U.S. patent application number 10/989433 was filed with the patent office on 2006-05-18 for rotation detecting sensor.
This patent application is currently assigned to AISIN SEIKI KABUSHIKI KAISHA. Invention is credited to Glenn Forrest, Takashi Hara, Kazuhiro Kamiya, Toshiyuki Matsuo, Karl Scheller, Kenichi Taguchi, Takayoshi Tsuzuki, Ravi Vig.
Application Number | 20060103377 10/989433 |
Document ID | / |
Family ID | 36318121 |
Filed Date | 2006-05-18 |
United States Patent
Application |
20060103377 |
Kind Code |
A1 |
Hara; Takashi ; et
al. |
May 18, 2006 |
ROTATION DETECTING SENSOR
Abstract
Disclosed is a rotation detecting sensor suitable for use under
a vibration-abundant condition as e.g. a sensor disposed in an
automobile body for detecting rotation of an engine or ABS. The
sensor includes a detecting element for detecting rotation of a
rotary body as a change in a magnetic flux and outputting a signal
and an integrated circuit for processing the amplified signal into
a pulse corresponding to the detected rotation of the rotary body.
The signal processing includes an initialization such as a gain
adjustment for obtaining an appropriate gain for use in the
subsequent process of conversion of the amplified signal to the
pulse. According to this invention, a re-initialization is effected
to obtain a new initial value such as a new gain if the previously
effected initialization is determined inappropriate.
Inventors: |
Hara; Takashi;
(Ichinomiya-shi, JP) ; Kamiya; Kazuhiro;
(Kariya-shi, JP) ; Taguchi; Kenichi; (Toyota-shi,
JP) ; Matsuo; Toshiyuki; (Takahama-shi, JP) ;
Tsuzuki; Takayoshi; (Toyota-shi, JP) ; Forrest;
Glenn; (Bow, NH) ; Scheller; Karl; (Bow,
NH) ; Vig; Ravi; (Bow, NH) |
Correspondence
Address: |
BUCHANAN INGERSOLL PC;(INCLUDING BURNS, DOANE, SWECKER & MATHIS)
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Assignee: |
AISIN SEIKI KABUSHIKI
KAISHA
Kariya-shi
MA
Allegro MicroSystems Inc.
Worcester
|
Family ID: |
36318121 |
Appl. No.: |
10/989433 |
Filed: |
November 17, 2004 |
Current U.S.
Class: |
324/207.25 |
Current CPC
Class: |
G01D 5/2449 20130101;
G01D 5/147 20130101; G01D 18/001 20210501; G01D 5/2448
20130101 |
Class at
Publication: |
324/207.25 |
International
Class: |
G01B 7/30 20060101
G01B007/30 |
Claims
1. A rotation detecting sensor comprising: a detecting element for
detecting rotation of a rotary body as a change in magnetic flux
and outputting an output signal corresponding thereto; initializing
means for effecting an initialization including at least a gain
adjustment for obtaining a desired gain as an initial value based
on variation in the output signal upon lapse of a predetermined
number of rotations of said rotary body; means for amplifying said
output signal together with said gain to provide an amplified
signal; pulse generating means for generating a pulse corresponding
to the rotation of said rotary body based variation in said
amplified signal amplified based on said gain; and initial value
evaluating means for evaluating whether said initial value obtained
by said initialization is appropriate or not and subsequently
causing said initializing means to effect a re-initialization to
obtain a new initial value when said initial value is evaluated
inappropriate, so that said sensor obtains a new amplified signal
based on said new initial value.
2. The rotation detecting sensor according to claim 1, wherein said
sensor has a threshold value for delimiting a pulse generating
timing in response to said amplified signal, and said threshold
value is set by said pulse generating means based on a range of
variation occurred in the amplified signal prior to the pulse
generation.
3. The rotation detecting sensor according to claim 1, wherein said
sensor has a preferred range for said amplified signal, and said
initial value evaluating means evaluates said initial value as
inappropriate and causes said initializing means to effect said
re-initialization when said amplified signal exceeds said preferred
range.
4. The rotation detecting sensor according to claim 1, wherein a
target amplitude is set for said amplified signal, so that said
amplified signal is confined within said target amplitude as a
result of said re-initialization.
5. The rotation detecting sensor according to claim 1, wherein said
gain is updated to the decreasing side in said
re-initialization.
6. The rotation detecting sensor according to claim 2, wherein said
threshold value for delimiting a pulse generating timing includes
upper and lower threshold values which are alternately generated
one after another based on the range of variation occurred in the
amplified signal prior to the pulse generation.
7. The rotation detecting sensor according to claim 2, wherein said
threshold value is set based on a maximum value Vmax, a minimum
value Vmin, a difference Vpp therebetween of said amplified signal
prior to the pulse generation.
8. The rotation detecting sensor according to claim 1, wherein said
initializing means, said amplifying means, said pulse generating
means and said initial value evaluating means are constructed and
incorporated together as a single integrated circuit.
9. The rotation detecting sensor according to claim 1, wherein said
sensor is used for detecting rotation of the rotary body included
in an automobile.
10. A vibrating machine body having the rotation detecting sensor
according to claim 1.
11. The rotation detecting sensor according to claim 2, wherein
said sensor has a preferred range for said amplified signal, and
said initial value evaluating means evaluates said initial value as
inappropriate and causes said initializing means to effect said
re-initialization when said amplified signal exceeds said preferred
range.
12. The rotation detecting sensor according to claim 2, wherein a
target amplitude is set for said amplified signal, so that said
amplified signal is confined within said target amplitude as a
result of said re-initialization.
13. The rotation detecting sensor according to claim 3, wherein a
target amplitude is set for said amplified signal, so that said
amplified signal is confined within said target amplitude as a
result of said re-initialization.
14. The rotation detecting sensor according to claim 2, wherein
said gain is updated to the decreasing side in said
re-initialization.
15. The rotation detecting sensor according to claim 3, wherein
said gain is updated to the decreasing side in said
re-initialization.
16. The rotation detecting sensor according to claim 4, wherein
said gain is updated to the decreasing side in said
re-initialization.
17. The rotation detecting sensor according to claim 6, wherein
said threshold value is set based on a maximum value Vmax, a
minimum value Vmin, a difference Vpp therebetween of said amplified
signal prior to the pulse generation.
18. The rotation detecting sensor according to claim 2, wherein
said initializing means, said amplifying means, said pulse
generating means and said initial value evaluating means are
constructed and incorporated together as a single integrated
circuit.
19. The rotation detecting sensor according to claim 3, wherein
said initializing means, said amplifying means, said pulse
generating means and said initial value evaluating means are
constructed and incorporated together as a single integrated
circuit.
20. The rotation detecting sensor according to claim 4, wherein
said initializing means, said amplifying means, said pulse
generating means and said initial value evaluating means are
constructed and incorporated together as a single integrated
circuit.
21. The rotation detecting sensor according to claim 5, wherein
said initializing means, said amplifying means, said pulse
generating means and said initial value evaluating means are
constructed and incorporated together as a single integrated
circuit.
22. The rotation detecting sensor according to claim 6, wherein
said initializing means, said amplifying means, said pulse
generating means and said initial value evaluating means are
constructed and incorporated together as a single integrated
circuit.
23. The rotation detecting sensor according to claim 7, wherein
said initializing means, said amplifying means, said pulse
generating means and said initial value evaluating means are
constructed and incorporated together as a single integrated
circuit.
24. The rotation detecting sensor according to claim 2, wherein
said sensor is used for detecting rotation of the rotary body
included in an automobile.
25. The rotation detecting sensor according to claim 3, wherein
said sensor is used for detecting rotation of the rotary body
included in an automobile.
26. The rotation detecting sensor according to claim 4, wherein
said sensor is used for detecting rotation of the rotary body
included in an automobile.
27. The rotation detecting sensor according to claim 5, wherein
said sensor is used for detecting rotation of the rotary body
included in an automobile.
28. The rotation detecting sensor according to claim 6, wherein
said sensor is used for detecting rotation of the rotary body
included in an automobile.
29. The rotation detecting sensor according to claim 7, wherein
said sensor is used for detecting rotation of the rotary body
included in an automobile.
30. The rotation detecting sensor according to claim 8, wherein
said sensor is used for detecting rotation of the rotary body
included in an automobile.
31. A vibrating machine body having the rotation detecting sensor
according to claim 2.
32. A vibrating machine body having the rotation detecting sensor
according to claim 3.
33. A vibrating machine body having the rotation detecting sensor
according to claim 4.
34. A vibrating machine body having the rotation detecting sensor
according to claim 5.
35. A vibrating machine body having the rotation detecting sensor
according to claim 6.
36. A vibrating machine body having the rotation detecting sensor
according to claim 7.
37. A vibrating machine body having the rotation detecting sensor
according to claim 8.
38. A vibrating machine body having the rotation detecting sensor
according to claim 9.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a rotation detecting sensor
comprising a detecting element for detecting rotation of a rotary
body as a change in magnetic flux and outputting an output signal
corresponding thereto, initializing means for effecting an
initialization including at least a gain adjustment for obtaining a
desired gain as an initial value based on variation in the output
signal upon lapse of a predetermined number of rotations of the
rotary body, means for amplifying said output signal together with
said gain to provide an amplified signal, and pulse generating
means for generating a pulse corresponding to the rotation of said
rotary body based variation in said amplified signal amplified
based on said gain.
[0003] 2. Related Art
[0004] A rotation detecting sensor of the above-noted type is
designed for detecting change in a magnetic flux which occurs in
association with rotation of a rotary body. More particularly, as
shown in FIG. 4, such rotary body 7 includes a number of teeth 8
along its outer periphery and detecting elements 1 constructed as
Hall elements, magnetoresistive elements or the like are disposed
at operatively appropriate positions relative to the rotary body.
Then, output signals from the detecting elements are used for
determining e.g. a rotational speed, a rotational direction of the
rotary body.
[0005] More particularly, this rotation detecting sensor utilizes
change in the magnetic flux on detecting surfaces of the detecting
elements which change occurs in association with rotation of the
rotary body. The detecting elements detect this magnetic flux
change and convert it into an amplitude-variable electric signal
corresponding thereto. Then, this output signal is inputted to a
logical determining section 4 in which the output signal is e.g.
binarized through an arithmetic logical operation, thus converted
into a pulse corresponding to e.g. the detected rotational speed of
the rotary body.
[0006] The rotation detecting sensor normally comprises the
magnetism detecting elements 1 and a single integrated circuit for
effecting amplification, offset adjustment and pulse
generation.
[0007] According to a recent version of the above type of rotation
detecting sensor now commercially available, in order to extend its
detection distance (i.e. to obtain greater freedom in the choice of
the separating distance between the teeth 8 of the rotary body and
the magnetism detecting elements 1), within a period delimited by
power-ON (energization) of the sensor and occurrence of a
predetermined number of amplitude variations subsequent thereto
(specifically at a predetermined rotational speed of the rotary
body when it is being rotated), the sensor automatically effects a
gain adjustment and/or an offset adjustment on the signal to be
inputted to the logical determining section so that an appropriate
threshold value may become available for use in a logical threshold
processing operation in the logical determining section.
[0008] The gain adjustment is effected for automatically obtaining
such an appropriate gain as will result in a signal having an
appropriate intensity confined within a predetermined range.
Whereas, the offset adjustment is effected for automatically
obtaining such an appropriate offset value as will result in a
signal having an appropriate median amplitude value within a
predetermined range.
[0009] In effecting "initialization" exemplified by the gain
adjustment and the offset adjustment described above, determination
of the timing for effecting this process relies upon the counted
number of cycles of the signal.
[0010] Incidentally, one possible application of such rotation
detecting sensor is its use in a vibrating machine body such as an
automobile body. In such case, the vibration of the machine body
per se such as the automobile body can cause a periodic change in
the separating distance between the rotary body and the detecting
element even when the rotary body is not rotating. Or, a small
periodic rotational vibration can occur in the rotary body due to
the vibration of the machine body These cause a change in the
magnetic flux, so that the sensor may generate an inadvertent
output signal based on such vibration, not on rotation of the
rotary body.
[0011] Then, if the initialization is effected under such condition
in the presence of inadvertent vibration-associated variation (i.e.
vibration noise) in the output signal from the detecting element,
the gain adjustment will result in an excessively large gain, since
the vibration noise is a very small change in the magnetic
flux.
[0012] Thereafter, when the rotary body is actually rotated, the
sensor picks this up as a sufficiently large magnetic flux. Hence,
when this output signal is amplified together with the excessively
large gain previously obtained, the resultant amplified signal will
have a value exceeding a maximum signal processing range of the
integrated circuit. Then, if the pulse generation is effected under
this condition, there will occur such inconvenience as disturbance
in the pulse generation timing.
[0013] As a solution to such problem, it is conceivable to reduce
the sensitivity of the sensor or increase the separating distance
between the rotary body and the detecting element. Obviously, such
solutions are undesirable because of disadvantageous reduction in
the sensor sensitivity.
[0014] Another solution has been proposed which detects or monitors
stop condition of the rotary body (which occurs e.g. when the
automobile body is stopped) continued for a predetermined period
and then effects an initialization again thereafter. With this
solution, however, the initialization is effected when it is not
actually needed. Hence, there is the possibility of disturbance in
the output pulse while the initialization is being effected.
[0015] Still another solution has been proposed (see patent
reference 1: Japanese Patent Application "Kokai" No. 2000-205259,
its claim and FIG. 1) which provides e.g. a "displacement sensor"
separately for detecting the physical vibration (i.e. another
sensor dedicated for detection of vibration, not rotation), so that
the output of the rotation detecting sensor may be appropriately
compensated for based on the vibration detection by this
displacement sensor. This solution is also disadvantageous or not
practical because of significant cost increase expected from the
provision of the additional sensor.
[0016] Next, what happens if such erroneous initialization is
effected in the presence of vibration noise will be described in
greater details with reference to FIGS. 4, 5,6 and 7.
[0017] FIG. 4 is a functional block diagram of a conventional
rotation detecting sensor. FIG. 5 is a flowchart illustrating
initialization and detection operation effected by the rotation
detecting sensor shown in FIG. 4. FIG. 6 is a diagram showing
amplified signal and its associated output pulse waveform (output
pulses) when the initialization is effected based on an amplified
signal from the detecting element resulting from vibration.
[0018] Referring first to FIG. 4, the conventional rotation
detecting sensor includes a pair of detecting elements 1, a
pre-amplifier 2 for amplifying signals from these detecting
elements 1, an offset adjustor 21 for effecting an offset
adjustment on the pre-amplified signals, a main amplifier 20 for
amplifying the signals after the offset adjustment, a logical
determining section 4 for effecting a logical operation on the
resultant signals to convert them into e.g. pulses and an output
section 5 for outputting the pulses.
[0019] In the above, the logical determining section 4 is
responsible for generating at least a number of pulses
corresponding to rotation of the rotary body 7 and optionally
shaping the pulses in accordance with e.g. a rotational direction
of the rotary body, so that such shaped pulses may be
outputted.
[0020] As shown in FIG. 4, when an initialization determining
section 3 has determined that a certain condition such as power-ON
is satisfied, an offset value to be used by the offset adjuster 21
and a gain value to be used by the main amplifier 20 are obtained
in advance by effecting an offset adjustment by the offset adjuster
21 and a gain adjustment by the main amplifier 20.
[0021] Conventionally, the gain adjustment is effected only once at
the time of power-ON which satisfies the initialization determining
condition and the gain value thus obtained is retained as it is to
be used subsequently for e.g. amplification of the output
signal.
[0022] Next, this type of initialization and signal processing
subsequent thereto will be described in details with reference to
the flowchart of FIG. 5.
(Initialization)
[0023] As shown at the upper part of in this flowchart, in response
to power-ON, while serially inputting the output signals from the
detecting element 1, the process effects an offset adjustment and a
gain adjustment (#51-1 and #52) with using the cycle of the signal
as a unit therefor. Then, the process effects a logical
determination for pulse generation (#53-1) and output of generated
pulse (#54-1). This process is continued or repeated until it is
judged (#55) the number of outputted pulses exceeds a predetermined
number of times (e.g. 6-times). With this initialization, an
appropriate gain is obtained.
[0024] Therefore, after this initialization, the resultant gain has
a value which is appropriate for that particular instance in the
process.
(Signal Processing After Initialization)
[0025] Upon completion of the initialization, the process goes on
to a closed loop shown at the lower part of the chart. In this
loop, while inputting new signals, the process obtains amplified
signals with using the gain previously obtained through the
initialization described above and effects a logical determination
and generates and outputs including pulses (#53-2 and #54-2).
[0026] As shown, the offset adjustment is effected in each cycle of
inputting new signals (#51-2).
[0027] The forms of signals processed by the above are illustrated
in the diagram of FIG. 6 which shows time along the horizontal axis
and shows amplified signals (upper row), undesired output pulse
waveform (middle row) and optimal pulse waveform (lower row) all
along the vertical direction.
[0028] Referring first to the horizontal axis representing time, an
area (Area A) shown on the left end and including relatively small
(amplified) signals is an area when element output signals due to
vibration are being inputted. From the center to the right side of
the diagram, there is shown another area (Area B) which is an area
when output signals due to rotation of the rotary body are being
inputted. The figure includes still another area (Area C) which is
included in the Area A at the beginning thereof. This Area C is an
initialization area for effecting the initialization.
[0029] Referring next to the vertical direction of the diagram, the
lowermost row represents the optimal pulse waveform to be obtained
from the element outputs. The middle row represents the undesired
pulse waveform obtained from amplified signals which were
erroneously amplified with using the gain set based on
vibration-associated output variation. The upper row represents
amplified signals which result in or correspond to the undesired
pulse waveform.
[0030] Further, within the upper row, a pair of opposed two dot
chain lines denote or delimit together a maximum signal processing
range of this sensor. Further, one dot chain lines denote threshold
values for pulse generation. In this diagram both the "appropriate
or optimal threshold value" and the "inappropriate threshold value"
are denoted with the one-dot chain lines. The "appropriate
threshold value" is a threshold value which should be employed in
threshold value processing for proper pulse generation even in the
presence of a signal which exceeds the maximum signal processing
range. Whereas, the "inappropriate threshold value" is an
undesirable threshold value which is set relying solely on the
maximum signal processing range.
[0031] As described above, the pulse waveform shown in the middle
row is a pulse waveform obtained by a threshold value processing
based on the inappropriate threshold value. Whereas, the pulse
waveform shown in the lower row is a pulse waveform obtained by a
threshold value processing based on the appropriate threshold
value.
[0032] Hence, in this prior art, as shown, there exists
disagreement between the pulse waveform shown in the lower row and
the pulse waveform shown in the middle row.
[0033] According to the sensor of the type to which the present
invention pertains, the sensor is constructed such that a pulse
generation threshold value for delimiting pulse generation timing
may be automatically set. More particularly, as illustrated in the
pulse generation process in the Area B (rotation) shown in FIG. 6,
this pulse generation timing is set as a timing when an amplified
signal intersects this pulse generation threshold value (one dot
chain line).
[0034] Referring now to FIG. 7, in the process of processing
amplified signals having predetermined unit cycle, the
above-described pulse generation threshold values are set based on
a width or difference Vpp between a maximum value Vmax and a
minimal value Vmin of the single unit cycle of amplified signal.
More particularly, an upper threshold value VthH and a lower
threshold value VthL are set one after another as values which
respectively satisfy: e.g. VthH=Vmax-r*Vpp, VthL=Vmin+r*Vpp, where
r=0.15.
[0035] Namely, these pulse generation threshold values are
automatically set based on range (magnitude) of amplitude variation
occurring in a unit cycle of the amplified signal.
[0036] Referring back to FIG. 6, when the initialization is
effected in the presence of vibration-associated signals detected.
The amplified signals resulting therefrom have a small signal
intensity as shown in the left end of the upper row. Under this
condition, if output signals are inputted one after another and the
gain adjustment as an example of initialization is effected for
obtaining an appropriate gain (i.e. appropriate for such outputs),
because of the weak signal intensity, the resultant gain will
approximate a maximum gain permissible with this sensor,.
[0037] If the vibration continues under the above condition, as
shown, upon lapse of a predetermined number of amplitude variations
thereof, the process automatically effects pulse generation in
accordance with the standard sequence. In this condition, however,
the hysteresis widths of the pulse generation threshold values are
extremely small.
[0038] Thereafter, when the rotary body actually begins to rotate,
because of the excessively large gain obtained previously, the
resultant amplified signals should exceed the maximum signal
processing range of the circuit. Consequently, because the pulse
generation threshold values employed at this stage are
inappropriate, inappropriate pulses will be generated as
exemplified by the relationship between the undesirable pulse
waveform shown in the middle row and the appropriate pulse waveform
shown in the lower row of the FIG. 6.
[0039] In the construction of the present invention, as will be
described later herein, the pulse generation threshold values are
continuously updated and optimized according to the range of the
periodic variation in the amplified detection signals, thereby to
provide an appropriate pulse waveform. In contrast, with the
conventional construction, as shown on the right side in FIG. 6,
the generated pulses have a relatively large pulse width as
determined by the maximum signal processing range.
[0040] As a result, if the sensor detects the rotational speed of
the rotary member and effects the predetermined control scheme in
the manners described above, proper performance cannot be obtained
with this sensor.
[0041] In view of the above-described state of the art, a primary
object of the present invention is to provide an improved rotation
detecting sensor capable of obtaining an appropriate gain through
initialization even when this initialization is effected based on a
change in output signals from a detecting element due to a factor
other than rotation, thereby to generate appropriate signals such
as pulses associated with rotation of a rotary member, so that the
sensor can provide highly reliable rotation information.
SUMMARY OF THE INVENTION
[0042] According to the present invention, there is provided a
rotation detecting sensor comprising: a detecting element for
detecting rotation of a rotary body as a change in magnetic flux
and outputting an output signal corresponding thereto, initializing
means for effecting an initialization including at least a gain
adjustment for obtaining a desired gain as an initial value based
on variation in the output signal upon lapse of a predetermined
number of rotations of said rotary body, means for amplifying said
output signal together with said gain to provide an amplified
signal, and pulse generating means for generating a pulse
corresponding to the rotation of said rotary body based variation
in said amplified signal amplified based on said gain; and initial
value evaluating means for evaluating whether said initial value
obtained by said initialization is appropriate or not and
subsequently causing said initializing means to effect a
re-initialization to obtain a new initial value when said initial
value is evaluated inappropriate, so that said sensor obtains a new
amplified signal based on said new initial value.
[0043] According to the rotation detecting sensor having the above
described construction, the initial value evaluating means
evaluates whether an initial value obtained by the initialization
is appropriate or not. And, if this value is evaluated as
inappropriate, an initialization is effected again. As a result,
the sensor obtains at least a gain which accurately reflects the
rotation of the rotary body and subsequently generates pulses with
less disturbance in the pulse generation timing by applying the
gain.
[0044] Therefore, even if this sensor is employed as a rotation
detecting sensor in a vibrating machine, it is possible to avoid
generation of inappropriate pulses under the influence of initial
vibration of the machine.
[0045] Preferably, said sensor has a threshold value for delimiting
a pulse generating timing in response to said amplified signal, and
said threshold value is set by said pulse generating means based on
a range of variation occurred in the amplified signal prior to the
pulse generation.
[0046] With this construction, for generating a predetermined pulse
waveform associated with rotary body rotation, the sensor can
effect the threshold processing therefor in such a manner as
suitable for the detection condition of the rotation detecting
element.
[0047] Preferably, said sensor has a preferred range for said
amplified signal, and said initial value evaluating means evaluates
said initial value as inappropriate and causes said initializing
means to effect said re-initialization when said amplified signal
exceeds said preferred range.
[0048] With the conventional rotation detecting sensor of this type
in general, as described hereinbefore, the sensor includes, on the
side of the output of the magnetism detecting element, a circuit
for effecting a predetermined logical determination on the output
from the detecting element to generate a pulse corresponding
thereto or for obtaining optionally a shaped pulse corresponding
thereto. Such circuit has a fixed maximum signal processing
range.
[0049] Therefore, if a predetermined preferred range is set for
such maximum signal processing range and the re-initialization is
effected when the amplified signal exceeds this preferred range,
the resultant amplified signal from which the pulse is to be
generated can always be confined within the preferred range
suitable for the subsequent signal processing.
[0050] Preferably, if the amplified signal has exceeded the
preferred range for a predetermined number of times in a row, the
signal is determined as being associated with vibration, then, the
re-initialization is effected.
[0051] Still preferably, a target amplitude is set for said
amplified signal, so that said amplified signal is confined within
said target amplitude as a result of said re-initialization.
[0052] Further, as described hereinbefore, when the sensor picks up
small vibration of a vibrating machine body as a noise and then
sets a gain appropriate therefor, thus set gain will be excessively
large. Therefore, the gain may be updated to the decreasing side in
the re-initialization.
[0053] This quickens the process to obtain a really appropriate
gain during the re-initialization when this is needed.
[0054] Further, the re-initialization can be effected at the timing
of start of rotation of the rotary body. Hence, optimum
initialization can be effected with a minimum number of rotation of
the rotary body.
[0055] Still preferably, said threshold value for delimiting a
pulse generating timing includes upper and lower threshold values
which are alternately generated one after another based on the
range of variation occurred in the amplified signal prior to the
pulse generation.
[0056] With this, the pulse-timing delimiting threshold values can
be reliably obtained in the alternate and serial manner based on a
certain present condition of the amplified signal.
[0057] Preferably, said threshold value is set based on a maximum
value Vmax, a minimum value Vmin a difference Vpp therebetween of
said amplified signal prior to the pulse generation.
[0058] With this, the pulse generation can be readily carried out
by utilizing the readily obtainable values characterizing the
amplified signal (i.e. the maximum value Vmax, the minimum value
Vmin and a difference Vpp therebetween).
[0059] Advantageously, said initializing means, said amplifying
means, said pulse generating means and said initial value
evaluating means are constructed and incorporated together as a
single integrated circuit.
[0060] The rotation detecting sensor of the invention can be used
in great number and in numerous applications. Hence, the
construction of the various means in the form of a single
integrated circuit is advantageous for mass production, stability
of performance as well as readiness of replacement of the sensor
when needed.
[0061] As described above, according to the rotation detecting
sensor of this invention having the constructions described, when
this sensor is employed in a vibrating machine body such as an
automobile body as a rotation detecting sensor for automatic
transmission or ABS (anti-lock braking system) thereof, the sensor
is still capable of effecting an optimal pulse waveform
generating/shaping operation through the re-initialization
regardless whether the change in magnetic flux is due to vibration
of the rotary body or to its rotation.
[0062] Further and other features and aspects of the present
invention will become apparent upon reading the following
description of preferred embodiments thereof with reference to the
accompanying drawings; in which,
[0063] FIG. 1 is a functional block diagram of a rotation detecting
sensor according to the present invention, the sensor being
designed for effecting a re-initialization,
[0064] FIG. 2 is a flowchart illustrating operating of the
invention's sensor which effects a re-initialization,
[0065] FIG. 3 is a diagram showing sensor operation when a
re-initialization is effected,
[0066] FIG. 4 is a functional block diagram of a conventional
rotation detecting sensor,
[0067] FIG. 5 is a flowchart illustrating operation of the
conventional sensor which effects an automatic initialization
function,
[0068] FIG. 6 is a diagram illustrating showing the operation of
the conventional sensor, illustrating its problem in particular,
and
[0069] FIG. 7 is a diagram illustrating setting of threshold values
for delimiting a pulse generating timing.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0070] Next, preferred embodiments of the invention will be
described with reference to FIGS. 1, 2 and 3 in correspondence with
FIGS. 4, 5 and 6 for comparison, respectively.
[0071] FIG. 1 is a functional block diagram of a rotation detecting
sensor relating to the present invention. This sensor is designed
for effecting a re-initialization when needed. FIG. 2 is a
flowchart illustrating initialization, re-initialization and
detection operations effected by the rotation detecting sensor
shown in FIG. 1.
[0072] FIG. 3 is a view corresponding to FIG. 6 described
hereinbefore and showing amplified signals, output pulse waveform
obtained by the rotation detecting sensor of the invention capable
of re-initialization and appropriate pulse waveform.
[0073] Describing with reference to FIG. 4 for comparison, like the
conventional rotation detecting sensor, the rotation detecting
sensor according to the present invention includes a pair of
detecting elements 1. Outputs (element outputs) from these elements
1 are subjected to an offset adjustment by an offset adjustor 21
and the resultant signals are then amplified by a main amplifier 20
and sent to a logical determining section 4 to be subjected to a
predetermined logical determination therein to be converted into
pulse signals, which are then transmitted an output section 5
downstream. These final signals include at least pulses.
[0074] At the logical determining section 4, as described
hereinbefore in connection with the prior art, a threshold setting
operation is automatically effected for pulse generation and at
least pulses are generated in correspondence with rotation of a
rotary body 7. Further, at this section, a pulse shaping operation
can optionally be effected in accordance with e.g. the rotational
direction of the rotary body 7. So that, this section can output
such shaped pulses also.
[0075] In the case of the conventional construction described
hereinbefore, the construction includes only the initialization
determining section 3 for effecting initialization only once. In
the case of the construction of the present invention, there is
further provided a re-initialization determining section 30 for
effecting a re-initialization if necessary. More particularly, in
this re-initialization too, a gain adjustment is effected so as to
obtain a new gain value accurately reflecting the actual condition
of the rotary body. In this re-initialization, the gain is updated
to the decreasing side.
[0076] FIG. 2 is a flowchart corresponding to the flowchart shown
in FIG. 5. The flowchart of FIG. 2 includes steps #21-25 as well as
additional steps #30, 31 which latter steps are provided in
connection with the essential feature of the present invention.
[Initialization]
[0077] In this flow, upon power-ON, while inputting output signals
one after another, the process effects an offset adjustment (#21-1)
and a gain adjustment (#22-1), both using amplitude variation in
the output signals as a unit therefor. Then, at the logical
determining section 4, the process effects a logical determination
(#23-1) for pulse generation and outputs the generated pulses
(#24-1). This initialization process is continued until it is
judged (#25) that the number of pulses exceeds a predetermined
number of times (e.g. 6 times). This initialization process is
substantially identical to that conventionally effected.
[Signal Processing After Initialization]
[0078] Upon completion of this initialization (or re-initialization
described later), the process goes to a flow shown at the
lower-right part in FIG. 2.
[0079] In this, while serially inputting new output signals, the
process an offset operation (#21-2) again. At this stage, however,
the process processes signals which were amplified by using the
gain previously obtained as it is. Thereafter, the process effects
an initialization determination at a re-initialization determining
section 30 (initial value evaluating means) (#30, #31), at which if
it is determined that an initialization is needed, the process goes
back to the above-described initialization process to effect an
initialization again. If, on the other hand, it is determined that
no initialization is needed, the process just moves to the logical
determination step to generate pulses and output the generated
pulses (#23-2, and #24-2). This process is repeated by a
predetermined timing.
[0080] The process for effecting the above described steps is
illustrated in the diagram of FIG. 3 which corresponds to FIG.
6.
[0081] FIG. 3 employs similar principle of diagrammatical
illustration to that employed in FIG. 6. In addition, however, this
FIG. 3 shows re-initialization determining threshold values
(actually consisting of an upper threshold value H and a lower
threshold value L for the determination of re-initialization)
denoted with narrow solid lines, which threshold values are used by
the re-initialization determining section 30. FIG. 3 further shows
a gain-setting target amplitude and a re-initialization area (Area
D) where the re-initialization is effected as needed.
[0082] In this diagrammatical representation, any disagreement or
displacement between the pulse waveform shown in the middle row
relative to the pulse waveform shown in the lower row would be a
problem. In this respect, in FIG. 3, it is observed that there is
no such displacement at all after the start of rotation of the
rotary body.
[0083] The pulse generating scheme effected at the logical
determining section 4 is identical per se to that described
hereinbefore for the prior art with reference to FIGS. 6 and 7.
Namely, the pulse generating threshold values are continuously,
updated and set, so that the pulse generating timing is set by the
timing when the amplified signal passes either pulse generating
threshold value.
[Operation Under Vibration]
[0084] In comparison with the construction shown in FIG. 6, when
the rotary body is not rotated and the signals from the detecting
elements due to certain vibration alone, the construction of the
present invention functions similarly to the prior art. Hence, an
excessive gain (substantially the maximum gain) will be set before
rotation of the rotary body.
[0085] [Operation Under Rotation]
[0086] Therefore, when the rotary body actually begins to rotate,
the resultant amplified signals will be excessively large exceeding
the maximum signal processing range. However, this excess condition
is detected as intercepts of the upper and lower re-initialization
determining threshold values (H, L) by the amplified signals (shown
at "intercept counts 1, 2 3" denoted with white circles). Then,
when the number of these intercepts (intercept counts) exceeds a
predetermined number (3 (three) in the case of the illustrated
example), the re-initialization determining section 30 determines
that the previously effected initialization was inappropriate,
hence, that a re-initialization is needed. This determination is
the determination effected by the re-initialization determining
section 30 referred to herein as "initial value evaluating
means".
[0087] In the illustrated case, in the same manner as the first
initialization, the re-initialization is effected for three cycles
shown as Area D. In this re-initialization stage, the gain is
automatically and continuously adjusted to the decreasing side
toward the gain setting target amplitude, so that the amplified
signal too is progressively decreased in its signal intensity and
the threshold value width (the width between the upper and lower
thresholds) for the pulse generation too is progressively converged
toward the median value.
[0088] Therefore, as shown on the right end in the figure, there is
achieved good agreement between the actual pulse waveform and an
ideal or optimum pulse waveform for pulse signal shown in the lower
row.
Other Embodiment
[0089] In the foregoing embodiment, in the determination of the
necessity of the re-initialization, a re-initialization is effected
if the re-initialization determining threshold value (e.g.
vibration noise determining threshold value) has been exceeded by a
predetermined number of times (specifically, three times in the
illustrated example). For this determination, it is also possible
to set upper and lower limits for this type of determining
threshold value and if the signal exceeds either one of them by a
predetermined number of times in a row or has exceeded it by the
predetermined number of times in total or exceeds the upper limit
and the lower limit alternately in a row by a predetermined number
of times, a re-initialization can be effected as determined
needed.
[0090] The rotation detecting sensor of the invention can be used
advantageously as a rotation detecting sensor to be installed in a
vibration abundant place, e.g. as a rotation detecting sensor for
an automatic transmission or ABS in an automobile body.
[0091] The present invention may be embodied in another manner than
those described above. Hence, the disclosed embodiments are not
intended to be limiting the scope of the invention, but various
modifications thereof will be apparent for those skilled in the art
without departing from the essential elements thereof set forth in
the appended claims and such modifications too are to be understood
as included within the scope of the invention.
* * * * *