JP4407647B2 - Fuel injection device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel injection device for an internal combustion engine that injects high-pressure fuel stored in a pressure accumulator into the internal combustion engine.

  In a common rail fuel injection device known as a diesel engine fuel injection device, high pressure fuel is stored in an accumulator, and the high pressure fuel stored in the accumulator is injected into a combustion chamber of each cylinder of the internal combustion engine via an injector. It is configured to supply. In addition, since it is necessary to always store high pressure fuel corresponding to the fuel injection pressure in the accumulator, fuel is supplied to the high pressure pump by the low pressure pump, and the high pressure fuel is pressurized by increasing the pressure by the high pressure pump. It is designed to supply the accumulator.

  Here, by adjusting the area of the fuel passage from the low pressure pump to the high pressure pump with an electromagnetic metering valve, the amount of fuel supplied to the high pressure pump and hence the amount of fuel pumped from the high pressure pump are adjusted. To do.

More specifically, the metering valve adjusts the area of the fuel passage from the low pressure pump to the high pressure pump by controlling the electromagnetic force to control the relative position of the valve body with respect to the valve body. ing. Also, based on the deviation between the target pressure of the fuel in the pressure accumulator and the current pressure, the target value for the amount of fuel supplied to the high-pressure pump is calculated, and the target drive current for the metering valve is calculated based on the target value. Then, duty control is performed on the power applied to the metering valve so as to achieve this target drive current (see, for example, Patent Document 1).
JP 2001-3791 A

  However, in the apparatus described in Patent Document 1, the metering valve operates at a high speed and with a small amplitude width by duty drive, and therefore when the valve body and the valve body are eccentric, the valve body and the valve body Of the sliding portion, the oil film is likely to be cut off at the portion where the clearance is small, sliding wear occurs in a short time, and the valve body may not operate smoothly.

  Also, when the metering valve is used with the valve body and the shaft of the valve body horizontal, or when the suction force acts in the radial direction on the valve body on the magnetic circuit of the metering valve In this case, eccentricity tends to be promoted, and sliding wear is promoted.

  And since the metering valve is used in a low-pressure fuel atmosphere, the force to return the valve body to the concentric position with respect to the valve body (that is, the aligning force) and the oil film maintenance force of the sliding part are insufficient. . In addition, when solid materials such as sliding wear powder or sticky substances generated due to abnormal fuel properties adhere to the sliding part, these solid materials are washed out to the metering valve used in a low-pressure fuel atmosphere. We cannot expect that much detergency.

  In view of the above points, the present invention provides a fuel injection device for an internal combustion engine that includes a metering valve that adjusts the area of a passage for sending fuel from a low pressure pump to a high pressure pump so that the valve body of the metering valve can operate smoothly. The purpose is to do.

In the present invention, the valve body (32) slidably disposed in the valve body (31) is displaced to adjust the area of the passage for sending fuel from the low pressure pump (20) to the high pressure pump (10). In the fuel injection device for an internal combustion engine provided with the quantity valve (30) , the valve body (31) receives fuel having a pressure higher than that of the fuel supplied from the low pressure pump (20) to the metering valve (30). An inlet (313) for supplying the fuel to the sliding part between the valve body (31) and the valve body (32), located on one end side from the inlet (313), and flows in from the inlet (313) 1st outlet (314) which flows in after the fuel which passed through a sliding part and the other end side from an inlet (313), and the fuel which flowed in from an inlet (313) passes through a sliding part And a second outlet (315) that flows in after the Characterized in that it comprises a mouth (314) and a second outlet low-pressure part of the fuel flows into the (315) fuel return passage back to (5) (8).

  In this way, since the high-pressure fuel is supplied to the sliding portion, the aligning force and the oil film maintenance force increase, and it is difficult for oil film breakage and sliding wear to occur. Further, since the high-pressure fuel is supplied to the sliding portion, the detergency is increased and the solid matter attached to the sliding portion can be washed away. Therefore, in combination, the valve element (32) of the metering valve (30) can operate smoothly.

  In this case, the high-pressure fuel pumped from the high-pressure pump (10) to the pressure accumulator (1) can be supplied to the sliding portion.

  In this way, since the high-pressure fuel always flows through the clearance of the sliding portion, a high detergency can always be obtained, and the solid matter adhering to the sliding portion can be more reliably washed away.

  By the way, when the high-pressure fuel supplied to the sliding part flows to the suction port (311) and discharge port (312) side of the valve body (31), the fuel sent from the low-pressure pump (20) to the high-pressure pump (10). The pressure, temperature, etc. of the fuel change, and the metering accuracy of the fuel supplied to the high-pressure pump (10) decreases.

Therefore, one of the first outlet (314) and the second outlet (315) is connected between the inlet (311) and the outlet (312) and the inlet (313). The high-pressure fuel that flows in from the inlet (313) and flows toward the suction port (311) and the discharge port (312) through the sliding portion flows into the low-pressure portion (5) through the outlet (315). ).

  In this way, the high-pressure fuel flowing in from the inlet (313) is prevented from flowing to the suction port (311) and the discharge port (312), and the fuel supplied to the high-pressure pump (10) is regulated. A decrease in quantity accuracy can be prevented.

  In addition, the code | symbol in the bracket | parenthesis of each means described in a claim and this column shows the correspondence with the specific means as described in embodiment mentioned later.

(First embodiment)
A first embodiment of the present invention will be described. FIG. 1 is a diagram showing an overall configuration of a fuel injection device according to a first embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view showing a main part of FIG.

  As shown in FIG. 1, the fuel injection device includes a pressure accumulator 1 that accumulates high-pressure fuel. A plurality of injectors 2 are connected to the pressure accumulator 1, and the injector 2 is controlled by a control device (hereinafter referred to as ECU) 3 to open a valve for a predetermined period at a predetermined time and is supplied from the pressure accumulator 1. Fuel is injected into each cylinder of a diesel engine (not shown). Here, only the injector 2 corresponding to one of the four-cylinder engines is shown, and illustration of the injectors corresponding to the other cylinders is omitted.

  The high pressure fuel stored in the pressure accumulator 1 is supplied from the fuel supply means P via the high pressure passage 4. The fuel supply means P sucks fuel from the fuel tank 5 through the filter 6, pressurizes the sucked fuel to a high pressure, and pumps the fuel to the high pressure passage 4. The details of the fuel supply means P will be described later.

  A return fuel passage 7 for returning leaked fuel from the injector 2 to the fuel tank 5 is connected to the injector 2. The fuel supply means P is connected to a return fuel passage 8 for returning the leaked fuel from the fuel supply means P to the fuel tank 5 as a low pressure portion.

  The ECU 3 includes a known microcomputer including a CPU, ROM, RAM, and the like (not shown), and performs arithmetic processing according to a program stored in the microcomputer. A signal from a fuel pressure sensor 9 that detects the pressure in the pressure accumulator 1 is input to the ECU 3, and various information such as the engine speed and the accelerator opening is input from various sensors S as needed.

  The ECU 3 calculates the optimal injection timing and injection amount (injection period) according to the operating state of the engine and the vehicle, and controls the valve opening timing and valve opening period of each injector 2. Further, the ECU 3 calculates the target discharge amount of the fuel supply means P, outputs a control signal to the fuel supply means P, and controls the discharge amount of the fuel supply means P. Incidentally, the target discharge amount of the fuel supply means P is the sum of the injection amount, the leak prediction amount, and the adjustment amount for causing the fuel pressure of the pressure accumulator 1 to follow the target pressure in the pressure accumulator.

  Next, the fuel supply means P will be described with reference to FIG. The fuel supply means P pressurizes the fuel and discharges it to the accumulator 1, the low-pressure pump 20 that supplies the fuel sucked from the fuel tank 5 to the high-pressure pump 10, and the low-pressure pump 20 to the high-pressure pump 10. A metering valve 30 for adjusting the flow rate of the supplied fuel is provided.

  In the high-pressure pump 10, a plunger 11 driven by an engine is slidably accommodated in a cylinder 12, and the plunger 11 reciprocates in the cylinder 12. The pump chamber 13 formed by the plunger 11 and the cylinder 12 is supplied with fuel from the low pressure pump 20 via the metering valve 30, and the fuel is pressurized by the plunger 11, and is discharged on the discharge side of the pump chamber 13. It is discharged to the pressure accumulator 1 through a check valve (hereinafter referred to as a discharge valve) 14. On the other hand, a check valve (hereinafter referred to as an intake valve) 15 is also provided on the suction side of the pump chamber 13 to prevent backflow of high-pressure fuel from the pump chamber 13 to the metering valve 30 side.

  The low-pressure pump 20 is driven by an engine or an electric motor, and adjusts so that the pressure of the fuel discharged from the pump unit 21 does not exceed a predetermined pressure, and a pump unit 21 that pumps the fuel sucked from the fuel tank 5 at a low pressure. And a relief valve 22 to be operated.

  The metering valve 30 includes a bottomed cylindrical valve body 31 and a cylindrical valve body 32 slidably inserted into the valve body 31, and the valve body 32 reciprocates in the valve body 31. It comes to move.

  A suction port 311 for sucking fuel supplied from the low pressure pump 20 and a discharge port 312 for discharging fuel sucked from the suction port 311 toward the high pressure pump 10 are formed on the side surface of the valve body 31. .

  The valve body 32 is formed with a low-pressure passage hole 321 that guides the fuel flowing in from the suction port 311 to the discharge port 312. The communication area between the low pressure passage hole 321 and the discharge port 312 (hereinafter referred to as the opening area of the discharge port 312), in other words, the area of the passage for sending fuel from the low pressure pump 20 to the high pressure pump 10 is the position of the valve body 32. To be adjusted according to

  The metering valve 30 includes a coil 33 that generates an electromagnetic force to drive the valve body 32, and the valve body 32 is urged in a direction in which the opening area of the discharge port 312 decreases due to the electromagnetic force of the coil 33. The The metering valve 30 includes a spring (not shown) that biases the valve body 32 in a direction in which the opening area of the discharge port 312 increases.

  Then, when energization to the coil 33 is stopped by a command from the ECU 3, the valve body 32 is biased by the spring and moves to a position where the opening area of the discharge port 312 is maximized.

  On the other hand, when the coil 33 is energized by a command from the ECU 3, the coil 33 generates an electromagnetic force corresponding to the current value and biases the valve body 32 in a direction to close the discharge port 312. And the position of the valve body 32 changes continuously according to the value of the electric current supplied to the coil 33, and the discharge port 312 is adjusted to the opening area according to an electric current value.

  Furthermore, the fuel injection device of the present embodiment has the following configuration. First, a high-pressure portion downstream from the discharge valve 14 of the high-pressure pump 10, more specifically, the high-pressure portion from the high-pressure pump 10 to the accumulator 1 is controlled by a bypass fuel passage 40 formed in the housing of the fuel supply means P. 30. Further, an inlet 313 communicating with the bypass fuel passage 40 is formed on the side of the valve body 31 of the metering valve 30 at a position on the side opposite to the coil from the suction port 311 and the discharge port 312. The high-pressure fuel from the high-pressure pump 10 to the pressure accumulator 1 is guided to the inlet 313 via the bypass fuel passage 40, and the high-pressure fuel passes through the inlet 313 to the valve body 31 and the valve body 32. To the sliding part.

  A first outflow port 314 communicating with the return fuel passage 8 is formed on the end surface (that is, the bottom) of the valve body 31 on the side opposite to the coil. The fuel that has passed through the sliding portion between the valve body 31 and the valve body 32 and has flowed out to the opposite coil side of the valve body 31 is returned to the fuel tank 5 via the first outlet 314 and the return fuel passage 8. .

  A second outlet 315 that communicates with the return fuel passage 8 is formed on the side surface of the valve body 31 at a position on the coil side of the inlet port 313 and on the coil side of the inlet port 311 and the outlet port 312. ing. In addition, a relief groove 322 that is always in communication with the second outlet 315 is formed on the outer peripheral surface of the valve body 32. The fuel passing through the sliding portion between the valve body 31 and the valve body 32 toward the suction port 311 and the discharge port 312 is supplied to the fuel tank via the escape groove 322, the second outlet 315, and the return fuel passage 8. Returned to 5.

  A plurality of annular oil retaining grooves 323 (three in this example) are formed on the outer peripheral surface of the valve body 32 at a position on the side opposite to the coil from the escape groove 322.

  Next, the operation of the fuel injection device configured as described above will be described.

  In FIG. 2, in the intake stroke of the high-pressure pump 10, the low-pressure fuel sent from the low-pressure pump 20 is metered by the metering valve 30, and the metered fuel is suctioned as the plunger 11 moves. 15 is opened and sucked into the pump chamber 13.

  Next, in the pumping stroke of the high-pressure pump 10, the fuel in the pump chamber 13 is pressurized with the movement of the plunger 11, the discharge valve 14 is opened, and the fuel is discharged to the pressure accumulator 1.

  The amount of fuel discharged at this time is controlled by the amount of fuel sucked into the pump chamber 13, and the amount of suction can be controlled by controlling the opening area of the discharge port 312 in the metering valve 30. The opening area of the discharge port 312 varies according to the value of the current supplied to the coil 33. Therefore, by controlling the value of the current supplied to the coil 33, the amount of fuel discharged from the fuel supply means P to the pressure accumulator 1 is controlled.

  Here, fuel whose pressure is higher than the pressure of the fuel supplied from the low-pressure pump 20 to the metering valve 30 is always applied to the sliding portion between the valve body 31 and the valve body 32 via the bypass fuel passage 40 and the inlet 313. Since it is supplied, the aligning force and the oil film maintenance force are increased, and it is difficult for oil film breakage and sliding wear to occur. At this time, the oil holding groove 323 eliminates the bias of the high-pressure fuel in the valve body circumferential direction, so that the eccentricity and inclination of the valve body 32 with respect to the valve body 31 can be prevented more reliably.

  Further, since the high-pressure fuel always flows through the clearance of the sliding portion, a high detergency can always be obtained, and the solid matter adhering to the sliding portion can be surely washed away.

  By the way, when high-pressure fuel flows toward the suction port 311 and the discharge port 312, the pressure or temperature of the fuel sent from the low-pressure pump 20 to the high-pressure pump 10 changes, and the metering accuracy of the fuel supplied to the high-pressure pump 10 is changed. However, in the present embodiment, the fuel that passes through the sliding portion and travels toward the suction port 311 and the discharge port 312 passes through the escape groove 322, the second outlet port 315, and the return fuel passage 8. Therefore, a reduction in the metering accuracy of the fuel supplied to the high-pressure pump 10 can be prevented.

(Second Embodiment)
A second embodiment of the present invention will be described. 3 and 4 are schematic cross-sectional views showing the main parts of the fuel injection device according to the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the same or equivalent part as 1st Embodiment, and the description is abbreviate | omitted.

  In the first embodiment, the high-pressure fuel is always supplied to the sliding portion between the valve body 31 and the valve body 32. However, in the present embodiment, the high-pressure fuel is slid only in the pumping stroke of the high-pressure pump 10. It is intended to be supplied to the moving part.

  As shown in FIG. 3, the fuel injection device of this embodiment includes a bypass fuel passage 50 in which the pump chamber 13 of the high-pressure pump 10 and the inlet 313 of the metering valve 30 are formed in the housing of the fuel supply means P. It is communicated. A check valve 51 that allows only the flow of fuel from the pump chamber 13 to the metering valve 30 is provided in the bypass fuel passage 50.

  Next, the operation of the fuel injection device configured as described above will be described.

  FIG. 3 shows the intake stroke of the high-pressure pump 10, and the low-pressure fuel sent from the low-pressure pump 20 is metered by the metering valve 30, and the metered fuel is moved along with the movement of the plunger 11. The suction valve 15 is opened and sucked into the pump chamber 13. At this time, the check valve 51 is closed to prevent the fuel from being sucked into the pump chamber 13 from the bypass fuel passage 50 side.

  Next, in the pressure feed stroke of FIG. 4, the fuel in the pump chamber 13 is pressurized with the movement of the plunger 11, the discharge valve 14 is opened, and the fuel is discharged to the pressure accumulator 1. Further, in this pressure feed stroke, the high pressure fuel in the pump chamber 13 is supplied to the sliding portion between the valve body 31 and the valve body 32 via the bypass fuel passage 50 and the inflow port 313. As a result, oil film breakage and sliding wear hardly occur.

  In addition, since the high-pressure fuel flows through the clearance of the sliding portion, a high detergency can always be obtained, and the solid matter adhering to the sliding portion can be reliably washed away.

  Further, in the intake stroke, the check valve 51 is closed to prevent the fuel from being sucked into the pump chamber 13 from the bypass fuel passage 50 side. Therefore, only the fuel metered by the metering valve 30 is used. Can be discharged.

(Other embodiments)
In each of the above-described embodiments, the normally open type metering valve 30 is used in which the discharge port 312 is closed when the valve body 32 is sucked into the coil 33, but when the valve body 32 is sucked into the coil 33. A normally closed type metering valve 30 in which the discharge port 312 is opened may be used.

  In the above embodiments, the valve body 32 reciprocates in the valve body 31 is used as the metering valve 30, but the rotary metering valve 30 in which the valve body 32 rotates in the valve body 31 is used. May be used.

It is a figure showing the whole fuel injection device composition concerning a 1st embodiment of the present invention. It is typical sectional drawing which shows the principal part of FIG. It is typical sectional drawing which shows the suction stroke of the fuel-injection apparatus which concerns on 2nd Embodiment of this invention. It is typical sectional drawing which shows a pumping process.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Accumulator, 2 ... Injector, 10 ... High pressure pump, 20 ... Low pressure pump, 30 ... Metering valve, 31 ... Valve body, 32 ... Valve body.

Claims (5)

A pressure accumulator (1) for storing high pressure fuel;
An injector (2) for injecting high-pressure fuel stored in the pressure accumulator (1) into the internal combustion engine;
A high pressure pump (10) for pumping high pressure fuel to the pressure accumulator (1);
A low pressure pump (20) for supplying fuel to the high pressure pump (10);
A metering valve that adjusts the area of a passage through which fuel is sent from the low-pressure pump (20) to the high-pressure pump (10) when the valve body (32) slidably disposed in the valve body (31) is displaced. (30) A fuel injection device for an internal combustion engine comprising:
The valve body (31)
Fuel having a pressure higher than that of the fuel supplied from the low-pressure pump (20) to the metering valve (30) flows in, and the fuel is slid between the valve body (31) and the valve body (32). An inlet (313) for supplying the moving part;
A first outlet (314) that is located on one end side of the inlet (313) and into which the fuel flowing in from the inlet (313) flows after passing through the sliding portion;
A second outlet (315) which is located on the other end side of the inlet (313) and into which the fuel flowing in from the inlet (313) flows after passing through the sliding portion;
The fuel injection device for an internal combustion engine, further comprising a return fuel passage (8) for returning the fuel that has flowed into the first outlet (314) and the second outlet (315) to the low pressure section (5). . 2. The fuel injection device for an internal combustion engine according to claim 1, wherein the high-pressure fuel pumped from the high-pressure pump (10) to the pressure accumulator (1) is supplied to the sliding portion. The high pressure pump (10) includes a pump chamber (13) in which fuel is sucked in a suction stroke and fuel is pressurized in a pressure feeding stroke.
The fuel in the pump chamber (13) pressurized in the pumping stroke is supplied to the sliding portion through a bypass fuel passage (50) communicating the pump chamber (13) and the metering valve (30). The fuel injection device for an internal combustion engine according to claim 1, wherein: The valve body (31) has a suction port (311) for sucking fuel supplied from the low pressure pump (20), and directs fuel sucked from the suction port (311) to the high pressure pump (10). A discharge port (312) for discharging ,
One outflow port (315) of the first outflow port (314) and the second outflow port (315) includes the suction port (311), the discharge port (312), and the inflow port (313). The fuel injection device for an internal combustion engine according to any one of claims 1 to 3, wherein the fuel injection device is disposed between the two. The internal combustion engine according to any one of claims 1 to 4, wherein the metering valve (30) is configured such that the valve body (32) reciprocates in the valve body (31). Fuel injection device.

Images