JP5853093B2 - Electromagnetic force equipment - Google Patents

Description

  The present invention relates to a device that operates by converting electric power into dynamic force using electromagnetic force.

  Patent Document 1 discloses a fuel injection timing detection technique in which a distortion detector that detects distortion in the moving direction of a needle in a nozzle body is provided on the outer periphery of the nozzle body.

  Patent Document 2 discloses a technique for detecting an electromagnetic flux generated around a solenoid coil with a leakage flux detection coil set in the vicinity of the solenoid coil and determining an operating state of the electromagnetic control valve.

JP-A-11-223170 JP 2009-204128 A

  Technologies and products that operate by converting electric power into dynamic force using electromagnetic force are widely known and used in actuators and power equipment. As a method of using electromagnetic force, there is a method in which a magnetic material such as an iron core is arranged at the center of a coil and a magnetic attraction force generated between a magnetic material member provided as a movable member different from the iron core and the iron core is taken out. It is common.

  Magnetic materials (not necessarily iron) used for the iron cores of such devices cause variations in device operation due to variations in material composition, currents applied to the coils, and component dimensional variations. There is a problem.

  The main cause of such operation variation is variation in magnetic attractive force acting between the iron core in the device and the movable member. In addition to the current supplied to the coil, the magnetic attractive force is influenced by the composition of the material, the state of the structure by heat treatment, and the dimensions of the parts. Further, the magnetic attractive force is not necessarily generated linearly with respect to the current applied to the coil. That is, the magnetic attraction force is not necessarily generated linearly with respect to the current applied to the coil due to the nonlinearity of the material, the shape of the material, and the influence of a transient phenomenon caused by the generation and attenuation of the eddy current.

  For this reason, even if the current waveform applied to the coil is the same, the same magnetic attractive force is not always obtained, and the operation of the device may vary.

  The fuel injection valves disclosed in Patent Document 1 and Patent Document 2 are solenoid actuators that operate by electromagnetic force. In the fuel injection valve, since the injection amount is determined by the opening time of the valve body for performing the opening / closing operation and the lift amount of the valve body, the operation variation becomes the injection amount variation. For this reason, Patent Document 1 and Patent Document 2 disclose a method of monitoring the operation of the valve body.

  Patent Document 1 captures changes in the stress of the body accompanying the operation of the valve, and can detect the timing of fuel injection. However, the strain detector is provided far away from the parts constituting the magnetic path, and detects the magnetic attraction force and magnetic flux acting inside the solenoid actuator that determines the operation of the valve element. There is no consideration. For this reason, although the force which a valve body receives as a result of operation of a solenoid can be detected indirectly, it was not necessarily enough to use as a signal for controlling operation of a solenoid itself.

  Patent Document 2 discloses a method of detecting magnetic flux generated in a solenoid from leakage magnetic flux. However, in a solenoid actuator that generates a large magnetic attractive force, it is common to reduce the magnetic resistance by covering the outside of the actuator with a magnetic material. Does not occur. Alternatively, if a gap is provided in the magnetic body that covers the outside so as to generate a leakage magnetic flux, there is a problem that the force generated as an actuator is reduced.

  An object of the present invention is to provide a method for detecting magnetic flux in a device that generates electromagnetic force. Further, as a device for generating electromagnetic force, a fuel injection valve, which is one of solenoid actuators, is to perform an accurate valve operation so that a minute injection amount can be precisely controlled.

  In order to achieve the above object, in the present invention, the members constituting the magnetic circuit are provided with strain detecting means for detecting strain in the magnetic flux passing direction.

  A force is applied to the magnetic member constituting the magnetic circuit by a magnetic flux penetrating itself, and stress is generated inside by this force. By detecting the strain caused by this stress, the magnetic flux generated in the device can be measured, and the magnetic attractive force generated according to the magnetic flux can be monitored.

  Further, by using the detected magnetic attraction force and magnetic flux to feed back to the current waveform for driving the device, it is possible to reduce the variation in the operation of the device and to perform more precise and minute operation.

  ADVANTAGE OF THE INVENTION According to this invention, the magnetic flux which has arisen in the magnetic circuit of the apparatus which operate | moves with an electromagnetic force can be monitored. With the measured magnetic flux, the electromagnetic force generated in the device can be monitored.

  By monitoring the magnetic flux or electromagnetic force, the current waveform for driving the device can be controlled using this value or the detected voltage.

  In a fuel injection valve that is a solenoid actuator that operates by electromagnetic force, more accurate operation can be performed, and a minute injection amount can be controlled.

1 is a system diagram showing an embodiment of a fuel injection valve and a drive device thereof according to a first example of the present invention. It is sectional drawing of the fuel injection valve which concerns on 1st Example of this invention. It is a schematic diagram which shows the principle of operation of this invention. It is a schematic diagram which shows the operation principle of this invention and the mounting position of a distortion | strain detection means. It is sectional drawing which shows the mounting position of the distortion | strain detection means in the fuel injection valve which concerns on 1st Example of this invention. It is a time chart which shows the method of controlling the fuel injection valve which concerns on 1st Example of this invention.

  Examples of the present invention will be described below.

  FIG. 1 is a diagram showing a system configuration of the first embodiment of the present invention. The first embodiment is an embodiment in which the present invention is applied to a fuel injection valve used in an internal combustion engine as a device using electromagnetic force. The fuel injection valve is a device that operates an internal valve using electromagnetic force generated by a solenoid, and its structure is as shown in FIG. The fuel injection valve 101 is provided with a strain detector 104.

  The drive circuit 102 performs energization control to the fuel injection valve 101. The drive circuit 102 is connected to the fuel injection valve 101 and is also connected to the ECU 106 so that signals can be exchanged. The drive circuit 102 may be configured in the same casing of the ECU 106 or in the same circuit board.

  An injection command pulse from the ECU 106 is transmitted to the drive IC 103 via the wiring 109. The drive IC 103 energizes the fuel injection valve 101 via the wiring 108 based on the injection command pulse. The current waveform to be energized is controlled by the drive IC 103.

  In the present invention, information of the strain detector 104 attached to the fuel injection valve 101 is used to determine the drive current waveform supplied from the drive IC 103 to the fuel injection valve 101. A signal obtained from the strain detector 104 is converted into an analog signal indicating a strain value in the drive circuit and transmitted to the drive IC 103.

  For example, as shown in FIG. 1, an analog signal representing the amount of distortion is input to a comparator 105 provided in the drive circuit 102, and a predetermined voltage value input from an ECU (engine control unit) 106 is input to the comparator 105. When the input is made and the result is transmitted to the drive IC 103, the drive IC 103 generates a drive current waveform of the fuel injection valve 101 sent to the wiring 108 based on the strain value detected by the strain detector 104. Can be determined.

  The signal obtained by the strain detector 104 can be used as a signal for detecting a magnetic flux generated in the magnetic circuit of the fuel injection valve 101, which is a solenoid. For this purpose, a drive waveform for improving the drive state of the fuel injection valve 101 is used. Then, it can be sent from the drive circuit 102.

  Hereinafter, the basic operation of the fuel injection valve 101, the installation method of the strain detector 104 for detecting the magnetic flux, the principle that the magnetic flux can be detected, and the drive waveform determination method using the same will be described.

  First, the basic operation of the fuel injection valve 101 will be described with reference to FIG. The fuel injection valve 101 shown in FIG. 2 includes a coil 204 that is supplied with a current from a terminal 211. When the coil 204 is energized, the magnetic core 202, the mover 203, the cylindrical member 214, and the yoke 201 Magnetic flux is generated in the magnetic circuit. When the magnetic flux is generated, a magnetic attractive force acts between the magnetic core 202 and the movable element 203, and the movable element 203 urged by the urging force of the urging spring 206 by this magnetic attractive force is attracted toward the magnetic core 202. Is done. At this time, since the mover 203 and the valve body 205 move integrally, the valve body 205 is also displaced in the direction of the magnetic core 202, and the valve body 205 creates a gap between the valve seat and the fuel supply port 213. The fuel supplied under pressure is injected from an injection hole 207 provided in the nozzle.

  The injection amount of the fuel injection valve 101 is controlled by the time during which the coil 204 is energized. That is, if the energization time is long, a lot of fuel is injected. However, in a general fuel injection valve, since the response of magnetic flux generated in the magnetic circuit is delayed with respect to the energized current, it is difficult to inject while controlling a small injection amount even if the energization time is shortened. There is a case. Further, the response delay of the magnetic flux is affected by the size of parts constituting the magnetic circuit and the variation of material characteristics.

  The magnetic flux determines the magnetic attractive force, the magnetic attractive force determines the operation of the valve body 205, and the injection amount by the fuel injection valve 101 is influenced by the operation of the valve body 205, and thus is injected from the fuel injection valve 101. When the fuel amount is very small, it is difficult to control the injection amount and to suppress the variation due to the variation in magnetic flux.

  In an internal combustion engine, it can be controlled to a minute injection amount, so that it can be burned even under a lower load condition. For example, in a scene where an engine brake is used, there is a range in which fuel injection can be stopped. An internal combustion engine that extends to the low load side and has a lower fuel consumption can be obtained. Alternatively, by performing fuel injection a plurality of times during one stroke, it is possible to promote the mixing of the fuel and suppress the generation of unburned fuel components, nitrogen oxides, and soot contained in the exhaust.

  In the embodiment according to the present invention shown in FIG. 2, the strain detector 104 is attached after providing a flat surface on the side surface of the yoke 201 constituting the solenoid, and is connected to the strain signal extraction connector 210 via the wiring 209. Has been. The direction of the strain detected by the strain detector 104 is attached so as to be the magnetic flux passing direction at the attachment position of the strain detector 104 of the yoke 201. By mounting in this way, the magnetic flux can be detected from the signal obtained by the strain detector 104.

  Here, the yoke 201 is a member configured to cover the periphery of the coil 204 on a cross section (cross section as shown in FIG. 2) in which the direction of the wire of the coil 204 is a normal direction.

  Next, the principle that magnetic flux can be detected by strain will be described with reference to FIG. FIG. 3A shows a general solenoid in which an iron core 302 and an iron core 303 are inserted in the center of a coil 301, and a gap 304 is provided between the iron cores 302 and 303.

When the solenoid coil 301 having such a configuration is energized, a magnetic flux is generated in the iron cores 302 and 303, and a force F as shown in the following formula acts on the iron cores 302 and 303 in the gap 304. However, B is the magnetic flux density generated by energization, S is the cross-sectional area of the gap portion of the iron cores 302 and 303, and μ ₀ is the vacuum permeability.
F = B ² S / 2μ ₀ (Expression 1)

  That is, the force F is not directly related to the size of the gap 304. The force F does not act due to the presence of the air gap 304 but acts due to the magnetic flux density B. Therefore, as shown in FIG. 3 (b), the above formula shows that the force F is generated even when there is no gap 304, and the magnetic flux density at that portion of the iron cores 302 and 303 is taken regardless of the cross section. A force corresponding to B is generated.

  For this reason, the iron cores 302 and 303 generate stress inside due to the force F, and thus the iron cores 302 and 303 are distorted. Unlike the so-called magnetostriction phenomenon that occurs due to the anisotropy of the orbital radius of electrons that circulate around the nuclei in the crystal lattice, this strain is generated by a mechanical mechanism, so that the iron cores 302 and 303 are not special materials. Can be detected.

  This principle can also be used in a solenoid actuator having a yoke 402 made of a magnetic material as shown in FIG. The yoke 402 is a member that covers the periphery of the coil 401 so that the magnetic flux that has passed through the part that generates the magnetic attractive force is directed again to the part that generates the magnetic attractive force.

  In the solenoid having the yoke 402, the magnetic flux passes through the magnetic body as indicated by an arrow 405, and the yoke 402, the iron core 403, and the iron core 404 are distorted according to the magnetic flux density. Therefore, in the solenoid having the yoke, the magnetic flux can be detected by attaching the strain detector 104 to the yoke.

  In the example of FIG. 4, it is effective to provide a flat portion on the side surface of the yoke 402 and attach the strain detector 104 to the side surface 406. Further, since the magnetic flux passes through the upper surface 407 and the lower surface 408 of the yoke, the magnetic flux can be detected by attaching the strain detector 104 to these portions. Here, in any case, the strain detected by the strain detector 104 is efficiently generated by the magnetic flux by attaching the strain detector 104 so that the magnetic flux penetrates the member to which the strain detector 104 is attached. Strain can be detected. In general, in a solenoid having a yoke 402, the yoke 402 often covers the coil 401. Therefore, the strain detector 104 is preferably installed outside the yoke 402. By doing so, not only the installation is facilitated, but also the wiring is easily pulled out, and it is easy to fix from the outside by a resin mold or the like.

  As the strain detector 104 used here, a general resistance-type strain gauge can be used, but it is particularly preferable to use a semiconductor sensor as disclosed in JP-A-2006-220574. Since the semiconductor sensor is not easily affected by the magnetic field, it is difficult to be affected by the magnetic flux leaking to the mounting portion of the strain detector 104, and the magnetic flux component that generates the magnetic attractive force can be accurately measured.

  FIG. 5 is a cross-sectional view showing mounting positions 501, 502, 503, and 504 of the strain detector 104 in the fuel injection valve. By attaching the strain detector 104 to the yoke 201 of the fuel injection valve 101, the magnetic flux can be detected. The fuel injection valve 101 may be provided with a cylindrical member 214 in order to prevent the fuel from leaking to the outside. Since the cylindrical member 214 needs to pass magnetic flux between it and the yoke 201, it is desirable that the cylindrical member 214 be made of a soft magnetic material. Therefore, since the cylindrical member 214 is also a part through which the magnetic flux passes, the magnetic flux can be detected even if the strain detector 104 is attached to the cylindrical member 214. In particular, the strain detector 104 may be provided in parallel with the gap between the magnetic core 202 corresponding to the iron core and the mover 203 as shown in the position 504 shown in the figure. As described above, by providing the strain detector 104 in parallel with the gap of the iron core, it is possible to detect the distortion generated in the process in which the magnetic flux leaked from the gap precedes the tubular member 214 and is highly sensitive. .

  Thus, by attaching the strain detector 104 to the yoke 201 or the cylindrical member 214, the magnetic flux can be detected. Moreover, since any attachment position can be attached to the site | part isolated from the fuel and a magnetic flux can be detected, the wiring from a distortion | strain detection means can be isolated from a fuel. That is, the strain detecting means can be attached without using means such as making a hole in the fuel injection valve.

  FIG. 6 is a time chart showing a method of energizing the fuel injection valve 101 according to the present invention. FIG. 6A is a diagram showing a general energization method of a direct injection fuel injection valve. The injection command pulse and drive current waveform from the ECU, and the magnetism generated between the magnetic core 202 and the mover 203 are shown. The relationship between the suction force and the operation of the valve body 205 is shown.

  The start of energization is started with the start of the injection pulse as shown in FIG. The initial drive current 601 from the start of energization to the timing 606 is supplied from a voltage source boosted higher than the battery voltage of the engine, and thus the drive current increases rapidly. In this process, the magnetic attractive force exceeds a certain threshold value 604, and at this timing 605, the valve body starts a valve opening operation.

  In a general method, the boosted voltage is applied until timing 606. This timing 606 is determined by the drive IC 103 determining that the value of the drive current has reached a predetermined threshold value 607 or after a predetermined time from the start of the injection pulse. The timing is determined.

  After the timing 606 when the current reaches a peak, the current value is controlled so that the current value falls within a predetermined range 610 to 609 by switching the battery voltage. As a result, the magnetic attractive force gradually decreases as shown by the magnetic attractive force 608 and approaches a constant value.

  When the injection pulse ends, the magnetic attractive force decreases, and when the magnetic attractive force falls below the threshold value 604, valve closing is started. The time from the end of the injection pulse to the completion of valve closing is a valve closing delay 623.

  Thus, in a general energization method, the drive current profile is controlled to be in a predetermined state. On the other hand, it is the magnetic attractive force profile that determines the operation of the valve element. The magnetic attraction force is affected by the dimensions and material properties of the parts constituting the solenoid, and the relationship with the drive current profile is not a constant multiple because of the generation of eddy current. For this reason, in general methods, if there is a variation in the dimensions or material properties of the parts, or a change in electrical resistance or magnetic characteristics due to a change in environmental conditions, the magnetic attraction force is predetermined even if the same drive current waveform is given. Therefore, the operation of the valve body 205 is likely to vary.

  Further, when the injection command pulse width is reduced, the drive current waveform is cut off in the process of decreasing the magnetic attraction force like the magnetic attraction force 608, and at the timing at which it is cut off due to the change in the pulse width. The magnetic attractive force changes, and the valve closing delay time 623 changes. For this reason, the substantial valve opening time cannot change linearly due to the change in the pulse width, and the injection amount control with a short pulse width tends to be difficult.

  In the state where the holding operation of the valve body 205 is performed, the current control ranges 609 to 610 are determined in consideration of various variations, so that a margin is provided for the minimum force 604 actually required. become. For this reason, the valve closing delay time 623 tends to be long, and the injection amount increases for the same injection pulse width.

  As described above, when the drive current waveform is controlled by a general method, it is difficult to accurately control the minute injection amount.

  The driving current control method according to this embodiment is a method as shown in FIG. In this embodiment, the drive current waveform is controlled not by the current value but by the magnetic attractive force.

The magnetic attractive force can be known from the value of the strain detector 104 attached to the fuel injection valve 101. The magnetic attraction force Fmag is expressed by the following equation, where E is the Young's modulus of the mounting member of the strain detector 104, A is the cross-sectional area of the mounting portion of the strain detector 104, S is the suction area, and ε is the detected strain value. Can be calculated as follows. Since K is a constant, the profile of the magnetic attractive force can be known from the value of strain ε.
Fmag = KA ² Eε / S (Equation 2)

  In the drive current control method shown in FIG. 6B, the timing at which the energization with the boosted voltage is stopped is determined as a predetermined time 621 after the magnetic attraction force exceeds a predetermined value 617. By detecting the timing when the magnetic attraction force exceeds a predetermined value and determining the timing to stop applying the boost voltage, the magnetic attraction force may vary due to variations in parts constituting the solenoid, variations in material properties, or changes in environmental conditions. Even if it has changed, the application time of the boosted voltage is automatically adjusted accordingly. As a result, it is possible to avoid a state in which the energization time is insufficient and the valve operation becomes slow, and the fuel injection valve 101 can be driven by applying the minimum boosted voltage.

  After the energization with the boosted voltage is stopped, the drive current waveform drops like a current 622. Here, the magnetic attraction force can be quickly converged to a predetermined value by stopping the energization until the magnetic attraction force reaches a predetermined current value 619 or applying a reverse voltage. The curve 618 in which the magnetic attractive force decreases after the energization is cut off is easily affected by variations in magnetic and electrical characteristics of the materials used, variations in dimensions, or environmental conditions such as temperature. When the stop period is determined based on the time or current value, the magnetic attractive force does not decrease sufficiently, or the magnetic attractive force becomes smaller than a desired value, and the variation of the movement of the valve body 205 is caused. It may become a factor to enlarge. According to the method of starting energization by detecting that the magnetic attractive force has reached the predetermined value 619 as in this embodiment, such a problem can be avoided.

  In the driving current control method shown in FIG. 6B, the current is controlled so that the magnetic attractive force falls within the range 619 to 620. For example, by performing switching control such that energization is stopped when the magnetic attraction force exceeds a predetermined value 620 and energization is performed when the magnetic attraction force falls below a predetermined value 619, the magnetic attraction force is kept within a predetermined value range. Can be controlled to be almost constant. As described above, since the magnetic attraction force becomes a substantially constant value, even when the injection pulse width changes, the change in the valve closing delay time 624 can be reduced. Therefore, the injection amount becomes linear with respect to the change in the injection pulse width. To change. In addition, since the magnetic attractive force is kept constant, variations due to individual variations in the valve closing delay time 624 and changes due to environmental changes can be reduced.

  By controlling the drive current so that the magnetic attractive force becomes a constant value in this way, it is possible to avoid an excessive magnetic attractive force like the magnetic attractive force 608 in FIG. 6A. The valve closing delay time 624 shown in FIG. 6B can be set shorter than the valve closing delay time 623 shown in FIG. As a result, it is possible to control a smaller injection amount even with the same pulse width.

  As described above, according to this embodiment, the magnetic attraction force can be detected and fed back to the control. By feeding back the magnetic attraction force, variation in the operation of the valve body is suppressed, and the operation delay is caused. This makes it possible to control a finer injection amount.

101 Fuel Injection Valve 102 Drive Circuit 103 Drive IC
104 Strain detector 105 Comparator 106 ECU
107 Strain signals 108, 601, 622 Drive current wiring 109 Drive pulse wiring 110 Predetermined voltage value 111 Control signal 201, 402 Yoke 202 Magnetic core 203 Movable element 204, 301, 401 Coil 205 Valve body 206 Energizing spring 207 Injection hole 209 Wiring 210 Connector 211 Terminal 213 Fuel supply port 214 Tubular members 302, 303, 403, 404 Iron core 304 Air gap 405 Magnetic flux direction 406, 407, 408, 501, 502, 503, 504 Mounting position 602, 608, 612, 618 Magnetic attractive force 603, 613 Displacement of valve body 604, 614, 617, 619, 620 Predetermined value 605, 615 Opening start timing 606 Boost voltage application stop timing 607, 609, 610 Predetermined current value 611 Current value 616 Timing 621 Predetermined time 623 624 valve closing delay time

Claims (7)

A first core member having magnetism, a coil wound so as to surround the first core member, and a second core for applying an electromagnetic force between the first core member when the coil is energized. In an electromagnetic force utilization device that uses a magnetic member having a core member and a magnetic circuit member that transmits magnetic flux to the first core member and the second core member,
A strain detector for detecting a strain in the passage direction of magnetic flux is provided in at least one of the first core member, the second core member, or the magnetic circuit member. Equipment that uses electromagnetic force. In the electromagnetic force utilization apparatus according to claim 1,
The first core member and the second core member are provided to face each other,
The magnetic circuit member is a solenoid that acts as a yoke that constitutes a part of a member that covers the periphery of the coil on a cross section in which the direction of the wire constituting the coil is a normal direction.
Either the first core member or the second core member is provided as a movable part,
An apparatus using electromagnetic force, wherein the strain detector is provided on a fixed member. In the electromagnetic force utilization apparatus according to claim 2,
The apparatus using electromagnetic force, wherein the strain detector is attached to an outer peripheral portion of the yoke. In the electromagnetic force utilization apparatus according to claim 2 or 3,
A fuel passage is provided inside the solenoid, the movable part is connected to a valve member, and the valve member is configured as a fuel injection valve that opens and closes.
An apparatus using electromagnetic force, wherein the strain detector is attached to a part different from a fuel passage part. In the electricity supply apparatus which supplies electricity to the electromagnetic force utilization apparatus of any one of Claims 1 thru | or 4,
An energizing apparatus, wherein at least a part of a waveform of a current energized to the coil is determined based on a strain value detected by the strain detector. In the electricity supply apparatus which supplies with electricity to the electromagnetic force utilization apparatus of Claim 4,
Comprising an input part of a signal of the strain detector attached to the fuel injection valve;
An energizing apparatus having a function of determining at least one portion of a drive current waveform energized to the fuel injection valve based on an input strain signal. The energization device according to claim 6,
An energization device that controls an energization current so that a signal related to strain obtained from the strain detector becomes a constant value.

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