JP2013224630A - Fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance accuracy of fuel injection control and to suppress increasing of power consumption in a fuel injection device in which an injection ratio is set high.SOLUTION: A fuel injection valve 10 opening a valve by attracting a needle valve 14 inserted into valve bodies 11, 12 by energization to coils has a first coil 16and a second coil 16as the coils, an attracting stroke of the needle valve 14 by the energization to the first coil 16is set smaller than an attracting stroke of the needle valve 14 by the energization to the second coil 16, only the first coil 16is energized in a range where a required injection quantity is small, and the first coil 16and the second coil 16are energized in a range where a required injection quantity is large.

Description

  The present invention relates to an engine fuel injection device, and more particularly to a fuel injection device suitable for shortening injection time, and belongs to the field of engine fuel supply technology.

  In recent years, gasoline engines for vehicles and the like have been proposed in which the compression ratio is set high and the temperature of the mixture is increased in the compression process so that the mixture is compressed and ignited in a low load region. According to this ignition method, the thermal efficiency in the low load region becomes high, and further improvement in fuel efficiency is expected compared to the lean burn method in which a conventional lean air-fuel mixture is spark-ignited.

  In this engine, ignition is performed by spark ignition in the high load region, but since the compression ratio is set high, the unburned mixture is self-ignited during the compression stroke, particularly in the high load low rotation region. There is a problem that ignition or knocking in which an unburned portion of the air-fuel mixture is locally self-ignited after the start of combustion is likely to occur.

  In response to this, by increasing the injection rate (injection amount per unit time) of the fuel injection valve and injecting in a short time at a timing near the compression top dead center, the time from the start of fuel injection to ignition is shortened. It is considered effective to do. In other words, premature ignition is suppressed by shortening the time from the start of injection to ignition, and it is considered that the agitation of the air-fuel mixture is promoted by the increase of the spraying speed due to the shortened injection time and knocking is suppressed. is there.

  In order to increase the injection rate of the fuel injection valve and shorten the fuel injection time, it is considered to increase the stroke amount of the valve body when the valve is opened.

  In Patent Document 1, in order to realize low fuel consumption by lean combustion at low load and high output by homogeneous combustion at high load, the stroke of the plunger is set in the open-type fuel injection valve. A switchable size is disclosed.

JP 2010-19194 A

  By the way, when the injection rate is increased, the fuel injection valve has a property that the control accuracy of the injection amount is lowered in a low load region where the injection amount is small.

  That is, as shown in FIG. 7A, the injection rate of the fuel injection valve increases according to the stroke of the valve body such as the needle valve after the start of the valve opening after the output of the injection command, and is constant at the maximum stroke amount. After a predetermined time has elapsed from when the injection command is output, the change characteristic with respect to time has a trapezoidal shape, but the injection rate at the time of valve opening increases and closes. There is a characteristic that the period during which the injection rate at the time of valve reduction tends to vary due to individual differences in valve opening speed.

  Looking at this as the total injection amount from the start of valve opening, as shown in FIG. 5B, the injection amount characteristic is shaded when the valve is opened and closed as shown in FIG. The inflection point P is formed with the injection amount corresponding to the area, and the region where the injection amount is smaller than the inflection point P is a region where the ratio of the variation amount to the injection amount is large.

  Therefore, as shown in FIG. 5B, it is necessary to set the minimum injection amount Qmin at the time of low load so that it is located on the higher injection amount side than the injection amount at the inflection point P. Thus, in order to shorten the injection time, if the stroke of the valve body is increased and the injection rate is increased, the hatched area in FIG. As shown, the inflection point is higher than the minimum injection amount Qmin. In this case, when the injection amount is low and the load is low, as shown by the symbol x, a state of injection occurs only in the region where the variation is large, and the control accuracy of the fuel injection amount is lowered.

  Accordingly, the present invention provides a fuel injection device that suppresses variations in the injection amount at low loads in a fuel injection device that is set to have a high injection rate, such as used in an engine that has a high compression ratio as described above. It is an object to improve control accuracy and suppress an increase in power consumption.

  In order to solve the above problems, the present invention is configured as follows.

  First, an invention according to claim 1 is provided in an engine, and a needle valve inserted in a valve body is sucked by energization of a coil to open the valve, and fuel is injected from a nozzle hole at the tip of the valve body into a combustion chamber. A fuel injection device for injecting, wherein the coil is provided with a first coil and a second coil, and the suction stroke of the needle valve by energizing the first coil depends on the suction stroke of the needle valve by energizing the second coil. An energization control means for energizing only the first coil in a region where the required injection amount is small and smaller than the suction stroke and energizing the first coil and the second coil in a region where the required injection amount is large. It is characterized by having.

  According to a second aspect of the present invention, in the first aspect of the present invention, the energization control unit is provided for the needle valve that is generated by energizing the first coil in a region where the first and second coils are energized. The energization of these coils is controlled so that the attraction force becomes larger than the attraction force generated by energization of the second coil.

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the energization control means is generated by energizing the first coil in a region energizing the first and second coils. The suction force for the needle valve is larger than the suction force required for starting the opening operation of the needle valve, and the suction force for the needle valve generated by energization of the second coil is required for starting the opening operation of the needle valve. The power supply to these coils is controlled so as to be smaller than the attraction force.

  With the above configuration, according to the first aspect of the invention, in the fuel injection device configured to suck and open the needle valve by energizing the coil, the first coil is provided in a region where the required injection amount is small. Since the needle valve suction stroke is reduced, the injection amount during the period when the injection rate increases when the valve is opened and during the period when the injection rate decreases when the valve is closed is smaller than when the stroke amount is large. Become. That is, the injection amount in a period that tends to vary is reduced, the ratio of the variation amount to the total injection amount is reduced, and the accuracy of fuel injection control is improved.

  Also, in the region where the required injection amount is large, the suction stroke of the needle valve is increased by energizing the second coil, so that the injection rate is increased and the required amount of fuel can be injected in a short time. For example, an engine that is required to shorten the fuel injection time in a high load region as the compression ratio increases is satisfied.

  According to the present invention, in the region where the required injection amount is large, the first coil is energized in addition to the second coil. Compared with the case where the stroke is realized, the power consumption is reduced.

  In other words, in order to start the valve opening operation of the needle valve in the valve closing state, the biasing force of the spring acting on the needle valve in the closing direction and the inside of the valve body through the gap corresponding to the stroke amount. However, if the needle valve has a large suction stroke and the gap becomes large, the current flowing through the coil is increased and generated in the coil. The attractive force, in other words, the strength of the magnetic field has to be increased, and the power consumption at the time of valve opening increases accordingly.

  Moreover, in order to make the magnetic force generated by energizing the coil act as an attractive force for the needle valve efficiently, the coil becomes large.

  Therefore, in the invention according to claim 1, when a large stroke of the needle valve is required, the first coil is energized together with the second coil and the suction stroke with respect to the needle valve, that is, the first gap is small. The suction force necessary for starting the valve opening operation is generated by energizing the coil, and this opens the valve at a lower current value than when the valve opening operation is started by energizing the second coil having a large suction stroke. It becomes possible to make it.

  Then, when the valve opening operation is started and the tip of the needle valve is separated from the seating surface, the urging force due to the fuel pressure disappears. After that, it is necessary to apply a relatively low current value to the second coil. The large stroke that is being done will be realized. As a result, the total power consumption required for valve opening in a region where the required injection amount is large is reduced, and the coil is made compact or the valve body is made compact.

  According to the invention of claim 2, when both the first and second coils are energized, the attraction force generated by energizing the first coil is greater than the attraction force generated by energizing the second coil. Since it is controlled so as to increase, the valve opening operation can be started by the suction force generated by energizing the first coil, and then the needle valve is moved by a predetermined stroke with a small suction force generated by applying the current to the second coil. Therefore, it is possible to reduce the energization current value to the second coil, and wasteful power consumption is suppressed.

  According to the invention of claim 3, when both the first and second coils are energized, the suction force generated by energizing the first coil is the suction required to start the valve opening operation of the needle valve. Since it is made larger than the force, the valve opening operation is surely started by energizing the first coil.

  And since the attraction | suction force by energization of the 2nd coil is made smaller than the attraction | suction force required for valve opening operation start, the useless power consumption by making the energization current value to this 2nd coil higher than necessary is suppressed. .

It is sectional drawing of the fuel injection valve in embodiment of this invention. It is a principal part expanded sectional view of the injection valve. It is a control block diagram of a fuel injection device concerning an embodiment of the present invention. It is explanatory drawing of the relationship between an attraction | suction stroke and the attraction | suction force required for a valve opening operation | movement start, and an electric current value. It is a time chart which shows the electricity supply control with respect to each coil. It is sectional drawing which shows the valve opening operation state of a fuel injection valve. It is explanatory drawing of the problem of a prior art.

  Hereinafter, embodiments of a fuel injection device according to the present invention will be described.

  FIG. 1 shows a configuration of a fuel injection valve 10 constituting a fuel injection device. A main body of the fuel injection valve 10 is a large-diameter cylindrical first valve body (hereinafter referred to as “first body”) 11. And a small-diameter cylindrical second valve body (hereinafter referred to as “second body”) 12 extending from one end of the first body 11 and closed at the tip, is connected by a coupling member 13.

  A needle valve (hereinafter referred to as “needle”) 14 that extends from the intermediate portion of the first body 11 to the distal end portion of the second body 12 along the center line thereof is provided in the first and second bodies 11 and 12. The fuel injection unit 15 is configured by the distal end portion 12 a of the second body 12 and the distal end portion 14 a of the needle 14.

Further, in the said first body 11, with the second body 12 side first coil 16 ₁ and the ₂ second coil 16 is housed, the first inner coil 16 ₁ tubular first stationary core 17 _1, the second inner coil 16 ₂ likewise ₂ cylindrical second fixed iron core 17 are disposed respectively.

Furthermore, between the first fixed core 17 ₁ and spacer 18 that is disposed in the counter second fixed core 17 ₂ side, and between the first fixed core 17 ₁ and the second fixed iron core 17 _2, respectively Ring-shaped first and second movable iron cores 19 ₁ and 19 ₂ are respectively provided with axial gaps X ₁ and X ₂ (see FIG. 2).

And the part located in the 1st body 11 of the needle 14 penetrates the 1st movable iron core 19 ₁ , the 1st fixed iron core 17 ₁ , the 2nd movable iron core 19 ₂ from the tip part 14a side, and A spring 20 is provided on the rear end side of the needle 14 to urge the needle 14 toward the distal end portion 14a, that is, in the valve closing direction.

Further, the first fixed iron core 17 ₁ side portion passing through the first movable iron core 19 ₁ of the needle 14, and a second fixed iron core 17 ₂ side of the portion penetrating the second movable iron core 19 _2, first, Second stepped portions 14 ₁ and 14 ₂ are provided, respectively.

Thus, the by first suction force generated by energization of the coil 16 ₁ together with the first movable iron core 19 ₁ is sucked to the first stationary core 17 ₁ side, via the first stepped portion 14 _1, a needle 14 is a stroke by the valve opening direction distance against the biasing force or the like corresponding to the gap X ₁ of the spring 20, likewise, the second movable iron core by the suction force generated by energization of the second coil 16 ₂ with 19 ₂ is sucked to the first fixed core 17 ₂ side, the second through the stepped portion 14 _2, the distance the needle 14 corresponds to the gap X ₂ against the biasing force or the like of the spring 20 Only strokes in the valve opening direction.

In this case, as shown enlarged in FIG. 2, the gap _X 1, _{X 2 is,} X 1 <a is set to the relationship _{X 2,} therefore, the needle 14 due to energization of the first to the coil 16 ₁ stroke of the valve opening direction is smaller than the stroke of the same direction of the needle 14 due to energization of the second to the coil 16 _2.

  On the other hand, the fuel injection portion 15 composed of the second body tip portion 12a and the needle tip portion 14a is a cone provided inside the wall surface of the second body tip portion 12a as shown in an enlarged view in FIG. The needle tip portion 14a, which is also conically shaped, is configured to close and open when the needle 14 contacts and separates according to the movement of the needle 14.

  When the valve is opened, the second body 12 passes from a pipe (not shown) connected to the connector 21 at the rear end of the first body 11 via a fuel passage (not shown) in the first body 11. The high-pressure fuel pumped to the fuel reservoir 12c between the needle 14 and the needle 14 mists from the plurality of nozzle holes 12d... 12d provided on the wall surface of the second body tip 12a to the outside (combustion chamber). It is made to be injected.

  In addition to the fuel injection valve 10 having the above configuration, as shown in FIG. 3, the fuel injection device 1 according to this embodiment includes a fuel control unit 30.

The fuel control unit 30 is provided in the engine control unit, inputs various signals indicating the operating state of the engine, and the fuel injection valve so as to obtain an injection amount required according to the operating state indicated by these signals. Pulse-shaped control currents are output to the ten first and second coils 16 ₁ and 16 ₂ .

  Next, the control current output operation of the fuel control unit 30 will be specifically described.

  First, the relationship between the energization amount to the coil and the stroke amount of the needle will be explained. Generally, in order to start the valve opening operation of the needle in the valve closing state, the spring is applied to the needle in the closing direction. It is necessary to apply a suction force that overcomes the force and the fuel pressure in the valve body to the needle. In this case, even if the suction force generated by energizing the coil is the same, the larger the stroke amount, the movable iron core Since the gap between the core and the fixed iron core is large, the suction force actually acting on the needle is small.

  Therefore, as shown in FIG. 4 (a), in order to apply the suction force necessary for starting the valve opening operation to the needle, the suction force generated by energization of the coil, in other words, the value of the energization current to the coil. Or, the strength of the magnetic field generated by this must be increased as the stroke amount increases.

As a result, as shown in FIG. (B), as compared to the current value I ₁ at which to open at the energization of the first coil 16 _one stroke amount is small, the stroke amount is large in the second to the coil 16 ₂ It is it is necessary to increase the current value I ₂ is supplied to the energization start early towards the time for opening energization, in the latter case, power consumption is increased at the time of valve opening, also, the magnetic force generated in the coil to act effectively as a suction force to the needle, which leads to a second size of the coil 16 _2.

Therefore, the control unit 30 of the fuel injection device 1, first, when the amount of the required injection is small, i.e., when sufficient equal stroke the gap X ₁ towards stroke amount is small the needle 14, FIGS. 5 (a) as shown in, the first coil 16 _1, first, energized by the current value I ₁ required valve opening operation start when the stroke amount is small, then the current value, the needle 14 stroke X _{It is} moved by ₁ and lowered to the current value I ₁ ′ necessary for holding in that state. The hold up time T ₁ corresponding to this state to the required injection amount has elapsed. At this time, does not output the control current for the second coil 16 _2.

Thus, in the fuel injection valve 10, as shown in FIG. 6 (a), by the magnetic force generated by the energization of the current value I ₁ of the first coil 16 _1, the first movable iron core 19 ₁ is first fixed is attracted to the iron core 17 ₁ side, via the first stepped portion 14 _1, the tip portion 14a of the needle 14 is separated from the seat surface 12b against the biasing force and the fuel pressure of the spring 20, indicated by the symbol a as such, the needle 14 is moved by the stroke amount equivalent to the gap X _1, the first movable iron core 19 ₁ is adsorbed by the first end surface of the fixed iron core 17 _1.

By this state is maintained until the time T ₁ is elapsed, the injection rate corresponding to the stroke amount X _1, from the tip of the nozzle hole 12d ... 12d of the second body 12, relatively requested A small amount of fuel is injected.

On the other hand, many required injection amount, when it is required to inject a short time this, i.e., when it is necessary to move the needle 14 by a large stroke X _2, as shown in FIG. 5 (b), the 1 to coil 16 _1, first, as when the amount required injection is small, energized by the current value _{I 1,} then ends the energization of the first coil 16 _1.

Further, with respect to the second coil 16 _2, delays the same time or slightly timing than this energization start and to the first coil, the needle 14 tip 14a is in a state of being separated from the seat surface 12b by stroke X ₂ Energization is performed at a current value I ₂ ′ required for movement, and this state is maintained until a time T ₂ corresponding to the required injection amount elapses.

Note that the current value I _{2 ',} since it is only necessary to move the needle 14 against the biasing force of the spring 20, than the current value I ₁ for a valve opening operation start energizing the first coil 16 ₁ small, there is no great difference between the subsequent current value _{I 1} 'for the first coil 16 _1.

Thus, in the fuel injection valve 10, as shown in FIG. 6 (b), by the suction force generated by energization of the current value I ₁ of the first coil 16 _1, similar to when the amount of required injection is small, the 1 movable iron core 19 ₁ is attracted to the first stationary core 17 ₁ side, via the first stepped portion 14 _1, the tip portion 14a is the seat surface 12b of the needle 14 against the biasing force and the fuel pressure of the spring 20 Spaced apart.

In parallel with this, the suction force generated by energization of the current value I2 'of the second to the coil 16 _{2, 2} second movable core 19 is attracted to the second fixed core 17 ₂ side, with the second stage via the part 14 _2, the needle 14 is moved by the stroke amount equivalent to the gap X ₂ against the urging force of the spring 20, as shown at b, ₂ a second movable iron core 19 and the second fixed iron core 17 ₂ is adsorbed on the end face.

By this state is maintained by the time T _2, a large injection rate corresponding to the stroke amount X _2, the second body 1 ₂ of the tip of the injection holes 12d ... 12d, the requested quantity of fuel Is injected.

As described above, so that the stroke of the needle 14 is changed according to the required injection amount, large when the stroke amount X ₂ is required, the energization of the first coil 16 ₁ for a small stroke Accordingly, since to separate the front end portion 14a of the needle 14 from the seating surface 12b, as compared with the case of starting the opening operation only by energizing the second coil 16 ₂ for a large stroke shown in FIG. 4 (b), total It is possible to reduce the energization amount.

  As a result, when a high injection rate is required for shortening the injection time, the power consumption at the time of valve opening is reduced, and the magnetic force generated in the coil is effectively applied to the needle as an attractive force. There is no need to increase the size of the coil.

  As described above, according to the present invention, for example, in an engine that employs a high compression ratio, in order to suppress premature wearing fire or knocking in a high load low rotation region, the needle stroke amount is increased and injection is performed. When the rate is increased, an increase in power consumption and an increase in size of the fuel injection valve are avoided. Therefore, it may be suitably used in the field of manufacturing this type of engine or in the field of manufacturing technology of a vehicle equipped with this type of engine.

DESCRIPTION OF SYMBOLS 1 Fuel injection apparatus 10 Fuel injection valve 14 Needle 16 ₁ , 16 ₂ 1st, 2nd coil 30 Control part

Claims (3)

A fuel injection device that is provided in an engine and sucks and opens a needle valve inserted into a valve body by energizing a coil, and injects fuel into a combustion chamber from a nozzle hole at the tip of the valve body,
The coil includes a first coil and a second coil,
The suction stroke of the needle valve by energizing the first coil is made smaller than the suction stroke of the needle valve by energizing the second coil,
A fuel injection system comprising an energization control means for energizing only the first coil in a region where the required injection amount is small and energizing the first coil and the second coil in a region where the required injection amount is large. apparatus.   The energization control means is configured such that, in a region where the first and second coils are energized, an attraction force to the needle valve generated by energizing the first coil is larger than an attraction force generated by energizing the second coil. The fuel injection device according to claim 1, wherein energization of these coils is controlled.   In the energization control means, in the region where the first and second coils are energized, the attraction force to the needle valve generated by energizing the first coil is greater than the attraction force required to start the valve opening operation of the needle valve. The energization of these coils is controlled so that the attraction force to the needle valve generated by energization of the second coil is smaller than the attraction force required to start the opening operation of the needle valve. The fuel injection device according to claim 1 or 2.

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