Patent Application
20170051696
The present invention relates to a control device for electromagnetic fuel injection valve.
Conventionally, a maximum injection quantity and a minimum injection quantity is defined as indices indicating a performance of a fuel injection valve for injecting fuel into an internal combustion engine. The quantity of fuel that a fuel injection valve can inject by keeping valve-opening of the fuel injection valve for a prescribed period (for example, one second) is defined as the maximum injection quantity. Injecting a larger injection quantity in a unit time is desired for requirement of the maximum injection quantity, and it can be addressed by increasing, as a determination factor, a setting value of a part represented by a valve-body lift quantity (moving quantity) in the fuel injection valve or a nozzle diameter provided in a distal end of the fuel injection valve. Meanwhile, the minimum injection quantity indicates the smallest injection quantity with which the fuel injection valve can stably inject, and the injection quantity is desirably required to be smaller. By the way, the injection quantity with which injection can be stably performed can be inevitably reduced by shortening a valve-opening instruction time for the fuel injection valve. However, the injection quantity varies between injection valves with identical specifications and identical driving instruction time. Therefore, the variation in the injection quantity falling within a prescribed range is set as a requirement.
In recent years, technological development for widening the range (hereinafter referred to as a dynamic range) between the maximum injection quantity and the minimum injection quantity that has been already mentioned is actively made for an electromagnetic fuel injection valve of a direct-injection internal combustion engine in particular. Particularly, so-called half-lift control in which an active fuel injection is controlled from a state where the valve body of the fuel injection valve is not fully open is catching attention for further reducing the minimum injection quantity while keeping the conventional maximum injection quantity.
For example, in the technique of PTL 1, the half-lift control is realized by improving the mechanism of the fuel injection valve such that the lift quantity of the valve body can be fixed to two levels of a high lift and a low lift and by setting a driving current of the fuel injection valve for each level.
In the technique of PTL 2, half-lift control of an electromagnetic fuel injection valve is realized by performing control to supply a valve-opening current for opening the valve body against a fuel pressure upstream of the fuel injection valve for a short period of time to start closing the valve before reaching a state where the valve body is fully open such that the lift quantity of the valve body is in a parabolic motion.
PTL 1: JP 2002-266722 A
PTL 2: JP 2013-2400 A
With the technique of PTL 1, it is necessary to improve the mechanism of the fuel injection valve to realize the half-lift control, and the lift quantity in a half-lift region cannot be changed continuously.
In addition, in the technique described in PTL 2, a specific scheme to continuously changing the lift quantity in the half-lift region in which the fuel injection is finished before the valve body reaches a full-lift state is neither taken into consideration. Further, even if the lift quantity in the half-lift region is variably controlled on the basis of the technique described in PTL 2, a problem that the relationship of a fuel injection quantity with an injection instruction period is different from a full-lift region in which a fuel injection instruction is stopped after the valve body reaches the full-lift position will arise.
An object of the present invention is made in consideration of such a problem and lies in making flow-rate properties in a half-lift region to be closer to flow-rate properties in a full-lift region to improve the controllability of a minute fuel injection quantity.
To solve the problem described above, a control device of the present invention is a control device for electromagnetic fuel injection valve that supplies a driving current to a solenoid to open a valve body with a magnetic force and injects a fuel into an internal combustion engine, and is characterized in that a supply period of the driving current includes a peak current supply period in which a magnetic force necessary for a valve-opening action of the valve body is generated, and
a lift quantity adjustment period in which a current lower than the peak current is passed for a prescribed period after the peak current supply period. The control device controls, in accordance with a length of the lift quantity adjustment period, at least one of a lift quantity of the valve body, an actual valve-opening period before the valve body reaches a full-lift position, and a fuel injection quantity injected into the internal combustion engine before the valve body reaches the full-lift position.
According to the present invention, it is possible to make the relationships of a fuel injection quantity with an injection instruction period of a half-lift region and a full-lift region closer to each other, and thus it is possible to improve the controllability of a minute fuel injection quantity.
Exemplary embodiments of the present invention will be described below with reference to drawings.
In the present exemplary embodiment, a normally-closed electromagnetic fuel injection valve will be described as a fuel injection valve 108 controlled by the fuel injection valve control device 101. The fuel injection valve 108 drives a valve body in an opening direction by supplying a current to a solenoid to generate a magnetic attractive force and closes the valve in accordance with, for example, a spring force or a supplied combustion power by cutting off the current supplied to the solenoid.
The configuration of the fuel injection valve control device 101 will be described herein. The fuel injection valve control device 101 includes a high voltage generation unit 106 that generates, on the basis of the battery voltage 109, a high power-source voltage (hereinafter referred to as a high voltage 110) required when opening the valve body provided in the fuel injection valve 108, and the high voltage generation unit 106 boosts the battery voltage 109 to reach a desired target high voltage on the basis of an instruction from a driving IC 105. The high voltage generation unit may be implemented by, for example, a booster circuit including a coil, a condenser, and a switching element. As described above, the fuel injection valve 108 is provided with two lines of power sources including the high voltage 110 for securing a valve-opening power of the valve body and the battery voltage 109 that causes the valve body to remain open such that the valve body is not closed after being opened.
In addition, a fuel injection valve driving units 107a and 107b are provided upstream and downstream of the fuel injection valve 108 and supply a driving current to the fuel injection valve 108. The details will be described later, and thus the description is omitted herein.
The high voltage generation unit 106, the fuel injection valve driving units 107a and 107b are controlled by the driving IC 105 and apply the high voltage 110 or the battery voltage 109 to the fuel injection valve 108 to achieve a desired driving current. In addition, in the driving IC 105, choosing the driving period of the fuel injection valve 108 (current-passing time of the fuel injection valve 108) and a driving voltage, and a set value of the driving current are controlled on the basis of an instruction value calculated at a fuel injection valve pulse signal calculation block 102a and a fuel injection valve drive waveform instruction block 102b provided in an in-ECU (not illustrated) block 102.
Next, the driving units 107a and 107b for the fuel injection valve 108 illustrated in
Next, the fuel injection valve driving unit 107b downstream of the fuel injection valve 108 is provided with a switching element of TR_Low 205. A power source supplied from the fuel injection valve driving unit 107a that is upstream can be applied to the fuel injection valve 108 by turning the driving circuit TR_Low 205 on, and desired current control of the fuel injection valve 108 that will be described later is performed by detecting a current consumed by the fuel injection valve 108 with a shunt resistor 206. To be noted, the present description shows an example of a method of driving the fuel injection valve 108, and the battery voltage 109 may be used when opening the fuel injection valve 108 in place of the high voltage 110 in the case where, for example, a fuel pressure is relatively low or the high voltage generation unit 106 has a malfunction.
Next, current control of the fuel injection valve 108 in a conventional technique will be described with reference to
The driving current profile 302 in the example of
Next, valve body behavior of the fuel injection valve 108 will be described. After the pulse signal is turned on (T304), the high voltage is applied to the fuel injection valve 108 until reaching the valve-opening current 302a. The valve body starts opening at a time point (T305 in
Next, the injection quantity property in the case of using the driving current 302 illustrated in
To describe this in detail, in the section 402 between the time point T305 at which the valve body starts to open and the time point T306 at which the valve body reaches the full lift, the fuel injection quantity increases as the lift quantity of the valve body increases on the basis of the supplying time of the valve-opening peak current 302a. In this period, since an inclination 401a of the fuel injection quantity is determined in accordance with the opening speed of the valve body and the power-source voltage for the peak current is derived from the high voltage 110, a property in which the inclination of 401a increases steeply is given.
Thereafter, the valve body collides with a stopper, and thus boucing also occurs in the fuel injection quantity property due to the boucing motion 310 that has been already described (period from T306 to T307). This bouncing period 403 is generally not used because of, for example, large differences in properties between fuel injection valves or poor reproducibility between injection operations.
Thereafter, the valve body after the bouncing is settled (T307) has an increasing property with an inclination 401b proportional to the length of the pulse signal for keeping a full-lift position, and the minimum injection quantity of a conventional fuel injection valve 108 is treated as a fuel injection quantity at the time of full lift 405+a surplus quantity.
Next, an example in which half-lift control is performed on the basis of the conventional method of driving the fuel injection valve 108 described with
In
The valve-opening peak current increases after the time point T304 at which a pulse signal 501 is turned on (505, 506, or 507). Thereafter, by turning the pulse signal 501 off at a stage (T502, T503, or T504) before the time point T306 at which the valve body collides with the stopper, T502, T503, and T504 respectively draw loci 505, 506, and 507, and the driving current becomes 0 A. In the case where the valve-opening action is started at T306 after the sequence that has been already described and the pulse signal 501 is turned off at T502, valve behavior represented by 507 is shown. Similarly, 508 is shown for T503, and 509 is shown for T504. Since it is before the valve body collides with the stopper, it becomes possible to perform half-lift control on the valve body behavior. Examples of a problem that arises at this time include a problem that the inclination 401a at this time becomes a different property from the inclination 401b at a full-lift region since the inclination 401a is steep. Specifically, the fuel injection quantity property in this case is the period indicated by 402 in
For example, in the case where a required injection quantity less than the minimum injection quantity that has been already described is calculated in the ECU, a method of not using the period 403 by skipping to the half-lift control period 402 illustrated in
To solve these problems, the method of driving the fuel injection valve 108 according to the present invention is shown.
In addition, this peak current supply period 609 needs to be greater than a valve-openability-guaranteeing minimum current value 611, which enables surely performing valve-opening even under the maximum combustion pressure under which the fuel injection valve 108 is used, or than a period corresponding thereto. That is, this peak current supply period 609 is for generating at least a minimum magnetic force required for performing valve-opening action of the fuel injection valve 108 to guarantee valve-opening of the fuel injection valve.
After the requirement for completing the peak current supply period is satisfied, a lift quantity adjustment period 603 in which a current lower than the peak current is supplied to the fuel injection valve 108 for a prescribed period is provided. This lift quantity adjustment period 603 applies a low voltage represented by the battery voltage 109 to the fuel injection valve 108.
The present invention is characterized by controlling the lift quantity of the valve body in the half-lift state before reaching the full lift in accordance with the length of the lift quantity adjustment period 603. The details of this point will be described later with reference to
In addition, the present invention is characterized by being provided with a current cutoff period (from T605 to T606) for quickly reducing the peak current after the peak current supply period 609 and before transitioning to the lift quantity adjustment period 603. This is for the purpose of counterbalancing an excess valve-opening force (for example, in the case where the combustion pressure is low), which has occurred in the peak current supply period, in the current cutoff period (from T605 to T606). This once cancels the power of the valve body at the time of valve opening, and thus the controllability of the lift quantity in the half-lift state in the lift quantity adjustment period 603 thereafter is improved.
To quickly reduce the peak current in the current cutoff period (from T605 to T606), supply of the high voltage 110 and the battery voltage 109 to the fuel injection valve 108 may be cut off. Further, to quickly reduce the peak current, a negative voltage may be applied to the fuel injection valve 108. To apply the negative voltage, for example, a counter-electromotive force generated in the solenoid of the fuel injection valve 108 may be used. A current passing through the fuel injection valve 108 can be reduced by providing a path that is connected to a ground and the high voltage generation unit 106 (or an on-vehicle power source) via a commutator and serves as an escape for a countercurrent generated in the fuel injection valve 108 due to the counter-electromotive force when the driving units 107a and 107b are both turned off.
Here, completion requirement during the current cutoff period (from T605 to T606) transitions to the lift quantity adjustment period 603 when either one of a case of being reduced to reach a prescribed current value and a case of a prescribed period having passed is satisfied. When transitioning to the lift quantity adjustment period 603, control is performed via either of the battery voltage 109 and the high voltage 110 such that a target current value 612 is reached.
Next, the valve behavior will be described with reference to
In the valve-opening action, with the driving method illustrated in
Since the lift quantity adjustment period 603 is controlled by the battery voltage 109 and the speed of the valve speed is moderated, the full-lift position is reached in a soft-landed state 708 without the occurrence of a boucing period 707.
Next, the half-lift control of the present invention will be described with reference to
For convenience of description, the driving current 602 of
Valve behavior 803 at this time may be set so as to be the minimum lift quantity of the half-lift control. This is because the peak current supplied in the peak current supply period 609 is required to be set so as to surpass the valve-openability-guaranteeing minimum current value 611 required when opening the fuel injection valve 108, a degree in which difference derived from machine difference and pulsation width with respect to a target combustion pressure is considered even for fuel injection valves 108 with the same properties is assumed, and there is a possibility that the valve body does not open in the case where the current is lower than this. Of course, the peak current has a room for these factors to a certain degree. However, in a basic idea, the electric energy constituted by the peak current supply period 609 or by the peak current supply period 609 and the current cutoff period (from T605 to T606) is the minimum lift quantity having the reproducibility illustrated in
The description of
A pulse signal 901 of
This enables continuously increasing the lift quantity until reaching the full-lift position without the occurrence of boucing while providing a smooth valve-opening action. To see this as a fuel injection quantity property, a property illustrated in
As described with the valve behavior of
In the present invention, the state described with reference to
The present exemplary embodiment shows an example in which the present invention can be effectively used and includes, for example, making the valve-opening action of the valve behavior 706 illustrated in
Another exemplary embodiment according to the present invention will be described with reference to
In the first exemplary embodiment, the minimum lift quantity has been described with reference to
As has been already described, the stable valve behavior 803 guaranteed by the peak current supply period 609 or by the peak current supply period 609 and the current cutoff period (from T605 to T606), is not necessarily the same between fuel injection valves 108 with identical specifications. That is, changing the length of the peak current supply period 609 or the peak current value 610 due to machine difference of the fuel injection valve 108.
In other words, the valve behavior indicated by 803 in
I this case, with a control device including a means capable of directly detecting the valve lift quantity, it is enough as long as at least one of the length of the peak current supply period 609 and the peak current value 610 and one or more of the length of the current cutoff period (from T605 to T606) and the target current during current cutoff are adjusted. Here, adjustment using the actual valve-opening period 711 correlated with the lift quantity will be described.
In
In this case, the actual valve-opening period of 803 is 1104 and the actual valve-opening period of 1102 is 1105. By using a function to detect these two periods, difference between the two is eventually calculated and corrected to the peak current supply period 609. Although it is half lift in
In addition, the correction at this time is based on an idea of performing relative correction between fuel injection valves 108 provided in the same internal combustion engine, and, for example, the difference from the other fuel injection valves 108 is calculated by setting the longest actual valve-opening period 711 as the standard, and the correction is performed on the full-lift quantity and the peak current supply period 609 and the peak current 610 that serve as bases.
The peak current supply period 609 and the peak current 610 that serve as bases serve as bases indicate, for example, the peak current supply period 609 and the peak current 610 described with reference to
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-090820 | Apr 2014 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2015/059020 | 3/25/2015 | WO | 00 |
