JP2005171895A - Common-rail type fuel injection device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce fluctuation of common rail pressure in a common rail type fuel injection device. <P>SOLUTION: Based on knowledge that common rail pressure fluctuates strongly when rotation cycle of a pump 13 pumping fuel to a common rail 14 is close to integral multiple of a drive cycle of pulse width modulation drive of a solenoid valve adjusting fuel flow rate to the pump 13, a pump control means 15 has a structure capable of switching current command value feed back operation of current supplied to the solenoid valve between when rotation cycle of the pump 13 detected by an engine rotation speed sensor 17 is in a predetermined range established in vicinity of integral multiple of the drive cycle of the pulse width modulation drive and when the rotation cycle is in other range. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a common rail fuel injection device for an internal combustion engine.

2. Description of the Related Art Today, common rail fuel injection devices that can freely implement a complicated aspect of fuel injection are widely used in internal combustion engines. The common rail type fuel injection device is configured to store the pressurized fuel supplied to the injector in the common rail common to the injectors of each cylinder, and is substantially equal to the fuel pressure in the common rail by opening and closing the injector. Fuel is injected at the injection pressure. Fuel is pumped to the common rail from a pump that is operated by engine rotational power. The pump adjusts the flow rate of the low-pressure fuel used for pumping by, for example, a solenoid valve that is fed by PWM (Pulse Width Modulation) drive and can adjust the opening according to the current value. The current to be supplied is feedback-controlled by the pump control means so that the actual pressure in the common rail becomes the target pressure (Patent Document 1, etc.).
JP 2001-3791 A

By the way, the output performance of the internal combustion engine and the cleanliness of the exhaust gas depend on the characteristics of the fuel spray such as the degree of atomization of the fuel spray injected from the injector and the spray penetration force. It is largely defined by the injection pressure, and hence the pressure in the common rail. Therefore, it is indispensable to control the pressure in the common rail with high accuracy, and further improvement is required.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a common rail fuel injection device capable of further increasing the accuracy of common rail pressure control.

In the first aspect of the invention, an injector that injects fuel into the cylinder, a common rail that stores pressurized fuel to be supplied to the injector, and a flow rate of low-pressure fuel that is pumped to the common rail by engine rotational power and used for pumping Is adjusted by a solenoid valve that is fed by PWM drive and can be adjusted according to the current value, and the current supplied to the solenoid valve is controlled by feedback control so that the actual pressure in the common rail becomes the target pressure. In a common rail fuel injection device for an internal combustion engine having a pump control means for adjusting,
A rotation period detecting means for detecting the rotation period of the pump;
The pump control means is configured to supply current to the solenoid valve when the rotation period of the pump is within a predetermined range set in the vicinity of an integral multiple of the drive period of the PWM drive and at other times. The feedback calculation of the command value can be switched freely.

  According to the experimental research by the inventors, in the configuration in which current supply to the solenoid valve is performed by PWM driving, the pressure in the common rail is pulsated with a relatively long period compared to the driving period of the PWM driving (hereinafter referred to as the PWM driving period). It was found that pressure swell occurred as appropriate. Further, the pressure undulation appears most prominently when the pump rotation cycle is in the vicinity of an integral multiple of the PWM drive drive cycle, and becomes less noticeable as the pump rotation cycle moves away from a cycle that is an integral multiple of the PWM drive drive cycle. When the rotation cycle of the pump is within a predetermined range set in the vicinity of an integral multiple of the drive cycle of the PWM drive and at other times, feedback calculation of the current command value of the current supplied to the solenoid valve is performed. By making it switchable, it is possible to effectively eliminate pressure undulations.

  According to a second aspect of the present invention, in the configuration of the first aspect of the invention, the pump control means calculates the current command value as a control amount by inputting a pressure deviation between an actual pressure in the common rail and a target pressure. And a correction value calculation means for calculating a correction value to be added to the control amount calculation means when the rotation period of the pump is within the predetermined range.

  When the pump rotation cycle is within a predetermined range set in the vicinity of an integral multiple of the PWM drive cycle, the current command value is corrected, thereby causing pressure undulation. Can be suppressed. Since the control amount calculation means for calculating the basic current command value may be the same as that of the conventional apparatus, it is easy to implement.

  According to a third aspect of the present invention, in the configuration of the first aspect of the invention, the pump control means receives the pressure deviation between the actual pressure in the common rail and the target pressure as an input, and the control amount includes at least a proportional term. Control amount calculation means for calculating a current command value is provided, and the control amount calculation means includes proportional gain correction means for correcting the gain of the proportional term when the rotation period of the pump is within the predetermined range. Prepare.

  When the pump rotation cycle is within a predetermined range set in the vicinity of an integral multiple of the PWM drive cycle, the pressure of the proportional term is corrected. Swelling can be suppressed. Since the control amount calculation means for calculating the basic current command value may be the same as that of the conventional apparatus, it is easy to implement.

  FIG. 1 shows a configuration of a diesel engine (hereinafter, simply referred to as an engine as appropriate) to which a fuel control device for an internal combustion engine of the present invention is applied. This embodiment is applied to an automobile, for example. The illustrated engine is a four-cylinder engine, and each cylinder of the engine body 1 is provided with an injector 11 corresponding to one-to-one, and fuel is injected when the valve is opened. Fuel is supplied from a common rail 14 common to each cylinder. Fuel in the fuel tank 12 is supplied to the common rail 14 from a high-pressure pump 13 that is a pump. The high-pressure pump 13 supplies fuel to the common rail 14 by pressure, and the common rail 14 is held at a high pressure. The structure of the high pressure pump 13 will be described later. The fuel pressure in the common rail 14 (hereinafter referred to as “common rail pressure” as appropriate) regulates the injection pressure of the injector 11 and is adjusted by the ECU 15 serving as pump control means controlling the high-pressure pump 13.

  The ECU 15 controls each part of the engine such as the injector 11 and the high pressure pump 13. In order to control each part of the engine, the ECU 15 receives output signals of sensors provided in each part of the engine to detect the operating state of the engine. A pressure sensor 16 for detecting the common rail pressure is attached to the common rail 14. Further, a rotation speed sensor 17 serving as a rotation period detecting means for detecting rotation of the crankshaft that outputs engine power is provided, and the ECU 15 is made aware of the rotation speed of the crankshaft (engine rotation speed). . Although not shown in the drawings, it is a matter of course that general sensors are provided as a diesel engine.

  ECU15 consists of various signal processing circuits and arithmetic circuits, for example, is comprised centering on a microcomputer.

  Next, control of the high-pressure pump 13 in the ECU 15 that is a characteristic part of the present invention will be described. The high pressure pump 13 is controlled by the ECU 15 as described above, and the ECU 15 controls the high pressure pump 13 so that the actual pressure becomes the target pressure based on the actual pressure of the common rail pressure known from the pressure sensor 16 and the target pressure. As the target pressure, an appropriate pressure value corresponding to the operating state such as the throttle valve opening and the engine speed is set as needed.

  The high-pressure pump 13 has a known structure that is employed in a common rail fuel injection device, and this is shown in FIG. The high-pressure pump 13 is provided with a pump rotating shaft 21 that receives engine power. A feed pump 132 that sucks fuel from the fuel tank 12 by engine power (engine rotating power) transmitted to the pump rotating shaft 21 at a predetermined reduction ratio, and A fuel pump 134 for pumping fuel to the common rail 14 is activated. A ring cam 41 is disposed on the pump rotating shaft 21 in the fuel pumping portion 134, and a cylinder 401 is formed on the outer periphery of the cam 41 in the radial direction of the pump rotating shaft 21. A plurality of cylinders 401 are arranged at equal intervals in the circumferential direction of the pump rotating shaft 21, and plungers 42 are slidably held in the respective cylinders 401. The pump rotating shaft 21 has a cam crest eccentric from its central axis, and presses the plunger 42 via the ring cam 41 when the cam crest rises.

A space formed by the plunger 42 and the cylinder 401 on the opposite side of the ring cam 41 across the plunger 42 is a pressure chamber 402 that expands and contracts due to the displacement of the plunger 42. The pressure chamber 402 is supplied with pre-pressurized fuel that passes through a suction valve 135 constituted by a check valve whose forward direction is the flow direction into the pressure chamber 402, and the plunger 42 as the cam crest rises. Compresses the fuel, and the pressurized fuel is supplied to the common rail 14 via a discharge valve 136 constituted by a check valve whose forward direction is the outflow direction from the pressure chamber 402.

  The fuel from the fuel tank 12 is supplied to the pressure chamber 40 by the feed pump 132 through the pressure regulating valve 131, and the fuel metering valve (hereinafter referred to as SCV as appropriate) is fed from the feed pump 132. ) 133 and the intake valve 135.

  The SCV 133 is an electromagnetic valve that adjusts the fuel flow rate by changing the opening degree (hereinafter referred to as the “SCV opening degree” as appropriate) according to the displacement amount of the valve body 32 inserted in the vertical hole of the rod-shaped valve body 31. The fuel supply amount to the pressure chamber 402 increases and the discharge amount increases as the opening side increases, and this increases the common rail pressure. The fuel from the SCV 133 is sucked into the pressure chamber 402 during a period when the cam mountain descends.

  The displacement of the valve body 32 is made by electromagnetic drive by the solenoid 33, and the displacement amount is made by adjusting the current amount to the solenoid 33. The current drive method for the solenoid 33 is a general PWM (Pulse Width Modulation) drive. For example, a method of controlling the ON / OFF time of the duty ratio according to the current command value by software can be adopted. Thereby, a current flows through the solenoid 33 of the SCV 133 with a duty ratio corresponding to the current command value. Note that the drive cycle of current drive for the solenoid 33 (hereinafter, referred to as the “SCV drive cycle” as appropriate) is stored in the ECU 15 in advance.

  FIG. 3 is an example of a characteristic line showing the relationship between the average current of the drive current (hereinafter referred to as “SCV drive current” as appropriate) flowing through the solenoid 33 of the SCV 133 and the discharge amount of the high-pressure pump 13. In the example of the figure, the larger the average current is, the smaller the opening becomes, and the SCV opening becomes 0 and the discharge amount becomes 0 at a predetermined current value. The smaller the average current, the larger the SCV opening and the discharge amount. In the current region where the discharge amount gradually increases with respect to the average current, the discharge amount is substantially proportional to the SCV opening and the length of the period in which the cam crest of the pump rotating shaft 21 descends and the pressure chamber 402 is in the expansion direction. The reason why the discharge amount takes a constant value in the low current region is that the discharge amount is defined by the stroke of the plunger 42 in the low current region where the SCV opening is large. At this time, since the length of the period in which the pressure chamber 402 is in the expansion direction becomes longer as the engine speed is lower, the slope of the characteristic line becomes steep, and the upper limit of the current region where the discharge amount takes a constant value is the high current region. Extend to the side. The ECU 15 calculates a current command value as a control amount for adjusting the common rail pressure to be controlled with respect to the required discharge amount. In calculating the current command value, the engine speed having dependency on the discharge amount as described above is taken into consideration.

  FIG. 4 shows the control of the high-pressure pump 13 executed by the ECU 15 as functional blocks. A PID calculation unit 151 is provided with a pressure deviation between the target pressure of the common rail pressure and the actual pressure as input, and PID calculation for adding a proportional term, an integral term, and a differential term is executed. In the calculation, a current command value is obtained. In addition, a correction value calculation unit 152 is provided with the pressure deviation as an input, and the calculation output of the PID calculation unit 151 is added and corrected by the calculation output. The correction value to be added and corrected is obtained by multiplying the pressure deviation by a predetermined coefficient. The coefficient is set based on the engine speed, the fuel injection amount, the common rail pressure, and the like.

  In the correction value calculation unit 152, the engine speed is converted into a rotation period (hereinafter referred to as a pump rotation period) Tp of the pump rotating shaft 21, and the pump rotation period Tp is an integral multiple (Ts × n) of the SCV drive period Ts. The correction value is set to 0 outside the predetermined range set in the vicinity of the period, and the calculation output of the PID calculation unit 151 is not substantially corrected. The coefficient may be determined in advance by storing a map that receives a detection value of an operating state such as the engine speed as an input, and referring to the map.

  The operation of the common rail fuel injection device will be described. FIG. 5 shows the opening area of the SCV 133 (hereinafter referred to as “SCV opening area” as appropriate) and the discharge amount in time series. The opening area is a passage cross-sectional area that defines a fuel flow rate that varies according to the amount of displacement of the valve body 32 in the SCV 133. The discharge amount is expressed as a discharge amount per pump rotation period Tp. This is substantially proportional to the integral value of the SCV opening area in the period of the length of the pump rotation period Tp. Two cases with different pump rotation periods Tp are shown as discharge amounts. The first case is a pump rotation cycle Tp (A), and the pump rotation cycle Tp (A) takes a value in the vicinity of an integral multiple (Ts × n) of the SCV drive cycle Ts. In the illustrated example, the pump rotation period Tp is set to about 1.125 times the SCV drive period Ts. The second of the two cases having different pump rotation cycles Tp is the case of the pump rotation cycle Tp (B), and the pump rotation cycle Tp (B) takes a value that is separated from the vicinity of the SCV drive cycle Ts. In the illustrated example, the pump rotation cycle Tp is set to about 0.5 times the SCV drive cycle Ts.

  Since the SCV 133 controls the current by PWM driving, the SCV opening area varies in the same cycle as the SCV driving cycle Ts as shown in the figure. When the pump rotation cycle is in the vicinity of an integral multiple of the SCV drive cycle, the discharge rate per pump rotation gradually increases and decreases. This causes a swell of the discharge amount, which causes a swell in the common rail pressure. Further, the rate of change of the discharge amount per pump rotation increases as it moves away from the vicinity of an integral multiple of the SCV drive cycle, and the pulsation of the discharge amount becomes a short-cycle pulsation, and the common rail pressure does not swell. In the example of the pump rotation cycle Tp (A) in which the pump rotation cycle Tp is a value in the vicinity of the SCV drive cycle Ts, the discharge amount is swelled. On the other hand, in the example of the pump rotation cycle (B) in which the pump rotation cycle Tp is (Ts × 1/2), only pulsation with the same cycle as the SCV drive cycle Ts occurs. In this case, the pulsation of the discharge amount is a short-period oscillating vibration, and the undulation phenomenon does not appear in the discharge amount and the common rail pressure.

  Therefore, in this common rail fuel injection device, the current command value of the SCV 133 as the control amount is corrected when the pump rotation cycle Tp takes a value in the vicinity of an integral multiple (Ts × n) of the SCV drive cycle. As shown in FIG. 6, the swell of the common rail pressure can be effectively reduced.

  As described above, as the pump rotation cycle Tp is closer to an integral multiple (Ts × n) of the SCV drive cycle, the pressure undulation cycle becomes longer. Therefore, substantial correction is performed on the calculation output of the PID calculation unit 151. The predetermined range of the pump rotation cycle Tp to be performed is set to a range in which the pump rotation cycle Tp is in the vicinity of an integer multiple (Ts × n) of the SCV drive cycle. The range is defined as (Ts × n). The limit value on the near side and the limit value on the side far from (Ts × n) are set according to the required pressure swell suppression action.

  In addition, as described above, the coefficient map includes the fuel injection amount and the common rail pressure as the operating state as a parameter. This is the discharge amount required to maintain the target pressure depending on the fuel injection amount. This is also because the discharge pressure changes depending on the common rail pressure, which is the pressure on the outlet side of the discharge valve 136, and the height of the swell of the common rail pressure changes depending on the operating state.

(Second Embodiment)
FIG. 7 is a functional block diagram showing the control of the high pressure pump in the ECU of the common rail fuel injection control apparatus according to the second embodiment of the present invention. In the first embodiment, the current command value is calculated by another method. Portions that operate substantially the same as in the first embodiment will be assigned the same reference numerals, and differences from the first embodiment will be mainly described.

  A PID calculation unit 151A, which is a control amount calculation means that receives a pressure deviation as an input, has a proportional term calculation unit 1511, an integral term calculation unit 1512, and a differential term calculation unit 1513. As a result, the current command value of the SCV 133 is obtained. The proportional term computing unit 1511, the integral term computing unit 1512, and the derivative term computing unit 1513 are general ones. The proportional term computing unit 1511 multiplies the pressure deviation by a proportional gain, and the integral term computing unit 1512 is an integral value of the pressure deviation. Is multiplied by the integral gain, and the differential term calculation unit 1513 multiplies the differential value of the pressure deviation by the differential gain.

  The PID calculation unit 151A is also provided with a gain correction unit 1514 that is a proportional gain correction unit that corrects the proportional gain, and the proportional gain used in the proportional term calculation unit 1511 is updated by the correction. The predetermined range of the pump rotation cycle Tp for performing substantial correction on the proportional gain is set to a range in the vicinity of the pump rotation cycle Tp being an integral multiple of the SCV drive cycle (Ts × n). Further, the correction of the proportional gain is performed with reference to a map that receives the engine speed, the injection amount, the common rail pressure, and the like as in the first embodiment.

  This embodiment can also effectively reduce the phenomenon of common rail pressure swell.

  Moreover, in each said embodiment, since the PID calculating part 151, the proportional term calculating part 1511, the integral term calculating part 1512, and the derivative term calculating part 1513 may be the same as the thing of the conventional apparatus, implementation is easy.

It is a block diagram of an internal combustion engine provided with the common rail type fuel injection device of the present invention. It is sectional drawing of the high pressure pump which comprises the said common rail type fuel injection apparatus. It is a characteristic view of the high pressure pump. FIG. 2 is a block diagram showing a first control content of the present invention that is executed by an ECU constituting the common rail fuel injection device. It is a timing chart explaining the action | operation of the said high pressure pump. It is a timing chart which compares the said common rail type fuel injection device and the conventional common rail type fuel injection device. It is a block diagram which shows the 2nd control content of this invention performed by ECU which comprises the said common rail type fuel injection apparatus.

Explanation of symbols

11 Injector 12 Fuel tank 13 High-pressure pump (pump)
132 Feed pump 133 SCV (solenoid valve)
134 Fuel Pumping Unit 136 Discharge Valve 14 Common Rail 15 ECU (Pump Control Unit)
151,151A PID calculation unit (control amount calculation means)
152 Correction calculation unit (correction amount calculation means)
1511 Proportional term calculation unit 1512 Integral term calculation unit 1513 Differential term calculation unit 1514 Proportional gain correction unit (proportional gain correction means)
17 Engine speed sensor (rotation cycle detection means)

Claims (3)

An injector for injecting fuel into the cylinder, a common rail for storing pressurized fuel to be supplied to the injector, and pumping the fuel to the common rail by engine rotational power, and adjusting the flow rate of the low-pressure fuel used for this pumping by PWM drive A pump that is powered by a solenoid valve that can be adjusted according to the current value, and a pump control means that adjusts the current supplied to the solenoid valve by feedback control so that the actual pressure in the common rail becomes a target pressure. In a common rail fuel injection device for an internal combustion engine having
A rotation period detecting means for detecting the rotation period of the pump;
The pump control means is configured to supply current to the solenoid valve when the rotation period of the pump is within a predetermined range set in the vicinity of an integral multiple of the drive period of the PWM drive and at other times. A common rail fuel injection device for an internal combustion engine, wherein feedback calculation of a command value is freely switchable.   2. The common rail fuel injection device for an internal combustion engine according to claim 1, wherein the pump control means calculates the current command value as a control amount by inputting a pressure deviation between an actual pressure in the common rail and a target pressure. A common rail fuel injection apparatus for an internal combustion engine, comprising: a quantity calculation means; and a correction value calculation means for calculating a correction value to be added to the control quantity calculation means when the rotation period of the pump is within the predetermined range. .   2. The common rail fuel injection apparatus for an internal combustion engine according to claim 1, wherein the pump control means receives the pressure deviation between the actual pressure in the common rail and the target pressure as an input, and the current command as a control amount including at least a proportional term. Control amount calculation means for calculating a value is provided, and the control amount calculation means includes proportional gain correction means for correcting the gain of the proportional term when the rotation period of the pump is within the predetermined range. Common rail fuel injection device for internal combustion engines.

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