JPS59141748A - Idling-speed controlling method - Google Patents

Abstract

PURPOSE:To prevent undershooting of the idling speed, by storing a learnt value at a particular instant in a non-volatile memory as a learning starting value, and updating the learnt value in case that the learnt value satisfies a particular condition. CONSTITUTION:A CPU30 processes data given from various sensors and controls operation of an ISCV13, etc. A learnt value and a learning starting value stored in a back-up RAM33 are stored in a learnt value monitor and a learning starting value monitor at a prescribed address of an RAM32. When the learnt value becomes lower than the learning starting value and the deviation becomes greater than a prescribed value, the learnt value is updated by obtain a new learnt value by substracting a prescribed value from the learning starting value. By employing such a method, it is enabled to cause undershooting of the idling speed and hence to prevent occurrence of engine stall.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to idle speed control of a vehicle engine, and in particular, to a method for determining a target value for the idle speed according to a load applied during idling and maintaining the target value. The present invention relates to an idle rotation speed control method for learning and controlling the idle rotation speed.

[Prior Art] In recent years, with the deterioration of the energy situation, there has been an increasing demand for lower fuel consumption in automobiles, and in conjunction with the tightening of exhaust gas regulations, various methods have been proposed to improve fuel efficiency and purify exhaust gas. One such method is to precisely control the idle speed according to various conditions under which the engine is placed, such as intake air temperature and engine cooling water temperature.

This method is usually called an idle speed control system (hereinafter simply referred to as ■SC), and it adjusts the amount of intake air flowing into a bypass path that bypasses the throttle valve during idle rotation, and adjusts the idle rotation speed to a target value, that is, the target rotation speed. It is an attempt to control the

Conventionally, in such ISO, when a change occurs in the load when the engine is idling, for example, if the vehicle is equipped with an air conditioner (near conditioner), the operating state of the air conditioner changes from on to off. Alternatively, when the power steering device changes from an off state to an on state, or similarly when the operating state of the power steering device changes, the target value of the idle speed is changed to adjust the engine speed to correspond to the load applied to the engine during these idle speeds. In addition, in the idle rotation speed control method, this is learned as appropriate based on the control values of the throttle valves 1 to 1 for each load, and the learned values are determined and stored in non-volatile memory. Based on this learned value and engine stall, the amount of intake air passing through the bypass path is controlled to quickly bring the idle speed closer to the target value and maintain stable idle speed even when engine conditions change over time. A method has been proposed to control the idle speed. When feedback control is performed and the idle speed is controlled to the target value, the amount of intake air flowing through the bypass passage is equal to the amount of intake air flowing through the slightly opened throttle valve. Less controlled.

Therefore, the learning value at that time will be learned in the direction of closing the bypass path. When switching from such a feedback control state to open loop control that does not rely on feedback control, and then performing feedback control again, there is no problem as long as the throttle valve is slightly open as in the previous feedback control, but if the throttle valve If the valve is completely closed, the amount of intake air passing through the bypass path at the time when the feedback control is restarted is controlled based on the learning value learned during the previous feedback control. As a result, since the amount of intake air is reduced, there is a possibility that an engine stall will occur, and even if an engine stall does not occur, there is a problem in that the idle speed will significantly undershoot when feedback control is resumed. .

This problem becomes more complex when the loads on the engine at idle are different.

For example, when the air conditioner is applied as a load to the engine, the intake air amount is learned to be smaller as described above, and then open loop control or feedback control is performed to remove the load from the air conditioner, etc., and then the air conditioner is loaded again. If the engine stalls due to a decrease in the amount of intake air, the driver determines that there is an abnormality in the air conditioner.

Such a phenomenon appears even more complicated when various learning values are provided for each load.

[Object of the Invention] An object of the present invention is to provide a guard when updating learned values stored in non-volatile memory corresponding to each load applied to the engine during idling, so that the learned values for each load do not become extremely large. It is an object of the present invention to provide a method for controlling the idle rotation speed, which solves the above-mentioned problems by preventing the value from becoming small.

[Configuration of the Invention] The gist of the configuration of the present invention that achieves the above object is to determine a target value of the idle rotation speed according to the load applied to the engine during idle rotation, and to store a learned value for each load in a nonvolatile memory. In the idle rotation speed control method, the purpose is to control the engine based on the operating state of the engine and the learned value so as to maintain the target value during feedback control of the idle rotation speed. a learning value when the vehicle is stopped and feedback control of the idle rotation speed is started as a learning start value, and the learning value decreases from the learning start value due to learning during the feedback control;
If the difference is a predetermined value or more, an update process is performed in which a value obtained by subtracting the predetermined value from the learning start value is set as a new learning value. be.

The present invention will be explained below by giving an example and referring to the drawings.

[Example] First, FIG. 1 shows an example in which the method of the present invention is applied. FIG. 2 is an explanatory diagram showing an engine and its peripheral devices.

1 is the engine body, 2 is the piston, 3 is the spark plug, 4
is a υ1 gas manifold, 5 is an oxygen sensor provided in the exhaust manifold 4 and detects the residual oxygen concentration in the exhaust gas,
6 is a fuel injection valve that injects fuel into the intake air of the engine body 1, 7 is an intake manifold, 8 is an intake air temperature sensor that detects the temperature of the intake air sent to the engine body 1, and 9 is a sensor that detects the temperature of engine cooling water. 10 is a throttle valve; 11 is a throttle sensor that is linked to the throttle valve 10 to detect the fully open state of the throttle valve 10 and output a signal; 12 is a throttle valve 10;
13 is an idle speed control valve (I'5CV) that controls the opening area of the bypass path 12, 14 is an air flow meter that measures the amount of intake air, and 15 is an air flow meter that absorbs the pulsation of intake air. Each represents a surge tank.

16 is an igniter that outputs the high voltage necessary for ignition; 17 is a nice repeater that is linked to a crankshaft (not shown) and distributes the high voltage generated by the igniter 16 to the spark plugs 3 of each cylinder; 18 is a nice repeater that outputs the high voltage necessary for ignition; A rotation angle sensor 19 is attached to the distributor 17 and outputs 24 pulse signals per one revolution of the distributor 17, that is, two revolutions of the crankshaft.
20 is an electronic control circuit, 21 is a key switch, and 22 is a starter motor.

Furthermore, 23 indicates a passage through which air flows bypassing the throttle valve when the engine is cold, that is, a fast-idle bypass passage. Reference numeral 24 indicates an air valve that controls air passing through the fast idle bypass path 23. Note that the air valve 24 operates to open the fast idle bypass passage 23 in order to secure the engine speed necessary for warm-up operation when the engine is cold.

25 is an air conditioner, 26 is a vehicle speed sensor, 27 is a Nicotral switch representing an armor in which the shift lever is pressed to neutral or bulking range in an automatic car, 28 is a steering sensor, 29 is a power steering drive device, and steering sensor 28 Power steering drive device 2 based on detection of steering wheel rotation angle by
9 is activated.

Next, FIG. 2 shows a block diagram of the electronic control circuit 20. As shown in FIG.

30 is a central processing unit (hereinafter simply referred to as CPU) that inputs and calculates data output from each sensor according to a control program and performs processing to control the operation of various devices such as 15CV13; 31 is a control unit; A read-only memory (hereinafter simply referred to as ROM) in which programs and initial data are stored; 32 is an electronic circuit 2;
Random access memory (hereinafter simply referred to as RAM) in which data input to o and data necessary for arithmetic control are read and written in one go; 33 is data necessary for subsequent engine operation even when the key switch 21 is turned off. so as to hold
A backup random access memory (hereinafter simply referred to as backup RAM) as a non-volatile memory backed up by a random access memory, 34 to 37 are buffers for the output signals of each sensor, and 38 is a buffer for the output signals of the sensors to the CP.
tJ30 is a multiplexer that selectively outputs, 39 is an A/D converter that converts an analog signal into a digital signal, 4
0 sends each sensor signal to the CPU 30 via the air conditioner signal or buffer, or via the buffer, multiplexer 38 and A/D converter 39, and also sends the control 1 to roll signals from the multiplexer 38 and A/D converter 39 from the CPU 30. represents an input/output port that outputs.

41 converts the output signal of the oxygen sensor 5 into the comparator 4.
43 is a shaping circuit that shapes the waveforms of the output signals of the rotation angle sensor 18 and the cylinder discrimination sensor 19;
4 represents a drive circuit that receives a signal from the CPtJ30 and drives the power steering device, and 45 represents a drive circuit that drives the l5CV"13 based on a signal from the C'P U 30. Each sensor signal is transmitted directly or via a buffer. CPU 30 by input/output port 46 via 41 etc.
The l5CV13 and power steering device 29 are sent to the CPU 30 via the input/output board 46 and the drive circuit.
controlled by the output signal of

Additionally, 47.48 connects to CP via output port 49.5o.
'The drive circuits that drive the fuel injection valve 6 and the igniter 16 by signals from U30 are respectively shown. Also, 51 is a path line that serves as a path for signals and data, and 52 is a C
It represents a clock circuit that sends a clock signal serving as a control timing to the PU 30, ROM 31, RAM 32, etc. at predetermined intervals.

Next, a control program which is a main part of this embodiment will be explained.

FIG. 3 is a flowchart showing a control program 60 for "rrsc calculation". This program is a part of a main program that performs other processes such as fuel injection amount control, or is executed at a predetermined timing in the form of a subroutine.

First, when the processing of this program 60 is started, it is determined in step 61 whether or not a load is applied to the engine 1, for example, whether the air conditioner 25 is on. If the air conditioner 25 is on, The process moves to step 62.

In step 62, the l5C
A learning value DGA for controlling V13 and a learning start value DGΔS when the air conditioner 25 is added as a load are read out from the backup RAM 33, and the learning value monitor DG at a predetermined location in the RAM 32 is read out.
M, written to learning start value monitor DGSM. After the vehicle is manufactured, the learning value and the learning start value are respectively stored at specified locations in the backup RAM'33 as values that are appropriately updated according to changes in the operating state of the engine 1 over time, as will be described later. Even if 21 is turned off, the memory is maintained by receiving power directly from the battery.

On the other hand, if it is determined in step 61 that the air conditioner 25 is in the off state, in step 63 the learning value DG and the learning start value DGS for when no load is applied to the engine 1 are read out from the backup RAM 33, and each It is written to the learning value monitor DGM and the learning start value monitor DGSM in the RAM 32.

Backup R, AM in step 62 or 63
After the learning value and the learning start value corresponding to the load are written into the RAM 32 from step 33, the process moves to step 64.

In step '64, the vehicle speed detected by the vehicle speed sensor 2 is extremely low, for example 2.5. It is determined whether or not the speed is below 2.5 km/h, and if it is below 2.5 km/h, the process moves to the next step 65.

In step 65 (5I), it is determined whether or not conditions suitable for feedback control of the idle speed are met, for example, when the throttle valve 1 is detected by the throttle sensor 11.
Whether a signal indicating that 0 is fully open is being output,
The water temperature sensor 9 that detects the engine cooling water temperature determines whether the temperature is 70° C. or higher, which indicates that the engine 1 has been sufficiently warmed up, and the throttle valve 10
If the platform is fully open and the water temperature is 70°C or higher, the process moves to the next step 66.

In step 66, a check is made to determine whether a flag indicating the stopped state of the vehicle (hereinafter referred to as flag FVo), which is set to "1" when the vehicle speed is greater than 2.5 km/h, has already been set to "1". is determined and the flag F V o is set, the vehicle speed is reduced to 2.5 km/h.
It is determined that the state is immediately after the value becomes less than h, and the process moves to step 67.

In step 67, since the vehicle speed has become less than 2,51v/h, it is assumed that the vehicle has almost stopped, and the flag FVo is set to rOJ.
to lyat.

In step 68, it is determined that the vehicle speed has decreased from 2.5 km/h to 2.5 km/+1 for the first time, and is stored in the learning value monitor DGM in order to start feedback control of the idle rotation speed. The current learning value is stored as a new learning starting value in place of the learning starting value already stored in the learning starting value monitor DGSM, and the process proceeds to the later-described "feedback control calculation" routine shown at 69.

On the other hand, if it is determined in step 66 that the flag FVo is rOJ, it is determined that the vehicle speed has been reduced and the vehicle is already at a stop, and feed pack control has been started, so the processing in steps 67 and 68 is performed. without doing
The process of "feedback control calculation" routine 69 is executed.

In step 70, which is processed after the processing of the "feedback control calculation" routine 69, the sum of the integral term DI and the proportional term DP and the learned value monitor DGM are calculated in the "feedback control calculation" routine 69. are compared, and the value of the learning value monitor DGM is [Σf(ΔN)+
-Q(bN')', the value of the learned value monitor DGM is reduced by a fixed value, for example, 0°02%, and if the current 40% is reduced to 39.98%, conversely, the value of the learned value monitor DGM is reduced to [ Σf(m) is set to 42.02%, and if the value of the learned value monitor DGM is equal to Σf(m) 10 (6A/) J, the value of the learned value monitor DGM is left as is, that is, the learned value monitor The DGM is updated, and the learned value monitor DGM in the RAM 32 is rewritten.

In the following step 71, the value of the learning value monitor DGM updated in the previous step 70 and the learning start value monitor I)G
A comparison is made with a constant value, for example, a value subtracted by 2% from SM, and if they are equal or the value of DGM is larger, the value of learned value monitor DGM updated in step 70 is left as is,
Proceed to the next step 72; on the other hand, if the value of DGM is small,
2 from the learning start value monitor DGSM in step 73.
After the value reduced by % is set as the value of the learned value monitor DGM, the process moves to step 72.

In step 72, it is determined whether or not the process that has been performed up to this point is a process in which the air conditioner 25 is on. If the air conditioner 25 is in the on state, step 7
Move to 4.

In step 74, the value currently stored in the learned value monitor DGM is 'For example, the load is the air conditioner 25.
Since this is the value when the is on, the value of the learned value monitor DGM in the RAM 32 is stored in the backup RAM'M 33 as the learned value DGA when the air conditioner 25 is on, and similarly the value of the learning start value monitor DGSM is stored as the learned value DGA when the air conditioner 25 is on. , air conditioner 2
Backup RA as learning start value DGAS when 5 is on
It is stored in M33, and the processing of this program 60 ends.

On the other hand, if it is determined in step 72 that the process up to now is the process when the air conditioner 25 is off, the value currently stored in the learned value monitor DGM is when the air conditioner 25 is off, that is, when the special load is It is stored in the backup RAM 33 as a learning value DG when the air conditioner is not connected, and similarly stored in the backup RAM 33 as a learning start value DGS when the air conditioner 25 is turned off. The processing of this program 60 ends.

If it is determined in step 64 that the vehicle speed is greater than 2.5 km/h and is not suitable for feedback control of the idle rotation speed, the process proceeds to step 76, and the vehicle is stopped. 7 lag FVo is set to "1" to indicate that there is no data, and the process moves to the subsequent step 77.

In step 77, the duty ratio of the 15CV13 drive signal during non-feedback control, ie, open loop control, is calculated based on the value of the learned value monitor DGM and according to the water temperature, vehicle speed, etc.

In the following step 78, the already calculated l5
The duty ratio data of the drive signal of CV13 is sent to the register in the input/output port 46, and this program 60 is executed.
After completing the processing, the data set in the input/output port 46 is sent to the drive circuit 45 of the l5CV13 at a predetermined timing, and the l5
The CV 13 is driven and the amount of intake air passing through the bypass passage 12 is controlled.

Further, in step 65, if the throttle valve 10 is fully opened (or if the water temperature is lower than 70°C, feedback control of the idle speed is performed in the same way as when the vehicle speed is greater than 2.5 km/h). If it is determined that the program is not suitable, the process moves to step 77, and after executing the process of step 78, the process of this program ends.

Next, the program of the "feedback control calculation" routine 69 shown in FIG. 4 will be explained.

This routine 69 is stored in the ROM 31 in the form of a subroutine, and when the processing of this routine 69 is started, first in step 80, the idle speed is adjusted depending on the load condition applied to the engine, that is, whether or not the air conditioner 25 is on. A target value NF is determined. For example, if the air conditioner 25 is on, the NF is 900 ppm, and the air conditioner 2
If 5 is not running, NF will be returned 750 rpn+.

In the following step 81, the current idle rotation speed N
Based on the difference ΔN between E and the target value NF determined in the previous step, an integral term D'I and a proportional term DP that determine the duty ratio of the drive signal of the 15CV13 are calculated. Here, the integral term DI is the integral term calculated by a predetermined function f(ΔN) in each process of this step, and is expressed as Σf(muN) and is stored in the RAM 32. This shows the trend of changes in idle speed.

Further, the proportional term DP is expressed by a predetermined function g(AN), and represents a value corresponding to momentary changes in the idle rotation speed. If this step is performed for the first time after feedback control of the idle rotation speed is started, the integral term DI that has already been integrated is not stored in the RAM 32, so the corresponding integral term DI is replaced with the integral term DI. The value stored in the learning value monitor DGM4 corresponding to the load is used as an integral term.

Furthermore, in the next step 82, the expected term DT of the duty ratio of the drive signal of the l5CV13 corresponding to the current load is determined, and finally the duty ratio of the drive signal of the l5CV13 is set as the sum of DI, DP, and DT, and the processing is performed. The process moves to step 83.

In step 83, the duty ratio of the driving signal for l5CV13 calculated in the previous step 82 is set in the register in the input/output port 46, and the processing of this routine 69 is completed.

[Operations and Effects of the Embodiment] As a result of the processing of the "ISC calculation" program 60 and the "feedback control calculation" routine 69, the idle rotation speed is controlled as described below.

When control is started, first, a learning value (for example, DG or DG
A) and learning starting value (e.g. DG8 or DGAS)
are the learned value monitors DG at predetermined locations in RAM 32, respectively.
M, stored in learning start value monitor DGSM.

Then, it is determined whether or not the vehicle speed is suitable for performing feedback control by looking at the state of the throttle valve 10 and water flow, and it is determined that the state is suitable for performing feedback control only after the vehicle speed has decelerated. In this case, the learning value stored in the learning value monitor DGM is stored in the learning starting value monitor DGSM as the learning starting value at the start of feedback control corresponding to the load at that time, and the value of the learning starting value monitor DGSM is updated. If the value of the learning value monitor DGM updated during the feedback control becomes smaller than the value of the learning start value monitor DGSM, and the difference is greater than 2%, rDGsM-2%
The learning value corresponding to the current load stored in the backup RAM 33 is updated with the value of `` as a new learning value, and the value of the learning value monitor DGM is changed to rDGsM.
-'2%', the learned value monitor [)-GM value is used as the new learned value,
The learning value corresponding to the current load stored in the backup RAM 33 is updated.

That is, in updating the learned value, it is recommended that a lower limit be guarded based on the learning start value.

One or more effects of this embodiment will be compared with a conventional example and will be explained based on the drawings.

First, in the conventional example, when the learning start value is not stored as shown in FIG. For example, in order to maintain the rotational speed at the target value, the duty ratio of the 15CV drive signal is reduced to a certain constant value. At that time, the learned value DG when no load is applied also decreases as the duty ratio decreases. Next, when a load is applied at timing t3 in that state, that is, when the air conditioner is turned on during operation, the learned value DG of the air conditioner on state that is already stored
A new duty ratio is determined based on A and increased as shown. However, since the throttle valve is still slightly open, the idle speed exceeds the target value, so the duty ratio is gradually reduced by feedback control, and as a result, the value of the learned value DGA is also reduced.

Then, at timing t4, the air conditioner turns off,
If an acceleration operation is performed at timing t5, feed back and back control of the idle rotation speed is stopped, and then feedback control is started again at timing t6, and the throttle valve is in a fully closed state at that point. Since control is started based on the learned value DG when the throttle valve is slightly open,
The duty ratio is reduced and the idle speed undershoots, causing engine stall in severe cases.

In addition, if feedback control is started at timing t6 and the idle rotation is maintained although the idle rotation speed undershoots, if the air conditioner is turned on at timing t9, the learned value of the air cone on condition is set at that point. Control is performed based on the DGA, and the above-mentioned J: Sea urchin idle speed undershoots,
In severe cases, engine stall may occur.

On the other hand, according to this embodiment, as shown in FIG. 6, feedback control is started at the timing tl,
Even if the throttle valve 10 is slightly opened at the timing of tl and the duty ratio of the IS and CV13 drive signals decreases significantly, the learning value DG remains below the value obtained by subtracting a predetermined value from the learning start value DO8 at the start of feedback control. Must not be. The same is true when the air conditioner 25 is turned on at timing t3, and the learned value D corresponding to the air conditioner 25 on state is the same.
GA does not become less than a value obtained by subtracting a predetermined value from the learning start value DGAS.

Therefore, if the acceleration operation is performed at timing 15, the feedback control is interrupted, and the feedback control is started again at timing t6 with the air conditioner 25 off and the throttle valve 10 fully open, then the previous feedback control Control is started based on the lower limit guarded learning value DG. As a result, even if the throttle valve was slightly opened and the learning value DG was reduced in the previous feedback control, the undershoot of the idle rotation speed can be kept small in the current feedback control. The same holds true even when the air conditioner 25 is turned on at timing t.

Therefore, unlike in the past, the idle speed does not significantly undershoot or engine stall occurs when feedback control of the idle speed is restarted, and even if a learning value is set according to the load, the feedback control is still in progress. When the load changes, the idle speed will not undershoot significantly, the engine will not stall, and the driver will not be reminded of any trouble occurring. Furthermore, it becomes possible to control the idle rotation speed in a manner that fully corresponds to changes in the engine over time.

In this embodiment, the air conditioner 25 is used as an example of the load.
However, in automatic vehicles, the load applied to the engine 1 during idling is different depending on whether the shift lever is in neutral or parking range or in another range, so the state of the neutral switch 27 Depending on the situation, a learning value and a learning start value may be provided separately. ,
Learning start values may be provided separately, and if the memory contents of the backup RAM 33 are destroyed, each learning value may be updated by the process described in the control program described above. In that case, multiple loads are applied to the engine 1 at the same time.
If the learning value and learning start value are to be set separately depending on the case, or the priority order is established among multiple loads, the idle speed is set based on the learning value and learning start value of the load with priority. Feedback control of the number may also be performed.

[Operations and Effects of the Invention] The idle speed control method of the present invention stores a learned value in a backup RAM (non-volatile memory) corresponding to the load applied to the engine during idle speed, and a learned value for each learned value. , stores a learning start value which is a learning value at the time when feedback control is started, and when updating the learning value by 6 during feedback control, the learning value is decreased and the difference from the learning start value is larger than a predetermined value. In this case, a value obtained by subtracting a predetermined value from the learning start value is set as a new learning value, and a guard is provided at the lower limit of the learning value.

Therefore, according to the present invention, it is possible to prevent the value of the learned value from becoming extremely small during feedback control of the idle speed, and even if the feedback control is started again after the feedback control is interrupted, the idle speed according to each load is maintained. The engine speed changes smoothly, and there is no undershoot in the idle speed or engine stall caused by undershoot.

In addition, the learning value and learning start value are memorized for each load,
The learning value corresponding to each load is prevented from becoming an extremely small value when updated by a lower limit guard based on the learning start value, so the idle speed will not undershoot extremely even when the load fluctuates. Therefore, there is no engine stall, and the driver is free to
It does not remind me of syllable students.

Furthermore, when updating the learning value, the lower limit guard is set to
Since the learning value at the start of feedback control is used as the learning start value, the learning start value is constantly updated, and therefore, various effects such as appropriately updating the learning value in response to changes in the engine over time can be obtained. be able to.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an engine and its peripheral equipment according to an embodiment to which the method of the present invention is applied, FIG. 2 is a block diagram similarly showing an electronic control circuit, and FIGS. 3 and 4 similarly show a control program. FIG. 5 is a graph illustrating the effects of the conventional example and the embodiment, and FIG. 6 is a graph illustrating the effects of the embodiment of the present invention. 1...Engine 12...Bypass path 13...IS CV 20...Electronic control circuit 21...Key switch 25...Air conditioner 29...Power steering device 30... CPU 33... Backup RAM Agent Patent attorney Tsutomu Sadatsu and 1 other person Figure 3 Figure 4 Figure 5 Time

Claims (1)

[Claims] A target value for the idle speed is determined according to the load applied to the engine during idle speed, a learned value for each load is stored in a non-volatile memory, and the target value is maintained during feedback control of the idle speed. In an idle rotation speed control method that aims to control the engine based on the operating state of the engine and the learned value,
In the non-volatile memory, a learned value when the vehicle is stopped and feedback control of the idle rotation speed is started is stored as a learning start value, and the learned value is changed to the learning start value by learning during feedback control. If the difference is greater than or equal to a predetermined value, an update process is performed in which a value obtained by subtracting the predetermined value from the learning starting value is set as the new learning value. Rotation speed control method.