JPH1164373A - Acceleration detecting device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acceleration detecting device which prevents the false detection of the state of acceleration which occurs on an uneven ground, etc., by eliminating noise caused by road irregularities without raising the cost of a controller. SOLUTION: In the case that a minute deceleration or acceleration occurs on a recessed surface, a counter value DLTP is added to an deceleration counter GCNT every basic pulse time PROD (PR0Da-PRODc) responsive to vehicle speed after a vehicle starts to decelerate. When the deceleration is completed, a counter value DLTM is subtracted from the deceleration counter GCNT every basic pulse time PROD. By this, in the case of not exceeding a counter threshold value CLTCNT, the state of deceleration is judged as not requiring the control to release lockup, the release of lockup is not performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration detecting device for a vehicle which determines an acceleration state of a vehicle based on pulse signals generated at time intervals corresponding to a vehicle speed.

[0002]

2. Description of the Related Art As a vehicle acceleration detecting device, a digital rotation sensor that outputs a digital signal is generally used. Such a rotation sensor is a combination of a rotating gear or a perforated disk attached to a rotating shaft and a photoelectric element attached at a fixed position, and the controller generates a pulse signal generated at time intervals corresponding to the vehicle speed. The acceleration state of the vehicle is obtained by counting the output change. In addition, as an example of the rotation sensor,
For example, those described in JP-A-8-15312 can be mentioned.

[0003] By the way, the vehicle acceleration detecting device is used, for example, in a control for releasing a lock-up clutch in order to prevent engine stall due to sudden deceleration in a low vehicle speed range during coasting. In most cases, it is sufficient to detect whether the vehicle is accelerating or decelerating.

However, in such a device,
Since the acceleration state is obtained based on the pulse signal generated at the time interval corresponding to the vehicle speed, when traveling on uneven terrain with unevenness, the acceleration state that is not required for vehicle control is affected by the noise component due to the unevenness. It may be detected incorrectly. Such an erroneous detection is not preferable because it imposes an unnecessary burden on the controller.

Therefore, a method of preventing erroneous detection by improving the controller so that many pulse signals can be detected can be considered. However, in this case, the controller is required to have a large-capacity memory required for calculation and a high processing speed. In other words, increasing the number of times the pulse signal is detected to eliminate the effects of noise components due to road surface irregularities results in an increase in memory capacity and an increase in arithmetic processing speed. The problem of rising occurs.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and eliminates a noise component caused by unevenness of a road surface without increasing the cost of a controller. It is an object of the present invention to provide a vehicular acceleration detection device that prevents an erroneous detection of an acceleration state that is not necessary for vehicle control.

[0007]

According to a first aspect of the present invention, there is provided an acceleration detecting apparatus for a vehicle, which detects a vehicle based on a pulse signal generated at time intervals corresponding to a vehicle speed. When detecting a predetermined acceleration state at the time interval of the pulse signal, the vehicle acceleration detection device for determining the acceleration state of the acceleration signal adds a counter value of a predetermined amount to the acceleration counter, and detects the time of the pulse signal. When the predetermined acceleration state is not detected at intervals, the acceleration counter is counted by subtracting a predetermined amount of the counter value from the acceleration counter, and the counted value becomes a value within a predetermined setting area. The time is determined to be an acceleration state necessary for vehicle control.

According to a second aspect of the present invention, there is provided an acceleration detecting apparatus for a vehicle for determining an acceleration state of a vehicle based on a pulse signal generated at a time interval corresponding to a vehicle speed. When a predetermined acceleration state is detected at the time interval of the pulse signal, a counter value of a predetermined amount is subtracted from the acceleration counter. When the predetermined acceleration state is not detected at the time interval of the pulse signal, the acceleration is increased. The acceleration counter is counted by adding a predetermined amount of counter value to the counter, and when the counted value becomes a value within a predetermined set area, it is determined that the vehicle is in an acceleration state necessary for vehicle control. It is characterized by having made it.

According to a third aspect of the present invention, in the vehicle acceleration detecting device according to the first or second aspect, the predetermined acceleration state detected at the time interval of the pulse signal is based on a predetermined threshold value. It is determined that the threshold value is calculated as a function based on the time interval of the pulse signal.

According to a fourth aspect of the present invention, in the vehicle acceleration detecting device according to the third aspect, the predetermined threshold value is a function of time.

(Equation 2) Dpl: circumferential distance of wheel corresponding to pulse signal interval to: time: time interval of previous pulse signal Vo: previous vehicle speed Gc: acceleration set in advance K: positive integer

According to a fifth aspect of the present invention, there is provided the vehicle acceleration detecting apparatus according to the first aspect, wherein the counter value DLTP added when detecting a predetermined acceleration state at the time interval of the pulse signal is used as the counter value DLTP. The counter value DLTM, which is decremented when a predetermined acceleration state is not detected at the time interval of the pulse signal, is set so as to satisfy a relationship of DLTM> DLTP.

[0012]

As described above, the vehicle acceleration detecting apparatus according to the first aspect of the present invention, when detecting a predetermined acceleration state at a time interval of a pulse signal corresponding to the vehicle speed, requires an acceleration counter. To add a predetermined amount of counter value,
When the predetermined acceleration state is not detected at the time interval of the pulse signal, the acceleration counter is counted by subtracting a predetermined amount of the counter value, and the counted value becomes a value within a predetermined setting area. Since it is determined that the vehicle is in an acceleration state necessary for vehicle control, a large-capacity memory and a high-speed calculation capability are required, so that the noise component due to the unevenness of the road surface is removed without increasing the cost of the controller. It is possible to prevent erroneous detection of the acceleration state in leveling or the like. In addition, since it is not necessary to calculate the actual acceleration that frequently uses multiplication / division at each time interval, it is possible to reduce the burden of the calculation by the controller.

According to a second aspect of the present invention, in the vehicle acceleration detecting device, when a predetermined acceleration state is detected at a time interval of a pulse signal corresponding to the vehicle speed, a predetermined amount is supplied to an acceleration counter. When a predetermined acceleration state is not detected at the time interval of the pulse signal, a counter value of a predetermined amount is added, and the acceleration counter is counted. Since it is determined that a value within the set area is an acceleration state necessary for vehicle control, the same effect as the first aspect is obtained.

According to a third aspect of the present invention, in the vehicle acceleration detecting apparatus according to the first or second aspect, the predetermined acceleration state detected at the time interval of the pulse signal is determined based on a predetermined threshold value. By detecting and calculating the threshold value as a function based on the time interval of the pulse signal, the threshold value can be determined in accordance with the time interval corresponding to the speed of the vehicle that changes every moment. This is because, for example, when the threshold value is constant, the detected acceleration decreases as the vehicle speed increases, so that the detected acceleration varies depending on the vehicle speed. However, according to the present device, the acceleration state can be detected in a stable state. .

According to a fourth aspect of the present invention, there is provided the vehicle acceleration detecting device according to the third aspect, wherein the threshold value is a function of time.

(Equation 3) Dpl: circumferential distance of the wheel to: to: time interval of previous pulse signal Vo: previous vehicle speed Gc: predetermined acceleration K: positive integer, it is possible to detect predetermined acceleration Gc.

According to a fifth aspect of the present invention, there is provided the vehicle acceleration detecting apparatus according to the first aspect, wherein the counter value DLTP added when detecting a predetermined acceleration state at a time interval of the pulse signal is used as the counter value DLTP. The noise component due to unevenness of the road surface is set because the counter value DLTM, which is decremented when a predetermined acceleration state is not detected at the time interval of the pulse signal, is set so as to satisfy DLTM> DLTP.
Can be further removed.

[0017]

An embodiment of the present invention will be described below in detail with reference to the accompanying drawings. In the present embodiment, the term “deceleration (deceleration state)” means a state in which the polarity of the acceleration (acceleration state) is negative.

FIG. 1 is a control system diagram of a power train provided with a vehicle acceleration detecting device according to the present invention. The power train of the vehicle includes a torque converter 10, a transmission 11, and a final reduction gear 12, and power from an engine (not shown) is input from the torque converter 10. The torque converter 10 has a torque increasing function and a torque fluctuation absorbing function, and includes a lock-up clutch 10c inside. The transmission 11 is an automatic transmission, and may be a stepped automatic transmission or a continuously variable transmission. The transmission 11 has the vehicle speed sensor 1 on the output side. Here, the vehicle speed sensor 1
Is a rotating gear or a perforated disk attached to the rotating shaft,
This is a rotation sensor that combines a photoelectric element mounted at a fixed position and outputs a pulse signal at time intervals corresponding to the vehicle speed. The vehicle speed V is obtained by a calculation based on the pulse signal Ro from the vehicle speed sensor 1 input to the controller 100. The power output from the output shaft 13 of the transmission 11 rotates the wheels 15 from the final reduction gear 12 via the axle 14.

The lock-up clutch 10c has a front-rear differential pressure (= PA-P) caused by a torque converter apply pressure PA applied to both sides thereof and a torque converter release pressure PR.
By controlling R), the pump impeller (not shown) and the turbine runner (not shown) of the torque converter 10 are directly connected or opened.

When the apply pressure PA becomes lower than the release pressure PR, the lock-up clutch 10c releases the space between the pump impeller of the torque converter 10 and the turbine runner (converter state), and the apply pressure PA becomes lower than the release pressure PR. When high, the torque converter 10
Is directly connected (lock-up state) between the pump impeller and the turbine runner.

The differential pressure (= PA-PR) is controlled by switching a lock-up control valve 16 in a control valve (not shown). The spring 16S acts in the same direction, and from the other side, the release pressure PR and the spring force act in the same direction, and the signal pressure Ps from the lock-up solenoid 17 acts.

The signal pressure Ps from the lock-up solenoid 17 is determined by using the pump pressure
Is created in accordance with the drive duty D of.
The controller 100 receives a coast state signal I indicating that the vehicle is coasting, a signal RI from the impeller rotation sensor 20, a signal RT from the turbine rotation sensor 30, and a signal Ro from the vehicle speed sensor 1. Note that the impeller rotation sensor 20 can be replaced with a signal from an engine rotation sensor (not shown) that detects the number of rotations of the engine.

The input of these signals causes the controller 10
A rotational speed difference (slip rotation) between the pump impeller and the turbine runner is determined from the impeller rotational speed and the turbine rotational speed detected at 0, and the smallest rotation that does not cause relative rotation between the pump impeller and the turbine runner during coasting. A differential pressure (= PA-PR) is controlled to prevent an engine stall (engine stop) due to a response delay when releasing lockup at a predetermined deceleration during coasting, for example. Note that the relationship between the duty-controlled signal pressure Ps and the differential pressure (= PA-PR) based on the signal pressure Ps is as shown in FIG. 2. When the signal pressure Ps is small, the lockup is released. When the signal pressure Ps increases, the lockup occurs.

FIGS. 3 and 4 are flowcharts illustrating an embodiment of the vehicle acceleration detecting device according to the present invention. FIG. 3A is a flowchart for determining whether or not the vehicle is in a stopped state, and is repeatedly executed. FIG. 3B is a main flowchart for detecting the deceleration state of the vehicle, and each time the pulse signal Ro is input to the controller 100,
Runs at sufficiently short intervals, regularly or irregularly. FIG. 4 is a flowchart for counting a counter value of a predetermined amount for the deceleration counter.
Interrupt processing is performed in step 517 of FIG.

The operation according to these flowcharts will be described below with reference to FIG. First, in step 501 of FIG. 3A, it is determined whether the vehicle is in a stopped state. At this time, if the vehicle is in a stopped state, the process proceeds to step 502, and the vehicle state flag is set to “VCNT =
0 ". However, if the vehicle is not in a stopped state, the process exits the flowchart of FIG.

Here, the pulse signal Ro from the vehicle speed sensor 1 is obtained.
Is input, a rotation speed input capture interrupt is performed, and the flowchart of FIG. 3B is executed.

In step 511 of FIG. 3B, the time at which the pulse signal was input is stored as time data Ta, and it is determined whether or not the vehicle state flag is "VCNT = 1". Since the vehicle state flag is “VCNT = 0” in a state where the vehicle has started to start, Step 51 is executed.
At 6, the vehicle status flag is incremented to "VCNT = 1".

Thereafter, the running vehicle state flag is set to "VCN".
Since “T = 1”, when a new pulse signal is input, in step 511, the time at which the pulse signal was input is stored as time data Tb. At this time, since the vehicle state flag is “VCNT = 1”, step 51
At 2, the previous time data Ta and the current time data T
b, a basic pulse time (or basic pulse period) P which is a time interval of a pulse signal generated corresponding to the vehicle speed.
Calculate ROD.

After calculating the basic pulse time PROD,
In step 514, it is determined whether a predetermined deceleration state is detected in the basic pulse time PROD. Here, if the basic pulse time PROD is equal to or greater than a predetermined threshold value (hereinafter referred to as a deceleration determination threshold value) CLTPROD, a condition for detecting a predetermined deceleration state (in this embodiment, a condition to be regarded as a rapid deceleration state) is set. And then proceed to step 515,
Set the deceleration flag to "CLTG = 1". In step 514, the basic pulse time PROD is set to the deceleration judgment threshold C.
If LTPROD is not satisfied, it is determined that the predetermined deceleration state is not detected, and the process proceeds to step 518, and the deceleration flag is set to “CLTG = 0”.

In step 513, a new deceleration judgment threshold value CL for the next basic pulse time PROD is calculated.
Calculate TPROD. The deceleration determination threshold CLT
The method of calculating PROD will be described later in detail.

In step 513, the deceleration judgment threshold value CLTPR
After calculating the OD and proceeding to step 517, in this step 517, the deceleration counter GCNT is operated according to the flowchart of FIG. 4 in order to determine whether or not the vehicle is in a deceleration state necessary for releasing lockup. That is,
When detecting the deceleration state with the basic pulse time PROD,
A predetermined amount of the counter value DLTP is added to the deceleration counter GCNT, and when the deceleration state is not detected in the basic pulse time PROD, the predetermined amount of the counter value DLTM is subtracted from the deceleration counter GCNT. Then, the deceleration counter GCNT is counted, and when this count value becomes a value within a predetermined set area, it is determined that the vehicle is in a deceleration state necessary for vehicle control.

Hereinafter, the flowchart of FIG. 4 will be described in detail. First, in step 800, the deceleration flag is set to "CLT
G = 1 "is determined. When the deceleration flag is "C
If LTG = 1 ”, it is determined that a predetermined deceleration state is detected in the basic pulse time PROD, and step 80 is performed.
Move to 1. This step 801 is a limiter for limiting the addition side of the deceleration counter GCNT, and determines whether or not the deceleration counter GCNT exceeds the maximum count value GLIM. When the vehicle starts to start, the deceleration counter GCNT does not exceed the maximum count value GLIM, so the process proceeds from step 801 to step 802, where a predetermined amount of counter value DLTP is added to the deceleration counter GCNT. I do. However, step 80
1, the deceleration counter GCNT counts the maximum count value GLI
If it exceeds M, step 802 is not executed.

If the deceleration flag is "CLTG = 0" at step 800, the basic pulse time PRO
Assuming that the predetermined deceleration state is not detected in D, the process proceeds to step 803. This step 803 is a limiter that limits the subtraction side of the deceleration counter GCNT, and determines whether the deceleration counter GCNT does not fall below the minimum count value DLTM. Deceleration counter GCNT
If exceeds the minimum count value DLTM, the process proceeds to step 804, where the deceleration counter GCNT is subtracted by a predetermined counter value (the same value as the minimum count value DLTM in this embodiment). I do. However, the deceleration counter GCNT has the minimum count value DLTM.
If the value is less than, the routine goes from step 803 to step 805, where the deceleration counter GCNT is cleared to "GCNT = 0".

At step 806, steps 802, 8
04, 805 deceleration counter GC counted
The magnitude relationship between NT and a predetermined threshold value CLTCNT is compared. At step 806, the deceleration counter GCNT
Is greater than or equal to the threshold value CLTCNT, it is determined that the vehicle is in a deceleration state necessary to release lockup, and the routine proceeds to step 807. In step 807, the lock-up solenoid 17 is duty-controlled, and the lock-up is released by lowering the apply pressure PA from the lock-up control valve 16 below the release pressure PR. If the deceleration counter GCNT falls below the threshold value CLTCNT, it is determined that the vehicle is not in a deceleration state necessary to release lockup, and the program of step 807 is not executed.

FIG. 5 illustrates a method of calculating the deceleration determination threshold value CLTPROD described in step 513 of FIG. 3B. Note that the deceleration determination threshold value CLPPROD
Is for determining a predetermined deceleration state for each basic pulse time PROD. FIG. 5A shows a deceleration determination threshold CLTP.
6 is a characteristic curve X for obtaining ROD. In step 513 of FIG.
Basic pulse time PROD (PROD (N-1)
) Is determined. This threshold value CLPPROD becomes a deceleration determination threshold value to be used next time.

FIG. 5B shows a characteristic curve Y plotting the deceleration Gc for judging the deceleration state for each vehicle speed.
It is. In the present embodiment, the upper region A of the curve Y is
This is an area in which lockup is released assuming rapid deceleration, and a lower area B of the curve Y is an area in which it is determined that rapid deceleration is not occurring. That is, the deceleration determination threshold C obtained in FIG.
Determining the deceleration state by comparing LTPROD with the latest basic pulse time PROD is performed by comparing the deceleration actually calculated from the latest basic pulse time PROD with the deceleration Gc shown in FIG. It is the same as making a judgment.

That is, the deceleration state required for releasing the lock-up is detected based on a predetermined threshold value CLPPROD, and this threshold value CLPPROD is detected as the basic pulse time PR.
Since it is calculated as a function of OD, the basic pulse time PRO
It is not necessary to calculate the actual deceleration for each D. Accordingly, not only the actual deceleration is not detected, but also the load on the controller 100 can be reduced.
Since it is not necessary to calculate the actual acceleration that frequently uses multiplication / division, the load on the controller due to the calculation can be reduced. In addition, it is not necessary to increase the high-speed operation capability of the RAM (random access memory).

FIG. 6 is a time chart for explaining the operation of the present invention. When the vehicle decelerates as shown in FIG. 7A, the time interval of the pulse signal Ro corresponding to the vehicle speed V, that is, the basic pulse time PROD increases with time, as is apparent from FIG. . According to the present invention, the basic pulse time PROD is compared with a predetermined threshold value CLTPROD, and it is determined that the vehicle is in a predetermined deceleration state. If the deceleration flag in FIG. ), The basic pulse time PROD corresponding to the vehicle speed V
Each time, the counter value DLTP is added to the deceleration counter GCNT. Then, the added deceleration counter GC
NT is the counter threshold value CLTCN as shown by the symbol β.
Only when the value becomes equal to or more than T, it is determined that this running state is a deceleration state necessary for releasing lockup, and a flag for detecting deceleration is set as shown in FIG. Turn ON to release lockup.

FIG. 7 shows an example in the case of traveling on a convex road. On the convex surface as shown in the figure, the vehicle speed V fluctuates in a short time, and an acceleration state in which lock-up does not need to be released occurs, as indicated by reference numeral γ in FIG. According to the present invention, the basic pulse time PROD is compared with a predetermined threshold value CLTPROD. If the deceleration flag in FIG. The counter value DLTP is added to the deceleration counter GCNT in FIG.
Is added.

However, when the vehicle slips over the convex surface, the basic pulse time PRO indicated by the symbol α2 in FIG.
From Dc, it is determined that the vehicle is not in the predetermined deceleration state, and the deceleration flag in FIG. (C) becomes “GCLT = 0”, and the deceleration counter GCNT in FIG.
Subtract with TM. Therefore, on such a convex road surface,
The counted value of the deceleration counter GCNT does not exceed the counter threshold value CLTCNT. That is, it is determined that the vehicle is not in the deceleration state necessary for releasing the lockup on the minute uneven road surface, as shown in FIG. No cancellation is performed.

Thus, when the same condition is observed in the prior art shown in FIG. 7F, deceleration is started at the reference numeral α1 in FIG. 9B, and it is determined that the vehicle is in a deceleration state necessary for releasing lock-up. Therefore, the flag for detecting the deceleration is turned on even by a slight speed change as indicated by the symbol β.
Then, the lockup is released.

As is clear from the comparison with the prior art, according to this embodiment, when the count value of the deceleration counter GCNT is used to detect the deceleration state in the basic pulse time,
The counter value DLTP is added to the deceleration counter,
When the deceleration state is not detected in the basic pulse time, the counter value DLTM is subtracted from the deceleration counter to obtain the value. Therefore, the memory capacity is increased to detect many pulse signals, or the arithmetic processing speed is increased. By doing so, it is possible to eliminate noise components caused by unevenness of the road surface without increasing the cost of the controller, and prevent erroneous detection of a deceleration state that is unnecessary for vehicle control that occurs on uneven terrain or the like.

In the present invention, as another embodiment,
When the deceleration state is detected in the basic pulse time, the counter value DLTM is subtracted from the deceleration counter. When the deceleration state is not detected in the basic pulse time, the counter value DLTP is added to the deceleration counter. Is also good.

The threshold value CLPPROD is calculated as a function of time as follows:

(Equation 4) Dpl: circumferential distance of wheels equivalent to basic pulse time PROD to: time interval of previous pulse signal Vo: previous vehicle speed Gc: preset deceleration K: positive integer

As a result, the acceleration Gc set in advance can be detected.

Further, a counter value DLTP which is added when detecting the deceleration state in the basic pulse time PROD,
The counter value DLTM, which is decremented when the deceleration state is not detected in the basic pulse time PROD, is expressed by DLTM> DLT
By setting so as to satisfy P, noise components due to road surface unevenness can be further removed.

[Brief description of the drawings]

FIG. 1 is a control system diagram showing a power train including a vehicle acceleration detection device according to the present invention.

FIG. 2 is a diagram illustrating a relationship between a differential pressure supplied to a lockup clutch and a signal pressure Ps.

FIG. 3A is a flowchart for determining whether a vehicle is in a stopped state. (B) is a main flowchart for detecting the deceleration state of the vehicle.

FIG. 4 is a flowchart for counting a counter value of a predetermined amount for a deceleration counter.

FIG. 5A shows a threshold value CLTPRO used for deceleration determination.
FIG. 9 is a diagram illustrating a method for calculating D. (B) is a diagram for explaining a method of determining the deceleration determination based on the deceleration Gc.

FIG. 6 is a time chart illustrating the operation of the present invention.

FIG. 7 is a time chart illustrating the operation of the present invention when traveling on a convex road surface.

[Explanation of symbols]

 1 Vehicle speed sensor 10 Torque converter 10a Lock-up clutch 11 Transmission 12 Final reducer 13 Output shaft 14 Axle 15 Wheel

Claims (5)

[Claims] An acceleration detecting device for a vehicle, which determines an acceleration state of a vehicle based on a pulse signal generated at a time interval corresponding to a vehicle speed, wherein when detecting a predetermined acceleration state at a time interval of the pulse signal, When a predetermined amount of counter value is added to the acceleration counter and a predetermined acceleration state is not detected at the time interval of the pulse signal, the predetermined amount of counter value is subtracted from the acceleration counter, An acceleration detecting device for a vehicle, wherein an acceleration counter is counted, and when the counted value becomes a value within a predetermined setting area, it is determined that the vehicle is in an acceleration state required for vehicle control. 2. A vehicular acceleration detection device for determining an acceleration state of a vehicle based on a pulse signal generated at a time interval corresponding to a vehicle speed, wherein when detecting a predetermined acceleration state at a time interval of the pulse signal, When a predetermined amount of counter value is subtracted from the acceleration counter, and a predetermined acceleration state is not detected at the time interval of the pulse signal, a predetermined amount of counter value is added to the acceleration counter, An acceleration detecting device for a vehicle, wherein an acceleration counter is counted, and when the counted value becomes a value within a predetermined setting area, it is determined that the vehicle is in an acceleration state required for vehicle control. 3. The method according to claim 1, wherein the predetermined acceleration state detected at the time interval of the pulse signal is determined based on a predetermined threshold value, and the threshold value is set to a function based on the time interval of the pulse signal. A vehicle acceleration detection device characterized in that it is calculated as: 4. The method according to claim 3, wherein the predetermined threshold value is a function of time. Dpl: circumferential distance of the wheel corresponding to the interval of the pulse signal to: to: time interval of the previous pulse signal Vo: previous vehicle speed Gc: predetermined acceleration K: positive acceleration represented by: Detection device. 5. The method according to claim 1, wherein the counter value DLTP added when detecting a predetermined acceleration state at the time interval of the pulse signal, and when the predetermined acceleration state is not detected at the time interval of the pulse signal. Wherein the counter value DLTM to be subtracted from the above is set so as to satisfy a relationship of DLTM> DLTP.