CN2577287Y - Gear sensor - Google Patents

Abstract

The utility model discloses a gear sensor, which comprises a magneto element and a magnet which are encapsulated in a casing together. The utility model is characterized in that the magneto element is a giant magnet resistor sensor; the shaft core direction of the magneto element is the magnetic sensibility direction and is the same with the shaft core direction of the magnet. Because the giant magnet resistor (GMR) chip has the sensitivity which is two magnitudes higher than a Hall element, even if anti-interference shielding measures are adopted, the giant magnet resistor chip can still cause the sensitivity of the gear sensor to be increased by one magnitude. Under the condition of the same detecting distance, the intensity of magnetic deviation field can be reduced and the magnet resistance is correspondingly reduced, and the utility model is good for reducing power consumption and increasing stability; in addition, the utility model also adopts a conducting magnet to reinforce the magnetization to a gear, and simultaneously, uses the conducting magnet to shield the interference.

Description

Gear sensor

Technical field:

The utility model relates to a kind of gear sensor.

Background technology:

Gear sensor is mainly used in the tachometric survey to the rotation middle gear, the almost bound gear sensor in cogged place in automation control system, in industrial automation lathe robot, use more, because the mechanical system of automatic control, the rotation of rotatable parts be unable to do without the driving of servomotor, the effective means of control is the control to servomotor, in such control system, frequency multiplier of gear sensor equivalence, whenever circling is an exportable n pulse (n is the number of teeth of gear), obviously the number of teeth the more, the umber of pulse of under certain revolution, exporting the more, attainable control accuracy is higher.In utmost point rotation at a slow speed detected, this was a very outstanding advantage, and gear sensor is directly to export with the form of frequency or pulse, therefore can directly link to each other with computing machine, need not to adopt A/D converter, even can directly drive AC servo motor, in testing process, be contactless the detection between sensor and the tested gear, thereby to gear and sensitive element, equal not damaged, thereby for detecting device, can be described as " forever " property, promptly long-life.

In the mechanical rotation system, rugged surroundings such as vibrations, impact, greasy dirt, the degree of bearing of gear sensor is far superior to light sensor.

Therefore, gear sensor more and more is subjected to vast automation control system designers' favor.

Principle: gear sensor is to be detected object with the gear, is made up of following three parts: the A. gear; B. sensitive element; C. bias field.Its middle gear generally is cold-rolled steel and makes, and from the magnetics angle, its material is a paramagnetic material, and the energy magnetic conduction is by magnetic field magnetisation; The sensitive element of gear sensor is by forming magneto sensors such as the Hall of magnetic-field-sensitive or magneto-resistors, and in the composition structure of sensor (head), this magneto sensor is between bias field and the gear.Bias field is to magnetize for the tooth to gear, gear in rotation could form " tooth signal " (except magnetic gear, magnetic linkage, magnetic coder), and detected by magneto sensor, this magnetic bias is generally finished with permanent magnet, magnetic induction density B generally between 200-3000 Gauss, requires this magnet that higher temperature stability will be arranged.

With magneto sensor, bias field (magnet) is encapsulated in a suitable manner and constitutes a detection front end (head) in the housing, in this housing of also subsequent conditioning circuit also can being packed into sometimes.Fig. 1 is that gear sensor detects synoptic diagram.

But existing gear sensor also has the high problem of insufficient sensitivity, can cause bigger problem under many application scenarios.As: because sensitivity is low, need to strengthen bias field, this can cause system's radial force to increase, and influences the stability of system, and this should be avoided in precision machining system; And for example: can cause reluctance force big when bias field is too big, this problem also can not be ignored in the rotary system of little power consumption.

Summary of the invention:

The purpose of this utility model is exactly in order to overcome the above problems, and a kind of gear sensor is provided, and improves its sensitivity.

The utility model realizes that the scheme of above-mentioned purpose is: a kind of gear sensor, comprise magneto sensor, magnet, and the two mutual encapsulation is in a housing; It is characterized in that: described magneto sensor is a giant magnetoresistance sensor, and its shaft core direction is magnetosensitive sense direction, and is consistent with the shaft core direction of magnet.

Adopt the beneficial effect of above scheme: owing to adopted giant magnetoresistance (GMR) chip, it has the sensitivity that exceeds 2 magnitudes than Hall element, even adopted anti-interference shielding measure, still can make the sensitivity of gear sensor improve an order of magnitude.Under the situation of similar detection distance, the magnetic biasing field intensity can reduce greatly, and reluctance force is also corresponding to be reduced, and helps reducing power consumption, increases stability.

Description of drawings:

Fig. 1 detects synoptic diagram for gear sensor.

Fig. 2 is a GMR chip magnetoresistive characteristic;

Fig. 3 is the gear graph that launches along straight line;

Fig. 4 is chip internal structure figure;

Fig. 5 is practical testing circuit one figure;

Fig. 6 is practical testing circuit two figure;

Fig. 7 is zeroing circuit figure;

Fig. 8 is level comparison circuit figure;

Fig. 9 a, 9b for this gear sensor main body---sensing head prepares synoptic diagram;

Fig. 9 c is main body---the synoptic diagram after sensing head is made of this gear sensor;

Figure 10 when detecting gear and magneto sensor (B), magnet (C) concern synoptic diagram.

Embodiment:

In conjunction with the accompanying drawings the utility model is described in further detail below by specific embodiment.

The utility model utilizes a kind of novel magnet-sensitive element GMR sensor as the sensitive element that detects magnetic field, and by reasonable structural design, being equipped with the speed measuring device that suitable electronic circuit constitutes superior performance together is gear sensor.Its principal feature is: (one) uses a kind of novel magnet-sensitive element GMR chip as magnetic sensitive core element, has high magnetic field sensitivity; (2) be unique bias field addition, can play of the interference of shielding stray magnetic field on the one hand, can guarantee the highly sensitive detection of chip effectively to the gear premagnetization on the other hand chip.

We are not difficult to find out that the mistor RH in the GMR chip is an even function from Fig. 2, and the magneto-resistor resistance increases family curve with the increase in magnetic field, and irrelevant with magnetic direction.This point is different with Hall element, when encapsulating, four GRM resistance is arranged usually by sealing for universal GMR chip in chip piece, and this structure is suitable for the application of traditional Wheatstone bridge testing circuit.

As can be seen from Fig. 4, chip internal has 4 mistors, and wherein R13 and R12 have taked the magnetic shielding measure in chip, is insensitive for magnetic field, and has only R11, R14 to magnetic-field-sensitive.Where is the purpose of R13, R12 adding so? fundamental purpose is R11, R14 are played the purpose of temperature stabilization.(same material has identical temperature characterisitic,) if can make R13=R14, R12=R11 (when zero magnetic field) when using, we apply a voltage V at 1.-2. two ends, its midpoint potential 3. with 4. will be to temperature-insensitive, and only to magnetic-field-sensitive, thereby part has overcome the dependence of traditional magneto-dependent sensor to temperature, make magneto sensor in application, improve temperature stability, understand chip internal structure in conjunction with Fig. 2 and Fig. 4 after, the principle of work of gear sensor has just come into plain view, so the course of work simply is described below:

When static, the magnetic flux Φ in magnetic field magnetizes gear by chip, at this moment, the static magnetic field B0 of chip place perception is exactly the initial working point of mistor R11, R14, when gear was rotated, alternately near (process) this axis with chip → magnet, this process must cause the variation by chip axle center (sensitive direction) magnetic flux φ for crown and teeth groove, cause the variation of B, thereby cause the variation of mistor value.1.-2. hold when applying voltage when this chip, 3., 4. its mid point has change in voltage when gear rotates, and this changes voltage, and we are called " tooth signal ".Fig. 3 is the gear synoptic diagram that launches along straight line.

Because the packing forms of mistor prolongs the traditional structure characteristics of having used, that is: Gordon Adams Bridge road, so subsequent detection circuit must expect adopting the bridge circuit amplifier.

According to present electronic technology level, this bridge circuit amplifier is all integrated, and it is also very handy to use, these chips, the product of the Max company of U.S. AD company, B-B company and the up-to-date adding industry is arranged, and performance level is more or less the same, and that all can shoot the arrow at the target is adopted.In order to reduce cost, in batch process, in the technical grade critical field, promptly available universal amplifier chip builds and forms.

The internal resistance of GMR chip is about 5K Ω, than the high magnitude of Hall chip, and the GMR chip adopts the stabilized voltage supply power supply, because above two big characteristics, make the feed circuit simplification that becomes, power consumption is also lower than the Hall chip, but do not reach little power consumption levels yet, requirement to this stabilized voltage supply is: temperature stability is good, and noise is low, can adopt pre-voltage stabilizing, filtering and accurate reference source to add modes such as expansion in particular application, work along both lines, raising under present electronic technology level, has not been too difficult problem to the power supply quality of sensor.

Figure 5 shows that one of practical testing circuit, this circuit is typical instrument amplifier, adopt three amplifiers to be barricaded as the instrument amplifier circuit, sensor adopts the stabilized voltage supply power supply, the electric signal that detects is by 1., 5. two ends output, deliver to A1 simultaneously, two in-phase input ends of A2, Amplifier Gain just realizes with the resistance size that changes RG, be not difficult to find out from structural drawing, A1, A2 is connected into symmetric form fully, thereby this circuit has fabulous inhibition ability to common mode voltage, generally can accomplish-the inhibition ability of 80dB--120dB, for guaranteeing that These parameters is corresponding requirement to R1=R2, (general asymmetry 1%-0.1%) is not excessive.For guaranteeing output-index, the condition of R3=R5, R4=R6 still can not be loosened index request.Under present large scale integrated circuit technology of preparing condition, these three circuit on a silicon chip integrated technology with quite ripe, and resistance R 1, R2 ... R6 etc. adopt laser trim technique, once finish, this instrument amplifier is no matter aspect encapsulation volume, and is or all quite advanced on the electricity function index.Product to AD, B-B, Maxim company all can be selected for use.Among Fig. 5, $\mathrm{<figure-callout\; id="1"\; label="Vout"\; filenames="Y0227293800112.png"\; state="\{\{state\}\}">Vout</figure-callout>}1=\mathrm{Vref}+[1+\frac{2\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="Y0227293800112.png"\; state="\{\{state\}\}">R</figure-callout>}1}{\mathrm{Rg}}]\left(\frac{R4}{R3}\right)\mathrm{Vin}$

Wherein R1=R2, R3=R5, R4=R6

Vin＝(Vout+)-(Vout-)

Shown in Figure 6 is two of practical testing circuit, be in the gear sensor subsequent conditioning circuit on GA0524-M8 actual being used, this circuit is to exchange backward end difference input mode, from circuit diagram 5 and circuit diagram 6 contrasts, be not difficult to find out that Fig. 6 circuit Magnetic Sensor adopts half arm bridging to connect mode, and signal is to adopt capacitive coupling, and the reason of doing like this is for the technical matters of the following aspects.

1. in common bridge circuit amplifier is used, when zero magnetic field, 1.-5. the midpoint potential of its bridge circuit i.e. two signal output parts should be equipotential (bridge balance) and when using the GMR chip, owing to be added with bias field, therefore in gear sensor was used, zero magnetic field state was non-existent.If still with the full-bridge place in circuit of mistor formation, 1.-5. current potential differs greatly, (even function characteristic) amplifier can not operate as normal.Therefore second half constitutes bridge circuit with adjustable potentiometer, and zeroing promptly realizes balance under the bias field state.

2. the employing of AC coupling C circuit is that it is very far away that the input impedance of in-phase input end and inverting input differs at the difference input amplifier.Two input ends are to source impedance coupling difficulty, thus employing AC coupling mode.This mode can expand in the magnetic sensor signal demodulator circuit of others, and general effect is also fine, and as near switch, magnetic coder etc., the effect of other elements has just seldom been stated.

Summary: above-described practical circuit Fig. 5 and practical circuit Fig. 6, be the part of gear sensor subsequent conditioning circuit, because the amplitude of tooth signal is very little, almost between μ V-mV, therefore the zero point drift and the noise objective of pair amplifier all have strict demand, and the one, select the low noise amplifier for use.As for the dynamic range of amplifier, requirement can be relaxed in the degree of distortion aspect, and the problem that the preparation of other aspects such as pcb board should be noted is stated in addition.

Other aspects such as wave shaping, electrical level discrimination circuit (Fig. 8), zeroing circuit (Fig. 7) because no specific (special) requirements, only provide circuit and do not analyze.

In gear sensor, sensing head is a core component, and the quality of sensing head preparation plays decisive influence to the performance of gear sensor, and this also is the emphasis that the utility model patent will be protected.

One. the selection of material

Chip: adopt No. 005 chip, saturation magnetic field intensity is: 0-85Gs

Packing forms: 8 pin

Bias field magnetic conductor: siliconized plate d=(0.05-0.5) mm, saturation magnetic field (1100-1800) Gs

Physical dimension: the front is worn into trapezoidal, and two involutory, forms duckbill, and assembling back gap width w is at 1/4-1/3T (T be crown apart from) or adjust on debugging apparatus.Bent angle length a.As shown in Figure 9.

Magnetizer: neodymium iron boron; Surface field: 3300Gs; Apart from chip center position: i

Mounting means: face pastes

Sheath: (Φ 6-Φ 20) copper is joined standard thread outward

Installation process:

The welding of chip pin, chip lead adopts enameled wire to weld, wherein two power supply lead wire twisted pair.Output lead adopts the four-core shielding line to be connected with two groups of twisted-pair feeders, and the shielding layer line links to each other with ground wire at output terminal.

Shielding line length: owing to be not with amplifying circuit in the sensor head, shielding line length is generally 1.6-2M and is advisable, and its amplifier box is fixed in the detection head appropriate positions near; If terminal device is away from detection head, suggestion adopts the model that carries amplifying circuit in the detection head for well, and at this moment, shielding line can extend to 15M.

Treat after welding of chip bias field and the installation its integral body to be pushed sheath, carry out disposable sealing.(adopt the epoxy resin sealing, before sealing, sensing head and amplifying circuit should be connected the trial run of good back, sensitivity is debugged the best.)

GMR chip system gear sensor can make detection sensitivity improve a magnitude, and the adding bias field is little, and the radial force that is subjected to of rotary body gear is greatly reduced.In rotary system, the existence of radial force, make rotation not steady, stable unfavorable to system, radial force inhomogeneous, the diameter run-out of rotary body will be caused, in the automatic control system of when Precision Machining, using, should be avoided, although be noncontact detecting the middle gear sensor, but with magnetic resistance, Hall element is in the gear sensor of core, and the adding of magnetizing field (permanent magnet) is inevitable fully.High 2 magnitudes of the remolding sensitivity Hall of GMR sensor, under the situation of similar detection distance, the magnetic biasing field intensity can reduce greatly, and reluctance force is also corresponding to be reduced, and in the rotary system of little power consumption, the sensor that the GMR chip is formed has bigger superiority than Hall.

The GMR chip is compared with Hall, the direction that adds bias field has nothing in common with each other, and it is vertical with the plane of Hall chip that Hall element adds the magnetic biasing field, and this plane (S1) is far longer than the sensitive area (S2) in GMR chip magnetic field, under the certain situation of variation rate of magnetic flux ΔΦ, tooth signal delta B can be expressed as:

Cause: Δ B1=ΔΦ/S1, Δ B2=ΔΦ/S2,

So: Δ B1＜Δ B2

GMR sensor head of the present utility model, it is different with Hall that its inclined to one side field applies direction, can avoid the sensitive direction of GMR, and not make chip saturated, makes chip keep higher sensitivity, and the magnetic bias field energy is more effective simultaneously magnetizes gear.

Magnetic conduction sheet is adopted in the adding of bias field, this magnetic conduction sheet plays the magnetic conduction effect to bias field on the one hand, and the remanent magnetism and the stray magnetic field of gear (being examined the front and back tooth of tooth) played magnetic screening action, and this remanent magnetism is to be very big sometimes on the gear of matrix adopting cold-rolled steel, surpassing 10Gs often has.This is exactly a kind of undesired signal for detecting tooth, and magnetic conduction sheet just forms shielding to the remanent magnetism of the front and back tooth of tested tooth.

When the number of teeth of gear more for a long time, just because gear sensor is exactly a frequency multiplier in speed testing controlling system originally, carry out in the magnetized process for gear, in magnetic conduction sheet the rate of change of magnetic flux equal revolution X doubly in (number of teeth) number ΔΦs=x*r/s formula x be the number of teeth, r/s is revolutions per second, if adopt whole magnetic conduction sheet, in magnetic conductor, will there be very big eddy current to exist, hamper the effective magnetizing of magnetic field to gear.Therefore, when adopting monoblock (rod) when material is done magnetic conductive media, should adopt high permeability material, lamination or nickel rod and ferrite magnetic material).

By above measure, in the application of gear sensor, the influence of turning gear remanent magnetism eddy current, three aspect factor all has change significantly, and to the stability of gear sensor, detecting distance etc. all has raising.Obviously this novelly is a kind of novelty, advanced person and new design with practicality, the above is this novel instantiation and the know-why of being used, the equivalence that the novel conception of Ruo Yiben is done changes, its function of producing does not exceed the spirit that instructions and accompanying drawing are contained yet, all should be in this novel scope, explanation hereby.

Claims (5)

1. a gear sensor comprises magneto sensor (B), magnet (C), and the two mutual encapsulation is in a housing; It is characterized in that: described magneto sensor (B) is a giant magnetoresistance sensor, and its shaft core direction is a magnetosensitive sense direction, and is consistent with the shaft core direction of magnet (C).

2. gear sensor as claimed in claim 1, it is characterized in that: described magneto sensor (B) chip internal has 4 mistors (R11-R14), constitute Wheatstone bridge, two mistors (R13, R12) on the relative brachium pontis are wherein arranged by magnetic shielding, for magnetic field is insensitive, and other two mistors (R11, R14) are to magnetic-field-sensitive.

3. gear sensor as claimed in claim 1 or 2 is characterized in that: be with magnetic conductor outside magneto sensor (B), this magnetic conductor is the duckbill of an end opening, and the opposite end of opening is near magnet (C).

4. gear sensor as claimed in claim 3 is characterized in that: magnetic conductor adopts lamination.

5. gear sensor as claimed in claim 1 or 2 is characterized in that: magnet (C) is a permanent magnet.

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