JP2014190186A - Fuel supply control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel supply control device that enables enhancement of correction accuracy of port injection amount by considering a pressure wave from a fuel pressure pump and a pressure pulsation component caused by reflection of the pressure wave.SOLUTION: A fuel supply control device is mounted to an internal combustion engine including: a low pressure fuel injection mechanism having low pressure fuel piping and a low pressure fuel injection valve for injecting fuel from the low pressure fuel piping; and a high pressure fuel injection mechanism that has a fuel pressure pump for sucking and pressurizing fuel from the low pressure fuel piping, high pressure fuel piping supplied with the pressurized fuel and a high pressure fuel injection valve for injecting the fuel from the high pressure fuel piping. The fuel supply control device controls fuel injection amounts at least by the low pressure fuel injection valve and the high pressure fuel injection valve. The fuel supply control device estimates delivery fuel pressure Pd on the basis of a first pressure fluctuation component Pc1 that is transmitted from the fuel pressure pump to inside of the low pressure fuel piping and transferred to the low pressure fuel injection valve side and a second pressure fluctuation component Pc2 that is reflected within the low pressure fuel piping, then reciprocated within the piping and transmitted again to the low pressure fuel injection valve side, and controls the fuel injection amount by the low pressure fuel injection valve.

Description

  The present invention relates to a fuel supply control device, and more particularly to a fuel supply control device equipped in a fuel supply system of an internal combustion engine including a fuel pressurization pump that is mechanically driven by power of the internal combustion engine.

  In a fuel supply system for an in-cylinder injection type or dual injection type internal combustion engine capable of directly injecting high-pressure fuel into a cylinder, generally, fuel supplied from a low-pressure fuel pump is pressurized by a fuel pressurizing pump, A mechanically driven fuel pressurizing pump in which a fuel pressurizing plunger is reciprocated by a cam is widely used.

  Then, as a fuel supply control device for controlling fuel supply in such a fuel supply system, for example, the port fuel injection time is corrected for pressure pulsation caused by the reciprocation of the plunger at the time of engine start where port injection is performed exclusively. In addition, one that stabilizes the port injection amount without increasing the size of the pulsation damper is known (for example, see Patent Document 1). Further, the fuel pressure is switched by switching the length of the fuel pipe depending on whether the fuel pressure is increased by the fuel pressurizing pump (see, for example, Patent Document 2), or the fuel pressure in the high-pressure fuel passage is near the relief pressure. A known fuel injection timing is set to a timing at which the fuel pressure in the high-pressure fuel passage falls within the allowable injection range when a fluctuating abnormality occurs (see, for example, Patent Document 3).

JP 2012-237274 A JP 2008-223636 A JP 2012-229623 A

  However, in the conventional fuel supply control device as described above, the estimation accuracy of the pressure of the low-pressure fuel due to the operation of the fuel pressurization pump is not sufficient for the following reasons, and the fuel injection by the low-pressure fuel injection valve There was room to improve the control accuracy of quantity.

  That is, the pulsation component of the fuel pressure in the fuel passage on the upstream side of the low pressure delivery pipe or the fuel pressurization pump is not due to the reciprocation of the plunger with the intake port of the fuel pressurization pump being opened, A pulsation component caused by reflection of pressure waves at the closed end such as the inner back end of the low-pressure delivery pipe is also included. And the pulsating component resulting from the reflection of the pressure wave always occurs during the operation period of the internal combustion engine. However, in the conventional fuel supply control device, since the pulsation component due to reflection is not taken into consideration, the estimation accuracy of the pressure fluctuation of the low-pressure fuel due to the operation of the fuel pressurizing pump is not sufficient.

  Therefore, the present invention takes into account the pressure pulsation component resulting from the pressure wave from the fuel pressurization pump and its reflection, and increases the accuracy of estimating the pressure fluctuation of the low pressure fuel resulting from the operation of the fuel pressurization pump. An object of the present invention is to provide a fuel supply control device capable of improving the control accuracy of the fuel injection amount from the injection valve.

  In order to achieve the above object, a fuel supply control apparatus according to the present invention includes (1) a low-pressure fuel injection having a low-pressure fuel pipe to which fuel is supplied from a feed pump and a low-pressure fuel injection valve for injecting the fuel from the low-pressure fuel pipe. A mechanism, a fuel pressurization pump that sucks the fuel from the low pressure fuel pipe and pressurizes the fuel to a high pressure level higher than a supply pressure level from the feed pump, and the high pressure level fuel is supplied from the fuel pressurization pump A high-pressure fuel injection mechanism including a high-pressure fuel pipe and a high-pressure fuel injection mechanism having a high-pressure fuel injection valve for injecting the fuel from the high-pressure fuel pipe, and fuel injection by at least the low-pressure fuel injection valve and the high-pressure fuel injection valve A fuel supply control device for controlling the amount of fuel, wherein the low-pressure fuel is transmitted from the fuel pressurization pump to the fuel in the low-pressure fuel pipe. A first pressure fluctuation component transmitted to the injection valve side, and a plurality of second pressure fluctuation components which are reflected in the low pressure fuel pipe and then reciprocated in the low pressure fuel pipe and propagated again to the low pressure fuel injection valve side Based on the above, the fuel injection amount by the low-pressure fuel injection valve is controlled.

  With this configuration, not only the first pressure fluctuation component transmitted from the fuel pressurization pump to the fuel in the low pressure fuel pipe and transmitted to the low pressure fuel injection valve side, but also reciprocating in the low pressure fuel pipe after being reflected in the low pressure fuel pipe. Thus, the pressure fluctuation transmitted to the low-pressure fuel injection valve side in the low-pressure fuel pipe is accurately estimated in consideration of the second pressure fluctuation component propagated again to the low-pressure fuel injection valve side. Therefore, the estimation accuracy of the pressure fluctuation of the low-pressure fuel due to the operation of the fuel pressurization pump is improved, and the fuel injection amount by the low-pressure fuel injection valve can be accurately controlled even if a certain level of pressure fluctuation occurs.

  In the fuel supply control device according to the present invention, (2) based on the propagation speed and attenuation coefficient of the pressure wave of the first pressure fluctuation component propagated from the fuel pressurization pump to the fuel in the low pressure fuel pipe. The second pressure fluctuation component may be estimated.

  In this case, the second pressure fluctuation component can be accurately estimated according to the propagation speed of the pressure wave in the low-pressure fuel pipe and the degree of attenuation. In addition, the propagation speed and attenuation coefficient of the pressure wave of the first pressure fluctuation component do not vary so much, and can be accurately measured by experiments in advance using a fuel supply system mounted on the internal combustion engine.

  In the fuel supply control device according to the present invention, (3) the fuel pressurizing pump has an input portion that is reciprocally driven by a rotating cam, and the first pressure fluctuation component is a rotation of the cam. It may be estimated based on the speed and the rotational angle position.

  In this case, the peak pressure and amplitude of the pressure wave can be estimated based on the rotational speed of the cam, and the pressure at that time can be estimated based on the rotational angle position of the cam.

  According to the present invention, there is provided a fuel supply control device capable of increasing the correction accuracy of the injection amount from the low pressure fuel injection valve in consideration of the pressure wave from the fuel pressurizing pump and the pressure pulsation component resulting from the reflection. can do.

1 is a schematic block configuration diagram of a fuel supply system for an internal combustion engine including a fuel supply control device according to an embodiment of the present invention. It is explanatory drawing explaining the relationship between the driving | operation of the fuel pressurization pump in the fuel supply system which concerns on one Embodiment of this invention in the valve opening state, and the pulsation of the fuel pressure of a suction side. (A) is explanatory drawing about the propagation of the pressure wave from the fuel pressurization pump in the fuel supply system which concerns on one Embodiment of this invention to the low pressure side delivery pipe, (b) is the low pressure side delivery pipe. It is explanatory drawing about reflection of the pressure wave. It is explanatory drawing of the estimation method of the fuel pressure in a delivery pipe in consideration of the pressure wave and reflected wave which are propagated from a fuel pressurization pump to a low pressure side delivery pipe in the fuel supply system which concerns on one Embodiment of this invention. Propagation pressure estimation for calculating a first pressure fluctuation component propagated from a fuel pressurization pump to a low-pressure delivery pipe and a second pressure fluctuation component rearriving after the reflection in the fuel supply system according to the embodiment of the present invention It is a flowchart of a process. Delivery fuel pressure estimation for estimating fuel pressure in a low pressure delivery pipe from a first pressure fluctuation component and a second pressure fluctuation component that currently arrive at a low pressure delivery pipe in a fuel supply system according to an embodiment of the present invention. It is a flowchart of a process. It is a graph which compares and shows an example of the pressure wave of a 1st pressure fluctuation component, and an example of the pressure wave which synthesize | combined the 2nd pressure fluctuation component, and a vertical axis | shaft is the fuel pressure in a low pressure side delivery pipe, and a horizontal axis Is the rotational angle position of the camshaft corresponding to time.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

(One embodiment)
FIG. 1 is a schematic block diagram of a fuel supply control device according to an embodiment of the present invention.

  First, the configuration will be described.

  FIGS. 1-7 is a figure for demonstrating the structure of the fuel supply system containing the fuel supply control apparatus which concerns on one Embodiment of this invention, and its effect | action.

  The fuel supply control device of this embodiment is a dual injection system that uses both in-cylinder injection that directly injects fuel into the combustion chamber in each cylinder and port injection that injects fuel into the intake port corresponding to each cylinder. For example, an in-line 4-cylinder spark ignition engine.

  First, the configuration will be described.

  The engine 10 shown in FIG. 1 has a plurality of cylinders 11, for example, four cylinders 11 indicated by # 1, # 2, # 3, and # 4, arranged in-line. In the engine 10, an intake passage 12 having a plurality of intake ports 13 corresponding to a plurality of cylinders 11 and an exhaust passage having a plurality of exhaust ports (not shown) are formed.

  Although not shown in detail, in each cylinder 11 of the engine 10, a piston (not shown) is housed to define a combustion chamber, and an intake valve and an exhaust valve are provided to open and close at a predetermined timing. . Further, the engine 10 is equipped with an ignition device having an ignition plug and an ignition coil (not shown).

  Further, the engine 10 is equipped with a low pressure fuel injection mechanism 20, a high pressure fuel injection mechanism 30, and a fuel supply control device 40 as a fuel supply system for supplying fuel to each combustion chamber.

  The low-pressure fuel injection mechanism 20 introduces a low-pressure side fuel, for example, gasoline, and performs port injection. The fuel tank 21, feed pump 22, pressure regulator 23, filter 24, low-pressure fuel supply pipe 25, low-pressure side delivery pipe 26 and a plurality of port injection injectors 27.

  The fuel tank 21 is supported by a vehicle body (not shown) and can be refueled. The feed pump 22 is a low-pressure fuel pump that can pressurize the fuel to a feed pressure that is a first pressure level and discharge the fuel into the low-pressure fuel supply pipe 25. The feed pump 22 is constituted by a circumferential flow pump which is a non-volumetric electric rotary pump, for example.

  The pressure regulator 23 is a pressure regulating valve that regulates the fuel discharged into the low pressure fuel supply pipe 25 to a preset supply pressure on the low pressure side. The filter 24 is formed of a filter medium that is disposed on the inlet side of the low-pressure fuel supply pipe 25 to remove foreign matters in the fuel.

  The low-pressure fuel supply pipe 25 and the low-pressure side delivery pipe 26 are low-pressure fuel pipes through which fuel discharged from the feed pump 22 is supplied to the plurality of port injectors 27. The pipe here is an arbitrary member that forms a fuel passage, and is not limited to a fuel pipe. One member through which the fuel passage is formed or a fuel passage is formed between them. A plurality of members may be used.

  The low pressure side delivery pipe 26 introduces the fuel pressurized to the first pressure level by the feed pump 22 and adjusted to the low pressure side supply pressure by the pressure regulator 23 through the low pressure fuel supply pipe 25. The low-pressure delivery pipe 26 has a pressure accumulating function that suppresses fuel pressure fluctuations at the time of injection by accommodating a predetermined volume of regulated fuel.

  More specifically, the low-pressure side delivery pipe 26 has a low-pressure fuel supply pipe 25 on one end side in the longitudinal direction extending in the series arrangement direction of the plurality of cylinders 11, for example, on the fourth cylinder (# 4 in FIG. 1) side. It is connected to the downstream end side. The low pressure side delivery pipe 26 is closed on the inner back end side separated from the low pressure fuel supply pipe 25. The low pressure side delivery pipe 26 is formed with a plurality of supply holes (not shown) for supplying fuel independently to the plurality of port injection injectors 27 at substantially equal pitches.

  The plurality of port injection injectors 27 are connected to the low-pressure delivery pipes 26 respectively, and fuel corresponding to the valve opening times (duty ratios) at predetermined intervals inside the plurality of intake ports 13 of the engine 10. The fuel can be injected with the injection amount. That is, each port injector 27 is a low-pressure fuel injection valve that injects fuel in the low-pressure delivery pipe 26 into any one of the plurality of intake ports 13.

  The high-pressure fuel injection mechanism 30 supplies high-pressure fuel for in-cylinder injection into each cylinder 11, and includes a high-pressure fuel pump 31, a high-pressure fuel supply pipe 35, a high-pressure delivery pipe 36, and a plurality of in-cylinder injections. An injector 37 (high pressure fuel injection valve) and a fuel pressure sensor 38 are included.

  The high-pressure fuel pump 31 has a pressurizing chamber 31a for introducing the fuel pressurized and fed to the first pressure level by the feed pump 22 through the branch pipe 25a of the low-pressure fuel supply pipe 25. The fuel in the pressure chamber 31 a is pressurized to a second fuel pressure level that is higher than the first fuel pressure level and discharged into the high-pressure fuel supply pipe 35. That is, the high-pressure fuel pump 31 can suck fuel from the branch pipe 25 a of the low-pressure fuel supply pipe 25 and pressurize the fuel to a high pressure level higher than the supply pressure level from the feed pump 22.

  A pulsation damper 29 that suppresses pressure pulsation of fuel in the branch pipe 25a is provided in the branch pipe 25a of the low-pressure fuel supply pipe 25 connected to the fuel inlet port of the high-pressure fuel pump 31. The pulsation damper 29 has, for example, an elastic diaphragm and a spring that receive fuel pressure inside, and is a known one that changes the internal volume by elastic deformation of the diaphragm.

  Specifically, the high-pressure fuel pump 31 has a pump housing 31h and a plunger 31p provided so as to be slidable back and forth within the pump housing 31h, and is defined between the pump housing 31h and the plunger 31p. The pressurizing chamber 31a changes its volume according to the displacement of the plunger 31p.

  A cam Cp is mounted on the camshaft 14 of the engine 10 so as to drive the plunger 31p. The high-pressure fuel pump 31 changes the volume of the pressurizing chamber 31a to perform the suction of fuel from the feed pump 22 and the pressurizing and discharging operations of the fuel in the pressurizing chamber 31a. Yes.

  The high-pressure fuel pump 31 further includes a follower lifter 31f that is driven up and down by a cam Cp in the vertical direction in the figure, and a compression spring 31g that urges the follower lifter 31f toward the cam Cp.

  Here, the cam Cp is integrally mounted on the camshaft 14 that is either the intake camshaft or the exhaust camshaft of the engine 10, and the rotational speed of the crankshaft is determined by the rotational power from the crankshaft of the engine 10. It is driven at a rotational speed of 1/2. Therefore, the cam Cp always rotates while the engine 10 is operating.

  Further, the cam Cp has a cam profile in which the radius (lift amount) is larger than the radius of other portions at least at one location in the circumferential direction. That is, the cam Cp has a cam profile such as a substantially elliptical shape or a polygon with rounded corners. In the present embodiment in which the engine 10 has four cylinders, the cam profile has a substantially square cam profile with rounded corners. Preferably used. The cam Cp in FIG. 1 shows a four-crest cam shape having such a cam profile.

  A suction control valve 32 is provided at the fuel inlet (not indicated) of the pressurizing chamber 31 a of the high-pressure fuel pump 31. The suction control valve 32 has a check valve function that allows the fuel to be sucked into the pressurizing chamber 31a from the branch pipe 25a of the low-pressure fuel supply pipe 25 while preventing the reverse flow.

  The suction control valve 32 includes a poppet-like valve body 32v, an electromagnetic drive coil 32c that electromagnetically drives the valve body 32v, and a spring 32k that normally biases the valve body 32v in the valve opening direction. . The valve body 32v can maintain the closed state when the urging force in the valve closing direction generated when the electromagnetic drive coil 32c is excited becomes larger than the urging force in the valve opening direction from the spring 32k. ing. The suction control valve 32 can release the fuel pressure in the pressurizing chamber 31a to the low pressure side while the valve is held open where the electromagnetic drive coil 32c is excited.

  The suction control valve 32 is a high-pressure fuel pump in which the fuel pressure in the pressurizing chamber 31a is lower than a certain differential pressure with respect to the fuel pressure fed from the feed pump 22 when the electromagnetic drive coil 32c is not excited. The valve can be opened when 31 is inhaled. Here, the suction control valve 32 is a normally open valve that excites the electromagnetic drive coil 32c during the pressurization and discharge period of the fuel, but the biasing directions of the electromagnetic drive coil 32c and the spring 32k are opposite to each other. Thus, the electromagnetic drive coil 32c may be a normally closed valve that is de-energized during fuel pressurization and discharge, or a relief valve that defines the upper limit of the fuel pressure in the high-pressure fuel supply pipe 35 may be provided. it can.

  The intake control valve 32 can be controlled by the ECU 41 via the driver circuit 42, and for this purpose, an electromagnetic drive coil 32 c of the intake control valve 32 is connected to the driver circuit 42.

  On the other hand, the high-pressure fuel supply pipe 35 between the high-pressure fuel pump 31 and the in-cylinder injector 37 is provided with a discharge valve 34 comprising a check valve with a spring, and the high-pressure fuel supply pipe 35 is disposed downstream of the upstream portion 35a. It is provided so as to be divided into side portions 35b. The discharge valve 34 opens when the discharge pressure of the fuel discharged from the high pressure fuel pump 31 becomes higher than the fuel pressure in the high pressure fuel supply pipe 35 by a predetermined discharge valve opening differential pressure. The fuel is allowed to be supplied to the injector 37 for injection.

  The high-pressure side delivery pipe 36 is configured so that high-pressure fuel pressurized to the second pressure level by the plunger-type high-pressure fuel pump 31 can be introduced through the high-pressure fuel supply pipe 35 and accumulated. The high-pressure fuel supply pipe 35 and the high-pressure side delivery pipe 36 are high-pressure fuel pipes to which high-pressure fuel is supplied from the high-pressure fuel pump 31.

  The plurality of in-cylinder injectors 37 are high-pressure fuel injection valves that can directly inject high-pressure fuel from the high-pressure side delivery pipe 36 into the plurality of cylinders 11 of the engine 10 in a predetermined order.

  The fuel pressure sensor 38 can detect the pressure of the fuel in the high-pressure side delivery pipe 36 and output the detected information to the fuel supply control device 40.

  The fuel supply control device 40 controls the amount of fuel injected by at least the plurality of port injectors 27 of the low pressure fuel injection mechanism 20 and the plurality of in-cylinder injectors 37 of the high pressure fuel injection mechanism 30, and is an electronic control unit. The ECU 41 and a driver circuit 42 for driving the actuators are configured.

  Although the detailed hardware configuration is not illustrated, the ECU 41 includes a backup memory such as a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and a nonvolatile memory, and further includes an input / output interface circuit. It is configured to include.

  Further, the ECU 41 communicates with other in-vehicle ECUs based on sensor information, set value information stored in the ROM or backup memory in accordance with a control program stored in advance in the ROM, The fuel injection amount corresponding to the ten operating states, the acceleration request, etc. is calculated. Then, the ECU 41 outputs the injection command signal to the port injector 27 and the in-cylinder injector 37, the valve drive instruction signal to the driver circuit 42 for driving the suction control valve 32, and the like in a timely manner. It has become.

  The ECU 41 adjusts the amount of fuel leakage from the pressurization chamber 31a by the suction control valve 32 based on at least the detection information of the fuel pressure sensor 38, so that the fuel supplied from the high-pressure fuel pump 31 to the high-pressure delivery pipe 36 By changing the amount, the fuel pressure in the high-pressure delivery pipe 36 can be controlled to an optimum fuel pressure in accordance with the operating state of the engine 10 and the injection characteristics of the in-cylinder injector 37. For example, the ECU 41 can set an ON time during which the electromagnetic drive coil 32c of the suction control valve 32 is in an excited state and an OFF time during which the excitation state is released within a certain signal cycle, and the ON time within the signal cycle. By changing the ratio, the amount of fuel leakage from the pressurizing chamber 31a by the suction control valve 32 can be adjusted.

  In addition, when the engine 10 is started, the ECU 41 first performs fuel injection by the port injection injector 27 for port injection, during which the fuel pressure in the high-pressure delivery pipe 36 detected by the fuel pressure sensor 38 is increased. When a preset pressure value close to the second pressure level is exceeded, it is determined that the second fuel pressure level necessary for fuel injection by the in-cylinder injector 37 can be reached, and for in-cylinder injection. The output of the injection command signal to the injector 37 is started.

  Further, the ECU 41 is based on, for example, in-cylinder injection from the in-cylinder injector 37, but the mixture formation is insufficient in the in-cylinder injection, such as when the engine 10 is warmed up or when the engine is under a low rotation and high load. Port injection is used in combination under specific operating conditions, or port injection from the port injection injector 27 is executed at the time of high rotation and high load in which port injection is effective.

  In addition, the ECU 41 executes a program for a propagation pressure estimation process and a delivery fuel pressure estimation process, which will be described later, stored in advance in the ROM, so that the low pressure side delivery pipe 26 used for port injection by the port injector 27 is used. The fuel pressure (hereinafter referred to as delivery fuel pressure) is estimated and calculated.

Specifically, as shown in FIG. 2, the ECU 41 determines the rotation speed w of the cam Cp and the rotation angle position corresponding to the lift at each time point of the cam Cp according to the rotation speed of the cam Cp. calculates the peak pressure P _AP of the pressure variations that occur in high pressure fuel pump 31, the pressure value P _at corresponding to the rotational angular position of the cam Cp. FIG. 2 shows the pressure fluctuation during one rotation of the cam Cp when the cam Cp has a four-head cam shape as shown in FIG. During this pressure fluctuation, the intake control valve 32 of the high-pressure fuel pump 31 is in an open state in which leakage of a predetermined flow rate or more may occur, but there is no passage between the pressurizing chamber 31a and the low-pressure fuel passage in the branch pipe 25a. An aperture can be interposed.

  Further, as shown in FIG. 3, the pressure fluctuation generated in the high-pressure fuel pump 31 becomes a pressure wave that travels into the low-pressure delivery pipe 26 through the low-pressure fuel supply pipe 25 and specifies the inner end of the low-pressure delivery pipe 26. It reaches the reflection position and is reflected there. Further, the pressure wave after being reflected at the specific reflection position (hereinafter referred to as a reflected wave) is reflected again on the high-pressure fuel pump 31 side and arrives again at the specific reflection position. Further, the pressure wave and the reflected wave propagated in the low pressure fuel supply pipe 25 and the low pressure side delivery pipe 26 in this way vary the pressure of the fuel in the low pressure side delivery pipe 26 while being attenuated during the propagation.

  Therefore, in the ROM or backup memory (hereinafter referred to as ROM or the like) of the ECU 41, the attenuation coefficients ξ1, ξ2, ξ3, ξ4 corresponding to the attenuation during the propagation of the pressure wave, the propagation time tp of the pressure wave, and the pressure wave Reflected wave propagation times tr1, tr2, tr3 corresponding to the number of reciprocations are stored in advance.

  The stored values of the attenuation coefficient ξ1-ξ4, the propagation time tp, and the reflected wave propagation time tr1-tr3 cause the pressure wave generated in advance by the high pressure fuel pump 31 to propagate in the low pressure fuel supply pipe 25 and the low pressure side delivery pipe 26, By conducting an experiment of reflecting at the specific reflection position, the actual attenuation amount and propagation time are calculated and set from the pressure wave input position and the information of the pressure sensor installed at the specific reflection position. The propagation time tp here corresponds to the propagation speed of the pressure wave that travels at a substantially constant speed in a pipe having a constant length formed by the low-pressure fuel supply pipe 25 and the low-pressure delivery pipe 26. The wave propagation time tr1-tr3 can also be calculated based on the propagation time tp.

The damping coefficients ξ1 to ξ4 are coefficients set according to the damping of the pressure wave in the elastic body corresponding to the structure and fuel properties of the low-pressure fuel supply pipe 25 and the low-pressure delivery pipe 26, respectively. These attenuation coefficients ξ1 to ξ4 are, for example, an attenuation coefficient ξ1 = ξ (for example, 0.5) corresponding to an attenuation amount until a pressure wave generated in the high pressure fuel pump 31 is propagated in the low pressure side delivery pipe 26. , and at least one round trip after reflection wave to be re-arrive at the low pressure side delivery pipe 26 the attenuation coefficient [xi] 2 ≒ xi] ³ corresponding to the attenuation amount (hereinafter, 1 also referred to as round-trip reflection wave).

In this embodiment, the influence of the reflected wave on the fuel pressure in the low pressure side delivery pipe 26 is reflected waves after two reciprocations (hereinafter also referred to as two reciprocal reflected waves) and reflected waves after three reciprocations (hereinafter three reciprocal reflected waves). and considering by the pressure variation component also referred to), 2 and the attenuation coefficient ξ3 ≒ ξ ⁵ corresponding to the attenuation of the reflected wave to be re-arrive at the low pressure side delivery pipe 26 after reciprocating low-pressure side delivery pipe 26 after three reciprocally a damping coefficient ξ4 ≒ ξ ⁷ corresponding to attenuation of the reflected wave to be re-arrival is further set to. The attenuation here includes attenuation due to pressure wave reflection and interference. Further, assuming that the influence due to the change in the fuel property is small, the estimation process is performed with the fuel property relating to the propagation of the pressure wave as a fixed value. However, the estimation process may be switched according to the environmental condition.

  The pressure wave propagation time tp is a propagation time required for the pressure wave generated by the high-pressure fuel pump 31 to propagate into the low-pressure delivery pipe 26.

  The reflected wave propagation times tr1, tr2, tr3 corresponding to the number of reciprocations are such that the pressure wave after being reflected at a specific reflection position such as the inner back end of the low pressure side delivery pipe 26 is reflected again on the high pressure fuel pump 31 side. This is the propagation time according to the number of reciprocations until the low-pressure delivery pipe 26 arrives again. That is, the reflected wave propagation times tr1, tr2, tr3 according to the number of round trips are reflected wave propagation time tr1 after one round trip, reflected wave propagation time tr2 after two round trips, and reflected wave propagation up to three round trips. It is time tr3.

  As described above, the pressure of the fuel in the low-pressure delivery pipe 26 varies under the influence of the pressure wave generated by the high-pressure fuel pump 31 and the reflected wave thereof, and can be transmitted to the port injection injector 27 side. Therefore, in the ECU 41, the fuel in the low pressure side delivery pipe 26 is transferred from the high pressure fuel pump 31 to the fuel in the low pressure side delivery pipe 26 at predetermined time intervals based on the rotational speed and rotational angle position of the cam Cp for each port injection and the stored information such as the ROM of the ECU 41. A first pressure fluctuation component Pc1 corresponding to the propagated pressure wave, and a plurality of second pressure fluctuation components Pc2 corresponding to a plurality of reflected waves after at least one reciprocation that arrives again in the low pressure side delivery pipe 26. , Each is estimated and calculated.

Specifically, the first pressure fluctuation component Pc1 is calculated when the pressure value P _At generated in the high-pressure fuel pump 31 is calculated according to the rotation speed and rotation angle position of the cam Cp in the propagation pressure estimation process described later. In parallel with the calculation process, it is calculated as a pressure component (= P _At × ξ1) multiplied by an attenuation coefficient ξ1 corresponding to the attenuation during propagation of the pressure wave from the high-pressure fuel pump 31 to the low-pressure delivery pipe 26. . The first pressure fluctuation component Pc1 calculated at this time is handled as arriving in the low-pressure delivery pipe 26 when the pressure wave propagation time tp elapses.

  On the other hand, the second pressure fluctuation component Pc2 is a first pressure fluctuation component Pc1 propagated from the high-pressure fuel pump 31 to the fuel in the low-pressure fuel supply pipe 25 and the low-pressure delivery pipe 26 in the propagation pressure estimation process described later. When calculated, the calculated value of the first pressure fluctuation component Pc1, the propagation time tp and the attenuation coefficient ξ1 of the pressure wave corresponding to the first pressure fluctuation component Pc1, the reflected wave propagation times tr1, tr2, tr3 and the attenuation It is calculated based on the coefficients ξ2-ξ4.

The second pressure fluctuation component Pc2 is reflected at the specific reflection position, and then reciprocates at least once in the low-pressure fuel supply pipe 25 and the low-pressure delivery pipe 26, and is again propagated into the low-pressure delivery pipe 26. Each time the reflected wave reflected at the specific reflection position makes a round trip to the high-pressure fuel pump 31, it is further attenuated by about the square of the attenuation during the propagation time tp and re-enters the low-pressure delivery pipe 26. arrive. Therefore, the second pressure fluctuation component Pc2, after the reflected wave propagation time pressure value P _At the propagation according to the reciprocating frequency from the start of the high-pressure fuel pump 31 tr1, tr2, tr3 has elapsed, the respective It is assumed that a plurality of pressure fluctuation components after attenuation corresponding to the number of reciprocations, for example, P _At × ξ ³ , P _At × ξ ⁵ , and P _At × ξ ⁷ re-arrive in the low pressure side delivery pipe 26.

  As shown in FIG. 4, when the cam Cp rotates with the intake control valve 32 open, the high-pressure fuel pump 31 generates a pressure wave having a period corresponding to the rotational speed of the cam Cp. , Pressure wave 2 and pressure wave 3 are sequentially output. At this time, the pressure fluctuation of the fuel in the low pressure side delivery pipe 26 includes the first pressure fluctuation component Pc1 corresponding to the latest pressure wave directly propagated from the high pressure fuel pump 31, and the low pressure side delivery preceding it. It can be considered that the second pressure fluctuation component Pc2 corresponding to the reflected wave that arrives in the pipe 26 and is reflected and then arrives again is synthesized.

  Therefore, whenever the port injection is executed by any of the port injection injectors 27, the ECU 41 executes a delivery fuel pressure estimation processing program that precedes the port injection. Then, a calculation for synthesizing the first pressure fluctuation component Pc1 corresponding to the latest pressure wave propagated from the high-pressure fuel pump 31 and the second pressure fluctuation component Pc2 derived from the reflected wave of the pressure wave preceding it is performed. Thus, the fuel pressure in the low-pressure delivery pipe 26 used for port injection by the port injector 27, that is, the delivery fuel pressure is estimated and calculated. Details of the delivery fuel pressure estimation process will be described later.

  The ECU 41 further estimates the estimated delivery fuel pressure in the low pressure side delivery pipe 26, and based on the estimated delivery fuel pressure and the air-fuel ratio required at the time of each injection to the engine 10, the fuel by the port injector 27 The injection time is variably controlled, and the fuel injection amount is suitably controlled.

  Next, the operation will be described.

  In the fuel supply device for an internal combustion engine of the present embodiment configured as described above, the port injection from the port injection injector 27 and the in-cylinder injection in the operation state of the feed pump 22 according to the operating state of the engine 10. The in-cylinder injection from 37 is switched, or the port injection from the port injector 27 and the in-cylinder injection from the in-cylinder injector 37 are both performed.

  For example, when the engine 10 is started, fuel injection by the port injector 27 for port injection is first executed, and the fuel pressure in the high-pressure delivery pipe 36 detected by the fuel pressure sensor 38 is close to the second pressure level. When a preset pressure value is exceeded, it is determined that the second fuel pressure level necessary for fuel injection by the in-cylinder injector 37 can be reached, and an injection command to the in-cylinder injector 37 is issued. The signal output is started.

  Therefore, in the starting stage from when the engine 10 starts a self-sustaining operation from a cranking state by a starter motor or the like to a stable idle operation state, fuel injection by the port injection injector 27 for port injection is executed exclusively. .

  In such a state, the cam Cp rotates with the intake control valve 32 open, and the plunger 31p of the high-pressure fuel pump 31 reciprocates, so that the low-pressure fuel supply pipe 25 and the low-pressure delivery pipe are connected from the high-pressure fuel pump 31. A pressure wave that pulsates the pressure is output to the 26th side.

  On the other hand, during this time, the ECU 41 detects the rotational speed and rotational angle position of the cam Cp every predetermined time immediately after the cranking start of the engine 10 or immediately after the start of the independent operation, and performs the propagation pressure estimation process as shown in FIG. In addition, whenever a port injection is executed by any one of the port injection injectors 27, a delivery fuel pressure estimation process as shown in FIG. 6 is executed prior to that.

In the propagation pressure estimation process shown in FIG. 5, first, the rotation speed and rotation angle position of the cam Cp are detected (step S11), and the generated pressure in the high-pressure fuel pump 31 is based on the rotation speed and rotation angle position of the cam Cp. P _At is calculated (step S12).

Next, based on the current generated pressure _PAt , the first pressure fluctuation component Pc1 propagated from the high-pressure fuel pump 31 to the fuel in the low-pressure delivery pipe 26 and at least one that arrives again in the low-pressure delivery pipe 26 The second pressure fluctuation component Pc2 corresponding to the reflected wave after the reciprocation is estimated and calculated for each. The calculated value and the cam rotation angle position corresponding to the arrival time and the re-arrival time of the first and second pressure fluctuation components Pc1 and Pc2 in the low-pressure delivery pipe 26 are a specific working memory of the RAM. The area is stored (step S13).

In the delivery fuel pressure estimation process shown in FIG. 6, first, the rotation angle position of the cam Cp is detected (step S21), and the first pressure fluctuation component Pc1 and the second pressure fluctuation component Pc1 at the arrival time corresponding to the detected rotation angle position are detected. Pressure fluctuation component Pc2, that is, all the pressure fluctuation components reaching the delivery pipe 26 at the present time, are the propagation pressure component P _At × ξ and the reflected wave-derived pressure components P _At × ξ ³ , P _At × ξ ⁵ , P _At × ξ ⁷ is read from a specific working memory area in the RAM (steps S22 to S25). The current pressure synthesized as the sum of the propagation pressure component P _At × ξ reaching the delivery pipe 26 and the pressure components P _At × ξ ³ , P _At × ξ ⁵ , and P _At × ξ ⁷ derived from the reflected wave at the present time. The fuel pressure in the low pressure side delivery pipe 26 is calculated as the delivery fuel pressure (step S26).

  FIG. 7 shows a composite corresponding to the delivery fuel pressure as shown by comparing an example of the pressure wave of the first pressure fluctuation component Pc1 and an example of the pressure wave Pd obtained by synthesizing the second pressure fluctuation component Pc2. The pressure wave Pd tends to shift exclusively to the amplitude increasing side and the phase delay side with respect to the first pressure fluctuation component Pc1. In this embodiment, the fuel pressure can be estimated in consideration of this deviation.

  When the estimated value of the delivery fuel pressure is calculated in this way, the basic fuel injection of the port injection injector 27 that executes the next port injection based on the air-fuel ratio required at the next port injection of the engine 10 or the like. Time is calculated, and the fuel injection amount is corrected to a suitable injection amount based on the estimated value of the delivery fuel pressure.

  Propagation from the intake control valve 32 to the low pressure delivery pipe 26 side, such as when the operation state of the engine 10 is stable and the intake control valve 32 for performing fuel injection by the in-cylinder injector 37 is closed. Under the operating state where the pressure fluctuation component is sufficiently small, the delivery fuel pressure estimation process described above can be interrupted.

  Thus, in the present embodiment, not only the first pressure fluctuation component Pc1 propagated directly from the high pressure fuel pump 31 to the fuel in the low pressure side delivery pipe 26 but also reflected in the low pressure side delivery pipe 26. Considering also the second pressure fluctuation component Pc2 derived from the reflected wave, the pressure fluctuation of the fuel in the low pressure side delivery pipe 26 caused by the operation of the high pressure fuel pump 31 is estimated with high accuracy, and the fuel port injection amount is calculated. The fuel pressure in the low pressure side delivery pipe 26 is estimated with high accuracy. Therefore, even if a certain amount of pressure fluctuation occurs in the low pressure delivery pipe 26, the fuel injection amount by the port injector 27 can be controlled with high accuracy.

  Further, in the present embodiment, based on the propagation speed and attenuation coefficient of the first pressure fluctuation component Pc1 propagated (propagated) from the high pressure fuel pump 31 to the fuel in the low pressure fuel supply pipe 25 and the low pressure side delivery pipe 26, Since the second pressure fluctuation component Pc2 is estimated, the second pressure fluctuation component Pc2 can be accurately estimated according to the propagation speed of the pressure wave in the low-pressure fuel supply pipe 25 and the low-pressure delivery pipe 26 and the degree of attenuation. become. In addition, the propagation speed and attenuation coefficient of the pressure wave corresponding to the first pressure fluctuation component Pc1 do not vary so much, and can be accurately measured by experiments in advance using a fuel supply system mounted on the engine 10, and sufficient control is achieved. Accuracy can be secured.

Furthermore, in the present embodiment, the high-pressure fuel pump 31 has a plunger 31p that is driven to reciprocate by the cam Cp, and the first pressure fluctuation component Pc1 is estimated based on the rotational speed and rotational angle position of the cam Cp. Therefore, the peak pressure _PAP and amplitude of the pressure wave corresponding to the first pressure fluctuation component Pc1 can be accurately estimated based on the rotational speed of the cam Cp. Moreover, based on the rotational angle position of the cam Cp, the pressure _PAt at that time can be estimated with high accuracy.

  As described above, in the present embodiment, the correction accuracy of the port injection amount from the port injection injector 27 is increased in consideration of both the pressure wave from the high-pressure fuel pump 31 and the pressure pulsation component caused by the reflected wave. The fuel supply control apparatus 40 which can be provided can be provided.

  In the above-described embodiment, the pressure wave is propagated into the low-pressure delivery pipe 26 by the reciprocating movement of the plunger 31p of the high-pressure fuel pump 31 with the intake control valve 32 opened. The fuel pressure in the low-pressure delivery pipe 26 can also be changed by intermittently sucking the fuel in the low-pressure fuel supply pipe 25 into the pressurizing chamber 31a by the high-pressure fuel pump 31 by opening and closing the suction control valve 32. . Therefore, when such pressure fluctuation is significant, it is conceivable to perform the same fuel pressure estimation as described above in consideration of the influence of the pressure wave and the reflected wave. The second pressure fluctuation component Pc2 is reflected at the specific reflection position and then reciprocated at least once in the low pressure fuel supply pipe 25 and the low pressure side delivery pipe 26, for example, once to three times, and then again the low pressure side delivery pipe 26. Although three types of pressure fluctuation components propagated inside are used, more types of pressure fluctuation components may be used.

  In addition, when a fuel pump that increases pulsation of fuel pressure is adopted for an engine fuel supply system that performs only port injection, fuel pressure estimation similar to that described above should be performed in consideration of the effects of pressure waves and reflected waves. However, the present invention is suitable when a low-pressure fuel supply mechanism and a high-pressure fuel supply mechanism having a cam-driven fuel pressurization pump are used in combination.

  As described above, the fuel supply control device according to the present invention takes into account the pressure pulsation component resulting from the pressure wave from the fuel pressurization pump and its reflection, and the fuel supplied to the injection from the low pressure fuel injection valve. Therefore, it is possible to provide a fuel supply control device that can sufficiently increase the injection amount accuracy from the low-pressure fuel injection valve. The present invention as described above is useful for all fuel supply control devices equipped in a fuel supply system of an internal combustion engine including a fuel pressurization pump that is mechanically driven by the power of the internal combustion engine.

DESCRIPTION OF SYMBOLS 10 ... Engine (internal combustion engine), 11 ... Cylinder, 12 ... Intake passage, 13 ... Intake port, 14 ... Cam shaft, 20 ... Low pressure fuel injection mechanism, 21 ... Fuel tank, 22 ... Feed pump (low pressure fuel pump), 23 ... pressure regulator, 24 ... filter, 25 ... low pressure fuel supply pipe (low pressure fuel pipe), 25a ... branch pipe, 26 ... low pressure side delivery pipe (low pressure fuel pipe), 27 ... port injection injector, 29 ... pulsation damper, DESCRIPTION OF SYMBOLS 30 ... High pressure fuel injection mechanism, 31 ... High pressure fuel pump, 31a ... Pressurization chamber, 31f ... Follower lifter, 31g ... Compression spring, 31h ... Pump housing, 31p ... Plunger (input part), 32 ... Suction control valve, 32c ... Electromagnetic Drive coil, 32k ... spring, 32v ... valve, 34 ... discharge valve, 35 ... high pressure fuel supply pipe (high Fuel pipe), 35a ... upstream part, 35b ... downstream part, 36 ... high pressure side delivery pipe (high pressure fuel pipe), 37 ... in-cylinder injector (high pressure fuel injection valve), 38 ... fuel pressure sensor, 40 ... Fuel supply control device, 41 ... ECU (electronic control unit), 42 ... driver circuit, Pc1 ... first pressure fluctuation component, Pc2 ... second pressure fluctuation component, tr1, tr2, tr3 ... reflected wave propagation time

Claims (3)

A low-pressure fuel injection mechanism having a low-pressure fuel pipe to which fuel is supplied from a feed pump and a low-pressure fuel injection valve for injecting the fuel from the low-pressure fuel pipe; A fuel pressurizing pump for pressurizing to a high pressure level higher than a supply pressure level, a high pressure fuel pipe to which the fuel at the high pressure level is supplied from the fuel pressurizing pump, and a high pressure fuel injection valve for injecting the fuel from the high pressure fuel pipe. A fuel supply control device for controlling a fuel injection amount by at least the low-pressure fuel injection valve and the high-pressure fuel injection valve.
The first pressure fluctuation component transmitted from the fuel pressurization pump to the fuel in the low pressure fuel pipe and transmitted to the low pressure fuel injection valve side is reflected in the low pressure fuel pipe and then reciprocated in the low pressure fuel pipe. A fuel supply control device that controls the fuel injection amount by the low-pressure fuel injection valve based on the plurality of second pressure fluctuation components propagated again to the low-pressure fuel injection valve side.   The second pressure fluctuation component is estimated based on a propagation speed and a damping coefficient of a pressure wave of the first pressure fluctuation component propagated from the fuel pressurization pump to the fuel in the low-pressure fuel pipe. The fuel supply control device according to claim 1. The fuel pressurization pump has an input portion that is reciprocally driven by a rotating cam;
The fuel supply control device according to claim 1, wherein the first pressure fluctuation component is estimated based on a rotational speed and a rotational angle position of the cam.

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