JP3477278B2 - Magnetic position sensor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic position sensor for magnetically detecting the relative position of a movable object to be detected.

[0002]

2. Description of the Related Art Conventionally, as a magnetic position sensor of this type, a throttle position sensor (Throttle Position Sensor) for detecting a throttle opening of an automobile or the like has been known. As an example, there is one disclosed in Japanese Patent Publication No. 55-13286. In this, the movable magnetic core and the fixed magnetic core are magnetically coupled to each other to form two closed magnetic paths, and a detection coil is provided in each closed magnetic path. Then, the electromotive force of each detection coil is detected by the change in the magnetic resistance of each closed magnetic circuit due to the displacement of the movable magnetic core, and the relative position of the movable magnetic core is detected.

The detection circuit of the sensor disclosed in this publication has a structure in which a position signal representing the position of the movable magnetic core is constantly output in analog form, which consumes a large amount of power and is the position signal effective? Since it has not been determined whether or not the operating environment has changed, has changed over time, has external noise, or has been powered on, etc. There was a problem that it would be detected.

Further, the circuit for generating the position signal is
It is desirable that the configuration be as simple as possible from the viewpoint of manufacturing cost and reliability, and especially for sensors used for controlling automobiles, the operating environment and conditions in the manufacturing process are also strictly required, so a robust and compact sensor is required. Long-awaited.

[0005]

In view of the above-mentioned problems, the present invention can prevent erroneous detection, detect an accurate relative position of an object to be detected, and consumes less power. An object is to provide a magnetic position sensor.
It is another object of the present invention to provide a magnetic position sensor that can contribute to reduction of manufacturing cost and improvement of reliability with a simple structure. It is a further object of the present invention to provide a robust and compact magnetic position sensor that adapts even under harsh operating environments and manufacturing processes.

[0006]

SUMMARY OF THE INVENTION A magnetic position sensor according to the present invention is a magnetic position sensor for detecting the relative position of a movable object to be detected, the magnetic position sensor including at least one exciting coil and first and second exciting coils. to the formation and detection coil, a magnetic path allowed to pass through the magnetic flux generating an electromotive force in response to the relative position of the detection object in each of said interlinked to the exciting coil first and second detection coils Magnetic path forming means and excitation command signal
Said exciting means for exciting the excitation coil, and a difference signal output means for outputting the level difference signal corresponding to the difference between the detection output level based on the electromotive force of the first and second detection coils according to item, wherein Capture that generates a capture signal when the sum of the detection output levels of the first and second detection coils reaches a predetermined value
Signal generation means and intermittently generate the excitation command signal
On the other hand, it is characterized by including control means for receiving the difference signal as a position signal in response to the capture signal .

[0007]

According to the magnetic position sensor of the present invention, the level difference signal corresponding to the difference between the detection output levels of the first and second detection coils for generating electromotive force according to the relative position of the object to be detected. Is generated, and it is determined that the sum of the detection output levels of the first and second detection coils is a predetermined value.
Then, in response to this determination, the difference signal is captured as an effective position signal indicating the relative position of the detected object.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 1 is a plan view showing a main body structure of a magnetic position sensor according to an embodiment of the present invention, and FIG.
The cross section is shown. The magnetic position sensor shown by these figures is for obtaining a linear output characteristic by detecting a rotation angle in the rotation of the object to be detected.

In FIGS. 1 and 2, the magnetic type position sensor has a fixed magnetic member 1 shown with fine dots.
, Movable magnetic member 3, exciting coil 5, and detecting coil 6
It consists of a and 6b. The fixed magnetic member 1 faces the U-shaped magnetic member 1a, the linear magnetic member 1b that joins both legs of the U-shaped magnetic member 1a, and the U-shaped magnetic member 1a of the linear magnetic member 1b. One end is fixed to the central portion on the side, and the other end has a protruding magnetic member 1c that linearly extends toward the rotation axis of the rotation shaft 2.

The shaft 2 which is the object to be detected or the moving object
Rotates about the rotation axis a. The shaft 2 is fixed to one end of the longitudinal magnetic member 3 by a screw 4 as a coupling means, and the longitudinal magnetic member 3 is rotatable around the rotation axis a together with the shaft 2. U-shaped magnetic member 1a
Has an inner surface which is arranged around the longitudinal magnetic member 3 and which has an arc centered on the rotation axis a and having a radius longer than the distance from the other end of the longitudinal magnetic member 3 to the rotation axis a. The surface and the other end surface of the longitudinal magnetic member 2 are not in contact with each other. One end of the longitudinal magnetic member 3 has an annular shape centered on the rotation axis a, and the extending end of the protruding magnetic member 1c has a shape facing and corresponding to the annular one end. The one end of the member 3 and the protruding magnetic member 1c are also not in contact with each other. The structure composed of the magnetic members 1a, 1b and 1c may be integrally formed.

An exciting coil 5 is wound around the protruding magnetic member 1c, and detection coils 6a and 6b are wound around both legs of the U-shaped magnetic member 1a. The exciting coil 5 is excited by an exciting circuit described later. As a result, when the exciting coil 5 generates a magnetomotive force, magnetic flux having a shape shown by a dotted line in FIG. 1 is distributed. The magnetic flux induced here interlinks with the detection coils 6a and 6b.
The magnetic flux density of the magnetic flux interlinking with 6b changes depending on the position of the longitudinal magnetic member 3. This is shown in FIG.

That is, the length of the magnetic path Pa of the magnetic flux interlinking the detection coil 6a and the magnetic path P of the magnetic flux interlinking the detection coil 6b.
The length b is changed complementarily depending on the position of the longitudinal magnetic member 3 facing the U-shaped magnetic member 1a, and the magnetic flux density linked to the detection coil is changed by the change in the resistance component of each magnetic path. Since the detection coils 6a and 6b generate an electromotive force according to the magnitude of the change rate of the interlinking magnetic flux, the detection coils 6a and 6b
The position (relative angle) of the longitudinal magnetic member 3, that is, the shaft 2 can be detected from the electromotive force of a, 6b, that is, the output voltage or current.

This magnetic type position sensor has a rotary shaft 2
Can be connected to, for example, a throttle valve of an internal combustion engine to function as a throttle position sensor. Further, it can be used also as a position detecting means in an automatic machine tool, an automatic carrying machine, etc., and is also suitable for factory automation (FA) and the like. Next, the operating principle of this magnetic position sensor will be described in more detail with reference to FIG.

In FIG. 3, an angle reference line l0 passing through the rotation center a of the movable magnetic member 3 and a line l1 connecting the rotation center a and the center position of the movable magnetic member 3 facing the U-shaped magnetic member 1a. When the angle formed by and is α [rad], the following equations are established corresponding to the closed magnetic paths Pa and Pb according to the Ampere's circumferential integration theorem.

[0015]

[Equation 1] H0 ・ L1 + H7 ・ L7 + H3 ・ L2 + H8 ・ L8 + H1 (L + r ・ α) = Ni (1)

[0016]

[Formula 2] H0 · L1 + H7 · L7 + H3 · L2 + H8 · L8 + H2 (L-r · α) = Ni (2) where L is the entire magnetic path formed by the U-shaped magnetic member 1a and the linear magnetic member 1b L1 is the magnetic path length formed by the protruding magnetic member 1c, L2 is the magnetic path length formed by the movable magnetic member 3, and r is the turning radius of the movable magnetic member 3, that is, the turning center a. The distance to the surface of the movable magnetic member 3 facing the U-shaped magnetic member 1a, S is the equivalent cross-sectional area of all magnetic paths, H0 and H3 are the magnetic field strengths of the protruding magnetic member 1c and the movable magnetic member 3, and H7. , H8 are the magnetic field strengths of the gaps 7 and 8, L7 and L8 are the lengths of the gaps 7 and 8, and H1 and H
2 is the magnetic field strength of the closed magnetic paths Pa and Pb, and Ni is the magnetomotive force generated in the exciting coil 5.

In the above equations (1) and (2), in order to remove the common term, the equations (1)-(2) are calculated, and the results are summarized as follows:

[0018]

## EQU3 ## α = (L / r)  (H2-H1) / (H2 + H1) (3) Here, assuming that H2 + H1 = const (const is a constant), the following equation (4) is derived.

[0019]

## EQU00004 ## H2 = (r.const..alpha.) / 2L + const / 2 (4) The voltages V1 and V2 generated in the detection coils 6a and 6b are H
Since it is proportional to 1 and H2,

[0020]

[Equation 5] V2 = (r · const · α) / 2L + const / 2 (5) Here, rearranging equation (5) with respect to α is as follows.

[0021]

[Equation 6] α = {2L / (r · const)} · (V2−const / 2) (6) As is clear from the above equation (3), H1 and H2, that is, V1
By detecting V2 and V2, the rotation angle α of the magnetic path member 5 can be obtained. If we rewrite equation (3),

[0022]

## EQU7 ## α = (L / r)  (V2-V1) / (V2 + V1) (7) That is, (L / r) is a constant, so (V1
If + V2) can be controlled to be constant, the rotation angle α of the movable magnetic member 3 can be uniquely obtained by (V2-V1). Therefore, in this case, (V2-V1) or (V1
-V2), that is, the difference between the output voltages of the two detection coils is treated as the value of the position signal representing the rotation angle α. Below, for this purpose, the output voltages V1 and V2 of the detection coils are changed to the rotation angle α.
A system for obtaining is described. In addition, (V1 + V
If 2) can be controlled to be constant, the rotation angle α of the movable magnetic member 3
Can be accurately expressed only by V2 as is clear from the equation (6).

FIG. 4 is a position signal for obtaining a position signal representing the position of the movable magnetic member 3 from the electromotive force of the detection coils 6a and 6b by exciting the exciting coil 5 of the magnetic position sensor shown in FIGS. An example of a generation and excitation control circuit is shown.
In FIG. 4, the excitation circuit 13 and the comparator 1 are included in this circuit.
5, an A / D (analog / digital) converter 16, a controller 18, resistors 32 and 33, and a voltage source 31 are used. Excitation circuit 13 generates an excitation pulse for exciting coil 5 in response to an excitation command signal issued from controller 18. When an exciting pulse is supplied to the exciting coil 5, a voltage V is applied across the detection coils 6a and 6b.
Although 1 and V2 are generated, the terminals (positive terminals) of the detection coils 6a and 6b, which indicate the positive electrode of the electromotive force generated in response to the positive level excitation pulse, are commonly connected. That is, the detection coils 6a and 6b have a differential winding configuration. The terminal (negative terminal) of the detection coil 6a, which indicates the negative electrode of the electromotive force generated with respect to the positive-level excitation pulse, is the A / D converter 16
The terminal (negative terminal) of the detection coil 6b, which is connected to the input end of the detection coil 6b and indicates the negative electrode of the electromotive force generated in response to the positive level excitation pulse, is grounded. In FIG. 4, “+” is added to the positive terminal and “−” is added to the negative terminal. By connecting both detection coils in this way, the potential of the output voltage difference V1-V2 of both detection coils, that is, the position signal appears at the negative terminal of the detection coil 6a. Therefore, such connection corresponds to the difference signal output means.

The common connection point of both detection coils is the comparator 15
It is led to the inverting input terminal of. The common connection point of the resistors 32 and 33 having the same resistance value R is connected to the non-inverting input terminal of the comparator 15. One end of the resistor 32 is connected to the position signal line, and one end of the resistor 33 is connected to the other end of the resistor 32. A constant voltage source 31 is provided at the other end of the resistor 33.
The reference voltage Vref is applied. The comparator 15 compares the common connection point potential of both resistors with the common connection point potential of both detection coils, and when it determines that the former is smaller than the latter, generates a low-level effective signal and A / D converter 16 Supply to. The A / D converter 16 receives the position signal from the negative terminal of the detection coil 6a, samples and holds the position signal in response to the valid signal, and sends the digital signal corresponding to the held voltage level to the controller 18. Forward.
The controller 18 takes in the transferred digital signal as position data, that is, rotation angle data at a predetermined timing of its internal generation based on the effective signal.

Next, the operation of this circuit will be described with reference to the time chart of FIG. First, the voltage VA applied to the inverting input terminal of the comparator 15 and the voltage VB applied to the non-inverting input terminal are

[0026]

[Equation 8] VA = V1 (10)

[0027]

## EQU9 ## VB = (V1-V2 + Vref) / 2 (11) can be written. Before time t1, the exciting pulse is not generated, and the exciting coil 5 is not excited.
As shown in (b) and (c), the output voltages V1 and V2 of each detection coil are V1 = V2 = 0 and the voltage VA
Is also 0 (that is, VA = V1). At this time, the value of the position signal as shown in FIG. 5D is also 0, so that the voltage VB is the value Vref obtained by dividing the reference voltage Vref by the resistors 32 and 33 having the same resistance value. / 2. Therefore, since VA <VB, the output signal of the comparator 15 exhibits a high level as shown in (e) of FIG.

When the exciting pulse rises from this state at time t1 as shown in FIG. 5A, both detection coils start to generate electromotive force, and at time t2.
When VA = VB in the above equation, the above equations (10) and (1
Based on 1),

[0029]

[Equation 10] V1 + V2 = Vref = constant (12) When the electromotive force of the detection coil further increases, VA
> VB, and VA = VB when the comparator 1
The output signal of 5 will fall to a low level. Therefore, the falling edge of the comparator 15 corresponds to the timing at which it is determined or detected that V1 + V2 = constant.

The A / D converter 16 uses this edge as the sample timing, and at the moment when the output signal of the comparator 15 changes from the high level to the low level or from the low level to the high level, that is, (12 When V1 + V2 = constant, the instantaneous value of V1-V2 is digitally converted into an appropriate or effective position signal value and transferred to the controller 18. The controller 18 takes in the digital output of the A / D converter 16 as position data in response to a falling edge or a rising edge of the effective signal, and performs a calculation according to the above equation (7) to obtain the rotation angle α. Ask.

FIG. 6 shows another example of the position signal generation and excitation control circuit, and the same parts as those in FIG. 4 are designated by the same reference numerals. In FIG. 6, the detection coils 6a, 6
The negative terminal of b is commonly connected. The positive terminal of the detection coil 6 a is connected to the analog input terminal of the A / D converter 16, and the positive terminal of the detection coil 6 b is grounded via the constant voltage source 31. At the positive terminal of the detection coil 6b,
The reference voltage Vref from the constant voltage source 31 is supplied. By connecting both detection coils as described above, a potential of V1 -V2 + Vref, that is, a position signal containing the V1 -V2 component and having the component shifted in level by the reference voltage appears at the positive terminal of the detection coil 6a. . Further, the output voltages V1 and V2 of each detection coil show a negative value with respect to the positive level excitation pulse.

The common connection point of both detection coils is the comparator 15
The non-inverting input terminal of the comparator 15 is connected to the common connection point of the resistors 32 and 33 connected in series between the ground point and the position signal line. Next, the operation of this circuit will be described with reference to the time chart of FIG. First, the voltage VA applied to the inverting input terminal of the comparator 15 and the voltage VB applied to the non-inverting input terminal are

[0033]

[Equation 11] VA = V1 + Vref (20)

[0034]

## EQU12 ## VB = (V1-V2 + Vref) / 2 (21) can be written. Before time t1, the exciting pulse is not generated and the exciting coil 5 is not excited. In this state, as shown in (b) and (c) of FIG.
The output voltages V1 and V2 of each detection coil are V1 = V2 = 0
And the voltage VA is Vref (that is, VA = Vref). At this time, since the value of the position signal as shown in FIG. 7D is also 0, the voltage VB is the value Vref obtained by dividing the reference voltage Vref by the resistors 32 and 33 having the same resistance value. / 2. Therefore, since VA> VB, the output signal of the comparator 15 shows a low level as shown in FIG. 7 (e).

When the exciting pulse rises from this state at time t1 as shown in FIG. 7A, both detection coils start to generate electromotive force, and at time t2.
When VA = VB in the above equation, the above equations (20) and (2
Based on 1),

[0036]

(13) V1 + V2 = -Vref = constant (22) When the electromotive force of the detection coil further increases, VA
<VB and VA = VB when the comparator 1
The output signal of 5 will rise to a high level. Therefore, the rising edge of the comparator 15 corresponds to the timing at which it is determined or detected that V1 + V2 = constant.

The A / D converter 16 uses this rising or falling as sample timing, and when the output signal of the comparator 15 changes from low level to high level or from high level to low level, That is, when the expression (22) is established and V1 + V2 = constant, the instantaneous value of V1 -V2 is digitally converted as an appropriate or effective position signal value and transferred to the controller 18. The controller 18 uses the A / D converter 16
The digital output of 1 is taken as position data in response to the rising edge of the effective signal, and the rotation angle α is obtained by performing the operation according to the above equation (7).

The configuration of the circuit of FIG. 6 is advantageous in the application of the single power supply circuit because the offset of the reference voltage Vref is added to the position signal. That is, when the output range of V1 -V2 is ± 2 [V] and Vref = 2.5 [V], the value of the obtained position signal is 0.5 to 4.5 [V].
Therefore, it can be realized with only a 5 volt power supply. Figure 8
The other example of a position signal generation and excitation control circuit is shown, and the same code | symbol is attached | subjected to the part equivalent to FIG. 4 and FIG. This circuit has improved versatility.

In FIG. 8, the positive terminals of the detection coils 6a and 6b are commonly connected. The negative terminal of the detection coil 6a is connected to the analog signal input terminal of the A / D converter 16, and the negative terminal of the detection coil 6b is a constant voltage source 31b.
Grounded through. An offset voltage VG from the constant voltage source 31b is supplied to the negative terminal of the detection coil 6b. Further, a series connection circuit of resistors 34 and 35 having resistance values RA and RB is formed between the negative terminal of the detection coil 6b and a common connection point of both detection coils, and the resistor 3
The connection point of 4 and 35 is led to the inverting input terminal of the comparator 15. Resistance values RC and R are provided between the position signal line and the ground point.
A series connection circuit of the resistors 32 and 33 having D and the constant voltage source 31a is formed, and the connection point of the resistors 32 and 33 is guided to the non-inverting input terminal of the comparator 15. By such a connection, the potential of V1 -V2 + VG, ie, the position signal, which contains the V1 -V2 component and is level-shifted by the offset voltage, appears at the negative terminal of the detection coil 6a.

The operation of this circuit can be described in the same manner as in FIGS. 4 and 6. The voltages VA and VB applied to the inverting and non-inverting input terminals of the comparator 15 are

[0041]

[Equation 14] VA = VG + V1 · RB / (RA + RB) (30)

[0042]

[Equation 15] VB = Vref + (V1-V2-Vref + VG). (RD / RC + RD) (31) Is. Here, the relationship of each resistance value is

[0043]

If RB / (RA + RB) = 2RD / (RC + RD) (32), if the voltage generated in both detection coils is VA = VB,

[0044]

(17) V1 + V2 = RC / RD.multidot. (Vref-VG) (33). Therefore, by the edge output of the comparator 15 which occurs at the time when VA = VB, V1 +
It can be determined that the value of V2 is the predetermined value shown on the right side of the equation (33).

The A / D converter 16 uses this edge output as a sample timing, and when the edge is generated, that is, when the equation (33) is satisfied and V1 + V2 = predetermined value, V1−V2 is obtained. The instantaneous value of is converted into a proper or effective position signal value by digital conversion, and the controller 1
8 will be transferred. The controller 18 is an A / D
The digital output of the converter 16 is taken in as position data in response to the rising edge of the effective signal, and
The rotation angle α is obtained by performing the calculation in accordance with the above equation (7) and in consideration of the predetermined value.

The sensitivity of the sensor is determined by the value of V1 + V2. That is, as can be seen from equation (7),

[0047]

[Equation 18] V1-V2 = (r / L) .alpha..multidot. (V1 + V2) (40) is derived, and the rate of change of the position signal (V1-V2) is a coefficient of .alpha. (R / L). And (V1 + V2). In other words, under the constant (r / L), (V1
The larger the value of + V2), the larger the value of the position signal (V1-V2) per unit amount of α.

Therefore, the sensitivity of the sensor can be set by the values of RC, RD and Vref based on the equation (33).
VG is also used to set the offset of the position signal. As described above, the circuit of this embodiment in which the sensitivity and the offset can be set can be used in a wide range of systems. Since the circuit of this embodiment handles (V1-V2) as a position signal, it has an advantage that the sensor sensitivity is relatively large. That is, for example, when only V2 is used as the position signal, as can be seen from the above equation (6),

[0049]

V2 = {rconst / (2L)}. Alpha. + Const / 2 (41) is derived. const can be replaced with (V1 + V2) as described above, so if you rewrite it,

[0050]

## EQU20 ## V2 = {r / (2L)}. Alpha..multidot. (V1 + V2) + (V1 + V2) / 2 (42) Here, the coefficient of α is {r / (2L)} and (V1
+ V2), the rate of change of the position signal V2 can be calculated by the equation (4
It can be seen that it is half that in the case of 0). Therefore, (V1
The circuit of each of the above embodiments configured by treating -V2) as a position signal has better sensor sensitivity than the circuit configured by treating V2 as a position signal.

Further, the present invention can be applied to the following differential transformer type sensor and the type of sensor for detecting the relative position of a linearly moving object to be detected. Figure 9
An example in which the excitation control and position signal generation system of FIG. 8 is applied to a magnetic position sensor using a short-circuit coil is shown in FIG.
Thru | or the part equivalent to FIG. 3 and FIG. 8 is attached | subjected the same code | symbol.

In FIG. 9, this magnetic position sensor is
A U-shaped magnetic member 1a having an arcuate portion shaped along an arc drawn around the point a, and a U-shaped magnetic member 1a.
The main body is a fixed magnetic member 1'comprising a linear magnetic member 1b that joins both legs. Fixed magnetic member 1 '
Is homogeneous and has a shape symmetrical to the line la containing the point a. Each of the two legs of the U-shaped magnetic member 1a has
The excitation coils 5a and 5b and the detection coils 6a and 6b are wound. A short-circuit coil 41 is arranged in the arc-shaped portion of the U-shaped magnetic member 1a. The short-circuit coil 41 has a minute gap in the arc-shaped portion so as to be movable along the arc-shaped portion. It is arranged in a roll. Short circuit coil 4
A mechanism 1 (not shown) responds to the displacement of the object to be detected and moves so as to draw an arc centered on the point a. In addition,
The fixed magnetic member 1'may be integrally formed.

The operation of this sensor is based on the same principle as that of the differential transformer. When the exciting coils 5a and 5b are excited to generate a magnetomotive force, the detection coils 6a and 6b generate an electromotive force. At the same time, the short-circuit coil 41 also generates an electromotive force,
A short circuit current flows through the coil and a repulsive force is generated. The repulsive force causes a change in the magnetic flux generated by the exciting coils 5a and 5b.
The magnetic flux passing through 6b is the short-circuit coil 41 on the magnetic path.
Complementarily increases or decreases according to the position of. Therefore, the voltages V1 and V2 generated in the detection coils 6a and 6b are also the short circuit coil 4
It will change complementarily according to the relative position of 1.
Then, from the detected voltages V1 and V2, a position signal and a valid signal are obtained in the same manner as in the above-described embodiments up to FIG.
A value representing the position of the detected object is calculated according to the equation (7).

The relationship between the position of the short-circuit coil 41 and the value of (V1-V2) when (V1 + V2) is constant is shown in FIG. According to this, it is understood that the difference between the output voltages of the detection coils 6a and 6b shows a linear characteristic with respect to the movement amount of the short-circuit coil 41. FIG. 11 shows a cross section of a magnetic position sensor that detects the position of a detection object that moves linearly, and the same reference numerals are given to the same parts as in FIG.

In FIG. 11, the magnetic position sensor has a longitudinal bobbin 50. The bobbin 50 has a hollow inside and a thicker protruding portion 5 near both ends on the outside.
1, 52 has a thin protruding portion 53 approximately at the center between the protruding portions 51, 52. On the bobbin 50, the exciting coil 5a is wound between the one end protruding portion 51 and the central protruding portion 53, and the exciting coil 5b is wound between the central protruding portion 53 and the other end protruding portion 52. . Further, the detection coil 6a is wound on the exciting coil 5a, and the detection coil 6b is wound on the exciting coil 5b. A core 60 is loosely inserted in the hollow portion of the bobbin 50, and the core 60 is a shaft 6
The bobbin 50 is supported by No. 1 and is movable in the bobbin 50 in response to the linear movement of the shaft 61 indicated by the arrow.

The operation of this sensor is also based on the same principle as that of the differential transformer. When the exciting coils 5a and 5b are excited to generate a magnetomotive force, the detection coils 6a and 6b generate an electromotive force. At that time, the voltage V generated in the detection coils 6a and 6b
1, V2 are center lines lb depending on the relative position of the core 60.
Will change in a complementary manner. Then, from the detected voltages V1 and V2, the position signal and the effective signal are obtained in the same manner as in the above-described embodiments up to FIG. 8, and the value representing the position of the detected object is calculated according to the equation (7). It will be. An equivalent circuit obtained by applying the excitation control and position signal generating system of FIG. 8 to this sensor can be written as shown in FIG.

In the position signal generation and excitation control circuit described so far, the position signal is obtained from the terminal of the detection coil 6a, but it goes without saying that the position signal may be obtained from the detection coil 6b. Further, the excitation pulse may be generated at a predetermined repetition period, or may be generated only when necessary to obtain the position of the detected object. Further, not only the first edge generation timing of the effective signal pulse but also the next edge generation timing (see FIGS. 5 and 7).
The position signal may be taken in at time t3).

In the position signal generation and excitation control circuit having such a configuration, the sum of the instantaneous electromotive forces of the detection coils 6a and 6b is a predetermined value from the edge of the effective signal which is the output of the discriminating means (V1 + V2 = The predetermined value) is determined. At this time, the detection level difference (V1 -V2) based on the electromotive forces of the detection coils 6a and 6b is taken in as an effective position signal and transmitted to the signal processing system. As a result, in the signal processing system, the calculation of the above equation (7) is performed, and the accurate rotation angle α of the detected movable member 3 is obtained.
Further, since the rotation angle of the detected movable member 3 is detected by the position signal only when the edge of the effective signal is generated, it is possible to reduce the power consumption.

Further, the position signal generation and excitation control circuit described above has a simple structure in which only one integrated circuit is used as a comparator, so that the number of expensive components to be used can be reduced and not only the manufacturing cost can be reduced. By reducing the number of integrated circuits that are easily affected by changes in the usage environment, reliability will be improved. Further, the comparator used in the position signal generation and excitation control circuit does not have to be composed of the operational amplifier, but can be composed of a device dedicated to the comparator having a lower integration degree than the operational amplifier. Such a dedicated device has a faster response speed than a comparator configured with an operational amplifier,
It is optimal for this position signal generation and excitation control circuit. Further, when such a dedicated device is used as a comparator in this position signal generation and excitation control circuit, it is excellent in handling the output voltage of the detection coil having a small time constant, that is, a small size. Therefore, the overall weight and size of the sensor can be reduced. By thus simplifying the sensor structure or downsizing the entire sensor, a robust and compact magnetic position sensor that can be adapted even under severe operating environments and manufacturing processes is provided. For example, the sensor thus improved can be easily mounted even in the engine room of an automobile.

It should be further noted that although various sensors have been illustrated above, the present invention is not limited to these and can be applied to various other sensors. In short, the present invention has an exciting coil that causes a magnetic flux to flow, and first and second detection coils that generate an electromotive force according to the relative position of the object to be detected by the magnetic flux. It can be applied to a sensor adapted to obtain a signal, and the design modification of each component of the present invention is possible.

[0061]

As described above in detail, according to the magnetic position sensor of the present invention, the detection output levels of the first and second detection coils that generate electromotive force according to the relative position of the object to be detected. A level difference signal is generated according to the difference between
It is determined that the sum of the detection output levels of the first and second detection coils is a predetermined value. Then, in response to this determination, the difference signal is captured as an effective position signal indicating the relative position of the detected object. This makes it possible to prevent erroneous detection and accurately detect the relative position of the detected object.
And it consumes less power. In addition, the simple configuration can contribute to reduction of manufacturing cost and improvement of reliability. Furthermore, the present invention makes it possible to provide a robust and compact magnetic position sensor that is adaptable even under severe operating environments and manufacturing processes.

[Brief description of drawings]

FIG. 1 is a plan view showing a main body structure of a magnetic position sensor according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a plan view of the main body of the sensor according to the embodiment for explaining the operating principle of the magnetic position sensor of FIGS. 1 and 2.

FIG. 4 is a block diagram showing an example of the configuration of a position signal generation and excitation control circuit.

5 is a time chart showing operation waveforms of each part of the circuit of FIG.

FIG. 6 is a block diagram showing another example of the configuration of a position signal generation / excitation control circuit.

7 is a time chart showing operation waveforms of respective parts of the circuit of FIG.

FIG. 8 is a block diagram showing still another example of the configuration of the position signal generation / excitation control circuit.

FIG. 9 is a plan view of a main body of a differential transformer type magnetic position sensor for explaining another application example of the present invention.

10 is a graph showing output characteristics obtained from the magnetic position sensor of FIG.

FIG. 11 is a sectional view of a main body of a differential transformer type magnetic position sensor for explaining still another application example of the present invention.

12 is an equivalent circuit diagram of the sensor of FIG.

[Explanation of symbols]

1a U-shaped magnetic member 1b Linear magnetic member 1c protruding magnetic member 2 rotating shaft 3 Movable magnetic member 4 screws 5,5a, 5b Excitation coil 6a, 6b detection coil 7,8 gap a rotation axis Pa, Pb Closed magnetic circuit 13 Excitation circuit 15 Comparator 16 A / D converter 18 Controller 31, 31a, 31b constant voltage source 32, 33, 34, 35 Electric resistance element 41 Short-circuit coil 50 bobbins 51, 52, 53 Projection 60 cores 61 shaft

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01B 7/00 G01B 7/30 G01D 5/20

Claims (12)

(57) [Claims] 1. A magnetic position sensor for detecting a relative position of a movable object, comprising at least one exciting coil, first and second detecting coils, and interlinking with the exciting coil. Magnetic path forming means for forming a magnetic path through each of the first and second detection coils for passing a magnetic flux that produces an electromotive force according to the relative position of the object to be detected, and the magnetic path forming means according to an excitation command signal. An exciting means for exciting the exciting coil; a difference signal outputting means for outputting a difference signal having a level corresponding to the difference between the detection output levels based on the electromotive forces of the first and second detecting coils; and the first and second Acquisition signal generating means for generating an acquisition signal when the sum of the detection output levels of the detection coils reaches a predetermined value , and the excitation command signal is generated intermittently while the acquisition signal is generated.
Magnetic position sensor, which comprises in response, the control means for taking the difference signal as the position signal, the No.. Wherein said take-signal generating means, said difference signal as one input signal, including a comparator for a signal corresponding to the detected output level of the first detection coil and the other input signal
The comparator compares the two input signals and outputs the first and the second signals.
The detection output level of the second detection coil has reached the predetermined value.
The magnetic position sensor according to claim 1, wherein the magnetic position sensor detects the fact. 3. The excitation means responds to the excitation command signal.
Of the first and second detection coils, wherein the excitation pulse of a specific polarity is supplied to the excitation coil, and the difference signal output means indicates one of the polarities of the electromotive force generated with respect to the excitation pulse . Deriving the difference signal from the other terminal of the first detection coil and deriving the other input signal of the comparator from the common connection point, including connecting means for connecting terminals of the first detection coil to each other at a common connection point. The magnetic position sensor according to claim 2, wherein 4. A differential signal voltage dividing means for dividing the differential signal
4. The magnetic position sensor according to claim 3, further comprising: the comparator using the voltage division output of the difference signal voltage dividing means as one input signal. 5. The windings of the first and second detection coils
Are differentially wound with respect to each other.
4. The magnetic position sensor described in 4. 6. The other terminal of the second detection coil is
The magnetic position sensor according to claim 5, wherein the magnetic position sensor is grounded. 7. The other terminal of the second detection coil
Is a contract characterized by being supplied with a predetermined constant voltage.
The magnetic position sensor according to claim 5. 8. The common connection point and the second detection coil
At least two voltage divider resistors connected to the other terminal
An anti-element, and the voltage division output by the voltage dividing resistance element is
It is characterized in that it is derived as the other input signal of the comparator.
The magnetic position sensor according to claim 5. 9. A divided voltage output by the differential signal voltage dividing means is checked.
A means for bell-shifting, comprising:
The magnetic position sensor according to 6, 7, or 8. 10. The control means samples the acquisition signal.
The position signal is sampled as a pull timing signal.
The digit corresponding to the sample and hold level.
Include an analog-to-digital converter that outputs
The method according to any one of claims 1 to 9, characterized in that
Magnetic position sensor. 11. The magnetic path forming means is the exciting coil.
And fixed magnetism in which the first and second detection coils are wound.
Member and the fixed magnetic portion in response to the displacement of the object to be detected.
On the part between the first and second detection coils on the material
A short piece that is free to move along and is wound around the fixed magnetic member.
And a junction coil.
10. The magnetic position sensor according to any one of 10. 12. The magnetic path forming means is the exciting coil.
And the first and second detection coils are wound.
A hollow bobbin arranged and wound in the axial direction,
In the hollow part of the hollow bobbin,
The hollow bobbin is inserted and movably inserted in the axial direction of the hollow bobbin.
And a movable core that is provided with the movable core.
11. The magnetic type position sensor according to any one of 10.