EP2010785A1 - Metering pump - Google Patents

Abstract

Metering pump comprising a cylindrical housing with a pump piston (12) moved back and forth in the housing for feeding (feeding stroke), and intake (intake stroke) of a hydraulic fluid from an inlet region (2) into the outlet region (4) of the pump (1), a swept volume (30) in which the fluid can be pressurized by the pump piston (12), an outlet valve (46) for the targeted ejection of the hydraulic fluid in the swept volume (30), and an inlet valve (32) in the pump piston (12) for accurate feeding of the hydraulic fluid from the inlet region (2) of the pump into the swept volume (30). At least one inlet valve (32) has control bores (36, 37), with which the feed is opened until the end of the feeding stroke of the piston (12) is reached, and the feed to the swept volume (30) is interrupted using this position.

Description

 metering

The invention relates to a metering pump according to the features of the generic part of claim 1. Dosierpumpem of the type mentioned operate on the principle of an electromagnetically or otherwise actuated axial reciprocating pump, which promotes well-defined amounts of hydraulic fluid from an inlet region in the outlet of the pump. Piston pumps have a higher efficiency than other pumps. This makes it easier to realize a higher dosing accuracy. A typical but not exclusive field of application is the metering of fuel for a combustion process, e.g. B in an internal combustion engine in the vehicle.

Dosing pumps usually have an outlet valve and an inlet valve. The inlet valve is used to allow the hydraulic fluid from the inlet region of the pump in metered quantities to flow into the reciprocating region of the pump piston. The fluid collected in the working chamber of the piston is conveyed and discharged by means of the outlet valve into the outlet region of the pump. At the beginning of a delivery stroke closes the intake valve, so that the inflow to the displacement is closed by the stroke. In the subsequent reverse suction stroke opens the inlet valve, the inlet is opened again and it flows through the resulting negative pressure a defined flow in the displacement.

Due to the stroke movements of the piston, pressure peaks of the fluid arise in the inlet region and outlet region, which can lead to an overflow of the pump. To avoid dosing errors, measures to avoid overflows through the valve are therefore necessary. The over-promotion is noticeable in particular with increasing pre-pressures of the pump. The aim is a pressure-independent delivery characteristic. As solutions exist on the one hand a damping in the inlet area, on the other hand, a pressure relief by an external fluid line. Both solutions are expensive.

DE 10 2004 028 889 A1 shows a metering pump in the function of a piston pump for conveying a hydraulic fluid, which is used in particular in brake systems of vehicles. The inlet of the hydraulic fluid takes place in the form of a slot-controlled inlet valve, which is arranged in the direction of movement of the pump piston. The fluid collected in the displacement of the pump is conveyed through an outlet valve in the form of a ball seat valve in the outlet of the pump. In the known arrangement, the control bores for the inlet valve are arranged exclusively in the housing. The holes are however determined by the construction. A positive control that compensates or degrades occurring pressure peaks of the inlet area is not provided in the known arrangement. For this purpose, complex means, such as external fluid lines or damping measures in the inlet area are required. If these additional measures are dispensed with, a stronger spring is necessary for the pump. For this purpose, again a high actuation force is necessary because the piston has to overcome a high restoring force in the form of a strong spring. DE 43 28 621 A1 shows a metering pump, in the overflows in

Hubkolbenraum be prevented by damping measures in the form of a transverse and arranged longitudinal bore in the piston, which, however, relate exclusively to the inlet region of the pump and are permanently connected thereto. The two holes on the inlet side is only a pressure pad, which smoothes the pressure profile of the pending between the inlet port and the inlet opening in the pumped medium. They contain air and are not suitable as feed. The longitudinal bore is closed at its end facing the displacement with a seal. The inlet to the displacement takes place exclusively through a suction hole in the housing, which is closed when the piston is passed over and reopened in a subsequent rearward suction stroke. In a practical further development of the pump, the sealing of the piston with respect to the displacement has been replaced by a valve disposed in the valve seat valve with a specific and limited closing pressure, whereby an inlet in the piston is made possible. The axial arrangement of the transverse bore connected to the inflow at the piston circumference defines only the Nutzhub the displacement. If the reciprocating piston has reached its stop facing the outlet during a delivery stroke, it is not ensured in the known arrangement that the inflow is closed by the transverse bore. If the transverse bore is not closed, further fluid can flow in through the control bores arranged in the piston when the delivery end stroke is reached due to the pressure peaks at the inlet region. There is a risk that the seat valve is lifted from its closed position and leads to over-promotion. It is the object of the invention which caused by over-promotion

Prevent dosing errors with simple means. The solution of the problem is in connection with the generic features of claim 1 by its characterizing features.

By means of the invention, a "positive control" is realized by the positioning of the inlet, which is positioned such that it establishes a connection between the inlet area and the lifting area in each exposed position of the piston and is only closed when the delivery end position is reached The supply bore remains open until the piston reaches its final delivery position, and only when this position is reached is a further inflow of the hydraulic medium into the displacement prevented There are no or few additional measures for the inflow, as these wells already exist in many applications, but the prior art only served as a permanently open flow channel Use as a control bore was not yet provided. The inlet bore now used as a control bore in the invention must only be shaped so that a defined closing function is achieved. The inventive arrangement of the control bores a balance between the pressure peak and the required metering accuracy is achieved and realized in the displacement compensation for the pressure occurring during the delivery stroke. This is achieved only by modifying the bore, "slot geometry," or other combinations of different sizes or different positioned holes, and eliminating the need for stronger return springs and higher drive forces.

The advantage of a slot-controlled intake valve known from the prior art is additionally improved by measures against over-delivery. This means that the delivery accuracy - depending on the design of the inlet and outlet valves and the operating point - is many times independent of the pre-pressure. In order for an arranged upstream of the working volume intake valve is realized, which comprises a series connection of two intake valves.

In an advantageous embodiment of the invention, the inflow comprises an additional inflow in the housing with a further inlet valve. Both intake valves have different functions. The inlet valve arranged in the housing serves in the delivery stroke for controlling and exact filling of the displacement. The intake valve in the piston, however, reduces the negative pressure in the displacement during the return / or suction stroke of the piston. The valve inlet in the housing may comprise a simple inlet bore, with which the conveying fluid is conveyed into the displacement of the piston during a suction stroke, and which opens and / or closes when passing over the piston. In addition, however, such an inlet valve can also be configured slit-controlled, wherein a plurality of control slots can also be provided, which are arranged concentrically to one another. The control bores for such a valve are advantageous in the space between the Innumfang the cylindrical housing and a guide sleeve for the piston arranged. The guide sleeve has an opening to the displacement of the pump.

The inlet valve in the pump piston advantageously comprises a blind bore in the direction of the inlet region with a subsequent transverse bore which opens in the inlet region of the pump. As a closure, a seat valve is provided on the front side of the piston. The longitudinal bore is closed by the seat body in the form of a ball. The mouth of the transverse bore to the inlet area remains open until the piston has reached its final delivery position. As a result, the overpressure present in the inlet area is also applied to the seat valve at the mouth to the displacement of the piston.

Since the transverse bore closes the inlet to the ball seat valve in the end position of the piston, the pressure peak in the inlet area of the pump can not open the ball seat valve. There is no over-promotion. On the return or suction stroke, however, the transverse bore releases the conveying path again. Now, the overpressure in the suction part of the pump compared to the negative pressure in the capacity slightly open the ball seat valve, thus allowing a smooth piston stroke. For the closure of the control bore or the transverse bore to the

Inlet area, no additional measures are required. In this case, the guide and / or bearing sleeve arranged between the housing and the piston is advantageously used. This type of storage of the piston is state of the art today. The axial length of the slide bearing sleeve extending in the direction of the transverse bore is dimensioned as a function of the piston stroke. The position of the transverse bore and the Ausraglänge the guide sleeve is arranged so that upon reaching the Förderendhubes the transverse bore is covered by the Ausraglänge of the sleeve in this direction and is closed. The sliding bearing of the piston in the guide sleeve prevents fluid material between piston and sleeve can penetrate into the displacement in the closed position. The dosing pump according to the invention is advantageously magnet-actuated. The stroke of the piston is generated with an integrated electromagnetic system, in which the piston is firmly connected to an armature of a solenoid, which is centrally surrounded by a coil. The pump piston forms an anchor rod arranged in the stroke direction of the armature, which passes through the cone of the magnet. In the de-energized state, all cavities in the inlet region and in the displacement of the piston are filled with hydraulic fluid. When the coil is energized, the armature displaces the piston against the force of a compression spring, which is arranged between the armature and the bearing sleeve of the piston. Due to the pumped medium collected in the displacement, the outlet valve is opened and the fluid is ejected. At the same time another inflow is blocked. During this time, further fluid material runs in the armature lifting space associated with the inlet area. When the power is turned off, the spring pushes the armature and thus the piston back to the starting position. It starts the backward suction stroke. This creates a vacuum in the displacement of the piston. About the now opened again inlet valve, both in the housing and in the piston, new fluid material can run in the displacement until a further delivery stroke takes place when energized again the magnet. Further advantageous embodiments of the invention will become apparent from the

Subclaims and an embodiment described in the drawing.

Fig. 1 shows a cross-sectional view of the invention in a first position of the pump piston. FIG. 2 shows a section of FIG. 1.

Fig. 3 shows the detail of Fig. 1 in a different position of the pump piston.

Fig. 1 shows in a cross-sectional view of a solenoid-operated fuel metering pump 1, which is used for example for diesel injection or for use in motor vehicle heating systems. The cylindrical pump piston 12 is fixed to the likewise cylindrical Magnet armature 13 is connected, which is surrounded centrally by a coil body 21 embedded in a magnetic coil 14. With the pump 1 accurately measured amounts of fuel are conveyed from a tank to a consumer. The flow direction of the fuel is from right to left in the direction of arrow X.

The pump 1 essentially comprises three areas, an inlet area 2, a pump area 3 and an outlet area 4. The inlet and pump area 2, 3 are shown enlarged in FIGS. 2 and 3.

The inlet portion 2 has, as shown in Fig. 1 rightmost, an intake 5 with an axial bore 7 for sucking the fuel. The entrance of the bore 7 is closed with a protective cap 6 against contamination in the delivery and transport state. From the intake manifold 5, the fuel flows through a filter 8 and enters a region designated as the zero closure 9. This region prevents the fuel flow into the pump region 3 when the pump piston 12 is not actuated. The zero seal 9 comprises a plastic sleeve 10, in the opening region of which the filter 8 is arranged. Its sleeve bottom has an axial passage opening 11 in the direction of the pump region 2 which, when the magnet armature 13 is not actuated, as is apparent in particular from FIG. 2, is closed by a rear piston stub 15 extending in the direction of the opening 11. Upon actuation of the pump piston 12, as can be seen in particular from FIG. 3, the passage opening 11 is opened for the fuel. The secure seal between the opening 11 and the piston stub 15 is ensured by a first O-ring seal 16 arranged on the outer circumference of the piston stub 15.

The magnet armature 13 has a continuous stepped anchor bore 18 whose diameter is slightly increased in the direction of its cone 17 and in the other direction is designed as a chamber 19 in which the fuel can flow when the through-opening 11 is open. In the anchor bore 18, the pump piston 12 is firmly inserted as a rod. stressed. During a stroke movement of the armature 13 opens or closes in the direction of intake 5 directed piston nozzle 15, the passage opening 11 to the intake manifold fifth

The armature 13, the zero closure 9 and the filter 8 are surrounded by an existing of ferromagnetic material anchor housing 20 and sealed against the plastic sleeve 10 of the zero degree 9 and the intake manifold 5 by two O-ring seals 54, 55. The armature 13 and thus the pump piston 12 is axially displaceable in the armature housing 20 movable. The outer wall of the armature 13 and the inner wall of the armature housing 20 are arranged at a distance from one another and form an inlet channel 42, which establishes a connection from the chamber 19 in the zero end 9 to the pump region 3.

On the armature housing 20, the bobbin 21 is pushed in its left end portion, which is suitably connected by brazing or welding to the armature housing 20, and surrounded by a magnetic housing 22, at its in the direction of the inlet portion 2 extending end with the armature housing 20 is firmly connected.

From the other (left) side in Fig. 1 in the bobbin 21 a likewise made of ferromagnetic material sleeve 23 is inserted, whose end cone 24 facing conical opening is effective as a magnetic pole, and, as the armature housing 20, in the Clamp seat within the bobbin 21 holds. In the sleeve 23, a bearing sleeve 26 is fitted with a suction port 25, which secures as sliding bearing 27 the pressed-in the armature 13 pump piston 12 an axial guidance. Between the sleeve 23 and the bearing sleeve 26, a further inlet channel 43 is arranged, which connects the Hubankerraum 29 with the suction port 25.

The bobbin 21 is delimited in the direction of the outlet region 4 by a conical disk 33, which forms the radial extending region of the magnetic pole. The bobbin 21 has at this end a radial cover 35 which is axially penetrated by the sleeve 23 and with this is firmly connected. The energization of the coil 14 via a protruding from the cover coupling plug 34. The cover 35 is sealed relative to the sleeve 23 by a further O-ring seal 56. Another O-ring seal 57 seals it from the magnet housing 22.

The end faces of the sleeve 23 and the armature 13 are arranged in the middle of the bobbin 21 at an axial distance from one another and form a Hubankerraum 29, which is filled in the armature region with fuel in the de-energized state through the inlet channel 42. In the area 29, a compression spring 28 is arranged, which is supported with its one end against the end cone 24 of the armature 13 and supported with its other end against the protruding end of the bearing sleeve 26. When the coil 14 is energized, the armature 13, together with the pump piston 12, is displaced (towards the left) in the direction of the cone 17 against the force of the pretensioned compression spring 28 (FIG. 3).

The inlet channel 43 discharges via the suction opening 25 into a displacement 30, which determines the Nutzhubbereich the pump 1 in the axial direction and two inlet valves 31, 32, of which the valve 31 in the housing and the valve 32 are arranged in the piston 12. In the radial direction of the displacement 30 is determined by the inner diameter of the sleeve 23.

The inlet valve 31 in the housing is formed by the suction opening 25 and the stroke movement of the pump piston 12. When passing over the opening 25, the associated inlet channel 43 is opened or closed by the position of the piston 12. By axial positioning of the intake opening 25 and the design of the opening bores, control functions can also be realized in this valve 31.

The other inlet valve 32 is arranged on the end face of the piston 12. It forms a series-connected valve arrangement with a transverse bore 37 and subsequent axial blind bore 36, which is positively controlled closed as soon as the piston 12 has reached the end of the delivery stroke. The transverse bore 37, which is connected to the lifting armature space 29 of the Lass region 2 is in communication, is positioned so that it is closed by reaching the Förderendhubes of the piston 12 of the bearing sleeve 26. However, if this inlet is opened by the position of the piston 12, the transverse bore 37 and the axial blind bore 36 form a further inlet for the displacement 30 of the pump 1.

The mouth region of the blind bore 36 has a seat valve 38. In the sitting position, the inlet via the transverse and blind bore 36, 37 is closed in the displacement 30. The closure is effected by a seat body 41 and a further compression spring 39, which is supported in the valve seat 40.

The piston 12 in its Förderendhub elastically abuts against a stop 44, which is designed as a damping disc and has a central passage 45 for the expelling through a delivery fuel, which is thereby conveyed into the outlet region 4 of the pump 1. The outlet region 4 essentially comprises an outlet valve 46 and an outlet nozzle 47 bounding the pump, the bore 40 of which is closed by a further protective cap 48 in the transport and storage state.

The exhaust valve 46 is also designed like the second inlet valve 31 in the piston as a seat valve. In the sleeve 23, at its end facing the outlet valve 46, the associated valve seat 50 is inserted with a central opening 51 for the passage 45 of the fuel. The associated seat body is designed as a ball 52 which closes the opening 51 by a further compression spring 53. During the delivery stroke of the fuel, the ball 52 is raised from its sitting position against the force of the compression spring 53 and conveys the fuel into the outlet connection 47.

The operation of a dosing pump 1 constructed in this way is as follows:

The positions of the magnet armature 13 shown by FIGS. 1 and 2 show the de-energized state in which all interspaces in the pump 1 are flooded with fuel. This concerns the Hubankerraum 29 im Inlet area 2 and in particular the displacement 30 in the pumping area 3. The first inlet valve 31, which is formed by the inlet channel 43 and the suction opening 25, is open. On the other hand, the second inlet valve 32 is closed, although the inlet in the piston 12 is still free, since the transverse bore 37 functioning as a control bore is not yet covered by the bearing sleeve 26 in this position. The delivery pressure of the fuel occurring in the inlet region 2 is thus directly applied to the seat valve 38.

In a delivery stroke of the pump (to the left), the coil 14 is energized and connected to the armature 13 pump piston 12 is moved in the direction against the stop 44 in its Förderendposition. The suction opening 25 in the Lagerhϋlse 26 is positioned so that it is already closed at the beginning of the delivery stroke by driving over the piston 12, so that no fuel can flow through the inlet channel 43.

The fuel collected in the displacement 30 is pressed by the delivery stroke into the outlet region 4 of the pump 1. The arranged there ball 52 of the exhaust valve 46 is raised and promotes the fuel in the outlet port 47. Upon reaching the Förderendhubes, as can be seen from Fig. 3, and the supply via the second inlet valve 32 in the piston 12 is locked because according to the invention Cross hole 37 is covered in this position by the bearing sleeve 26. Thus occurring pressure peaks are no longer degraded in the inlet region 2 occurring in the piston position, which could lead to over-promotion in the reciprocating piston 30 of the pump 1.

With the beginning of the delivery stroke, the closure of the zero end 9 at the rear end of the armature 13 is opened at the same time, and it simultaneously new fuel flows into the Hubankerraum 29.

Upon reaching the (left) Förderendposition the stop 44 of the exhaust valve 46, the energization of the coil 14 is interrupted. By the restoring force of the first compression spring 28 in Ankerhubraum 29, the armature 13 is pushed back together with the piston 12 in its initial situation (Fig. 2), whereby in the displacement 30, a negative pressure is generated with a suction effect. Once the suction port 25 and the transverse bore 37 are free again by the return of the piston 12, new fuel can flow into the displacement 30 until the piston 12 has reached its original position again, and another inflow is stopped by the zero closure 9. Subsequently, a further delivery stroke takes place by renewed energization of the coil 14.

The present invention has been explained using the example of two inflows, each with two inlet valves. However, it is understandable without further explanation to those skilled in the art that the invention can also be used in metering pumps in which the inflow takes place exclusively via the second inlet valve 32 in the piston and the inflow via the first inlet valve 31 is dispensed with, so that the valve 32 in addition to control functions at the same time the filling of the displacement 30 takes over. For this purpose, only the seat valve 38 provided there is to be interpreted accordingly.

Claims

claims 1) metering pump, comprising A cylindrical housing having a pump piston (12) reciprocated in the housing for conveying (delivery stroke), and sucking (suction) a hydraulic fluid from an inlet region (2) into the outlet region (4) of the pump (1), A displacement (30) in which the fluid is pressurisable by means of the pump piston (12), an outlet valve (46) for the directed ejection of the Displacement space (30) located hydraulic fluid and arranged in the pump piston (12) inlet valve (32) for defined inflow of hydraulic fluid from the inlet region (2) of the pump in the displacement (30), characterized in that the at least one inlet valve (32) Control bores (36, 37), with which the inlet is open until reaching the Förderendhubes the piston (12), and is interrupted by this position, the inlet to the displacement (30). 2) Dosing pump according to claim 1, characterized in that the inlet via a further inflow bore (25) in the housing with an additional inlet valve (31). 3) Dosing pump according to claim 2, characterized in that the additional inlet valve (31) is slot-controlled. 4) Dosing pump according to one or more of claims 1 to 3, characterized in that the control bore comprises an axial blind bore (36) in the direction of the inlet region with a subsequent transverse bore (37). 5) Dosing pump according to claim 4, characterized in that the transverse bore (37) is axially positioned so that it is closed when reaching the Förderendhubes. 6) Dosing pump according to one or more of claims 1 to 5, characterized in that the inlet valve (32) controls the passage of the blind bore (36) to the displacement (30). 7) Dosing pump according to one or more of claims 1 to 6, characterized in that the inlet valve 32) a seat valve (38) with a the Includes blind bore (36) closing seat body (41). 8) Dosing pump according to one or more of claims 1 to 7, characterized in that the piston (30) in a fixedly connected to the housing bearing sleeve (26) is slidably mounted. 9) Dosing pump according to one or more of claims 1 to 8, characterized in that on reaching the Förderendhubes the transverse bore (37) of the bearing sleeve (26) is closed. 10) Dosing pump according to one or more of claims 1 to 9, characterized in that the piston (12) is actuated electromagnetically, in particular by a pushed onto the housing lifting magnet. 11) Dosing pump according to claim 9, characterized in that the Piston (12) is fixedly connected to a magnet armature (13) of the lifting magnet.