JPS6183461A - Throttle valve controller for engine - Google Patents

Abstract

PURPOSE:To prevent a torque shock from occurring, by varying an opening variable speed in a throttle valve to an accelerator operating variable speed according to an engine speed. CONSTITUTION:An accelerator operated variable is detected by an accelerator detecting device 19. Opening in a throttle valve is controlled by a throttle valve opening controlling device 52 according to the accelerator operated variable. An engine speed is detected by an engine speed detecting device 27, and an opening variable speed in the throttle valve to an accelerator operating variable speed is controlled according to the engine speed. With this constitution, a torque shock is prevented from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is directed to a throttle pulverizer 6[1 device of an engine, in particular, a throttle valve that controls the intake air amount to a predetermined amount with respect to an accelerator operation amount indicating a required engine output. This invention relates to an improvement in which the degree of opening is electrically controlled.

(Prior Art) Conventionally, as a technique for controlling the amount of intake air supplied to the engine to a predetermined amount of intake air in response to the amount of accelerator operation indicating the required engine output, as shown in Japanese Patent No. 138235/1980, the accelerator The throttle valve opening control means is equipped with an accelerator detection means for detecting the amount of operation, and a throttle valve opening degree control means for receiving the output of the accelerator detection means and controlling the opening degree of the throttle valve according to the accelerator operation. It is known that feedback control is performed on the opening degree according to the amount of accelerator operation. Then, by supplying a fuel gauge to the engine so that the air-fuel ratio is set in advance according to the intake air m based on this throttle valve distance, the air-fuel ratio of the engine is set to the target value. It is something.

(Problems to be Solved by the Invention) However, with the above-mentioned conventional device, smooth acceleration performance cannot be achieved during sudden acceleration from a low engine rotation speed.
There is a problem that the acceleration feeling deteriorates. In other words, when accelerating rapidly from a low engine speed range, the throttle valve opens wide and the amount of intake air and fuel supply increases, causing a sudden rise in combustion pressure. The engine speed does not rise suddenly due to the rise of the engine speed, and as a result, the increase in engine speed and the increase in combustion pressure do not correspond well, causing torque shock in the engine and reducing the acceleration feeling. Due to the large change in the opening of the throttle valve, the vaporization and atomization characteristics of the fuel are greatly reduced, and good combustion is not ensured at the beginning of the second acceleration, resulting in so-called acceleration hesitation (sluggishness). There is a problem that smooth acceleration performance cannot be obtained. In addition, when accelerating suddenly from a high engine speed range,
Since the engine speed increases immediately due to large rotational inertia, the increase in engine speed corresponds well with the increase in combustion pressure, so torque shock does not occur, and the change in throttle valve opening is small. Since it is not large and has a large amount of intake air, the fuel vaporization and atomization characteristics are good and smooth acceleration performance can be obtained.

The present invention has been made in view of the above, and its purpose is to keep the speed of change in the opening of the throttle valve constant in response to the speed of change in accelerator operation when controlling the opening of the throttle valve by 6A as described above. By changing the engine speed appropriately according to the engine speed without changing the engine speed, the increase in combustion pressure is gradual and responds well to the increase in engine speed during sudden acceleration from a low engine speed range, thereby reducing engine torque shock. The object of the present invention is to suppress the deterioration of the vaporization and atomization characteristics of the fuel to ensure a good combustion state, thereby ensuring smooth acceleration performance and a good acceleration feeling even during any sudden acceleration.

(Means for solving the problem) In order to achieve the above object, the solving means of the present invention includes an accelerator detecting means 19 for detecting the amount of accelerator operation, and an accelerator detecting means 19 for detecting the amount of accelerator operation, as shown in FIG. In an engine throttle crushing device equipped with a throttle valve control means 52 that receives the output and controls the opening degree of the throttle valve according to the accelerator operation amount, the engine rotation speed is detected. A detecting means 27 receives the output of the engine speed detecting means 27, and changes the speed of change in the opening degree of the throttle valve relative to the speed of change in accelerator operation in accordance with the engine speed to be lower when the engine is running at low speed than when waiting for high engine speed. This configuration includes opening degree change speed changing means 38.

(According to the above configuration, in the present invention, when the engine suddenly accelerates from a low rotational speed range, the throttle valve gradually opens at a low opening change speed C relative to the accelerator operation amount.
The increase in the amount of intake air and fuel supply M, that is, the increase in combustion pressure, is slow and responds well to the slow increase in engine speed, thereby preventing the occurrence of torque shock and achieving good fuel vaporization and atomization. The characteristics are ensured and smooth acceleration performance is achieved.

In addition, during sudden acceleration from a high engine speed range, the throttle valve opens quickly at a high opening change rate, so that the combustion pressure increases quickly in response to the increase in engine speed.
Similarly, good acceleration feeling and smooth acceleration performance are achieved by 1q.

(Example) Hereinafter, an example of the present invention will be described based on the drawings from FIG. 2 onwards.

FIG. 2 shows the overall configuration of an engine control device according to an embodiment of the present invention, in which 1 is a four-cylinder engine, for example, and 2 is an engine with one end opening to the atmosphere via an air cleaner 3 and the other end opening to the engine 1. An intake passage 4 supplies intake air (air) to the engine 1, and an exhaust passage 4 has one end open to the engine 1 and the other end opened to the atmosphere to discharge exhaust gas from the engine 1.

Reference numeral 5 indicates an accelerator pedal that is depressed in response to engine output requirements, and reference numeral 6 indicates a throttle valve that is disposed in the intake passage 2 and controls the amount of intake air. There is no linkage relationship, and as will be described later, it is electrically controlled by the amount of depression of the accelerator pedal 5, that is, the amount of accelerator operation.

Reference numeral 7 denotes a throttle actuator comprising a step motor or the like that opens and closes the throttle valve 6.

Reference numeral 8 denotes a catalyst device which is interposed in the exhaust passage 4 and purifies exhaust gas.

Further, 9 has one end opening upstream of the contact vX device 8 of the exhaust passage 4 and the other end opening downstream of the throttle valve 6 of the intake passage 2, so that a part of the exhaust gas in the exhaust passage 4 is returned to the intake passage 2. An exhaust gas recirculation passage 10 is interposed in the middle of the exhaust gas recirculation passage 9 to control the amount of exhaust gas recirculation. The recirculation control valve 11 is a solenoid valve that controls the opening and closing of the recirculation control valve 10, which is a diaphragm device whose operation source is intake negative pressure.

On the other hand, reference numeral 12 denotes a fuel injection valve disposed downstream of the throttle valve 6 in the intake passage 2 to inject and supply fuel. The fuel tank 16 is connected to the fuel tank 16 through the fuel tank 16, and the fuel from the fuel tank 16 is supplied to the fuel tank 16. 31 is returned to the fuel tank 16 through a return passage with a fuel pressure regulator 17 interposed therebetween, so that fuel at a predetermined pressure is supplied to the fuel or'h! ) is supplied to the I valve 12.

In addition, 1 is an accelerator pedal position sensor as an accelerator detection means for detecting the depression state of the accelerator pedal 5, that is, the accelerator operation amount α, and 20 is disposed upstream of the throttle valve 6 in the intake passage 2 to detect intake air mQaR. 21 is an intake temperature sensor which is also arranged upstream of the throttle valve 6 in the intake passage 2 and detects the intake air temperature, 22 is a throttle position sensor which detects the opening of the throttle valve 6, and 23 is an engine cooling water sensor. Warm 1
2TW, a water temperature sensor 24, which is disposed upstream of the catalyst device rI18 in the exhaust passage 4, and a 02 sensor, which detects the air-fuel ratio λ of the engine 1 from the oxygen concentration component in the exhaust gas; 25, the recirculation and flow control valve 1; -O is a recirculation/flow sensor that detects the exhaust gas recirculation time, and these detection signals 19 to 25 are input to a control unit 26 consisting of an analog computer or the like, and the control unit 26
Accordingly, the throttle actuator 7, solenoid valve 11, and fuel injection valve 12 are controlled. In general, an igniter 27 is input-connected to the control unit 26, and inputs a signal indicating the number of ignitions, that is, the engine rotational speed NO, thereby controlling the engine rotational speed detection means. Further, a dust distributor 28 and two batteries are connected as inputs to the control unit 26, and the ignition timing and the battery voltage Va ((
Entering words.

Next, move the (¥:rib) of the control unit 26 to the third
This will be explained using figures. Note that FIG. 3 shows the case of a four-cylinder engine.

In FIG. 3, first, to describe the throttle valve opening control system, MAl is a target supply Qa+ of air to be supplied to the engine 1, which is set so that the air-fuel ratio is set in advance for the accelerator operation amount α. The first map receives the output from the accelerator pedal position sensor 19 and sets the target air fiQaj to be supplied to the engine 1 according to the accelerator operation amount α. MA2 is the minimum air ffi Q all in order to achieve the air-fuel ratio necessary for idle up with respect to the engine cooling water temperature 1j[Tw
is set in the second map, which receives the output from the water temperature sensor 23 and sets the minimum air amount Qam for water temperature correction according to the engine coolant temperature Tw.

31 is the first map MAI and the second map MA2.
is a maximum value selection circuit which receives each output and selects the maximum value Qa2 of the target air flQa+ determined by the first map MAI and the minimum air amount QalIl for water temperature correction determined by the second map MA2; The above target air fftQa
+ is lower than the minimum air amount for water temperature correction Qa+n, the minimum air amount for water temperature correction flI Q a to increase the idle
m is selected to ensure good engine drivability. Moreover, MA3 is the maximum air fftQa determined by the engine speed NO with respect to the engine speed Ne.
This is the third map in which M is set, which receives the output from the igniter 27 and sets the maximum air ffiQaM according to the engine rotational speed Ne. 32 receives each output of the maximum value selection circuit 31 and the third map MA3, and selects the maximum air ff1 determined by the maximum value selection circuit 31.
Maximum air mQa obtained from Qa2 and third map MA3
The minimum value selection circuit selects the minimum value Qa3 among M, and when the target air air ff1Qa1 exceeds the maximum air mQaM determined by the engine speed Ne, the throttle valve 6 is fully open to allow intake. Since it is meaningless to set the target value to an amount greater than the air loss, by selecting the maximum air ff1QaM and limiting the maximum value, a full open signal corresponding to the fully open throttle valve 6 is output to the subsequent stage. ing. As described above, the target air mQa3 is given to the accelerator operator α in consideration of the correction for the engine cooling water temperature F3Tw and the correction for the maximum air amount when the throttle valve 6 is fully open determined by the engine speed Ne.
is found.

Further, 33 receives the output from the minimum value selection circuit 32, and selects the target air ff1Qa3 at the engine rotational speed Ne.
The intake air ff1Ac+ per cylinder in a 4-cylinder engine is calculated using a divider that divides by the value doubled (NeX2). 34 receives the output from the divider 33 and calculates the intake mAc1 per cylinder of the engine by an acceleration correction coefficient KA c c for the elapsed time t from the start of acceleration determined by the 10th map MAIG when the engine 1 is accelerating. A multiplier that calculates the target intake chamber Δc2 by multiplying and correcting it is designed to improve acceleration performance by correcting and adding the itl suspension of the target intake air ff1Ac+, and the detection during engine acceleration is performed by the zone determination module described below. 51, for example, the following acceleration correction conditions ■ Engine cooling water temperature TV<, t°C ■ Rate of change of target air mQa1 with respect to time dQa 1
/dt>β ■ Engine rotation @Ne<n (β, n are predetermined values corresponding to high engine rotation) This is performed by determining that the following is satisfied. , MA4
and MA5 are the target intake air ffi for the engine speed Ne when exhaust recirculation is stopped and during exhaust recirculation, respectively.
The fourth and fifth maps set the throttle valve opening θ1 or θ1e that should be A C2, and both maps M
A4. MA5 is a recirculation switch 3 which is switched between when exhaust recirculation is stopped and when exhaust recirculation is performed by a signal from the recirculation sensor 25.
5, receives the output from the multiplier 34, and selects the target intake air ff1Acz and the smooth throttle valve opening θ1.
Alternatively, θIE is set. Further, 36 is an intake air amount feedback correction module, and the multiplier 34
While receiving the target intake air ff1Ac2 signal from
The above air 70 - actual air ff actually measured by the meter 20
1QaR and engine rotation *Ne, the actual intake air ff1AcR per cylinder calculated from the actual air ff1QaR and the engine rotation speed Ne is compared with the target intake air aAcz, and the throttle valve is opened according to the deviation. Feedback correction coefficient Ca for feedback correction of degree
This is to calculate FB. Rani, 37 is the fourth above.
Or 5th map MA4. 5 and the intake air amount feedback correction module 36, the map MA4. Target throttle valve opening θ1 determined by MA5
Or θIE is calculated by the intake m feedback correction module 36.
The signal of the target throttle valve opening θ2 corrected by the multiplier 37 is applied to the eleventh map M, which will be described later.
An is output to the throttle actuator 7, and the opening degree of the throttle valve 6 is set to the target throttle valve opening degree θ2.
controlled by. As described above, the throttle valve opening control means 52 receives the output of the accelerator pedal position sensor 19 and controls the opening and closing of the throttle valve 6 according to the accelerator operation amount α to achieve the target opening θ2.

An 11th map MA11, which is very important in the configuration of the present Bimei, is arranged after the multiplier 37.
The map MAI+ increases as the engine speed Ne increases. Throttle valve 6 for accelerator operation change speed
The opening change speed vth of the throttle valve 6 is set, and the operating speed of the throttle actuator 7 is determined based on the opening change speed yth of the throttle valve 6 selected here. As described above, in response to the output from the igniter 27, the opening change speed gVth of the throttle valve 6 relative to the accelerator operation change speed is changed to be lower at low engine speeds than at high engine speeds according to the engine speed NO. This constitutes a degree change speed changing means 38. Specifically, the opening change speed changing means 38 is constituted by, for example, an integral (having several layers), and changes the opening change speed of the throttle valve 6 by changing the integral constant according to the engine rotation speed Ne. The rate of change vth is changed.

Next, the fuel supply ffi till tn in FIG.
To describe the system, Ms is the sixth map in which the target first shift Qf+ of fuel to be supplied to the engine 1 is set so that the air-fuel ratio is set in advance for the accelerator operation amount α, and the accelerator pedal position In response to the output from the sensor 19, the target fuel mQfI to be supplied to the engine 1 is set according to the accelerator operation amount α. May
is the minimum temperature F31ffi with respect to the engine cooling water temperature Tw so that the air fuel ratio required for idle up is obtained with respect to the air amount Qam set in the second map MA2.
A seventh map in which Qfm is set, and water temperature sensor 2
3, the minimum fuel amount Qfm for water temperature correction is set according to the engine cooling water temperature U T w. 39 receives the respective outputs of the sixth map Mss and the seventh map May, and outputs the target fuel iQf, which is determined by the sixth map Mas.
This is a maximum value selection circuit that selects the maximum value Qf2 of the minimum fuel amount Qfm for water temperature correction obtained in the seventh map M87, and when the target fuel mQf+ is lower than the minimum fuel amount ffiQfm for water temperature correction, the idle up Therefore, the minimum fuel mQfm for water temperature correction is selected to ensure good engine operability. Furthermore, Maw is the eighth map in which the maximum fuel mQfM for the engine speed NO is set so that the maximum air ffiQaM set in the third map MA3 becomes the target air-fuel ratio set in advance.
The maximum fuel amount QfM is set according to the engine rotation @Ne. 40 receives each output of the upper iSa maximum value selection circuit 39 and the eighth map Mss, and selects the maximum fuel MQfz determined by the maximum value selection circuit 3 and the maximum fuel fftQfM determined by the eighth map Mea. This is a minimum value selection circuit that selects the minimum value Qf3, and when the target fuel ff1Qf1 exceeds the maximum fuel amount QfM determined by the engine speed Ne, that is, as described above, the When the maximum air amount QaM is exceeded, the throttle valve 6
When the target 1n is greater than the amount of air that can be taken in at full throttle, the maximum air ffiQaM is selected and the maximum fuel ffiQIM is selected to set the preset target airflow for the intake air supplied to the engine 1. The number of the sixth map Me5 (vote value Qf+) is corrected so that the fuel ratio becomes the same.As in the case of the air amount, the accelerator operation amount α is corrected for the engine cooling hydrogen degree Tw. A target fuel amount Qf3 is determined in consideration of correction to the maximum fuel amount for all throttle valves 6 determined by the engine speed Ne.

Then, the target fuel level Qf from the maximum value selection circuit 40 is
The s signal is transmitted to the remover 41, the first to third multipliers 42 to 44,
It is output to the fuel injection valve 12 via the fuel cutter 1 to the switch 45 and the fuel injection valve correction circuit 46. The evaluator 41 receives the output from the minimum value selection circuit 40, divides the target fuel ff1Qr3 by the engine rotational speed Ne assuming that fuel is injected into two cylinders at the same time, and calculates the fuel supply fiQfi per cylinder. It is something to do. Further, the first multiplier 42 converts the target fuel supply @ Ml Q f i obtained by the denumbing device 41 into a water temperature correction coefficient CTW for the engine cooling water temperature Tw obtained from the ninth map Mss.
and the target fuel supply ff by multiplying and correcting by the enrichment correction coefficient CER obtained by the enrichment correction module 47.
1Qfi+ is calculated. The enrichment correction module 47 performs enrichment correction to increase the fuel supply amount by, for example, 8% when the intake air ff1Ac+ relative to the engine speed Ne is in the enrichment line region based on a zone signal from a zone determination module 51 to be described later. It outputs a coefficient CεR (for example, 1.08).

Further, the second multiplier 43 converts the target fuel supply ff1Qfi obtained by the first multiplier 42 into the learning correction coefficient C5TD' obtained by the fuel learning correction module 48? '
The target fuel supply ffl Q f i 2 is calculated by performing the multiplication correction. The fuel learning correction module 48 determines whether fuel feedback correction conditions are satisfied in the fuel feedback correction module 49 based on the zone signal from the zone determination module 51 and the fuel feedback correction coefficient CfFB signal from the fuel feedback correction module 49, which will be described later. After that, for example, when more than 2 seconds have passed, set the fuel engineering concavity correction fault C5vo to its initial value = 1.0, and then calculate the following formula % peak value of CfFe + past 8 CfFe (D bottom le) / 16-1.1, it is sequentially updated and output.

Further, the third multiplier 44 multiplies and corrects the target fuel supply fiQfiz obtained by the second multiplier 43 by the fuel feedback correction coefficient CfFs obtained by the fuel feedback correction module 49 to obtain the target fuel supply ff1Qf.
This is to calculate i3. This fuel feedback correction module 49 is based on the zone signal from the zone determination module 51 and the air-fuel ratio λ signal from the 02 sensor 24, for example, under the following conditions: ■ Engine cooling water temperature Tw>60°C ■ Intake air ff1Ac+ ≧10 of the cylinder stroke volume %■
When the intake air ff1Ac+ with respect to the engine rotational speed Ne is outside the enrich line and the tunnel cut zone. ■ When the 02 sensor 24 is active, the fuel feedback correction coefficient CfFa (for example, 0.8 ≦
Cfps≦1.25, the proportional constant P-0.06 and the integral constant 1-0.05/sea) are output.

Furthermore, the opening and closing of the twin cut switch 45 is controlled by an output signal from the twin cut control module 50. Based on the zone signal and target intake mAC+ signal from the zone determination module 51, the twin air cut control module 50 operates under, for example, the following conditions: ■ Engine cooling water temperature Tw>60°C ■ Intake fftAc+<10% of cylinder stroke volume■
When the engine rotational speed Ne>11000 rp is satisfied, control is performed to listen to the twin cut switch 45 to cut fuel injection. Here, the zone determination module 51 determines the engine rotation speed Ne, the target intake air ff
1Ac+, engine cooling water temperature Tw, and air-fuel ratio A, condition determination signals (zone signals) for each of the control modules 47 to 50 are created.

Furthermore, the fuel injection valve correction circuit 46 includes the third fuel injection valve correction circuit 46.
Upon receiving the target fuel supply amount Qfi3 signal from the multiplier 44 and the battery voltage VB signal from the two batteries, the pulse signal as the target fuel supply amount signal to the fuel injection valve 12 is corrected according to the battery voltage VB, and the fuel It outputs to the injection valve 12. As described above, the fuel injection valve 12 is driven for a predetermined period of time in synchronization with ignition, and the fuel supply amount is controlled to the target value.

Therefore, in the above embodiment, during sudden acceleration from a low engine speed range, the opening change rate yth of the throttle valve 6 relative to the accelerator operation change rate is equal to the 11th map MA.
It is initially set low by I+, and then gradually set high as the engine speed Ne increases, and the throttle valve 6 hears a louder sound as the throttle actuator 7 gradually increases the opening change speed. As a result, the intake air amount to the engine 1 and the fuel injection amount tJJ gradually increase, and the increase in combustion pressure corresponds to the slow increase in engine speed (1=1), so torque shock does not occur. There is no problem, and a good acceleration feeling is achieved by 1q. At the same time, the gradual upper limit of the opening degree change 3a degree of the throttle valve 6 ensures good vaporization and atomization characteristics of the fuel, and smooth acceleration performance is exhibited.

In addition, during sudden acceleration from a high engine speed range, the opening change rate v of the throttle valve 6 relative to the accelerator operation change rate
th is selected at a high speed from the beginning by the 11th map MAI+, the throttle valve 6 opens quickly, and the combustion pressure immediately rises, but the engine speed also rises rapidly due to its large rotational inertia, causing the combustion pressure to rise. Therefore, torque shock will not occur. Moreover, since the range of change in the throttle valve 6 is smaller than that during rapid acceleration from the engine's low speed range and the amount of intake air is large, the fuel vaporization and atomization characteristics are good and smooth acceleration performance can be obtained. In short, as shown in Fig. 4, when there is sudden acceleration from low engine speed, the increase in throttle valve rAU is slower in response to the increase in accelerator operation amount than when the engine is at high speed. This allows for smooth acceleration performance without torque shock.

In addition, target air 4 and target fuel ω are respectively determined for the accelerator operation amount α, and based on the determined target (1α), the intake air amount and fuel supply amount are adjusted to target 1 in parallel simultaneously. By being controlled so that the intake air amount and fuel supply amount change to the target F value at the same time without any time lag in response to changes in the accelerator operation amount α, the The air-fuel ratio of the engine can be precisely controlled to the target air-fuel ratio without causing a delay in fuel response, thereby improving the acceleration performance and driving performance of the engine.Moreover, the accelerator operation amount α ilJ at the same time so that the intake air amount and fuel supply amount become the preset air-fuel ratio.
Therefore, the target air-fuel ratio can be accurately controlled without requiring feedback control, and the control can therefore be simplified.

In the above embodiment, the opening change speed changing means 38 is adjusted so that the opening change speed vth of the throttle valve 6 is equal to the engine rotation f!
Although the present invention is configured to change steplessly according to lNe, the present invention is not limited to this. For example, the n degree change speed yth of the throttle valve 6 may be set low in a low engine speed range, and high in a high engine speed range. (The setting may be changed in two stages or in stages.)

(Effects of the Invention) As explained above, according to the present invention, when the throttle valve opening is changed by $Q 12n'' according to the accelerator operation amount, the opening change rate of the throttle valve relative to the accelerator operation change rate is Since the engine speed is changed to a lower value at low engine speeds than at high engine speeds according to the engine speed, the increase in combustion pressure and the increase in engine speed correspond in a 1:1 ratio even during sudden acceleration. In addition to preventing the occurrence of drudgery, good fuel vaporization and atomization characteristics are ensured, and acceleration displacement is suppressed, thereby ensuring a good acceleration feeling and improving acceleration performance. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention. 2 to 4 show an embodiment of the present invention, in which FIG. 2 is a schematic diagram of the entire groove bottom, FIG. 3 is a block diagram showing the operation flow of the control unit, and FIG. 4 is an explanatory diagram of the operation. 1...Engine, 5...Accelerator pedal, 6...
Throttle valve, 7... Throttle actuator, 1
1...Accelerator pedal position sensor, 26...
Control unit, 27...Igniter, 38.
. . . Opening degree change speed changing means, 52 . . . Throttle valve opening degree controlling means.

Claims (1)

[Claims] (1) Accelerator detection means for detecting the amount of accelerator operation;
In an engine throttle valve control device comprising a throttle valve opening control means that receives the output of the accelerator detection means and controls the opening of the throttle valve according to an accelerator operation amount, the engine rotation detects the engine rotation speed. and an opening that receives the output of the engine rotation speed detection means and changes the opening change rate of the throttle valve relative to the accelerator operation change rate in accordance with the engine rotation speed to be lower when the engine is running at low speeds than when the engine is at high speeds. 1. A throttle valve control device for an engine, comprising: degree change speed changing means.