JP2013167187A - Method of detecting high pressure fuel pump reference point, and common rail type fuel injection control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a correlation between an ejection timing of fuel of a high pressure pump and a rotation phase of an engine to be easily detected.SOLUTION: An output signal of a pressure sensor 11 is input by an electronic control unit 4 when starting an engine 3, a rail pressure with regard to an elapse of time from the engine start is calculated based on the output signal, a change in a rail pressure slope which is an amount of change in the rail pressure per unit time is calculated based on the calculated rail pressure, as an actual rail pressure slope characteristic, a comparison between the actual rail pressure slope characteristic and a reference rail pressure slope characteristic which has been acquired beforehand and becomes a reference is performed, and on the basis of the comparison result, a deviation between a top dead center of a plunger as a reference point of a high pressure pump 7 and a top dead center of the engine is detected.

Description

  The present invention relates to a common rail fuel injection control device, and more particularly to a device that aims to eliminate a rotational phase shift between a high-pressure fuel pump and an engine.

As a fuel injection control device for an internal combustion engine such as a diesel engine, a fuel is pressurized by a high-pressure pump, and is pumped and stored in a common rail as an accumulator. Common rail fuel injection control devices that enable high-pressure fuel injection to engines are known for their excellent fuel efficiency and emission characteristics. Various improvements to operating characteristics have been proposed and put to practical use. ing.
In such a common rail type fuel injection control device, the high-pressure pump is a so-called mechanical type, and is connected to the output shaft of the engine to obtain a driving force, whereby the plunger is reciprocated to perform intake and discharge of fuel. It has come to be.

In such a configuration, it is desirable that the high pressure pump and the engine be assembled so that the fuel discharge timing by the high pressure pump and the rotational phase of the engine have a predetermined relationship from the viewpoint of reducing emissions.
However, the assembly work in which the discharge timing of the high-pressure pump and the rotational phase of the engine have a predetermined relationship not only requires work time but also requires skill in the work, leading to an increase in the cost of the apparatus. There are problems such as.
As a measure for solving such a problem, for example, a device that can detect the rotational position of the top dead center of the plunger of the high-pressure fuel pump based on the pressure change at the time of fuel discharge in a high rail pressure state is proposed. (See, for example, Patent Document 1).

Japanese Patent Laying-Open No. 2011-163138 (page 64-10, FIGS. 1 to 3)

  However, in the above-mentioned measures, when detecting the rotational position of the top dead center of the plunger of the high-pressure fuel pump, the rail pressure must be in a high rail pressure state. Since it is based on a common rail fuel injection control device having a fuel leak in the high-pressure fuel section, there is a problem that it cannot be applied to a device in which the fuel leak is sufficiently suppressed.

  The present invention has been made in view of the above circumstances, and a high-pressure fuel pump reference point detection method and a common rail fuel injection that can easily detect the relative relationship between the fuel discharge timing of the high-pressure pump and the rotational phase of the engine. A control device is provided.

In order to achieve the above object of the present invention, a high pressure pump reference point detection method according to the present invention includes:
Fuel in the fuel tank is pressurized and pumped to a common rail by a high-pressure pump, enabling high-pressure fuel injection to the engine via a fuel injection valve connected to the common rail, and a metering valve upstream of the high-pressure pump And a high-pressure pump reference point detection and detection method in a common rail fuel injection control device in which the metering valve is driven and controlled by an electronic control unit to control the rail pressure of the common rail,
When the engine is started, the change in rail pressure with respect to various elapsed times is measured, and the change in the rail pressure, which is the amount of change in the rail pressure with respect to unit time, is calculated as the actual rail pressure slope characteristic based on the measurement results. The deviation between the top dead center of the plunger as the reference point of the high-pressure pump and the top dead center of the engine is detected by comparing the actual rail pressure slope characteristic with a reference rail pressure slope characteristic that is acquired in advance. It is comprised so that it may do.
In order to achieve the above object of the present invention, a common rail fuel injection control device according to the present invention includes:
Fuel in the fuel tank is pressurized and pumped to a common rail by a high-pressure pump, enabling high-pressure fuel injection to the engine via a fuel injection valve connected to the common rail, and a metering valve upstream of the high-pressure pump A common rail fuel injection control device configured such that the metering valve is driven and controlled by an electronic control unit to control the rail pressure of the common rail,
The electronic control unit is
At the time of starting the engine, an output signal of a pressure sensor is input, and based on the output signal of the pressure sensor, a rail pressure with respect to the passage of time from the time of starting the engine is calculated, and based on the calculated rail pressure The change in the rail pressure, which is the amount of change in the rail pressure per unit time, is calculated as the actual rail pressure gradient characteristic, and the actual rail pressure gradient characteristic is compared with a reference rail pressure gradient characteristic that is acquired in advance as a reference. The displacement between the top dead center of the plunger as the reference point of the high pressure pump and the top dead center of the engine is detected based on the comparison result.

According to the present invention, the fuel discharge timing of the high-pressure pump and the engine rotation phase can be easily detected, so that the assembly state of the high-pressure pump and the engine in the manufacturing process can be made arbitrary, and the assembly work in the manufacturing process is simplified. The cost of the apparatus can be reduced.
In addition, since the fuel injection by the fuel injection amount corrected based on the relative relationship between the detected fuel discharge timing of the high-pressure pump and the rotational phase with the engine is enabled, the assembly state of the high-pressure pump and the engine in the manufacturing process can be changed. Even if optional, highly reliable fuel injection control is possible, and stable and reliable operation of the apparatus can be ensured.

It is a block diagram which shows the structural example of the common rail type | mold fuel-injection control apparatus in embodiment of this invention. It is a subroutine flowchart which shows the procedure of the high pressure fuel pump reference point detection process in embodiment of this invention. It is a characteristic diagram which shows the change characteristic of the rail pressure from the engine starting calculated | required in the high pressure fuel pump reference point detection process in embodiment of this invention. It is a characteristic diagram which shows the example of the actual rail pressure inclination characteristic acquired in the high pressure fuel pump reference point detection process in embodiment of this invention with the reference rail pressure inclination characteristic. It is a characteristic diagram which shows typically the example of a change characteristic of energization time and fuel injection quantity. FIG. 6A is a schematic diagram schematically showing a change example of the fuel injection amount when the phases of the engine and the high-pressure pump coincide with each other, and a change example of the discharge amount of the high-pressure pump. FIG. 6B is a schematic diagram schematically showing an example of a change in the discharge amount of the high-pressure pump. FIG. 7A is a schematic diagram schematically showing a change example of the fuel injection amount and a change example of the discharge amount of the high pressure pump when the phases of the engine and the high pressure pump are shifted, and FIG. 7A is a change example of the fuel injection amount. FIG. 7B is a schematic diagram schematically showing a change example of the discharge amount of the high-pressure pump. It is a characteristic diagram which shows typically an example of the phase shift versus fuel change amount characteristic beforehand required for execution of the high-pressure fuel pump reference point detection processing in the embodiment of the present invention. FIG. 9 is an explanatory diagram for explaining that the phase shift vs. fuel change amount characteristic shown in FIG. 8 is one of the change characteristics of energization time and fuel injection amount. It is explanatory drawing explaining the case where the phase shift versus fuel change amount characteristic shown by FIG. 8 is acquired at several points of the energization time and the change characteristic of the fuel injection amount. FIG. 7 is a characteristic diagram showing a correction amount change characteristic of a fuel injection amount with respect to a phase shift having a characteristic opposite to the phase shift versus fuel change amount characteristic.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 11.
The members and arrangements described below do not limit the present invention and can be variously modified within the scope of the gist of the present invention.
First, a configuration example of a common rail fuel injection control device to which the high-pressure fuel pump reference point detection method according to the embodiment of the present invention is applied will be described with reference to FIG.
The common rail fuel injection control device according to the embodiment of the present invention includes a high pressure pump device 50 that pumps high pressure fuel, a common rail 1 that stores high pressure fuel pumped by the high pressure pump device 50, and a common rail 1 that is supplied from the common rail 1. And a plurality of injectors 2-1 to 2-n for injecting and supplying high pressure fuel to the cylinders of the engine 3, and an electronic control unit ("ECU" in FIG. 4) as a main component.
Such a configuration itself is the same as the basic configuration of this type of fuel injection control apparatus that has been well known.

The high-pressure pump device 50 has a known and well-known configuration with a supply pump 5, a metering valve 6, and a high-pressure fuel pump (hereinafter referred to as “high-pressure pump”) 7 as main components.
In this configuration, the fuel in the fuel tank 9 is pumped up by the supply pump 5 and supplied to the high-pressure pump 7 through the metering valve 6. As the metering valve 6, an electromagnetic proportional control valve is used, and the energization amount is controlled by the electronic control unit 4, so that the flow rate of the fuel supplied to the high-pressure pump 7, in other words, the discharge of the high-pressure pump 7. The amount is to be adjusted.

A return valve 8 is provided between the output side of the supply pump 5 and the fuel tank 9 so that surplus fuel on the output side of the supply pump 5 can be returned to the fuel tank 9. .
The supply pump 5 may be provided separately from the high-pressure pump device 50 on the upstream side of the high-pressure pump device 50 or may be provided in the fuel tank 9.
The fuel injection valves 2-1 to 2-n are provided for each cylinder of the engine 3, and are supplied with high-pressure fuel from the common rail 1, and perform fuel injection by injection control by the electronic control unit 4. Yes. As the fuel injection valves 2-1 to 2-n in the embodiment of the present invention, for example, a so-called electromagnetic valve type that has been conventionally used is suitable.

The electronic control unit 4 has, for example, a microcomputer having a known and well-known configuration, a storage element (not shown) such as a RAM and a ROM, and fuel injection valves 2-1 to 2-n. The main component is a circuit (not shown) for energizing and driving, and a circuit (not shown) for energizing and driving the metering valve 6 and the like.
In addition to the detection signal of the pressure sensor 11 that detects the pressure of the common rail 1 being input to the electronic control unit 4, various detection signals such as the engine speed, the accelerator opening, the outside air temperature, and the atmospheric pressure are received by the engine 3. It is input to be used for the operation control and fuel injection control.

Next, the high-pressure fuel pump reference point detection process of the embodiment of the present invention executed by the electronic control unit 4 will be described with reference to FIGS.
First, the high-pressure pump reference point detection process in the embodiment of the present invention will be generally described.
In the common rail fuel injection control apparatus described above, as is well known, the high-pressure pump 7 is caused to reciprocate a plunger (not shown) by the rotational driving force of the engine 3 so as to suck and discharge fuel. It is what is supposed to be done. Therefore, in order to perform accurate fuel injection control, it is necessary to assemble the high pressure pump 7 and the engine 3 in advance so that the fuel discharge timing by the high pressure pump 7 and the rotational phase of the engine 3 have a predetermined relationship. However, this assembling work not only takes time but also requires skill. In addition, if the skill level of the operator is not sufficient even after the assembly, the assembly with the desired accuracy may not be ensured.

In the high-pressure pump reference point detection process according to the embodiment of the present invention, how much the correlation between the fuel discharge timing of the high-pressure pump 7 and the rotational phase of the engine 3 deviates from the reference correlation. Is detected when the engine 3 is started, and the fuel injection amount is corrected based on the detection result, thereby enabling fuel injection at the originally required fuel injection amount.
Therefore, by applying this high-pressure pump reference point detection process to the common rail fuel injection control device, when the high-pressure pump 7 is assembled in the production line of the engine 3, the fuel discharge timing by the high-pressure pump 7 and the engine 3 It is possible to assemble arbitrarily without considering the mutual relationship between the rotational phases of the two.
Conventionally, when the high-pressure pump is assembled to the engine, both the camshaft of the high-pressure pump and the drive shaft of the engine or both of them are used to match the rotational phase of the high-pressure pump and the rotational phase of the engine. However, by applying the present invention, it becomes unnecessary to apply the present invention, so that the manufacturing becomes easier and the manufacturing cost can be reduced.

Hereinafter, the high-pressure pump reference point detection processing procedure in the embodiment of the present invention will be specifically described with reference to FIG. 2. First, the start of the engine 3 is confirmed in the electronic control unit 4 (FIG. 2). When the rail pressure is measured (see step S102), the rail pressure is measured (see step S104 in FIG. 2).
The high-pressure pump reference point detection process in the embodiment of the present invention substantially corresponds to the discharge and suction operations of the high-pressure pump 7 with the passage of time until the rail pressure reaches the target rail pressure after the engine is started. Thus, for example, as shown in FIG. 3, since the phenomenon of repeatedly increasing and stagnating (or decreasing) is utilized, in step S104, the rail pressure at the time of starting the engine is used. Change data is acquired.

In FIG. 3, the portion where the rail pressure increases with the passage of time corresponds to the fuel discharge stroke of the high-pressure pump 7, and the portion where the rail pressure stagnates or gradually decreases indicates the fuel of the high-pressure pump 7. Corresponds to the inhalation stroke.
The rail pressure is measured by reading the output signal of the pressure sensor 11 into the electronic control unit 4 at predetermined time intervals until the rail pressure reaches the target rail pressure or until it reaches a predetermined allowable range with respect to the target rail pressure. And stored in an appropriate storage area of the electronic control unit 4. The predetermined time interval should be appropriately selected in consideration of the processing capability of the electronic control unit 4 and the like. For example, the output signal of the pressure sensor 11 is read every 1 ms for a total of 500 ms. That is, it is conceivable to read 500 times, but of course it is not necessary to be limited to this.

Next, the rail pressure gradient is calculated for the rail pressure change acquired as described above (see step S106 in FIG. 2).
That is, the slope of the rail pressure (rail pressure change amount) is calculated as a result of dividing the rail pressure change amount Δp in unit time Δt.
In the embodiment of the present invention, in the common rail fuel injection device as a reference in which the correlation between the fuel discharge timing of the high-pressure pump 7 and the rotational phase of the engine 3 is set to a predetermined relationship, the above-described engine start-up is performed. It is assumed that the inclination of the rail pressure is acquired in advance and stored as reference data (hereinafter referred to as “reference rail pressure inclination” for convenience of description) in an appropriate storage area of the electronic control unit 4. The predetermined relationship between the fuel discharge timing of the high-pressure pump 7 and the rotational phase of the engine 3 is, for example, that the top dead center of the engine 3 and the top dead center of the plunger (not shown) of the high-pressure pump 7 coincide. The assembled state is suitable for detecting a shift between the top dead center of the engine 3 and the top dead center of the high-pressure pump 3 plunger (not shown) in an actual device, as will be described later.

FIG. 4 shows an example of the characteristic of the reference rail pressure gradient described above by a solid characteristic line. In this example, the rail pressure in the reference common rail fuel injection control apparatus assembled so that the top dead center of the engine 3 and the top dead center of the plunger (not shown) of the high-pressure pump 7 coincide with each other is described. This shows an example of a change in the slope of. In FIG. 4, the vertical axis represents the rail pressure gradient Δp / Δt, and the horizontal axis represents the rotation angle of the high-pressure pump 7.
The rail pressure gradient Δp / Δt represented by the solid line increases with a positive value as the rotational angle changes when fuel pumping starts as the high-pressure pump 7 starts rotating, and reaches a relatively short time. Reach a certain level for a while. Here, the rail pressure gradient Δp / Δt is in a constant state only as an example, and the change in this portion is determined by the cam profile in the high-pressure pump 7 and is not necessarily constant. .
Then, it starts to decrease slightly near the top dead center (indicated as “TDC” in FIG. 4), and when the plunger (not shown) of the high pressure pump 7 reaches the top dead center, Δp / Δt becomes zero, and the high-pressure pump 7 shifts to the suction stroke. In the intake stroke, Δp / Δt increases with a negative value as the rotational angle changes, reaches a negative value for a relatively short time, and thereafter remains constant for a while. Then, Δp / Δt starts to increase slightly before the end of the suction stroke, and Δp / Δt has a characteristic of just over zero when the suction stroke is switched to the discharge stroke.

In the reference rail pressure gradient characteristic described above, the horizontal axis indicates the pump angle, which is obtained based on the rotational phase of the engine 3.
That is, first, the pump angle corresponds to the angle of the rotary shaft of the high-pressure pump 7, in other words, the position of the plunger (not shown).
On the other hand, the rail pressure change shown in FIG. 3 is assembled so that the top dead center of the engine 3 and the top dead center of the plunger (not shown) of the high pressure pump 7 coincide as described above. The relative relationship between the rotation angle of the rotating shaft of the engine 3 and the pump angle of the high-pressure pump 7 is obtained in advance, and the rotation angle of the engine 3 is determined by the engine rotation speed. Since it can be grasped by the output signal of the rotation sensor (not shown) to be detected, the pump angle of the high-pressure pump 7 can be eventually replaced based on the rotation angle of the engine 3.

On the other hand, the rail pressure gradient Δp / Δt actually calculated in step S106, that is, the common rail fuel injection control attached without considering the relative relationship between the fuel discharge timing of the high-pressure pump 7 and the rotational phase of the engine 3 is considered. The slope Δp / Δt of the rail pressure of the apparatus (hereinafter referred to as “actual rail pressure slope” for convenience of explanation) is, for example, as shown by the dotted characteristic line in FIG.
Therefore, after the above-described actual rail pressure slope calculation, comparison with the reference rail pressure slope is performed (see step S108 in FIG. 2).

  First, in FIG. 4, the actual rail pressure gradient characteristic represented by the dotted line has a tendency (similar shape) that is substantially the same as the reference rail pressure gradient characteristic represented by the solid line in the same figure. However, there is a deviation in the pump angle with respect to the reference rail pressure gradient characteristic. That is, when the reference rail pressure gradient characteristic is compared with the actual rail pressure gradient characteristic at the inflection point where the positive value of Δp / Δt starts to decrease from a substantially constant state, for example, the reference rail pressure gradient of FIG. In contrast to the inflection point a at which the positive value of Δp / Δt starts to decrease from a substantially constant state, the similar inflection point b in the characteristic line of the actual rail pressure gradient is the inflection point a. On the other hand, there is a deviation of Δφ in the pump angle.

This deviation is due to the fact that it is arbitrarily attached without considering the relative relationship between the fuel discharge timing of the high-pressure pump 7 and the rotational phase of the engine 3, and the magnitude of the deviation is the plunger of the high-pressure pump 7 (not shown). ) Shows the magnitude of deviation between the top dead center (reference point) and the plunger (not shown) of the engine 3.
Accordingly, the magnitude of the above-described deviation, that is, the deviation amount is calculated by comparing the actual rail pressure inclination characteristic and the reference rail pressure inclination characteristic (see step S110 in FIG. 2).
As described above, the shift amount is preferably obtained by comparison at the position of the inflection point.
Here, the positions of the inflection points are identified from the calculated change in Δp / Δt, for example, the inflection points a and b described above are points where Δp / Δt starts to decrease from a constant value. Is possible. Note that the inflection point used as a reference when calculating the deviation amount may be either the inflection point a or the inflection point b.

Next, an injection amount correction coefficient that is a coefficient for correcting the fuel injection amount is determined based on the deviation amount obtained as described above (see step S112 in FIG. 2). Then, a series of processes are completed by the process of step S112, and the process returns to the main routine (not shown), the fuel injection amount is corrected using the injection amount correction coefficient determined in step S112, and the fuel injection is performed. Will be done.
Here, the injection amount correction coefficient is based on the correlation between the deviation amount acquired in advance based on the common rail type fuel injection control device used as a reference and the correction of the required fuel injection amount, as described below. Is determined.

Next, the correlation between the deviation amount acquired in advance and the necessary correction of the fuel injection amount will be described with reference to FIGS.
First, as one of data to be acquired in advance, there is a fuel injection amount characteristic with respect to the energization time of the fuel injection valves 2-1 to 2-n. FIG. 5 shows an example of such fuel injection characteristics. The fuel injection amount characteristic is preferably acquired for each of a plurality of rail pressures (P1, P2,..., Pn) (see FIG. 5). In FIG. 5, ET represents the energization time, and Q represents the fuel injection amount.

In obtaining the fuel injection amount characteristic, it is preferable that the conditions of the apparatus when obtaining the reference rail pressure gradient described above be the same. That is, it is preferable that the engine 3 and the plunger (not shown) of the high-pressure pump 7 be assembled so that the top dead center thereof coincides (see FIG. 6). FIG. 6 schematically shows that the top dead center of the engine 3 and the top dead center of the plunger (not shown) of the high pressure pump 7 coincide with each other. In FIG. FIG. 6B schematically shows changes in compression and suction strokes associated with rotation, and changes in fuel discharge and suction strokes associated with rotation of the high-pressure pump.

Next, the phase difference between the top dead center of the engine 3 and the top dead center of the high-pressure pump 7 is shifted to obtain the change amount of the fuel injection amount (hereinafter referred to as “phase shift versus fuel change amount characteristic” for convenience of explanation).
This phase shift vs. fuel change amount characteristic is such that the top dead center of the engine 3 and the top dead center of the high-pressure pump 7 are matched, and the top dead center of the engine 3 is based on a state in which a certain rail pressure and a certain fuel injection amount are injected. This is a result of measuring the change amount of the fuel injection amount when the phase of the top dead center of the high-pressure pump 7 is variously shifted (see FIG. 7). In addition, when shifting the phase, it is preferable to carry out with a fine pitch, but the size of the pitch is not limited to a specific value and should be arbitrarily set. Further, the range for shifting the phase is preferably 360 degrees. Note that the phase shift range is 360 degrees in the case of the 1 cam configuration, 180 degrees in the 2 cam configuration, and 120 degrees in the 3 cam configuration.

FIG. 8 shows an example of such a phase shift vs. fuel change amount characteristic. The horizontal axis indicates the phase shift from a state where the top dead center of the engine 3 and the top dead center of the high-pressure pump 7 coincide with each other. The vertical axis indicates the change amount ΔQ of the fuel injection amount with reference to the fuel injection amount in a state where the top dead center of the engine 3 and the top dead center of the high pressure pump 7 coincide with each other.
In FIG. 8, “E_TDC” means the top dead center of the engine 3, and “P_TDC” means the top dead center of the high-pressure pump 7.

The characteristic line in FIG. 8 is a case where a phase shift is caused with reference to an arbitrarily selected rail pressure and energization time (fuel injection amount), and is one point expressed by the fuel injection amount characteristic (FIG. 9). Therefore, a plurality of similar characteristics are obtained by variously changing the rail pressure and the energization time (fuel injection amount) (see FIG. 10).
FIG. 10 shows the point where the acquired phase shift vs. fuel change amount characteristic is the fuel injection amount characteristic as a white point.
Therefore, the correction of the fuel injection amount necessary for canceling the change in the fuel injection amount caused by the phase shift to obtain the original fuel injection amount is obtained by correcting the phase shift versus the fuel change obtained earlier with respect to the phase shift. The quantity characteristic is opposite to the characteristic. FIG. 11 shows an example. In FIG. 11, the dotted characteristic line represents the correction amount of the fuel injection amount with respect to the phase shift, and the phase shift versus fuel change amount characteristic represented by the solid line in FIG. In contrast, the characteristics are opposite.
As described above, since a plurality of phase shift vs. fuel change amount characteristics are acquired, the above-described reverse characteristics are obtained for each phase shift vs. fuel change amount characteristic.

Next, an injection amount correction coefficient is calculated based on the correction amount of the fuel injection amount for each phase shift acquired as described above, and this is stored in an appropriate storage area of the electronic control unit 4.
First, assuming that a fuel injection amount that is assumed to have no phase shift is Qs, a corrected fuel injection amount is Qm, and an injection amount correction coefficient is Km, an embodiment of the present invention It is assumed that the injection amount correction coefficient in is used as Qm = Km × Qs.

On the other hand, the correction amount ΔQ described above is an amount to be added to or subtracted from the fuel injection amount Qs when there is no phase shift. That is, the corrected fuel injection amount Qm is obtained as Qm = Qs ± ΔQ, which can be organized as Qm = Qs ± ΔQ = (1 ± ΔQ / Qs) Qs.
Therefore, the injection amount correction coefficient Km is obtained as Km = (1 ± ΔQ / Qs).

The injection amount correction coefficient Km obtained as described above is the actual rail pressure when the injection amount correction coefficient Km is obtained, and at that time, the target fuel injection amount calculated by the fuel injection control process as in the conventional case. At this time, the phase shift amount obtained in the process of the previous step S110 is input, and a so-called conversion table is read out from the electronic control unit 4 so that the injection amount correction coefficient Km corresponding thereto is read out. It is preferable to store in advance in an appropriate storage area so that it can be used in the previous step S112.
Since the injection amount correction coefficient Km obtained based on the measurement data as described above is discrete with respect to the rail pressure and the target fuel injection amount, the lacking portion is obtained by a general complement method or the like. It is preferable to do so.

  It is suitable for a common rail type fuel injection control apparatus in which assembly work is desired without considering the phase of the engine top dead center and the top dead center of the high pressure pump.

DESCRIPTION OF SYMBOLS 1 ... Common rail 2-1 to 2-n ... Fuel injection valve 3 ... Engine 4 ... Electronic control unit 7 ... High pressure pump

Claims (6)

Fuel in the fuel tank is pressurized and pumped to a common rail by a high-pressure pump, enabling high-pressure fuel injection to the engine via a fuel injection valve connected to the common rail, and a metering valve upstream of the high-pressure pump And a high-pressure pump reference point detection and detection method in a common rail fuel injection control device in which the metering valve is driven and controlled by an electronic control unit to control the rail pressure of the common rail,
When the engine is started, the change in rail pressure with respect to various elapsed times is measured, and the change in the rail pressure, which is the amount of change in the rail pressure with respect to unit time, is calculated as the actual rail pressure slope characteristic based on the measurement results. The deviation between the top dead center of the plunger as the reference point of the high-pressure pump and the top dead center of the engine is detected by comparing the actual rail pressure slope characteristic with a reference rail pressure slope characteristic that is acquired in advance. A high-pressure pump reference point detection method characterized by: The reference rail pressure slope characteristic is based on the rail pressure change characteristic with respect to the elapsed time measured at the time of starting the engine in a state where the top dead center of the high pressure pump and the top dead center of the engine are matched. The amount of change in pressure is calculated according to the rotation angle of the rotary shaft of the high-pressure pump,
By detecting the deviation between the top dead center of the plunger as the reference point of the high-pressure pump and the top dead center of the engine by comparing the actual rail pressure inclination characteristic and the reference rail pressure inclination characteristic, a predetermined inflection point is used. 2. The high pressure pump reference point detecting method according to claim 1, wherein the position is compared by comparing the positions in the respective rail pressure gradient characteristics and determining the positional deviation.   The fuel injection amount correction coefficient for the detected displacement is calculated using a predetermined injection amount correction coefficient conversion table, and fuel injection by the corrected fuel injection amount is enabled. Item 3. The high pressure pump reference point detection method according to Item 2. Fuel in the fuel tank is pressurized and pumped to a common rail by a high-pressure pump, enabling high-pressure fuel injection to the engine via a fuel injection valve connected to the common rail, and a metering valve upstream of the high-pressure pump A common rail fuel injection control device configured such that the metering valve is driven and controlled by an electronic control unit to control the rail pressure of the common rail,
The electronic control unit is
At the time of starting the engine, an output signal of a pressure sensor is input, and based on the output signal of the pressure sensor, a rail pressure with respect to the passage of time from the time of starting the engine is calculated, and based on the calculated rail pressure The change in the rail pressure, which is the amount of change in the rail pressure per unit time, is calculated as the actual rail pressure gradient characteristic, and the actual rail pressure gradient characteristic is compared with a reference rail pressure gradient characteristic that is acquired in advance as a reference. The common rail fuel injection control apparatus is configured to detect a deviation between a top dead center of a plunger as a reference point of the high pressure pump and a top dead center of the engine based on the comparison result. The electronic control unit is
In a state where the top dead center of the high pressure pump and the top dead center of the engine are matched, the amount of change in rail pressure per unit time is determined based on the change characteristic of rail pressure with respect to the elapsed time acquired at the time of engine start. While the reference rail pressure inclination characteristic calculated corresponding to the rotation angle of the rotation shaft of the pump is stored in advance,
By detecting the deviation between the top dead center of the plunger as the reference point of the high-pressure pump and the top dead center of the engine by comparing the actual rail pressure inclination characteristic and the reference rail pressure inclination characteristic, a predetermined inflection point is used. 5. The common rail fuel injection control device according to claim 4, wherein the common rail type fuel injection control device is configured to compare the positions in the respective rail pressure gradient characteristics and obtain a positional deviation thereof. The electronic control unit is
A fuel injection amount correction coefficient for the detected positional deviation is calculated using a predetermined injection amount correction coefficient conversion table, and fuel injection with the corrected fuel injection amount is enabled. The common rail fuel injection control device according to claim 5.

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