JP3349053B2 - Window glass pinch detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting the presence or absence of a window glass, and more particularly, to detecting an object or the like being pinched on a closed window glass and releasing the pinched object from the pinched state. The present invention relates to a device for detecting the presence / absence of holding a window glass.

[0002]

2. Description of the Related Art Conventionally, in a power window device of an automobile, a window glass is opened and closed by operating a window opening / closing switch. In detail, for example, when the window is fully open, when the window close switch is operated,
Power is supplied to a motor that moves the window glass up and down, and the window glass is rotated in the closing direction.
Then, when the glass is completely closed, the power supply to the motor is stopped, and the closing operation of the glass is completed. This power supply is stopped, for example, when the glass is closed, the load of the motor is increased, and when the load current becomes a predetermined value or more, it is determined that the glass is closed, and the power supply is stopped. I have.

[0003] In addition, this type of power window device includes:
Some are provided with a pinch prevention mechanism. This pinch prevention mechanism detects when the window glass is performing a closing operation, for example, when an object is caught in the glass and a further closing operation becomes impossible, and detects that the glass is caught and removes the glass. The object is opened in the opening direction to release a pinched object.

There is a pulse detection method for detecting that the object or the like has been caught (hereinafter, detection of the presence or absence of being caught). This pulse detection method is performed by detecting a rotation speed of a motor that opens and closes a window glass and generating a pulse signal having a period proportional to the rotation speed. Generally, when the rotation speed of the motor is high, the pulse period is short, and when it is low, the pulse period is long. Utilizing the fluctuation of the pulse period, the detection of the presence / absence of pinching is performed as follows.

Now, when the motor is performing a closing operation in a direction to close the window glass at a constant rotation speed, a pulse cycle outputted at each time becomes constant. Then, the pulse period T0 of the currently output actual pulse and the pulse periods T1 to TN-1 of each pulse up to N-1 before the currently output pulse are summed, and the total value is expressed by N Divide by.

That is, the average pulse period P0 (= (T0 +
T1 +... + TN-1) / N). Therefore, if the pulse period is always constant, the average pulse period P0 is also constant.

The average pulse period P0 obtained at each time is
Is a threshold value POS (= a × P0) as a basic threshold value obtained by multiplying a coefficient by a predetermined coefficient with respect to the coefficient a.
1). The threshold value POS is a reference value for determining whether or not the sheet is held at each time.

The pulse period T obtained at that time is
A period difference value △ S (= T0−P0) between 0 and an average pulse period P0 including the pulse period T0 is obtained. The obtained period difference value ΔS and the threshold value POS obtained at that time
Compare with Then, when the period difference value ΔS at that time is larger than the threshold value POS at that time, it is determined that something has been caught. Conversely, when the period difference value ΔS at that time is equal to or smaller than the threshold value POS at that time, it is determined that nothing is sandwiched.

[0009]

However, when the pinch detection is performed by changing the pulse frequency as described above, the impact of the opening / closing of the door during the upward movement of the window glass or the impact (vibration generated when traveling on a rough road) is obtained. For example, when the pulse cycle is changed, it is erroneously detected that the window glass is pinched, and the window glass may be turned over and fall.

An object of the present invention is to correct a pulse period variation parameter when a pulse having a short pulse period is generated so as not to detect pinching when the pulse period fluctuates due to factors such as vibration and shock. Accordingly, it is an object of the present invention to provide an apparatus for detecting the presence / absence of pinching of window glass, which can suppress erroneous detection of pinching.

[0011]

In order to solve the above-mentioned problems, a first aspect of the present invention is to provide a driving circuit for supplying a power supply voltage to a motor for driving a window glass to open and close, and a driving circuit for controlling a rotation speed of the motor. Input the pulse signal of the pulse period, and find the pulse period of the pulse signal at each time,
A period difference value calculating unit that calculates a period difference value between the average pulse period and the pulse period at that time, and a period difference value calculating unit that obtains a period difference value between the average pulse period and the pulse period at that time. By calculating the difference value at that time, a difference sum calculating means for calculating a difference sum that is a sum of a plurality of predetermined difference values in the past, and comparing the difference sum with a predetermined threshold value, A first determining means for determining whether or not an object is pinched by the glass during the closing operation of the window glass, and inverting the motor through the drive circuit when the pinch is being pinched; In the presence / absence detection device, when the period difference value at that time is equal to or less than a predetermined value, the gist is a window glass sandwiching presence / absence detection device including a correction unit that corrects the difference sum.

According to a second aspect of the present invention, in the first aspect, the correction means includes a difference between the current difference value calculated by the periodic difference value calculation means and a predetermined past value to be calculated by the difference sum calculation means. The gist of the present invention is a window glass sandwiching presence / absence detection device that replaces only a value exceeding the predetermined value among a plurality of difference values with a predetermined value.

According to a third aspect of the present invention, in the first aspect, a second determining means for determining whether the period difference value is equal to or less than a predetermined value.
And the duration when the period difference value is
The correction means includes a counting means for counting the period difference value.
When the count changes from below a predetermined value to above a predetermined value,
Difference for a duration equal to the duration counted by the
In order for the summation calculation means to calculate,
The difference value at that time calculated by
Out of the difference values, only those exceeding the predetermined value
Window glass that is replaced with a fixed value
The gist is a non-detection device .

(Operation) According to the first aspect of the present invention, the period difference value calculating means inputs a pulse signal having a pulse period corresponding to the rotation speed of the motor, obtains a pulse period of the pulse signal at each time, and determines in advance the pulse period. An average pulse period is determined from the determined plurality of past pulse periods, and a period difference value is determined from the average pulse period and the pulse period at that time.

The difference sum calculating means calculates a difference sum which is a sum of the difference value at that time calculated by the periodic difference value calculating means and a plurality of predetermined past difference values. First
The determination means determines whether or not an object has been pinched by the window glass during the closing operation by comparing the sum of the differences with a predetermined threshold value. , The motor is driven in reverse.

The correction means corrects the sum of the differences when the period difference value at that time is equal to or less than a predetermined value. As a result, the first
Will determine whether or not an object has been pinched by the window glass during the closing operation based on the corrected difference sum and the periodic difference value at that time.

According to the second aspect of the present invention, the correction means includes a difference value calculated by the period difference value calculation means and a plurality of predetermined past values, which are calculated by the difference sum calculation means. Only the difference value that exceeds the predetermined value is replaced with the predetermined value.

According to the third aspect of the present invention, the second determination means determines whether the period difference value is equal to or less than a predetermined value. Then , the counting means performs a relay when the period difference value is equal to or less than a predetermined value.
Count the duration. The correction means determines that the period difference value is predetermined.
When the value changes from below the specified value to the specified value, the counting
The sum of the differences for a time corresponding to the duration counted by the stage
Calculated by the period difference value calculation means for calculation by the calculation means.
The difference value at that time issued and a plurality of
Of the difference values, only those exceeding the predetermined value are set to the predetermined value.
Replace with

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment in which the present invention is embodied in a power window device for a side door of a vehicle will be described below with reference to FIGS. 1 to 5 and FIG.

FIG. 1 shows an electrical configuration of the power window device. In FIG. 1, a controller 21 constituting the electronic control unit includes a calculation unit 22 and a storage unit 23. The calculation unit 23 performs various calculations. The storage unit includes a rewritable memory unit (RAM) for storing the operation result of the operation unit 23 and detection signals from various sensors described later, and a read-only memory unit (ROM) for storing various control programs. Have.
The controller 21 constitutes a period difference value calculation unit, a difference sum calculation unit, first and second determination units, a count unit, and a correction unit.

The up switch 24, down switch 25, and auto switch 26 are provided on the inner surface of the door. The raising switch 24 is a switch for raising the window glass, and the lowering switch 25 is for lowering the window glass. Both switches 24 and 25 are turned on and off by selectively switching the swing type power window switch.
That is, when the power window switch is swung to one side, the up switch 24 is turned on, and when the power window switch is swung to the other side, the down switch 25 is turned on.
Then, both switches 24 and 25 are turned on only when the occupant is operating, and return to the neutral position when the operating force is released, and both switches 24 and 25 are turned off.

The auto switch 26 is turned on / off by selectively switching and pressing a swing type power window switch. Then, even when the pressing operation of the occupant is released, the motor M is rotationally driven based on the operation of the auto switch 26 to the open side or the closed side under the control of the controller 21.

These switches 24, 25 and 26 are connected to the controller 21 and input an on / off signal to the controller 21. The motor M is driven using the battery B of the vehicle as a driving power source.
7 is connected to the battery B. Switching circuit 27
Is composed of a relay circuit. And battery B
The switching of the switching circuit 27 causes the motor 15 to rotate forward, reverse, or stop. That is, the switching circuit 2
Reference numeral 7 is connected to the controller 21 so that a forward rotation control signal, a reverse rotation control signal, and a stop signal from the controller 21 are input. Then, the switching circuit 27 switches the circuit based on the forward rotation control signal, and drives the motor M forward. The switching circuit 27 switches to reverse the circuit based on the reverse control signal from the controller 21.
The motor M is driven to rotate in the reverse direction. Further, the controller 21
The switching circuit 27 cuts off the connection of the motor M to the battery B based on the stop signal from. The switching circuit 27 corresponds to the driving circuit of the present invention.

The pulse sensor PS inputs a pulse signal corresponding to the rotation speed of the motor M to the controller 21 during the control of the motor M. The controller 21 calculates the average value Pa of the pulse width at each time based on the pulse corresponding to the number of rotations of the motor 15 per unit time, and stores the average value Pa in the RAM of the storage unit 23. The pulse sensor PS includes:
Regardless of the operation of the up switch 24, the down switch 25, or the auto switch 26, the pulse sensor is operated full time, that is, constantly.
The pulse sensor PS constitutes foreign matter trapping detection means.

The limit switch LS is electrically connected to the controller 21. When the window glass is at the fully closed position, the limit switch LS is turned on by the window glass and inputs an ON signal to the controller 21. The controller 21 inputs a stop signal to the switching circuit 27 to stop the forward rotation of the motor M based on the ON signal from the limit switch LS.

Now, the operation of the power window device configured as described above will be described. FIG.
Is a pinch determination control routine of the power window device executed by the control unit. This control routine is started when the window glass of the power window device starts to be raised, and thereafter is executed at predetermined time intervals while the window glass is being raised. It should be noted that various flags, timers, counters, and the like used in this routine are initialized only when this routine is first executed when the window glass is raised.

In step 10, the controller 21
Reads the pulse width Pw (= Pn-1 + Pn) based on the pulse signal S from the pulse sensor PS (FIG. 2).
reference). Next, in step 20, the average pulse cycle Pa of the n pulses obtained up to the previous control cycle is calculated by the following equation.

Pa = 2 (P0 + P1 + P2 +... + Pn-
2) / (n-1) In the next step 30, a period difference value (hereinafter referred to as a difference value) ΔPa is calculated by the following equation.

ΔPa = Pw−Pa Step 20 constitutes an average pulse period calculating means, and steps 20 and 30 constitute a period difference value calculating means.

In the subsequent step 40, the obtained difference value ΔPa is stored as a m-th difference value in a predetermined area of the RAM in the storage unit 23. Note that, in the previous control cycle, the m-th difference is (m
-1) Update as number.

In the next step 50, it is determined whether or not the ΔPa is smaller than a predetermined value α (≦ 0) as a predetermined value. If ΔPa is larger than the determination value α, the process proceeds to step 70. If ΔPa is equal to or smaller than the determination value α,
Move to step 60. The determination value α is obtained by an experiment or a test, and is stored in the ROM of the storage unit 23 in advance. The determination in step 50 is performed to determine whether the pulse period (pulse width) has become short due to vibration, impact, or the like.

When the process proceeds to step 60, among the (m + 1) difference values ΔPax (x = 0, 1,..., M) stored in the RAM up to the current control cycle, ΔPax>
Only the value of α is replaced with the value of α of the judgment value.

Steps 50 and 60 constitute the correcting means of the present invention. Step 60 or Step 5
When the process proceeds from step 0 to step 70, in step 70, the difference sum Ps is calculated by the following equation.

[0034]

(Equation 1)

Step 70 constitutes a difference sum calculating means. In the following step 80, the difference sum Ps
Is greater than the “threshold value” Psth.
As shown in FIG. 3, when the average pulse period Pa is short, the “threshold value” Psth indicates a constant value when the average pulse period Pa is short, and is a function that increases as the average pulse period Pa increases (increases). It is stored in the ROM of the storage unit 23. In step 80, the difference sum Ps is set to the “threshold value” Psth
If it is smaller, the routine goes to step 90, where the motor M
The normal rotation flag for outputting the normal rotation control signal is set, and this control routine is temporarily ended. If the difference sum Ps is equal to or greater than the "threshold value" Psth in step 80, the process proceeds to step 100 to reset a normal rotation flag for outputting a reverse rotation control signal to the motor M, and to execute this control routine. Is temporarily terminated.

In another control routine executed at the predetermined timing, the controller 21 determines the state of the normal rotation flag. If the normal rotation flag is set, the controller 21 controls the switching circuit 27 to perform normal rotation. The control signal is input, the motor M is driven forward, and the glass window is driven upward. When the normal rotation flag is reset, a reverse rotation control signal is input to the switching circuit 27, the circuit is switched and connected, the motor M is driven in reverse, and the window glass is driven down.

When the limit switch LS is turned on by the window glass when the window glass is raised and the window glass is at the fully closed position, an ON signal is input to the controller 21. The controller 21 inputs a stop signal to the switching circuit 27 based on the ON signal. As a result, the forward drive of the motor M is stopped.

(A) In this embodiment, when a foreign substance is caught by the rising window glass, the pulse period Pa increases and the difference value ΔPa also increases. Therefore, in the pinch determination control routine,
In step 50, the value is larger than the determination value α, so that the determination is “NO” in that step, and in step 70, the difference sum Ps is calculated as an uncorrected difference sum. Therefore, in the subsequent step 80, the value becomes larger than the "threshold value" Psth.
If it is 0, the determination is “NO”, and the normal rotation flag is reset in step 100. As a result, the window glass is driven to rotate in the reverse direction, and the entrapment is eliminated.

(B) Further, according to this embodiment, since the pulse period fluctuates due to vibration and impact, it is determined in step 50 whether the difference value ΔPa is smaller than the judgment value α. , It is determined whether or not the pulse period (pulse width) has become short.

If the difference value ΔPa is larger than the judgment value α, it is assumed that there is no change in the pulse period due to vibration or impact, and the process directly jumps to step 70, where the (m + 1) difference values ΔPax (x = 0,1, ...
, M) to calculate the difference sum Ps.
As a result, the difference sum Ps is not corrected, and the comparison with the “threshold value” Psth is performed in step 80.

If the difference value ΔPa is equal to or smaller than the determination value α, it is determined that there is a change in the pulse cycle due to vibration and impact, and in step 60, the RAM is not changed until the current control cycle.
(M + 1) difference values ΔPax (x = 0,
1,..., M), only those of ΔPax> α were replaced with α of the determination value. As a result, step 70
Then, the difference sum Ps is corrected and calculated based on the (m + 1) difference values ΔPax including the replaced difference value.
Then, in step 80, the corrected difference sum P
s is compared with the “threshold value” Psth.

Referring to FIG. 4, a case where the above-mentioned difference sum Ps is corrected and a case where there is no correction will be described. Referring to FIG. As a result, the value of Ps with correction becomes “threshold value” Pst
Exceeding h is suppressed, and thus false detection is suppressed.

FIG. 4 is an explanatory diagram for explaining pinch detection when α = 0 and the period difference value changes due to vibration or the like. The vertical axis indicates each parameter (Psth, ΔPa, Ps) is the time (ms), and the horizontal axis is the elapsed time (t).

(C) FIG. 5 shows a result obtained by actually measuring the present embodiment by simulation when α = 0, and as shown in FIG.
In the case of s, since the value is lower than Ps without correction, Ps with correction does not exceed the “threshold value” Psth. Therefore, erroneous detection is suppressed. FIG.
Is an explanatory diagram for explaining pinch detection when the period difference value changes due to vibration or the like. The vertical axis represents time (ms) of each parameter (Psth, ΔPa, Ps), and the horizontal axis represents elapsed time (t). ).

(D) In the present embodiment, for example,
ΔPa fluctuates even when vibrations and shocks occur continuously, such as when driving on a rough road. Therefore, even when vibration or impact occurs continuously, erroneous detection can be effectively suppressed.

(Second Embodiment) Next, a second embodiment of the present invention will be described.
The embodiment will be described with reference to FIGS. 6 and 8. FIG. In this embodiment, the electrical configuration is the same as in the first embodiment.

FIG. 8 shows a part of the pinch determination control routine of the power window device executed by the controller 21. In the pinch determination control routine of the first embodiment, the steps 50 and 70 are performed. Since the steps are different, and the other steps are the same as those of the pinching determination control routine of the first embodiment, the description thereof is omitted.

Note that this control routine is started when the window glass of the power window device starts to be raised, and is executed every predetermined time while the window glass is being raised.

In step 50, ΔPa is equal to the judgment value α.
If so, the process proceeds to step 51. On the other hand, if ΔPa is larger than the determination value α, the process proceeds to step 54. When the process proceeds to step 51, the history flag F is set to “1”.
Is set. The history flag F is a flag for determining whether or not ΔPa has become equal to or smaller than the determination value α in the past. First, when the pinch determination control routine is executed, the history flag F is reset to “0”.
Is determined to be “NO”, and steps 50 to 5
Move to 2. Then, in step 52, the history flag F is set to "1", and the routine goes to step 53.
When the process proceeds from step 50 to step 51 in the pinching determination control routine in the subsequent control cycle, the history flag F is set to “1”.
1 is determined as "YES", and the routine jumps to step 53.

When the process proceeds from step 51 or 52 to step 53, the timer count t1 is incremented by one in step 53, and the process proceeds to step 70. Therefore, in step 50, ΔPa is equal to the determination value α.
If it is below, the timer counter t1 is always incremented by one.

Further, from step 50 to step 54
In step 54, it is determined whether or not the history flag F is set to "1".
If the history flag F is reset to “0” instead of “1”, since ΔPa exceeds the determination value α, it is determined that there is no change due to vibration or impact in the past and “NO” is determined. Move to step 70.

If the history flag F is set to "1" in step 54, it means that there has been a change due to vibration or impact in the past, and ΔPa is less than or equal to the judgment value α. , "YES", and the routine goes to step 55.

In step 55, it is determined whether or not the timer counter t1 is 0. Timer counter t1
If There Re only a zero, at step 56, the timer counter t1 is decremented by one, the process proceeds to step 57. In step 57, the (m + 1) difference values ΔPax (x = 0, 1, 1) stored in the RAM until the current control cycle are reached.
.., M), only those of ΔPax> α are replaced with the determination value α, and the process proceeds to step 70.

If the timer counter t1 is 0 in step 55, the history flag F is reset to "0" in step 58, and the routine goes to step 70. In this second embodiment, step 50 comprises:
The second determining means constitutes, and the steps 50 and 57 constitute the correcting means.

(E) The second embodiment configured as described above has the advantage (d) similar to the first embodiment. (F) Further, in this embodiment, when the process proceeds from step 51 or 52 to step 53, the timer count t1 is incremented by one in step 53, and the process proceeds to step 70. Therefore, in step 50, if ΔPa is equal to or smaller than the determination value α, the timer counter t1 is always incremented by one, that is, clocking is performed.

Then, in the subsequent pinching judgment control routine, if ΔPa exceeds the judgment value α in step 50, the process proceeds to step 56 via steps 54 and 55, and in step 56, the pinching of the past control cycle is performed. The value of the timer count t1 counted in the determination control routine is decremented.

Accordingly, the period t1 as a predetermined time until the timer counter t1 becomes 0 due to this decrement.
In each of the pinch determination control routines executed during the period, in step 57, RA
(M + 1) difference values ΔPax (x = 0,
1,..., M), only those of ΔPax> α are replaced with the determination value α, and the process proceeds to step 70. That is, during the period of t1, the calculation of the difference sum Ps in step 70 is the corrected difference sum Ps.

As a result, step 8 after step 70
At 0, the corrected difference sum Ps and the “threshold value”
A comparison with Psth will be made. Therefore,
In the case of Ps with correction, as in the first embodiment,
Since the value becomes lower than Ps without correction, Ps with correction does not exceed the “threshold value” Psth,
Therefore, erroneous detection is suppressed.

(G) FIG. 6 shows a result obtained by actually measuring the present embodiment by simulation when α = 0, and as shown in FIG.
Since the value is lower than Ps without correction, Ps with correction does not exceed “threshold” Psth,
False detection is suppressed. FIG. 6 is an explanatory diagram for explaining pinch detection when the period difference value changes due to vibration or the like. The vertical axis indicates each parameter (Psth, ΔPa,
Ps) is the time (ms), and the horizontal axis is the elapsed time (t).

The embodiment of the present invention is not limited to the above-described embodiment, but may be as follows. (A) In the second embodiment, the time (T1) when the difference value ΔPa is equal to or smaller than the judgment value α is counted, and when the difference value ΔPa exceeds the judgment value α, the counting is performed. During the period of t1, the determination value α of the difference value ΔPax
Only those exceeding the threshold value are replaced with the judgment value α.
Instead, the time (T
1) is counted, and when the continuation time exceeds a predetermined continuation time, and when the difference value ΔPa exceeds the criterion value α, the criterion value α of the difference value exceeds the criterion value α for a certain period of time. May be replaced with the determination value α.

[0061]

[0062]

As described above in detail, according to the first to third aspects of the present invention, when the pulse period fluctuates due to vibration, impact, or the like, and a pulse having a short pulse period is generated, the pulse period fluctuation By performing parameter correction processing,
An excellent effect of suppressing erroneous detection of entrapment is achieved.

In particular, according to the present invention, there is an effect that erroneous detection can be avoided when a continuous pulse fluctuation occurs on a rough road.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram of a power window device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a pulse signal.

FIG. 3 is an explanatory diagram showing a relationship between a difference sum Ps, a periodic average value Pa, and a threshold value.

FIG. 4 is an explanatory diagram for explaining pinch detection when a period difference value changes due to vibration or the like.

FIG. 5 is an explanatory diagram in the case of actual measurement in the first embodiment.

FIG. 6 is an explanatory diagram in the case of a real side according to the second embodiment.

FIG. 7 is a flowchart illustrating a sandwiching determination control routine according to the first embodiment;

FIG. 8 is a flowchart illustrating a sandwiching determination control routine according to the second embodiment.

[Explanation of symbols]

21: controller constituting a period difference value calculating means, difference sum calculating means, first and second determining means, counting means and correcting means, 22: calculating section, 23: storage section, 27: switching circuit as drive circuit .

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-286477 (JP, A) JP-A-8-260810 (JP, A) JP-A-6-280446 (JP, A) 12464 (JP, Y2) (58) Fields investigated (Int. Cl. ⁷ , DB name) E05F 15/00 B60J 1/00

Claims (3)

(57) [Claims] A drive circuit (27) for supplying a power supply voltage to a motor (M) for opening and closing a window glass.
And a pulse period (P) corresponding to the rotation speed of the motor (M).
n-1 + Pn), a pulse period (Pn-1 + Pn) of the pulse signal (S) at each time is obtained, and a plurality of predetermined past pulse periods (P0 to Pn) are obtained.
-2) to determine the average pulse period (Pa), the average pulse period (Pa) and the pulse period at that time (Pn-1 + Pn)
A period difference value calculating means (21) for calculating a period difference value (△ Pa) with the above, a difference value at that time calculated by the period difference value calculating means (21), and a plurality of predetermined past differences A sum-of-difference calculating means (21) for calculating a sum of differences with the value, and comparing the sum of the differences with a predetermined threshold value to determine whether or not an object has been pinched by the glass during the closing operation of the window glass A first determining means (21) for inverting and driving the motor (M) via the driving circuit (27) when the sheet is being held; When the period difference value is equal to or smaller than a predetermined value (α), a window glass sandwiching detection device including a correction unit that corrects the difference sum. 2. The correction means calculates a difference between the difference value at that time calculated by the periodic difference value calculation means (21) and a plurality of predetermined difference values in the past in order to calculate by the difference sum calculation means. 2. The window glass sandwiching detection device according to claim 1, wherein only those exceeding the predetermined value (α) are replaced with the predetermined value (α). 3. A method according to claim 1, wherein said second determining means determines whether or not the period difference value is equal to or less than a predetermined value, and a duration (t1) when the period difference value is equal to or less than the predetermined value.
A counting means (21) for counting, wherein the correcting means changes the period difference value from a predetermined value to a predetermined value.
When it changes, the counting means (21) counts
During the time corresponding to the continuation time (t1)
In order to calculate the stage, the period difference value calculating means (21)
The calculated difference value at that time and a plurality of predetermined past values
Of the difference values exceeding the predetermined value (α)
The window guard which is to be replaced with the predetermined value (α)
A device for detecting the presence or absence of a lath.