JP2010024851A - Fuel supply device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection device for an internal combustion engine inhibiting amplification of pulsation accompanying resonance of a pulsation damper. <P>SOLUTION: A low pressure regulator 19 is operated in an open state of a fuel pressure selection valve 22, insides of delivery pipes 11R, 11L get in low fuel pressure states, and a downstream side of the delivery pipe 11L is blocked. A high pressure regulator 17 is operated in a close state of the fuel pressure selection valve 22, insides of the delivery pipes 11R, 11L get in high fuel pressure states, and the downstream side of the delivery pipe 11L is opened. In an engine operation condition where the pulsation damper 23 resonates under the low fuel pressure state, the downstream side of the delivery pipe 11L is opened by setting the fuel selection valve 22 in a close state and getting insides of the delivery pipes 11R, 11L in the high fuel pressure state. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel supply device that supplies fuel to an internal combustion engine.

A fuel supply device applied to an internal combustion engine pumps fuel stored in a fuel tank to a delivery pipe by a fuel pump and injects it from an injector connected to the delivery pipe, thereby fueling the cylinder corresponding to the injector. Supply. In such a fuel supply device, a part of the fuel pumped from the fuel pump to the delivery pipe returns to the fuel tank via the pressure regulator, so that the fuel pressure (fuel pressure) in the delivery pipe becomes a predetermined pressure. What is prescribed in is known. In this type of fuel supply device, the amount of fuel injection per unit time of the injector is defined by adjusting the fuel pressure. (For example, Patent Document 1)
By the way, in the internal combustion engine under various operating conditions, the fuel injection timing for each injector is set according to the engine speed, the required load on the internal combustion engine, and the like. For this reason, fuel pulsation due to such fuel pressure fluctuations, for example, under operating conditions in which fuel pressure fluctuations periodically occur in the delivery pipe, such as operating conditions in which intermittent fuel injection is performed between injectors. Will occur. Such fuel pulsation causes not only problems such as vibration of the delivery pipe and the noise caused by the vibration, but also causes problems such as a decrease in drivability by varying the fuel injection amount in the unit injection time of each injector. In view of this, a technology for suppressing such pulsation by providing a pulsation damper having a diaphragm urged by an elastic material or the like in a delivery pipe or the like has been conventionally known (for example, for pulsation of fuel) (for example, Patent Document 2, Patent Document 3).
JP-A-7-189873 JP 62-182476 A JP 2000-297726 A

  On the other hand, the frequency of pulsation caused by such fuel injection differs depending on the rotational speed that is an index of fuel injection timing, and depending on the value of the rotational speed, the frequency of pulsation may be close to the natural frequency of the pulsation damper. is there. Since the diaphragm in the pulsation damper is displaced when subjected to pulsation, which is an external force, when the vibration frequency of the pulsation and the natural frequency of the pulsation damper are close to each other, resonance of the diaphragm is induced and fuel pulsation is induced. On the contrary, there is a risk of amplifying the pulsation. Moreover, in recent years, the fluctuation in fuel pressure tends to increase due to an increase in the fuel injection amount per unit time of the injector due to the higher output of the internal combustion engine. Therefore, the pulsation caused by the resonance of the pulsation damper is further amplified. There is a concern. The above-mentioned problems can be alleviated by enlarging the volume per unit displacement of the diaphragm to reduce the displacement caused by pressure fluctuations, that is, by increasing the size of the pulsation damper. In some cases, such large pulsation dampers could not be secured due to a decrease in the number of pulsations.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fuel supply device for an internal combustion engine in which amplification of pulsation accompanying resonance of a pulsation damper is suppressed.

In the following, means for achieving the above object and its effects are described.
According to the first aspect of the present invention, there is provided a supply passage comprising a pressure feed passage through which fuel is pumped from a fuel tank, a delivery pipe connected to the pressure feed passage and provided with an injector, and the delivery pipe connected to the delivery pipe. A recirculation passage for recirculating surplus fuel in the pipe to the fuel tank, a low fuel pressure state in which the circulation of the recirculation passage is prohibited and the pressure in the supply passage is set to the first pressure, and the circulation of the recirculation passage is permitted. A fuel supply device for an internal combustion engine comprising a fuel pressure selection means for selecting a high fuel pressure state in which a pressure in the supply passage is set to a second pressure higher than the first pressure, the fuel supply device being provided in the supply passage, A pulsation damper that suppresses fuel pulsation generated by fuel injection, and the fuel pressure selection means in an engine operating state in which the pulsation damper resonates in the low fuel pressure state; There is summarized in that for selecting the high fuel pressure condition.

  In the low fuel pressure state where excess fuel in the supply passage does not pass through the return passage and is not recirculated, the delivery pipe and the return passage are connected to each other because a clogging that prohibits the flow of the return passage is formed in the delivery pipe. A continuous fuel flow that passes through and returns to the fuel tank cannot be obtained. When intermittent fuel consumption due to the fuel injection of the injector is executed under such a low fuel pressure state, only the amount of fuel consumption by the injector is intermittently supplied from the fuel tank to the supply passage. For this reason, intermittent fuel flow for each fuel injection of the injector occurs inside the supply passage, and fuel pulsation is likely to occur.

  When the frequency of pulsation due to fuel injection is close to the natural frequency of the pulsation damper, resonance of the pulsation damper is induced, and even the pulsation due to the resonance propagates inside the common passage. It becomes like this. Although the pulsation caused by the resonance of the pulsation damper propagates in the supply passage composed of the delivery pipe and the pressure-feed passage, the delivery pipe is reflected in the supply passage because the return passage is closed. Propagate to. As a result, both of the pulsation generated by the resonance of the pulsation damper and the pulsation reflected from the blockage of the return passage are propagated to the fuel supplied to the injector.

  According to this invention, in the engine operating state in which the pulsation damper resonates in the low fuel pressure state, the high fuel pressure state is selected and the circulation of the recirculation passage downstream of the supply passage is permitted. In such a state, since there is recirculation on the downstream side of the supply passage, continuous fuel flow in the supply passage can be realized, and pulsation due to fuel injection can be suppressed by reducing intermittent flow. Or even the pulsation accompanying the resonance of the pulsation damper can be released from the supply passage. As a result, pulsation amplification accompanying resonance of the pulsation damper can be suppressed as compared with the case where the reflux passage is closed.

  The gist of the invention described in claim 2 is that the fuel pressure selection means selects the high fuel pressure state at a selected rotational speed that is a rotational speed at which the pulsation damper resonates in the low fuel pressure state.

  The resonance of the pulsation damper is induced by the pulsation that accompanies the fuel injection, which is the external force that the pulsation damper receives. The presence or absence of the pulsation that accompanies this fuel injection or the magnitude of the amplitude of the pulsation It depends on the rotational speed that is an index of the injection timing.

  According to the present invention, as described above, since the high fuel pressure state is selected based on the presence or absence of pulsation due to fuel injection or the rotational speed that is an index of the amplitude of the pulsation, the presence or absence of resonance of the pulsation damper Alternatively, the high fuel pressure state is selected based on the magnitude of the amplitude. As a result, it is possible to effectively suppress the pulsation amplification accompanying the resonance of the pulsation damper.

According to a third aspect of the present invention, the fuel pressure selection means is configured so that the fuel pressure selection means has the high fuel pressure on the condition that a load required for the internal combustion engine in the low fuel pressure state is not less than a threshold value that makes the resonance amplitude of the pulsation damper excessive. The gist is to select the fuel pressure state.

  The amplitude of the pulsation accompanying fuel injection becomes smaller as the pressure fluctuation accompanying the fuel injection becomes smaller, in other words, as the fuel injection amount which is an index of pressure fluctuation becomes smaller. For example, even when the rotational speed at which the fuel injection timing of each injector is not superimposed, if the fuel injection amount is sufficiently small, that is, if the required load correlated with the fuel injection amount is sufficiently small, the fuel injection is accompanied. Since the amplitude of the pulsation is sufficiently small, the resonance of the pulsation damper associated therewith can be sufficiently suppressed. According to the present invention, since a threshold is provided for the required load when selecting a high fuel pressure state, unnecessary pressure fluctuations caused by switching of fuel pressure do not occur when the amplitude of pulsation accompanying fuel injection is small. .

  Further, the more fuel that is recirculated in the high fuel pressure state, the more fuel that passes through the vicinity of the injector, which is in the vicinity of the combustion chamber, and returns to the fuel tank. Therefore, the higher the fuel pressure opportunity, the higher the temperature of the fuel in the fuel tank. According to the above-described configuration, the frequency of the high fuel pressure state can be reduced by an amount corresponding to the opportunity that the required load becomes equal to or less than the threshold value, as compared with the case where the high fuel pressure state is selected only by the rotation speed. Therefore, it is possible to suppress the high temperature of the fuel in the fuel tank as described above.

  According to a fourth aspect of the present invention, the fuel pressure selecting means has the fuel pressure selecting means on the condition that the fuel injection amount required for the injector in the low fuel pressure state is not less than a threshold value that makes the resonance amplitude of the pulsation damper excessive. The main point is to select a high fuel pressure state.

  According to this configuration, since the high fuel pressure state is selected based on the required fuel injection amount, the high fuel pressure state can be selected based on a direct parameter related to the amplitude of pulsation accompanying fuel injection. Therefore, the amplitude of the pulsation in the supply passage can be more reliably reduced.

The gist of the invention described in claim 5 is that the threshold value is a value for each selected rotational speed.
The resonance of the pulsation damper is induced by pulsation accompanying fuel injection, which is an external force received by the pulsation damper. The presence or absence of pulsation accompanying this fuel injection, or the amplitude of the pulsation, is determined as described above. It depends on the rotational speed of the engine, the required load on the internal combustion engine, and the fuel injection amount of each injector. According to this configuration, since the required load for selecting the high fuel pressure state and the threshold value of the fuel injection amount are values for each selected rotational speed, an accurate threshold value corresponding to the rotational speed is selected when selecting the high fuel pressure state. Can be set.

The gist of the invention described in claim 6 is that the pulsation damper is provided in the delivery pipe.
According to the present invention, since the pulsation damper is disposed in the vicinity of the injector, the pulsation accompanying fuel injection can be effectively suppressed by the pulsation damper. And since the amplification of the pulsation due to the resonance of the pulsation damper is suppressed under such a configuration, the pulsation can be effectively suppressed in the range of all the rotational speeds including the selected rotational speed.

Hereinafter, an embodiment of a fuel supply device for an internal combustion engine according to the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of a fuel supply device that supplies fuel to an eight-cylinder on-board internal combustion engine having a V-type cylinder arrangement. FIG. 2 is a cross-sectional view showing a cross-sectional structure of a pulsation damper provided in the fuel supply apparatus. FIG. 3 is a graph showing the relationship between the diaphragm amplitude and the rotation speed in the pulsation damper.

  As shown in FIG. 1, the internal combustion engine is provided with a pair of delivery pipes 11R and 11L corresponding to the left and right banks. Four injectors 12 are connected to these delivery pipes 11R and 11L corresponding to the respective cylinders. Each injector 12 opens and closes a needle valve (not shown) disposed therein to inject and supply fuel in the delivery pipes 11R and 11L to each cylinder.

  A fuel pump 14 provided inside the fuel tank 13 is connected to one end of one delivery pipe 11R by a main pipe 15 as a pressure feed passage. The other delivery pipe 11L is connected to the other end of this one delivery pipe 11R via a communication pipe 16, and the fuel from the fuel tank 13 is supplied by connecting these delivery pipes 11R and 11L in series. Supplied from the delivery pipe 11R to the delivery pipe 11L. In the present embodiment, a delivery path is constituted by these delivery pipes 11R and 11L, the main pipe 15 and the communication pipe 16.

  A high pressure return pipe 18 is connected to the downstream side of the delivery pipe 11L via a high pressure regulator 17. The high pressure regulator 17 is a pressure regulating valve that regulates the fuel injection pressure (fuel pressure) in each of the delivery pipes 11R and 11L to a high injection pressure PH (in the present embodiment, about 400 kPa: second pressure) that is a predetermined pressure value. is there. The high pressure regulator 17 is opened when the fuel pressure in the delivery pipes 11R, 11L exceeds the high injection pressure PH by the fuel pumped from the fuel pump 14, and the excess fuel is returned to the fuel tank 13 via the high pressure return pipe 18. By adjusting the fuel pressure, the fuel pressure is adjusted to the high injection pressure PH.

  On the other hand, a low-pressure return pipe 21 having a low-pressure regulator 19 is connected to a portion located near the fuel tank 13 on the upstream side of the main pipe 15. The low pressure regulator 19 adjusts the fuel pressure in each of the delivery pipes 11R and 11L to a low injection pressure PL (in this embodiment, about 284 kPa: the first pressure) that is a pressure value lower than the high injection pressure PH. It is a pressure regulating valve. The low pressure regulator 19 is opened when the fuel pressure in the delivery pipes 11R and 11L exceeds the low injection pressure PL by the fuel pumped from the fuel pump 14, and surplus fuel is supplied to the fuel tank 13 via the low pressure return pipe 21. The fuel pressure is adjusted to the low injection pressure PL by refluxing.

  The low pressure return pipe 21 is provided with a fuel pressure selection valve 22 constituting fuel pressure selection means. The fuel pressure selection valve 22 is a valve that switches between the main pipe 15 and the low-pressure return pipe 21 between a communication state and a non-communication state. By opening the valve, the low-pressure regulator 19 is switched to a state that can be opened. By closing the valve, the high-pressure regulator 17 is switched to a state where it can be opened.

  In the open state of the fuel pressure selection valve 22, the fuel flows back from the main pipe 15 to the low pressure return pipe 21, so that the fuel pressure in the delivery pipes 11 R and 11 L rises and the high pressure regulator 17 is opened. In addition, the fuel pressure is adjusted to the low injection pressure PL by opening the low pressure regulator 19. On the other hand, when the fuel pressure selection valve 22 is closed, the fuel does not recirculate from the main pipe 15 to the low pressure return pipe 21, so that all of the fuel supplied from the fuel pump 14 to the main pipe 15 is sent to the delivery pipes 11R and 11L. The fuel pressure is adjusted so that the fuel pressure is adjusted to the high injection pressure PH by opening the high pressure regulator 17. As described above, in the fuel supply device of the present embodiment, the fuel pressure selection valve 22 is selected to be in the open state or the closed state, so that the fuel pressure of the delivery pipes 11R and 11L is the high fuel pressure state that is the high injection pressure PH or low. The low fuel pressure state that is the injection pressure PL is selected.

  Each delivery pipe 11R, 11L is provided with a pulsation damper 23 for suppressing the pulsation of the fuel generated by the fuel injection of the injector 12. Since the pulsation dampers 23 provided in the pair of delivery pipes 11R and 11L have the same internal structure, the pulsation damper 23 provided in the delivery pipe 11R will be described below.

  As shown in FIG. 2, the delivery pipe 11R is provided with a branch port 11P extending outward from the delivery pipe 11R, and the pulsation damper 23 is formed in the opening of the branch port 11P so as to close the opening. It is arranged. The casing of the pulsation damper 23 is formed in a cylindrical shape with a lid and is fitted to the branch port 11P with the seal member 24 interposed therebetween, and an introduction hole 23a that is an opening of the casing communicates with the branch port 11P. As a result, the fuel in the delivery pipe 11R is introduced into the pulsation damper 23.

  A diaphragm 23b is disposed inside the casing of the pulsation damper 23 so as to block the introduction hole 23a, and the diaphragm 23b is biased toward the introduction hole 23a by a spring 23c. The diaphragm 23b is elastically deformed in response to the pulsation of the fuel. When the fuel pulsation generated in the delivery pipe 11R propagates inside the pulsation damper 23, the diaphragm 23b and the spring 23c are displaced according to the pulsation, and the volume for storing the fuel is changed based on the displacement. This suppresses the pulsation. In the present embodiment, the pulsation damper 23 having such a function is disposed at a position close to the injector 12 that is a generation source of pulsation caused by fuel injection, so that pulsation in the delivery pipe 11R is efficiently suppressed. . The pulsation damper 23 has a structure in which the diaphragm 23b is urged by the spring 23c. However, in order to suppress pulsation, for example, a pulsation damper having a diaphragm made of an elastic material and omitting the spring 23c may be used. May be.

  On the other hand, even in the case of such a pulsation damper 23, when the vibration frequency of the pulsation generated in the delivery pipes 11R and 11L becomes close to the natural frequency of the pulsation damper 23, the diaphragm 23b receives the pulsation, thereby the diaphragm. The resonance of 23b is induced. In particular, in the low fuel pressure state described above, the downstream side of the delivery pipe 11L is blocked, so that continuous fuel flow cannot be obtained in the delivery pipes 11R and 11L, and fuel is intermittently injected by the fuel injection of the injector 12. When the fuel is consumed, pulsation occurs every time the fuel is intermittently consumed. When the pulsation damper 23 resonates in such a state, the pulsation accompanying the resonance propagates to the upstream side and the downstream side of the pulsation damper 23, but is reflected by the blockage because the downstream side is blocked. Propagates within the delivery pipes 11R, 11L.

  As a result, both the pulsation from the pulsation damper 23 and the pulsation from the above-described blockage are propagated in the fuel supplied to each injector 12 among the pulsations accompanying the resonance of the pulsation damper 23. In the fuel supply device according to the present embodiment, the fuel pressure selection valve 22 is controlled to be opened and closed as part of the fuel injection control in order to suppress the amplification of pulsation caused by such resonance.

  Next, fuel injection control using the fuel supply device will be described below. Fuel injection control using the fuel supply device is executed by an electronic control device 41 (see FIG. 1) which is a control device mounted on the vehicle.

The electronic control unit 41 includes a calculation unit that executes calculation processing related to control of the fuel supply device, a program and data necessary for various controls, and a storage unit that temporarily stores calculation results of the calculation unit And an input / output port for inputting / outputting a signal to / from the outside.

  Detection signals from various sensors for detecting the engine operating state are input to the input port of the electronic control unit 41. Specifically, from the fuel pressure selection valve 22, a detection signal indicating whether the fuel pressure selection valve 22 is open or closed, in other words, whether the fuel pressure is a high injection pressure PH or a low injection pressure. A detection signal indicating whether it is PL is input. A detection signal indicating the rotational speed NE of the internal combustion engine is input to the input port from a rotational speed sensor 42 provided in the vicinity of the crankshaft (not shown). A detection signal indicating the intake air amount GA is input from an air flow meter 43 provided in an intake passage (not shown) communicating with each cylinder. Further, in the exhaust pipe 25 of the internal combustion engine, a detection signal indicating the oxygen concentration of the exhaust is input from an oxygen concentration sensor 44 provided upstream of the three-way catalyst 26.

  On the other hand, the injector 12, the fuel pressure selection valve 22, and the like are electrically connected to the output port of the electronic control unit 41, respectively. The electronic control unit 41 grasps the operating state of the internal combustion engine based on the detection signals from the respective sensors, and performs various command signals via the output port in order to execute fuel injection control corresponding to the engine operating state at that time. Is output to each of the above parts.

  In the fuel injection control executed by the electronic control unit 41, first, an intake air amount that is a detection value is obtained using a map in which a reference fuel injection amount for obtaining a theoretical air-fuel ratio is associated with the intake air amount GA and the rotational speed NE. The reference fuel injection amount is calculated by applying the GA and the rotational speed NE to the map. Further, the actual air-fuel ratio in the previous fuel injection is obtained based on the required value of the fuel injection amount in the previous fuel injection (requested fuel injection amount TAU) and the oxygen concentration which is the detected value of the oxygen concentration sensor 44. A feedback correction amount related to the required fuel injection amount TAU is calculated based on the degree of deviation between the actual air-fuel ratio and the theoretical air-fuel ratio. Based on the feedback correction amount and the reference fuel injection amount, the required fuel injection amount TAU in the current fuel injection control is calculated.

  When the required fuel injection amount TAU is calculated, in the fuel injection control executed by the electronic control unit 41, the pulse output from the rotational speed sensor 42 is used according to the crank angle, and the fuel injection according to the rotational speed NE is used. The time is calculated. In calculating the fuel injection timing, for example, the fuel injection timing is set as an advance value with respect to a reference crank angle such as top dead center, and the fuel injection timing for obtaining the optimum combustion is determined based on the intake air amount GA and the rotational speed NE. A map associated with is used. Then, the fuel injection timing is calculated by applying the intake air amount GA and the rotational speed NE to this map.

  When the required fuel injection amount TAU is calculated, the electronic control unit 41 selects a high pressure injection condition based on the required fuel injection amount TAU and the engine operating state in order to select a fuel pressure for injecting the required fuel injection amount TAU. It is determined whether or not is established.

  The high pressure injection condition is a condition set for injecting the required fuel injection amount TAU under the high injection pressure PH. When the high pressure injection condition is satisfied, the required fuel injection amount TAU is In order to inject under the high injection pressure PH, the fuel pressure selection valve 22 is closed and the fuel pressure in the delivery pipes 11R and 11L is held at the high injection pressure PH. Under this high pressure injection condition, the required fuel injection amount TAU described above is a high value that is difficult to obtain under the low injection pressure PL, for example, a request to the internal combustion engine calculated by the rotational speed NE, the intake air amount GA, and the like. It is mentioned that it is a high load area | region where load becomes higher than a predetermined value.

When the high pressure injection condition is not satisfied at the fuel injection timing executed by the electronic control unit 41, the electronic control unit selects whether or not to inject the required fuel injection amount TAU at the low injection pressure PL. In 41, it is determined whether or not the resonance suppression condition is satisfied based on the required fuel injection amount TAU and the engine operating state.

  The resonance suppression condition is a condition set to suppress amplification of pulsation due to resonance of the pulsation damper 23. The resonance of the pulsation damper 23 is induced by the external force received by the diaphragm 23b, in other words, the pulsation of the fuel accompanying the fuel injection. The pulsation of the fuel accompanying the fuel injection is intermittently generated by the injector 12. It occurs when injection is performed. The pulsation caused by the fuel injection is less likely to occur as the fuel injection timing of each injector overlaps, in other words, as the fuel flow in the delivery pipes 11R and 11L becomes more continuous. On the contrary, the fuel pulsation accompanying the fuel injection is more likely to occur as the fuel injection timing of each injector 12 becomes intermittent, in other words, the fuel flow in the delivery pipes 11R and 11L becomes intermittent.

  If the vibration frequency of the pulsation caused by the fuel injection is significantly different from the natural frequency of the pulsation damper 23, the resonance is hardly induced, and conversely, the vibration frequency of the pulsation accompanying the fuel injection is less than the pulsation damper. If it is close to the natural frequency of 23, the resonance is likely to be induced. Further, as the external force received by the diaphragm 23b, that is, the amplitude of the pulsation accompanying the fuel injection becomes smaller, the amplitude of the resonance of the pulsation damper 23 becomes smaller. growing.

  The resonance suppression condition is an engine operation state set based on the vibration frequency and amplitude of the pulsation. In the engine operation state in which the pulsation is amplified by the resonance in the low fuel pressure state, the high fuel pressure state is selected as the fuel pressure. The conditions are set as follows. An example of the engine operating state that serves as an index of such pulsation frequency is the rotational speed NE used when calculating the fuel injection timing. Further, the required fuel injection amount TAU can be given as an engine operating state serving as an index of such pulsation amplitude.

  Therefore, the resonance suppression condition in the present embodiment includes (a) the rotational speed NE that is an index of pulsation frequency is the selected rotational speed region NEf, and (b) required fuel injection that is an index of amplitude of pulsation. A logical product condition that the amount TAU is equal to or greater than the selected fuel injection amount TAUT is set.

  In the selected rotational speed region NEf and the selected fuel injection amount TAUT, values based on tests performed in advance are set, and the displacement amount of the diaphragm 23b, which is an index of the resonance amplitude of the pulsation damper 23, is set to the low injection pressure PL. The rotational speed NE and the required fuel injection amount TAU when it becomes excessively large under are set. In setting the selected rotational speed region NEf, for example, as shown in FIG. 3, the relationship between the rotational speed NE, which is an index of the pulsation frequency, and the displacement amount Δx of the diaphragm 23b is changed to a single or a plurality of different required fuels. It is acquired under the injection amount TAU. In this relationship, the range of the rotational speed NE (between the lower limit rotational speed NEL and the upper limit rotational speed NEH) in which the displacement amount Δx of the diaphragm 23b is greater than or equal to the reference displacement amount Δx1 is set as the selected rotational speed region NEf. The In setting the selected fuel injection amount TAUT, the relationship between the required fuel injection amount TAU, which is an index of the amplitude of pulsation, and the displacement amount Δx of the diaphragm 23b is acquired, and the displacement amount Δx of the diaphragm 23b is included in the relationship. The minimum required fuel injection amount TAU that becomes the reference displacement amount Δx1 is set as the selected fuel injection amount TAUT.

When the resonance suppression condition is satisfied, even if the required fuel injection amount TAU is low and can be injected at the low injection pressure PL, the fuel of the required fuel injection amount TAU is reduced under the high injection pressure PH. The fuel pressure selection valve 22 is forcibly closed in order to inject at this time. As a result, in an engine operating state where pulsation can be amplified in a low fuel pressure state, the fuel pressure can be forcibly switched to a high fuel pressure state, and therefore the high pressure regulator 17 can be opened. In other words, since the downstream side of the delivery pipe 11L can be opened, the fuel can be continuously flowed through the delivery pipes 11R and 11L, so that the pulsation itself associated with fuel injection can be suppressed. . Furthermore, even if the pulsation damper 23 resonates, part of the pulsation associated with the resonance can be released from the downstream side of the delivery pipe 11L to the fuel tank 13, so that the pulsation associated with the resonance is also suppressed. can do.

  As a result, pulsation that can occur in a low fuel pressure state can be suppressed, and amplification of pulsation can be suppressed even if the pulsation damper 23 resonates. When the resonance suppression condition is not satisfied, the fuel pressure selection valve 22 is opened to inject the fuel of the required fuel injection amount TAU under the low injection pressure PL.

  Incidentally, in order to suppress the pulsation amplification described above, only the rotation speed NE is in the selected rotation speed region NEf may be set as the resonance suppression condition. However, when this resonance suppression condition is satisfied, the surplus fuel passes through the delivery pipes 11R and 11L in the vicinity of the combustion chamber and is returned to the fuel tank 13, so that the fuel tank with heated fuel is used. There is a concern about the high temperature inside 13. Therefore, as described above, by adopting the logical product condition of the condition (a) related to the rotational speed NE and the condition (b) related to the required fuel injection amount TAU as the resonance suppression condition, the recirculation frequency of the surplus fuel whose temperature is increased It is possible to suppress the increase in temperature in the fuel tank 13 in suppressing the fuel pulsation.

  As described above, when the fuel pressure for injecting the required fuel injection amount TAU is selected according to the high pressure injection condition and the resonance suppression condition, the fuel injection control executed by the electronic control unit 41 performs the required fuel under the selected fuel pressure. In order to inject the injection amount TAU, the fuel injection time of the injector 12 is calculated. As the calculation of the fuel injection time, for example, a function associated with the injection time TAU of the injector 12 and the fuel pressure is used, and the selected fuel pressure and the calculated fuel injection amount TAU are calculated. The fuel injection time is calculated by applying to this function or the like.

  Next, a control routine for fuel injection control executed by the electronic control unit 41 will be described with reference to FIG. FIG. 4 is a flowchart for explaining a control routine of fuel injection control. The fuel injection control is repeatedly executed by the electronic control device 41 from the start of the internal combustion engine.

  When the fuel injection control is started, first, the electronic control unit 41 grasps the engine operating state based on detection signals from various sensors, and the required fuel injection amount TAU is determined based on the rotational speed NE and the intake air amount GA. Calculated (step S101). When the required fuel injection amount TAU is calculated, the electronic control unit 41 determines whether or not the high pressure injection condition is satisfied based on, for example, the required load calculated from the rotational speed NE and the intake air amount GA (step S102). ). When the high pressure injection condition is satisfied (step S102: YES), the fuel pressure selection valve 22 is closed (step S105), and the request is made according to the fuel injection timing and the fuel injection time corresponding to the required fuel injection amount TAU. The fuel injection amount TAU is injected under a high fuel pressure state (step S106). On the other hand, when the high pressure injection condition is not satisfied (step S102: NO), it is determined by the electronic control device 41 whether the resonance suppression condition is satisfied, and the fuel pressure is set based on the determination result. The

That is, the electronic control unit 41 first determines whether or not the required fuel injection amount TAU is equal to or greater than the selected fuel injection amount TAUT (step S103). If the required fuel injection amount TAU is less than the selected fuel injection amount TAUT (step S103: NO), the fuel pressure selection valve 22 is opened (step S107), and fuel injection corresponding to the required fuel injection amount TAU is performed. The required fuel injection amount TAU is injected under the low fuel pressure state according to the timing and the fuel injection time (step S108). On the other hand, when the required fuel injection amount TAU is equal to or greater than the selected fuel injection amount TAUT (step S103: YES), the electronic control unit 41 subsequently determines whether or not the rotational speed NE is within the selected rotational speed region NEf. (Step S104).

  When the rotational speed NE is less than the lower limit rotational speed NEL, or when the rotational speed NE exceeds the upper limit rotational speed NEH (step S104: NO), the fuel pressure selection valve 22 is similarly opened (step S107). . The required fuel injection amount TAU is injected under a low fuel pressure state in accordance with the fuel injection timing and the fuel injection time corresponding to the required fuel injection amount TAU (step S108). On the other hand, when the rotational speed NE is greater than the lower limit rotational speed NEL and equal to or lower than the upper limit rotational speed NEH (step S104: YES), the fuel pressure selection valve 22 is closed (step S105), and the required fuel injection amount TAU is reached. The requested fuel injection amount TAU is injected under a high fuel pressure state according to the corresponding fuel injection timing and fuel injection time (step S106).

  As a result, the pulsation that can occur in the low fuel pressure state can be suppressed under the high fuel pressure state, and even if the pulsation damper 23 resonates under the high fuel pressure state, the pulsation associated with the resonance is delivered. By discharging from the downstream side of the pipe 11L, pulsation amplification can be suppressed.

As described above, according to the fuel supply device for an internal combustion engine in the present embodiment, the following effects can be obtained.
(1) The rotational speed NE, which is an index of the pulsation frequency associated with fuel injection, is the selected rotational speed region NEf, and the required fuel injection amount TAU, which is an index of the amplitude of the pulsation, is greater than or equal to the selected fuel injection amount TAUT. The logical product condition with being is set as the resonance suppression condition. When the required fuel injection amount TAU is equal to or greater than the selected fuel injection amount TAUT and the rotational speed NE is in the selected rotational speed region NEf, the fuel pressure selection valve 22 is closed and the fuel pressure is set to the high injection pressure PH. The high pressure regulator 17 was opened by increasing the pressure.

  Thereby, in the engine operation state in which the pulsation is amplified by resonance in the low pressure state, the downstream side of the delivery pipe 11L can be opened, and the fuel can flow continuously in the delivery pipes 11R and 11L. Therefore, the pulsation accompanying fuel injection can be suppressed, and the resonance of the pulsation damper 23 accompanying this can be suppressed. Even if the resonance of the pulsation damper 23 is induced, a part of the pulsation accompanying the resonance can be released from the downstream side of the delivery pipe 11L to the fuel tank 13. As a result, even if the pulsation damper 23 resonates, pulsation amplification can be suppressed.

  (2) Since a threshold value is provided for the required fuel injection amount TAU, which is an index of pressure fluctuation when selecting a high fuel pressure state, it is not necessary to switch the fuel pressure state when the amplitude of pulsation due to fuel injection is small There will be no significant pressure fluctuations.

  (3) Further, the more fuel that is recirculated in the high fuel pressure state, the more fuel that is returned to the fuel tank 13 through the delivery pipes 11R and 11L in the vicinity of the combustion chamber. For this reason, as the opportunity for the high fuel pressure state increases, the fuel temperature in the fuel tank 13 generally increases. According to the above-described embodiment, compared with the case where the high fuel pressure state is selected only by the rotational speed NE, the recirculation frequency in the high fuel pressure state is reduced by the opportunity for the required fuel injection amount TAU to be less than the selected fuel injection amount TAUT. can do. Thereby, the high temperature of the fuel in the fuel tank 13 as described above can be suppressed.

(4) Since the pulsation damper 23 is provided in both of the delivery pipes 11R and 11L, the pulsation can be suppressed at a position close to the injector 12 that is a pulsation generation source. Therefore, the propagation range of the pulsation can be reduced, and the pulsation can be efficiently suppressed.

In addition, you may change the said embodiment as follows.
In the above embodiment, the pulsation damper 23 is disposed in each of the delivery pipes 11R and 11L. In addition to this, in order to suppress pulsation using a pulsation damper, the pulsation damper 23 may be provided only in one of the delivery pipes 11R and 11L, or the main pipe 15 is not limited to the delivery pipes 11R and 11L. May be provided.

  In the resonance suppression condition of the above embodiment, the selected rotational speed region NEf that is the threshold value of the rotational speed NE and the selected fuel injection amount TAUT that is the threshold value of the required fuel injection amount TAU are set independently of each other. This may be changed to change and set the threshold value of the required fuel injection amount TAU for each rotation speed. At this time, when determining the resonance suppression condition, it is first determined whether or not the rotational speed NE is in the selected rotational speed region NEf. If the rotational speed NE is in the selected rotational speed region NEf, the required fuel is determined. A configuration for determining whether or not the injection amount TAU is equal to or greater than the selected fuel injection amount TAUT is preferable.

  Further, a map in which the fuel pressure (high fuel pressure state or low fuel pressure state) is associated with the rotational speed NE and the required fuel injection amount TAU is constructed, and the rotational speed NE and the required fuel injection amount TAU are applied to the map. Accordingly, a high fuel pressure state or a low fuel pressure state may be selected. At this time, as shown in FIG. 5, when the high pressure injection condition is not satisfied (step S102: NO), first, the required fuel injection amount TAU and the rotational speed NE are applied to the map. If the fuel pressure associated with the required fuel injection amount TAU and the rotational speed NE is in the high fuel pressure state (step S109: YES), the fuel pressure selection valve 22 is closed and the required fuel injection amount TAU is in the high fuel pressure state. (Steps S105 and S106). On the other hand, when the fuel pressure associated with the required fuel injection amount TAU and the rotational speed NE is in a low fuel pressure state (step S109: NO), the fuel pressure selection valve 22 is opened and the required fuel injection amount TAU is low. The fuel is injected under the state (steps S107 and S108).

  As described above, the presence or absence of pulsation accompanying the fuel injection or the amplitude of the pulsation varies depending on the rotational speed NE of the internal combustion engine and the required fuel injection amount TAU to each injector 12. According to the above configuration, since the threshold value of the required fuel injection amount TAU for selecting the high fuel pressure state is a value for each rotational speed NE, the rotational speed NE and the required fuel injection amount TAU are selected when selecting the high fuel pressure state. It is possible to set an appropriate threshold value according to both of the above.

  In the above embodiment, the required fuel injection amount TAU is used as an index of the amplitude of pulsation accompanying fuel injection. However, the present invention is not limited to this, and for example, the required load based on the accelerator operation amount or the intake air amount GA is used. In addition, it is also possible to use a correlation value that correlates with the fuel injection amount as a parameter indicating the engine operating state.

  In the above-described embodiment, the case where the displacement amount Δx of the diaphragm 23b is equal to or greater than the reference displacement amount Δx1 as an indicator that the resonance amplitude of the pulsation damper 23 becomes excessive has been described. Not limited to this, as an indicator that the resonance amplitude of the pulsation damper 23 becomes excessive, the amplitude of the fuel pressure in the delivery pipes 11R and 11L is equal to or greater than a reference value set to stabilize the fuel injection amount. May be used.

In the above embodiment, the delivery pipes 11R and 11L are connected by the communication pipe 16, and the delivery pipes 11R and 11L are connected in series. Not limited to this, the main pipe 15 may be branched and connected to each of the delivery pipes 11R and 11L and connected in parallel. In this case, it is desirable to provide the high-pressure regulator 17 in each of the delivery pipes 11R and 11L.

In the above embodiment, the fuel supply device of the internal combustion engine is controlled by one electronic control device 41, but may be embodied by a plurality of electronic control devices.
In the above embodiment, the fuel of the internal combustion engine is not particularly limited. However, the present invention is flexible in that it can use a gasoline internal combustion engine, a diesel internal combustion engine, or a fuel in which alcohol fuel and gasoline fuel are mixed. The present invention can be applied to an internal combustion engine for a fuel vehicle (FFV).

  In the internal combustion engine of the above-described embodiment, the fuel supply method to each cylinder is not particularly limited. However, the present invention is not limited to the port injection type in which fuel is injected from the injector 12 into the intake port of each cylinder. The present invention can be applied to an in-cylinder internal combustion engine that directly injects fuel.

  In the above embodiment, the present invention has been embodied in a V-type internal combustion engine having two cylinder arrangements. However, the present invention is not limited to this, and any internal combustion engine in which a delivery pipe is disposed may be used. The same operation and effect can be obtained even if the invention is embodied in an engine or an in-line internal combustion engine having one cylinder arrangement.

1 is a schematic configuration diagram showing a fuel supply device for an internal combustion engine according to an embodiment of the present invention. The schematic block diagram of the pulsation damper in one Embodiment of this invention. The graph which shows an example of the displacement amount of the diaphragm with respect to the rotational speed in this embodiment. The flowchart for demonstrating the control routine of the fuel-injection control in this invention. The flowchart for demonstrating the control routine of the fuel-injection control in the example of a change.

Explanation of symbols

  GA: intake air amount, NE: rotational speed, NEf: selected rotational speed region, NEH: upper limit rotational speed, NEL: lower limit rotational speed, PH: high injection pressure, PL: low injection pressure, TAU ... required fuel injection amount, TAUT ... selected fuel injection amount, Δx ... displacement amount, Δx1 ... reference displacement amount, 11P ... branch port, 11R, 11L ... delivery pipe, 12 ... injector, 13 ... fuel tank, 14 ... fuel pump, 15 ... main piping, 16 ... Communication pipe, 17 ... High pressure regulator, 18 ... High pressure return pipe, 19 ... Low pressure regulator, 21 ... Low pressure return pipe, 22 ... Fuel pressure selection valve, 23 ... Pulsation damper, 23a ... Introduction hole, 23b ... Diaphragm, 23c ... Spring, 24 ... sealing material, 25 ... exhaust pipe, 26 ... three-way catalyst, 41 ... electronic control unit, 42 ... rotational speed sensor, 43 ... air flow meter 44. Oxygen concentration sensor.

Claims (6)

A supply passage comprising a pressure feed passage through which fuel is pumped from a fuel tank and a delivery pipe connected to the pressure feed passage and provided with an injector;
A return passage connected to the delivery pipe for returning excess fuel from the delivery pipe to the fuel tank;
A low fuel pressure state in which the circulation of the reflux passage is prohibited and the pressure in the supply passage is the first pressure, and a second pressure in which the circulation of the reflux passage is permitted and the pressure in the supply passage is higher than the first pressure A fuel supply device for an internal combustion engine comprising a fuel pressure selection means for selecting a high fuel pressure state to be
A pulsation damper provided in the supply passage for suppressing fuel pulsation generated by fuel injection of the injector;
A fuel supply apparatus for an internal combustion engine, wherein the fuel pressure selection means selects the high fuel pressure state in an engine operating state in which the pulsation damper resonates in the low fuel pressure state. 2. The fuel supply device for an internal combustion engine according to claim 1, wherein the fuel pressure selection unit selects the high fuel pressure state at a selected rotational speed that is a rotational speed at which the pulsation damper resonates in the low fuel pressure state. . The fuel pressure selecting means selects the high fuel pressure state on the condition that the load required for the internal combustion engine in the low fuel pressure state is equal to or greater than a threshold value that makes the resonance amplitude of the pulsation damper excessive. The fuel supply device for an internal combustion engine according to claim 2. The fuel pressure selecting means selects the high fuel pressure state on condition that the fuel injection amount required for the injector in the low fuel pressure state is equal to or greater than a threshold value that makes the resonance amplitude of the pulsation damper excessive. The fuel supply device for an internal combustion engine according to claim 2. The fuel supply apparatus for an internal combustion engine according to claim 3 or 4, wherein the threshold value is a value for each selected rotational speed. 6. The fuel supply device for an internal combustion engine according to claim 1, wherein the pulsation damper is provided in the delivery pipe.

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