or forged blank to form the hub of the impeller and the transition fillet at the root of the hub to the blades of the impeller;

[0107] 2.3 Positioning an area of the transition fillet to be rolled;

[0108] 2.4 Aligning the rolling body of the CNC to the positioned area to be rolled;

[0109] 2.5 Rolling the area to be rolled to form the indentation in the rolled area;

[0110] 2.6 Moving the rolling body relative to the impeller manufactured from the bar or forged blank to position the area of the next transition fillet to be rolled;

[0111] 2.7 Repeating steps 2.4 to 2.6 until the rolling of all the fillets of the impeller is completed.

[0112] Such integrated machining method enables the on-line rolling in the CNC machining center, and the rolling process is included in the process of machining the impeller blank, which optimizes the machining process of the impeller. From the perspective of the overall machining process of the impeller, this realizes the efficient forming of the area of the transition fillet of the hub of the impeller with the compressive residual stress.

[0113] By introducing the compressive residual stress, the fatigue resistance of the area of the transition fillet of the hub of the impeller is improved, the service life of the impeller is prolonged, and the occurrence of the "pizza cut" failure is inhibited. This machining method is particularly advantageous for small-batch and high-precision impeller production.

[0114] The rolling body in steps 2.4 to 2.6 can also be replaced by a rolling head in the CNC.

[0115] The rolling body or the rolling head contacts the surface of the area of the transition fillet of the impeller to be machined when loaded and performs a rolling action, leaving an indentation in the rolled area of the impeller and introducing residual compressive stress. To ensure the effect of introducing residual compressive stress, the rolling body should have the same radius as the transition fillet of the hub of the impeller to be rolled. Therefore, in step 2.1 described above, when the blank is fixedly installed, the operator or the control unit of the CNC can determine the size of the impeller to be machined simultaneously, including the outer diameter of the impeller, the radius of the transition fillet of the impeller, and select the corresponding rolling body or rolling head according to the radius of the transition fillet to perform steps 2.5 and 2.6, so as to adapt to the size of the blank of the impeller and ensure the efficient performance of the rolling operation.

[0116] As shown in Figure 7 The method can further include steps 2.51 of monitoring the rolled surface and 2.52 of cooling the rolled surface after performing step 2.5 described above.

[0117] Step 2.51 is to monitor the surface of the rolled area of the transition fillet of the impeller by using, for example, the existing sensor unit in the CNC, to determine whether there is too high a temperature and whether there is a visual change in the surface, so as to prevent the rolling process from causing the temperature of the rolled area to rise, and in turn causing ablation or introducing cracks in the rolled area due to high temperature, and to issue an alarm if necessary.

[0118] Step 2.52 is to cool the rolled area by using, for example, the cooling unit in the CNC. With the help of the cooling unit, the rolled surface can be cooled after each rolling, the rolled surface can be cooled during rolling, or the rolled surface can be cooled after a plurality of rollings.

[0119] The CNC center should have a plurality of rolling bodies or rolling heads with different hardness. The hardness of the material of the selected rolling body or rolling head should be at least 20 HRC (Rockwell hardness) higher than the hardness of the material of the blank to be machined, so that the rolling and indentation in the area of the transition fillet of the blank in step 2.5 can be successfully performed. For aluminum alloy blanks, the hardness of the material of the rolling body or rolling head is ideally 35 to 40 HRC. For titanium alloy blanks, the hardness of the material of the rolling body or rolling head is ideally 55 to 60 HRC.

[0120] The surface roughness of the rolled surface of the transition fillet of the blank is better than that of the surface of the unrolled transition fillet. For example, the surface roughness of the rolled surface is better than Ra0.4.

[0121] The depth of the indentation formed in the rolled region of the transition fillet of the blank is 0.03 to 0.05 mm. The indentation depth can be controlled by the CNC control unit adjusting the load applied by the rolling body or rolling head. At the same time, it should also be ensured that the size of the applied load does not cause the CNC to alarm due to overload. If necessary, the desired indentation can be formed by increasing the number of rolling times. The rolled region is between 0.8 times the outer diameter to 1 times the outer diameter of the impeller formed by the final blank of the processed impeller, which can be positioned by the mandrel used to fix the blank of the impeller.

[0122] The speed at which the rolling body or rolling head rolls in the region of the transition fillet of the blank is determined by factors such as the output power of the CNC drive source, the cooling power of the cooling unit, etc., and is adjusted by the control unit.

[0123] It should be noted that the rolling in step 2.5 above refers to at least one rolling of the rolling body or rolling head in the region to be rolled of one transition fillet of the hub of the impeller positioned in 2.3 and is not limited to only one rolling. Generally, the rolling body or rolling head needs to roll 5 to 10 times in the region to be rolled of a single transition fillet of the impeller to obtain the desired indentation. Here, the size of the load applied each time can be the same and uniform, or it can be different. For example, the first or first few rollings are light pressure adjustments of the rolling body or rolling head, and only the last one or last few are relatively heavy pressure for complete indentation formation.

[0124] Embodiment 2 can be performed in an existing CNC through the rolling head, without the need to manufacture or purchase a dedicated rolling device, and the overall processing cost is lower. It is particularly advantageous for small batches and high-precision impellers, such as high-precision impellers used in the aerospace field. In the CNC integrated processing method, the process has high flexibility, and adjustments such as the position of the rolling body, the size of the load applied by the rolling body, etc. can be achieved by adjusting the processing program executed by the CNC through the control unit.

[0125] In the above, the two embodiments of rolling processing in a dedicated rolling device and integrated processing including rolling processing in a CNC are described respectively, and in particular, the number of times the rolling body rolls in the region of each transition fillet is described, but the present application is not limited thereto.

[0126] For example, depending on the material of the processed impeller, the future application scenario of the impeller, the depth of the indentation produced in the region of the transition fillet is not necessarily 0.03 to 0.05 mm, and can be larger or smaller than this range. For example, the roughness of the rolled region of the transition fillet can also be lower than Ra0.4 or higher than Ra0.4.

[0127] Accordingly, the number of times the rolling body or the rolling head rolls against the area of the same transition corner can be more than 10 times or less than 6 times, either in a dedicated rolling apparatus or in a CNC.

[0128] In the above, the hardness of the rolling body or the rolling head is explained in the case where the material of the impeller or the blank of the impeller is an aluminum alloy or a titanium alloy. However, the present application is not limited thereto, and the rolling body or the rolling head can be appropriately selected according to the hardness of other materials used to manufacture the impeller or the blank of the impeller, so as to ensure that the hardness thereof is at least 20 HRC higher than the hardness of the material used to manufacture the impeller or the blank of the impeller.

[0129] The present application can freely combine each embodiment, or appropriately deform, omit each embodiment, within the scope thereof.

Claims

1. An impeller for a compressor, the impeller comprising a back disk, a hub, and blades, wherein, The hub and the back plate are integrally constructed, and the hub is integrally connected to the root of the blade at its outer edge. There is a transition fillet between the outer edge of the hub and the root of the blade. The hub is characterized in that a rolled area is provided at each of the transition fillets, and in the rolled area, a dent is generated due to rolling.

2. The impeller as described in claim 1, characterized in that, The depth of the dent is 0.03 to 0.05 mm.

3. The impeller as described in claim 1, characterized in that, The rolled area is located between 0.8 times and 1 times the outer diameter of the impeller.

4. The impeller as described in claim 1, characterized in that, The rolled area is configured such that its surface roughness is better than that of the unrolled area at the root of the blade.

5. The impeller as described in claim 4, characterized in that, The surface roughness of the rolled area is better than Ra0.

4.

6. A method for machining a compressor impeller, characterized in that... Includes the following steps: The impeller of the compressor is fixed by means of a clamp, wherein the hub of the impeller is integrally connected to the root of the blades of the impeller at the outer edge, and there is a transition fillet between the outer edge of the hub and the root of the blades; Position the rolling elements to align them with the target area of ​​the impeller's transition fillet; The target area is loaded and rolled at least once using a rolling element, thereby creating a dent in the rolled area.

7. A method for manufacturing an impeller for a compressor, characterized in that, Includes the following steps: The compressor impeller blank is fixed in place using a clamp. The blank is processed to form the hub and blades of the impeller, such that the hub is integrally connected to the root of the blade at the outer edge, and there is a transition fillet between the outer edge of the hub and the root of the blade; Position the rolling elements to align them with the target area of ​​the impeller's transition fillet; The target area is loaded with a rolling element to perform at least one rolling pass, thereby creating a dent in the rolled area.

8. The method as described in claim 6 or 7, characterized in that, The target area of ​​the transition fillet is rolled 5 to 10 times using the rolling element.

9. The method as described in claim 6 or 7, characterized in that, The method further includes a step of cooling the rolled area after loading the target area for at least one rolling.

10. The method as described in claim 6 or 7, characterized in that, The depth of the dent is 0.03 to 0.05 mm.

11. The method as described in claim 6 or 7, characterized in that, The rolled area is located between 0.8 times and 1 times the outer diameter of the impeller.

12. The method as described in claim 7, characterized in that, The method further includes, after rolling the target area of ​​a transition fillet, repositioning the rolling element relative to the blank to align it with the area to be rolled for the next transition fillet.

13. A rolling device for a compressor impeller, comprising: A mounting device for securing the compressor impeller. Multiple rolling elements for rolling. A control unit configured to process an impeller fixed at the fixing device according to the method of claim 6, so as to load and roll the impeller at the target area of ​​each transition fillet of the impeller by means of the plurality of rolling elements, thereby creating indentations in the rolled area.

14. The rolling mill as described in claim 13, characterized in that, The depth of the dent is 0.03 to 0.05 mm.

15. The rolling mill as described in claim 13, characterized in that, The rolled area is located between 0.8 times and 1 times the outer diameter of the impeller.

16. The rolling mill equipment according to any one of claims 13 to 15, characterized in that, The radius of the rolling element is determined to be the same as the radius of the transition fillet.

17. The rolling mill equipment according to any one of claims 13 to 15, characterized in that, The rolling equipment also includes a cooling device for cooling the rolled surface of the impeller.

18. The rolling mill equipment according to any one of claims 13 to 15, characterized in that, The hardness of the rolling element is at least 20 HRC higher than that of the impeller material.

19. The rolling mill as described in claim 18, characterized in that, For impellers made of aluminum alloy, the hardness of the rolling elements is 35-40 HRC; or for impellers made of titanium alloy, the rolling elements are selected such that the hardness of the rolling elements is 55-60 HRC.

20. The rolling mill equipment according to any one of claims 13 to 15, characterized in that, The rolling equipment also includes a support device for supporting the back plate of the impeller.

21. The rolling mill equipment according to any one of claims 13 to 15, characterized in that, The rolling device also includes multiple loading arms, with the rolling elements respectively disposed at the free ends of the loading arms. The loading arms are configured to drive the rolling elements to move relative to the impeller.

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