Patent Application
20180010547
The present invention relates to a fuel injection valve, a control device for a fuel injection valve, and a control method.
A fuel injection valve mounted to an internal combustion engine is demanded to inject an appropriate quantity of fuel according to an operating condition, and an instruction for appropriate injection is issued by a fuel injection control device through a means for determining an operating condition. The fuel injection valve is activated to be opened and closed in such a way that a valve element is seated on and separated from a seat by being vertically moved due to magnetic force generated by current supply to a solenoid, and with this activation, the fuel injection valve injects fuel. The output and torque of the internal combustion engine are proportional to the fuel injection quantity, and the fuel injection quantity needs to be appropriately controlled according to an operating condition.
As a method for correcting an influence of pressure in a combustion chamber, a method has been proposed for correcting an injection quantity by a means for measuring and predicting a pressure in a combustion chamber. For example, PTL 1 (JP 2005-105947 A) indicates (see abstract) that “there is provided a technology for controlling a fuel injection quantity that changes with a change in an in-cylinder pressure with improved accuracy. As a solution, in controlling power supply time, a variation in a fuel injection quantity caused by a variation in a fuel injection rate at the in-cylinder pressure of an engine (detected or estimated value in the running state of the internal combustion engine) relative to a fuel injection rate at a reference in-cylinder pressure (under the condition of an injector characteristic measuring benchmark test) is calculated, and in addition, a variation in the fuel injection start timing is corrected. In the calculation of the variation in the fuel injection quantity, a fuel injection rate changing behavior model in which changing behavior of the fuel injection rate is modeled as a trapezoid is used to calculate the areas of Δq1 and Δq2. The variation in the fuel injection start timing Δτd is calculated based on a rail pressure and the variation in the in-cylinder pressure”.
In addition, PTL 2 (JP H09-256886 A) indicates (see abstract) that “In a fuel injection control device for a direct injection type engine, a fuel injection quantity is precisely controlled without using an in-cylinder pressure sensor. As a solution, the fuel injection control device is provided with: an in-cylinder pressure computing means 104, which computes a pressure Pc inside the cylinder according to the detected operating condition; a differential pressure computing means 105 that computes a differential pressure Pf between the computed in-cylinder pressure Pc and a pressure of fuel fed to an injector 101; a fuel injection rate computing means 106 that computes a fuel injection rate K on the basis of the computed differential pressure Pf; and a fuel injection quantity correction means 107 that corrects a valve opening time Ti of the injector 101 on the basis of the computed fuel injection rate K”.
PTL 1: JP 2005-105947 A
PTL 2: JP H09-256886 A
Force exerted on a valve element of a fuel injection valve includes force of a spring which is a component of the fuel injection valve and a fuel pressure in a direction of closing the valve element, and magnetic force generated by supply of current to a solenoid in a direction of opening the valve element. Further, a valve element of a fuel injection valve that directly injects fuel into a combustion chamber receives a pressure in the combustion chamber. Particularly, the pressure received by the valve element of the fuel injection valve is different between at an injection timing being in an engine intake stroke and an injection timing being in an engine compression stroke. In the injection in the compression stroke, the valve element, which is open inward and faces the combustion chamber, of the fuel injection valve receives force in the direction of opening the valve element. The present inventors have found that, a time at which the valve element opens becomes earlier or a time at which the valve element closes is delayed by force applied in the direction of opening the valve element, and therefore, a fuel injection quantity may be more than the fuel injection quantity expected in advance based on drive current supplied to the fuel injection valve.
Neither PTL 1 (JP 2005-105947 A) nor PTL 2 (JP H09-256886) described above indicates that a fuel injection rate and fuel injection timing are corrected on the basis of an in-cylinder pressure which is a reference for an injection start timing, and an injection quantity is changed by an application of force in a direction of opening the valve element due to the in-cylinder pressure during a compression stroke rather than during an intake stroke in an engine cycle. A method for correcting the injection rate and the injection timing by means of an injection signal is disclosed. However, there arises a problem such that, only by controlling a time for supplying current to the fuel injection valve, the magnetic force to the valve element varies, so that a time at which the valve element opens or a time at which the valve element closes is changed to vary an injection quantity.
Particularly, at half lift, opening of the fuel injection valve is not accompanied by collision of the valve element, and when a valve element position is specified before the valve element is fully open, the relation of force exerted on the valve element determines an open position of the valve element and an injection quantity, so that the injection quantity becomes larger due to the influence of force received from the combustion chamber.
In view of this, an object of the present invention is to suppress deviation of a quantity of fuel injected in intake, compression, and expansion strokes in an engine cycle from a target injection quantity according to an injection timing, considering force from a combustion chamber to a valve element of a fuel injection valve that directly injects fuel to the combustion chamber.
In order to achieve the above object, the present invention provides a control device for a fuel injection valve that performs a plurality of injections in one cycle, the control device including a control unit that controls a time for supplying drive current to the fuel injection valve, wherein the control unit controls so that, when fuel is injected in a compression stroke, a time for supplying drive current for injection at a second injection timing later than a first injection timing is shorter than a time for supplying drive current for injection at the first injection timing.
According to the control device for a fuel injection valve in the present invention, deviation between an injection quantity of fuel injected from the fuel injection valve in a compression stroke and a target value can be suppressed. The foregoing and other objects, features and advantages of the invention will be apparent from the following description of preferred embodiments.
An embodiment of a fuel injection valve according to the present invention will be described below in detail with reference to the drawings.
An embodiment of the present invention will be described with reference to the drawings.
Further, an amount of intake air is measured by an airflow sensor 3 mounted on an intake duct. The amount of air sucked by the engine 1 is controlled by a throttle valve 4. An intake collector 5 distributes air to other cylinders not illustrated, and after passing through the intake collector 5, air is distributed to intake pipes of the respective cylinders, and sucked into a combustion chamber 22 through an intake valve 25. An unillustrated airflow control valve for imparting directionality to airflow may be provided on the intake pipe 6. Fuel is transported through a fuel path in such a way that the fuel transported under pressure into a fuel pipe from a fuel tank 7 by projection of an unillustrated low-pressure fuel pump is transported to a common rail 8. The fuel is also pressurized and accumulated by a high-pressure fuel pump 10 provided to an intake cam shaft 9.
An engine control unit (hereinafter referred to as an ECU) 11 determines an operating condition of the engine 1 in the ECU 11 based on signals from various sensors mounted to the engine 1, and outputs instruction values appropriate for the determined operating condition to various actuators. Examples of various sensors include: the airflow sensor 3; a fuel pressure sensor 12 provided to the common rail 8 for detecting a pressure of fuel; a phase sensor 13 for detecting a phase of the intake cam 9; a phase sensor 15 for detecting a phase of an exhaust cam 14; a crank angle sensor 17 for detecting a rotational speed of a crankshaft 16; a water temperature sensor 18 for detecting a temperature of engine cooling water; a knock sensor (not illustrated) for detecting knocking; and an exhaust gas sensor (exhaust A/F sensor 20, exhaust O2 sensor 21) for detecting a concentration of exhaust gas in an exhaust pipe 19. Further, examples of various actuators include a fuel injection valve 23, the high-pressure fuel pump 10, the throttle valve 4, an airflow control valve (not illustrated), a phase control valve (not illustrated) for controlling phases of intake and exhaust cams, and an ignition coil 28.
In the light of the operating configuration of the engine 1, a control unit (microcontroller) of the ECU 11 receives an air amount measured by the airflow sensor 3 and signals from the exhaust A/F sensor 20 and the exhaust O2 sensor 21 to calculate a fuel injection quantity of the fuel injection valve 23. The control unit (microcontroller) in the ECU 11 also detects, by means of the fuel pressure sensor 12, the pressure of the fuel pressurized by the high-pressure pump 10, and determines an injection period (injection pulse width) of the fuel injection valve 23 on the basis of the calculated fuel injection quantity of the fuel injection valve 23 and the detected fuel pressure. An injection pulse signal is transmitted to an unillustrated drive circuit for the fuel injection valve 23 from the ECU 11, and drive current is outputted from the drive circuit for the fuel injection valve 23 to the fuel injection valve 23, whereby the fuel injection valve 23 injects the fuel.
The drive signal transmitted from the ECU 11 mainly includes an injection timing, the number of times of injection, and an injection period. In the present embodiment, the detail of the injection pulse signal will be described later. Air and fuel supplied to the combustion chamber 22 are vaporized and mixed in the combustion chamber 22 with the vertical movement of a piston 24, forming an air fuel mixture. Then, the temperature and pressure rise due to the compression operation of the piston 24. The ECU 11 calculates an ignition timing from information such as the engine speed and the fuel injection quantity, and outputs an ignition signal to the ignition coil 27. The ignition signal mainly includes a start timing of current supply and an end timing of current supply to the ignition coil 27.
Accordingly, ignition is performed by an ignition plug 28 at a timing slightly before the compression top dead center of the piston 24, so that the air fuel mixture in the combustion chamber 22 is ignited and combustion occurs. The ignition timing may be after the compression top dead center, because the ignition timing differs according to an operating condition. Force for pushing back the piston 24 downward is applied due to the increased pressure by the combustion, and this force is transmitted to the crankshaft 16 as engine torque during the expansion stroke and becomes engine power. After the combustion, gas remaining in the combustion chamber 22 is discharged to the exhaust pipe 19 through the exhaust valve 26. This exhaust gas often includes components harmful to humans. Therefore, this exhaust gas is detoxified by the action of a catalyst 29 disposed on the exhaust pipe 19, and then, discharged in the atmosphere.
Next, the detailed configuration of the fuel injection valve 23 according to the present embodiment will be described with reference to
The ECU 11 in
Each signal will be described in detail. The control unit (microcontroller) in the ECU 11 outputs the injection pulse signal 301 to the unillustrated drive circuit, and the drive circuit receiving this injection pulse signal 301 outputs drive current with the drive current waveform 302 to the solenoid 214. As indicated by the drive current waveform 302, the drive current increases until reaching the maximum drive current value Ip after being supplied. Thus, the magnetic force 303 generates magnetic force sufficient for opening the valve element 208 in
Then, the control unit (microcontroller) in the ECU 11 controls so that the drive current keeps a first drive current value Ih1 which is smaller than the maximum drive current value Ip and required for keeping the valve element open, after the drive current reaches the maximum drive current value Ip. Thereafter, the control unit (microcontroller) in the ECU 11 controls so that the drive current keeps a second drive current value Ih2 which is smaller than the first drive current value Ih1 and required for keeping the valve element open. Thus, the magnetic force 303 continuously keeps enough magnetic force to open the valve element. In this case, the solenoid 214 in
Next,
The quantity of fuel injected here is determined by an opening amount and an opening time of the valve element 208 of the fuel injection valve, and the differential pressure between the fuel pressure exerted on the valve element of the fuel injection valve and the pressure in the combustion chamber into which the fuel is to be injected by the fuel injection valve.
On the other hand, besides the fuel pressure, biasing force of the spring 210 and the magnetic force are exerted on the valve element 208 for closing the valve element 208. Therefore, closing force is exerted on the valve element, regardless of the driving condition of the vehicle. The current supply to the solenoid 214 in the fuel injection valve is performed so that magnetic force is generated, for opening the valve element, so as to overcome the fuel pressure controlling a fuel quantity to obtain required output and torque and force of the spring constituting the fuel injection valve for closing the valve element.
Therefore, to open the valve element, it is necessary to generate, by means of the solenoid, magnetic force exceeding a total value of the fuel pressure according to the respective operating conditions and the force for closing the valve element due to the spring force and the magnetic force dependent on the structure of the fuel injection valve. When the valve element is closed, the spring force and the fuel pressure are exerted in the direction of closing the valve element, and remaining surplus magnetic force due to the current supply to the solenoid is exerted in the direction of opening the valve element. In addition, if fuel is directly injected into the combustion chamber, the pressure in the combustion chamber is greatly exerted in the direction of opening the valve element. Therefore, to reliably close the valve element, it is general that the spring, which is a component of the fuel injection valve, is designed to have larger force for reliably closing the valve element.
However, in the fuel injection valve which directly injects fuel into the combustion chamber, the pressure in the combustion chamber is exerted to the valve element in the direction of opening the valve element, as well as the fuel pressure, the magnetic force due to the solenoid, and the force of the spring provided to the fuel injection valve. It is to be noted that the generation of force in the direction of closing the valve element due to negative pressure during the intake stroke is not described here for simplifying the description, since the generation of this force occurs less. The present inventors have found that, according to this, the time in which the valve element is open becomes short, and the time in which the valve element closes becomes long. Particularly, the effect caused by the pressure in the combustion chamber which is higher in the compression stroke than in the intake stroke is great in one engine cycle including intake, compression, expansion, and exhaust strokes. Note that 4-stroke engine is described here for simplifying the description. In addition, the detailed description for the injection in the expansion stroke will not be described here.
In the control for the fuel injection valve which performs a plurality of injections in one engine cycle, a timing at which the valve element opens may be earlier due to the effect of the injection in the compression stroke, and therefore, in this case, the actual injection quantity may be deviated from a target injection quantity which has been set. Next, a method for controlling the fuel injection valve when the pressure received by the fuel injection valve from the combustion chamber is not considered will be described with reference to
The in-cylinder pressure 507 indicates a pressure in the cylinder, and the ignition signal 508 indicates an engine ignition timing when the ignition timing is retarded to increase the temperature of the catalyst. The injection pulse signals 509 and 510 indicate injection pulse signals when the pressure received by the fuel injection valve from the combustion chamber is not considered, and the injection pulse signal 510 is transmitted at a timing later than the timing at which the injection pulse signal 504 is transmitted. In addition, the drive currents 511 and 512 indicate drive currents transmitted to the solenoid 214 from the drive circuit that receives the injection pulse signals 509 and 510.
As described above, it is necessary to retard the ignition timing to increase the temperature of the catalyst, and thus to form an air fuel mixture and perform ignition at the retarded ignition timing. For this end, the injection timing needs to be retarded from 504 to 510. In
However, as described above, there arises a problem such that the injection quantity increases relative to the target injection quantity because force in the direction of opening the valve element is exerted on the valve element of the fuel injection valve by the in-cylinder pressure due to the retardation of the injection timing. The control for the fuel injection valve according to the present embodiment to address this problem will be described with reference to
The control method in the present embodiment illustrated in
Then, it is determined whether or not a target combustion state is achieved based on the signals from the exhaust A/F sensor 20 and the exhaust O2 sensor 21 and the crank angle sensor 17 in
More specifically described, when fuel is injected in the compression stroke, the control unit in the ECU 11 for the fuel injection valve in the present embodiment controls so that a time for supplying the drive current 612 for the injection at a second injection timing of the injection pulse signal 610 later than a first injection timing of the injection pulse signal 604 becomes shorter than a time for supplying the drive current 606 for the injection at the first injection timing of the injection pulse signal 604.
In other words, when fuel is injected in the compression stroke, the control unit in the ECU 11 controls so that the width of the injection pulse signal 610 for the drive current 612 for the injection at the second injection timing later than the first injection timing becomes smaller than the width of the injection pulse signal 604 for the drive current 606 for the injection at the first injection timing.
This control is especially effective when being executed together with retarding the ignition timing for raising the temperature of the catalyst, in injecting fuel in the compression stroke in fast idling at engine startup. That is, according to this control, the injection quantity can be less deviated from the target value, whereby an effective operating region can be achieved. In fast idling, an operation in which A/F is lean with less required injection quantity is performed such as stratified combustion, and injection is performed frequently in the compression stroke. Therefore, unless the control according to the present embodiment is performed, deviation of an injection quantity becomes a problem.
When the engine to which the fuel from the fuel injection valve is discharged is operated in a full-open operating region and the fuel is injected in the compression stroke, an in-cylinder pressure is particularly likely to increase. Therefore, if fuel is injected based on the injection pulse signal 510 illustrated in
In view of this, the control unit in the ECU 11 may apply the control in
Next,
In addition, respective reference signs in
At half lift, not only the opening of the valve element and the speed of opening the valve element but also the height of the valve element are increased unintentionally. In view of this, in the present embodiment, the maximum drive current becomes smaller as the injection start timing is retarded as illustrated in
More specifically described, the control unit in the ECU 11 controls so that, when the valve element 208 of the fuel injection valve is moved to a position lower than the maximum height position in the compression stroke, the maximum value of the drive current 712 for the injection at a second injection timing of the injection pulse signal 710 later than a first injection timing of the injection pulse signal 704 becomes smaller than the maximum value of the drive current 706 for the injection at the first injection timing.
It is to be noted that, in this case, the control unit in the ECU 11 may control so that the time for supplying the drive current 712 for injection at the second injection timing of the injection pulse signal 710 later than the first injection timing of the injection pulse signal 704 becomes shorter than the time for supplying the drive current 706 for injection at the first injection timing, as in
In addition, the control unit in the ECU 11 may control the drive current so that the fuel injection valve is driven by the same maximum drive current in a plurality of injections, when the valve element of the fuel injection valve is moved to the maximum height position, that is, the valve element 208 is driven at full lift, in the compression stroke. At full lift, the same maximum drive current is supplied to excessively provide magnetic attraction force generated by the solenoid, by which the amount of change in the time in which the valve element is open and the speed for opening the valve element is reduced.
Next, the flow of the control according to the present embodiment will be described with reference to a flowchart in
According to the control device for a fuel injection valve in the present embodiment described above, deviation between an injection quantity of fuel injected by the fuel injection valve in the compression stroke and a target value can be suppressed, whereby an internal combustion engine having enhanced fuel economy performance and exhaust performance can be implemented.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-043103 | Mar 2015 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2016/055740 | 2/26/2016 | WO | 00 |
