JP2007303372A - Fuel supply system of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel supply system of an internal combustion engine in which an electromagnetic valve or the like need not be provided, requests for both high power and low fuel consumption can be satisfied, and further a simple structure and high reliability can be realized. <P>SOLUTION: The fuel supply system is equipped with pump controllers 59, 60 which control an operation of a fuel pump 21 so as to supply a required injection quantity of fuel to an injector 31; a low-pressure regulator 71 including a regulated pressure port 71a connected with a fuel pathway P1 at a supply side and a return port 71b communicating with a fuel reservoir chamber 11 at a pump side; a high-pressure regulator 72 including a regulated pressure port 72a connected with the fuel pathway P1 at the supply side, and a return port 72b communicating with a fuel reservoir room 11 at the pump side; transfer pumps 76, 77 which transfers fuel from other fuel reservoir chambers 12, 13 to the reservoir chamber 11 depending on a fuel flow returning from the port 71b to the reservoir room 11; and an orifice 81 which is located in a fuel pathway P2 at a return side and limits a fuel flow returning to the reservoir room 11 depending on an anteroposterior pressure difference. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel supply system for an internal combustion engine that supplies fuel stored in a plurality of fuel storage chambers in a fuel tank to a fuel injection device (injector) using a fuel pump, and particularly to a jet pump for fuel transfer in a vertical fuel tank. And a fuel supply system for an internal combustion engine that performs high-pressure / low-pressure switching of a supplied fuel pressure (hereinafter referred to as fuel pressure) in accordance with an operating state in order to improve fuel injection accuracy.

  In the fuel supply system that supplies the fuel stored in the fuel tank to the injector side, the fuel pump is installed in a so-called saddle-shaped fuel tank (a fuel tank in which a propeller shaft or the like is formed on the lower surface side). Some pump-side fuel storage chambers transfer fuel from other fuel storage chambers. For example, the return passage of the fuel discharged from the pump is branched so that the fuel is transferred through the communication passage by the amount of fuel consumed by the engine, and the fuel according to the return flow rate in the branch passage. A jet pump that transfers fuel from other fuel storage chambers is provided in the pump side fuel storage chamber, and an electromagnetic valve is provided in the branch passage upstream of the jet pump to control the transfer amount from the controller side to the optimum amount. What is made to do is known (for example, refer patent document 1).

  Further, in an internal combustion engine of an electronic control fuel injection system, linearity is required for the relationship between the fuel injection time (injection drive pulse width) and the fuel injection amount. Since it is difficult to accurately control the injection amount in a low load region where the required injection amount is small, such as when idling, the fuel pressure is regulated by a pressure regulator that uses the intake pressure downstream of the throttle valve as the back pressure. The injection drive pulse is corrected based on the detected value of the fuel pressure, and the control accuracy is improved by lowering the fuel pressure according to the intake air at low load, and the throttle valve opening is increased and the intake pressure is relatively high at high load. Some have made the fuel pressure higher than when the load is low, so that the required injection amount with a high output can be accommodated (see, for example, Patent Document 2).

In addition, the range in which the linearity between the injector injection time and the required injection amount can be obtained for high and low fuel pressures is grasped in advance, and the high-pressure pressure regulator is bypassed in the low load region where the linearity decreases at high fuel pressure. There is a type that adjusts the fuel pressure by a low-pressure pressure regulator to widen the dynamic range of the injection amount control and ensure the accuracy of the fuel injection control (see, for example, Patent Document 3).
JP 2004-218571 A Japanese Utility Model Publication No. 63-22360 Japanese Patent Laid-Open No. 10-274077

  However, in the fuel supply system of the conventional internal combustion engine, the return path of the fuel is branched, and not only a jet pump but also an electromagnetic valve is provided in the branch path to switch the operation of the jet pump. Due to the necessity of the valve and its control means (hereinafter referred to as a solenoid valve or the like), there is a problem that the configuration of the apparatus is complicated and the reliability is lowered.

  In addition, in the conventional internal combustion engine fuel supply system that constantly introduces the intake pressure to the back pressure of the pressure regulator, there is a problem that the fuel vapor is generated at a high temperature and the startability is deteriorated. There has been a problem that the atmospheric pressure is led to the back pressure chamber of the regulator, but there is a problem that the configuration of the apparatus is complicated and the reliability is lowered due to the necessity of a back pressure switching electromagnetic valve or the like.

  Furthermore, in a conventional internal combustion engine fuel supply system that forms a passage that bypasses the high-pressure pressure regulator in a low load region, a passage that bypasses the high-pressure pressure regulator is formed, or an electromagnetic valve for opening and closing the passage is provided. Again, there is a problem that the necessity of a solenoid valve or the like leads to a complicated apparatus configuration and a decrease in reliability.

  In addition to these problems, when the absolute pressure control using the atmospheric pressure as the back pressure is adopted, the differential pressure received by the plunger of the injector also changes. Therefore, if the fuel pressure is made constant, the driving load of the injector increases depending on the load. As a result, the needle valve opening characteristic of the injector during a minute energization time is deteriorated as the injector driving load is increased, and the combustion controllability at the time of low load of the internal combustion engine is deteriorated. Especially in the case of idling where the required injection amount is very low, etc., in the case of a high-power engine in which the injection hole area of the injector is set to be relatively large in order to ensure a sufficient fuel injection amount corresponding to the required injection amount at a high rotational load In addition, the drive pulse width becomes too narrow and the error of the injection amount becomes large, which makes it difficult to satisfy both the recent demand for higher output and lower fuel consumption.

  Therefore, the present invention provides a highly reliable fuel supply system for an internal combustion engine with a simple configuration that does not require a solenoid valve or the like and can satisfy both demands for high output and low fuel consumption.

In order to solve the above problems, the present invention provides (1) a fuel supply system for an internal combustion engine that supplies fuel stored in a plurality of fuel storage chambers in a fuel tank to a fuel injection device with a fuel pump,
Pump control means for controlling the operation of the fuel pump so as to supply a required amount of fuel to the fuel injector; and a first fuel passage connected to a fuel passage on the supply side from the fuel pump to the fuel injector. A low-pressure pressure regulator having a first return port communicating with an adjustment pressure port and a pump-side fuel storage chamber in which the fuel pump is installed, and having a predetermined low-pressure adjustment value set with atmospheric pressure as a back pressure; And a second return pressure port connected to the fuel passage on the supply side and a second return port connected to the pump side fuel storage chamber, and a predetermined pressure higher than the low pressure pressure regulator using atmospheric pressure as a back pressure. A high-pressure pressure regulator in which a pressure adjustment value on the high-pressure side is set, and the flow rate of fuel returning from the first return port to the pump-side fuel storage chamber A transfer pump for transferring fuel from another fuel storage chamber to the pump-side fuel storage chamber, and a return-side fuel passage from the first return port to the pump-side fuel storage chamber; A throttle element that restricts the flow rate of fuel returning from the port to the pump-side fuel storage chamber according to the front-rear differential pressure, and when the required fuel injection amount required for injection by the fuel injection device is less than a predetermined value The pump control means reduces the discharge amount of the fuel pump so as to suppress the flow rate of the fuel returning from the low pressure pressure regulator and the high pressure pressure regulator to the pump side fuel storage chamber to a predetermined amount or less. The pressure in the fuel passage is adjusted to the pressure adjustment value on the low pressure side.

  With this configuration, the flow rate of the low-pressure and high-pressure pressure regulators is appropriately suppressed only by adjusting the discharge amount of the fuel pump, and the supply fuel pressure is switched between the high-pressure side and the low-pressure side. Therefore, if the fuel injection drive pulse for driving the fuel injection device is switched to a different pulse width depending on whether the fuel pressure control mode is the high pressure side or the low pressure side, this is the case of a high output engine having a relatively large injection hole area. However, the drive pulse width becomes too narrow when idling, etc., where the required injection amount is very small, and the injection amount error becomes large, or a sufficient fuel injection amount corresponding to the required injection amount cannot be secured at high rotational loads. Therefore, it is possible to satisfy both the recent demand for higher output and lower fuel consumption. In addition, there is no need to provide a dedicated return pipe to return the surplus fuel to the pump side fuel storage chamber, and the surplus fuel returns from the pressure regulator to the fuel tank without reaching the engine side. The temperature can be kept low.

  In the fuel supply system of the internal combustion engine having the configuration of (1) above, (2) a fuel consumption calculated based on a fuel injection time in the fuel injection device and a pressure in the fuel passage on the supply side; And a regulator passage for observing the flow rate of fuel returning from the low-pressure pressure regulator and the high-pressure pressure regulator to the pump-side fuel storage chamber based on the discharge amount of the fuel pump calculated based on the energization state of the fuel pump It is preferable to provide a flow rate calculation means.

  With this configuration, the regulator passage flow rate can be properly maintained, and low power consumption and low fuel consumption can be achieved.

  In the fuel supply system of the internal combustion engine having the configuration (1) or further (2), it is preferable that (3) a detection means for detecting the driving state of the fuel pump is provided.

  In this case, it is preferable that (4) the pump control means further includes a pump drive circuit for driving the fuel pump in accordance with a target fuel discharge amount of the fuel pump.

  According to the present invention, the flow rate of the low-pressure and high-pressure pressure regulators is appropriately suppressed only by adjusting the discharge amount of the fuel pump, and the supply fuel pressure is switched between the high-pressure side and the low-pressure side. If the fuel injection drive pulse for driving the system is switched to a different pulse width depending on whether the fuel pressure control mode is the high pressure side or the low pressure side, even a high power engine with a relatively large injection hole area is required. The fuel injection drive pulse width becomes too narrow at idling, etc. when the injection amount is very small, and the injection amount error becomes large, or a sufficient fuel injection amount corresponding to the required injection amount cannot be secured at high rotational load. This makes it possible to satisfy both the recent demand for higher output and lower fuel consumption.

  Embodiments of the present invention will be described below with reference to the drawings.

  1 to 3 are views showing a fuel supply system for an internal combustion engine according to an embodiment of the present invention, and FIG. 1 shows a schematic configuration thereof.

  As shown in FIG. 1, the fuel supply system for an internal combustion engine according to the present embodiment uses fuel L stored in a plurality of fuel storage chambers 11, 12, 13 in a fuel tank 10 to each injector 31 (fuel injection) of the engine 1. The fuel pump 21 is supplied to the apparatus.

  The engine 1 is a multi-cylinder internal combustion engine mounted on an automobile. A combustion chamber 3 partitioned by a piston 2 is formed in each cylinder 1a of an engine block (not shown in detail), and an intake valve 4 The exhaust valve 5 is equipped to be opened at a predetermined timing, and a spark plug 6 is disposed so as to be exposed in the combustion chamber 3. A throttle valve 8 is provided in the intake pipe 7.

  The plurality of injectors 31 corresponding to the plurality of cylinders 1a of the engine 1 are connected to delivery pipes 32 that supply fuel to these, and the fuel (for example, gasoline) discharged from the fuel pump 21 is supplied to the fuel passage P1 on the supply side. To the delivery pipe 32. The fuel pump 21 is driven by, for example, a DC motor 21m (see FIG. 2), and can control the rotation speed and the discharge amount proportional to the voltage control.

  Each of the injectors 31 is disposed in the vicinity of the corresponding combustion chamber 3, and the operation of the injector 31 and the spark plug 6 is controlled by an engine control computer (hereinafter referred to as ECC) 50, and the fuel injection time and ignition timing are controlled. .

  The ECC 50 includes a CPU (Central Processing Unit) 50a, a ROM (Read Only Memory) 50b, a RAM (Random Access Memory) 50c, and a B-RAM (Back-up RAM) 50d as a backup memory using a battery. An input interface circuit and an output interface circuit (not shown) are included. The input interface circuit of the ECC 50 is connected to an air flow meter 41, a rotation speed sensor 42, a throttle sensor 43, and a sensor group (not shown) such as an oxygen sensor, a cylinder discrimination sensor, an intake air temperature sensor, and a water temperature sensor. Sensor information from the sensor group is taken into the ECC 50. The output interface circuit of the ECC 50 is connected to an injector 31, an igniter 36 that drives each spark plug 6 via a distributor (not shown), a pump drive circuit 60 that will be described later, and the like. Note that the power of the ECC 50 is supplied from the battery 38 via the key switch 37.

  The CPU 50a of the ECC 50 mainly uses the sensor information acquired from the input interface circuit, preset setting value information, etc. while exchanging data between the RAM 50c and the B-RAM 50d according to the control program stored in the ROM 50b. On the basis of this, predetermined arithmetic processing is executed, and a control signal is output from the output interface circuit according to the result, thereby executing electronic control processing of the engine 1 and performing pump control processing described later. It is supposed to be.

  A known relief valve type low-pressure pressure regulator 71 and high-pressure pressure regulator 72 are connected to the fuel passage P 1 on the supply side from the fuel pump 21 to the delivery pipe 32.

  The low-pressure pressure regulator 71 communicates with the first adjustment pressure port 71a connected to the fuel passage P1 on the supply side from the fuel pump 21 to the injector 31 and the pump-side fuel storage chamber 11 in which the fuel pump 21 is installed. 1 return port 71b, which is set to a predetermined low pressure adjustment value, for example, 324 kPa, with atmospheric pressure as the back pressure. Further, the high pressure regulator 72 has a second adjustment pressure port 72a connected to the fuel passage P1 on the supply side, and a second return port 72b communicating with the pump side fuel storage chamber 11, and has an atmospheric pressure. Is set to a predetermined high pressure side pressure adjustment value higher than that of the low pressure regulator 71, for example, 400 kPa.

  In the return-side fuel passage P2 returning from the first return port 71b of the low-pressure pressure regulator 71 to the pump-side fuel storage chamber 11, the pump-side fuel storage chamber 11 according to the fuel flow rate in the return-side fuel passage P2. In addition, known jet pumps 76 and 77 (transfer pumps) as described in Patent Document 1 for transferring fuel from other fuel storage chambers 12 and 13 are provided.

  Further, the flow rate of the fuel returning from the first return port 71b to the pump-side fuel storage chamber 11 is limited in the return-side fuel passage P2 in accordance with the front-rear differential pressure (the differential pressure between the upstream side and the downstream side). An orifice 81 is provided. The orifice 81 serves as a throttle element that activates the low-pressure pressure regulator 71 until a predetermined flow rate is reached.

  As shown in FIG. 2, the ECC 50 functionally includes a control value calculation unit that calculates a control value for electronic control of the engine 1, for example, a required fuel injection time, ignition timing, throttle opening, load, and the like. 51, an injection drive pulse output unit 52 that outputs an injection drive pulse to the injector 31 based on a calculation result in the control value calculation unit 51, and an ignition signal output unit 53 that outputs an ignition signal to the spark plug 6. It has a program and a working memory corresponding to these functional units.

  The ECC 50 further calculates a fuel consumption amount Fc required for each predetermined cycle based on the required fuel injection time calculated by the control value calculation unit 51 and the pressure in the fuel passage P1 on the supply side. 54, an energization state detection unit 55 (detection means) for detecting the energization state of the fuel pump 21 by a drive voltage (hereinafter also referred to as a pump voltage) or a drive current (hereinafter also referred to as a pump current) of the DC motor 21m; A fuel discharge amount calculation unit 56 that calculates a discharge amount of fuel discharged from the fuel pump 21 based on detection information of the energization state detection unit 55, and a discharge amount of the fuel pump 21 calculated by the fuel discharge amount calculation unit 56 Based on the fuel injection time calculated by the control value calculation unit 51, the pump-side fuel storage chamber 11 is transferred from the low pressure regulator 71 and the high pressure regulator 72. A P / R passage flow rate calculation unit 57 (regulator passage flow rate calculation means) for observing the flow rate of fuel, and a required fuel consumption amount Fc and P / R passage flow rate calculation unit 57 calculated by the fuel consumption amount calculation unit 54. The target fuel discharge amount calculation unit 58 that calculates the target fuel discharge amount Fp based on the passage flow rate calculated in step 1 and a PWM (pulse width modulation) type pump drive pulse signal corresponding to the target fuel discharge amount Fp of the fuel pump 21 And a pump control unit 59 that outputs a relay switching signal for starting driving of the fuel pump 21 when the starter signal is ON and when the engine rotation signal is continuously input for a predetermined time. Here, the pump control unit 59 controls the rotational speed of the fuel pump 21 by controlling the energization current so as to supply the required injection amount of fuel to the injector 31 together with the pump drive circuit 60 connected to the positive terminal of the battery 38. The pump control means is configured.

  Although the pump drive circuit 60 is shown in a simplified manner in FIG. 2, the energization of the motor coil of the DC motor 21m of the fuel pump 21 can be switched ON / OFF in accordance with the ON / OFF switching signal from the pump control unit 59. From the MOS-FET output section of the pump control section 59 supplied to the gate current flowing between the drain connected to the motor coil of the direct current motor 21m of the fuel pump 21 and the ground-side source. In accordance with the PWM signal, the MOS-FET type transistor 62 that variably controls the energization current to the coil of the DC motor 21m of the fuel pump 21, and the generated voltage of the DC motor coil at the time of switching the power ON / OFF Clamp diode 63 and capacitor 64 having functions such as clamping and regulating the current direction The has.

  The pump control unit 59 suppresses the flow rate of the fuel returning from the low pressure pressure regulator 71 and the high pressure pressure regulator 72 to the pump side fuel storage chamber 11 to a predetermined amount or less when the required fuel injection amount Fc required for injection is less than a predetermined value. Thus, the discharge amount of the fuel pump 21 can be reduced, and the pressure in the fuel passage P1 on the supply side can be adjusted to the pressure adjustment value on the low pressure side by the low pressure regulator 71 (details will be described later).

  Next, the operation will be described.

  FIG. 3 is a flowchart showing a schematic flow of a control program executed in the fuel supply system of the internal combustion engine of the present embodiment configured as described above. This program is set when the starter signal is ON and the engine rotation signal is predetermined. After the time is continuously input, it is executed every predetermined time. When the starter signal is ON and the engine rotation signal is continuously input for a predetermined time, first, a relay switching signal for starting driving the DC motor 21m of the fuel pump 21 is sent from the pump control unit 59 to the drive relay switch 61. And the fuel pump 21 starts to rotate.

  As shown in FIG. 3, first, various sensor values and calculated values such as a fuel pump voltage, a pump current, and a required fuel injection amount (“INJ injection amount” in FIG. 3) are acquired every predetermined time ( Step S1). At this time, the injection drive pulse is output from the injection drive pulse output unit 52 to the injector 31 and the ignition signal is output from the ignition signal output unit 53 to the igniter 36 based on the calculation result of the control value calculation unit 51. It is output.

  Next, based on the required fuel injection time calculated by the control value calculation unit 51 and the pressure control mode in the fuel passage P1 on the supply side, the fuel consumption Fc required by the fuel consumption calculation unit 54 is calculated at predetermined intervals. Is calculated. The fuel discharge amount calculation unit 56 calculates the discharge amount of the fuel discharged from the fuel pump 21 based on the detection information of the energization state detection unit 55, and the fuel pump 21 calculated by the fuel discharge amount calculation unit 56. The flow rate of the fuel returning from the low-pressure pressure regulator 71 and the high-pressure pressure regulator 72 to the pump-side fuel storage chamber 11 in the P / R passage flow rate calculation unit 57 based on the discharge amount of the fuel and the fuel injection time calculated by the control value calculation unit 51 The target fuel discharge amount calculation unit 58 is based on the fuel consumption amount Fc corresponding to the required fuel amount calculated by the fuel consumption amount calculation unit 54 and the passage flow rate calculated by the P / R passage flow rate calculation unit 57. Thus, the target fuel discharge amount Fp is calculated. That is, the pump speed corresponding to the target fuel discharge amount Fp is calculated (step S2).

  Next, it is determined whether the fuel pressure control mode is the low pressure side or the high pressure side depending on whether the value of the required fuel injection amount Fc is equal to or greater than a predetermined value (step S3). This process ends here.

  On the other hand, if the determination result in step S3 is the low pressure side, then, the discharge flow rate from the first return port 71b of the low pressure pressure regulator 71, that is, the flow rate through the orifice 81 is less than the predetermined flow rate. The pump rotation speed is set, the flow rates of the pressure regulators 71 and 72 are suppressed (step S4), and the pulse width of the injection drive pulse signal from the injection drive pulse output unit 52 to the injector 31 is required. The injection amount Fc is corrected to a value corresponding to the fuel pressure after switching (pressure adjustment value on the low pressure side) (step S5).

  The operation when such a series of processing is performed will be described more specifically.

  When the required fuel injection amount Fc is relatively small and the discharge amount of the fuel pump 21 is small, the pressure of fuel from the fuel pump 21 to the high-pressure pressure regulator 72 and the orifice 81 is adjusted by the high-pressure pressure regulator 72. The pressure adjustment value on the low-pressure side, which is the set pressure of the low-pressure pressure regulator 71, is reached early after the start of the operation of the fuel pump 21, and the fuel relieved by the low-pressure pressure regulator 71 is transferred to the first return port. It is discharged from 71b and flows from the first return port 71b to the return side fuel passage P2 to the pump side fuel storage chamber 11. At this time, the flow rate of the discharged fuel is limited to a flow rate corresponding to the differential pressure across the orifice 81 on the downstream side (fuel tank side), but the orifice 81 has a low pressure until the predetermined flow rate is reached as described above. The regulator 71 is operated.

  When the required fuel injection amount Fc is large and the discharge amount of the fuel pump 21 is increased, the amount of fuel discharged from the first return port 71b is increased and the differential pressure across the orifice 81 is increased. When the flow rate exceeds the predetermined flow rate, the pressure in the first return port 71b, which is the pressure on the upstream (front) side of the orifice 81, reaches the set pressure of the low pressure regulator 71, and the pressure adjustment function of the low pressure regulator 71 is lost. Furthermore, the pressure of the first adjustment pressure port 71a connected to the fuel passage P1 on the supply side increases as the discharge amount of the fuel pump 21 increases.

  When the fuel pressure in the fuel passage P1 on the supply side reaches the pressure adjustment value on the high-pressure side, the high-pressure pressure regulator 72 is activated, and excess supply fuel is supplied from the second return port 72b to the pump-side fuel storage chamber 11. Come back.

  Between the time when the pressure adjustment function of the low pressure regulator 71 is lost and the time when the high pressure regulator 72 is activated, the differential pressure across the orifice 81 increases from the vicinity of the low pressure adjustment value to the vicinity of the high pressure adjustment value, Along with this, the flow rate of the return side fuel passage P2 increases. At this time, the amount of fuel transferred by the jet pumps 76 and 77 also increases. In the operating state of the high-pressure pressure regulator 72, a larger amount of fuel is transferred from the other fuel storage chambers 12 and 13 to the pump-side fuel storage chamber 11 by the jet pumps 76 and 77 than when the low-pressure pressure regulator 71 is operating. .

  In this way, the fuel passage P1 in the supply side passage is changed to the set pressure of the low-pressure pressure regulator 71 and the set pressure of the high-pressure pressure regulator 72 only by changing the discharge amount Fp of the fuel pump 21 according to the required fuel injection amount. It is possible to switch to

  Here, the discharge amount Fp of the fuel pump is the return flow rate Fr1 from the low-pressure pressure regulator 71 set in consideration of the required fuel consumption amount Fc by the injector 31 and various fluctuation factors in the operating range of the low-pressure pressure regulator 71. (Fp = Fc + Fr1), and the return flow rate Fr1 is preferably less than the predetermined flow rate, for example, 18 to 20 liters per hour (18-20 (litter / hour)).

  On the other hand, in the operating range of the high-pressure pressure regulator 72, the discharge amount Fp of the fuel pump is the sum of the fuel consumption Fc by the injector, the return flow rate Fr1 from the low-pressure pressure regulator 71, and the return flow rate Fr2 from the high-pressure pressure regulator 72 ( Fp = Fc + Fr1 + Fr2). In this case, the return flow rate Fr1 from the low-pressure pressure regulator 71 is higher than the predetermined flow rate, for example, 24 liters per hour (24 (litter / hour)), and the initial flow rate from the high-pressure pressure regulator 72 The return flow rate Fr2 is preferably less than 40 liters per hour (Fr1 <24 (litter / hour)), for example.

  When the pump discharge amount Fp corresponding to the required fuel injection amount Fc as described above is set as a target value, the target rotational speed Nfp of the DC motor 21m of the fuel pump 21 is set by multiplying the target value Fp by a predetermined coefficient k. (Nfp = k · Fp) and, for example, the voltage between terminals of the DC motor 21m of the fuel pump 21 based on the battery voltage value or the like (battery voltage monitor information held by the ECC 50 and circuit specifications of the fuel pump drive system) The pump current Vfp is detected by the energization state detection unit 55 connected in parallel to the DC motor 21m of the fuel pump 21, and the PWM drive pulse generated by the pump control unit 59 is input to the gate of the transistor 62. Thus, the pump current is controlled by PWM drive so that the target fuel discharge amount Fp is obtained.

  On the other hand, the control value calculation unit 51 in the ECC 50 calculates the basic fuel injection time based on, for example, the intake air amount detected by the air flow meter 41 by a known method, and based on various sensor information based on this basic injection amount. A corrected injection amount (amount of fuel required to be injected) Fc is calculated, and a fuel injection drive pulse corresponding to the required injection amount Fc and the fuel pressure in the fuel passage on the supply side is an injection drive pulse. It is output from the output unit to each injector 31.

  Specifically, if the required injection amount Fc is small and the target fuel discharge amount Fp of the fuel pump 21 is small, the low-pressure pressure regulator 71 operates, and the pressure of the fuel in the fuel passage P1 on the supply side is the pressure adjustment value on the low-pressure side. However, based on the injection characteristics of the injector 31, a fuel injection drive pulse having a relatively long time (wide pulse width) is generated compared to when the fuel pressure is the pressure adjustment value on the high pressure side. . Further, if the required fuel injection amount is large and the target fuel discharge amount Fp of the fuel pump 21 is large, the high pressure regulator 72 is activated when the pressure of the fuel in the upstream fuel passage reaches the high pressure adjustment value by the orifice 81. Therefore, based on the injection characteristic of the injector 31, a fuel injection drive pulse having a relatively short time (narrow pulse width) is generated as compared with the case where the fuel pressure is the pressure adjustment value on the low pressure side. .

  As described above, in the present embodiment, the control mode of the fuel pressure is determined according to the current discharge amount (pump rotation speed) of the fuel pump 21 and the required fuel injection amount (load), and the pump discharge amount Fp is set. By simply controlling to increase or decrease, the flow rate of the pressure regulators 71 and 72 is appropriately suppressed to switch the supplied fuel pressure between the high pressure side and the low pressure side, and the fuel injection control pulse for driving the injector 31 is high in the fuel pressure control mode. The fuel injection amount is controlled while switching to a different pulse width depending on whether the side or the low pressure side. Therefore, even if the engine 1 is a high-power engine having a relatively large injection hole area of the injector 31, the drive pulse width becomes too narrow at idling or the like when the required fuel injection amount is very small, and the injection amount error becomes large. And the problem that a sufficient fuel injection amount corresponding to the required injection amount cannot be ensured at the time of high rotational load can be solved, and both the recent demand for higher output and lower fuel consumption can be achieved. . Moreover, since power consumption can be reduced, it can contribute to low fuel consumption and low noise.

  Furthermore, in the present embodiment, the pump side from the low-pressure pressure regulator 71 and the high-pressure pressure regulator 72 is based on the required fuel consumption and the discharge amount Fp of the fuel pump 21 calculated based on the energization state of the fuel pump. Since the regulator passage flow rate calculation unit 57 for observing the flow rate of fuel returning to the fuel storage chamber 11 is provided, the regulator passage flow rate can be properly maintained, and low power consumption and fuel consumption can be achieved.

  In addition, since the fuel pump 21 is driven by the DC motor 21m and includes an energization state detection unit 55 that detects the energization state of the fuel pump 21 based on the drive voltage or drive current of the DC motor 21m. The discharge amount can be accurately grasped from the energized state, and the discharge amount of the fuel pump 21 can be accurately controlled. In addition, the pump controller 59 outputs a PWM-type pump drive pulse signal corresponding to the target fuel discharge amount Fp of the fuel pump 21, and current control is performed on the DC motor 21m that drives the fuel pump 21 in accordance with the pump drive pulse signal. Since the pump drive circuit 60 is provided, the control means of the fuel pump 21 can be made simple and low cost by the PWM drive system, and the discharge amount of the fuel pump 21 can be optimally controlled at all times.

  As described above, the present invention has the effect of being able to satisfy both the recent demands for higher output and lower fuel consumption. Fuel stored in a plurality of fuel storage chambers in a fuel tank can be obtained. A fuel supply system for an internal combustion engine that supplies fuel to an injector with a fuel pump, particularly an internal combustion engine that employs a jet pump to transfer fuel in a vertical fuel tank and switches fuel pressure according to operating conditions to improve fuel injection accuracy It is useful for the entire engine fuel supply system.

1 is a block diagram showing a schematic configuration of a fuel supply system for an internal combustion engine according to a first embodiment of the present invention. It is a principal part schematic block diagram of the control system of the fuel supply system which concerns on the 1st Embodiment of this invention. It is the flowchart which shows the flow of the control program of the fuel supply system of the internal combustion engine which concerns on the 1st Embodiment of this invention.

Explanation of symbols

11 Pump-side fuel storage chamber 12, 13 Fuel storage chamber (other fuel storage chamber)
21 Fuel pump 21m DC motor 31 Injector (fuel injection device)
32 Delivery pipe 36 Igniter 41 Air flow meter 42 Speed sensor 43 Throttle sensor 50 ECC (Engine control computer)
51 Control Value Calculation Unit 52 Injection Drive Pulse Output Unit 53 Ignition Signal Output Unit 54 Fuel Consumption Calculation Unit 55 Energized State Detection Unit (Detection Unit)
56 fuel discharge amount calculation unit 57 P / R passage flow rate calculation unit 58 target fuel discharge amount calculation unit 59 pump control unit (pump control means)
60 Pump drive circuit (pump control means)
61 Drive relay switch 62 Transistor (MOS-FET)
63 Clamp diode 71 Low pressure pressure regulator 71a First adjustment pressure port 71b First return port 72 High pressure pressure regulator 72a Second adjustment pressure port 72b Second return port 76, 77 Jet pump (transfer pump)
81 Orifice (throttle element)
P1 Fuel path on the supply side P2 Fuel path on the return side

Claims (4)

A fuel supply system for an internal combustion engine that supplies fuel stored in a plurality of fuel storage chambers in a fuel tank to a fuel injection device with a fuel pump,
Pump control means for controlling the operation of the fuel pump to supply the fuel injection device with a required injection amount of fuel;
A first adjustment pressure port connected to a fuel passage on the supply side from the fuel pump to the fuel injection device, and a first return port communicating with a pump side fuel storage chamber in which the fuel pump is installed; A low pressure regulator in which a pressure adjustment value on a predetermined low pressure side is set with the atmospheric pressure as a back pressure;
A second high pressure port connected to the fuel passage on the supply side and a second return port communicating with the pump side fuel storage chamber; A high pressure regulator with a pressure adjustment value on the side,
A transfer pump for transferring fuel from another fuel storage chamber to the pump-side fuel storage chamber according to the flow rate of fuel returning from the first return port to the pump-side fuel storage chamber;
It is installed in a fuel passage on the return side from the first return port to the pump-side fuel storage chamber, and restricts the flow rate of fuel returning from the first return port to the pump-side fuel storage chamber according to the front-rear differential pressure. And an aperture element
When the required fuel injection amount required to be injected by the fuel injection device is less than a predetermined value, the flow rate of fuel returning from the low pressure pressure regulator and the high pressure pressure regulator to the pump side fuel storage chamber is suppressed to a predetermined amount or less. A fuel supply system for an internal combustion engine, wherein the discharge amount of the fuel pump is decreased by the pump control means to adjust the pressure in the fuel passage on the supply side to the pressure adjustment value on the low pressure side.   A fuel consumption calculated based on a fuel injection time in the fuel injection device and a pressure in the fuel passage on the supply side, and a discharge amount of the fuel pump calculated based on an energization state of the fuel pump. 2. The fuel for an internal combustion engine according to claim 1, further comprising regulator passage flow rate calculation means for observing a flow rate of the fuel returning from the low pressure pressure regulator and the high pressure pressure regulator to the pump side fuel storage chamber. Supply system.   3. The fuel supply system for an internal combustion engine according to claim 1, further comprising detection means for detecting a driving state of the fuel pump.   4. The fuel supply system for an internal combustion engine according to claim 3, wherein the pump control means includes a pump drive circuit that drives the fuel pump in accordance with a target fuel discharge amount of the fuel pump.

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