JP2006132439A - Common rail type fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a common rail type fuel injection device capable of preventing a supply pump from being failed by iron powder mixed in a return fuel from a boosting mechanism. <P>SOLUTION: The fuel pressurized by the supply pump 7 and stored in a common rail 10 is jetted into an engine cylinder by a fuel injection mechanism 31. The fuel supplied from the common rail 10 to the fuel injection mechanism 31 is arbitrarily pressurized by the boosting mechanism 51. On the other hand, a return fuel discharged by the operation of the boosting mechanism 51 is returned to the inlet side of the supply pump 7 via a return passage 59. Filters 64 are installed on the downstream sides of an orifice 61 and a check valve 62 installed in the return passage 59 to suppress pressure fluctuation. The return fuel is filtrated by the filters 64 after the pressure pulsation is suppressed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a common rail type fuel injection device, and more particularly to a pressure increase type common rail type fuel injection device capable of controlling a fuel injection rate waveform by pressurizing high pressure fuel supplied from a common rail by a pressure increasing mechanism.

  A common rail type fuel injection device that accumulates high pressure fuel pumped from a pressure pump in a common rail and injects it into a cylinder of the engine from a fuel injection valve at a predetermined time according to the operating state of the engine has been put into practical use. Since this type of fuel injection device can control the injection pressure and the injection timing independently, it is becoming the mainstream of diesel engines for vehicles. For example, since the injection rate waveform is almost rectangular, the initial injection amount is large, etc. There was room for improvement in terms of reduction and combustion noise reduction.

  Therefore, a pressure-increase type common rail fuel injection device has been developed as a fuel injection device capable of controlling the injection rate waveform (see, for example, Patent Document 1). In this type of fuel injection device, the fuel supplied from the common rail is pressurized at any time by the pressure-increasing piston of the pressure-increasing mechanism, thereby making it possible to control the fuel injection rate waveform. The booster piston is formed by integrally forming a large diameter part and a small diameter part, and is configured to pressurize the fuel on the small diameter part side using fuel pressure acting on the large diameter part. The fuel pressure is applied as a back pressure so as to oppose the fuel pressure, and the operation of the pressure-increasing piston is regulated. When the fuel pressure needs to be increased, the fuel pressure is removed and the pressure-increasing piston is operated.

By the way, in the common rail type fuel injection device, the fuel in the fuel tank is pumped up by the feed pump and supplied to the supply pump, and is pressurized to a predetermined pressure by the supply pump and pumped to the common rail. The amount of pressurized fuel other than fuel injection increases by the amount of return fuel when the fuel is excluded, and the capacities of the supply pump and the feed pump are inevitably insufficient. Therefore, the supply pump side copes with the capacity expansion and returns the return fuel to the supply pump inlet side (feed pump outlet side) via the orifice and check valve without returning the return fuel to the fuel tank. Possible measures to make up for the lack of capacity.
JP-A-8-21332

However, when the return fuel from the pressure increasing mechanism is returned to the supply pump, unlike the case where the return fuel is returned to the fuel tank and supplied to the supply pump along the normal path, the supply pump influences the influence of the return fuel properties. It will be received directly.
Specifically, there is a case where iron powder is mixed in the return fuel returned from the pressure increasing mechanism when circulating through the piping, etc. When the return fuel is returned according to the regular route, the feed pump is supplied from the fuel tank. Iron powder is removed by the existing filter installed in the pipe up to this point, but when the return fuel is returned to the supply pump, the iron powder also flows into the supply pump together with the return fuel, causing a failure. It was.

Further, the temperature of the return fuel from the pressure increasing mechanism rises due to pressurization of the supply pump and the like, and the fuel temperature reaches, for example, about 110 ° C. in the high load high rotation range of the engine. Since the supply pump uses the fuel to lubricate the bearings and cam, the oil film is likely to be cut off as the temperature rises, and the supply pump may be seized.
The present invention has been made to solve such problems, and the object of the present invention is to prevent a supply pump failure due to iron powder mixed in return fuel from a pressure increasing mechanism. The object is to provide a common rail fuel injection device.

  In addition to claim 1, the object of claim 2 is to provide a common rail type fuel injection device capable of preventing the supply pump from being seized by high temperature return fuel from the pressure increasing mechanism.

  In order to achieve the above object, a first aspect of the present invention includes a common rail that stores fuel pressurized by a pressurizing pump, a fuel injection mechanism that injects fuel supplied from the common rail into the cylinder of the engine, and a common rail. The fuel injection mechanism is provided between the fuel injection mechanism and the fuel pressure of the common rail acts on one side of the piston to regulate the operation of the piston. Pressure increasing mechanism that can further pressurize and supply the fuel to the fuel injection mechanism, and a return path that returns the return fuel to the inlet side of the pressure pump when the fuel pressure acting on one side of the piston of the pressure increasing mechanism is removed And a pulsation suppressing means provided in the return path, and a filter provided downstream of the pulsation suppressing means in the return path.

  Accordingly, the fuel is pressurized by the pressurizing pump, stored in the common rail, and supplied from the common rail to the fuel injection mechanism. The fuel pressure of the common rail acts as a back pressure on one side of the piston of the pressure increasing mechanism. During the operation of the fuel pressure, the operation of the piston is restricted and the fuel pressure is not increased by the pressure increasing mechanism. Is injected into the cylinder of the engine at the common rail pressure, and when the fuel pressure acting on the piston of the pressure increasing mechanism is eliminated, the fuel from the common rail is further pressurized by the operation of the piston and is injected into the fuel injection mechanism. The fuel injection pressure into the cylinder is further increased. As a result, it is possible to arbitrarily change the fuel injection rate waveform in accordance with the presence or absence of fuel pressure increase by the pressure increase mechanism and the timing of start of pressure increase (timing to eliminate fuel pressure acting on the piston).

  On the other hand, the return fuel when the fuel pressure acting on one side of the piston of the pressure increasing mechanism is removed is returned to the inlet side of the pressurizing pump through the return path. At this time, the fuel is subjected to pressure pulsation by the pulsation suppressing means. After being suppressed, it is returned to the inlet side of the pressure pump. As the pulsation suppressing means, for example, an orifice for restricting the flow rate of the return fuel, a check valve for preventing a back flow of the return fuel, or the like is used. Since the filter is provided on the downstream side of the pulsation suppressing means, the return fuel after the pressure pulsation is suppressed is filtered, so that the filter is prevented from being damaged and the filtration function from being lowered due to the pressure pulsation. Thus, the iron powder mixed in the return fuel can be reliably removed.

The invention of claim 2 is the invention according to claim 1, wherein a heater core is provided in the return path, and the heater core is disposed in a heater unit for heating mounted on the vehicle.
Therefore, the temperature of the return fuel discharged from the pressure increasing mechanism has risen due to pressurization by a pressurizing pump, etc., and when the return fuel flows through the heater core, the heating air is heated and the heat of the return fuel is heated. On the other hand, since the return fuel is cooled by heating the heating air, a situation in which the high-temperature return fuel is returned to the pressurizing pump and seizure occurs is prevented.

  As described above, according to the common rail fuel injection device of the first aspect of the present invention, the filter for filtering the return fuel from the pressure increasing mechanism is provided on the downstream side of the pulsation suppressing means, and the pressure pulsation is suppressed. Since the return fuel is filtered, the iron powder mixed in the return fuel can be surely removed by preventing the filter from being damaged and the filter function from being lowered, thereby preventing the supply pump from being damaged due to the iron powder. be able to.

  In the invention of claim 2, in addition to claim 1, since the return fuel is cooled by using the heat of the return fuel from the pressure increasing mechanism for heating, seizure of the pressurizing pump by the high-temperature return fuel is performed. Can be prevented in advance.

Hereinafter, an embodiment in which the present invention is embodied in a common rail fuel injection device for a vehicle engine will be described.
FIG. 1 is an overall configuration diagram showing a common rail fuel injection device according to the present embodiment. A fuel tank 1 installed in the vehicle is connected to a feed pump 3 via a tank fuel path 2, and the feed pump 3 is provided with a filter 4 and an electromagnetic feed fuel amount adjusting valve 5 via a feed fuel path 6. It is connected to a pump 7 (pressure pump). The supply pump 7 is connected to a common rail 10 through a pair of supply fuel passages 9 each having a check valve 8. Although the feed pump 3 and the supply pump 7 are shown separately in the figure, these actual pumps 3 and 7 are integrated and driven by an engine (not shown) via a common drive shaft 11.

  The fuel in the fuel tank 1 is pumped up by the feed pump 3 and supplied to the supply pump 7 through the tank fuel path 2 and the feed fuel path 6, and further pressurized by the supply pump 7 to the common rail 10 through the supply fuel path 9. Supplied. The fuel intake amount of the supply pump 7 is limited according to the opening degree of the feed fuel amount adjusting valve 5, and the fuel discharge amount of the supply pump 7 is controlled accordingly to adjust the fuel pressure in the common rail 10.

  A fuel injection valve 21 provided in each cylinder of the engine is connected to the common rail 10 via a common rail fuel passage 22, and the fuel injection valve 21 has a posture in which the tip (lower side) faces the cylinder of each cylinder. It is arranged. The configuration of the fuel injection valve 21 is roughly divided into a fuel injection mechanism 31 that controls fuel injection into the cylinder of the engine and a pressure increase mechanism 51 that increases the pressure of fuel supplied to the fuel injection mechanism 31 in advance.

  First, the structure of the fuel injection mechanism 31 will be described. An injection hole portion 32, a fuel reservoir 33, a spring chamber 34, and a pressure chamber 35 are continuously formed in the body 21a of the fuel injection valve 21 from the front end side. A tip end portion 36 a of a needle valve 36 is disposed in the nozzle hole portion 32 and the fuel reservoir 33, a collar portion 36 b of the needle valve 36 is disposed in the spring chamber 34, and the needle valve 36 is disposed in the pressure chamber 35. The piston portion 36c is disposed, and the tip portion 36a, the flange portion 36b, and the piston portion 36c are formed by combining the respective parts. In the spring chamber 34, a spring 37 is interposed between the upper surface of the flange 36 b of the needle valve 36 and the upper wall of the spring chamber 34. The urging force of the spring 37 urges the needle valve 36 downward. Yes.

The common rail fuel passage 22 is connected to one end of a fuel supply passage 38 formed in the body 21 a of the fuel injection valve 21, and a check valve 39 is provided in the fuel supply passage 38. The other end of the fuel supply path 38 is connected to a fuel reservoir 33 of the fuel injection mechanism 31, and fuel from the common rail fuel path 22 is guided to the injection hole 32 through the fuel supply path 38 and the fuel reservoir 33.
One end of a pressure passage 41 having an orifice 40 is connected to a location downstream of the check valve 39 (fuel reservoir 33 side) of the fuel supply passage 38, and the other end of the pressure passage 41 is connected to the upper portion of the pressure chamber 35. It is connected. Accordingly, the fuel pressure in the fuel supply passage 38 acts as a back pressure on the upper surface of the piston portion 36 c of the needle valve 36 located in the pressure chamber 35 through the pressure passage 41, while the needle valve 36 has a fuel reservoir 33 at the location. The upward fuel pressure is acting. Since the resultant force of the fuel pressure acting on the upper surface of the piston portion 36c of the needle valve 36 and the urging force of the spring 37 exceeds the fuel pressure acting on the fuel reservoir 33, the needle valve 36 is urged downward to move the tip portion 36a. The valve is held in a closed state in pressure contact with the nozzle hole portion 32.

  An electromagnetic injection control valve 43 is connected to the upper portion of the pressure chamber 35 via an orifice 42, and the injection control valve 43 is connected to the fuel tank 1 via a return path 44. The return path 44 is shared by the cylinders, and the return paths 44 of the cylinders are gathered together in the vicinity of the engine and connected to the fuel tank 1. As the injection control valve 43 is opened, the fuel in the upper portion of the pressure chamber 35 is collected in the fuel tank 1 via the return path 44, and the fuel pressure acting as a back pressure is applied to the upper surface of the piston portion 36c of the needle valve 36. Since the fuel pressure rapidly decreases, the magnitude relationship of the fuel pressure is reversed, and the needle valve 36 is urged upward to be switched to the valve open state.

  On the other hand, the pressure increasing mechanism 51 is provided above the fuel injection mechanism 31. A cylinder 52 of a pressure increasing mechanism 51 is formed in the body 21 a of the fuel injection valve 21, and a pressure increasing piston 53 is disposed in the cylinder 52 so as to be movable up and down and is urged upward by a spring 60. The booster piston 53 includes an upper large-diameter portion 53a and a lower small-diameter portion 53b. The large-diameter portion 53a of the booster piston 53 divides the cylinder 52 into an upper cylinder chamber 52a and a lower cylinder chamber 52b. A pressurizing chamber 52 c is defined below the small diameter portion 53 b of the pressure increasing piston 53.

  A location upstream of the check valve 39 in the fuel supply path 38 is connected to the upper cylinder chamber 52 a via the upper supply path 54 and the lower cylinder chamber via a lower supply path 56 having an orifice 55. The fuel is introduced into each of the cylinders 52a and 52b. Further, the downstream side of the check valve 39 in the fuel supply passage 38 is connected to the pressurizing chamber 52c through the pressurizing passage 57, and fuel is also introduced into the pressurizing chamber 52c. The resultant force of the fuel pressure acting as the back pressure on the lower surface of the large diameter portion 53a of the pressure increasing piston 53 and the urging force of the spring 60 exceeds the fuel pressure acting on the upper surface of the large diameter portion 53a. The pressurizing chamber 52c is held at the maximum volume.

  An electromagnetic pressure-increasing control valve 58 is connected to the lower cylinder chamber 52b of the pressure-increasing mechanism 51. The pressure-increasing control valve 58 is connected to the filter 4 in the feed fuel path 6 and the feed fuel amount adjusting valve via a return path 59. 5 is connected to the inlet side of the supply pump 7. As the pressure increase control valve 58 is opened, the fuel in the lower cylinder chamber 52b is returned to the inlet side of the supply pump 7 through the return path 59, and serves as a back pressure on the lower surface of the large diameter portion 53a of the pressure increase piston 53. Since the operating fuel pressure rapidly decreases, the magnitude relation of the fuel pressure is reversed, and the pressure increasing piston 53 is urged downward to reduce the volume of the pressurizing chamber 52c. The return path 59 is also shared by each cylinder, and the return paths 59 of the cylinders are gathered together in the vicinity of the engine and connected to the inlet side of the supply pump 7.

  On the other hand, the orifice 61 (pulsation suppressing means), the check valve 62 (pulsation suppressing means), the heater core 63, and the filter are arranged in order from the upstream side to the downstream side (supply pump 7 side) of the return path 59 from each cylinder. 64 is provided. The return path 59 is piped so as to detour once from the inside of the engine room to the passenger compartment side, and its heater core 63 is incorporated in a heater unit 65 installed on the passenger compartment side. The structure of the heater unit 65 will be described below. .

Here, since the heater unit 65 also incorporates an existing heater core 66 in which engine coolant circulates together with the heater core 63, the fuel heater core 63 in the return path 59 is used to distinguish the heater cores 63, 66. And the existing one is called a cooling water heater core 66.
The duct 67 of the heater unit 65 is installed at the foot of a passenger seat in the passenger compartment, and a fan 70 driven by a motor 69 is installed at an entrance 68 provided on one side of the duct 67. The inlet 68 selectively communicates with the interior or exterior of the vehicle according to the operation of the air conditioning panel by the driver, and the interior or outside air of the interior of the vehicle is introduced as the fan 70 is operated. The duct 67 is bifurcated from an inlet 68 into a first passage 71 and a second passage 72, a fuel heater core 63 is disposed in the first passage 71, and a coolant heater core 66 is disposed in the second passage 72. ing. On the opposite side of the inlet 68, the first passage 71 and the second passage 72 merge to form an outlet 73, and the outlet 73 communicates with air outlets (not shown) provided in each part of the vehicle interior.

  A fuel heater core damper 75 driven by a motor 74 is provided on the outlet 73 side of the first passage 71, and the first passage 71 communicates with or shuts off the outlet 73 side according to the opening and closing of the fuel heater core damper 75. Is done. Similarly, a cooling water heater core damper 77 driven by a motor 76 is provided on the outlet 73 side of the second passage 72, and the second passage 72 is connected to the outlet 73 side according to the opening / closing of the cooling water heater core damper 77. Communicated or blocked.

A discharge passage 78 is formed to be branched between the fuel heater core 63 and the fuel heater core damper 75 in the first passage 71, and the first passage 71 communicates with the outside of the vehicle via the discharge passage 78. The discharge passage 78 is provided with an outside discharge damper 80 driven by a motor 79, and the first passage 71 is communicated with or cut off from the outside of the vehicle according to the opening and closing of the outside discharge damper 80.
On the other hand, an input / output device (not shown), a storage device (ROM, RAM, etc.) used for storing control programs, a control map, etc., a central processing unit (CPU), a timer counter, etc. Control unit) is installed. On the input side of the ECU 91, a rail pressure sensor 92 that detects the fuel pressure in the common rail 10, a temperature sensor 93 that detects the temperature of the return fuel flowing in the return path 59 of the pressure increasing mechanism 51, and an accelerator operation amount (not shown). Various sensors such as an accelerator sensor to detect, a cylinder discrimination sensor for discriminating each cylinder, and a crank angle sensor for outputting a crank angle signal synchronized with the rotation of the engine are connected. Further, on the output side of the ECU 91, the feed fuel amount adjustment valve 5, the injection control valve 43 of the fuel injection valve 21 of each cylinder, the pressure increase control valve 58, the fan drive motor 69 of the heater unit 65, and the fuel heater core damper drive Devices such as a motor 74 for cooling water, a damper driving motor 76 for cooling water heater core, and a damper driving motor 79 for discharging outside the vehicle are connected.

  Then, the ECU 91 determines the common rail pressure and the fuel injection amount based on various information related to the engine operating state such as the accelerator operation amount (engine load) detected by the accelerator sensor and the engine rotational speed calculated from the crank angle signal from the crank angle sensor. Then, target values such as the fuel injection timing, the presence or absence of fuel pressure increase by the pressure increase mechanism 51, and the operation timing of the pressure increase mechanism 51 are set, and the feed fuel amount adjusting valve 5, the injection control valve 43, and the pressure increase control valve 58 are driven. The fuel injection is executed with the optimum injection rate waveform for the engine operating state.

Therefore, the operation of the common rail fuel injection device based on the processing of the ECU 91, particularly the operation state of the pressure increasing mechanism 51 will be described.
The fuel in the fuel tank 1 is pumped up by the feed pump 3 driven by the engine, the iron powder is removed by the filter 4 through the tank fuel path 2 and the feed fuel path 6, and then supplied to the supply pump 7. Is further pressurized and supplied to the common rail 10 through the supply fuel passage 9. The ECU 91 adjusts the fuel discharge amount by limiting the fuel intake amount of the supply pump 7 by controlling the opening degree of the feed fuel amount adjusting valve 5, and feeds back the actual common rail pressure detected by the rail pressure sensor 92 to the target value of the rail pressure. Control.

On the other hand, the fuel injection valve 21 operates as follows according to the opening and closing of the injection control valve 43 and the pressure increase control valve 58.
The fuel in the common rail 10 is supplied to the fuel injection valve 21 of each cylinder through the common rail fuel path 22, and the injection hole portion 32 passes through the fuel supply path 38 and the fuel reservoir 33 of the fuel injection mechanism 31 in the body 21 a of each fuel injection valve 21. Is led to the upper part of the pressure chamber 35 through the pressure path 41. When the injection control valve 43 is closed, the needle valve 36 is urged downward by the fuel pressure acting as a back pressure on the upper surface of the piston portion 36c of the needle valve 36 and is held in the closed state.

  Further, the fuel from the common rail fuel path 22 is introduced into the upper cylinder chamber 52a of the pressure increasing mechanism 51 through the upper supply path 54, and is introduced into the lower cylinder chamber 52b through the lower supply path 56. It is also introduced into the pressurizing chamber 52 c through the pressure path 57. As a result, fuel pressure is applied to the upper and lower surfaces of the large-diameter portion 53a of the pressure increasing piston 53. When the pressure increase control valve 58 is closed, the pressure increasing piston 53 is urged upward by the fuel pressure acting as a back pressure on the lower surface of the large diameter portion 53a of the pressure increasing piston 53, and the pressure chamber 52c is maximized. Hold in volume.

  When the injection control valve 43 is opened from the above state, the fuel in the upper portion of the pressure chamber 35 is returned to the fuel tank 1 side via the return path 44, and the back pressure is applied to the upper surface of the piston portion 36c of the needle valve 36. Therefore, the needle valve 36 is urged upward to be switched to the valve open state, and fuel injection is started from the injection hole portion 32. After that, when the injection control valve 43 is closed, the fuel flow to the fuel tank 1 is stopped and the fuel pressure at the upper part of the piston portion 36c is recovered, so that the needle valve 36 is urged downward again to close the valve. It returns to the state and fuel injection is stopped.

The above is a case where the fuel of the common rail pressure is injected as it is without performing the fuel pressure increase by the pressure increase mechanism 51. When the fuel pressure increase by the pressure increase mechanism 51 is performed, the opening and closing of the injection control valve 43 is controlled. Thus, the pressure increase control valve 58 is driven to open and close at a predetermined timing.
For example, as indicated by the solid line in FIG. 2, the pressure increase control valve 58 of the pressure increase mechanism 51 is opened at a predetermined time prior to the opening of the injection control valve 43. As the pressure increase control valve 58 is opened, the fuel in the lower cylinder chamber 52b is returned to the inlet side of the supply pump 7 via the return path 59 and acts as a back pressure on the lower surface of the large diameter portion 53a of the pressure increase piston 53. Since the fuel pressure to be suddenly decreased, the pressure increasing piston 53 is urged downward to reduce the volume of the pressurizing chamber 52c. That is, the fuel in the pressurizing chamber 52c is pressurized on the small diameter portion 53b side by using the fuel pressure acting on the large diameter portion 53a of the pressure increasing piston 53, and the check valve 39 in the fuel supply passage 38 is pressurized. The fuel existing in the further downstream side (pressurizing chamber 52c, fuel supply path 38, fuel reservoir 33, nozzle hole portion 32) further increases from the fuel pressure corresponding to the original common rail pressure.

  Accordingly, when the injection control valve 43 is subsequently opened, the injection pressure rises rapidly from the initial stage of injection and is maintained at a pressure higher than the common rail pressure, and thereafter, the injection control valve 43 and the pressure increase control valve 58 are moved back and forth. When the valve is closed, the needle valve 36 is urged downward to be in a closed state, and fuel injection is stopped. Then, as the opening timing of the pressure increase control valve 58 is delayed (closer to the opening timing of the injection control valve 43) as shown by the broken line or the alternate long and short dash line, the increase in the injection pressure at the initial stage of injection becomes more gradual. An injection rate waveform that suppresses initial injection is realized. On the premise of such characteristics, the ECU 91 controls the valve opening timing of the pressure increase control valve 58 based on the accelerator operation amount, the engine rotation speed, and the like, thereby always obtaining an optimum injection rate waveform for the engine operating state. It is adjusted.

On the other hand, the return fuel from the pressure increasing mechanism 51 is returned to the inlet side of the supply pump 7 without being collected in the fuel tank 1, and as a result, the required fuel amount on the supply pump 7 side is reduced by the amount of return fuel. The shortage of the capacity of the feed pump 3 is compensated, and a smaller feed pump 3 can be applied.
Then, the return fuel from the pressure increasing mechanism 51 sequentially flows through the orifice 61, the check valve 62, the fuel heater core 63, and the filter 64 on the return path 59, and the pressure at the orifice 61 and the check valve 62 against this return fuel. Pulsation is suppressed, the fuel heater core 63 radiates heat, and the filter 64 removes iron powder. Therefore, each operation will be described below.

  First, the operation of the orifice 61 and the check valve 62 will be described. As shown by the solid line in FIG. 2, the return fuel is discharged from the outlet of the pressure increasing mechanism 51 with a large pressure pulsation (for example, about 4 MPa). This pressure pulsation is suppressed as shown by the broken line by the flow rate restriction by the orifice 61, and is further suppressed almost completely as shown by the one-dot chain line by the backflow prevention by the check valve 62. The fuel pressure of the fuel becomes substantially constant (for example, approximately 0.5 MPa which is substantially equal to the discharge pressure of the feed pump 3), and is supplied to the supply pump 7 in this state. Therefore, without being affected by the pressure pulsation when discharged from the pressure increasing mechanism 51, the fuel is pressurized by the control of the feed fuel amount adjusting valve 5 on the supply pump 7 side, and as a result, an accurate common rail pressure is achieved. Is done.

  Further, the operation of the filter 64 will be described when the return fuel from the pressure-increasing mechanism 51 is returned to the fuel tank 1 and supplied to the supply pump 7 according to the normal path. There is a possibility that iron powder may be mixed in the piping from the supply pump 7 to the pressure increasing mechanism 51 (common rail fuel path 22 and fuel supply path 38). Since the iron powder is removed by the filtration of 64, the failure of the supply pump 7 due to the iron powder can be prevented in advance.

  Here, the filter 64 is provided on the downstream side of the orifice 61 and the check valve 62 in the return path 59, and filters the return fuel after pressure pulsation is suppressed. With such an arrangement of the filter 64, the filter paper built in the filter 64 exhibits a filtering action without being subjected to pressure pulsation. As a result, the filter paper is prevented from being damaged by the pressure pulsation, and the periodicity of fuel accompanying the pressure pulsation is prevented. The filtration function is lowered due to the back flow, that is, the phenomenon that the iron powder trapped on the filter paper is separated by the back flow is prevented, and the filtration function of the filter 64 is improved to more reliably prevent the supply pump 7 from being broken by the iron powder. be able to.

  On the other hand, when the operation of the fuel heater core 63 is described, the temperature of the return fuel discharged from the pressure increasing mechanism 51 rises due to pressurization of the supply pump 7 or the like, and the fuel temperature changes according to the operating state of the engine. For example, a return fuel of about 50 ° C. is circulated through the fuel heater core 63 in the low load and low rotation region and about 110 ° C. in the high load and high rotation region. On the ECU 91 side, the heater unit 65 is controlled as follows in order to cool the return fuel using the fuel heater core 63.

  Specific control by the ECU 91 is performed in accordance with Table 1, and the operating states of the dampers 75, 77, 80 and the fan 70 of the heater unit 65 are switched according to the return fuel temperature and the necessity of heating.

  Here, the level of the fuel temperature is determined by using an upper limit temperature (for example, 80 ° C.) at which the supply pump 7 is not likely to be burned when the return fuel is returned as a threshold value. It is determined according to whether heating is selected by the operation of.

  First, when the return fuel temperature is high and heating is required, the fuel heater core damper 75 is opened, the cooling water heater core damper 77 is closed, the outside discharge damper 80 is closed, and the fan 70 is operated to be introduced into the duct 67. The air thus introduced is guided from the inlet 68 side to the outlet 73 side through the first passage 71. Therefore, the air flowing through the first passage 71 is heated by the fuel heater core 63 and blown into the vehicle compartment from each outlet, while the return fuel in the fuel heater core 63 is cooled. That is, at this time, the heat of the return fuel is used for heating.

  When the return fuel temperature is high and heating is not required, the fuel heater core damper 75 is closed, the coolant heater core damper 77 is closed, the vehicle discharge damper 80 is opened, and is introduced into the duct 67 by the fan 70. The air is guided from the inlet 68 side to the outside of the vehicle through the first passage 71 and the discharge passage 78. Accordingly, the return fuel in the fuel heater core 63 is cooled by the air flowing through the first passage 71 as in the case of the heating required as described above. At this time, the heated air is unnecessary and is discharged outside the vehicle.

  When the return fuel temperature is low and heating is required, the fuel heater core damper 75 is closed, the cooling water heater core damper 77 is opened, the outside discharge damper 80 is closed, and is introduced into the duct 67 by the fan 70. Air is guided from the inlet 68 side to the outlet 73 side through the second passage 72. Therefore, the air flowing through the second passage 72 is heated by the cooling water heater core 66 and blown into the vehicle compartment from each outlet. That is, when the temperature of the return fuel is low, cooling of the return fuel with air is unnecessary and is not performed. On the other hand, since heating of the air using the return fuel cannot be expected, it is the same as a general vehicle heating system. In addition, the heat of engine cooling water is used for heating.

When the return fuel temperature is low and heating is not required, all the dampers 75, 77, 80 are closed and the fan 70 is stopped. Therefore, the air is not heated by any of the heater cores 63 and 66, and the return fuel is not cooled.
In the above control example, the fuel heater core damper 75 and the coolant heater core damper 77 are switched in two positions. However, the opening degree of the dampers 75 and 77 according to the temperature of the return fuel and the required temperature in the passenger compartment. May be continuously switched in the reverse direction.

  As a result of the above control, when the temperature of the return fuel from the pressure increasing mechanism 51 is high, the return fuel is cooled by the fuel heater core 63, so the high-temperature return fuel is returned to the supply pump 7 to cause seizure. The situation can be prevented in advance, and moreover, when heating the vehicle interior, the heat of the return fuel can be effectively used for heating without being thrown out of the vehicle. In addition, when the temperature of the return fuel is low, it is switched to heating with the existing engine cooling water. Even in this case, heating can be continued without causing any trouble, and the demerit of the configuration in which the heat of the return fuel is used for heating. That is, it is possible to prevent a situation in which the passenger compartment cannot be heated when the temperature of the return fuel is low.

This is the end of the description of the embodiment, but the aspect of the present invention is not limited to this embodiment. For example, in the above-described embodiment, the invention is embodied in a common rail fuel injection device for a vehicle engine. However, the application target is not limited to a vehicle engine, and may be applied to, for example, a stationary engine.
In the above embodiment, the orifice and the check valve are used as the pulsation suppressing means. However, the present invention is not limited to this. For example, an accumulator or the like may be used as the pulsation suppressing means. If it is installed on the downstream side, the same operational effects relating to pressure pulsation as in the above embodiment can be obtained.

  Further, in the above embodiment, the return fuel from the pressure increasing mechanism 51 is returned between the filter 4 in the feed fuel path 6 and the feed fuel amount adjusting valve 5, but is returned to the upstream side of the filter 4 in the feed fuel path 6. May be. In the case of such a configuration, the filter 4 performs the filtering function of the return fuel, and therefore the filter 64 may be omitted.

It is a whole lineblock diagram showing the common rail type fuel injection device of an embodiment. It is a figure which shows the relationship between the operation time of a pressure increase mechanism, and an injection rate waveform, and the pressure pulsation of each place of a return path.

Explanation of symbols

7 Supply pump 10 Common rail 31 Fuel injection mechanism 51 Pressure increasing mechanism 59 Return path 61 Orifice (pulsation suppressing means)
62 Check valve (pulsation suppression means)
63 Fuel heater core 64 Filter 65 Heater unit

Claims (2)

A common rail for storing fuel pressurized by a pressure pump;
A fuel injection mechanism for injecting fuel supplied from the common rail into the cylinder of the engine;
Provided between the common rail and the fuel injection mechanism, the fuel pressure of the common rail acts on one side of the piston to regulate the operation of the piston, and the fuel pressure acting on the one side is excluded A pressure increasing mechanism capable of operating a piston, further pressurizing fuel from the common rail and supplying the fuel injection mechanism;
A return path for returning the return fuel to the inlet side of the pressurizing pump when the fuel pressure acting on one side of the piston of the pressure increasing mechanism is removed;
Pulsation suppression means provided in the return path;
And a filter provided on the return path downstream of the pulsation suppressing means.   2. The common rail fuel injection apparatus according to claim 1, wherein a heater core is provided in the return path, and the heater core is disposed in a heater unit for heating mounted on a vehicle.

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