Method for detecting change in transfer molding process of motor rotor core stack

Abstract

The present disclosure provides a method for detecting a change in a transfer molding process of a motor rotor core stack. A method for detecting a change in a rotor core stack includes: measuring a jig press position of a jig press and a plunger position of a plunger; determining a nominal position of the jig press; calculating a height offset of the rotor core stack; calculating a normalized position of the plunger by adding the plunger position and the height offset of the rotor core stack; and analyzing the standardized plunger position to detect a change within the rotor core stack.

Description

Technical Field

[0001] The present disclosure relates to an electric motor. More specifically, the present disclosure relates to detecting variations in a transfer molding process of a rotor core stack of an electric traction motor. Background Art

[0002] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0003] Electric traction motors are used to provide propulsion in electric vehicles and hybrid electric vehicles. Electric traction motors conventionally include a stationary component or stator and a rotating component or rotor. The rotor includes a rotor core stack and magnets inserted into cavities of the rotor core stack. The magnets are sealed in the rotor core stack with a thermosetting resin during a resin transfer molding press process.

[0004] During the resin transfer molding process, a press clamps the rotor core stack between a mandrel and a runner plate via the bottom of the press and the top of the press. Raw resin is placed in a reservoir located above the runner plate and heated to a liquid state. A plunger presses the liquid resin through the runner plate to fill the cavities around the magnets in the rotor core stack. Once the resin cures into a solid state, the magnets are permanently sealed within the rotor core stack.

[0005] A variety of scenarios can occur during the transfer molding process that can result in defective rotor core stacks. Some scenarios may include resin leakage, missing magnets, or incomplete filling. These scenarios can cause variations in the amount of residual resin remaining in the reservoir.

[0006] The volume of the rotor core stack cavities can also vary between each rotor core stack. Variations in the volume of the rotor core stack cavities can result in significant variations in the volume of the residual resin. The normal variations in the volume of the residual resin due to variations in the volume of the rotor core stack cavities can be greater than the abnormal variations in the volume of the residual resin due to process problems.

[0007] The present disclosure addresses challenges related to molding process variations in an electric motor rotor stack. Summary of the Invention

[0008] This section provides an overall overview of the present disclosure and is not a full disclosure of its entire scope or all of its features.

[0009] In one form of the present disclosure, a method for detecting changes in a rotor core stack includes: measuring a fixture press position of a fixture press and a plunger position of a plunger; determining a nominal position of the fixture press; calculating, via a controller, a height offset of the rotor core stack; calculating, via the controller, a normalized position of the plunger by adding the plunger position and the height offset of the rotor core stack; and analyzing, via the controller, the normalized plunger position to detect changes within the rotor core stack, and in response to analyzing the normalized plunger position to detect changes within the rotor core stack, accepting or rejecting the rotor core stack for production based on the detected changes.

[0010] In variations of the method that may be implemented individually or in combination: calculating the height offset of the rotor core stack further includes calculating a difference between the fixture press position and the nominal position of the fixture press to determine a position difference; calculating the height offset of the rotor core stack further includes normalizing a plunger cross-sectional area of a bore of the plunger by a cross-sectional area of the rotor core stack to determine a normalized area; calculating the height offset of the rotor core stack further includes multiplying the normalized area and the position difference; the cross-sectional area of the rotor core stack is a cross-sectional area of a plurality of cavities of the rotor core stack; analyzing the normalized plunger position further includes determining whether the plunger position and the fixture press position are between an upper limit and a lower limit; analyzing the normalized plunger position further includes accepting the rotor core stack where the plunger position and the fixture press position are between the upper limit and the lower limit; analyzing the normalized plunger position further includes rejecting the rotor core stack where the plunger position and the fixture press position are not between the upper limit and the lower limit; the fixture press position of the fixture press is a distance between a top surface of the fixture press and a top surface of a runner plate located on a top surface of the rotor core stack; and the plunger position is a distance between a bottom surface of the plunger and a top surface of a runner plate located on a top surface of the rotor core stack.

[0011] In another form, a method for detecting changes in a rotor core stack includes: measuring the die press position of a die press and the plunger position of a plunger; determining a nominal position of the die press; calculating, via a controller, a difference between the die press position and the nominal position of the die press to determine a position difference; normalizing, via the controller, a plunger cross-sectional area of a bore of the plunger by a cross-sectional area of a plurality of cavities of the rotor core stack to determine a normalized area; calculating, via the controller, a height offset of the rotor core stack by multiplying the normalized area and the position difference; calculating, via the controller, a normalized position of the plunger by adding the plunger position and the height offset of the rotor core stack; and analyzing, via the controller, the normalized plunger position to detect changes within the rotor core stack, and in response to analyzing the normalized plunger position to detect changes within the rotor core stack, accepting or rejecting the rotor core stack for production based on the detected changes.

[0012] In a variation of the method that can be implemented individually or in combination: analyzing the normalized plunger position further includes determining whether the normalized plunger position and the die press position are between an upper limit and a lower limit; analyzing the normalized plunger position further includes accepting the rotor core stack in which the plunger position and the die press position are between the upper limit and the lower limit; analyzing the normalized plunger position further includes rejecting the rotor core stack in which the plunger position and the die press position are not between the upper limit and the lower limit; the die press position of the die press is a distance between a top surface of the die press and a top surface of a runner plate located on a top surface of the rotor core stack; and the plunger position is a distance between a bottom surface of the plunger and a top surface of a runner plate located on a top surface of the rotor core stack.

[0013] In yet another form of the present disclosure, a system for detecting changes in a rotor core stack includes: a rotor core stack; a die press disposed below a bottom surface of the rotor core stack; a runner plate disposed above a top surface of the rotor core stack; a plunger disposed above the runner plate; at least one sensor for determining the die press position of the die press and the plunger position of the plunger; and a controller for calculating a height offset of the rotor core stack, determining a normalized position of the plunger based on the height offset of the rotor core stack and the plunger position, and analyzing the normalized plunger position to detect changes in the rotor core stack.

[0014] In a variation of the system that can be implemented individually or in combination: the controller determines whether the normalized plunger position and the clamp press position are between an upper limit and a lower limit; the clamp press position of the clamp press is the distance between the top surface of the clamp press and the top surface of the runner plate; and the plunger position is the distance between the bottom surface of the plunger and the top surface of the runner plate.

[0015] Based on the description provided herein, additional applicable fields will become apparent. It should be understood that the description and specific examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] To better understand the present disclosure, various forms of the present disclosure will now be described by way of example with reference to the accompanying drawings, in which:

[0017] Figure 1 A schematic view of a rotor core stack in a transfer molding press according to the present disclosure is depicted;

[0018] Figure 2 Depicts a rotor core of a rotor core stack according to Figure 1 ;

[0019] Figure 3 A method for detecting changes in a rotor core stack according to the present disclosure is depicted;

[0020] Figure 4 Depicts a method for calculating the height offset of a core stack of a rotor core according to Figure 3 ;

[0021] Figure 5 An example data set of a rotor core stack according to the present disclosure is depicted; and

[0022] Figure 6 Depicts a method for analyzing the normalized plunger position to detect changes in a rotor core according to Figure 3 ;

[0023] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way. DETAILED DESCRIPTION

[0024] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate the same or corresponding parts and features.

[0025] Refer to Figure 1 and Figure 2, the transfer molding system 100 includes a rotor core stack 102. The rotor core stack 102 includes a series of rotor cores 200 stacked one on top of the other along the vertical direction. The rotor core stack 102 also includes a plurality of cavities 201 disposed within each of the rotor cores 200 of the rotor core stack 102. The cavities 201 include a plurality of magnet slots 202 in which a plurality of magnets 205 are disposed. In one form, the cavities 201 of the rotor core stack 102 may also include structural holes 204.

[0026] The transfer molding system 100 also includes a runner plate 104, a mandrel 106, a clamp press 108, and a support member 110. The rotor core stack 102 is disposed between the runner plate 104 and the mandrel 106. The mandrel 106 is disposed on the top surface of the clamp press 108, and the rotor core stack 102 is disposed on the top surface of the mandrel 106. Then, the runner plate is disposed above the rotor core stack 102 and below the support member 110. During the transfer molding pressing process, the clamp press 108 moves toward the support member 110 to clamp the rotor core stack 102 between the runner plate 104 and the mandrel 106 with a predetermined force.

[0027] The transfer molding system 100 also includes a plunger 114 disposed within a hole of the support member 110. The hole and the runner plate 104 define a reservoir 112. A solid polymer is placed within the reservoir 112 and heated until it reaches a liquid state and becomes a liquid polymer 116. In one form, the liquid polymer 116 is an epoxy resin.

[0028] During the transfer molding pressing process, the plunger 114 presses the liquid polymer 116 through the holes in the runner plate 104 to fill the cavities within the rotor core stack 102. The liquid polymer 116 fills the space between the plurality of magnet slots 202 and the plurality of magnets 205. Once the liquid polymer 116 cures and reaches a solid state, the plurality of magnets 205 are permanently held within the plurality of magnet slots 202. In one form, the cavities may also include structural holes 204, which are filled with the liquid polymer 116 to provide structural support for the rotor core stack 102 after the liquid polymer 116 cures.

[0029] The transfer molding system 100 also includes at least one sensor 120 and a controller 122. The at least one sensor 120 determines a clamp press position 126 of the clamp press 108 and a plunger position 124 of the plunger 114. The clamp press position 126 provides the position of the clamp press relative to the remainder of the transfer molding system 100. In one form, the clamp press position 126 is the distance between the top surface of the clamp press 108 and the top surface of the runner plate 104. In various forms, the clamp press position 126 is the case when the clamp press 108 is in a final position that clamps the mandrel 106, the rotor core stack 102, and the runner plate 104 between the clamp press 108 and the support member 110 with a predetermined force. The plunger position 124 provides the position of the plunger relative to the remainder of the transfer molding system 100. In a particular form, the plunger position 124 is the distance between the bottom surface of the plunger 114 and the top surface of the runner plate 104. In one form, the plunger position 124 is the case when the plunger 114 is in a final position and has completed extruding the liquid polymer 116 into the rotor core stack 102. The sensor 120 transmits the clamp press position 126 and the plunger position 124 to the controller 122.

[0030] Reference Figure 3 , a method 300 for detecting changes in the rotor core stack 102 is shown. In step 302, the at least one sensor 120 measures the clamp press position 126 and the plunger position 124. In one form, the clamp press position 126 is the final position of the clamp press 108. The final position of the clamp press 108 is the case when the clamp press 108 clamps the mandrel 106, the rotor core stack 102, and the runner plate 104 between the clamp press 108 and the support member 110 with a predetermined force. In various forms, the plunger position 124 is the final position of the plunger 114. The final position of the plunger 114 is the case when the plunger 114 is in a final position and has completed extruding the liquid polymer 116 into the rotor core stack 102. In a particular form, the final position of the plunger 114 is variable and is determined based on the transfer molding process of each rotor core stack 102. During the final stage of the transfer molding process, the plunger 114 extrudes the liquid polymer 116 through a hole in the runner plate 104 at a predetermined pressure for a first predetermined duration. Then, the plunger 114 stops and holds for a second predetermined duration while the liquid polymer 116 cures into a solid. The position at which the plunger 114 stops is the final position of the plunger 114. In a particular form, the controller 122 records the clamp press position 126 and the plunger position 124.

[0031] In step 304, the controller 122 determines the nominal position of the fixture press 108. In one form, the nominal position of the fixture press is determined by adding the heights of the rotor core stack 102, the runner plate 104, and the mandrel 106. In another form, the nominal fixture press position 126a can be the average or mean of multiple final positions from a sample data set of the previous rotor core stack 102 transfer molding system 100 of the fixture press 108. In one form, the final fixture press position 126c is the nominal fixture press position 126a. In other forms, the final fixture press position 126c can vary from the nominal fixture press position 126a by a tolerance within a predetermined tolerance range. Step 304 can be completed before, after, or simultaneously with step 302. In step 306, the controller 122 calculates the height offset of the rotor core stack 102.

[0032] Reference Figure 4 , more details of step 306 are provided. In step 402, the position difference is determined by subtracting the nominal position of the fixture press 108 from the fixture press position 126. Then, in step 404, the controller determines the normalized area. The normalized area is the cross-sectional area of the rotor core stack 102 divided by the cross-sectional area of the hole of the plunger 114. In one form, the cross-sectional area of the rotor core stack 102 is the total cross-sectional area of the cavities 201 of the rotor core stack 102. In one form, the total cross-sectional area of the cavities 201 includes at least one of the total cross-sectional area of the plurality of magnet slots 202 and the total cross-sectional area of the structural holes 204. In step 406, the normalized area of step 404 is multiplied by the position difference of step 402 to provide the height offset of the rotor core stack 102. The height offset is determined by the following equation:

[0033]

[0034] where X2 is the fixture press position 126, is the nominal fixture press position, A1 is the cross-sectional area of the hole of the plunger 114, and A2 is the cross-sectional area of the rotor core stack 102.

[0035] Return reference Figure 3 , in step 308, the controller 122 calculates the normalized plunger position of the plunger. The normalized plunger position 124b is the sum of the nominal plunger position 124a and the height offset calculated in step 306. The normalized plunger position 124b depends on the geometry of the rotor core stack 102 because it takes into account the height and cross-sectional area of the cavities 201 of the rotor core stack 102.

[0036] Then, in step 310, the controller 122 analyzes the normalized plunger position to detect changes in the rotor core stack 102. Common sources of changes in the rotor core stack 102 include changes in the following volumes: the volume of the liquid polymer 116, the volume of the cavities 201 in the rotor core stack 102, the volume of the magnets 205, and the volume of the holes in the flow channel plate 104. For example, if the rotor core stack 102 is missing a magnet 205, the volume of the total area of the cavities 201 will increase, and the amount of liquid polymer 116 required to fill the cavities 201 of the rotor core stack 102 will increase. Other sources of changes in the rotor core stack 102 include resin extrusion between the rotor cores 200 or the flow channel plate 104, and incomplete transfer of the liquid polymer 116.

[0037] Further reference Figure 5 and Figure 6 FIG. 500 aggregates data 502 of multiple rotor core stacks 102 in the transfer molding system 100 and correlates the plunger position 124 and the clamp press position 126 of the data 502. In one form, the data 502 includes a predetermined data set of the rotor core stack 102 from a previous transfer molding system 100. In one variant, the data 502 can be random sample data from a predetermined data set. In one form, the predetermined data set can consist of data of the rotor core stack 102 from a previous transfer molding system 100 that has previously passed a quality control process. In another form, the data 502 can be a compilation of the rotor core stack 102 to be analyzed for changes.

[0038] The normalized plunger position is calculated for each point of the data 502. The aggregation of the normalized plunger positions forms a line 504. In one form, the line 504 is the best fit line through the data 502, which expresses the relationship between the plunger positions 124 of the multiple data 502 and the clamp press position 126. In one form, the line 504 is linear. The line 504 depends on the data 502 and the normalized plunger position. The lower limit 506 and the upper limit 508 are determined based on the line 504. In one form, the lower limit 506 and the upper limit 508 are within one to five standard deviations of the line 504. In another form, the upper limit 508 and the lower limit 506 are within + / - three standard deviations of the line 504, respectively. The upper limit 508 is three standard deviations higher than the line 504, and the lower limit 506 is three standard deviations smaller than the line 504.

[0039] In step 602, the controller determines whether the plunger position 124 and the clamp press position 126 are between an upper limit 508 and a lower limit 506. If both the plunger position 124 and the clamp press position 126 are between the upper limit 508 and the lower limit 506, then in step 604 the corresponding rotor core stack 102 is accepted for production. An example of an accepted rotor core stack 102 is represented by an accepted data point 514. If at least one of the plunger position 124 and the clamp press position 126 is not between the upper limit 508 and the lower limit 506, then in step 606 the corresponding rotor core stack 102 is rejected for production. An example of a rotor core stack 102 rejected because liquid polymer 116 was extruded between rotor cores 200 or runner plates 104 of the rotor core stack 102 is represented by a rejected data point 510. An example of a rotor core stack 102 rejected because of incomplete transfer of liquid polymer 116 is represented by a rejected data point 512. When determining acceptable variations of the rotor core stack 102, method 300 considers the height of the rotor core stack 102 and variations in the area of the cavities 201 of the rotor core stack 102.

[0040] Unless expressly indicated otherwise herein, all numerical values indicating mechanical / thermal properties, percentages of composition, dimensions, and / or tolerances or other characteristics should be understood as being modified by the word "about" or "approximately" when describing the scope of the present disclosure. This modification is desirable for various reasons including: industrial practice; material, manufacturing, and assembly tolerances; and testing capabilities.

[0041] As used herein, the phrase "at least one of A, B, and C" should be construed to represent the logic (A or B or C) using non-exclusive logic "or" and should not be construed to mean "at least one of A, at least one of B, and at least one of C".

[0042] In the present application, the terms "controller" and / or "module" may refer to, be part of, or include the following: application specific integrated circuit (ASIC); digital, analog, or mixed analog / digital discrete circuits; digital, analog, or mixed analog / digital integrated circuits; combinational logic circuits; field programmable gate arrays (FPGA); processor circuits (shared, dedicated, or group) that execute code; memory circuits (shared, dedicated, or group) that store code executed by the processor circuits; other suitable hardware components that provide the described functionality (e.g., operational amplifier circuit integrators as part of a heat flux data module); or a combination of some or all of the above, such as in a system-on-chip.

[0043] The term memory is a subset of the term computer-readable medium. As used herein, the term computer-readable medium does not cover transitory electrical or electromagnetic signals propagated through a medium (such as on a carrier wave); thus, the term computer-readable medium can be considered tangible and non-transitory. Non-limiting examples of non-transitory tangible computer-readable media are non-volatile memory circuits (such as flash memory circuits, erasable programmable read-only memory circuits, or mask read-only circuits), volatile memory circuits (such as static random access memory circuits or dynamic random access memory circuits), magnetic storage media (such as analog or digital magnetic tape or hard disk drives), and optical storage media (such as CDs, DVDs, or Blu-ray discs).

[0044] The devices and methods described in this application can be implemented, in part or in whole, by a special-purpose computer created by configuring a general-purpose computer to execute one or more specific functions embodied in a computer program. Functional blocks, flowchart components, and other elements described above serve as software specifications that can be translated into a computer program by the routine work of a technician or programmer.

[0045] The description of the present disclosure is merely exemplary in nature and, thus, variations that do not depart from the substance of the present disclosure are intended to be within the scope of the present disclosure. Such variations should not be regarded as departing from the spirit and scope of the present disclosure.

[0046] According to the present invention, a method for detecting a change in a rotor core stack includes: measuring a die press position of a die press and a plunger position of a plunger; determining a nominal position of the die press; calculating, via a controller, a difference between the die press position and the nominal position of the die press to determine a position difference; normalizing, via the controller, a plunger cross-sectional area of a bore of the plunger by a cross-sectional area of a plurality of cavities of the rotor core stack to determine a normalized area; calculating, via the controller, a height offset of the rotor core stack by multiplying the normalized area and the position difference; calculating, via the controller, a normalized position of the plunger by adding the plunger position and the height offset of the rotor core stack; and analyzing, via the controller, the normalized plunger position to detect a change within the rotor core stack, and in response to analyzing the normalized plunger position to detect a change within the rotor core stack, accepting or rejecting the rotor core stack for production based on the detected change.

[0047] In one aspect of the present invention, analyzing the normalized plunger position further includes determining whether the normalized plunger position and the die press position are between an upper limit and a lower limit.

[0048] In one aspect of the present invention, analyzing the standardized plunger position further includes accepting the rotor core stack where the plunger position and the jig press position are between the upper limit and the lower limit.

[0049] In one aspect of the present invention, analyzing the standardized plunger position further includes rejecting the rotor core stack where the plunger position and the jig press position are not between the upper limit and the lower limit.

[0050] In one aspect of the present invention, the jig press position of the jig press is the distance between the top surface of the jig press and the top surface of the runner plate located on the top surface of the rotor core stack.

[0051] In one aspect of the present invention, the plunger position is the distance between the bottom surface of the plunger and the top surface of the runner plate located on the top surface of the rotor core stack.

Claims

1. A method for detecting changes in a rotor core stack, the method comprising: measuring the clamp press position of the clamp press and the plunger position of the plunger; determining a nominal position of the fixture press; calculating, via a controller, a height offset of the rotor core stack; calculating, via the controller, a normalized position of the plunger by adding the plunger position and the height offset of the rotor core stack; as well as The standardized plunger positions are analyzed via the controller to detect variations within the rotor core stack, and in response to analyzing the standardized plunger positions to detect variations within the rotor core stack, the rotor core stack is accepted or rejected for production based on the detected variations. 2 . The method of claim 1 , wherein calculating the height offset of the rotor core stack further comprises calculating a difference between the jig press position and the nominal position of the jig press to determine a position difference. 3 . The method of claim 2 , wherein calculating the height offset of the rotor core stack further comprises normalizing a plunger cross-sectional area of ​​a bore of the plunger with a cross-sectional area of ​​the rotor core stack to determine a normalized area. 4 . The method of claim 3 , wherein calculating the height offset of the rotor core stack further comprises multiplying the normalized area and the position difference. 5 . The method of claim 3 , wherein the cross-sectional area of ​​the rotor core stack is a cross-sectional area of ​​a plurality of cavities of the rotor core stack.

6. The method of claim 1, wherein analyzing the normalized plunger position further comprises determining whether the plunger position and the clamp press position are between upper and lower limits. 7 . The method of claim 6 , wherein analyzing the standardized plunger position further comprises accepting the rotor core stack with the plunger position and the clamp press position between the upper and lower limits. 8 . The method of claim 6 , wherein analyzing the standardized plunger position further comprises rejecting the rotor core stacks where the plunger position and the clamp press position are not between the upper limit and the lower limit.

9. The method of claim 1, wherein the jig press position of the jig press is a distance between a top surface of the jig press and a top surface of a runner plate located on a top surface of the rotor core stack.

10. The method of claim 1, wherein the plunger position is a distance between a bottom surface of the plunger and a top surface of a flow channel plate located on a top surface of the rotor core stack.

11. A system for detecting changes in a rotor core stack, the system comprising: Rotor core stacking; a jig press disposed below a bottom surface of the rotor core stack; a flow channel plate disposed above a top surface of the rotor core stack; A plunger, the plunger being arranged above the flow channel plate; at least one sensor for determining a clamp press position of the clamp press and a plunger position of the plunger; as well as A controller is configured to calculate a height offset of the rotor core stack, determine a normalized position of the plunger based on the height offset of the rotor core stack and the plunger position, and analyze the normalized plunger position to detect a change in the rotor core stack.

12. The system of claim 11, wherein the controller determines whether the normalized plunger position and the clamp press position are between upper and lower limits.

13. The system of claim 11, wherein the jig press position of the jig press is a distance between a top surface of the jig press and a top surface of the manifold plate.

14. The system of claim 11, wherein the plunger position is a distance between a bottom surface of the plunger and a top surface of the flow channel plate.

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