JP2010525228A - INJECTION CONTROL METHOD FOR INTERNAL COMBUSTION ENGINE AND INJECTION CONTROL DEVICE FOR INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

  The present invention relates to an injection control method in an internal combustion engine and an injection control apparatus in an internal combustion engine for accurately adjusting an injection amount in a fuel injection system without additional hardware. According to the present invention, the pressure value is supplied to the control device (260) together with the time delay amount of the pressure sensor (205), and the pressure value is corrected by evaluating these values.

Description

Prior Art For example, based on the increasing demands on emission regulations for obstructions in Europe and the United States, it is becoming increasingly important to obtain highly accurate fuel injection in common rail fuel injection systems. In addition, the demand for the maximum rail pressure of the future CR system is increasing.

  In order to meet the demand for high rail pressure, leakage loss must be reduced. This is achieved in particular by shortening the pumping phase. However, if the pumping phase is shortened, the pumping amount increases in the high rotation speed region, the pressure gradient on the rail becomes excessively steep, and it becomes difficult to accurately meter the desired injection amount.

  In order to accurately adjust the amount of fuel to be injected to the injector as accurately as possible, the fuel pressure in the rail is measured by a pressure sensor immediately before the injector is driven, and a characteristic map (so-called flow rate-drive time characteristic map) is obtained from the pressure value. ) To determine the drive time.

  However, the low-pass filter necessary for noise reduction in the pressure sensor and the control device causes a time delay in the true rail pressure signal in the control device. Also, the reading of the pressure value immediately before the original metering from the injector may be performed during a dynamic interrupt to ensure sufficient time for the controller to calculate the required drive time. is there. As a whole, a time delay amount Δt from the pressure measurement until the pressure value becomes available in the control device is generated, and this time delay amount is used when calculating the drive time of the injector.

  At a large number of operating points in the high rotation speed region where the gradient of the rail pressure is steep, the time delay amount Δt described above causes the measured value of the rail pressure used in the controller to be between the actual value of the rail pressure at the time of injection. There is a difference of about 80 bar. Since the amount of injected fuel is determined mainly by the rail pressure, such a pressure difference leads to a significant injection amount error.

  A method for determining the pressure value at the start of injection by linear interpolation is known from DE 19858571. However, this method can only be used when the pressure gradient is very steep and strong fluctuations are observed.

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a method capable of accurately adjusting an injection amount at low cost.

The subject is a method for driving a fuel injection system for an internal combustion engine comprising a high-pressure pump, a common rail, a pressure sensor, at least one injection valve, and a control device for driving and controlling the injection valve. In a method for driving a fuel injection system for an internal combustion engine, which detects and evaluates a _first rail pressure p _Rail-1 of a common rail at a _first time point t ₁ (j) existing at a time ΔT before injection of a valve, A second rail pressure p _Rail-2 ( _jr ) of the common rail is detected at a _second time t ₂ (j) after the first time with respect to the injection jr that precedes in time; This is solved by correcting the _first rail pressure _pRail-1 detected at the first time point with respect to the injection j based on the detected second rail pressure _pRail-2 (jr). The

1 is a schematic view of a common rail fuel injection system. It is a graph showing the pressure characteristic in the one work cycle in the 4-cylinder internal combustion engine which performs two pumping strokes per work cycle.

The method of the present invention, due to the time delay from the first rail pressure _{p Rail-1} detection in the first time point _{t 1} to the second detection of the rail pressure _{p Rail-2} at the second time point _{t 2} The fact that the error has a certain regularity is used. Such an error, that is, a systematic error, is known relatively accurately from the previous injection j-r, and is used to correct the first rail pressure _pRail-1 of the next injection j. As a result, the rail pressure error is remarkably reduced, and the amount of injected fuel can be adjusted accurately. Moreover, no additional hardware is required.

  A further advantage of the method of the present invention is that the existing pressure sensor requires only one additional pressure measurement and no other hardware is required. That is, the method of the present invention can be realized by updating an existing fuel injection system in software.

In an advantageous embodiment of the method according to the invention, the first rail pressure at injection j is determined using the first rail pressure p _Rail-1 (jr) at time j. It is corrected. As a result, the accuracy of correcting the rail pressure, and hence the accuracy of metering of the injected fuel amount, is improved.

In an advantageous embodiment of the method according to the invention, the correction of the _first rail pressure _pRail-1 is performed according to the formula as defined in claim 3.

  In order to explain the formula, each concept will be explained.

  In a four-cycle internal combustion engine, one work cycle corresponds to two crankshaft rotations, that is, a crankshaft angle of 720 °. In this one work cycle, each of the m cylinders performs four strokes (intake stroke, compression stroke, work process, exhaust stroke) of the 4-cycle internal combustion engine. Since the four strokes are repeated in the next work cycle, the internal combustion engine is periodically operated every work cycle. The index j is the number of m cylinders.

  In the present invention, the injection j means that fuel is injected into the cylinder j. Fuel is injected once into all the m cylinders in one work cycle. Since the method of the present invention is applicable to any of main injection, pre-injection and post-injection, these injection types are not distinguished.

  Since the high-pressure pump is rigidly coupled to the crankshaft of the internal combustion engine, the pumping stroke of the high-pressure pump follows the predetermined periodicity of the internal combustion engine described above, and preferably operates at an integer multiple of the work cycle. The number of pumpings in one work cycle is determined according to the number of pump elements of the high-pressure pump and the conversion ratio from the high-pressure pump to the crankshaft. In general, the number of pumps per work cycle is an integer. Therefore, for example, in a four-cylinder internal combustion engine, pumping is performed twice from a high pressure pump in one work cycle.

That is, for example, in a four-cylinder internal combustion engine, four injections and two pumps from the high-pressure pump are performed in one work cycle, so that the pumps from the high-pressure pump are performed every other injection. This means that a very similar rail pressure characteristic becomes dominant in the two injections j-2 before the actual injection j. In the present invention, the actual injection pressure _pRail-1 of the next injection j is corrected using the effect. According to the method of the present invention, it is possible to remarkably reduce the injection error caused by the pressure value error.

  In the above-described embodiment, the delay amount from the preceding injection to the actual injection j is 2. This delay amount is hereinafter referred to as r.

  In relation to the equation recited in claim 3, the delay amount in the above-described embodiment of the four-cylinder internal combustion engine is r = 2.

It should be noted here that the preceding cylinder in the ignition sequence cannot be taken into account unless it is an in-line cylinder system having pumping synchronized with injection and sufficient pump uniform pumping characteristics. When the conversion ratio is not synchronized with the injection and / or when a V-type cylinder system is used, the rail pressure characteristics near the time of injection have a difference depending on the individual cylinders. This is based on the system and is related to the ignition sequence of the preceding cylinder or cylinders depending on the delay amount r. With the first rail pressure _pRail-1 (jr) and the second rail pressure _pRail-2 ( _jr ), which are known during the injection jr in the cylinder jr, The first rail pressure p _Rail-1 (j) can be replaced and corrected. The following table shows the current internal combustion engine concept and the delay amount r with respect to the conversion ratio from the internal combustion engine to the high pressure pump.

  In another advantageous embodiment of the invention, the second rail pressure of cylinder jr and / or the measured value of the first rail pressure is used to correct the first rail pressure at injection j, where Similar pressure characteristics are dominant in the cylinders jr, j immediately before and / or during the injection.

  The problems of the present invention can also be solved by configuring a control device that operates according to the method of the present invention.

  Other embodiments and other advantages of the invention can be obtained from the description, the claims, and the drawings. All features shown in the description, claims and figures may be the subject of the present invention, either alone or in any combination.

FIG. 1 shows a schematic view of a fuel injection device for an internal combustion engine, and the method of the present invention will be described in detail with reference thereto.

  Fuel is metered into the individual combustion chambers of the internal combustion engine (not shown) via the injector. Each injector corresponds to a respective cylinder of an internal combustion engine (not shown). In the embodiment of FIG. 1, four cylinders 100-1 to 100-4 of a four-cylinder internal combustion engine are shown. If the number of cylinders of the internal combustion engine is m, which is different from this, the number of injectors will be correspondingly 100-1 to 100-m.

  Each injector is supplied with fuel from a pressure accumulator or common rail 200. The common rail 200 is connected to a high-pressure pump 220 via a high-pressure line 210. The high pressure pump 220 is connected to the low pressure pump 250 via a low pressure line 240. The low pressure pump 250 is most often configured as an electric fuel pump. The low pressure pump 250 is preferably arranged in the fuel tank 255.

  A pressure sensor 205 is disposed on the common rail 200. A fuel amount control valve 230 is arranged between the low pressure pump 250 and the high pressure pump 220. Alternatively, although not shown, the fuel amount control valve 230 may be disposed between the high-pressure pump 220 and the common rail 200. A predetermined voltage is applied from the output stage 160 to the fuel amount control valve 230 and the injector 100. The output stage 160 is preferably incorporated within the controller 260 and processes the output signals of the pressure sensor 205 and various other sensors 270.

  The fuel injection device operates as follows. That is, first, the low-pressure pump 250 pumps the fuel in the fuel tank 255 to the high-pressure pump 220 via the low-pressure line 240. Next, the high pressure pump 220 compresses the fuel and pumps it to the common rail 200 via the high pressure pipe 210. Further, the start and end of the fuel injection j to the j-th cylinder are controlled by driving the injector 100-j. The control is performed based on the operation characteristic amount of the internal combustion engine detected by various sensors 270.

The pressure sensor 205 measures the fuel pressure p _rail (t) in the common rail 200 and is preferably evaluated in the controller 260.

The fuel amount control valve 230 is driven such that the target pressure value p _soll is generated in the common rail 200 in accordance with the measured pressure value p _rail . The fuel amount control valve 230 controls the amount of fuel pumped from the high-pressure pump 220 and thus the pressure drop amount in the common rail 200. For this purpose, it is necessary that the fuel amount control valve 230 is driven at a predetermined first time and returned to the original at a predetermined second time. In order to achieve accurate pressure control, the fuel quantity control valve 230 must be opened and closed at precisely defined times. At this time, it is advantageous that the delay time from the driving of the fuel amount control valve 230 to the actual response, that is, the opening or closing of the fuel amount control valve 230 is as small as possible.

When the demand type pressure control is performed, the high pressure pump 220 pumps the fuel amount necessary for maintaining the fuel pressure p _rail (t) in the common rail 200 or the fuel amount necessary for a desired pressure change.

FIG. 2 shows a graph of rail pressure characteristics over a work cycle corresponding to a crankshaft angle of 720 °. The rail pressure p _rail (t) indicated by the first curve 280 follows a periodic pattern. Two pumping operations are performed within one work cycle corresponding to a crankshaft angle of 0 ° to 720 °. This pumping is identified by the maximum rail pressure at crankshaft angles of 180 ° and 540 °.

  The two pumping operations are performed immediately before the injection of the cylinders 2 and 4 of the internal combustion engine. The injections j of the four cylinders of the internal combustion engine are represented by cylinder numbers 1, 2, 3, and 4. During the injections j = 1 and j = 3 of the cylinders 1 and 3, the high-pressure pump is not pumped.

Since fuel is the amount of fuel present in the common rail 200 when it is injected into the combustion chamber decreases, the fuel pressure p _rail in the common rail of between injection 1 and 3 is reduced. This is also clear from the first curve 280.

As described above, since a certain amount of time delay is unavoidable between the detection of the rail pressure and the injection, the control device, for example, injects j = 1 of the first cylinder at a crankshaft angle of 0 °. And the first rail pressure p _rail-1 (j = 1) at time t ₁ (j = 1) must be determined based on this. Since the fuel is not pumped by the high-pressure pump from the injection j = 1 of the first cylinder at the crankshaft angle of 0 ° to the time point t ₁ (j = 1), the rail pressure within the time range ΔT is It is almost constant.

The rail pressure characteristic at the injection j = 2 to the second cylinder is different from this. The time range ΔT is also considered in this case, but in the injection concerned, in the time range ΔT from the time point t ₁ (j = 2) to the injection at the crankshaft angle of 180 ° due to the pumping by the high-pressure pump 220. The rail pressure p _rail changes significantly. In the conventional method, in order to control the injection amount, the injection duration is obtained using only the first rail pressure at the time point t ₁ (j = 2) when the second injection j = 2, and the second injection is performed. Since the fuel pressure in the common rail 200 at the start of j = 2 was considerably higher than the fuel obtained based on the drive duration, the actual injection amount was larger than the desired injection amount. According to FIG. 2, the pressure difference between the second rail pressure p _rail-2 and the first rail pressure p _{rail-1 at} the second injection j = 2 is about 80 bar.

According to the present invention, the rail pressure is detected at the second time point t ₂ (j) before the injection j. The second time point t ₂ (j) is a time point just before the start of injection or at the same time as the injection. In this case, the pressure difference between the second rail pressure p _rail-2 and the first rail pressure p _rail-1 is about 80 bar. The error or systematic error is repeated approximately the same for every fourth injection j = 4 corresponding to a crankshaft angle of 540 ° as shown in FIG.

In the method of the present invention, such periodicity is utilized, and the first rail pressure p _rail-1 (j = 4) measured at time t ₁ (j = 4) before the fourth injection j = 4 is The pressure difference p _rail−2 (j = 2) −p _rail−1 (j = 2) obtained for the second injection j = 2 is corrected. In this way, the injection amount error caused by the pressure value error can be remarkably reduced.

Claims (8)

A high pressure pump (220), a common rail (200), a pressure sensor (205), at least one injection valve (100-j [j = 1 to m]), and a control device (160) for driving and controlling the injection valve. A driving method for a fuel injection system of an internal combustion engine,
For the injection j, the first rail pressure (p _Rail-1 (j) of the common rail at the first time point (t ₁ (j)) existing at the time ΔT before the injection of the injection valve (100-j). )) Detected and evaluated,
In a driving method for a fuel injection system of an internal combustion engine,
The second rail pressure (p _Rail-2 ) of the common rail is detected at a _second time point (t ₂ (j)) after the first time point with respect to the injection jr that precedes in time. The first rail pressure (p _Rail-1 (j) detected at the first time point for the injection j based on the second rail pressure (p _Rail-2 (jr)). )) Is corrected, a driving method of a fuel injection system for an internal combustion engine. Using the first rail pressure (p _Rail-1 (t ₁ (jr))) for the injection jr that precedes in time, the detected at the first time for the injection j The method for driving a fuel injection system for an internal combustion engine according to claim 1, wherein the first rail pressure (p _Rail-1 (j)) is corrected. The correction of the first rail pressure is _expressed by the equation p _{Rail-1, korr} (t ₁ (j)) = p _Rail-1 (t ₁ (j)) + [p _Rail-2 (t ₂ ( _jr )) ) -P _Rail-1 (t ₁ (jr))]
Where p _{Rail-1, korr} (t ₁ (j)) is the correction value for the first rail pressure at injection j, and p _Rail-1 (t ₁ (j)) is at injection j P _Rail-2 (t ₂ (jr)) is a second rail pressure measurement at injection jr that precedes injection j in time. , P _Rail-1 (t ₁ (jr)) is a measurement value of the first rail pressure at the injection jr that precedes the injection j in time, and j is an index of the injection, and is an internal combustion engine. 3. The method for driving a fuel injection system for an internal combustion engine according to claim 1, wherein j = 1 to m corresponding to the number m of cylinders, r is a delay amount, and r ≦ j.   The fuel injection system for an internal combustion engine according to any one of claims 1 to 3, wherein the time (ΔT) is equal to or greater than a time delay amount from when a signal is detected and an injection duration is obtained until the start of injection. Driving method.   The method for driving a fuel injection system for an internal combustion engine according to any one of claims 1 to 4, wherein the time (ΔT) is equal to or greater than a time from an interrupt to an injection start. The measured value of the second rail pressure in the predetermined cylinder jr (p _Rail-2 (t ₂ (jr))) and / or the first rail pressure in the predetermined cylinder (jr) The measured value (p _Rail-1 (t ₁ (jr))) is used to correct the first rail pressure for the injection j, where the cylinder jr and the cylinder j immediately before the injection and 6. A method for driving a fuel injection system of an internal combustion engine according to claim 1, wherein a similar pressure characteristic is dominant during the injection.   A computer program for causing a computer to execute all the steps of the method for driving a fuel injection system for an internal combustion engine according to any one of claims 1 to 6.   A control device for an internal combustion engine, which executes all the steps of the method for driving a fuel injection system for an internal combustion engine according to any one of claims 1 to 6.

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