JP2011153547A - Fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection device immediately restarting an internal combustion engine even if a detected and stored stop crank angle reaches a low-accuracy value or an erroneous detection value. <P>SOLUTION: When starting the engine, after starting angle momentum L1 is detected, that is, second fuel injection timing and the second amount of fuel injected are determined based on the starting angle momentum L1. Thereby, even if the stored stop crank angle is the erroneous detection value or the like, it becomes possible to optimize the fuel injection timing and the amount of fuel injected after the starting angle momentum L1 is detected and to immediately restart the engine. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel injection device for injecting and supplying fuel to a diesel-type internal combustion engine, and in particular, to a vehicle equipped with a system (idle stop system) for automatically stopping and starting the internal combustion engine during idling operation. It is effective.

  The idle stop system is a system that automatically stops the internal combustion engine when a vehicle such as a signal waiting is stopped for a short time, and when a travel start command is issued (for example, when an accelerator pedal is depressed or This is a system that suppresses wasteful fuel consumption by automatically restarting the internal combustion engine when the brake is released (see, for example, Patent Document 1).

  By the way, in the 4-cycle reciprocating diesel engine, fuel is injected and supplied into the cylinder (combustion chamber) based on the position of the crankshaft (crank angle), that is, the position of the piston. After the crankshaft is rotated once (360 degrees) or more and the crankshaft reference position is detected (cylinder discrimination), fuel injection timing control is started based on the detected reference position.

  However, in the above-described normal start control, fuel injection control for starting the engine is started after cylinder discrimination is completed. Therefore, if this start control is directly adopted in the idle stop system, the time required for restart is reduced. It is difficult to shorten, and there is a risk that the driver may feel uncomfortable.

  On the other hand, after stopping the fuel supply to the cylinder, the crankshaft stop position (stop crank angle) when the rotation of the crankshaft actually stops is stored, and at the time of restart, the stored stop is stored. There is known an idle stop system that controls the timing of injecting fuel based on the position, thereby reducing the time required for restart by starting fuel injection control without performing cylinder discrimination. .

  However, since an internal combustion engine needs to compress a gas such as air that is a working fluid, after the fuel supply to the cylinder is stopped and before the rotation of the crankshaft actually stops, the compression reaction force causes In some cases, a phenomenon (reverse phenomenon) in which the crankshaft rotates in a direction opposite to the conventional rotation direction may occur.

  When the reverse rotation phenomenon occurs, it becomes impossible to accurately grasp the stop position of the crankshaft, and it becomes impossible to execute the fuel injection control at an accurate timing. Need to figure out.

  Thus, for example, in the invention described in Patent Document 2, the interval between pulses detected by the angle detection crank angle sensor (“interval from rising pulse to falling pulse” and “interval from falling pulse to rising pulse”). The reversal phenomenon is detected based on the change of.

JP 2006-63832 A JP 2008-14287 A

  However, if the detected and stored stop crank angle is a value with low accuracy or a false detection value, it is difficult to shorten the time required for restart because fuel cannot be supplied at an appropriate injection timing and injection amount. Become. In particular, in a diesel internal combustion engine of a type in which fuel is directly injected into the combustion chamber, restart is required when the fuel injection timing and injection amount are inappropriate, coupled with the lack of an ignition device. Difficult to reduce time.

  In view of the above points, the present invention can restart the internal combustion engine promptly even if the detected / stored stop crank angle is a value with low accuracy or a false detection value. An object is to provide a fuel injection device.

  In achieving the above object, according to the present invention, if the stored stop crank angle is an erroneously detected value or the like, the fuel injection timing and the fuel injection amount become inappropriate, and usually sufficient combustion pressure is generated. The following solution was adopted, focusing on the point that sufficient torque is not generated on the crankshaft.

  That is, in the first aspect of the invention, a fuel injection device that injects and supplies fuel to a diesel internal combustion engine (50), and an injector (30) that injects and supplies a fuel chamber of the internal combustion engine (50); Stop crank angle storage means (40) for detecting the rotation angle of the crankshaft of the internal combustion engine (50) and storing the rotation angle of the crankshaft when the internal combustion engine (50) stops, and torque generated on the crankshaft And a torque information detecting means (40) for detecting an information value (hereinafter referred to as a torque information value), and at the start of the internal combustion engine (50), fuel is injected from the injector (30). Based on the torque information value detected after the hour (hereinafter, this torque information value is referred to as the starting torque information value), the starting torque information value at the start of the internal combustion engine (50) is Characterized in that it comprises a starting time injection control means (40) for determining the fuel injection timing and fuel injection amount after when issued.

  Thus, according to the first aspect of the invention, when the internal combustion engine (50) is started, the fuel injection timing and the fuel injection amount after the start time torque information value is detected become the start time torque information value. Therefore, even if the stop crank angle stored in the stop crank angle storage means (40) is a false detection value or the like, the fuel injection timing and fuel after the start time torque information value is detected It becomes possible to optimize the injection amount, and to quickly restart the internal combustion engine (50).

  That is, in the conventional fuel injection device, after recognizing the crankshaft position (piston position) based on the stored stop crank angle, the rotational speed of the internal combustion engine and the temperature of the fuel (usually the temperature of the cooling water) ), The fuel injection timing and the fuel injection amount are determined, and the combustion state at the time of starting, that is, the torque (torque information value) generated in the crankshaft is not considered at all. However, even when sufficient combustion pressure is not generated, the fuel injection timing and the fuel injection amount are not optimized.

  On the other hand, in the invention according to claim 1, as described above, it is possible to optimize the fuel injection timing and the fuel injection amount after at least the detection of the starting torque information value. It becomes possible to restart the internal combustion engine (50) promptly.

Note that “when the internal combustion engine (50) is started” refers to a state before the starter device such as a starter motor is operated and combustion is stabilized to the extent that the internal combustion engine (50) can operate independently.
Further, “when the starting torque information value is detected” is preferably the time between the first fuel injection and before the second fuel injection. In the internal combustion engine, after the second fuel injection is performed and before the third fuel injection is performed, or after the third fuel injection is performed, the fourth fuel injection is performed. It may be a time between before.

  By the way, when the starting torque information value is equal to or smaller than a predetermined value that can be regarded as misfire, there is a possibility that the actually executed fuel injection timing is largely deviated from the appropriate fuel injection timing. Therefore, in such a case, for example, the crankshaft is rotated one rotation (360 degrees) or more to detect the reference position of the crankshaft (cylinder discrimination), and then the fuel injection is performed based on the detected reference position. It is better to control the timing.

  Therefore, in the invention described in claim 2, when the starting torque information value is equal to or less than a predetermined value that can be regarded as misfire, the prohibiting means (40) that prohibits the operation of the starting injection control means (40). ).

  In the invention according to claim 3, the start-time injection control means (40) has storage means in which a torque information value corresponding to the start-time torque information value is stored in advance. The injection control means (40) determines the fuel injection timing based on the difference between the torque information value stored in the storage means (hereinafter, this torque information value is referred to as normal torque information value) and the starting torque information value. And determining the fuel injection amount.

  Accordingly, in the invention according to the third aspect, the fuel injection timing and the fuel injection amount after the time when the starting torque information value is detected can be reliably optimized, so that the internal combustion engine ( 50) can be restarted.

  Specifically, as in the invention described in claim 4, when the torque information value is detected as the angular momentum of the crankshaft, and the starting torque information value is smaller than the normal torque information value, the starting torque information value It is desirable to increase at least the fuel injection amount as compared with the time before the detection.

  By the way, since the angular momentum is an integrated value of torque (a value obtained by integrating instantaneous torque with time), the ratio of errors included in the detected value can be reduced as compared with the case of directly detecting torque. For this reason, since it becomes possible to optimize the fuel injection timing and the fuel injection amount with higher accuracy than when the torque information value is torque, the internal combustion engine (50) can be restarted quickly. It becomes.

  Incidentally, the reference numerals in parentheses for each of the above means are examples showing the correspondence with the specific means described in the embodiments described later, and the present invention is indicated by the reference numerals in the parentheses of the above respective means. It is not limited to a specific hand or the like.

It is a conceptual diagram of the fuel-injection apparatus which concerns on embodiment of this invention. It is a flowchart which shows the starting control of the fuel injection apparatus which concerns on embodiment of this invention. It is a chart which shows the state at the time of a start in the engine using the fuel injection device concerning the embodiment of the present invention. (A) is a graph showing the relationship between the angular momentum difference and the fuel injection correction amount, and (b) is a graph showing the relationship between the angular momentum difference and the fuel injection timing correction amount.

In the present embodiment, the fuel injection device according to the present invention is applied to a fuel injection device for a diesel engine for a vehicle. Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1. Configuration of fuel injection device (see Fig. 1)
The fuel injection device 10 according to the present embodiment is a so-called pressure accumulation type (common rail type) fuel injection device. Specifically, as shown in FIG. 1, a feed pump 14, a high-pressure pump 16, a suction metering valve 18, a common rail 20, a pressure sensor 22, a pressure reducing valve 24, an injector 30, and an electronic control unit (hereinafter referred to as ECU). ) 40 and an electronic drive unit (hereinafter referred to as EDU) 42 and the like, and injects fuel into each cylinder of a 4-cylinder diesel internal combustion engine (hereinafter referred to as engine) 50.

  The feed pump 14 sucks fuel from the fuel tank 12 and supplies it to the high-pressure pump 16. The high-pressure pump 16 receives power from the engine 50 and adds the sucked fuel when the plunger reciprocates. It is a known pump that pressurizes.

  The suction metering valve 18 is provided on the suction side of the high-pressure pump 16 and adjusts the amount of fuel supplied to the common rail 20, whereby the pressure in the common rail 20 becomes the control target pressure in cooperation with the high-pressure pump 16. It adjusts to become.

  The high-pressure pump 16 according to the present embodiment operates with power from the engine 50, and thus cannot control the high-pressure pump 16 itself, but the operation (opening degree) of the intake metering valve 18 is Therefore, the amount of fuel supplied to the common rail 20 can be adjusted by controlling the operation of the intake metering valve 18.

  The common rail 20 is a stock pressure vessel that accumulates fuel pumped from the high-pressure pump 16 and holds the fuel pressure at a predetermined pressure corresponding to the engine operating state. The pressure sensor 22 is connected to the inlet side of the common rail 20. Pressure detecting means for detecting the pressure in the common rail 20.

  The pressure reducing valve 24 is an adjusting valve for adjusting the communication state between the common rail 20 and the fuel tank 12 side. The pressure reducing valve 24 is opened when the pressure in the common rail 20 abnormally rises, thereby This fuel is discharged to the fuel tank 12 side to reduce the fuel pressure in the common rail 20.

  The plurality of injectors 30 are fuel injection valves that are connected in parallel to the common rail 20 and supply high-pressure fuel accumulated in the common rail 20 to the combustion chambers of the cylinders. The control means is constituted by a well-known computer including rewritable nonvolatile storage means such as RAM and flash memory.

  The intake metering valve 18, the pressure reducing valve 24 and the injector 30 are controlled by the ECU 40. The injector 30 is not directly controlled by the ECU 40 but is indirectly controlled by the ECU 40 via the EDU 42 that drives the injector 30.

  In addition, the ECU 40 detects a rotation speed sensor S1 that detects the engine rotation speed, an accelerator sensor S2 that detects the depression amount of the accelerator pedal, a rotation speed sensor S3 that detects the rotation speed Ne of the engine, and a rotation speed of the high-pressure pump 16. Rotational speed sensor S4, vehicle speed sensor S5 for detecting vehicle speed, brake sensor S6 for detecting the depression amount of the brake pedal, crank angle sensor S7 for detecting the rotation angle of the crankshaft of the engine, water temperature for detecting the temperature of the engine cooling water Based on detection signals from various sensors such as the sensor S8 and the pressure sensor 22, the operating states of the engine 50 and the fuel injection device 10 are acquired.

  Then, in order to control the engine 50 to an optimum operating state, the ECU 40 controls the intake metering valve 18, the pressure reducing valve 24, and the injector according to a program stored in advance in the ROM or flash memory based on the acquired engine operating state. The energization (energization duty ratio) to 30 etc. is controlled.

  In addition, the crank angle sensor S7, for example, similarly to the crank angle sensor described in Patent Document 2, detects the interval between detected pulses ("interval from rising pulse to falling pulse" and "from falling pulse to rising pulse"). This is a type of MRE sensor that can detect a reverse phenomenon based on a change in the interval “).

2. Idle stop system 2.1. Outline of Idle Stop System The idle stop system according to the present embodiment is designed to perform fuel injection when the vehicle speed is equal to or lower than a predetermined speed and the brake depression amount is equal to or higher than a predetermined amount in order to suppress wasteful fuel consumption. To stop the engine 50 automatically and restart the fuel injection when a travel start command is issued (for example, when the accelerator pedal is depressed or the brake is released), and the starter motor (Not shown) The engine 50 is operated and the engine 50 is automatically restarted.

  In the idle stop system, after stopping the fuel supply to automatically stop the engine 50, the crank angle of the crankshaft when the rotation of the crankshaft of the engine 50 is actually stopped is detected by the crank angle sensor S7. The detected crank angle (hereinafter referred to as stop crank angle) is stored in the RAM, and at the time of restart, cylinder discrimination is performed by controlling the timing of fuel injection based on the stored stop crank angle. Without starting, fuel injection control is started.

2.2. FIG. 2 shows fuel injection control (starting control) executed when the engine is started during operation of the idle stop system. After the first fuel injection is performed, the second fuel injection is performed. It is a flowchart which shows the control performed before it is performed.

  A program for executing the start control (including the control shown in FIG. 2) is stored in a nonvolatile storage means such as a ROM of the ECU 40 or a flash memory, and is started when a travel start command is issued. It is executed by the ECU 40 and ends when the engine speed becomes equal to or higher than the predetermined speed and the combustion is stabilized to the extent that the engine 50 can operate independently.

  When the travel start command is issued, the start control is started, and the starter motor rotates and cranking is executed to restart the engine 50, which is obtained based on the stop crank angle stored in the RAM. First fuel injection based on crankshaft position (piston position), engine 50 (crankshaft) rotation speed or crankshaft angular velocity, and temperature of fuel and engine 50 (usually cooling water temperature) The timing and the fuel injection amount are determined, and the fuel injection is executed according to the determined fuel injection timing and the fuel injection amount (S1).

Hereinafter, determining the fuel injection timing and the fuel injection amount based on the position of the crankshaft, the number of revolutions, the temperature of the fuel and the coolant, etc. is referred to as normal start-up control.
Next, after the current angular momentum of the crankshaft (hereinafter, this angular momentum is referred to as starting angular momentum L1) is calculated (S5), the starting angular momentum L1 is a predetermined value that can be regarded as misfire. It is determined whether or not the value is equal to or less than the value (S10).

  When it is determined that the starting angular momentum L1 is equal to or less than the predetermined value (S10: YES), the second fuel injection timing and the fuel injection amount are determined by the normal starting control, and the determined fuel is determined. Fuel injection is executed according to the injection timing and the fuel injection amount (S30).

  In the present embodiment, the third fuel injection timing and the fuel injection amount are determined by the normal start-up control, and the engine rotation speed is equal to or higher than the predetermined rotation speed, so that the combustion is stabilized to the extent that the engine 50 can operate independently. When the start control ends.

  On the other hand, if it is determined that the starting angular momentum L1 is greater than the predetermined value (S10: NO), the normal angular corresponding to the same crank angle as the crank angle used to calculate the starting angular momentum L1. The momentum L2 is read from a nonvolatile storage means such as a ROM or a flash memory (S15), and the difference (L2−L1) between the normal angular momentum L2 and the starting angular momentum L1 is calculated (S20).

  Here, the normal angular momentum L2 is an angular momentum generated by the first fuel injection when an accurate stop crank angle is stored, and is a value obtained in advance by a test. The normal angular momentum L2 is stored in advance in a nonvolatile storage means such as a ROM or a flash memory as a value corresponding to each crank angle.

  Then, the second fuel injection timing and the fuel injection amount determined by the normal start time control are corrected based on the angular momentum difference calculated in S20, whereby the second fuel injection timing and the fuel injection amount are corrected. Is determined (S25), fuel injection is performed according to the determined second fuel injection timing and fuel injection amount (S30).

3. FIG. 3 is a chart showing changes in the engine speed, torque T, and angular momentum L when the engine 50 using the fuel injection device 10 according to this embodiment is started. .

  In the engine 50 according to the present embodiment, the top dead center (TDC) of the compression stroke is the first cylinder (# 1) → the third cylinder (# 3) → the fourth cylinder (# 4) → the second cylinder ( Since # 2) is switched in order of the first cylinder (# 1), in the normal start-up control, the fuel injection timing of each cylinder is determined based on the position of the top dead center of the compression stroke.

  In a four-cycle engine, each stroke is converted into a crank angle in the order of intake stroke → compression stroke → explosion stroke → exhaust stroke, and is repeated in units of 180 degrees. Therefore, torque T and engine speed are also about 180 degrees. In particular, the torque T varies greatly between the compression stroke and the explosion stroke. However, since the angular momentum L is an integrated value of the torque T (a value obtained by integrating the instantaneous torque with time), as shown by the following mathematical formula, the angular momentum L changes with time.

T = r × F (Formula 1)
F = m · a Equation 2
Where T is a vector quantity indicating torque, F is a vector quantity indicating a force acting on the mass point, r is a position vector quantity up to the mass point, and symbol x is a vector product. Further, m is the mass of the mass point (scalar amount), and a is a vector amount indicating acceleration.

From Equations 1 and 2, T = r × (m · a) = m (r × dv / dt).
Here, v represents a vector quantity indicating the speed.

  Further, since the angular momentum L is expressed by L = r × m · v, the integrated value of the torque T (the value obtained by integrating the instantaneous torque with time) is the angular momentum L. Thus, the angular momentum L is a parameter having technical significance as an information value relating to torque having a correlation with the torque T, that is, a torque information value.

  In the present embodiment, at the time of starting the engine 50, the time when the starting angular momentum L1 is detected, that is, the second fuel injection timing and the fuel injection amount are determined based on the starting angular momentum L1. Therefore, even if the stored stop crank angle is an erroneously detected value or the like, it becomes possible to optimize the fuel injection timing and the fuel injection amount after the start angular momentum L1 is detected, and promptly The engine 50 can be restarted.

  That is, in the conventional fuel injection device, after recognizing the crankshaft position (piston position) based on the stored stop crank angle, the rotational speed of the internal combustion engine and the temperature of the fuel (usually the temperature of the cooling water) The fuel injection timing and the fuel injection amount are determined on the basis of the fuel injection timing and the fuel injection timing and the fuel injection amount. However, even when sufficient combustion pressure is not generated, the fuel injection timing and the fuel injection amount are not optimized.

  On the other hand, in the present embodiment, as described above, it is possible to optimize the fuel injection timing and the fuel injection amount at least after the start time angular momentum L1 is detected. Can be restarted.

  That is, in this embodiment, the angular momentum corresponding to the starting angular momentum L1, that is, the normal angular momentum L2 is stored in advance, and based on the difference between the normal angular momentum L2 and the starting angular momentum L1, The fuel injection timing and the fuel injection amount are determined.

  If the fuel injection timing and the fuel injection amount at the start are inappropriate, normally, sufficient combustion pressure is not generated and sufficient torque is not generated on the crankshaft. Therefore, the starting angular momentum L1 is the normal time angle. It becomes smaller than the momentum L2.

  Therefore, in the present embodiment, as shown in FIG. 4A, when the starting angular momentum L1 is smaller than the normal angular momentum L2, the time before the starting angular momentum L1 is detected, that is, the normal startup. The fuel injection amount is increased as compared with the first fuel injection amount determined by the control.

  In the present embodiment, the fuel injection correction amount is increased in accordance with the increase in the angular momentum difference until the angular momentum difference reaches a predetermined value, but when the angular momentum difference exceeds the predetermined value, the fuel injection correction amount is increased. Even if it is increased, no effect can be expected. Therefore, the fuel injection correction amount is almost constant regardless of an increase in the angular momentum difference.

Incidentally, when the angular momentum difference becomes negative, that is, when the starting angular momentum L1 becomes larger than the normal angular momentum L2, the fuel injection correction amount becomes 0, and the correction is not substantially executed.
Further, since the fuel injection correction amount increases as the angular momentum difference increases (see FIG. 4A), in principle, the fuel injection timing is advanced (accelerated) (according to the timing). 4 (b)), the fuel injection timing also varies depending on the stop crank angle and the cooling water temperature. Therefore, even if the angular momentum difference increases, the fuel injection timing may be delayed (timing is delayed). .

  As described above, in the present embodiment, the fuel injection timing and the fuel injection amount after the time when the starting angular momentum L1 is detected can be surely optimized, so that the engine 50 is restarted promptly. It becomes possible.

  By the way, when the angular momentum L1 at the time of start is equal to or less than a predetermined value that can be regarded as misfire, there is a possibility that the actually executed fuel injection timing is greatly deviated from the appropriate fuel injection timing. Therefore, in such a case, it is better to execute the normal start control.

Therefore, in the present embodiment, when the angular momentum L1 at the start is equal to or less than a predetermined value that can be regarded as misfire, calculation of the angular momentum difference and correction of the fuel injection amount and the like are prohibited.
By the way, as described above, the angular momentum is an integrated value of torque (a value obtained by integrating the instantaneous torque with time), so that the ratio of error included in the detected value is reduced as compared with the case where the torque is directly detected. be able to.

  For this reason, compared with the case where the torque information value is torque, the fuel injection timing and the fuel injection amount can be optimized more accurately, so that the engine 50 can be restarted promptly.

(Other embodiments)
In the above-described embodiment, the present invention is applied to the engine restart while the idle stop system is operating. However, the application of the present invention is not limited to this, and the driver starts the engine 50 manually. It can also be applied to.

In the above-described embodiment, the present invention is applied to the common rail fuel injection device, but the application of the present invention is not limited to this.
In the above-described embodiment, the angular momentum is used as the torque information value. However, the present invention is not limited to this, and for example, the torque T may be used as the torque information value.

  Further, in the above-described embodiment, the third fuel injection timing and the fuel injection amount are determined by the normal start-up control, but the present invention is not limited to this, and for example, the next fuel after the fuel injection The angular momentum L1 is calculated during the time until the injection, and the normal angular momentum L2 and the angular momentum L1 corresponding to the angular momentum L1 are compared to determine the next fuel injection timing and the fuel injection amount. The operation may be repeated until the start of the engine 50 is completed.

  Further, the present invention is not limited to the above-described embodiment as long as it matches the gist of the invention described in the claims.

10 ... Fuel injection device, 12 ... Fuel tank, 14 ... Feed pump,
16 ... High pressure pump, 18 ... Suction metering valve, 20 ... Common rail, 22 ... Pressure sensor,
24 ... Pressure reducing valve, 30 ... Injector, 50 ... Engine, S1 ... Speed sensor,
S2 ... Accelerator sensor, S3 ... Revolution sensor, S4 ... Revolution sensor,
S5: Vehicle speed sensor, S6: Brake sensor, S7: Crank angle sensor,
S8: Water temperature sensor.

Claims (4)

A fuel injection device for injecting and supplying fuel to a diesel internal combustion engine,
An injector for injecting and supplying a fuel chamber of the internal combustion engine;
Stop crank angle storage means for detecting the rotation angle of the crankshaft of the internal combustion engine and storing the rotation angle of the crankshaft when the internal combustion engine stops;
Torque information detecting means for detecting an information value relating to torque generated in the crankshaft (hereinafter, this information value is referred to as a torque information value);
The internal combustion engine is based on the torque information value detected when the internal combustion engine is started and after the fuel is injected from the injector (hereinafter, this torque information value is referred to as a startup torque information value). A fuel injection device comprising: a fuel injection timing control unit that determines a fuel injection timing and a fuel injection amount after the start time torque information value at the time of engine startup is detected.   2. The fuel according to claim 1, further comprising: prohibiting means for prohibiting operation of the start-time injection control means when the start-time torque information value is equal to or less than a predetermined value that can be regarded as misfire. Injection device. The start-time injection control means has storage means in which the torque information value corresponding to the start-time torque information value is stored in advance.
Further, the starting injection control means is based on a difference between the torque information value stored in the storage means (hereinafter, this torque information value is referred to as a normal torque information value) and the starting torque information value. The fuel injection device according to claim 1, wherein the fuel injection timing and the fuel injection amount are determined. The torque information value is an angular momentum of the crankshaft,
Further, when the starting torque information value is smaller than the normal torque information value, the starting injection control means sets at least a fuel injection amount as compared with the time before the starting torque information value was detected. The fuel injection device according to claim 3, wherein the fuel injection device is increased.