JP2006152872A - Valve gear drive device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To securely limit the maximum strokes of valves without increasing production cost, lowering assemblability, and using a mechanical stopper. <P>SOLUTION: In this valve gear drive device of an internal combustion engine, a piston 15 is operated by a fluid pressure to lift open the valves 12 such as an intake valve and an exhaust valve by the piston 15 and the valve 12 is closed by relieving the hydraulic pressure. The valve gear drive device also comprises fluid pressure opening means 13 and 28 for lowering the fluid pressure applied to the piston 15 immediately before the piston 15 reaches the maximum stroke by acting the fluid pressure on the piston 15. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus for opening and closing a valve that forms an intake valve or an exhaust valve of an internal combustion engine, and more particularly, to a valve operating system for an internal combustion engine that does not have a cam mechanism and that uses a fluid pressure to open and close the valve. The present invention relates to a driving device.

  In order to increase the degree of freedom in engine control, a so-called camless type valve drive apparatus that eliminates the valve opening / closing drive by the cam mechanism and uses electromagnetic drive or fluid pressure drive instead is promising. For example, Patent Document 1 discloses such a camless valve drive apparatus. In this device, a piston is connected to the valve, and a high fluid pressure is created to lift the valve by a required amount against the valve spring of the valve. The fluid pressure is applied to the piston, and the valve is opened via the piston. The valve is driven. Therefore, by controlling the supply timing and magnitude of the fluid pressure, the valve opening / closing timing and the lift amount can be freely set.

JP 2003-328713 A

  By the way, in the said apparatus, in order to restrict | limit the maximum stroke of a valve | bulb, the mechanical stopper was provided in the piston or the valve | bulb. However, if a mechanical stopper is provided on the piston or valve, the shape of the piston or valve becomes complicated, resulting in an increase in manufacturing cost and a decrease in assembly. Further, according to the mechanical stopper, there is a problem that sound and impact are generated when the valve reaches the maximum stroke.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a valve drive for an internal combustion engine capable of reliably limiting the maximum stroke of the valve without using a mechanical stopper without causing an increase in manufacturing cost or a decrease in assemblability. To provide an apparatus.

  In order to achieve the above object, the present invention operates a piston by fluid pressure, lifts a valve such as an intake / exhaust valve by the piston, opens the valve, releases the fluid pressure and releases the fluid pressure. In a valve drive apparatus for an internal combustion engine that closes a valve, fluid pressure is applied to the piston, and fluid pressure release means for reducing the fluid pressure applied to the piston immediately before the piston reaches the maximum stroke is provided. It is a thing.

  Here, the piston is slidable in the actuator body and has a cylindrical outer piston provided with a restricted stroke, and is slidable in the outer piston and connected to the valve. And when the valve is opened, fluid pressure is applied to the outer piston and the inner piston to lift the outer piston and the inner piston at the same time, and after the outer piston is stopped, The fluid pressure may be applied only to the inner piston, and the fluid pressure releasing means may release the fluid pressure acting on the inner piston when the inner piston reaches the vicinity of the maximum stroke.

  The fluid pressure release means is provided on the inner peripheral surface of the outer piston, and is a slit that communicates with the space above the inner piston in the outer piston when the inner piston reaches the vicinity of the maximum stroke. You may have.

  According to the present invention, the manufacturing cost is not increased or the assembling property is not lowered, and the maximum stroke of the valve can be surely limited without using a mechanical stopper.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is an overall view of a valve drive apparatus according to an embodiment of the present invention. The valve drive apparatus of this embodiment is applied to a multi-cylinder common rail diesel engine for vehicles and the like.

  First, a common rail fuel injection device will be described.

  An injector 1 that performs fuel injection is provided for each cylinder of the engine (internal combustion engine). The injector 1 is constantly supplied with high-pressure fuel having a common rail pressure Pc (for example, about several tens to several hundreds of MPa) stored in the common rail 2. The fuel in the fuel tank 3 is sucked by the feed pump 5 through the fuel filter 4 and then sent to the high-pressure pump 6. The fuel is fed to the common rail 2 by the high-pressure pump 6. The feed pressure Pf of the feed pump 5 is adjusted by a pressure regulating valve 7 composed of a relief valve and is kept constant. The feed pressure Pf is larger than the normal pressure (that is, the fuel is in a pressurized state), but is significantly smaller than the common rail pressure Pc, for example, about 0.5 MPa.

  An electronic control unit (hereinafter referred to as ECU) 8 is provided as a control device that controls the entire apparatus shown in the figure. The ECU 8 is connected to a sensor (not shown) for detecting the engine operating state (engine crank angle, rotational speed, engine load, etc.). The ECU 8 grasps the operating state of the engine based on the detection signals of these sensors and sends a driving signal based on the operating state to the electromagnetic solenoid of the injector 1 to control the opening and closing of the injector 1. Fuel injection is executed / stopped in response to ON / OFF of the electromagnetic solenoid. When the fuel injection is stopped, the fuel of about normal pressure is returned from the injector 1 to the fuel tank 3 through the return passage 9. The ECU 8 feedback-controls the actual common rail pressure toward the target pressure based on the operating state of the engine. Therefore, a common rail pressure sensor 10 for detecting the actual common rail pressure is provided.

  Next, the valve drive apparatus of this embodiment will be described.

  A valve 12 that forms an intake valve or an exhaust valve of the engine is supported on the cylinder head 11 of the engine so as to be movable up and down. The valve 12 is formed in a shaft shape as a whole, and a valve body 13 is provided at the lower end thereof. When the valve 12 is closed, the valve 12 is seated on the seat portion 14 of the cylinder head 11 by the valve body 13. A piston 15 is provided at the upper end of the valve 12. A valve drive actuator 16 that forms the main part of the present apparatus is provided on the upper portion of the cylinder head 11, and an actuator body 17 is fixed to the upper end of the cylinder head 11. The piston 15 is supported by the actuator body 17 so as to be movable up and down.

  A flange portion 18 is provided in the middle portion of the valve 12 in the longitudinal direction, and a valve spring 19 for biasing the valve 12 in the valve closing direction (upper side in FIG. 1) between the flange portion 18 and the cylinder head 11. Are disposed in a compressed state. The valve spring 19 of the present embodiment is a coil spring. A magnet 20 for attracting the flange portion 18 is embedded in the lower end portion of the actuator body 17, and the valve 12 is also urged by the magnet 20 in the valve closing direction. The magnet 20 of the present embodiment is a ring-shaped permanent magnet that surrounds the valve 12. In FIG. 1, only one valve of one cylinder is shown. However, when it is desired to open and close multiple cylinders or a plurality of valves, the same configuration may be given to the valves.

  As shown in FIGS. 2 and 3, the piston 15 of the present embodiment includes a cylindrical outer piston 21 slidably provided in the actuator body 17, a slidable movement in the outer piston 21, and It is a double piston comprising an inner piston 22 that is integrally connected to the upper end of the valve 12. The outer piston 21 is inserted into an outer piston insertion hole 23 provided in the actuator body 17 while forming a shaft seal. The inner piston 22 is at least the upper end portion of the valve 12 and is inserted into the inner periphery of the outer piston 21 forming the inner piston insertion hole 24 while forming a shaft seal. In the present embodiment, the valve 12 and the inner piston 22 are integrally formed, but they may be configured separately.

  The outer peripheral surface of the lower end portion of the outer piston 21 is enlarged in diameter, and the enlarged diameter portion 25 moves in the oil chamber 26 provided in the actuator body 17 as the outer piston 21 moves. The movement of the outer piston 21 is restricted by the lower end surface of the outer piston 21 coming into contact with the bottom surface of the oil chamber 26. That is, the downward movement of the outer piston 21 is limited within a predetermined range. The maximum stroke of the outer piston 21 is determined by the distance L1 (see FIG. 2) between the lower end surface of the outer piston 21 and the bottom surface of the oil chamber 26 when the valve 12 is closed. The interval L1 is set to a very small value with respect to the entire stroke of the valve 12, and is about 1 mm, for example.

  An outer step portion 27 is provided at the upper end portion of the inner piston insertion hole 24 of the outer piston 21, and an inner step portion 28 for engaging with the outer step portion 27 is provided at the upper end portion of the inner piston 22. At the initial opening and closing of the valve 12, the outer stepped portion 27 and the inner stepped portion 28 are engaged, and the outer piston 21 and the inner piston 22 are moved simultaneously. In the present embodiment, the outer stepped portion 27 and the inner stepped portion 28 are each formed in a tapered shape. Further, the outer stepped portion 27 and the inner stepped portion 28 are set so that the upper end surface 29 of the outer piston 21 and the upper end surface 30 of the inner piston 22 are substantially flush with each other when they are engaged. For example, the diameter of the upper end surface 29 of the outer piston 21 is about 9 mm, and the diameter of the upper end surface 30 of the inner piston 22 is about 2.7 mm.

  A slit 31 is provided at the lower end of the inner piston insertion hole 24 of the outer piston 21 along the axial direction. A plurality of slits 31 (see FIG. 3, four in the illustrated example) are provided at predetermined intervals along the circumferential direction. The slit 31 communicates with the space (inner piston insertion hole 24) above the inner piston 22 in the inner piston insertion hole 24 of the outer piston 21 when the inner piston 22 reaches the vicinity of the maximum stroke. The slit 31 is provided to be separated from the outer stepped portion 27 by a predetermined distance L2. The interval L2 is set to a relatively large value compared to the interval L1, and is about 11 mm, for example.

  Here, immediately before the inner piston 22 reaches the maximum stroke, a fluid pressure releasing means for reducing the fluid pressure applied to the inner piston 22 is provided. In the present embodiment, the inner step portion 28 of the inner piston 22 and the slit 31 of the outer piston 21 mainly constitute the fluid pressure releasing means.

  In the actuator body 17, a pressure chamber 32 facing the upper end surface (pressure receiving surface) 29 of the outer piston 21 and the upper end surface (pressure receiving surface) 30 of the inner piston 22 is provided. The pressure chamber 32 is supplied with a working fluid for lifting the valve 12 in the valve opening direction, and mainly includes an outer piston insertion hole 23 of the actuator body 17 and an inner piston insertion hole 24 of the outer piston 21. The The bottom surface portion of the pressure chamber 32 is defined by pressure receiving surfaces 29 and 30.

  The working fluid of this embodiment uses light oil common to the engine fuel. When fuel is supplied to the pressure chamber 32, the valve 12 is pushed in the valve opening direction via the outer piston 21 and the inner piston 22, and when this pushing force exceeds the urging force of the valve spring 19 and the attractive force of the permanent magnet 20. The valve 12 is opened. On the other hand, when the fuel is discharged from the pressure chamber 32, the valve 12 is closed by the biasing force of the valve spring 19 and the attractive force of the permanent magnet 20. That is, the outer piston 21 and the inner piston 22 are operated by hydraulic pressure, the valve 12 is opened by the outer piston 21 and the inner piston 22, and the hydraulic pressure in the pressure chamber 32 is released to close the valve 12.

  As shown in FIGS. 1 and 4, a first operation valve 33 for switching supply / stop of high-pressure fuel to the pressure chamber 32 is provided on the side of the pressure chamber 32 (left side in FIG. 1). . The first operation valve 33 of the present embodiment is a pressure balance type control valve.

  The first actuating valve 33 has a housing 34 attached to one side (left side in FIG. 1) of the actuator body 17 and a needle-like balance valve 35 slidably provided in the housing 34. . A front end portion 36 of the balance valve 35 is formed in a hemispherical shape, and the front end portion 36 is arranged toward the pressure chamber 32 side. A supply passage 37 is formed on the front end portion 36 side (right side in FIG. 4) of the balance valve 35, and a valve control chamber 38 is formed on the rear end portion side (left side in FIG. 4) of the balance valve 35. The supply passage 37 and the valve control chamber 38 communicate with each other through a communication hole 39 provided in the balance valve 35.

  The supply passage 37 is connected to the common rail 2 as a high-pressure fuel supply source via an external pipe 71, and high-pressure fuel having a common rail pressure Pc is constantly supplied to the supply passage 37. The supply passage 37 faces the distal end portion 36 side of the balance valve 35 and communicates with the pressure chamber 32, and has a valve seat portion 40 in which the distal end portion 36 of the balance valve 35 is in line contact or surface contact. On the upstream side (upper side in FIG. 4) of the valve seat part 40 is an inlet 41 (high-pressure fuel inlet from the common rail 2) of the supply passage 37, and on the downstream side (right side in FIG. 4) of the valve seat part 40. An outlet 42 of the supply passage 37 (an inlet of high-pressure fuel to the pressure chamber 32) is provided.

  The valve control chamber 38 has a shaft-shaped spring holding member having a spring 43 for urging the balance valve 35 in the valve closing direction (right side in FIG. 4) and a flange 44 for holding the spring 43. 45 is provided. The flange portion 44 of the spring holding member 45 is provided with a communication groove 46 for communicating both ends. The spring 43 of the present embodiment is a coil spring, and is disposed in a compressed state between the balance valve 35 and the flange portion 44 of the spring holding member 45.

  The valve control chamber 38 communicates with the return passage 9 through an orifice 47 that is an outlet of fuel. An armature 48 as an on-off valve for opening and closing the orifice 47 is movably provided on the side of the orifice 47. On the side of the armature 48, an electromagnetic solenoid 49 as an electric actuator for moving the armature 48 in the valve opening direction (left side in FIG. 4) and the armature 48 in the valve closing direction (right side in FIG. 4). An armature spring 50 for biasing and a shaft-shaped armature spring holding member 52 having a flange 51 for holding the armature spring 50 are provided. The armature spring holding member 52 has a communication hole (not shown) that allows the valve control chamber 38 and the return passage 9 to communicate with each other. The armature spring 50 of this embodiment is a coil spring, and is disposed in a compressed state between the armature 48 and the flange portion 51 of the armature spring holding member 52. The electromagnetic solenoid 49 is connected to the ECU 8 and is ON / OFF controlled by a drive signal supplied from the ECU 8.

  Normally, when the electromagnetic solenoid 49 is OFF, the armature 48 is pressed in the valve closing direction by the armature spring 50, and the orifice 47 is closed. Therefore, the high-pressure fuel acts on the back surface 53 and the valve control chamber 38 that form the pressure receiving surface of the spring holding member 45 and the front surface 54 that forms the pressure receiving surface of the balance valve 35. At this time, since the area of the pressure receiving surface 53 of the spring holding member 45 is larger than the area of the pressure receiving surface 54 of the balance valve 35, the spring holding member 45 presses the balance valve 35 against the valve seat portion 40 via the spring 43. . Accordingly, the outlet 42 of the supply passage 37 is closed by the balance valve 35.

  On the other hand, as shown in FIG. 5, when the electromagnetic solenoid 49 is turned on, the armature 48 is moved in the valve opening direction against the urging force of the armature spring 50, and the orifice 47 is opened. When this happens, part of the high-pressure fuel supplied into the valve control chamber 38 is discharged to the return passage 9 through the orifice 47. Accordingly, the balance valve 35 is moved in the valve opening direction against the biasing force of the spring 43, and the outlet 42 of the supply passage 37 is opened. As a result, the common rail 2 communicates with the pressure chamber 32 via the supply passage 37, and high-pressure fuel is instantaneously and vigorously supplied from the common rail 2 to the pressure chamber 32.

  As shown in FIGS. 1 and 6, above the pressure chamber 32 (upper side in FIG. 1), supply / stop of supply of low-pressure fuel to the pressure chamber 32 and discharge of high-pressure fuel from the pressure chamber 32 are switched. The second operating valve 55 is provided. The second operating valve 55 of the present embodiment is a mechanical check valve.

  The second operating valve 55 includes a supply passage 56 provided in the actuator body 17. The supply passage 56 is connected to a low pressure chamber 57 (see FIG. 1) as a low pressure working fluid supply source via an external pipe 72. The low pressure chamber 57 is connected to a feed passage 58 (see FIG. 1) upstream of the pressure regulating valve 7 and upstream of the high pressure pump 6, and low pressure fuel having a feed pressure Pf is always introduced and stored from the feed passage 58. .

  The supply passage 56 is provided with a bottomed cylindrical valve holding member 59. The valve holding member 59 is arranged with the bottom thereof facing the pressure chamber 32. An orifice hole 60 (see FIG. 6) that communicates both ends is provided at the bottom of the valve holding member 59. A valve body 61 is provided at the bottom of the valve holding member 59 so as to be movable up and down.

  The valve body 61 is formed in a shaft shape as a whole, and an umbrella valve portion 62 is formed at a lower end portion (lower side in FIG. 6), and a flange portion 63 is formed at an upper end portion (upper side in FIG. 6). Is provided. The upper end portion of the umbrella valve portion 62 is seated on the seat portion 64 formed at the upper end portion of the pressure chamber 32.

  A first return spring 65 is provided in the valve holding member 59. The first return spring 65 of this embodiment is a coil spring. The first return spring 65 has a relatively small set force and spring constant, and is disposed in a compressed state between the flange 63 of the valve body 61 and the valve holding member 59. Thereby, the valve body 61 is always biased in the valve closing direction (upper side in FIG. 6).

  An electric actuator (for example, an electromagnetic actuator) 66 for forcibly opening the second operating valve 55 is provided. A rod 67 is movably connected to the electric actuator 66 in the axial direction, and a bottomed cylindrical spring seat 68 is attached to the tip of the rod 67 at the bottom. A second return spring 69 is provided in the valve holding member 59. The second return spring 69 of this embodiment is a coil spring. The second return spring 69 has a relatively large set force and spring constant, and is disposed between the spring seat 68 and the valve holding member 59 in a compressed state. Thereby, the spring seat 68 is always urged in the valve closing direction of the valve body 61. The electric actuator 66 is connected to the ECU 8 and is ON / OFF controlled by a drive signal given from the ECU 8.

  A third operating valve 70 (see FIG. 1) is connected to the supply passage 56 via the electric actuator 66. The third actuating valve 70 of this embodiment is a mechanical check valve. The third operating valve 70 has an inlet side connected to the supply passage 56 and an outlet side connected to the feed passage 58. The third operating valve 70 is opened based on the pressure difference between the inlet side and the outlet side, and is opened only when the pressure on the inlet side becomes a predetermined pressure higher than the pressure on the outlet side.

  Here, the valve opening set pressure of the third operating valve 70 is slightly higher than the feed pressure Pf and significantly lower than the common rail pressure Pc. Therefore, even if low pressure fuel exists on the inlet side of the third operating valve 70, the third operating valve 70 does not open. However, if high pressure fuel exists on the inlet side of the third operating valve 70, the third operating valve 70 immediately Open the valve.

  First, when the valve 12 is opened, the electric actuator 66 is held OFF, and the first operation valve 33 is opened for a predetermined period at the beginning of opening of the valve 12. Then, the high pressure fuel is supplied from the common rail 2 to the pressure chamber 32 via the first operation valve 33. The high pressure fuel pushes the pressure receiving surface 29 of the outer piston 21 and the pressure receiving surface 30 of the inner piston 22, thereby giving initial energy to the valve 12. The valve 12 is moved under inertia under the condition that the urging force of the valve spring 19 and the attractive force of the magnet 20 act, and is lifted downward. During the inertial movement of the valve 12, the volume of the pressure chamber 32 gradually increases, and the pressure in the pressure chamber 32 becomes lower than the pressure in the supply passage 56 (that is, the pressure in the low pressure chamber 57).

  In this case, as shown in FIG. 7, the valve element 61 of the second operating valve 55 opens against the urging force of the first return spring 65 due to the pressure difference between the pressure chamber 32 and the low pressure chamber 57. Moved to the valve side, the second operating valve 55 is opened. As a result, the low pressure fuel in the low pressure chamber 57 is introduced into the pressure chamber 32 via the supply passage 56. That is, the pressure chamber 32 is replenished with fuel so as to compensate for the increase in volume.

  On the other hand, when the valve 12 is closed, the first operation valve 33 is held closed and the electric actuator 66 is turned on. Then, as shown in FIG. 8, the valve body 61 of the second operating valve 55 is pushed to the valve opening side by the spring seat 68, and the second operating valve 55 is forcibly opened. As a result, the high-pressure fuel in the pressure chamber 32 passes through the supply passage 56 and the electric actuator 66 to the inlet side of the third operating valve 70, pushes the third operating valve 70 open, and is discharged to the feed passage 58. Since the valve opening set pressure of the third operating valve 70 is set to a value lower than the pressure of the high-pressure fuel, that is, the common rail pressure Pc, the third operating valve 70 is naturally opened. As a result, the pressure in the pressure chamber 32 is lowered, and the valve 12 is raised by the urging force of the valve spring 19 and the attractive force of the magnet 20, that is, moved in the valve closing direction.

  Next, the operation of the slit 31 which is a characteristic part of the present embodiment will be described.

  As shown in FIG. 9A, when high pressure fuel is supplied to the pressure chamber 32 to open the valve 12, the high pressure fuel is separated from the pressure receiving surface 29 of the outer piston 21 and the pressure receiving surface 30 of the inner piston 22. Act on. Therefore, at the initial stage of valve opening, the outer piston 21 and the inner piston 22 are simultaneously lifted, and the valve 12 is lifted in the valve opening direction by the outer piston 21 and the inner piston 22. At that time, fuel is present in the oil chamber 26, but its hydraulic pressure is smaller than the common rail pressure Pc, for example, about 1 MPa or less. Therefore, even if fuel is present in the oil chamber 26, the outer piston 21 is lifted. Note that a leak passage for discharging part of the fuel in the oil chamber 26 may be connected to the oil chamber 26.

  Next, as shown in FIG. 9B, when the outer piston 21 and the inner piston 22 lift until the lower end surface of the outer piston 21 comes into contact with the bottom of the oil chamber 26, the lifting of the outer piston 21 is stopped. . After the outer piston 21 stops, the high-pressure fuel acts on the pressure receiving surface 30 of the inner piston 22, only the inner piston 22 is lifted, and the valve 12 is further lifted in the valve opening direction by the inner piston 22.

  Next, as shown in FIG. 9C, when the inner piston 22 is lifted so that the inner step portion 28 of the inner piston 22 is located below the upper end of the slit 31 of the outer piston 21, the vicinity of the maximum stroke is reached. The inner piston insertion hole 24 constituting a part of the pressure chamber 32 is communicated with the slit 31. When this happens, part of the high-pressure fuel supplied into the pressure chamber 32 tends to flow into the slit 31. That is, a part of the hydraulic pressure acting on the inner piston 22 is released. Accordingly, the hydraulic pressure acting on the inner piston 22 decreases, and the force pushing the valve 12 decreases. At this time, since the inner piston 22 is lifted by the inertial motion due to the initial energy of the high-pressure fuel supply, the energy of the inertial motion is smaller at the end of the valve opening than at the beginning of the valve opening. Therefore, combined with the biasing force of the valve spring 19 and the attractive force of the magnet 20, the lift of the inner piston 22 (valve 12) is stopped.

  Thus, in this embodiment, the slit 31 is provided at the lower end portion of the inner piston insertion hole 24 into which the inner piston 22 is inserted, and the inner piston insertion hole 24 (pressure chamber) immediately before the inner piston 22 reaches the maximum stroke. 32) and the slit 31 are configured to communicate with each other. Thereby, since the maximum stroke of the valve 12 is controlled, the structures of the outer piston 21, the inner piston 22 and the valve 12 can be kept simple, and the assembly thereof can be facilitated. Further, in this embodiment, since no mechanical stopper is provided to control the maximum stroke of the valve 12, no sound or impact is generated.

  On the other hand, as shown in FIG. 10A, when the high pressure fuel in the pressure chamber 32 is discharged to close the valve 12, the valve 12 is lifted by the biasing force of the valve spring 19 and the attractive force of the magnet 20. Then, the inner piston 22 connected to the upper end portion of the valve 12 is moved in the valve closing direction.

  Next, as shown in FIG. 10B, when the inner piston 22 is moved until the inner step portion 28 of the inner piston 22 is engaged with the outer step portion 27 of the outer piston 21, the inner piston 22 is moved. The outer piston 21 is pushed. Thereby, the outer side piston 21 and the inner side piston 22 are moved simultaneously.

  Next, when the valve body 13 of the valve 12 is seated on the seat portion 14 of the cylinder head 11 as shown in FIG. 1, the movement of the outer piston 21 and the inner piston 22 is stopped as shown in FIG. The Thereafter, the electric actuator 66 is turned off and the second operation valve 55 is closed. Thereby, the valve 12 is held in the closed state again.

  By the way, the piston 15 of this embodiment is a double piston composed of an outer piston 21 and an inner piston 22, and only the inner piston 22 moves for a predetermined period from the initial stage of valve closing, and the outer piston 21 at the end of valve closing. And the inner piston 22 are configured to move simultaneously. Accordingly, the pressure receiving area of the piston 15 as a whole increases at the end of valve closing, whereby the valve closing speed is reduced, and the seating impact force when the valve body 13 of the valve 12 is seated on the seat portion 14 of the cylinder head 11 is reduced. can do. By doing in this way, it becomes possible to reduce seating sound and wear of the seat part 14.

  In addition, in this embodiment, the outer piston 21 and the inner piston 22 move simultaneously at the initial stage of valve opening, and only the inner piston 22 moves after the outer piston 21 stops. Therefore, even in the initial stage of valve opening, the pressure receiving area of the entire piston 15 is large, the valve opening speed is increased, and the response delay can be shortened. In this case, it is necessary to increase the initial energy of the high-pressure fuel supply with an increase in the pressure receiving area in the initial stage of valve opening. However, in this embodiment, the stroke of the outer piston 21 is limited so as to be extremely small. The increase is minimized. By doing so, it is possible to control the valve 12 precisely in the intake and exhaust strokes.

  The present invention is not limited to the embodiment described above.

  For example, in the above embodiment, the slits 31 are provided straight along the axial direction, but the slits 31 may be provided spirally in the axial direction.

  Further, in the above embodiment, the slit 13 is provided at the lower end portion of the outer piston 21, but it is only required to be separated from the outer step portion 27, and the slit 31 is provided above the lower end portion of the outer piston 21. It may be done.

  In the above-described embodiment, the piston 15 is a double piston composed of the outer piston 21 and the inner piston 22, but the piston 15 may be a single piston provided by being connected to the upper end of the valve 12. In that case, a piston insertion hole for slidably supporting the single piston may be provided in the actuator body 17 and a slit 31 may be provided at the lower end of the piston insertion hole.

  Further, as shown in FIG. 11, in order to facilitate fluid pressure release, the slit 31 and the oil chamber 26 are communicated with the lower end surface of the outer piston 21 when the outer piston 21 reaches the maximum stroke. In addition to providing the groove 81, a groove 82 for communicating the slit 31 and the oil chamber 26 when the outer piston 21 reaches the maximum stroke may be provided on the bottom surface of the oil chamber 26. In this case, when the inner piston 22 is lifted so that the inner step portion 28 of the inner piston 22 is positioned below the upper end of the slit 31 of the outer piston 21, the inner portion constituting a part of the pressure chamber 32 near the maximum stroke. The piston insertion hole 24 communicates with the oil chamber 26 through the slit 31 and the grooves 81 and 82. When this happens, part of the high-pressure fuel supplied into the pressure chamber 32 is released to the oil chamber 26. Only one of the groove 81 of the outer piston 21 and the groove 82 of the oil chamber 26 may be provided.

  Further, instead of the slit 31, as shown in FIG. 12, a communication hole 83 to the oil chamber 26 may be provided in the outer piston 21. For example, the communication hole 83 is provided above the enlarged diameter portion 25 of the outer piston 21. A plurality (for example, about three to four) of the communication holes 83 are provided at predetermined intervals in the circumferential direction. In this case, when the inner piston 22 is lifted so that the inner step portion 28 of the inner piston 22 is positioned below the communication hole 83 of the outer piston 21, the inner portion constituting a part of the pressure chamber 32 in the vicinity of the maximum stroke. The piston insertion hole 24 communicates with the oil chamber 26 via the communication hole 83. When this happens, part of the high-pressure fuel supplied into the pressure chamber 32 is released to the oil chamber 26. The communication hole 83 may be provided in the enlarged diameter portion 25 of the outer piston 21.

  In the above embodiments, the working fluid is engine fuel (light oil), but the working fluid may be ordinary oil or the like.

  In the above embodiment, the high-pressure fuel is the fuel having the common rail pressure Pc and the low-pressure fuel is the fuel having the feed pressure Pf. However, the high-pressure fuel and the low-pressure fuel may be separately produced by a hydraulic device. However, in the case of a common rail diesel engine, since high pressure fuel and low pressure fuel are originally produced, it is desirable to use them as in the above embodiment because the configuration is simple and low cost.

  In the above embodiment, the valve spring 19 and the magnet 20 are used in combination to urge the valve 12 in the valve closing direction. However, only the valve spring 19 or only the magnet 20 may be used alone.

  Furthermore, the engine to which the valve drive device of the present invention is applied is not limited to a common rail diesel engine, but may be a normal injection pump diesel engine or a gasoline engine.

1 is an overall view of a valve drive apparatus according to an embodiment of the present invention. It is sectional drawing of a piston. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. It is principal part sectional drawing of a 1st action valve, and an electromagnetic solenoid is a state of OFF. It is principal part sectional drawing of a 1st action valve, and is a high voltage | pressure supply state. It is principal part sectional drawing of a 2nd operating valve, and an electric actuator is a state of OFF. It is principal part sectional drawing of a 2nd operating valve, and is a low voltage | pressure supply state. It is principal part sectional drawing of a 2nd operating valve, and is a high pressure discharge state. (A)-(c) is the schematic which shows the operating state of the piston at the time of valve opening. (A)-(c) is the schematic which shows the operating state of the piston at the time of valve closing. It is the schematic which shows the modification of a piston. It is the schematic which shows the modification of a piston.

Explanation of symbols

12 valve 15 piston 17 actuator body 21 outer piston 22 inner piston 28 inner step (fluid pressure release means)
31 Slit (fluid pressure release means)

Claims (3)

  A valve drive apparatus for an internal combustion engine that operates a piston by fluid pressure, lifts a valve such as an intake / exhaust valve by the piston, opens the valve, and releases the fluid pressure to close the valve. A valve drive for an internal combustion engine comprising fluid pressure releasing means for applying fluid pressure to the piston and reducing the fluid pressure applied to the piston immediately before the piston reaches the maximum stroke apparatus.   The piston is slidable in the actuator body and has a cylindrical outer piston provided with a regulated stroke, and is slidable in the outer piston and connected to the valve. When the valve is opened, fluid pressure is applied to the outer piston and the inner piston to lift the outer piston and the inner piston at the same time, and after the outer piston stops, the inner piston 2. The operation of the internal combustion engine according to claim 1, wherein when the fluid pressure is applied only to the inner piston and the inner piston reaches the vicinity of the maximum stroke, the fluid pressure releasing means releases the fluid pressure acting on the inner piston. Valve drive device. The fluid pressure release means is provided on the inner peripheral surface of the outer piston, and has a slit that communicates with the space above the inner piston in the outer piston when the inner piston reaches the vicinity of the maximum stroke. The valve drive apparatus for an internal combustion engine according to claim 2.

Images