DE102010062451A1 - Change-over valve i.e. flow control valve, for installation in high pressure pump of internal combustion engine of motor vehicle, has stop for valve needle formed by concave cavity of valve body, where cavity is rotationally symmetrical - Google Patents

Abstract

The valve (10) has a valve body (26), and a valve needle (20) biasing the valve body from time to time, where movement of the valve needle is limited by a stop in one direction. A stop (34) for the valve needle is formed by a concave cavity (24) of the valve body. The cavity is rotationally symmetrical with respect to a longitudinal axis (12), where depth of the cavity increases monotonically as a function of decreasing radius. The cavity has a geometrical shape corresponding to that of a spherical cap.

Description

State of the art

The invention relates to a switching valve according to the preamble of claim 1.

Known from the market are switching valves, such as those used as quantity control valves upstream of high-pressure pumps for internal combustion engines in motor vehicles. Frequently, such switching valves have a valve needle, which can act on an approximately plate-shaped valve body.

It is also known to limit a stroke of the valve needle in the switching valve by a so-called needle collar in at least one axial direction. The needle collar is rigidly coupled to the valve needle or in one piece. manufactured with the valve needle. Due to the needle collar, the moving mass is increased, which must be taken into account especially in fast switching operations.

In injectors, it is also known, the movement of an "anchor-needle assembly" formed from the valve needle and an armature in one axial direction by an armature stop on a pole core of an electromagnet and in the other axial direction by abutment on a sealing seat of the Limit injection valve.

Disclosure of the invention

The problem underlying the invention is achieved by a switching valve according to claim 1. Advantageous developments are specified in subclaims. Features which are important for the invention can also be found in the following description and in the drawings, wherein the features, both alone and in different combinations, can be important for the invention, without being explicitly referred to again.

The invention has the advantage that the movement of a valve needle of a switching valve can be limited to a first stop without the action of a needle collar, with comparatively large axial forces can be transmitted to the valve needle or the stop with sufficient fatigue strength. In this case, a diameter of the valve needle can be reduced and dispensed with a diameter jump. In addition, the moving mass of the switching valve can be reduced, switching speeds increased, the operating noise is reduced and costs are reduced.

The invention takes advantage of the fact that during operation of the switching valve, an end portion of the valve needle strikes a valve body, wherein the valve body in turn can strike for example on a housing portion ("rest") of the switching valve. Thus, a first condition is given to limit the axial movement of the valve needle without the involvement of a needle collar. In addition, the invention is based on the consideration that, in particular with fast-switching switching valves, relatively large dynamic forces can act on the valve needle and the valve body. In order to prevent a permanent deformation of the valve needle and / or of the valve body that is detrimental to the operation of the switching valve, the valve body according to the invention has a concave recess in which the end section of the valve needle can abut. As a result, possible deformations of the valve needle or the valve body are structurally anticipated ("wear reserve"), so that a possible "digging" of the end portion into the valve body during operation of the switching valve can at least be reduced. The invention prevents the valve lift and / or a magnetic force (working stroke, air gap) from changing in an inadmissible manner, which may result in an insufficient function of the switching valve.

In addition, it is provided that the recess is rotationally symmetrical with respect to a longitudinal axis, and that a depth of the recess monotonically increases with decreasing radius. As a result, first of all, the valve body embodied according to the invention, regardless of a possible rotation about a longitudinal axis of the switching valve, can always produce an optimal stop. Second, the recess according to the invention is designed such that the valve body can center itself with respect to the axis of the valve needle at least over several cycles of the switching valve itself. In this way, a particularly precise switching of the switching valve can be achieved without incurring additional costs.

In particular, it is provided that the recess has approximately the geometry of a spherical cap. Thus, a particularly suitable for the invention geometry of the recess is described, which can be made simple and inexpensive.

The fatigue strength of the switching valve is further improved if the geometry of the recess and the geometry of the end portion of the valve needle are at least partially complementary to the first stop. As a result, the contact surface between the valve needle and the valve body can be optimized, and axial pressure forces occurring at the stop can be limited. Preferably, the geometries are carried out that even with a radially slightly displaced position of the valve body still a sufficiently large contact surface can be formed.

An application of the switching valve provides that it is a quantity control valve of a high-pressure fuel pump. Quantity control valves for fuel pumps in motor vehicles require a particularly precise switching in order to precisely measure a respectively required amount of fuel. By inventively reduced mass of the valve needle, the switching speed of the switching valve can be increased while maintaining a sufficient fatigue strength.

Hereinafter, exemplary embodiments of the invention will be explained with reference to the drawings. In the drawing show:

1 a simplified diagram of a fuel system of an internal combustion engine;

2 a sectional view of a quantity control valve of the fuel system of 1 ;

3 a detailed view III of the quantity control valve of 2 ;

4 one to the 3 similar representation;

5 a force diagram at a first stop of the quantity control valve of 2 to 4 ; and

6 a diagram for the axial movement of a piston of a high-pressure pump of the fuel system of 1 ,

The same reference numerals are used for functionally equivalent elements and sizes in all figures, even in different embodiments.

1 shows a fuel system 1 an internal combustion engine in a much simplified representation. From a fuel tank 9 will fuel through a suction line 4 , by means of a pre-feed pump 5 , via a low pressure line 7 , and about one of an electromagnet 15 actuatable switching valve 10 - Which in the present case a quantity control valve 10 is - (not explained here) (piston) high-pressure pump 3 fed. Downstream is the high pressure pump 3 via a high pressure line 11 to a high-pressure accumulator 13 ("Common rail") connected. Other elements, such as outlet valves of the high pressure pump 3 , are in the 1 not drawn. It is understood that the switching valve 10 or the quantity control valve 10 as a unit with the high-pressure pump 3 can be trained. For example, the quantity control valve 10 an inlet valve of the high pressure pump 3 be.

In addition, the quantity control valve 10 also an actuator other than the electromagnet 15 have, for example, a piezoelectric actuator or a hydraulic actuator.

When operating the fuel system 1 promotes the pre-feed pump 5 Fuel from the fuel tank 9 in the low pressure line 7 , The quantity control valve determines 10 the delivery chamber of the high pressure pump 3 amount of fuel supplied.

2 shows the quantity control valve 10 from 1 in a sectional view. The quantity control valve 10 is substantially rotationally symmetric to a longitudinal axis 12 executed. It includes several different housing sections 14 in which elements of the quantity control valve 10 are arranged. In a middle area of the drawing of 1 is an anchor 16 arranged, which axial anchor holes 18 and with a valve needle 20 is axially coupled. In the present case is the anchor 16 with the valve needle 20 rigidly connected. In the drawing above the anchor 16 is between the anchor 16 and a housing section 14 an anchor spring 22 arranged. The anchor 16 is part of the in the 2 not fully illustrated electromagnet 15 , Between the anchor 16 and a pole core arranged above in the drawing 17 in this case, an annular armature gap 19 educated.

The anchor 16 and those with the anchor 16 coupled valve needle 20 are in the quantity control valve 10 guided radially by means of two guide sections. A first guide section 28 is defined by an axial portion of a peripheral surface of the armature 16 educated. A second guide section 30 is in a lower part of the drawing of 2 through a circumferential surface of the valve needle 20 opposite a housing section 14 educated. In the drawing to the right of the guide section 30 is an opening 31 arranged. The low pressure line 7 is at a radial opening 33 in the left in the drawing area of the quantity control valve 10 connected.

An end section 32 the valve needle 20 is how very good 3 it can be seen in a dome-shaped recess 24 a valve body 26 at one through the boundary surface of the recess 24 formed first stop 34 struck down in the drawing. Here are the geometries of the end section 32 and the recess 24 at least partially executed in approximately complementary. In this way, between the end section 32 and the recess 24 formed a sufficiently large contact surface, so that resulting compressive stresses in the end portion 32 or the recess 24 stay relatively small. The recess 24 is rotationally symmetrical to the longitudinal axis 12 executed.

The valve body 26 is in the illustrated positively open position in turn at a retirement home 36 a housing element 38 struck. A valve spring designed as a compression spring 40 is between a bottom of the housing element 38 and the valve body 26 arranged and acts on the valve body 26 in the direction of a sealing seat 42 in the drawing upwards. In the present case is between the sealing seat 42 and the valve body 26 an annular gap 44 formed, can flow through the fuel during operation in the delivery chamber of the fuel pump.

In the presentation of the 2 is the electromagnet 15 not energized, and the anchor 16 , the valve needle 20 and the valve body 26 are due to the force of the armature spring 22 in their lowest position in the drawing. The end section 32 resting on the concave surface of the recess 24 , The quantity control valve 10 So it is open and the downstream of the quantity control valve 10 arranged high-pressure pump 3 is in a suction phase.

In a subsequent Rückströmphase promotes the high-pressure pump 3 due to the forcibly opened quantity control valve 10 not, and the electromagnet 15 is still not energized. In the process, the quantity control valve becomes 10 by means of the anchor spring 22 kept open.

At the beginning of a subsequent promotion phase of the high-pressure pump 3 becomes the electromagnet 15 energized and the anchor 16 is from the pole core 17 dressed. The valve needle 20 lifts it from the valve body 26 at least so far that the valve spring 40 - Supported by hydraulic flow forces in the quantity control valve 10 - the valve body 26 against the seal seat 42 can press. The annular gap 44 can disappear and the quantity control valve 10 thus close. Now fuel is in the high-pressure accumulator 13 ("Rail") promoted.

After the end of the funding phase, the energization of the electromagnet 15 switched off, whereupon the armature spring 22 the anchor 16 together with the valve needle 20 in the drawing pushes down. This beats the end section 32 the valve needle 20 against the valve body 26 , The following is the valve body 26 - again supported by flow forces - from the sealing seat 42 lifted and against the retirement home 36 pressed. When striking the end section 32 at the recess 24 of the valve body 26 can generate comparatively high forces. Due to the recess 24 , which in the present case has the geometry of a spherical cap, and by the at least partially complementary geometry of the end portion 32 remain during striking the resulting local compressive stresses relatively small.

The spherical cap-shaped recess 24 moreover has the property that an (axial) depth of the recess 24 increases monotonically with decreasing radius. This may cause the valve body 26 in relation to the valve needle 20 or the longitudinal axis 12 center yourself, as will be described below.

4 shows one to the 3 similar representation of a slightly different embodiment of the quantity control valve 10 , The illustrated elements are identified by their reference numerals.

5 shows a force diagram when striking the end portion 32 the valve needle 20 to the recess 24 of the valve body 26 , A normal force 50 indicating the direction of the local surface normal at the stop 34 has in an axial component 52 and a radial component 54 disassembled. It can be seen that the radial component 54 is directed so that it has a centering between the valve needle 20 and the valve body 26 allows. The farther the valve needle 20 from the center of the recess 24 is removed, the larger the radial component 54 , Otherwise, the axes of the valve needle 20 and the recess 24 identical, both elements are already maximally centered and the radial component 54 is zero (not shown).

It is understood that the geometry of the recess 24 in the 2 to 5 can also be designed differently. In particular, the axial depth of the recess 24 be smaller than in the 5 shown.

6 shows a coordinate system for illustrating the axial movement of a piston of the high pressure pump designed as a piston pump 3 , Shown on the abscissa is a time t and on the ordinate a stroke 60 of (in 6 not shown) piston. A horizontal dashed line 62 indicates a top dead center of the piston movement. The bottom dead center of the piston movement corresponds to a stroke 60 from zero.

An arrow 64 indicates the temporal range of the suction phase, an arrow 66 indicates the time range of the Rückströmphase and an arrow 68 indicates the time range of the delivery phase of the high-pressure pump 3 , Overall, the three designated phases represent a period of working movement of the high pressure pump 3 represents.

It can be seen that the suction phase is defined between top dead center and the subsequent bottom dead center. The subsequent Rückströmphase begins with the bottom dead center and ends by way of example at a time t1 before reaching the following top dead center. The subsequent promotion phase begins at time t1 and ends at the following top dead center. The time t1 depends on the activation of the electromagnet 15 of the quantity control valve 10 ,

Claims (5)

Switching valve ( 10 ) with a valve body ( 26 ) and a valve needle acting on it at least temporarily ( 20 ), whose movement is limited in at least one direction by a stop, characterized in that a first stop ( 34 ) for the valve needle ( 20 ) at a concave recess ( 24 ) on the valve body ( 26 ) is formed. Switching valve ( 10 ) according to claim 1, characterized in that the recess ( 24 ) rotationally symmetric with respect to a longitudinal axis ( 12 ) is executed, and that a depth of the recess ( 24 ) increases monotonously with decreasing radius. Switching valve ( 10 ) according to claim 1 or 2, characterized in that the recess ( 24 ) has approximately the geometry of a spherical cap. Switching valve ( 10 ) according to at least one of the preceding claims, characterized in that at the first stop ( 34 ) the geometry of the recess ( 24 ) and the geometry of the end section ( 32 ) of the valve needle ( 20 ) are at least partially complementary in some areas. Switching valve ( 10 ) according to at least one of the preceding claims, characterized in that it comprises a quantity control valve ( 10 ) a high-pressure fuel pump ( 3 ).

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