Permanent magnet aging device and permanent magnet aging system of electric power steering system
By using an alternating magnetic field control circuit system to age permanent magnets, the problem of low aging efficiency in existing technologies is solved, achieving efficient aging and precise control of permanent magnets, and improving the stability and reliability of permanent magnets.
Patent Information
- Application Number
- CN202423184906.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-23
- Publication Date
- 2025-12-19
- Estimated Expiration
- 2034-12-23
AI Technical Summary
Existing methods for aging permanent magnets are inefficient, time-consuming, and difficult to control in terms of aging progress and precision, resulting in insufficient stability and reliability of permanent magnets during use.
The permanent magnet aging device utilizes an alternating magnetic field control circuit system to generate an alternating magnetic field through an excitation coil. Combined with magnetic field strength and direction control circuits, it achieves efficient aging of permanent magnets and precise control over the degree and accuracy of aging.
It improves the stability and reliability of permanent magnets, shortens the initial failure period of the life cycle, enhances the stability and reliability of permanent magnet application products, and facilitates life cycle assessment.
Smart Images
Figure CN223692517U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to permanent magnet technical field, specifically, relate to permanent magnet aging device and electric power steering system's permanent magnet aging system. BACKGROUND
[0002] The corresponding relation of failure rate and operation time of electronic and electrical components in the whole life cycle follows the bathtub curve (failure rate curve), and the permanent magnet used in the angle sensor of the electric power steering system and other industrial products is not exceptional. Figure 1 As shown in the figure, with the passage of time, the failure rate curve 100 of the permanent magnet shows three stages: the initial failure period 110, the sporadic failure period 120 and the wear failure period 130, wherein the failure rate of the sporadic failure period 120 is low, the magnetic property of the permanent magnet is stable, and the effective life cycle 100' of the permanent magnet corresponds to the sporadic failure period 120.
[0003] Therefore, one of the methods to improve the reliability of the permanent magnet is to age the permanent magnet before use, so that the permanent magnet can experience the initial failure period 110 in advance, thereby directly entering the sporadic failure period 120 with low failure rate after use.
[0004] The current permanent magnet aging method is to place the permanent magnet in a high-temperature environment to naturally degrade its magnetic property to achieve the aging purpose. The efficiency of natural aging in a high-temperature environment is low, the time cost is high, and the degree and precision of natural aging in a high-temperature environment are not easy to control, and the aging progress is difficult to control.
[0005] It should be noted that the information disclosed in the above background section is only used to strengthen the understanding of the background of the utility model, and therefore can include information that does not constitute prior art known to those skilled in the art. CONTENT OF THE UTILITY MODEL
[0006] Therefore, the utility model provides a permanent magnet aging device and a permanent magnet aging system for an electric power steering system, which utilizes the principle that the aging speed of the permanent magnet is accelerated in an alternating magnetic field, realizes efficient aging of the permanent magnet, and facilitates control of the degree and precision of aging, thereby realizing precise control of the aging progress of the permanent magnet.
[0007] According to one aspect of the utility model, provide a kind of permanent magnet aging device, comprising: load circuit, including excitation coil and sampling element in series;Magnetic field intensity control circuit, including negative feedback circuit, the output of the negative feedback circuit is connected in the load circuit, and the sampling element is connected the reverse input end of the negative feedback circuit, and the magnetic field intensity control circuit is used to control the intensity of the environmental magnetic field generated by the excitation coil;Magnetic field direction control circuit, including relay, the relay has two switches and two pairs of contacts, wherein each switch is matched with a pair of contacts, the two switches are connected in series in the load circuit, and each pair of the contact is respectively connected to the two ends of the excitation coil, and the magnetic field direction control circuit is used to control the direction of the environmental magnetic field.
[0008] The excitation coil generates a magnetic field with corresponding intensity under the drive of current, the intensity of the magnetic field is in proportional relationship with the current flowing through the excitation coil, and the direction of the magnetic field is controllable and determined by the direction of the current flowing through the excitation coil. By placing the permanent magnet in the magnetic field range of the excitation coil and controlling the excitation coil to generate an alternating magnetic field by using the magnetic field intensity control circuit and the magnetic field direction control circuit, the required magnetic field environment is provided for the aging of the permanent magnet. The magnetic field intensity control circuit includes a negative feedback circuit, the load current flowing through the excitation coil is fed back through the sampling element connected in series with the excitation coil, the current of the load circuit in which the excitation coil is located is stabilized through the adjustment of the negative feedback circuit, so as to control the intensity of the environmental magnetic field generated by the excitation coil; when the input of the negative feedback circuit is changed, the intensity of the environmental magnetic field generated by the excitation coil changes accordingly. The magnetic field direction control circuit includes a relay, the two switches of the relay are connected in series in the load circuit and each pair of contacts is respectively connected to the two ends of the excitation coil, the direction of the environmental magnetic field generated by the excitation coil is changed by switching the connection state between the switches and the contacts of the relay, and then the direction of the environmental magnetic field generated by the excitation coil is changed. In this way, the excitation coil generates an alternating magnetic field by controlling the excitation coil through the magnetic field intensity control circuit and the magnetic field direction control circuit, so that the magnetic field of the permanent magnet is accelerated to degrade to a stable state, and the permanent magnet is efficiently aged; and the intensity and direction of the environmental magnetic field generated by the excitation coil can be accurately controlled through the magnetic field intensity control circuit and the magnetic field direction control circuit, so as to control the aging degree and precision of the permanent magnet, and accurately control the aging progress of the permanent magnet.
[0009] The permanent magnet aging device of the utility model is used to place the permanent magnet in the alternating magnetic field for aging test before the permanent magnet is installed / used, so that the permanent magnet quickly experiences the initial failure period, so as to directly enter the occasional failure period with low failure rate after being put into use, greatly improves the stability and reliability of the permanent magnet after being put into use, and then improves the stability and reliability of the industrial product to which the permanent magnet is applied, and also facilitates the evaluation of the service life of the permanent magnet.
[0010] In some embodiments, when the first control signal inputted by the in-phase input end of the negative feedback circuit changes, the strength of the environmental magnetic field changes; when the connection state of the switching contact of the relay changes, the direction of the environmental magnetic field changes; as the permanent magnet aging device operates: the value of the first control signal decreases, and / or the transformation frequency of the connection state decreases.
[0011] The aging speed of the permanent magnet is related to the strength and polarity transformation frequency of the environmental magnetic field. The greater the strength of the environmental magnetic field and the higher the polarity transformation frequency, the faster the aging speed of the permanent magnet. As the permanent magnet aging test proceeds, the strength of the environmental magnetic field is reduced by decreasing the value of the first control signal of the negative feedback circuit, and / or the polarity transformation frequency of the environmental magnetic field is reduced by decreasing the transformation frequency of the connection state of the relay, so that the aging progress of the permanent magnet is slowed down, so as to accurately control the degree and precision of the aging.
[0012] In some embodiments, as the permanent magnet aging device operates: when the magnetic field strength of any magnetic pole of the permanent magnet subjected to the environmental magnetic field reaches a preset threshold value, the value of the control signal decreases; when the magnetic field strength of both magnetic poles of the permanent magnet reaches the preset threshold value, the transformation frequency of the connection state decreases; when the magnetic field strength of any magnetic pole of the permanent magnet reaches a critical threshold value, the permanent magnet aging device stops operating; wherein the critical threshold value is the magnetic field strength corresponding to the critical value of the failure rate change of the permanent magnet, and the preset threshold value is greater than the critical threshold value.
[0013] During the aging test, the magnetic field strengths of the N and S poles of the permanent magnet are detected at a certain frequency. When one of the magnetic field strengths of the N and S poles of the permanent magnet reaches a preset threshold value, the value of the control signal is decreased to reduce the current flowing through the excitation coil, thereby correspondingly reducing the strength of the environmental magnetic field in which the permanent magnet is located. At this time, the detection frequency of the magnetic field strength of the permanent magnet itself can be increased simultaneously to improve the control accuracy of the aging progress. When the magnetic field strengths of the N and S poles of the permanent magnet both reach the preset threshold value, the transformation frequency of the connection state of the relay is reduced to reduce the direction transformation frequency of the current of the excitation coil, and further reduce the direction transformation frequency of the environmental magnetic field in which the permanent magnet is located. At the same time, the test frequency of the magnetic field strength of the permanent magnet itself can be increased again to further improve the control accuracy of the aging progress. When one of the magnetic field strengths of the N and S poles of the permanent magnet reaches the critical point position of the high failure rate and the low failure rate, the aging test stops. At this time, the service life of the permanent magnet is at the critical point position of the high failure rate and the low failure rate, i.e., at the critical point position of the initial failure period and the occasional failure period. At this time, the permanent magnet is put into use, and the operating failure rate is at the smooth position of the low point of the failure period curve.
[0014] In some embodiments, the negative feedback circuit comprises: an operational amplifier, a non-inverting input terminal of the operational amplifier is connected to the first signal input terminal; a first transistor, which is connected in series between the excitation coil and the sampling element, an output terminal of the operational amplifier is connected to a control terminal of the first transistor, and a node of the series connection of the first transistor and the sampling element is connected to an inverting input terminal of the operational amplifier.
[0015] The sampling element feeds back the current of the excitation coil in real time. When the current of the load loop becomes larger, the voltage of the inverting input terminal of the operational amplifier becomes higher, the difference between the inverting input terminal and the non-inverting input terminal becomes smaller, the output differential voltage of the operational amplifier becomes smaller, the base current of the first transistor controlled by the operational amplifier becomes smaller, the internal resistance of the first transistor becomes larger, the voltage drop between the emitter and the collector of the first transistor increases, and the current of the load loop becomes smaller. When the current of the load loop becomes smaller, the voltage of the inverting input terminal of the operational amplifier becomes smaller, the difference between the inverting input terminal and the non-inverting input terminal becomes larger, the output differential voltage of the operational amplifier becomes larger, the base current of the first transistor controlled by the operational amplifier becomes larger, the internal resistance of the first transistor becomes smaller, the voltage drop between the emitter and the collector of the first transistor decreases, and the current of the load loop becomes larger. In this way, the current of the load loop, i.e. the current flowing through the excitation coil, is finally stabilized to a constant value through the feedback of the sampling element and the adjustment of the negative feedback circuit.
[0016] In some embodiments, the negative feedback circuit further comprises: a first current-limiting resistor, which is connected in series between the output terminal of the operational amplifier and the control terminal of the first transistor.
[0017] The first current-limiting resistor protects the first transistor from overcurrent.
[0018] In some embodiments, the magnetic field strength control circuit further comprises a filter circuit, which is connected between the first signal input terminal and the non-inverting input terminal of the negative feedback circuit.
[0019] The filter circuit can filter out the noise input by the first signal input terminal, ensuring that the first control signal delivered to the negative feedback circuit is pure and reliable.
[0020] In some embodiments, the filter circuit comprises: a first filter resistor and a second filter resistor connected in parallel, first ends of the first filter resistor and the second filter resistor are respectively connected to the first signal input terminal; a first filter capacitor and a second filter capacitor connected in parallel, first ends of the first filter capacitor and the second filter capacitor are respectively connected to second ends of the second filter resistor and are commonly connected to the non-inverting input terminal of the negative feedback circuit, and second ends of the first filter capacitor and the second filter capacitor are respectively connected to second ends of the first filter resistor.
[0021] Suppose that the first signal input end inputs a rectangular wave with a duty cycle of N and a peak value of U from a central processing unit (CPU) port.
[0022] In some embodiments, the magnetic field direction control circuit comprises: a second triode connected in series with the coil of the relay, and a control end of the second triode connected to a second signal input end; when a second control signal input by the second signal input end changes, the working state of the second triode changes, and the connection state of the switching contact of the relay changes; wherein the working state of the second triode comprises a conduction state and a cut-off state.
[0023] The conduction and cut-off of the second triode are controlled by the second control signal, and the connection state of the switching contact of the relay is controlled, so that the direction of the current flowing through the excitation coil changes, thereby changing the direction of the environmental magnetic field generated by the excitation coil.
[0024] In some embodiments, the magnetic field direction control circuit further comprises: a freewheeling diode connected in antiparallel across the coil of the relay; and / or a second current-limiting resistor connected in series between the second signal input end and the control end of the second triode.
[0025] The freewheeling diode provides freewheeling for the coil of the relay, and when the relay is powered off, the electric quantity stored in the coil of the relay forms a loop through the freewheeling diode, thereby avoiding voltage impact on other components. The second current-limiting resistor limits the current flowing to the base of the second triode, thereby protecting the second triode.
[0026] According to another aspect of the present application, a permanent magnet aging system for an electric power steering system is provided, comprising: a permanent magnet for assembly in an angle sensor of the electric power steering system; and the permanent magnet aging device according to any of the above embodiments, wherein the permanent magnet is placed within the magnetic field range of the excitation coil.
[0027] Before the permanent magnet is assembled in the angle sensor, the permanent magnet is subjected to an aging test, so that the permanent magnet quickly skips the high-failure-rate stage in the early life cycle and directly enters the low-failure-rate stage in the life cycle, thereby greatly improving the reliability and stability of the electric power steering system and ensuring the safety of the electric power steering system during operation.
[0028] The present application has at least the following beneficial effects compared with the prior art:
[0029] The utility model discloses a magnetic field strength control circuit and magnetic field direction control circuit control excitation coil produces the alternating magnetic field, provide the magnetic field environment that needs for permanent magnet aging, make permanent magnet self magnetic field accelerate degradation reaches stable state, realize the efficient aging of permanent magnet, and through magnetic field strength control circuit and magnetic field direction control circuit can accurate control the strength and direction of the environmental magnetic field that excitation coil produces, control the aging degree and precision of permanent magnet, realize the accurate control of the aging progress of permanent magnet.
[0030] The utility model discloses a permanent magnet aging device, before permanent magnet installation / application, place permanent magnet in the alternating magnetic field and carry out aging test, make permanent magnet experience initial failure period rapidly, in order to directly enter the sporadic failure period of low failure rate after putting into use, improve the stability and reliability of permanent magnet after putting into use greatly, and then improve the stability and reliability of the industrial product of permanent magnet application, and also convenient for evaluating the life cycle of permanent magnet.
[0031] It should be understood that the foregoing general description and the following detailed description are only exemplary and explanatory, and cannot limit the utility model. BRIEF DESCRIPTION OF DRAWINGS
[0032] The drawings here are incorporated into the description and constitute a part of the description, show the embodiment of the utility model, and be used for explaining the principle of the utility model with the description. Obviously, the drawings in the following description only are some embodiments of the utility model, and the other drawings can be obtained according to these drawings without paying the creative labor for the ordinary skill in the art.
[0033] Figure 1 Show the failure rate curve of permanent magnet;
[0034] Figure 2 Show the circuit structure schematic drawing of permanent magnet aging device in the utility model embodiment;
[0035] Figure 3 Show the arrangement relation schematic drawing of permanent magnet and excitation coil in the utility model embodiment;
[0036] Figure 4 Show the circuit structure schematic drawing of magnetic field strength control circuit in the utility model embodiment;
[0037] Figure 5 Show the circuit structure schematic drawing of magnetic field direction control circuit in the utility model embodiment. DETAILED DESCRIPTION
[0038] Example implementations will now be described more fully with reference to the accompanying drawings. Example implementations may, however, be implemented in many different forms and should not be construed as limited to the implementations set forth herein. Rather, these implementations are provided as non-limiting examples, so that this disclosure will fully convey the scope of the application to those skilled in the art.
[0039] The accompanying drawings are included to provide a further understanding of the application, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the application and, together with the description, serve to explain the principles of the application.
[0040] The terms "first", "second", and similar terms do not imply any order, quantity, or importance, but are used to distinguish one element from another, and are used for the purpose of clear and consistent description. Furthermore, in the description of the present application, when a device is said to be "connected" to another device, this includes not only the case of direct connection, but also the case of indirect connection through other elements.
[0041] It should be noted that the features of the embodiments of the present application and the features in different embodiments can be combined with each other without conflict.
[0042] Figure 2 The circuit structure of the permanent magnet aging device is shown, Figure 3 The arrangement relationship between the permanent magnet and the field coil is shown; in combination with Figure 2 and Figure 3 The permanent magnet aging device provided by the embodiments of the present application comprises:
[0043] The load circuit 200 comprises the field coil EC and the sampling element R1 connected in series.
[0044] The magnetic field strength control circuit comprises a negative feedback circuit 310, the output end of the negative feedback circuit 310 is connected in the load circuit, and the sampling element R1 is connected to the reverse input end of the negative feedback circuit 310, and the magnetic field strength control circuit is used for controlling the strength of the environmental magnetic field generated by the field coil EC.
[0045] The magnetic field direction control circuit 400 comprises a relay KR, the relay KR has two switches (K1, K2) and two pairs of contacts (A1, A2; A3, A4), wherein each switch is matched with a pair of contacts (the switch K1 is matched with the contacts A1 and A2, and the switch K2 is matched with the contacts A3 and A4), the two switches (K1, K2) are connected in series in the load circuit 200, and each pair of contacts is connected to both ends of the field coil EC (the contacts A1 and A4 are connected to the F end of the field coil EC, and the contacts A2 and A3 are connected to the E end of the field coil EC), and the magnetic field direction control circuit 400 is used for controlling the direction of the environmental magnetic field.
[0046] The excitation coil EC generates a magnetic field with a corresponding strength under the driving of the current, the strength of the magnetic field is in a proportional relationship with the current flowing through the excitation coil EC, and the direction of the magnetic field is controllable and determined by the direction of the current flowing through the excitation coil EC. The permanent magnet PM is placed in the magnetic field range of the excitation coil EC, and the alternating magnetic field generated by the excitation coil EC is controlled by the magnetic field strength control circuit and the magnetic field direction control circuit 400, so as to provide the required magnetic field environment for the aging of the permanent magnet PM. The magnetic field strength control circuit includes a negative feedback circuit 310, the load current flowing through the excitation coil EC is fed back through the sampling element R1 connected in series with the excitation coil EC, and the current of the load circuit 200 where the excitation coil EC is located is stabilized through the adjustment of the negative feedback circuit 310, so as to control the strength of the environmental magnetic field generated by the excitation coil EC; when the input of the negative feedback circuit 310 is changed, the strength of the environmental magnetic field generated by the excitation coil EC changes accordingly. The magnetic field direction control circuit 400 includes a relay KR, the two switches of the relay KR are connected in series in the load circuit 200, and each pair of contacts is connected to the two ends of the excitation coil EC, the current direction flowing through the excitation coil EC is changed by switching the connection state between the switches and the contacts of the relay KR, and then the direction of the environmental magnetic field generated by the excitation coil EC is changed. In this way, the alternating magnetic field generated by the excitation coil EC is controlled by the magnetic field strength control circuit and the magnetic field direction control circuit 400, so that the magnetic field of the permanent magnet PM is accelerated to degrade to a stable state, and the efficient aging of the permanent magnet PM is realized; and the strength and direction of the environmental magnetic field generated by the excitation coil EC can be accurately controlled by the magnetic field strength control circuit and the magnetic field direction control circuit 400, so as to control the aging degree and precision of the permanent magnet PM, and realize the precise control of the aging progress of the permanent magnet PM.
[0047] The relay KR has two connection states: the switch K1 contacts A1 and the switch K2 contacts A3, at this time, the current of the power supply end V1 flows into the F end of the excitation coil EC and flows out of the E end; the switch K1 contacts A2 and the switch K2 contacts A4, at this time, the current of the power supply end V1 flows into the E end of the excitation coil EC and flows out of the F end.
[0048] The permanent magnet aging device is used before the permanent magnet PM is installed and applied, the permanent magnet PM is placed in the alternating magnetic field for aging test, the permanent magnet PM rapidly experiences the initial failure period, so as to directly enter the occasional failure period with low failure rate after being put into use, the stability and reliability of the permanent magnet PM after being put into use are greatly improved, and then the stability and reliability of the industrial product applied by the permanent magnet PM are improved, and the service life of the permanent magnet PM is also convenient to evaluate.
[0049] In some embodiments, in order to accelerate the aging effect of the permanent magnet PM, the permanent magnet aging test can also be carried out at high temperature, for example, the permanent magnet aging device is placed in a temperature box.
[0050] In some embodiments, when the first control signal inputted by the in-phase input end of the negative feedback circuit 310 changes, the strength of the ambient magnetic field changes; when the connection state of the switch contact of the relay KR changes, the direction of the ambient magnetic field changes; as the permanent magnet aging device operates: the value of the first control signal decreases, and / or the change frequency of the connection state decreases.
[0051] The aging speed of the permanent magnet PM is related to the strength and polarity change frequency of the ambient magnetic field. The greater the strength of the ambient magnetic field and the higher the polarity change frequency of the ambient magnetic field, the faster the aging speed of the permanent magnet PM. As the permanent magnet aging test proceeds, the strength of the ambient magnetic field is reduced by reducing the value of the first control signal of the negative feedback circuit 310, and / or the polarity change frequency of the ambient magnetic field is reduced by reducing the change frequency of the connection state of the relay KR, so that the aging progress of the permanent magnet PM is slowed down, so as to accurately control the degree and precision of the aging.
[0052] In some embodiments, as the permanent magnet aging device operates: when the magnetic field strength of any magnetic pole of the permanent magnet PM acted on by the ambient magnetic field reaches a preset threshold value, the value of the control signal decreases; when the magnetic field strength of both magnetic poles of the permanent magnet PM reaches the preset threshold value, the change frequency of the connection state decreases; when the magnetic field strength of any magnetic pole of the permanent magnet PM reaches a critical threshold value, the permanent magnet aging device stops operating; wherein the critical threshold value is the magnetic field strength corresponding to the critical value of the failure rate change of the permanent magnet PM, and the preset threshold value is greater than the critical threshold value.
[0053] Before starting the permanent magnet aging test, a large number of tests are needed to collect the failure rate and service life of the batch of permanent magnets, and the corresponding relationship between the magnetic field strength of the N pole and the S pole of the permanent magnet and the service life. The attenuation of the magnetic field strength of the permanent magnet itself is a manifestation of the aging of the permanent magnet. By determining whether the N pole and the S pole of the permanent magnet are currently at the critical point position of high failure rate and low failure rate, i.e., whether they are at the critical point position of the initial failure period and the occasional failure period, the greater magnetic field strength of the N pole and the S pole corresponding to the critical point position is taken as the critical threshold value of the batch of permanent magnets.
[0054] During the burn-in test, the magnetic field strength of the N-pole and S-pole of the permanent magnet PM is detected at a certain frequency. When one of the magnetic field strength of the N-pole and S-pole of the permanent magnet PM reaches a preset threshold, the value of the control signal is reduced to reduce the current flowing through the excitation coil EC, so as to correspondingly reduce the ambient magnetic field strength of the permanent magnet PM, at this time the detection frequency of the magnetic field strength of the permanent magnet PM itself can be increased to improve the burn-in process control accuracy. When the magnetic field strength of the N-pole and S-pole of the permanent magnet PM reaches the preset threshold, the switching frequency of the connection state of the relay KR is reduced to reduce the current direction switching frequency of the excitation coil EC, and further reduce the ambient magnetic field direction switching frequency of the permanent magnet PM, and the test frequency of the magnetic field strength of the permanent magnet PM itself can be increased again to further improve the burn-in process control accuracy. When one of the magnetic field strength of the N-pole and S-pole of the permanent magnet PM reaches the critical point position of the high failure rate and the low failure rate, the burn-in test stops. At this time, the service life of the permanent magnet PM is at the critical point position of the high failure rate and the low failure rate, that is, at the critical point position of the initial failure period and the occasional failure period, and at this time the permanent magnet PM is put into use, and the operation failure rate is at the low point of the failure period curve.
[0055] In a specific example, it is assumed that the current flowing through the excitation coil EC is I1 when the burn-in test starts, the current direction switching frequency of the excitation coil EC is H1, the permanent magnet PM is placed in the magnetic field environment of the excitation coil EC, and the magnetic field strength of the N-pole and S-pole of the permanent magnet PM is detected every detection period T1. After a period of time, the permanent magnet PM is aged to a certain extent, which is manifested as a decrease in the magnetic field strength of the permanent magnet PM itself. During the burn-in test, if the magnetic field strength of the N-pole or S-pole of the permanent magnet PM reaches a preset threshold F1, the current flowing through the excitation coil EC is reduced to I2 (I2
[0056] Figure 4 The circuit structure of the magnetic field strength control circuit is shown, combined with Figures 2 to 4As shown, in some embodiments, the negative feedback circuit 310 comprises: an operational amplifier U1, a non-inverting input terminal of the operational amplifier U1 is connected to the first signal input terminal IN1; a first transistor Q1, which is connected in series between the excitation coil EC and a sampling element R1, an output terminal of the operational amplifier U1 is connected to a control terminal of the first transistor Q1, and a series node of the first transistor Q1 and the sampling element R1 is connected to an inverting input terminal of the operational amplifier U1.
[0057] The sampling element R1 can be a sampling resistor, or other elements such as a capacitor, without being limited to the elements shown in the figure. The sampling element R1 feeds back the current of the excitation coil EC in real time. When the current of the load circuit 200 becomes larger, the voltage of the inverting input terminal of the operational amplifier U1 becomes higher, the difference between the inverting input terminal and the non-inverting input terminal becomes smaller, the output differential voltage value of the operational amplifier U1 becomes smaller, the base current of the first transistor Q1 controlled by the operational amplifier U1 becomes smaller, the internal resistance of the first transistor Q1 becomes larger, the voltage drop between the emitter and the collector of the first transistor Q1 increases, and the current of the load circuit 200 becomes smaller. When the current of the load circuit 200 becomes smaller, the voltage of the inverting input terminal of the operational amplifier U1 becomes smaller, the difference between the inverting input terminal and the non-inverting input terminal becomes larger, the output differential voltage value of the operational amplifier U1 becomes larger, the base current of the first transistor Q1 controlled by the operational amplifier U1 becomes larger, the internal resistance of the first transistor Q1 becomes smaller, the voltage drop between the emitter and the collector of the first transistor Q1 decreases, and the current of the load circuit 200 becomes larger. In this way, the current of the load circuit 200, i.e. the current flowing through the excitation coil EC, is finally stabilized to a constant value through the feedback of the sampling element R1 and the adjustment of the negative feedback circuit 310. Assuming that the first control signal input to the non-inverting input terminal of the operational amplifier U1 is a voltage V, the constant current flowing through the excitation coil EC is: I = V ÷ R1.
[0058] In other embodiments, the negative feedback circuit 310 can also be formed by other electronic elements, without being limited to the elements shown in the figure.
[0059] In some embodiments, the negative feedback circuit 310 further comprises: a first current-limiting resistor R2, which is connected in series between the output terminal of the operational amplifier U1 and the control terminal of the first transistor Q1. The first current-limiting resistor R2 plays a current-limiting protection role for the first transistor Q1.
[0060] In some embodiments, the magnetic field strength control circuit further comprises a filter circuit 320, which is connected between the first signal input terminal IN1 and the non-inverting input terminal of the negative feedback circuit 310. The filter circuit 320 can filter out the noise input by the first signal input terminal IN1, and ensure that the first control signal delivered to the negative feedback circuit 310 is pure and reliable.
[0061] In some embodiments, the filter circuit 320 comprises: a first filter resistor R3 and a second filter resistor R4 connected in parallel, and first ends of the first filter resistor R3 and the second filter resistor R4 are connected to the first signal input end IN1 respectively; a first filter capacitor C1 and a second filter capacitor C2 connected in parallel, and first ends of the first filter capacitor C1 and the second filter capacitor C2 are connected to a second end of the second filter resistor R4 and are commonly connected to the non-inverting input end of the negative feedback circuit 310, and second ends of the first filter capacitor C1 and the second filter capacitor C2 are connected to a second end of the first filter resistor R3 respectively.
[0062] Suppose that the first signal input end IN1 inputs a rectangular wave with a duty cycle of N and a peak value of U from a central processing unit CPU port. The rectangular wave gradually becomes a direct current through the filter circuit 320 composed of the first filter resistor R3 and the second filter resistor R4, and the first filter capacitor C1 and the second filter capacitor C2, and the direct current voltage amplitude is (U×N) V.
[0063] Figure 5 The circuit structure of the magnetic field direction control circuit is shown schematically; in combination with the circuits shown in Figure 2 , Figure 3 and Figure 5 In some embodiments, the magnetic field direction control circuit 400 comprises: a second triode Q2 connected in series with a coil KR1 of a relay KR, and a control end of the second triode Q2 is connected to the second signal input end IN2; when a second control signal input by the second signal input end IN2 is transformed, a working state of the second triode Q2 is transformed, and a connection state of a switching contact of the relay KR is transformed; wherein the working state of the second triode Q2 comprises a conduction state and a cut-off state.
[0064] The conduction and cut-off of the second triode Q2 are controlled through the second control signal, and then the connection state of the switching contact of the relay KR is controlled, so as to realize the transformation of the current direction flowing through the excitation coil EC, thereby changing the direction of the environmental magnetic field generated by the excitation coil EC.
[0065] Specifically, when the second triode Q2 receives a low-level second control signal, the relay KR is not powered, the switch K1 is connected to the A1 contact, the switch K2 is connected to the A3 contact, the power supply current enters the switch K1 from the power supply end V1, flows through the A1 contact, flows into the F end of the excitation coil EC, and flows out from the E end of the excitation coil EC, and the direction of the environmental magnetic field is the same as the direction of the magnetic field of the permanent magnet PM itself. When the second triode Q2 receives a high-level second control signal, the base of the second triode Q2 is in a high-level saturated conduction state, and the power supply V2 drives the relay KR to normally flip, so that the switch K1 of the relay KR is connected to the contact A2, the switch K2 is connected to the contact A4, the power supply current flows into the F end from the E end of the excitation coil EC, and then flows out, so that the direction of the environmental magnetic field is opposite to the direction of the magnetic field of the permanent magnet PM itself.
[0066] In some embodiments, the magnetic field direction control circuit 400 further comprises: a freewheeling diode D, which is anti-parallel connected across the coil KR1 of the relay KR; and / or, a second current-limiting resistor R5, which is connected in series between the second signal input end IN2 and the control end of the second triode Q2.
[0067] The freewheeling diode D freewheels the coil KR1 of the relay KR, when the relay KR is powered off, the electric quantity stored in the coil KR1 of the relay KR forms a loop through the freewheeling diode D, avoiding voltage impact on other components. The second current-limiting resistor R5 plays a role in limiting the current of the base of the second triode Q2, to protect the second triode Q2.
[0068] The utility model embodiment further provides a kind of permanent magnet aging system of electric power assisted steering system, as shown in combination Figures 2 to 5 Permanent magnet PM is used to assemble in the angle sensor of electric power assisted steering system;Permanent magnet aging device, wherein permanent magnet PM is placed in the magnetic field range of excitation coil EC.
[0069] Before the permanent magnet PM of angle sensor is assembled, permanent magnet PM is subjected to aging test, so that permanent magnet PM rapidly skips the high failure rate stage in early life cycle, and directly enters the low failure rate stage in life cycle, so that the reliability and stability of electric power assisted steering system are greatly improved, and the safety in the operation process of electric power assisted steering system is guaranteed.
[0070] Permanent magnet PM can also be applied to other industrial products, and the permanent magnet aging device of the utility model can also be used to perform aging test on permanent magnet PM before permanent magnet PM is put into use, to improve the reliability and stability of permanent magnet PM after being put into use.
[0071] The above content is a further detailed description of the utility model made in combination with specific preferred embodiments, and cannot be determined that the specific implementation of the utility model is limited to these descriptions. For ordinary skilled persons in the technical field to which the utility model belongs, without departing from the concept of the utility model, a number of simple deductions or substitutions can also be made, which should be regarded as belonging to the protection scope of the utility model.
Claims
1. A permanent magnet aging device characterized by comprising: The application relates to a permanent magnet aging device. The device comprises: a load circuit comprising a magnetizing coil and a sampling element connected in series; a magnetic field intensity control circuit comprising a negative feedback circuit, the output end of the negative feedback circuit being connected to the load circuit, and the sampling element being connected to the reverse input end of the negative feedback circuit, the magnetic field intensity control circuit being used for controlling the intensity of an ambient magnetic field generated by the magnetizing coil; 2. The permanent magnet aging device according to claim 1, wherein a magnetic field direction control circuit comprising a relay, the relay having two switches and two pairs of contacts, each switch being matched with a pair of contacts, the two switches being connected in series in the load circuit, and each pair of contacts being connected to the two ends of the magnetizing coil, the magnetic field direction control circuit being used for controlling the direction of the ambient magnetic field. When a first control signal inputted to the non-inverting input end of the negative feedback circuit changes, the intensity of the ambient magnetic field changes; when the connection state of the switch contacts of the relay changes, the direction of the ambient magnetic field changes.
3. The permanent magnet aging device of claim 2, wherein With the operation of the permanent magnet aging device: the value of the first control signal decreases, and / or the change frequency of the connection state decreases. With the operation of the permanent magnet aging device: when the magnetic field intensity of any magnetic pole of a permanent magnet acted on by the ambient magnetic field reaches a preset threshold value, the value of the control signal decreases; when the magnetic field intensity of two magnetic poles of the permanent magnet reaches the preset threshold value, the change frequency of the connection state decreases; 4. The permanent magnet burn-in device of any one of claims 1-3, wherein, when the magnetic field intensity of any magnetic pole of the permanent magnet reaches a critical threshold value, the permanent magnet aging device stops operating. The critical threshold value is the magnetic field intensity corresponding to the critical value of the failure rate change of the permanent magnet, and the preset threshold value is greater than the critical threshold value. The negative feedback circuit comprises:
5. The permanent magnet aging device of claim 4, wherein an operational amplifier, the non-inverting input end of the operational amplifier being connected to a first signal input end; a first triode connected in series between the magnetizing coil and the sampling element, the output end of the operational amplifier being connected to the control end of the first triode, and the series connection node of the first triode and the sampling element being connected to the inverting input end of the operational amplifier.
6. The permanent magnet aging device according to any one of claims 1 to 3, wherein The negative feedback circuit further comprises:
7. The permanent magnet aging device of claim 6, wherein a first current-limiting resistor connected in series between the output end of the operational amplifier and the control end of the first triode. The magnetic field intensity control circuit further comprises a filter circuit connected between the first signal input end and the non-inverting input end of the negative feedback circuit. The filter circuit comprises:
8. The permanent magnet burn-in apparatus of any one of claims 1-3, wherein, a first filter resistor and a second filter resistor connected in parallel, the first ends of the first filter resistor and the second filter resistor being respectively connected to the first signal input end; a first filter capacitor and a second filter capacitor connected in parallel, the first ends of the first filter capacitor and the second filter capacitor being respectively connected to the second end of the second filter resistor and being commonly connected to the non-inverting input end of the negative feedback circuit, and the second ends of the first filter capacitor and the second filter capacitor being respectively connected to the second ends of the first filter resistor. The magnetic field direction control circuit comprises: a second triode connected in series with the coil of the relay, and the control end of the second triode being connected to a second signal input end; When the second control signal inputted by the second signal input end changes, the working state of the second triode changes, and the connection state of the switching contact of the relay changes; The working state of the second triode includes a conducting state and a cut-off state.
9. The permanent magnet burn-in apparatus of claim 8, wherein The magnetic field direction control circuit further comprises: A freewheeling diode connected in antiparallel across the coil of the relay; And / or a second current-limiting resistor connected in series between the second signal input end and the control end of the second triode.
10. A permanent magnet burn-in system for an electric power assisted steering system, characterized by Comprise: A permanent magnet for assembling in an angle sensor of an electric power steering system; The permanent magnet is placed in the magnetic field range of the field winding.