WO1994005975A1

WO1994005975A1 - Unit using hall elements for determining the position of the throttle valve in an internal-combustion engine

Info

Publication number: WO1994005975A1
Application number: PCT/DE1993/000742
Authority: WO
Inventors: Joachim Melbert
Original assignee: Siemens Aktiengesellschaft
Priority date: 1992-09-09
Filing date: 1993-08-17
Publication date: 1994-03-17
Also published as: EP0659268A1; JPH08500901A; DE9212158U1

Abstract

The unit proposed for determining the position of the throttle valve in an internal-combustion engine includes a device with means for producing a magnetic field and an array made up of a multiplicity of Hall elements. The Hall elements are spaced a given distance apart along a given line. A magnetic-induction effect is produced which is dependent on the throttle-valve position. Also included is an interpolation circuit which interpolates the analogue output signals from at least two Hall elements to produce a common analogue output signal.

Description

Arrangement for detecting the throttle valve position in an internal combustion engine with Hall elements

The invention relates to an arrangement for detecting the throttle valve position in an internal combustion engine with Hall elements according to the preamble of claim 1

A throttle valve angle sensor for internal combustion engines is described in DE 38 26 408 AI. Here, a throttle valve angle sensor for internal combustion engines with a permanent magnet attached to one end of the throttle valve shaft is described, which generates a parallel magnetic flux whose direction is rotated depending on the rotation of the throttle valve shaft. Here, a magnetically sensitive element, such as, for example, is essentially parallel to the main direction of the external magnetic flux of the permanent magnet and at a distance from the permanent magnet. a Hall element is arranged, by means of which the change in the magnetic flux density as a result of the rotation of the permanent magnet is measured. The measured change in magnetic flux density is converted into a corresponding change in an electrical signal via an amplifying electrical circuit.

The output variable of the magnetically sensitive element is usually superimposed on a constant variable, a so-called offset, which is independent of the magnetic field. An output current is a superimposed DC current and an output voltage is a superimposed DC voltage. This offset as well as the gain and linearity of Hall elements fluctuate very strongly from element to element and with temperature. In addition, the linearity range of magnetically sensitive elements, such as Hall elements, is very limited, so that a complex adjustment is required in a known arrangement described above and, in addition, due to the problems mentioned, the resolution, ie the dynamic range or the precision of the measurement result such an arrangement is not very large. Precision potentiometers are therefore mostly used in applications in which precise geometry detection is also to be ensured when brief power failures can occur. However, they experience problems due to aging or poor contacts due to contamination or corrosion.

When determining the throttle valve position in internal combustion engines, it is necessary to precisely determine the actual current geometry detection, in particular in vehicle construction, at any time, even immediately after a brief supply voltage failure or immediately after switching on the arrangement for position detection. This is with an arrangement according to DE

38 26 408 AI possible in principle. In the book "Semiconductor Sensors", edited by Prof. Dr. Ing. WJ Bartz et al., Expert Verlag are described in chapter 6.4 on page 259 ff., In particular in part 6.4.3 "Analog position detection" on pages 265 to 267 position detection arrangements, as they can be used in such an arrangement. The Hall voltage is simply used as a distance criterion depending on the distance of a Hall element from a movable permanent magnet. As can be seen particularly in Figure 6.20 on page 625, such an arrangement is characterized by a very small area with a linear relationship between the change in distance and the change in magnetic field. The object of the present invention is to provide an arrangement for geometry detection using Hall elements, in which the aforementioned problems do not occur or only to a very small extent.

This object is achieved by an arrangement with the features of claim 1. Favorable embodiments are the subject of subclaims. An arrangement according to the invention for detecting the throttle valve position contains a multiplicity of Hall elements which are arranged either along a straight line or along a predetermined line at a predetermined distance from one another and from an interpolation circuit which interpolates at least the analog output variable from two Hall elements. With such an arrangement, the geometric distribution of a constant magnetic field along the Hall element chain can be recorded. Here, the linear areas of the individual Hall elements are overlaid by interpolating the output variables of the individual Hall elements and depending on the geometric arrangement of the individual Hall elements such that the overall arrangement covers a very large area with a linear relationship between the change in geometry of the detecting magnetic field and the output signal of the

Overall arrangement. If the overall arrangement ensures that the magnetic induction detected by the Hall element arrangement can be unambiguously assigned to the relative geometric arrangement between the Hall element arrangement and an object, i.e. the throttle valve position, then a throttle valve position can be unambiguously assigned to each level of the output signal of the interpolation circuit. Here, by varying the distances between individual Hall elements, by variation of the operating point of the individual Hall elements and by appropriate dimensioning of the interpolation circuit, a linear relationship between the geometric variable to be detected and the analog value of the output signal of the interpolation circuit can be achieved.

A linearization of the relationship between the geometric relationship to be detected and the electrical output signal of the arrangement within the preferably monolithically integrated circuit greatly simplifies the construction and adjustment of an overall arrangement. It only has to be ensured that there is a linear relationship between the geometric relationship to be detected, for example a throttle valve position, and the geometric distribution of a DC magnetic field over the Hall element arrangement.

In the case of an arrangement according to the invention, the geometric arrangement of a constant magnetic field is detected. In contrast, in a known arrangement, a change in the strength of the magnetic field caused by the change in geometry is detected independently of its geometric distribution. The invention is explained in more detail below with reference to the figures.

It shows:

Figure 1 is a schematic, perspective view of an embodiment of an inventive

Arrangement with a device with a magnetic field source and an arrangement of a plurality of Hall elements which are arranged along a straight line in the example and with an interpolation circuit; FIG. 2a shows a schematic illustration of a large number of Hall elements, as can be used in an arrangement according to FIG. 1;

Figure 2b, the magnetic field distribution or the magnetic

Induction B as a function of location, as it acts on the plurality of Hall elements in an arrangement according to FIG. 1;

Figure 2c in a schematic representation of the location-dependent

Hall voltage curve for the individual Hall elements according to FIG. 2a;

3a shows a possible embodiment of an interpolation circuit for an arrangement according to the invention, in which a differential amplifier is assigned to each Hall element;

3b shows the signal curve of the non-inverting output of an interpolation circuit according to FIG. 3a and the corresponding signal curves for the individual differential amplifier arrangements of this interpolation circuit;

Figure 3c another possible embodiment of a

Interpolation circuit;

Figure 4 shows another possible embodiment of a

Diaphragm in connection with a shield for use in a device with magnetic field source in Figure 1, which is suitable for a local

Magnetic field change in the longitudinal direction in response to an angle of rotation. Figure 5 shows another possible embodiment of an arrangement according to the invention.

FIG. 1 shows a schematic representation of an embodiment of an arrangement for detecting a geometric relationship with a device Q with a magnetic field source Mg. The magnetic field source Mg is preferably designed as a permanent magnet and turns off 1 a constant surface-distributed magnetic field with the magnetic induction B ready. The arrangement according to FIG. 1 contains six Hall elements H ₁ , H ₂ , H ₃ , H ₄ , H ₅ and H ₆ , which are arranged along a straight line G in the exemplary embodiment such that the magnetic field lines of the magnetic field source Mg are essentially parallel to one another with respect to the Hall element arrangement. The device with magnetic field source Q has a screening device Seh which extends at least between the magnetic field source Mg and the Hall element arrangement H ₁ ... and which has a predetermined opening OP in the area between the magnetic field source Mg and the Hall element arrangement. This opening OP can be completely or partially covered by a diaphragm BL. In the exemplary embodiment shown, with Hall elements H ₁ ... H ₆ arranged along a straight line G, the opening OP is elongated and extends parallel to the straight line G. The diaphragm BL is dependent on the movement of an object EG, whose relative position to the Hall element arrangement H ₁ ... H ₆ can be detected, can be moved along a line that extends parallel to the straight line G. Here, the opening width of the diaphragm in the longitudinal direction depends on the momentary arrangement of the diaphragm and thus of the object EG along a distance 1. In this arrangement, the device Q with the magnetic field source Mg, depending on the current position of the object EG, places it over a certain range of the plurality of Hall elements a magnetic field which is essentially uniform per unit area or unit length. The Hall elements acted upon by this magnetic field or the magnetic induction dependent thereon each deliver a Hall voltage dependent on the magnetic induction at their output. The outputs of the individual Hall elements H ₁ , H ₂ ... H ₆ are connected to an interpolation circuit IPS. This interpola tion circuit IPS provides a signal Io at an output depending on the Hall voltages of the individual Hall elements. The output of the interpolation circuit IPS is connected to an input of an evaluation circuit AS. The plurality of Hall elements, the interpolation circuit and the evaluation circuit are preferably integrated in a single semiconductor body HL in the exemplary embodiment according to FIG. 1. The evaluation circuit AS can be designed differently depending on the application. In particular, it can contain an analog-to-digital converter.

FIG. 4 shows an alternative embodiment of a device with a magnetic field source for an arrangement according to FIG. 1. The shielding device SCH here has a slot-shaped, essentially elongated opening OP, which is between the magnetic field source (see FIG. 1) and the Hall element arrangement (see FIG. 1). is aligned parallel to the alignment line G of the Hall elements. The aperture BL1 has a specially designed curved edge K and is rotatably mounted in a rotation point RP, which is located on the center line of the opening OP in the longitudinal direction. The edge K is shaped in such a way that a change in the angle of rotation of the diaphragm BL1 leads to a change in the length of the opening which is released by the diaphragm BL1 and the opening OP of the shielding device. The embodiment shown is suitable for converting an angular rotation of 90 ° into a change in length proportional to this.

Figure 2a shows a schematic representation of a number of Hall elements arranged along a straight line. Here, the first element Hl, two adjacent elements Hi and Hj and the last element Hn are shown. The total number of Hall elements should be n, where n is an integer, positive number greater than 1. FIG. 2a shows an operating point _{current source} I _Hl , I _Hi ... I _Hn for each Hall element. The output voltages of the individual Hall elements U _Hl , U _Hi , U _Hj and U _{Hn are also} shown.

FIG. 2b shows the potential course of the magnetic induction over the Hall element arrangement as a function of the distance 1. The limit values are shown in dashed lines and an exemplary value is shown in full line. As can be seen, in an arrangement according to the invention, a constant magnetic induction preferably acts on the Hall element arrangement depending on the length. FIG. 2c shows a schematic representation of the Hall voltages U _Hl , U _Hi , U _Hj and U _Hn provided by the respective Hall elements H1, Hi, Hj and Hn, depending on the length 1. In the simplest case, an evaluation can take place in such a way that the Hall elements are connected in series, so that the individual output voltages are added up. Then there is a quasi-linear relationship, since the individual Hall elements deliver a linear output voltage in partial areas.

FIG. 3a shows a possible embodiment of an interpolation circuit IPS for use in an arrangement according to the invention. The interpolation circuit shown provides a differential amplifier stage with a voltage signal input and a current signal output for each Hall element Hl, ... Hi, ... Hn. The current signal outputs of the individual differential amplifier stages DVi, DVj are combined in a common current node. Here are the leading outputs of the positive output signal Io _i ⁺ , Io _j ⁺ , ... gears of the differential amplifier stages DVi, DVj, ... combined in a common current node ∑ Io ⁺ and leading the negative current output signal Io _i -, Io _j -, ...

Signal outputs of the differential amplifier stages DVi, DVj, ... form the common current output ∑Io-. The operating points of the individual differential amplifier stages DVi,

DVj, ... are each set via a current source with a current Io _i , Io _j , ... Each differential amplifier stage has a, preferably symmetrical, signal input which is connected to the signal output of an individual Hall element Hl, ... Hi, Hj ... Hn and thus acts on the corresponding Hall voltage U _Hi , U _Hj , ... is. For the arrangement shown in FIG. 3a, the total current of all current sources Io _i , Io _j , ... which set the respective operating point is constant and the current

Io forms. The current ∑ Io is composed of the positive signal currents and the negative signal currents, so that the following applies:

∑ lo = ∑ Io- + ∑ Io ⁺ .

FIG. 3c shows a further embodiment of the interpolation circuit shown in FIG. 3a. Compared to the circuit according to FIG. 3a, it optionally has the following modifications. In addition, a negative feedback resistor R _i is interposed between the emitters of the differential amplifier stage. Furthermore, partial collector currents I _k 'can be connected from one of the transistors for negative feedback to the respective other current node ∑ I _o ⁺ or ∑ I _o -. Finally, an individual isolating amplifier V _i with selectable amplification can be connected upstream of the inputs of each evaluation stage.

Figure 3b shows the course of the individual positive current signals Io _l ⁺ , Io _i ⁺ , Io _i ⁺ , ... Io _n ⁺ in an arrangement according to Figure 3a and the course of the current signal ∑ lo ⁺ of Ge complete arrangement for the case that an even number of Hall elements is used. The illustration according to FIG. 3b is idealized, but largely gives the relationship between a location-dependent magnetic field and an output signal of an interpolation circuit IPS for an arrangement according to the invention, as shown for example in FIG. 1. The linearity of the relationship between location and output signal can be optimized by various measures. On the one hand, the Hall sensors can be arranged at different distances from one another or, overall, can be designed differently. In addition, the operating point currents Io _l , ... Io _i , Io _j , ... Io _{n of} the individual differential amplifier stage DVi, ... of an interpolation circuit can be of different sizes. Furthermore, the differential amplifiers can have different geometries. A negative feedback in the differential amplifiers of an interpolation circuit IPS also leads to a change in the location-dependent output signal of the overall arrangement. Another possibility of implementing an interpolation circuit is to use cross-coupled differential amplifiers, the base connections of two transistors with different emitter areas of different sizes being connected together in a bipolar configuration and forming an input gate of the differential amplifier circuit, the emitter connections of the four transistors forming a differential amplifier stage also being connected together are and are connected to a supply potential via a constant current source and the collector connections of the transistors are connected together, which differ both in the emitter area and in the signal input.

Figure 5 shows a further embodiment of the arrangement according to the invention. The schematic illustration again shows a magnetic field source Mg for generating a pa parallel magnetic field between two poles similar to a horseshoe magnet. The first pole Fe1 is firmly connected to the magnetic field source M. The second is horizontally movable on its longitudinal axis. In the example shown, the first pole Fe1 is located below and the second movable pole Fe2 above the magnetic field source Mg. Between the poles Fe1 and Fe2, a large number of Hall elements H ₁ ... H are attached to the pole Fe1. These can be integrated in an integrated circuit, for example. By moving the pole Fe2, a constant magnetic field flows through more or less Hall elements H _I to H _n . When evaluating by means of one of the understanding evaluation circuits, an output voltage that is linear to the movement of the pole Fe2 can be generated.

An advantage of an arrangement according to the invention for geometry detection with Hall elements is that the temperature dependency and supply voltage dependency of the offset signal, the linearity and the amplification given in known arrangements are substantially reduced by a factor which corresponds to the reciprocal of the number of Hall elements used. Corresponds to elements and that far larger geometries can be detected.

Claims

1. Arrangement for detecting the throttle valve position in an internal combustion engine with a device with a magnetic field source and an arrangement of a plurality of

Hall elements, the device with a magnetic field source providing the Hall element arrangement with magnetic induction dependent on the throttle valve position, and the Hall element arrangement converting this geometry-dependent magnetic induction into an electrical analog signal,

characterized ,

that the plurality of Hall elements are arranged at a predetermined distance from one another along a predetermined line and that an interpolation circuit is provided which interpolates the analog output signals of at least two Hall elements to form a common analog output signal.

2. Arrangement according to claim 1,

characterized ,

that the distances between two adjacent Hall elements are each the same size.

3. Arrangement according to one of claims 1 or 2,

characterized ,

that the Hall elements are arranged along a straight line.

4. Arrangement according to one of claims 1 or 2,

characterized ,

that the Hall elements are arranged along a line describing a circular path.

5. Arrangement according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t,

that the Hall element arrangement and the interpolation circuit are monolithically integrated together.

6. Arrangement according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t,

that the interpolation circuit for each Hall element (Hl, ..., Hn) a differential amplifier stage (D _Vi , D _Vj ) with a voltage signal _input (U _Hi ; U _Hj ) and a current signal output (I _oi ⁺ _, I _oi -; I _oj ⁺ , I _oj -) to a common one

Current nodes (∑ I _o ⁺ , Σ I _o -) are combined.

7. Arrangement according to claim 6,

characterized ,

that a differential amplifier stage consists of two transistors whose emitters are connected via a current source (I _oi ; I _oj ) to a reference potential, at whose base connections the input voltage can be fed and at whose collectors the output current can be tapped.

8. Arrangement according to claim 7,

characterized ,

that a resistor (R.) is connected between the emitters of the transistors.

9. Arrangement according to claim 7 or 8,

characterized ,

that a collector partial current (I _k ') is fed to the respective collector connection of the other transistor via a further collector connection of a transistor.

10. Arrangement according to one of claims 7 to 9,

characterized ,

that an isolation amplifier (V _i ) is provided which the Input of a differential amplifier stage (DV _i , DV _j ) is connected upstream and has an adjustable gain.