EP0244575B1 - Internal-gear pump - Google Patents

Description

The internal gear pump according to the preamble of claim 1 is known from DE-A 3 444.859.

An internal gear pump is also the subject of GB-A 2 069 609. The internal gear and external gear are accommodated in a housing covered on the open side by a control plate. The control plate is closed by a cover. The outlet channels are provided in the control plate and covered by check valves in the form of resilient metal tongues. They open into a collecting space which extends over more than 180 _° C. in the form of a kidney-shaped recess in the radial extent which extends inward beyond the root circle of the meshing teeth of the external gear in the side of the control plate which is away from the gearwheels. The pressure building up in this collecting space thus has a full effect in the area of the combing teeth on their end faces.

Since such internal gear pumps are based on the principle that a large number of cells which are sealed against one another are formed by the intermeshing teeth, the pump must be manufactured with narrow tolerances in order to avoid leakage on the one hand but also prevent cavitation damage.

On the other hand, since the plurality of outlet channels must be connected to one another and end in an outlet chamber having a larger cross-section, it is the object of the invention to avoid the pump housing being deformed as a result of the pressure forces prevailing in the outlet chamber and the narrow tolerances achieved by precise production being thereby disturbed.

The solution results from claim 1.

Claim 2 indicates further training and function of the outlet chamber. Through the design according to claims 3 and 4, tilting forces are avoided, in particular if the center line of the circular segment or in particular if the line which divides the circular segment into two equally large, radial halves lies on the cylindrical housing.

In the embodiment according to claim 5, there is the advantage that, despite a large number of mutually closed cells and associated outlets, there is only a limited number of outlet openings with the necessary check valves in each outlet chamber, so that there is sufficient space for the accommodation. It is also achieved that the compressive forces act symmetrically on the housing and therefore cancel each other out.

The invention thus improves an internal gear pump which has so many rotating and mutually closed cells that there are always several - at least three - cells with a decreasing volume in the outlet zone. There are a number of outlets corresponding to the number of cells. Some or all of these outlets open into the lubricating oil channel. However, those outlets that are assigned to a cell with a large volume are blocked by a check valve. Only the smallest or the smallest outlet openings assigned to the lubricating oil channel can open directly into the lubricating oil channel without a check valve.

Exemplary embodiments of the invention are described below with reference to FIGS. 1 to 5.

The following description applies to both exemplary embodiments according to FIGS. 1, 2 on the one hand and FIGS. 3 to 5 on the other hand together.

The outer wheel 1 is freely rotatably mounted in the housing cylinder 31. The outer wheel 1 has an internal toothing 2. The cylindrical housing 31 is closed on both sides by the covers 32 and 33. In the cover 32, the shaft 34 is rotatably supported and driven by a motor vehicle engine, not shown. The inner wheel 3 is mounted on the shaft 34 in a rotationally fixed manner. The inner wheel 3 has an external toothing 4 which engages with the internal toothing 2 of the outer wheel 1. To improve the efficiency, the interior of the pump, which is outside the engagement area, can be filled with sickle 57. The sickle hugs the circles of the gears to a large extent. The inlet channel 35 is located in the cover 33. The inlet channel 35 is connected to the sump 36 via a throttle 37. A pressure control valve 39 is located in a bypass 38, which is connected in parallel to the throttle channel 37. The piston 40 of the pressure control valve controls the opening of the bypass channel 38 to the sump 36 with its control edge 41. The piston is on one side with a spring 42 charged. On the opposite side, the piston in control chamber 43 is acted upon by the outlet pressure via control line 44.

The pump forms on the outlet side between the intermeshing teeth of the outer wheel 1 and inner wheel 3 four (FIG. 1) or three (FIG. 4) cells which are closed in the circumferential direction and in the axial direction and which have been completely or partially filled with 01 via inlet channel 35.

• In den Deckel 32 sind vier Auslaßöffnungen 48.1, 48.2, 48.3, 48.4 eingebracht. Im Schnitt nach Fig. 2 ist nur eine dieser Auslaßöffnungen zu sehen. Diese Auslaßöffnung ist dort mit 48 bezeichnet. Jede der Auslaßöffnungen steht mit einem in den Deckel 33 gebohrten Auslaßkanal 49 in Verbindung. Der Auslaßkanal ist jeweils auch radial nach außen gerichtet, wie Fig. 2 zeigt. Daher mündet jeder Auslaßkanal 49 auf der Außenseite des Deckels 33 möglichst nah am und axial über dem Gehäuse 31. Die Auslaßkanäle müssen nicht notwendigerweise mit radialer Komponente durch den Deckel gebohrt werden. Es ist z.B. auch möglich, daß die Auslaßkanäle als radiale Nuten in der den Zahnrädern zugewandten Seite von Deckel 33 ausgeführt sind und sodann durch einen axialen Stichkanal in dem Deckel in die Auslaßbohrungen 52 der Auslaßkammer 51 einmünden.

The following applies to the exemplary embodiment according to FIGS. 1, 2:

• Four outlet openings 48.1, 48.2, 48.3, 48.4 are introduced into the cover 32. In the section of Fig. 2, only one of these outlet openings can be seen. This outlet opening is designated there by 48. Each of the outlet openings is connected to an outlet channel 49 drilled in the cover 33. The outlet channel is also directed radially outwards, as shown in FIG. 2. Therefore, each outlet channel 49 opens on the outside of the cover 33 as close as possible to and axially above the housing 31. The outlet channels do not necessarily have to be drilled through the cover with a radial component. It is also possible, for example, for the outlet channels to be designed as radial grooves in the side of cover 33 facing the gearwheels and then to open into the outlet bores 52 of the outlet chamber 51 through an axial branch channel in the cover.

An outlet housing 50 is placed pressure-tight on the cover 33. The outlet housing 50 forms an outlet chamber which communicates with the outlet openings gen 48.1 to 48.4 is connected via a pressure channel 49 and a bore 52. The bores 52.1, 52.2 and 52.3 (see FIG. 1) are each closed by a check valve. The check valve is formed by an m-shaped plate which is screwed against the wall 53 of the outlet housing 50. The tongues protruding from the common crossbeam 55 of the check valve 54 cover the bores 52. Therefore, these tongues act as check valves. Each check valve only releases the connection from the respective pressure cell formed between the teeth via the respective outlet opening 48, pressure channel 49 and bore 52 if the pressure of the outlet cell is at least equal to the outlet pressure in the outlet chamber 51. The last and smallest pressure cell is directly connected to the outlet chamber via opening 48.4 and corresponding channels 49, 52.

• In den Deckel 33 sind drei Auslaßöffnungen 48.1, 48.3, 48.5 eingebracht. In den Deckel 32 sind zwei Auslaßöffnungen 48.2, 48.4 eingebracht. Die Auslaßöffnungen des Deckels 33 sind gegenüber den Auslaßöffnungen des Deckels 32 versetzt angeordnet. Das heißt: In der Projektion auf eine Normalebene überdecken sich die Auslaßöffnungen im Deckel 33 bzw. 32 nicht - wie Fig. 4 zeigt. Die Auslaßöffnungen schmiegen sich mit ihrer radial inneren Kante 27 (Innenkante) eng an die Eingriffslinie 11 an, und zwar derart, daß zwischen der Eingriffslinie 11 und der Innenkante 27 lediglich ein schmaler, jedoch für die Abdichtung ausreichend dichtender Dichtsteg 28 stehenbleibt. Die Breite der Auslaßöffnungen 48.1 bis 48.5 ist so gewählt, daß die Auslaßöffnungen von dem Querschnitt der Zähne 2 des Hohlrades 1 bei entsprechender Stellung der Zähne überdeckt werden, wobei in Umfangsrichtung ebenfalls ausreichende Dichtflächen stehenbleiben. In der radialen Höhe erstrecken sich die Auslaßöffnungen bis in den Bereich des Außenumfangs des Hohlrades und jedenfalls bis zum äußersten Bereich, mit dem der Grund der Zahnlücken des Hohlrades 1 auf der Stirnfläche der Deckel 32, 33 mündet.

The following applies to the exemplary embodiment according to FIGS. 3 to 5:

• In the cover 33, three outlet openings 48.1, 48.3, 48.5 are introduced. Two outlet openings 48.2, 48.4 are introduced into the cover 32. The outlet openings of the cover 33 are arranged offset with respect to the outlet openings of the cover 32. That means: in the projection onto a normal plane, the outlet openings in the cover 33 or 32 do not overlap - as shown in FIG. 4. The outlet openings nestle closely with their radially inner edge 27 (inner edge) to the line of engagement 11, in such a way that only a narrow, but sufficiently sealing sealing web 28 remains between the line of engagement 11 and the inner edge 27. The width of the outlet openings 48.1 to 48.5 is selected so that the outlet openings are covered by the cross section of the teeth 2 of the ring gear 1 with the teeth in a corresponding position, sufficient sealing surfaces also remaining in the circumferential direction. In the radial height, the outlet openings extend into the area of the outer circumference of the ring gear and in any case up to the outermost area with which the bottom of the tooth gaps of the ring gear 1 opens on the end face of the covers 32, 33.

• Die Zähne des Hohlrades werden nach einem Verzahnungsgesetz hergestellt, auf das später noch eingegangen wird. Dieser nach dem Verzahnungsgesetz entstehende ideale Zahnlückengrund ist für eine Zahnlücke punktiert eingezeichnet und mit 29 bezeichnet. Dieser Zahnlückengrund wird jedoch bei allen Zahnlücken und über die gesamte axiale Länge der Zahnlücken wesentlich erweitert und in den Ausführungsbeispielen durch Zahnlückengrund 30 gebildet. Zahnlückengrund 30 stellt in den Ausführungsbeispielen den halben Mantel eines Kreiszylinders dar, dessen Achse jeweils auf der Symmetrieebene der Zahnlücke und im wesentlichen auf dem Wälzkreis oder geringfügig radial außerhalb des Wälzkreises 7 des Hohlrades liegt. Darüber hinaus ist der Zahnlückengrund an seinen beiden Enden noch einmal mit einer trichterförmigen Erweiterung 26 versehen. Die trichterförmige Erweiterung 26 erstreckt sich radial bis nahezu an den Außenumfang des Hohlrades. Die trichterförmige Erweiterung 26 kann sich auch in Umfangsrichtung erstrecken. Sie liegt jedoch jedenfalls radial außerhalb des Wälzkreises 7 des Hohlrades 1. Wenn bei einer erfindungsgemäßen Pumpe der Ölaustritt nur einseitig vorgesehen wird, so befindet sich auch die trichterförmige Erweiterung nur an der betreffenden Seite.

For the design of the bottom of the tooth gaps in the ring gear 1, the following results from FIGS. 3 and 4:

• The teeth of the ring gear are manufactured according to a toothing law, which will be discussed later. This ideal tooth space base, which is created according to the gearing law, is shown in dotted lines for a tooth space and designated 29. However, this tooth space base is significantly expanded for all tooth spaces and over the entire axial length of the tooth spaces and is formed by tooth space base 30 in the exemplary embodiments. In the exemplary embodiments, tooth space base 30 represents half the shell of a circular cylinder, the axis of which lies on the plane of symmetry of the tooth space and essentially on the pitch circle or slightly radially outside of the pitch circle 7 of the ring gear. In addition, the bottom of the tooth space is again provided with a funnel-shaped extension 26 at both ends. The funnel-shaped extension 26 extends radially to almost the outer circumference of the ring gear. The funnel-shaped extension 26 can also extend in the circumferential direction. However, it is in any case radially outside of the pitch circle 7 of the ring gear 1. If the oil outlet is only provided on one side in a pump according to the invention, the funnel-shaped extension is also only on the relevant side.

The outlet openings 48.1 to 48.5 now extend radially in any case so far outwards that they also cover the funnel-shaped extensions 26 on the end faces of the outer wheel 1.

5, only one of these outlet openings can be seen in each cover 32, 33. These outlet openings are designated there by 48. Each of the outlet openings is connected to an outlet channel 49 drilled in the cover 32, 33. The outlet channel is also directed radially outwards, as shown in FIG. 2. Therefore, each outer channel 49 opens on the outside of the cover 32 or 33 as close as possible to the housing 31. The outlet channels do not necessarily have to be drilled through the cover with a radial component. It is e.g. it is also possible that the outlet channels are designed as radial grooves in the side of the cover 32 or 33 facing the gearwheels and then open into the outlet bores 52 of the outlet chamber 51 through an axial branch channel in the respective cover.

An outlet housing 50 is placed pressure-tight on each cover 32, 33. Each outlet housing 50 forms an outlet chamber which is connected on one side to the outlet openings 48.1, 48.3, 48.5 and on the other side to the outlet openings 48.2, 48.4 each via a pressure channel 49 and a bore 52. The bores 52 (cf. FIG. 4) are each closed by a check valve, with the exception of that bore which is connected to the outlet opening 48.5. The outlet opening 48.5 is located at the end of the pressure zone immediately before the pitch point. Both outlet chambers are connected to the common pressure channel 56.

The check valves on both sides are formed by an n-shaped plate, which is screwed against the wall 53 of the outlet housing 50. The tongues protruding from the common crossbeam 55 of the check valve 54 cover the bores 52. Therefore, these tongues act as check valves. Each check valve only releases the connection from the respective pressure cell formed between the teeth via one of the outlet openings 48, pressure channels 49 and bores 52 if the pressure of the outlet cell is at least equal to the outlet pressure in the outlet chamber 51. The last and smallest pressure cell is directly connected to the outlet chamber via opening 48.5 and corresponding channels 49, 52.

4, the teeth of the ring gear 1 are asymmetrical. First, both flanks of each tooth are formed according to a special toothing law. This interlocking law ensures that there is a high degree of coverage that is greater than 2, preferably greater than 3. This has the effect that the teeth are in engagement with one another in approximately the entire rotational range between the intersection of the two tip circles 5 and 9 and the pitch point and, as a result, more than two tooth cells are formed by two successive tooth pairs in each case. These tooth cells are mutually closed in the circumferential direction. This gearing law includes that the driving flanks of the inner wheel 3 and outer wheel 1 also have a correspondingly large degree of coverage. It is now provided that the degree of coverage is less on the driving side of the teeth than on the sealing side of the teeth. This means: The tooth flanks, which lie sealingly on top of each other in the pressure zone between the intersection of the tip circles and the pitch point and form the tooth cells that are sealed off from each other, are produced in accordance with the toothing law described above. These flanks are referred to as sealing flanks in the context of this application.

However, the flanks of the teeth of ring gear 1 and pinion 3, which serve to transmit the torque between inner wheel 3 and ring gear 1 (driving flanks), are produced with a lower degree of coverage, which is preferably between 1 and 2. This is done in that only a partial area of the driving flanks of the outer wheel 1 and / or the inner wheel 3 is produced according to the toothing law (engagement area of the flank). The engagement area 64 of the drive flanks of the ring gear extends radially a little way inward from the pitch circle 7 of the ring gear. The cross-sectional area by which the driving flank of the ring gear deviates from the profile produced by toothing is designated by 65.

The engagement area 66 of the drive flanks of the inner wheel 1 extends radially a little outward from the pitch circle 8. The cross-sectional area of the tooth head by which the driving tooth flanks of the inner wheel 3 recede relative to the ideal tooth profile is designated by 67.

As mentioned, either the driving flanks of the ring gear or the driving flanks of the pinion or both can be provided with such cutouts 65 and 67, respectively. The latter solution has the advantage that only low flow velocities arise on the suction side of the pump. The engagement area 64 of the driving flanks of the ring gear and / or the inner wheel, which is formed according to the gearing law, is dimensioned such that on the one hand at least one pair of teeth of the ring gear and the inner wheel are always in engagement with one another, but on the other hand fewer tooth pairs are in engagement on the driving side than on the Sealing side. The degree of coverage on the engagement side is preferably not greater than 2 due to the correspondingly short design of the engagement areas.

The following again applies to both exemplary embodiments: Each outlet chamber 51 has an outlet which leads into the common lubricating oil channel 56. Each outlet chamber circumscribes in the normal section - as can be seen from FIG. 1 - essentially an annular segment. This ring segment lies essentially on and axially above the cylindrical housing shell 31. The outlet housing is therefore not supported on the deformable part of the cover 33 but on the cylindrical housing shell 31. The center line, the radius of which is the arithmetic mean of the inner radius and the outer radius, preferably lies above the housing jacket. It is even more favorable that the partial areas of the ring segment, which lie on both sides of the housing shell 31, are essentially of the same area. These measures prevent the outlet housing 50 from warping or warping and thereby exerting deforming forces on the covers 32 and 33, respectively.

The embodiment of Figures 3 to 5 also has the advantage that the outlet chambers 51 sit on both sides of the pump housing or the shell 31. Therefore, the compressive forces exerted on the pump housing from the outlet chambers 51 cancel each other out. The pump housing is only loaded symmetrically. Therefore, one-sided deformation and warping of the housing cannot occur. This makes it easier to comply with the necessary tolerances.

• Wenn bei steigender Drehzahl der Druck in Auslaßkammer 51 steigt, so wird zunächst der Bypass 38 verschlossen. Es gelangt nunmehr lediglich noch ein gedrosselter Ölstrom auf die Einlaßseite. Daher werden die Zahnlücken auf der Einlaßseite lediglich noch teilgefüllt. Im übrigen herrscht in den Zahnlücken ein Vakuum. Das hat zur Folge, daß der Druck in den Zahnzellen auf der Auslaßseite zunächst niedriger als der Druck in der Auslaßkammer 51 ist. Daher bleiben die jeweiligen Zungen des Rückschlagventils 54 geschlossen. Mit fortschreitender Verkleinerung der Zellen auf der Auslaßseite steigt der Druck in den Zellen jedoch an. Es öffnet jeweils nur die Zunge des Rückschlagventils, für die der Druck der Zelle größer oder gleich dem Druck in der Auslaßkammer 51 ist. Das hat zur Folge, daß die Pumpe nunmehr lediglich noch eine drehzahlunabhängige, konstante Ölmenge liefert.

About the function of the lubricating oil pump:

• If the pressure in the outlet chamber 51 rises with increasing speed, the bypass 38 is first closed. There is now only a throttled oil flow on the inlet side. Therefore, the tooth gaps on the inlet side are only partially filled. There is also a vacuum in the tooth gaps. As a result, the pressure in the tooth cells on the outlet side is initially lower than the pressure in the outlet chamber 51. Therefore, the respective tongues of the check valve 54 remain closed. However, as the size of the cells on the outlet side shrinks, the pressure in the cells increases. It only opens the tongue of the check valve for which the pressure of the cell is greater than or equal to the pressure in the outlet chamber 51. The result of this is that the pump now only delivers a constant, independent oil quantity.

In addition, the lubricating oil pump also meets other requirements of special operating conditions. For example, occur that the lubricating oil heats up excessively or that engine parts have to be cooled by lubricating oil due to special performance requirements.

In this case, a further short-circuit channel 58 is provided between the inlet 35 of the pump and the oil sump 36. An electromagnetically switched valve 59 is located in this short-circuit channel. This valve is actuated via signal line 60 and amplifier 61 by a temperature sensor 62. The temperature sensor can be used, for example, to measure the oil temperature or the temperature of a machine part, for example a piston.

REFERENCE SIGN LISTING

• 1 outer wheel, ring gear
• 2 internal teeth
• 3 inner wheel, pinion
• 4 external teeth
• 5 tip circle outer wheel
• 6 foot circle outer wheel
• 7 Outer wheel pitch circle
• 8 Internal gear pitch circle
• 9 Head circle inner wheel
• 10 foot circle inner wheel, base circle
• 11 line of engagement
• 12 pitch point
• 13 intersection of the head circles
• 14 tooth height
• 15 gear module, large section
• 16 small section
• 17 center point, outer wheel
• 18 circle of centers of curvature
• 19 center of curvature
• 20 radius of curvature of the line of engagement
• 21 Outer gear pitch radius
• 22 Internal gear radius
• 23 direction of rotation, web
• 24 arrow direction
• 25 center of inner wheel
• 26 funnel-shaped extension
• 27 edge, inner edge
• 28 sealing web
• 29 ideal tooth space reason
• 30 tooth gap reason
• 31 housing
• 32 lids
• 33 cover
• 34 wave
• 35 inlet
• 36 tank
• 37 throttle
• 38 bypass
• 39 pressure control valve
• 40 pistons
• 41 control edge
• 42 spring
• 43 control room
• 44 control line
• 45 inlet
• 46 outlet
• 47 front steering edge
• 48 outlet kidney
• 49 outlet duct
• 50 outlet housing
• 51 outlet chamber
• 52 hole
• 53 wall
• 54 check valve
• 55 crossbars
• 56 pressure channel
• 57 sickle
• 58 short-circuit channel
• 59 valve
• 60 reporting line
• 61 amplifiers
• 62 temperature sensors
• 63 throttle
• 64 area of engagement of the drive flanks of the ring gear
• 65 Deviation cross section of ring gear
• 66 Area of engagement of the drive flanks of the gear
• 67 Deviation cross section

Claims (6)

1. Internal gear pump the gearing of which is designed so that engagement of the teeth basically already commences in the point of intersection of the tips so that in the discharge region the teeth form a plurality of cells which are each closed off from the other, and in which a plurality of discharge channels leave the housing or the rotor, with at least the first discharge channels in the direction of rotation each being closed by a check valve and being spaced apart in a peripheral direction by a distance which is smaller than or equal to the pitch of a cell formed by the teeth simultaneously in engagement, characterised in that a discharge chamber (51) lies on one of the covers (33) of the pump axially above the cylindrical housing shell (31) of the pump and is as a result supported in an axial direction substantially on the cylindrical housing shell (31) of the pump.

2. Internal gear pump according to claim 1, characterised in that the discharge channels (49) are guided radially outwards in the cover and are each closed in the discharge chamber by check valves (54) disposed therein.

3. Internal gear pump according to claim 1, characterised in that the discharge chamber (51) in normal section substantially circumscribes a ring segment.

4. Internal gear pump according to claim 3, characterised in that the centre line of the ring segment, which extends along a circle and whose radius is the arithmetical mean of internal radius and external radius, lies axially above the housing shell.

5. Internal gear pump according to one of claims 1 to 4, characterised in that a discharge chamber (51) is placed on each face (cover 32, 33) of the pump housing, that one portion of the discharge channels opens out into one discharge chamber, and that both discharge chambers open out into the common discharge channel (56).

6. Internal gear pump according to claim 5, characterised in that the discharge channels (49) open out alternately from tooth space to tooth space into one or the other discharge chamber (51).

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