WO2009121647A1

WO2009121647A1 - Hydraulic damping means

Info

Publication number: WO2009121647A1
Application number: PCT/EP2009/051218
Authority: WO
Inventors: Matthias Burger; Hans-Christoph Magel
Original assignee: Robert Bosch Gmbh
Priority date: 2008-04-02
Filing date: 2009-02-04
Publication date: 2009-10-08
Also published as: DE102008000929A1

Abstract

The invention relates to a solenoid valve (16) for a fuel injector (10) for actuating an injection-valve element (26) by pressure relief of a control chamber (24). The control chamber (24) is loaded with fuel which is at system pressure. The solenoid valve (16) comprises a valve element (46) which opens or closes a valve seat (42). A hydraulic connection (72; 74, 76, 78) which generates a force which assists the respective movement of the valve element (46) and acts on the valve element (46) runs between a low-pressure volume (68) and a valve chamber (70).

Description

March 26, 2008

description

title

Hydraulic damping

State of the art

In the development of internal combustion engines, compliance with the emission limits has the highest priority. Especially the common-rail injection system has made a decisive contribution to the reduction of pollutant emissions. The advantage of the high-pressure accumulator injection system (common rail) lies in the independence of the injection pressure of the speed and load of the internal combustion engine. However, in the case of self-igniting internal combustion engines, a significant increase in the injection pressure is necessary for compliance with future exhaust gas limit values. Latest injectors for highest injection pressures are leak-free, by dispensing with a low-pressure stage. Due to the absence of this low-pressure stage, only low closing forces are available for actuating the injection valve member, which is generally needle-shaped. This leads to steep maps and thus to a poor Kleinstmengenfähigkeit so designed fuel injectors.

This disadvantage can be compensated by fast-switching valves, such as fast-switching solenoid valves. With fast-switching valves, however, there is the problem that characteristic ripples occur due to bumping. Under bouncing unintentional relegation of the valve seat is understood by the higher impact energy striking the valve seat closing element and a due to the elasticity of the materials occurring rebounding in the opening direction. The bouncing of the valve member occurs in particular in hard running stroke stops in metal / metal contact in conjunction with a fast-switching valve needle of a fuel injector solenoid valve. In order to dampen the hard impact of the valve needle in the valve seat or the hard impact of the closing element in the valve seat, crimp gaps are nowadays carried out in order to reduce the impact energy by hydraulic means. But squish gaps have the negative property that when closing the valve needle, a hydraulic force occurs, which delays just this closing. This effect is called hydraulic gluing. The hydraulic bonding is of external influences such as Example pressure and temperature dependent and therefore leads to variations from hub to hub. Preller appear not only when opening, but also when closing the valve needle in appearance. These buffers have a particularly negative influence on the injector function and generally lead to large stroke to Hub- scattering and thus to an unfavorable reproducibility of injection quantities.

Unlike an upper stroke stop, for example, on a stop sleeve in the magnetic core, due to its sealing function no nip can be performed on the valve seat. A high stop impulse of the valve needle in the valve seat not only leads to bumping when closing, but also to a significantly increased valve seat wear.

Disclosure of the invention

As a result of the solution proposed according to the invention, in the case of a solenoid valve for actuating a fuel injector, the bouncing when closing on the valve seat is eliminated by a hydraulic counterforce. Furthermore, an acceleration of the valve movement takes place during the opening phase, which brings about short switching times, for example between the main injection phase and one of the main injection phase with a time-closely upstream pilot injection. The Absteuermenge, which is controlled when opening the valve seat from the control chamber, is redirected via a hydraulic line such that at the time of valve opening, an overpressure in a low pressure volume and at the time of valve closing a negative pressure in this low pressure volume is generated. This differential pressure, i. the overpressure or the negative pressure is used to exert an additional hydraulic force on the valve or the valve member of the solenoid valve, which is usually shaped like a needle. The differential pressure is due to the inertia of the hydraulic fluid, i. of the fuel, in the hydraulic line that opens into the valve chamber.

The hydraulically generated, acting in the opening direction of the valve member hydraulic force arises at the time of opening and leads to an additional acceleration of the valve member of the solenoid valve, which leads to faster switching operations. When closing the valve member of the solenoid valve, however, creates a closing supporting hydraulic force. The main advantage of the additional closing force resulting from closing is the prevention of mechanical bounce. At the time of closing, a greater force is exerted on the armature and thus on the valve member in the closing direction, compared with the force acting on the valve member or the armature during the closing movement. This is the decisive advantage of the proposed solution according to the invention, since a mechanical bouncing with a mere increase in the spring force the closing spring acting in the closing direction can not be prevented. By the solution proposed by the invention, the mechanical bouncing is counteracted by a greater closing force acts on the armature at the time of closing of the valve member than during the running in the direction of the valve seat closing movement.

In an advantageous embodiment of the invention underlying idea flows when opening the armature, and thus the valve member, Absteuermenge from the control chamber via a drain channel with at least one outlet throttle in a high-pressure volume in front of the valve seat and a Absteuerleitung in a low pressure volume, which is behind the Valve seat is located. The diversion line is advantageously designed as a bore and designed by its length / width ratio so that the function of a hydraulic line is given. On the one hand, this hydraulic line can be formed as a bore in a sleeve delimiting the high-pressure volume in front of the valve seat in the valve piece, and on the other hand as a bore having a long line length in a plurality of sections in the valve piece.

About this hydraulic line, which can be displayed in the two variants outlined above, arises at the time of opening of the valve member in the low pressure volume overpressure, since the hydraulic fluid is accelerated in the diversion line. The overpressure generates a force acting in the opening direction on the valve member, so that its switching time is reduced in an advantageous manner. The overpressure in the diversion line is only present for a short time until a stationary flow has set within the diversion line.

When closing the valve member, the Absteuermenge deducted from the control room is abruptly reduced and the flow in the hydraulic line breaks down. Due to the transient behavior of the hydraulic fluid within the diversion line, a low pressure is impressed on the low-pressure volume downstream of the valve seat. This is due to the fact that the low pressure volume is "sucked out" due to the inertia of the fluid flowing through the spill line and the negative pressure acts on the valve member or armature acting as a closing force, thereby preventing mechanical valve bouncing The period of time during which the differential pressure acts, be it the overpressure or the negative pressure, depends on the length of the hydraulic line, which is in. short duration, so that the solenoid valve is again pressure-balanced or hydraulically non-powered opens the valve chamber.

Brief description of the drawings -A-

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

It shows:

1 shows a solenoid valve whose low-pressure volume is connected via a hydraulic line in a first embodiment with a valve chamber,

Figure 2 shows a solenoid valve whose low pressure volume is connected via a hydraulic line in a second embodiment with a valve chamber, and

Figure 3 shows a further constructive variant in which the Absteuerleitung is realized via a sleeve.

embodiments

As can be seen from the illustration according to FIG. 1, a fuel injector 10 comprises an injector body 12 which is constructed symmetrically with respect to the injector axis 14. A solenoid valve 16 is integrated in the fuel injector 10. The injector body 12 of the fuel injector 10 is acted upon by a high pressure port 18 with fluid under a system pressure, preferably fuel. The system pressure with which the fuel is present at the high-pressure port 18 of the injector body 12 of the fuel injector 10 is generated in a high-pressure accumulator body (common rail), for example via a hydraulic pump. Reference numeral 20 denotes a return port, which is located above the solenoid valve 16 of the fuel injector 10.

The fuel injector 10 comprises a valve piece 22, which is fastened by means of a screwed in the interior of the injector body 12 valve clamping nut 36 in this. In the valve piece 22, a control chamber 24 is formed. The control chamber 24 is pressure-relieved via a drain passage 30, in which at least one outlet throttle 32 is received. On the other hand, the control chamber 24 is supplied with fuel via an inlet throttle 34 from a high-pressure volume 38, which is supplied by fuel under system pressure, coming from the high-pressure port 18.

The control chamber 24 acts on an upper end face of a generally needle-shaped injection valve member 26. The injection valve member 26 is guided in the injector body 12 of the fuel injector 10. The injection valve member 26 is at the combustion chamber end the Kraftstoffϊnjektors 10 - not shown in Figure 1 - injection openings freely, via which with open injection valve member 26 of the fuel under system pressure from the high pressure volume 38 flows to the open injection ports at the combustion chamber end of the fuel injector 10.

The valve member 22 shown in Figure 1 comprises a flat surface 40 in which a valve seat 42 is executed. The valve seat 42 is designed in the embodiment shown in Figure 1 as a flat seat. The valve seat 42 is closed by a valve member 46, which is located below an armature 48. The valve seat 42 is located at the discharge point of the discharge channel 30 for pressure relief of the control chamber 24, wherein the drainage channel 30 comprises at least one outlet throttle 32.

Above the plane surface 40 is a guide body 44, in which the valve member 46 is guided with a valve needle 52, which serves to position it. On the other hand, the valve member 46 is guided below the armature 48 via a high pressure-tight guide 50 to a pressure pin 54.

The valve member 46 and the armature 48 are acted upon by a closing spring 56 which places the valve member 46 in the valve seat 42 formed on the flat surface 40 of the valve member 22.

The solenoid valve 16, which is located above the armature 48, comprises a magnet group 58, a magnetic core 60 and a magnetic coil 62 embedded therein. At the upper side of the armature 48 facing the magnetic coil 32 is a disc-shaped upper stroke stop 64.

In addition to the control chamber 24 already mentioned, the fuel injector 10 comprises further hydraulic spaces. In addition to the control chamber 24, this includes a high-pressure volume 66, which is located behind the valve seat 42, limited by the inside of the valve member 46. Furthermore, between the outer circumferential surface of the valve member 46 and the inside of the guide body 44, a low pressure volume 68 behind the valve seat 42. This is about a in the illustrations according to Figures 1 and 2 in two different embodiments procured Absteuerleitung 72 with a valve chamber 70 with connection to the return 20 hydraulically connected.

As can be seen from the illustration according to FIG. 1, the diversion line 72 between the low-pressure volume 68 and the valve space 70 can be designed as a bore passing through the guide body 44 in the radial direction. Alternatively, according to FIG. 2, it is possible to design the diversion line 72 as one or more sections 74, 76 in the valve piece 24. In this variant of the diversion line 72 with a first section 74 and a second section 76, longer line lengths can be represented. The length of the hydraulic line, the Absteuerleitung 72, which opens into the valve chamber 70, determines the period during which the differential pressure, whether it is overpressure or negative pressure, is present in the low-pressure volume 68.

The operation of the fuel injectors 10 shown in Figures 1 and 2 is as follows: The armature 48 of the solenoid valve 16 is the same pressure balanced in the closed state, which means that act on the armature 48 no pressure forces. This is achieved in that the sealing edge of the valve seat 42 acts on the same diameter as the high pressure-tight guide 50. The pressure force is thus absorbed via the pressure pin 54, on which the valve member 46 is guided.

Upon energization of the solenoid 62 of the solenoid valve 16, the armature 48 opens, so that Absteuermenge flows from the control chamber 24 via the drain passage 30, in which at least one outlet throttle 32 is provided, flows through the high pressure volume 66 in the low pressure volume 68. The low-pressure volume 68 is hydraulically connected via the diversion line 72 to the valve space 70. The diversion line 72, which according to FIG. 1 may be formed as a bore in the guide body 44, is designed by its length / width ratio such that it assumes the function of a hydraulic line. The illustration according to FIG. 2 shows the embodiment of the diversion line 72 in the valve piece 22. Due to the dynamics of the flow in the diversion line 72, an excess pressure arises at the time of opening the valve member 46 in the low-pressure volume 68. This increase in pressure is due to the fact that the hydraulic fluid in the diversion line 72 is accelerated. The overpressure creates a force acting in the opening direction on the valve member 46, which shortens the switching time of the valve member 46 in an advantageous manner. The overpressure is only present for a short time until a stationary flow has formed within the diversion line 72. This is dependent on the length of the diversion line 72 or its line sections 74 and 76, respectively, as shown in the embodiment variant according to FIG.

When closing the solenoid valve 16, however, is closed by the closing of the valve seat 42 by the valve member 46, the amount diverted from the control chamber 24 abruptly reduced, so that the flow in the Absteuerleitung 72 abruptly stops. Due to the transient behavior of the flow within the diversion line 72 - this applies to both variants - now arises in the low pressure volume 68, a negative pressure. The negative pressure results from the fact that the low-pressure volume 68 is "sucked out" due to the inertia of the hydraulic fluid flowing through the discharge line 72. The negative pressure arising in the low-pressure volume 68 acts on the armature 48 or on the valve member 46 as a force acting in the closing direction Occurring force prevents the mechanical bouncing of the valve member 46, ie its unintentional leaving the valve seat 42. Also, this pressure difference, which supports the force acting in the closing direction, is only of short duration, so that the solenoid valve 16 after a short time again pressure balanced, respectively works hydraulically without force.

The illustration according to FIG. 3 shows a further structural design of the fuel injector proposed according to the invention, in which the diversion line is designed in an integrated sleeve.

In the embodiment shown in Figure 3 is located above the valve member 22 also the guide body 44, in which, however, according to this embodiment, a sleeve 80 is integrated. The integrated sleeve 80 has an upper surface 82 which is arranged in a concave contour 84. The concave contour 84 at the top 82 of the integral sleeve 80 provides the advantage that the compressive forces on the entire anchor surface, i. act on the entire underside of the armature 48 and thereby creates a larger force. The concave contour 84 on the upper side 82 of the integrated sleeve 80 also causes the flow cross-section 86, as seen in the radial direction, can be kept substantially constant. In the illustration according to FIG. 3, it is shown that a positioning of the armature 48 instead of the valve needle guide 72 shown in FIG. 1 is realized in the guide body 44, here via a polygonal guide 88 which is attached to the integrated sleeve 80. On the other hand, it is shown in the illustration according to FIG. 3 that the valve member 46, or the armature 48, is comprised without contact. In this embodiment, the valve needle guide 52 shown in connection with Figure 1 is omitted within the guide body 44 above the valve member 22. The positioning of the armature 48, or the valve member 46 is taken over by the high pressure-tight guide 50 on the pressure pin 54.

Moreover, it can be seen from the illustration according to FIG. 3 that the injector body 12 comprises the injector body 12 analogously to the variants of embodiment already discussed above in connection with FIGS. 1 and 2. This is formed symmetrically with respect to the injector axis 14 and comprises the solenoid valve 16. The injector body 12 of the fuel injector 10 is acted upon by the fuel under system pressure via the high-pressure port 18. The fuel is via a return port 20 in the upper Area of the fuel injector 10 is returned to a low pressure region of the fuel injection system.

The fuel injector 10 comprises the valve piece 22 in which the control space 24, which is acted upon by fuel under system pressure, is formed. The pressure prevailing in the control chamber 24 pressure level acts on an upper end face of a preferably needle-shaped injection valve member 26. The pressure relief of the control chamber 24 via the outlet channel 30, in which there is at least one outlet throttle 32. The pressurization of the control chamber 24 via a high-pressure volume 38 within the injector body 12 and at least one inlet throttle, compare position 34. The valve member 22 is screwed by means of a valve clamping nut 36 in the interior of the injector body 12 and placed against a shoulder thereof. In the valve piece 22, the preferably needle-shaped injection valve member 26 is guided, wherein the valve member 22, the injection valve member 26 enclosing, a closing spring 28 is supported. This is, supported by the system pressure prevailing in the control chamber, the preferably needle-shaped injection valve member 26 in its running at the combustion chamber end of the fuel injector 10 - in Figure 3, however, not shown - seat.

The valve piece 22 comprises the upper planar surface 40, in which the valve seat 42 is executed. The valve seat 42 is also in the embodiment shown in Figure 3 as a flat seat, but could also be a conical seat or a ball seat or the like. The valve seat 42 is located at the discharge point of the discharge channel 30 below the valve member 46. A- analogy to the illustrations according to Figures 1 and 2, the valve member 46 which is attached to the underside of the armature 48, in the high-pressure-tight guide 50 on the pressure pin 54th guided. In contrast to the embodiment according to FIG. 1, the valve needle guide 52 for positioning the valve member 46 in the guide body 44 is omitted. This function has been taken over by the integrated sleeve 80, the upper side 82 of which - as shown in FIG. 3 - has the concave contour 84, which makes possible a flow cross-section 86 for the hydraulic fluid which is essentially constant in the radial direction.

As shown in FIG. 3, the magnetic valve 16 comprises the magnet group 58, the magnetic core 60 and the magnet coil 62. On the upper plan side of the armature 48 is the upper stroke stop 64, which is disc-shaped analogous to the embodiment of Figure 1. Above the valve seat 42, enclosed by the valve member 46, the high-pressure volume 66 is located when the valve member 46 is closed, which is connected to the low-pressure volume 68 when the solenoid valve 16 is opened. The hydraulic connection between the low-pressure volume 68 and the valve space 70 takes place in the embodiment according to FIG. 3 via the upper side 82 of the integrated sleeve 80. current discharge line 72, whose flow cross-section is characterized in the radial direction by position 86.

Claims

claims

1. A solenoid valve (16) for a fuel injector (10) for actuating an injection valve member (26) by depressurizing a control chamber (24), which is acted upon by a system pressure fuel, with a valve member (46) having a valve seat (42). opens or closes, characterized in that between a low-pressure chamber (68) and a valve chamber (70) extends a hydraulic connection (72; 74, 76, 86) which supports the respective movement of the valve member (46) on the valve member (70) 46) generates acting force.

2. Solenoid valve according to claim 1, characterized in that the valve member (46) in a high-pressure-tight guide (50) pressure balanced on a pressure pin (54) and guided by a low-pressure volume (68) limiting the guide body (44) is enclosed.

3. Solenoid valve according to claim 2, characterized in that the hydraulic connection (72) extends through the guide body (44).

4. Solenoid valve according to claim 2, characterized in that the hydraulic connection (72) extends in a valve piece (22) which delimits the control chamber (24).

5. Solenoid valve according to claim 4, characterized in that the hydraulic connection (72) in the valve piece (22) has at least one extended line section (74, 76).

6. Solenoid valve according to claim 1, characterized in that the valve piece (22) has a valve member (46) surrounding, integrated sleeve (80).

7. Solenoid valve according to claim 6, characterized in that the guide body (44) with integrated sleeve (80) on the armature (48) facing side has a concave contour (84).

8. Solenoid valve according to claim 6, characterized in that the valve member (46) in the integrated sleeve (80) either without contact or in a polygonal guide (88) is guided.

9. Solenoid valve according to claim 1, characterized in that the hydraulic connection (72; 74, 76, 86) is formed in such a length / width ratio, so that in this when opening the valve member (46) generates excess pressure and when closing the valve member (46) in the low pressure volume (68), a negative pressure is generated.

10. Solenoid valve according to claim 7, characterized in that the concave contour (84) of the integrated sleeve (80) is designed such that a flow cross-section (86) extends in the radial direction below the armature (48) substantially in the radial direction constant.

11. Solenoid valve according to claim 1, characterized in that the time period during which a differential pressure in the low pressure volume (68) is generated, depending on the length of the valve in the space (70) opening hydraulic connection (72; 74, 76; 86) ,