EP0225338A1

EP0225338A1 - Variable capacity pump.

Info

Publication number: EP0225338A1
Application number: EP86902794A
Authority: EP
Inventors: Siegfried Hertell; Dieter Otto
Original assignee: Barmag AG; Barmag Barmer Maschinenfabrik AG
Current assignee: Oerlikon Barmag AG
Priority date: 1985-05-09
Filing date: 1986-05-06
Publication date: 1987-06-16
Also published as: US4750867A; JP2598396B2; EP0225338B1; JPS63500112A; WO1986006797A2; DE3666606D1

Abstract

Une pompe à capacité variable hydraulique conçue comme pompe à roue dentée intérieure, dans laquelle les dents de la roue extérieure (1) et de la roue intérieure (5) sont engagées les unes avec les autres entre les points d'intersection des cercles de tête de la denture. Ainsi des cellules de denture sont créées dans la région de sortie. Les cellules de la denture débouchent dans un canal de sortie commun à toutes, par des canaux de sortie (48) qui sont disposés à une certaine distance de la denture et qui sont fermés à chaque fois par une soupape de retenue. L'entrée est reliée au réservoir par deux ou trois canaux, dont le premier est équipé d'un papillon fixe (37), le deuxième est commandé par une soupape de commande de la pression (39) agissant en fonction de la pression régnant dans le chambre de compression (51) et le troisième est commandé par une soupape électromagnétique (59) agissant en fonction d'autres paramètres de fonctionnement.A hydraulic variable capacity pump designed as an inner gear pump, in which the teeth of the outer wheel (1) and the inner wheel (5) are engaged with each other between the points of intersection of the head circles teeth. Tooth cells are thus created in the exit region. The cells of the teeth open into an outlet channel common to all, through outlet channels (48) which are arranged at a certain distance from the teeth and which are closed each time by a check valve. The inlet is connected to the reservoir by two or three channels, the first of which is fitted with a fixed butterfly (37), the second is controlled by a pressure control valve (39) acting as a function of the pressure prevailing in the compression chamber (51) and the third is controlled by an electromagnetic valve (59) acting according to other operating parameters.

Description

Control pump

The invention relates to a control pump for hydraulic fluid, the delivery rate of which is speed-dependent up to a limit value and, moreover, remains essentially constant regardless of the speed. Pumps of this type are in particular designed as vane pumps, the eccentricity of the rotor to the stator being adjustable as a function of pressure.

The associated technical effort is not justified in many cases ^*.

The invention provides a robustly designed control pump in which the control behavior results from its design without additional mechanical devices.

The invention is based primarily on the knowledge that only the internal gear pump is suitable as such a pump.

In this internal gear pump, the teeth are designed so that the tooth flanks of the teeth between the

Intersections of the head circles lie, mesh with one another and therefore form individual cells in their tooth gaps, which are circumferentially closed. In this case, the engagement of the teeth of the outer wheel and the inner wheel or wheels which are assigned to one another is also to be involved

Advantage begin at the intersection of the head circles. Depending on the requirements, it is possible that the Tooth engagement does not extend absolutely exactly to the intersections of the tip circles. It must be taken into account here that an intervention does not necessarily require a mechanically firm contact; rather, gearwheels are already referred to as being in engagement when the distance between their flanks results in such a narrow gap that this takes into account the viscosity of the hydraulic fluid hydraulically as a seal.

The invention further provides that the inlet opening of the pump has a throttling effect. This means that the cross section of the inlet opening is so small or reduced by installing a throttle that for a given pressure drop only a limited amount of flow can flow through the inlet into the pump.

Furthermore, on the outlet side ^'of the pump, an outlet is essentially assigned to each tooth gap which results from the tooth engagement as a closed cell. Several of these outlets open into a common pressure channel. In this case, separate pressure systems can be fed from the remaining outlet channels. If this is not the case, all outlets open into the common pressure channel. With a few exceptions, all outlets are secured by check valves with the direction of flow in the outlet direction. The only exception is the tooth cell closest to the intersection of the head circles or possibly the tooth cell after next. These tooth cells open into the pressure channel. The distance between the outlets corresponds to the tooth pitch or is smaller than the tooth pitch.

There are - in the direction of rotation - several outlets arranged one behind the other and each closed by a valve arrangement. The valve arrangement is designed in such a way that the cells formed in the outlet area are opposite the Only open the pressure chamber if the operating pressure of the pressure channel has also been reached in the respective cell as a result of the progressive compression.

Furthermore, the invention provides a tooth shape which ensures that those in the pressure range, i.e. between the intersections of the head circles, the tooth flanks of the two gears come into such good contact with one another that the gaps formed between two meshing flanks can be described as hydraulically tight and the pump operates silently. The toothing is designed in such a way that the tooth flanks that mesh with one another touch as large a surface as possible or lie opposite one another. Therefore, adjacent tooth cells are sealed from each other by a gap that is as long as possible. For this purpose, the toothing is designed as a cycloid toothing. In a preferred embodiment, the cycloid toothing is designed with a curved line of engagement extending from the pitch point to the intersection of the two tip circles. The radius of curvature of the line of engagement preferably takes on values which lie in terms of their dimensions between the pitch circle radius of the inner toothing of the outer wheel and the pitch circle radius of the outer toothing of the inner wheel or wheels.

The line of engagement can be a curved line with a continuously changing radius of curvature within the specified limits or can lie on a circle, the radius of which is defined within the previously specified limits.

In a form of further training, the selected toothing has a special shape that falls outside the scope of the known, in that the pitch circles are shifted from the usual position. The distance is for the internal toothing of the external gear Between the pitch circle and the tip circle, the distance between the pitch circle and the root circle in the external toothing of the inner wheel or wheels is significantly smaller than the toothing module or the other tooth part. The respectively larger section of the teeth to the smaller section advantageously behaves at least as 2: 1 and preferably as 3.5: 1 to 5: 1.

When the outer wheel is stationary and the inner wheel is rolling, the center of curvature of the line of engagement describes an arc. This means that when the inner wheel is stationary and the outer wheel is rolling, the lines of engagement assigned to the individual teeth of the outer wheel, which are congruent to one another, each lie on an associated circle, the individual center points of the circle lying on a circle concentric with the outer wheel.

The invention provides a gear pump which has a delivery and output characteristic that increases with the speed only up to a certain speed. at

If this speed is exceeded, the rotating cells are only partially filled, and the filling decreases with increasing speed. Adverse consequences of the cavitation which arises as a result, and in particular the generally feared cavitation erosion, are avoided by the inventive selection of only those gear pumps which have cells which are sealed off relative to one another, and by the inventive design of the outlet region with a plurality of outlet openings arranged in the circumferential direction, which are provided by check valves are closed. As a result of this embodiment of the invention, the only partially filled cells come into contact with the pressurized cells and the pressure chamber only when the pressure of the partially filled cell has reached the system pressure. This avoids cavitation implications. The partial filling of the cells in the inlet area results from the throttling of the inlet channel which is always present there and which allows only a limited inlet oil flow which is not sufficient to completely fill each cell in the filling time predetermined by the pump speed. However, throttles adapted to the application and operational purpose of the pump can also be used in the inlet duct. In particular, in an advantageous further development of the invention, it is possible to design the throttle in an adjustable manner, so that the delivery capacity of the pump can be adapted to the respective requirement. It is also advantageous to install a throttle that is adjustable in this way in a control circuit, by means of which the delivery rate is kept constant or is adapted to a predetermined desired value. For this reason, the control pump according to this invention is also advantageously used as a lubricating oil pump for use in motor vehicles.

Such internal combustion engines are distinguished on the one hand by the fact that they are operated with very different and constantly changing operating parameters, starting from idling up to maximum load operation at the highest speeds. The lubricating oil system must therefore meet the maximum load conditions, but on the other hand should not consume unnecessarily much energy in the lower load ranges.

A requirement of such an internal combustion engine is also that it has a long service life without professional maintenance. This is opposed to the fact that the internal combustion engine is subject to wear, which leads to an increase in the consumption of lubricating oil and to a drop in pressure in the lubricating oil system. The lubricating oil pump must therefore also be adapted to this increasing demand over the course of the service life. This means that this proportion of the lubricating oil pump that is not required leads to corresponding energy losses. The invention provides a lubricating oil system that on the one hand has a sufficient amount of lubricating oil in all. Provides operating conditions, on the other hand avoids unnecessary, lossy funding.

The invention therefore now provides that this throttle is bypassed by a bypass channel and that there is a valve in the bypass channel which is controlled by the outlet pressure of the control pump and which opens the bypass when the pressure in the outlet channel drops.

In this control system, the throttle is set so that the oil tight, which is promoted by the control pump, depends on the speed only up to a certain speed. This will e.g. taken into account the fact that the lubricating oil consumption of an engine in the lower speed ranges is speed-dependent. On the other hand, it is taken into account that the dependence of the lubricating oil consumption on the rotational speed only exists up to a certain rotational speed. This threshold speed can be specified by dimensioning the throttle.

On the other hand, the control system can be used by everyone, e.g. Adjust the increased demand caused by wear by determining the pressure drop and using it to open a bypass. By opening the bypass, the entire delivery capacity or an additional portion of the delivery capacity of the control pump can be accessed.

In an advantageous embodiment it is provided that only an increased proportion of the conveying capacity is tapped through the bypass. In addition, the possibility is to be created to meet a special need by further increasing the funding, which is not dependent on pressure. This is the case with motor vehicle engines, for example possible to increase the lubricating oil circulation if the lubricating oil temperature exceeds a certain value (threshold temperature). For this purpose, another short-circuit channel is provided in the inlet, which is actuated by an electromagnetic valve.

The invention is described below using an exemplary embodiment.

Show it

1, 2 the radial section and axial section; Fig. 3 as a detail of Fig. 1, the execution of the toothing.

The outer wheel 1 is freely rotatably mounted in the housing 31. The outer wheel 1 has internal teeth 2. The cylindrical housing 31 is closed on both sides by the covers 32 and 33. The shaft 34 is rotatably mounted in the cover 32 and driven by a motor, not shown. The inner wheel 3 is rotatably mounted on the shaft 34. The inner wheel 3 has an external toothing 4 which is in engagement with the internal toothing 2 of the outer wheel 1. In the cover 33 there is the inlet channel 35 (see also FIG. 1). The inlet channel 35 is connected to the tank 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 tank 36 with its control edge 41. The piston is on one side with one Spring 42 loaded. On the opposite

On the side, the piston in control chamber 43 is acted upon by the outlet pressure via control line 44. The outlet side of the pump will be discussed later. The function of the pressure control valve 39 as a function of the outlet pressure is described below. As long as no or only a small one Exhaust pressure prevails in the control line 44 and the control chamber 43, the piston with its control edge releases the flow from the inlet 45 to the outlet 46. Oil can now flow from the tank 36 to the pump both via the throttle 37 and the bypass channel 38. When the pressure in the control chamber 43 increases and the spring force overcomes, the inlet is closed off from the outlet 46. Now only a throttled oil flow flows through the throttle 37 from the tank 36 to the inlet 35 of the pump. If the outlet pressure rises further, the pressure control valve acts as a pressure limiting valve. The spring 42 is compressed so far that the front control edge 47 opens the pressure line 44 opposite the outlet 46 to the tank.

To the outlet side of the pump:

The pump forms - as shown in FIG. 1 - on the outlet side '• between the intermeshing teeth of the outer wheel 1 and the inner wheel 3 four cells which are closed in the circumferential and axial directions and have been filled with oil via the inlet channel 35. In the cover 32 there are four outlet ^Kidney 48.1, 48.2, 48.3, 48.4 introduced. 2 shows only one of these outlet kidneys. This outlet kidney is designated there by 48. Each of the outlet kidneys 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 outer channel 49 opens on the outside of the cover 33 as close as possible to the housing 31. An outlet housing 50 is placed on the cover 33 in a pressure-tight manner. The outlet housing 50 forms an outlet chamber which is connected to the outlet kidneys 48.1 to 48.4 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 sheet 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 which only connect the respective pressure cell formed between the teeth, via outlet kidney 48, the respective pressure channel 49 and bore 52 release when 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 connected directly to the outlet chamber via kidney 48.4 and corresponding channels 49, 52.

The outlet chamber 51 has an outlet which leads into the common pressure channel 56.

How the pump works:

At low pressure in the outlet chamber 51, the spring 42 displaces the piston 40 - in FIG. 2 - to the left. The pump now acts like a normal internal gear pump. The oil flow flows through throttle 37 and bypass channel 38 to the inlet. Sufficient tooth gaps are filled to the maximum and expressed again on the outlet side. Whether the filling is complete or only partial depends on the throttle resistance of the throttle 37 and the bypass channel 38. In Fig. 2, the throttle 63 is shown symbolically, which indicates that the bypass 38 also causes throttling, which at high speeds can lead to the fact that the tooth cells are only partially filled. This will be referred to later.

When the pressure in the outlet chamber 51 increases, the bypass 38 is first closed. Now there is only a strongly restricted oil flow on the inlet side. Therefore, the tooth gaps on the inlet side are only partially filled or filled even less. There is also a vacuum in the tooth gaps. As a result, the pressure in the tooth cells on the outlet side initially is lower than the pressure in the outlet chamber 51. Therefore, the tongues of the check valve 54 remain closed. However, as the cells on the outlet side continue to shrink, 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 consequence of this is that the pump now only delivers a speed-independent, constant oil quantity. It is therefore not necessary, even with increasing speed, to discharge an excessive amount of oil with corresponding power losses, as is the case with conventional systems. The pump is therefore particularly suitable for motor vehicles, in particular as a lubricating oil pump in motor vehicles. If the lubricating oil requirement increases, e.g. due to wear and tear

Threshold pressure in the Ste erdruckkammer 43 only reached at higher speed. Therefore, the bypass 38 is also closed later. As a result, the lubricating oil pump automatically adapts to an increased demand. The lubricating oil pump therefore meets the increasing lubricating oil requirement over the entire service life of the motor vehicle engine. On the other hand, the lubricating oil pump works economically even with a new engine with a relatively low lubricating oil requirement, since this lubricating oil pump avoids that an unneeded feed component must be returned to the sump with losses.

In addition, the control pump also meets other requirements of special operating conditions. For example, occur in motor vehicle engines that the

Lubricating oil is excessively heated or that engine parts have to be cooled by lubricating oil due to special performance requirements. In this case, as shown in FIG. 2, a further short-circuit channel 58 is provided between the inlet 35 of the pump and the tank 36. In this short-circuit channel lies an electromagnetically switched valve 59. This valve is actuated via signal line 60 and amplifier 61, for example 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. It is also possible to use a different measuring instrument, for example a speed counter, instead of the temperature sensor 62. The alarm line can also be used to record other extraordinary operating conditions. In any case, the valve 59 serves the purpose of meeting an extraordinary need. It is assumed here that the sum of the oil flow, which is conveyed by throttle 37 on the one hand and via bypass 38 on the other hand, is still throttled and therefore, despite the pressure control valve 39 being open, only a partial filling of the cells of the internal toothing takes place at speeds that exceed a certain threshold speed lie. Fig. 2 meets this requirement in that a further throttle 63 is indicated in the bypass 38.

It has already been pointed out that the effectiveness of the pump depends on the toothing being designed in such a way that the teeth in the outlet area between the intersections of the head circles are in engagement with one another and - taking into account the viscosity of the hydraulic oil - form closed cells.

Fig. 3 serves to explain the toothing, which is preferably used in the context of this invention.

The outer wheel 1 has an internal toothing 2, in which the inner wheel 3 meshes with its external toothing 4. In relation to the fixed external gear 1, the internal gear 3 rotating in the direction of arrow 24 moves in the direction of arrow 23. The pitch circle 7 of the outer gear is just like the pitch circle 8 of the inner wheel 3 in relation to the tooth height 14 and the center points 17 and 25 of the pitch circles in the direction of the center points 17 and 25, whereby a small section 16 of the teeth 2 and 4 and a substantially larger section 15 are formed, which complement each other to the tooth height 14 which is practically the same for both wheels 1 and 3. The distance between the pitch circle 7 and the root circle 6 of the outer wheel 1 and between the pitch circle 8 and the tip circle 9 of the inner wheel 3 is preferably at least twice the distance between the pitch circle 7 and the tip circle 5 for the outer wheel 1 or the distance between the pitch circle 8 and the base circle 10 of the inner wheel, the ratio of the dimensions between the two tooth sections 15 and

16 preferably has a value between 3.5: 1 and 5: 1.

The through the pitch 12 and. The line of intersection 11 of the intersection 13 of the head circles 5 and 9 lies on a circle with the radius 26 which starts from the center 19 of the circle. If the inner wheel rolls on the stationary ring gear, the center of curvature 19 describes a circle 18 which is concentric with the pitch circle 7 of the outer wheel. The connecting straight line 21 between the center point of the ring gear

17 and the respective pitch point 12 intersect this circle at the current center of curvature. The radius of the circle 18 is determined by the specified conditions. The resulting form of gearing solves the task in an outstanding manner.

REFERENCE CHARACTERISTICS

Outer wheel inner toothing Inner wheel outer toothing Head circle Outer wheel Foot circle Outer wheel Rolling circle Outer wheel Rolling circle Inner wheel Head circle Inner wheel Foot circle Inner wheel, basic circle Interference line pitch point Intersection of the tip circles Tooth-high toothing module, large section Small section center point, Outer wheel circle of centers of curvature Center of curvature Center point of curvature Radius of the meshing line pitch circle gear radius, center of curvature Inner wheel radius of engagement line

Housing cover cover wave

Inlet

tank

throttle

bypass

Pressure control valve

piston

Control edge- ^'

feather

Control room

Control line

Inlet

Front control edge outlet

Outlet kidney

Exhaust duct

Outlet housing

Outlet chamber

drilling

wall

check valve

Crossbar

Pressure channel

sickle

Short-circuit channel

Valve •

Reporting line

amplifier

Temperature sensor

throttle

Claims

PATENT CLAIMS

1. Control pump for hydraulic fluid, the Fδrdermenge is speed dependent up to a limit value and is also controllable independently of the speed, characterized in that the control pump is an internal gear pump in which each tooth gap in the inlet area of the pump of the internal toothing via an inlet opening, possibly equipped with a throttle, with the oil supply and each tooth gap in the internal toothing located in the outlet region of the pump via outlet openings which are secured by non-return valves and whose spacings in the circumferential direction are as large as or smaller than the tooth division, are connected to the pump outlet, and in which the toothing is designed such that the tooth flanks are in engagement with essentially all teeth which lie between the intersections of the tip circles,

2. Control pump according to claim 1, characterized in that the toothing (2, 4) is a cycloid toothing.

3. Control pump according to claim 2, characterized in that the cycloid toothing has a curved line of engagement (11) which essentially runs through the intersections (13) of the two tip circles (5; 9) and whose radius of curvature (20) values between the pitch circle radius ( 21) of the inner toothing (2) of the outer wheel (1) and the pitch circle radius (22) of the outer toothing (4) of the inner wheel (3).

4. Control pump according to claim 3, characterized in that the line of engagement (11) is a circle whose radius (26) has a value between the pitch circle radii (21; 22) of the meshing gears (1, 3).

5. Control pump according to one of claims 1 to 4, characterized in that the engagement of the mutually associated teeth (2; 4) of the internal toothing (2) of the outer wheel (1) and

External teeth (4) of the inner wheel (s) (3) already in the area of the intersection (13) of the head travel (5, 9) begins.

6. Control pump according to one of claims 1 to 5, characterized in that in the internal toothing (2) of the ^' external gear (1) - the distance (16) between the pitch circle (7) and tip circle (5), in the external toothing (4) the or the .Internal gears (3) the distance (16) between the pitch circle (8) and the root circle

(10) is smaller than the gear module.

7. Control pump according to claim 6, characterized in that the corresponding larger toothed module section (15) of the teeth (2; 4) relates to the respective smaller section (16) of the teeth (2; 4) as at least 2: 1 and preferably like 3.5: 1 to 5: 1.

8. Control pump according to claim 3 or 4, characterized in that with a stationary outer wheel (1) and rolling inner wheel (3) the curvature, center (19) of the line of engagement

(11) describes an arc (18).

9. Control pump according to one of the preceding claims, characterized in that a constant throttle sits in the suction channel of the pump, which is bypassed by a bypass channel with a pressure-controlled valve when the pressure in the outlet channel exceeds a threshold value.

10. Control pump according to claim 9, characterized in that the pressure-controlled valve has a pressure control chamber which opens when a maximum permissible pressure in the outlet channel to the tank is exceeded.

11. Control pump according to claim 9 or 10, characterized in that the inlet of the pump is connected to an unthrottled inlet channel which is opened or closed to cover a particularly high demand by an electromagnetically operated valve.