JP2008215187A - Fuel injection valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent temperature compensation resistance from being ruptured and deformed, and to eliminate a defective resistance value of the temperature compensation resistance. <P>SOLUTION: Temperature compensation resistance 5 for executing temperature compensation of a piezostack 41 is accommodated in a stuck case 48 together with the piezostack 41. The temperature compensation resistance 5 is thereby prevented from undergoing high-temperature and high-pressure environment when molding a connector so that rupture and deformation are suppressed to prevent a defective resistance value. The fuel injection valve is provided with a dummy laminated body 6 for receiving a load in an expansion direction C of the piezostack 41 so as to accommodate the temperature compensation resistance 5 in the state where no load in the expansion direction C of the piezostack 41 is received, in the dummy laminated body 6, thereby protecting the temperature compensation resistance 5 from external force. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel injection valve for injecting fuel into an internal combustion engine.

  A conventional fuel injection device controls the on-off valve operation of a nozzle by using a piezo stack that expands and contracts due to charge and discharge. In order to compensate for a potential difference generated between the terminals of the piezo stack due to expansion and contraction of the piezo stack due to a temperature change or the like, a temperature compensation resistor is attached between the terminals of the piezo stack.

The temperature compensation resistor is installed inside the connector and is resin-molded simultaneously with the connector molding. Thus, the temperature compensation resistor is protected from external force and temperature (see, for example, Patent Document 1).
German Patent Application Publication No. 1,990,346

  However, due to the inflow of high temperature and high pressure resin at the time of molding the connector, there is a problem that the temperature compensation resistance is broken and deformed, causing a resistance value defect.

  The present invention has been made in view of the above points, and it is an object of the present invention to prevent breakage and deformation of a temperature compensation resistor and eliminate a resistance value defect of the temperature compensation resistor.

  The present invention is characterized in that the temperature compensation resistor (5) for compensating the temperature of the piezo stack (41) is housed in the stack case (48) together with the piezo stack (41).

  In this way, since the temperature compensation resistor (5) is not exposed to a high temperature / high pressure environment at the time of molding the connector, it is prevented from being broken or deformed, and a resistance value failure is prevented.

  In this case, a dummy laminated body (6) that receives a load in the expansion / contraction direction (C) of the piezo stack (41) is provided, and the temperature compensation resistor (5) receives a load in the expansion / contraction direction (C) of the piezo stack (41). If the dummy laminated body (6) is housed in the absence, the temperature compensation resistor (5) can be protected from external force.

  Further, the electrode (52) of the temperature compensation resistor (5) and the wiring member (7) connecting the electrode (52) to the terminal of the connector can be brought into contact in a slidable state.

  By doing so, the contact portion between the electrode (52) of the temperature compensation resistor (5) and the wiring member (7) slides according to the expansion and contraction of the piezo stack (41), and therefore the contact portion is filtered. Compared with the aspect joined by etc., the stress which generate | occur | produces in a contact part by expansion-contraction etc. of a piezo stack (41) can be made small.

  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.

  An embodiment of the present invention will be described. FIG. 1 is a cross-sectional view schematically showing the overall configuration of a fuel injection device including a fuel injection valve according to an embodiment of the present invention.

  The fuel injection valve is mounted on a cylinder head of an internal combustion engine (more specifically, a diesel engine, not shown) and injects high-pressure fuel stored in a pressure accumulator (not shown) into the cylinder of the internal combustion engine. It is.

  As shown in FIG. 1, the nozzle body 1 of the fuel injection valve includes a fuel inlet portion 11 into which high-pressure fuel from the pressure accumulator is introduced, and a fuel outlet portion 12 through which fuel inside the fuel injection valve flows out toward the fuel tank 100. And.

  A nozzle 2 that injects fuel when the valve is opened is disposed on one end side in the axial direction of the nozzle body 1. The nozzle 2 includes a nozzle needle 21 that is slidably held on the nozzle body 1, a nozzle spring 22 that urges the nozzle needle 21 in a valve closing direction, and a cylindrical portion into which a piston portion 21a of the nozzle needle 21 is inserted. And a nozzle sleeve 23.

  At one end in the axial direction of the nozzle body 1, an injection hole 24 communicating with the fuel inlet 11 through the high-pressure fuel passage 13 is formed, and high-pressure fuel is injected from the injection hole 24 into the cylinder of the internal combustion engine. Yes. The nozzle body 1 is formed with a tapered valve seat 25 on the upstream side of the nozzle hole 24, and the nozzle needle 21 is formed with a seat portion 21 b on the side opposite to the piston portion, and this seat portion 21 b contacts the valve seat 25. The nozzle hole 24 is opened and closed by separating.

  The cylindrical piston portion 21a is slidably and liquid-tightly inserted into the nozzle sleeve 23, and the control chamber 26 in which the internal fuel pressure is switched between high pressure and low pressure by the piston portion 21a and the nozzle sleeve 23. Is formed. The nozzle needle 21 is urged in the valve closing direction by the fuel pressure in the control chamber 26 and is opened by the high pressure fuel guided from the fuel inlet 11 to the nozzle hole 24 side through the high pressure fuel passage 13. Be energized by.

  A valve chamber 14 in which the control valve 3 for controlling the pressure in the control chamber 26 is accommodated is formed in the intermediate portion in the axial direction of the nozzle body 1. The control chamber 26 is always in communication with the valve chamber 14 via the communication passage 15.

  The valve chamber 14 is connected to the fuel inlet 11 through the high-pressure fuel passage 13. Further, the valve chamber 14 is connected to the fuel outlet portion 12 through a low pressure fuel passage 16.

  The nozzle body 1 is formed with a high pressure side valve seat 18 and a low pressure side valve seat 19 facing the valve chamber 14. The high pressure side valve seat 18 is a portion surrounding a portion where the high pressure fuel passage 13 opens into the valve chamber 14, and the low pressure side valve seat 19 is a portion surrounding a portion where the low pressure fuel passage 16 opens into the valve chamber 14.

  The control valve 3 has a valve body 31 and a valve spring 32. The valve body 31 contacts and separates from the low pressure side valve seat 19 to open and close between the valve chamber 14 and the low pressure fuel passage 16, and contacts and separates from the high pressure side valve seat 18 and between the valve chamber 14 and the high pressure fuel passage 13. Open and close. The valve spring 32 urges the valve body 31 in such a direction that the space between the valve chamber 14 and the high pressure fuel passage 13 is opened and the space between the valve chamber 14 and the low pressure fuel passage 16 is closed.

  An actuator chamber 17 in which the actuator 4 that drives the control valve 3 is housed is formed on the other end side in the axial direction of the nozzle body 1. The actuator chamber 17 is connected to the low pressure fuel passage 16 via the low pressure communication passage 16a.

  The actuator 4 includes a piezo stack 41 in which a large number of piezo elements are stacked and expands and contracts due to charge and discharge, and a transmission unit that transmits the expansion and contraction displacement of the piezo stack 41 to the valve body 31 of the control valve 3.

  The transmission unit is configured as follows. Both the first piston 43 and the second piston 44 formed in a cylindrical shape are slidably and liquid-tightly inserted into the actuator sleeve 42, and between the first piston 43 and the second piston 44, A liquid chamber 45 filled with fuel is formed.

  The first piston 43 is urged toward the piezo stack 41 by a first spring 46 and is directly driven by the piezo stack 41. When the piezo stack 41 is extended, the pressure of the liquid chamber 45 is increased by the first piston 43.

  The second piston 44 is urged toward the valve body 31 side of the control valve 3 by the second spring 47 and is actuated by receiving the pressure of the liquid chamber 45 to drive the valve body 31. When the piezo stack 41 is extended, the second piston 44 operates by receiving the pressure of the liquid chamber 45 that has been increased in pressure, thereby closing the space between the valve chamber 14 and the high-pressure fuel passage 13 and the valve chamber 14. The valve body 31 is driven to a position where the space between the low pressure fuel passage 16 is opened. On the other hand, when the piezo stack 41 contracts, that is, when the pressure in the liquid chamber 45 is low, the second piston 44 is pushed back toward the first piston 43 by the valve spring 32 of the control valve 3 against the second spring 47.

  A back pressure valve 120 that controls the pressure on the low pressure fuel passage 16 side is disposed in the return path 110 that connects the fuel tank 100 and the fuel outlet portion 12. Incidentally, while the pressure of the high pressure fuel stored in the pressure accumulator is 100 MPa or more, the back pressure valve 120 controls the pressure on the low pressure fuel passage 16 side to about 1 MPa.

  Electric power is supplied to the piezo stack 41 via the piezo drive circuit 130. In the piezo drive circuit 130, the energization timing to the piezo stack 41 is controlled by an electronic control circuit (hereinafter referred to as ECU) 140.

  The ECU 140 includes a well-known microcomputer including a CPU, ROM, EEPROM, RAM, and the like (not shown), and performs arithmetic processing according to a program stored in the microcomputer. The ECU 140 receives signals from various sensors (not shown) that detect the intake air amount, the accelerator pedal depression amount, the internal combustion engine speed, the fuel pressure in the accumulator, and the like.

  A detailed configuration of the actuator 4 will be described with reference to FIGS. 2 is a cross-sectional view of the actuator 4 in FIG. 1, FIG. 3 is a perspective view of the main part of the actuator 4 in FIG. 2, FIG. 4 is a view taken in the direction of arrow A in FIG. It is.

  The metal cylindrical stack case 48 includes, in order from one end side, the first piston 43, the piezo stack 41, the dummy laminated body 6 including the temperature compensation resistor 5 for compensating the temperature of the piezo stack 41, and the nozzle body 1 (see FIG. 1) is housed.

  The dummy laminate 6 is made of an insulating resin, and is formed with a recess 61 into which the temperature compensation resistor 5 is inserted and a slit-like groove 62 into which the electrode lead wire 51 of the temperature compensation resistor 5 is inserted. The resin of the dummy laminate 6 is preferably a resin having a linear expansion coefficient close to that of the piezo element.

  The load in the expansion / contraction direction C of the piezo stack 41 acting on the dummy laminate 6 is received by a portion of the dummy laminate 6 excluding the recess 61 and the groove 62. Therefore, the load in the expansion / contraction direction C of the piezo stack 41 does not act on the temperature compensation resistor 5 and the electrode lead wire 51.

  An electrode foil 52 is bonded to a portion of the outer peripheral surface of the dummy laminate 6 where the groove 62 is formed, and the electrode foil 52 and the electrode lead wire 51 are joined by brazing. The electrode foil 52 is connected to a connector terminal (not shown) via a thin metal wiring member 7. The wiring member 7 is in contact with the electrode foil 52 in a pressed state, and therefore the electrode foil 52 and the wiring member 7 are slidable. The electrode foil 41a of the piezo stack 41 and the wiring member 7 are joined by brazing or the like. An insulating sheet (not shown) is interposed between the stack case 48 and the wiring member 7 and between the spacer 49 and the wiring member 7.

  Next, the operation of the fuel injection valve will be described. When the piezo stack 41 is energized and charged with electric charge, the piezo stack 41 extends and the first piston 43 is driven, and the pressure of the liquid chamber 45 is increased by the first piston 43. The second piston 44 is driven toward the valve body 31 side of the control valve 3 by the pressure of the liquid chamber 45 that has been increased in pressure.

  When the valve body 31 is driven by the second piston 44, the valve body 31 comes into contact with the high-pressure side valve seat 18 and the space between the valve chamber 14 and the high-pressure fuel passage 13 is closed. However, the valve chamber 14 and the low pressure fuel passage 16 are opened apart from the low pressure side valve seat 19. Therefore, the fuel in the control chamber 26 is returned to the fuel tank 100 through the communication passage 15, the valve chamber 14, and the low pressure fuel passage 16.

  As a result, the pressure in the control chamber 26 decreases and the force for urging the nozzle needle 21 in the valve closing direction decreases, so that the nozzle needle 21 moves in the valve opening direction and the seat portion 21b moves away from the valve seat 25. The nozzle hole 24 is opened, and fuel is injected from the nozzle hole 24 into the cylinder of the internal combustion engine.

  Thereafter, when the electric charge is discharged from the piezo stack 41, the piezo stack 41 contracts, and the first piston 43 is returned to the piezo stack 41 side by the first spring 46. Further, the valve body 31 and the second piston 44 are returned to the first piston 43 side by the valve spring 32.

  As a result, the valve body 31 is separated from the high-pressure side valve seat 18 to open the space between the valve chamber 14 and the high-pressure fuel passage 13, and the valve body 31 is in contact with the low-pressure side valve seat 19 and The space between the passage 16 is closed. Therefore, the high pressure fuel from the pressure accumulator is introduced into the control chamber 26 through the high pressure fuel passage 13, the valve chamber 14, and the communication passage 15.

  As a result, the pressure in the control chamber 26 rises and the force for urging the nozzle needle 21 in the valve closing direction increases, so that the nozzle needle 21 moves in the valve closing direction and the seat portion 21b sits on the valve seat 25. Thus, the nozzle hole 24 is closed and the fuel injection is completed.

  In this embodiment, since the temperature compensation resistor 5 is housed in the stack case 48, the temperature compensation resistor 5 is not exposed to a high temperature / high pressure environment when the connector is formed, and the temperature compensation resistor 5 is prevented from being broken or deformed. This prevents a resistance value failure.

  Further, a dummy laminate 6 that receives a load in the expansion / contraction direction C of the piezo stack 41 is provided, and the temperature compensation resistor 5 is accommodated in the dummy laminate 6 without receiving a load in the expansion / contraction direction C of the piezo stack 41. Therefore, the temperature compensation resistor 5 can be protected from external force.

  Further, since the electrode 52 of the temperature compensation resistor 5 and the wiring member 7 that connects the electrode 52 to the terminal of the connector are in contact with each other in a slidable state, the contact portion is joined by brazing or the like. Compared with the aspect which is, the stress which generate | occur | produces in a contact part by expansion-contraction etc. of the piezo stack 41 can be made small.

It is sectional drawing which shows typically the whole structure of a fuel-injection apparatus provided with the fuel-injection valve which concerns on one Embodiment of this invention. It is sectional drawing of the actuator 4 of FIG. It is a perspective view of the principal part in the actuator 4 of FIG. FIG. 3 is a view as seen from an arrow A in FIG. 2. It is an expanded sectional view of the B section of FIG.

Explanation of symbols

  2 ... Nozzle, 5 ... Temperature compensation resistor, 41 ... Piezo stack, 48 ... Stack case.

Claims (3)

A piezo stack (41) which is housed in a cylindrical stack case (48) and expands and contracts by charge and discharge of charges;
A temperature compensation resistor (5) for performing temperature compensation of the piezo stack (41);
A nozzle (2) that opens or closes according to the expansion and contraction of the piezo stack (41) and injects fuel when the valve is opened,
The fuel injection valve, wherein the temperature compensation resistor (5) is housed in the stack case (48). A dummy laminate (6) that is stacked and accommodated in the stack case (48) together with the piezo stack (41) and receives a load in the expansion / contraction direction (C) of the piezo stack (41),
The temperature compensation resistor (5) is housed in the dummy laminate (6) without receiving a load in the expansion / contraction direction (C) of the piezo stack (41). The fuel injection valve described. The electrode (52) of the temperature compensation resistor (5) is connected to a connector terminal via a wiring member (7), and the electrode (52) of the temperature compensation resistor (5) and the wiring member (7) slide. The fuel injection valve according to claim 1, wherein the fuel injection valve is in contact in a possible state.

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