Ferromagnetic Core Coil Device, Sensor Device, and Turbocharger

Abstract

The present invention relates to a ferrite core coil device (1) comprising an electromagnetic coil (2) and a ferrite core (3) holding the coil (2). A chord forms a bent edge (4a) of the ferrite core (3). A first sector (2a) of the coil (2) is not arranged on a bed (3a), while a second sector (2b) of the coil (2) is arranged on the bed (3a), wherein the first sector (2a) is bent around the bent edge (4a) at a bent angle (a) relative to the second sector (2b). Furthermore, the present invention relates to a sensor device (1a) having a ferrite core coil device (1) for determining the rotational speed of a metallic rotatable object (28) and a turbocharger (20) having such a sensor device (1a).

Description

Technical Field

[0001] The present invention relates to a ferrite core coil device, and more particularly, to a ferrite core coil device for a sensor device. Background Art

[0002] A turbocharger converts the waste energy in the exhaust gas of an automotive engine into compressed air and then forces it back into the automotive engine. This causes the engine to burn more fuel, thereby generating more power while consuming less energy, thus improving the overall efficiency of the combustion process. A turbocharger generally includes a turbine wheel and a compressor wheel, which are connected by a common shaft supported on a bearing system. The turbine wheel is driven by the exhaust gas, which in turn drives the compressor wheel. The compressor wheel sucks in and compresses ambient air and then feeds it into the cylinders of the engine. Through turbocharging, the performance level of a small engine can be increased to that of a large engine without turbocharging, thereby reducing fuel consumption and emissions. Therefore, turbochargers are increasingly used in diesel and gasoline engines of passenger cars, commercial vehicles, off-road vehicles, and sports cars.

[0003] Determining the rotational speed of the compressor impeller of a turbocharger is crucial for optimizing its efficiency and ensuring that the turbocharger and the engine remain within their respective safe operating ranges. Today's turbochargers need to operate reliably and continuously at continuously increasing exhaust gas temperatures and compressor inlet temperatures. Compared with their diesel counterparts, modern gasoline turbochargers have to operate in an environment of higher engine hood temperatures, with the temperature of the compressor impeller being about 200 °C or higher. Modern turbocharger compressor wheels are usually made of strong, lightweight conductive materials such as aluminum, titanium, or magnesium that can withstand high stresses. The rotational speed of such a compressor wheel can be measured, preferably by means of the active eddy current principle, in which a magnetic field is generated by an oscillating system and a sensing coil is used to detect the compressor blades as they pass through the magnetic field in front of the sensor tip.

[0004] A turbocharger speed sensor is usually realized by connecting a sensor head / sensor tip to a sensing element located close to the compressor wheel via a cable leading to the sensor electronics.

[0005] Applications for measuring the turbocharger speed face challenges because the impeller / compressor wheel (target wheel) is usually very thin (a few tenths of a millimeter; especially for passenger cars), and thus delivers a low signal. Also, the sensing distance / air gap, i.e., the distance between the sensing element (usually a standard flat coil, such as a pancake coil) and the target (blade), varies as the coil is flattened, while the inner wall of the turbocharger housing is circular / saddle-shaped and the outer shell of the impeller / compressor wheel is curved.

[0006] Generally speaking, among other factors, the type of coil used as a sensing element has a decisive influence on the shape of the detection signal. To achieve a reliable rotational speed calculation, preferably, whenever a blade passes in front of the end of the sensor, the detection signal should exhibit as sharp a signal peak as possible with sufficient amplitude. If, for example, the amplitude of the signal peak is not large enough (i.e., the signal is not strong enough), the peak may not be detected, which in turn will lead to an incorrect rotational speed. Generally, the amplitude of the detection signal decreases as the blade thickness decreases, thus making it more difficult to detect thin blades. External influences (such as the housing of the device with the sensor) also play an important role and can cause signal amplitude modulation losses of up to 50%.

[0007] In addition to the problem of weak signals from thin blades, all these solutions have another common problem, namely the occurrence of so-called "double peaks" in the detection signal. This means that a single peak may actually show two peaks. This can also lead to an incorrect rotational speed because the system may interpret the double peak as two different single peaks, i.e., two blade passages instead of one.

[0008] These properties of the output signal of the sensing element of the turbocharger cause problems in terms of the available solutions to the extent that the measured rpm (revolutions per minute) value may be incorrect.

[0009] In known applications, relatively large coils are used to obtain a strong enough output signal. However, in turbocharger applications, smaller inductive elements / coils are required to allow the end of the sensor device to be small / thin, thus avoiding negative effects such as hot spots and aerodynamic disturbances that may have a negative impact on the function of the turbocharger. When using large flat coils in the available solutions, the disturbing effect of the varying inductive distance / air gap is even stronger. In addition, the end of the sensor with such a large coil is too large to be inserted into the new generation of small turbochargers. Summary of the Invention

[0010] A ferrite core coil device, as a sensing element of a sensor device for determining the rotational speed of a metal rotatable object, includes a coil having a first sector and a second sector and a ferrite core holding the coil. The ferrite core has a disk shape lacking a disk sector and is defined by the contour of the disk and the chord of the disk. The chord forms a curved edge of the ferrite core. The first sector of the coil is not arranged on the bed of the ferrite core, while the second sector of the coil is arranged on the bed. The first sector is bent around the curved edge at a curved angle with respect to the second sector. Brief Description of the Drawings

[0011] The present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0012] Figure 1is a perspective view of a ferrite core according to an embodiment;

[0013] Figure 2 is Figure 1 a top view of the ferrite core;

[0014] Figure 3 is a perspective view of a ferrite core coil device according to an embodiment;

[0015] Figure 4 is Figure 3 a side view of the ferrite core coil device;

[0016] Figure 5 is a perspective view of a sensor device of a ferrite core coil device having Figure 3 ;

[0017] Figure 6 is Figure 5 a cross-sectional view of the sensor tip of the sensor device; and

[0018] Figure 7 is a cross-sectional side view of a turbocharger according to an embodiment of a sensor device having Figure 5 . DETAILED DESCRIPTION

[0019] The present invention will now be described in more detail by way of example with reference to the accompanying drawings, in which like reference numerals denote like elements. The described embodiments are merely possible configurations, and the various features described herein may be provided independently of each other or may be omitted.

[0020] For the purposes of the present invention, the rotatable object may, for example, be a compressor wheel of a turbocharger for an automobile, but is not limited thereto. The present invention may also be applied to various rotatable objects, provided that these objects are made of a metal suitable for the detection method described herein or contain a sufficient amount of such metal.

[0021] The term "metal" in relation to the rotatable object is understood herein to include metals or metal alloys, but the rotatable object may also include other materials such as plastics, generally provided that the amount of metal / conductivity is sufficient to trigger a detectable signal peak using the present invention.

[0022] The term "chord" used throughout the document is understood in its mathematical sense as "a chord of a circle" and is thus defined as a line segment whose endpoints both lie on the circle. However, for the purposes of the present invention, the term chord should also refer to a curve having a curvature greater than that of the circle cut out by the chord (i.e., a radius smaller than that of the circle).

[0023] The term "radius" is used herein as viewed from the central axis x of the ferrite core coil device.

[0024] Figure 1 and 2 shows the ferrite core 3 of the ferrite core coil device 1 according to an embodiment. As Figure 1 and 2 shown, the ferrite core 3 has a disc shape without disc sectors and a maximum diameter of D1. The ferrite core 3 is defined by the contour of the disc and the chord 4a of the disc. Thus, the size of the remaining disc sectors is defined by the distance of the chord 4a from the central axis x of the ferrite core coil device 1. The ferrite core 3 also has a bed 3a as a surface for placing the coil 2. As Figure 3 shown, the bed 3a has a maximum diameter D2. The bed 3a is defined by the edge wall 3b of the ferrite core 3 extending along the contour of the disc and the chord 4a marking the curved edge of the ferrite core 3. Thus, the edge wall 3b has a thickness given by D1–D2.

[0025] As Figure 1 and 2 shown, the ferrite core 3 has a pin 5 protruding from the bed 3a. In the illustrated embodiment, the pin 5 has a circular cross-section with a diameter of D3 and is thus integrally cylindrical. The pin 5 has the same axis as the ferrite core 3. The height 4b of the pin 5 from the bed 3a is substantially the same as that of the edge wall 3b, as Figure 3 shown, but in an embodiment it may also slightly exceed the height 4b of the edge wall 3b. In other embodiments, the ferrite core coil device 1 can be used without the pin 5. However, it has been found that using the pin 5 can improve the performance of the coil device 1. In addition, the attachment of the coil as described below is more secure because the coil cannot shift. In an embodiment, the thickness of the ferrite core 3 is between 0.2 mm and 2 mm. In an embodiment, the relative magnetic permeability μr of the ferrite core 3 is between 50 and 3000.

[0026] In Figure 3 and 4 is shown the ferrite core coil device 1 according to an embodiment. The ferrite core coil device 1 includes an electromagnetic coil 2 supported on Figure 1 the ferrite core 3. The output connector 6 of the coil 2 is shown in Figure 3 , through which the coil 2 can be connected to an external circuit for processing the signals transmitted by the coil device 1. The coil 2 is wound around the pin 5 and has between 10 and 30 windings in an embodiment. In an embodiment, the coil 2 occupies almost the entire surface between the edge wall 3b and the pin 5 without gaps, and the radius R2 of the wound coil 2 is less than the radius R1 of the ferrite core 3, as Figure 1 shown.

[0027] As Figure 3 and 4As shown, the coil 2 is divided into two parts, where the first sector 2a of the coil 2 wraps around and bends along the curved edge 4a (chord). The coil 2 is bent such that it substantially forms an L-shaped coil. The second sector 2b of the coil 2 rests on the bed 3a. The ratio between the first sector 2a and the second sector 2b of the coil 2 is between 1:1 and 1.5:1. As previously mentioned, in the embodiment, the pin 5 is cylindrical. Depending on the ratio between the two sectors 2a, 2b of the coil 2, which can also indirectly define the dimensions of the ferrite core 3, the pin 5 can have a shape similar to the disc itself. This is especially the case when the ratio between the sectors 2a, 2b is 1:1. In this case, the pin 5 has a cross-section that is semi-circular when viewed from the curved edge 4a. In Figure 1 the example shown, the dimensions are such that the pin 5 remains a complete circle.

[0028] In the embodiment, the coil 2 is printed on a flexible polymer substrate. The material chosen for the flexible polymer substrate is highly heat-resistant, especially capable of withstanding temperatures of at least up to 200 °C and in one embodiment up to at least 230 °C. Suitable materials are, for example, liquid crystal polymers or polyimides. The flexible polymer substrate also protects the coil 2 from breaking, as otherwise it might break due to its inherent brittleness. Another advantage of this method is the simplicity of the installation process, as the coil 2 does not have to be wound around the pin 5 manually or by machine.

[0029] Figure 4 As shown Figure 3 a side view of the ferrite core coil device 1 is shown, which emphasizes the L-shape of the coil 2. As mentioned above, the coil 2 wraps around and bends along the curved edge 4a, thereby forming two sectors 2a, 2b that are at a curved angle a with respect to each other. In the embodiment, the curved angle a is between 70 degrees and 110 degrees. In this example, the curved angle a is chosen to be 90°, which gives the best results for this exemplary application. An increase in the curved angle a greater than 90° will result in a decrease in the signal amplitude, as the magnetic field is increasingly counteracted. A decrease in the curved angle a towards a flat pancake coil less than 90° will result in the signal showing a double-pulse behavior on the thin blade. These effects are particularly pronounced for blade thicknesses less than 1 mm.

[0030] The chord 4a that defines the bed 3a is considered the line where the bed 3a terminates and the curvature of the curved region begins. This curvature is shown by the curved region at the line 4a in Figure 3 and 4 such that, taking into account the wire thickness of the coil 2, the curved region of the coil 2 fits smoothly on this curved surface. In any case, the curvature is not chosen to be so large that sharp edges are produced, which could damage the coil wire or cause the coil wire to fold, which is undesirable.

[0031] In Figure 5Shown is a sensor device 1a of a ferrite core coil device 1 according to an embodiment, and a detailed cross-sectional view of a sensor tip 15 of the sensor device 1a is shown in Figure 3 and in Figure 6 The sensor device 1a for determining the rotational speed of a rotatable object includes a sensor housing (not shown) having a connector section 7, a mounting section 8, and a sensor section 9. The above-mentioned ferrite core coil device 1, i.e., the sensing element, is arranged at the sensor tip 15 of the sensor section 9. Figure 6 Shown is how the ferrite core coil device 1 is attached to the sensor section 9 of the sensor device 1a at line 10. For this purpose, the tip 15 of the sensor section 9 has a surface substantially the same as that of the ferrite core 3 in this example, with a stepped portion for receiving the curved first sector 2a of the coil 2. The design of the step advantageously provides support for the first sector 2a of the coil 2. The sensor section tip 15 does not necessarily have to match the diameter D1 of the coil device 1.

[0032] The ferrite core coil device 1 is connected to sensor electronics for evaluating the output signal of the sensing element 1, which is arranged within the sensor section 9 as shown in Figure 5 and 6 The sensor electronics includes an integrated SOI (silicon-on-insulator) circuit, particularly in the form of an ASIC. It has been shown that using such an SOI circuit has certain advantages as it can withstand high temperatures and is thus suitable for use in harsh environments such as inside a turbocharger. In particular, the ASIC can be configured for the following parameters / characteristics: number of vanes (dividers), debouncer, output pulse width, maximum frequency range of the output signal, error detection frequency range, detection threshold and hysteresis, short-circuit detection time, overheat shutdown threshold, oscillator adjustment, demodulator adjustment, bandgap adjustment, and / or error flag disabling and enabling. Error flag disabling and enabling may be of particular interest: coil break (break of the sensing element 1), overheat detection (regarding the environment of the sensor device 1a), data integrity detection, overvoltage and undervoltage detection (e.g., to protect the engine control unit to which the sensor device 1a is connected), frequency error (e.g., whether the compressor wheel speed is too low). Thus, a diagnostic function / system can be incorporated into the ASIC and configured in an application-related manner, and this diagnostic system monitors overvoltage and undervoltage, overheat, data integrity, frequency error, coil / sensing element breakage, and / or short circuit.

[0033] In Figure 7 shown is a turbocharger 20 according to an embodiment, in which Figure 5 and 6The sensor device 1a. The turbocharger 20 has a turbocharger housing 21. Inside the turbocharger housing 21, a compressor wheel or impeller 28 attached to a shaft through a compressor inlet 29 is arranged, and it is connected to a turbine wheel through a shaft (not shown). A recess is provided in a wall 30 (shaded area) of the turbocharger housing 21, in which at least the sensor section 9 of the sensor device 1a can be introduced and fixed in a desired operating position.

[0034] As Figure 7 shown, the connector section 7 of the sensor device 1a is connected to sensor electronics to further process the sensor signal. The mounting section 8 is formed as a flange having an insertion hole through which a bolt or other fixing means can pass to firmly attach the sensor device 1a to the outside of the turbocharger housing 21. The sensor section 9 of the sensor device 1a is positioned such that the sensor tip 15, i.e., the ferrite core coil device 1 of the sensor device 1a, faces a plurality of blades 26 of the compressor wheel 28, as Figure 7 shown. In an embodiment, the hole accommodating the sensor device 1a is tapered towards the sensor tip 15, and the diameter of the sensor tip 15 can be smaller than the diameter of the rest of the sensor device 1a. In this way, it is ensured that the sensor tip 15 is tightly fitted into the tapered portion of the hole.

[0035] Hereinafter, the installation and operation method of the sensor device 1a will be described in more detail in conjunction with the basic measurement principle of the ferrite core coil device 1, which has been briefly outlined at the beginning.

[0036] To measure the rotational speed of the compressor wheel 28, the sensing element 1 is part of an oscillator box formed by a coil 2, a capacitor, and an integrated SOI circuit / ASIC. This results in an electromagnetic field being generated around the sensing element 1, and its magnetic flux lines "jump out" of the plane of the sensing element 1. If a conductive target / object such as an impeller / compressor blade 26 approaches the sensing element 1, the magnetic flux lines pass through the blade 26 and induce eddy currents therein. The eddy currents in the blade 26 also generate an electromagnetic field that cancels the electromagnetic field generated by the sensing element 1, thereby affecting the impedance of the sensing element 1 and thus the oscillation frequency. When the blade 26 approaches the sensing element 1, the eddy current effect increases. The changing impedance of the sensing element 1 is reflected in the modulation of the oscillation frequency. By evaluating this frequency by the sensor electronics and / or the engine control unit, a current or voltage signal corresponding to the rotational speed of the impeller / compressor wheel blade 26 is obtained, and thus the rotational speed can be determined.

[0037] As described above, the sensor device 1a is placed such that the sensor tip 15 is at a predetermined distance from the rotatable object. In Figure 7In a specific example of the turbocharger 20, the tubular sensor device 1a is introduced into and inserted into a recess in the wall 30 of the turbocharger 20 until the sensor tip 15 is at a specific distance from the impeller. This can be seen at the position shown by the arrow 37 in Figure 7 In the embodiment, this distance is between 0.5 and 1 mm from the rotating impeller.

[0038] Generally, after connecting the sensor 1a to the sensor electronics for further processing, an input current is applied to the ferrite core coil device 1, and the amplitude-modulated output voltage signal is read as the output of the sensor device 1a and processed by the sensor electronics. The sensor electronics determines the rotational speed of the impeller by evaluating the demodulated output voltage signal of the sensor device 1a.

[0039] The sensor device 1a can be used, for example, for sensing the compressor wheel blades 26 of turbochargers in automotive, truck, off-highway vehicle, aerospace, or power generation applications. In addition, the sensor device 1a can be used in any application that requires measuring / detecting the rotational speed, especially for applications with small dimensions and / or high ambient temperatures and / or applications where the target / object material has a lower electrical conductivity than aluminum (such as impeller blades with a thin geometry, e.g., made of titanium). However, the present invention can be integrated into all types of industrial machines containing rotating components, such as in production lines, etc., especially for applications that require high reliability of the rotating components. The turbocharger 20 is used in automotive engines and can also be used in other applications especially related to propulsion technologies including aerospace, etc.

[0040] By using the ferrite core 3 together with the L coil 2, the signal amplitude can be increased, and the ferrite core 3 acts as an amplifier for detecting the signal. Thereby, a more reliable distinction is achieved between different "true" signal peaks. At the same time, the shape and relative arrangement of the coil 2 and the ferrite core 3 of the sensor device 1a enable the complete avoidance of double peaks (even for a thin coil of about 0.2 mm), and advantageously achieve an increased sensor sensitivity compared to known sensors, and enable better or even error-free signal peak detection. Therefore, the risk of false assumption (detection) of the existence of two signal peaks (i.e., two blade channels) instead of one signal peak is minimized or avoided. In addition, the increased sensor sensitivity allows an increase in the distance between the sensor device 1a and the blade, i.e., the air gap, thus simplifying the production process because the positioning accuracy requirements of the sensor are lower than those of known solutions.

Claims

1. A ferrite core coil device (1), as a sensing element of a sensor device (1a) for determining the rotational speed of a metallic rotatable object (28), comprises an electromagnetic coil (2) and a ferrite core (3) holding the coil (2). wherein, The ferrite core (3) has a disc shape lacking disc sectors, and thus has a shape defined by the contour of the disc and a chord (4a) of the disc, wherein the chord forms a curved edge (4a) of the ferrite core (3), wherein a first sector (2a) of the coil (2) is not arranged on the bed (3a), while a second sector (2b) of the coil (2) is arranged on the bed (3a), wherein the first sector (2a) is bent around the curved edge (4a) at a bending angle (a) with respect to the second sector (2b).

2. The ferrite core coil device according to claim 1, wherein, The ferrite core has a pin (5) protruding from the bed (3a), and the coil (2) is wound around the pin (5).

3. The ferrite core coil device according to claim 2, wherein, The pin (5) has the same axis (x) as the ferrite core (3).

4. The ferrite core coil device according to claim 1, wherein, The bed (3a) is defined by a support edge wall (3b) of the ferrite core (3) extending along the contour of the disc and by the edge (4a).

5. The ferrite core coil device according to claim 4, wherein, The height of the pin (5) from the bed (3a) is substantially the same as the height of the edge wall (3b) from the bed (3a).

6. The ferrite core coil device according to claim 1, wherein, The radius (R2) of the wound coil is smaller than the radius (R1) of the ferrite core (3).

7. The ferrite core coil device according to claim 1, wherein, The area ratio between the first sector (2a) and the second sector (2b) of the coil (2) is between 1:1 and 1.5:

1.

8. The ferrite core coil device according to claim 1, wherein, The bending angle (a) is between 70 degrees and 110 degrees.

9. The ferrite core coil device according to claim 8, wherein, The coil (2) is a substantially L-shaped coil with a bending angle of 90°.

10. The ferrite core coil device according to claim 1, wherein, The coil (2) has 10 to 30 windings.

11. The ferrite core coil device according to claim 1, wherein, The coil (2) is wound such that all windings of the coil (2) are in contact with the bed (3a).

12. The ferrite core coil device according to claim 1, wherein, The coil (2) is printed on a flexible polymer substrate.

13. The ferrite core coil device according to claim 1, wherein, The thickness of the ferrite core (3) is between 0.2 mm and 2 mm.

14. The ferrite core coil device according to claim 1, wherein, The magnetic permeability μr of the ferrite core (3) is between 50 and 3000.

15. A sensor device (1a) for determining the rotational speed of a rotatable object (28), comprising a sensor housing having a sensor section (9), a mounting section (8) and a connector section (7), wherein, The ferrite core coil device (1) according to any one of the preceding claims is arranged at the sensor end (15) of the sensor section (9).

16. A turbocharger (20) having a turbocharger housing (21) and a sensor device (1a) according to claim 15, wherein, The compressor impeller (28) is arranged inside the turbocharger housing (21), and the wall (30) of the turbocharger housing (21) is provided with a recess, wherein at least the sensor section (9) of the sensor device (1a) is arranged such that the ferrite core coil device (1) of the sensor device (1a) protrudes from the compressor impeller (28) through the wall (30) facing the impeller (28) at a predetermined distance (37).

17. The turbocharger (20) according to claim 16, wherein the ferrite core coil device (1) of the sensor device (1a) projects from the compressor impeller (28) through the wall (30) facing the impeller (28) at a distance between 0.5 mm and 1 mm.

18. A method for determining the rotational speed of a rotatable object by means of a sensor device (1a) according to claim 15, comprising the following steps: The sensor device (1a) is placed such that the sensor end (15) is at a predetermined distance (37) from the rotating object (28), An input current is applied to the ferrite core coil device (1), An amplitude-modulated output voltage signal is read as the output of the sensor device (1a), and The rotational speed is determined by evaluating the demodulated output voltage signal of the sensor device (1a).

19. The method according to claim 18, wherein the rotatable object is a turbocharger blade.

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