JPH04255584A - Internal gear pump for hydraulic fluid - Google Patents

Abstract

PURPOSE: To design an internal gear pump wherein an outer gear having no rotors is provided so as to be eccentrically rotated, and the entire engaging region of the gear is prevented from being short-circuited with an entrance so as to utilize an entire entrance as a sending-out/discharging chamber. CONSTITUTION: An outer gear 14 partially covers an entrance chamber 28, rotary crescent-shaped entrance face 27 is released, the entrance face is extended over a center angle measured on the axis 13 of a pump, and this center angle is smaller than the sum of a pitch angle and the center angle of a rotary crescent-shaped chamber 3 limited by the tip circle of the gear in a side opposite an eccentric side, which is measured on the pump axis.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION The present invention relates to a gear pump according to the preamble of claim 1.

0002

[Prior Art] The above-mentioned pump is DE-OS344.
8253 (pp-1372).

[0003] External gears are supported in cutouts in the rotor. The rotor is also rotatably mounted in a chamber formed by an internal gear and filling this chamber. The known pump has a cylindrical inlet chamber located in the end wall as an inlet, as well as a passage system arranged in the rotor, which are in continuous communication.

[0004] This configuration is advantageous only if the entire interior space bounded by the tip circle of the internal gear is filled by the rotor insofar as it lies outside the meshing area of the teeth.

[0005]

[Problems to be Solved by the Invention] An object of the present invention is to configure an internal gear pump without a rotor but with an externally geared gear that rotates eccentrically. The aim is to design such that the entire meshing area is not short-circuited with the inlet area and can therefore be used in its entirety as delivery chamber and discharge chamber.

[0006]

The above object is achieved by the features of claim 1.

[0007]

In the arrangement according to the invention, the annular inlet chamber is covered by a rotating gear in such a way that the meshing region does not connect with the inlet on the discharge side.

The arrangement according to claim 3 and especially claim 4 ensures good lubrication and cooling on both sides of the eccentric, which is still loaded. It is also important for plain bearing mounted eccentrics that the pressure be equalized.

[0009] According to the measures according to claim 5, it is avoided that the rotating force generated by the rotation of the external gear and the discharge area acts on the drive shaft and causes bending of the shaft and tilting of the external gear.

According to the configuration according to claim 6 and/or claim 7, good cooling and lubrication of the eccentric body is achieved, and the eccentric body is subjected to heat and friction loads on the inside and outside by the sliding bearing portion.

A further intensification of the cooling is achieved by the measures of claim 8.

[0012] In a particular embodiment, it is advantageous if the delivery characteristic curve of the pump is such that, with increasing rotational speed, it first rises rapidly, then remains constant and then falls again. Such a characteristic curve is particularly suitable for motor vehicle hydraulic systems.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A pump casing is composed of a casing peripheral wall 1 and end plates 2 and 3, the end plates overlapping each other. The casing peripheral wall 1 has a perfectly circular cylindrical inner chamber, and an annular groove 4 is cut into the cylindrical inner peripheral surface of the inner chamber. An internal gear 6 is fixed to the web 5 left on the side. The entire package consisting of the housing jacket 1, the end plates 2, 3 and the internal gear 6 is held together by a screw connection 7. The screw connection 7 passes through the internal gear in the region of the tooth tip by means of a bore 8 .

The internal gear has internal teeth. The internal space of the pump is bounded by the tip circle 9 of the internal gear by internal teeth. A pin 10 is fixedly inserted into the end plate 3 with one end. The other end of the pin 10 projects into the inner chamber of the pump. An eccentric body 11 is rotatably supported on the pin 10. The axial width of the eccentric body is approximately equal to the axial widths of the casing peripheral wall 1 and the internal gear 6. The eccentric body has a perfectly circular cylindrical outer circumferential surface, and its central axis is indicated by reference numeral 12. The eccentric body rotates around the axis 13 of the pin 10 with an eccentricity E. An external gear 14 is rotatably supported on the eccentric body 11. The external gear 14 has external teeth. The eccentricity E of the eccentric body and the external teeth of the external gear are designed so that the external teeth of the external gear mesh with the internal teeth of the internal gear, and a tooth profile portion is formed.

Therefore, the tip circles 9 and 15 of the tooth profile intersect at rotating intersection points 21 and 22. As a result, on the inner circumferential surface of the addendum circle 9 of the internal gear, a meshing region is created between the intersection points 21 and 22 that rotates toward the side where the eccentricity E of the axis 13 is located, and on the other hand, the meshing region rotates toward the side where the eccentricity E of the axis 13 is located. On the opposite side there is created a crescent space 23 in which the pump rotates.

The tooth profile portion is formed so that the teeth of the internal gear and the external gear closely mesh with the tooth surfaces between the intersection points 21 and 22 of the addendum circles 9 and 15. Therefore, the intersection 21,2
A plurality of displacement chambers are created in the meshing region between the two, which are sealed against each other and against the crescent space 23 on the side opposite to the eccentric side by contact of the tooth surfaces.

A drive shaft 16 is used to drive the pump. The drive shaft 16 is rotatably supported in the other end plate 2 concentrically with respect to the axis 13 of the pin 10, and its end ends approximately in line with the inner surface of the pump chamber. There is. Here, the drive shaft 16 forms an end surface, and a connecting piece 17 is eccentrically fixed to this end surface. This connecting piece 17
protrudes axially into the entrainment pocket 18, which is formed in the end face of the adjacent eccentric 11 in the eccentric region.

The pump has an approximately radial inlet passage 19 in the end plate 3 as an inlet. The entrance passage is distribution room 20
The distribution chamber concentrically surrounds the pin 10. The distribution chamber is formed as a perfect circular cylindrical notch in the end face of the end plate that limits the pump chamber. The radius of the distribution chamber is smaller than the radius FJ of the root circle of the external gear.

Another perfect circular cylindrical notch is formed concentrically with the axis 13 on the end surface of the opposite end plate 2 . This cutout is used as the entrance chamber 28. Distribution chamber 20 and inlet chamber 28 are connected to each other by a passage. The passage passes axially through the eccentric. These channels are preferably designed as grooves in the inner bore of the eccentric and are used for lubrication of the plain bearing of the eccentric on the pin 10 as well as for cooling the eccentric 11. The entraining pocket 18 is used as such a passage, so that it passes axially through the eccentric body 11 and its outer edge lies on a circumference with a radius slightly larger than the radius of the shaft. It is particularly advantageous if this passage is on the eccentric side of the eccentric axis. This is because on this side there is also a discharge side, so that the eccentric is here particularly exposed to pressure, friction and, therefore, heat loads. Heat can be removed from this axial passage located in the eccentric region. Furthermore, a plurality of such passages can also be provided. Additionally or alternatively, the axial passage can also be used to improve the lubrication of the plain bearing. These passages are used for lubrication of the plain bearing of the external gear on the eccentric as well as for the plain bearing of the eccentric on the stationary pin 10. Two further such lubrication channels 29 can be seen in FIG. 2 in the plain bearing area of the external gear. The lubrication passages 29 are each offset by 60° in the circumferential direction of the circumferential surface of the eccentric body 11. Suitable channels can also be provided in the inner bore of the eccentric, so that the oil flow through these lubrication channels 29 and entrainment pockets 18 provides a symmetrical distribution of the oil and at the same time hydrodynamic support of the eccentric. However, this oil flow also has the effect of cooling the eccentric body. This cooling effect is particularly important since the eccentric itself is rotatably supported in the inner bore and the outer peripheral surface is used as a rotatable support for the external gear.

Another means of cooling (which additionally
or can be used instead) annular passage,
That is, on the side of the inlet chamber 28 and/or the distribution chamber 20, the eccentric body is slightly thinner than the internal width of the external gear or the casing wall 1. In this case, an annular surface is formed on the end face of the eccentric, which is filled with oil and in which a constant oil flow occurs. This configuration of the eccentric is illustrated in FIG. 3 by lines 34, 35, which indicate the end faces of the eccentric.

The radius R of the outer diameter of the inlet chamber 28 (relative to the axis 13 of the pin 10) must be kept according to the invention within a certain range, as will be explained later. The radius R of the outer diameter of the entrance chamber 28 is designed such that the root circle FJ of the external gear or the circular area surrounded by this root circle covers the entrance chamber 28 except for the crescent-shaped entrance surface 27. . Part of the inlet surface is also covered by the sides of the teeth of the external gear. The inlet faces co-rotate on the side of the inner chamber opposite the eccentric side.

Due to the design according to the invention of the radius R of the outer diameter of the inlet chamber 28 on the one hand and the root circle FJ of the external gear on the other hand, the crescent-shaped inlet face 27 is formed by one of the closed displacement chambers of the meshing region. Not being covered is achieved. This avoids the dead distance of these displacement chambers in the discharge area and improves the hydraulic efficiency.

The outlet passage 24 is located radially in the housing jacket 2 and is connected to the circumferential groove 4 in the housing jacket. This circumferential groove is bounded on the inside by the outer circumferential surface of the external gear and forms an outer chamber.

[0024] The internal gear has at least one gear in each tooth groove area.
It has two exit holes 25. FIG. 1 shows that two outlet holes 25.1, 25.2 are arranged axially in each tooth groove. The outlet holes are each arranged in parallel radial planes. Each radial plane is covered by an elastic valve ring 26.1, 26.2, which covers all outlet holes in the vertical plane and is divided in the axial plane. One end of the valve ring is fixed, for example by a rivet, and the other end is freely movable. These valve rings 26.1, 26.2 act as check valves for each outlet hole.

Next, the operation will be described.

The drive shaft 16 is driven in the direction of rotation shown by an arrow 31. At this time, the connecting piece 17 engages in the entraining pocket of the eccentric and entrains the eccentric. This causes the external gear to perform a tottering movement within the inner chamber of the pump, causing the external gear to rotate in the direction indicated by the arrow 32 as a result of the meshing of its tooth profile with the tooth profile of the internal gear. The external gear and the tooth profile of the internal gear form a plurality of displacement chambers between the intersection points 21 and 22 of both addendum circles, and the displacement chambers continuously expand and contract. In the subsequent region, the displacement chamber expands until it opens and communicates with the oil-filled crescent chamber. The displacement chamber is reduced on the leading side of the external gear. The oil is therefore under pressure here. If the pressure in the displacement chamber exceeds the system pressure prevailing in the circumferential groove 4, here the valve rings 26.1 and 26.2 close to the outlet hole 2 due to the pressure difference.
5.1, 25.2, so that oil can be ejected from the displacement chamber.

Due to the negative pressure generated on the inlet side, the oil flows into the distribution chamber 2.
0 and the inlet passage 19 through the lubricating channels 29, 30 on the outer peripheral surface of the pin 10 and the entraining pocket 18 to the inlet chamber 28.
It is sucked in from. As a result, a good lubricating film is formed in the area of the plain bearing of the eccentric body 11, which serves both for lubrication and for hydrodynamic support.

The outer diameter of the inlet chamber 28 is designed such that the displacement chamber is not connected to the inlet chamber 28 on the discharge side. The inlet chamber 28 is covered in the discharge region by the end face of the external gear, ie by the face surrounded by the root circle and the face described by the tooth crests. Therefore, on the outside the entrance chamber 2
The width of the crescent-shaped inlet surface 27, which is limited by the circumferential surface of 8 and on the inside by the tooth root circle of the external gear, is one pitch larger than the width of the crescent-shaped inner chamber 23, which is limited by both tooth tip circles. It's okay. The width and pitch width of the crescent-shaped interior chamber are each determined as a central angle with respect to the central axis 13 of the pump.

The pump can advantageously also be used as a pump which is throttled on the suction side. In this case, the inlet channel 19 is provided with a throttle 33 . Because of this throttling, only a limited amount of oil can be sucked in for a limited amount of time. This time-limited suction amount is sufficient to completely fill the pump up to a predetermined rotational speed. Therefore, up to this rotation speed, the pump discharge amount is proportional to the rotation speed. An increase in the rotational speed no longer results in a further increase in the delivery volume. Therefore, an increase in rotational speed is not associated with increased oil consumption. This pump is therefore suitable for motor vehicle actuators whose oil requirements are independent of highly variable engine speeds.

Instead of or in addition to the throttle 33 in the inlet channel, the inlet face 27 can be designed so small that the throttle effect necessary for suction throttle adjustment takes place here. As a result, the sealing member 36 in the area between the drive shaft 16 and the casing end plate 2 may be spared from the load of the pressing force.

The radius of the distribution chamber 20 can be determined similarly to the radius of the inlet chamber 28. In this case, the pump is filled both via the distribution chamber and via the inlet chamber. In this case, a discharge characteristic curve is obtained in the suction-side throttle that first increases steeply with the rotational speed, but then becomes constant regardless of the rotational speed. Such a characteristic curve is suitable wherever a constant hydraulic force, independent of engine speed and vehicle speed, has to be applied in the hydraulic system of a motor vehicle.

However, the radius of the distribution chamber can also be designed such that it does not communicate with the discharge chamber formed by the toothing. In this case, the pump is filled exclusively via the inlet chamber 28. In this case, the suction side throttle of the pump first rises steeply with the rotation speed, then breaks off, and remains almost constant over the rotation speed range,
A discharge characteristic curve is then obtained which again descends with rotational speed. Such characteristic curves are used in the field of automobile hydraulic systems.
It is suitable wherever only reduced hydraulic forces have to be applied at high vehicle speeds or engine speeds (for example, this is the case in steering aids).

[Brief explanation of the drawing]

FIG. 1 is a sectional view including the axis of the pump.

2 shows a cross-sectional view of the pump according to FIG. 1, FIG.

FIG. 3 is a view corresponding to FIG. 1 of a pump in which the end face of the eccentric body has a different configuration.

[Explanation of symbols]

1 Casing peripheral wall 2, 3 End plate 4 Groove 5. Web 6 Internal gear 7 Screw connection member 8 holes 9 Tip circle 10 pin 11 Eccentric body 12 Central axis 13 Axis line 14 External gear 15 Tip circle 16 Drive shaft 17 Connecting piece 18 Entrainment pocket 19 Entrance passage 20 Distribution room 21, 22 intersection 23 Crescent room 24 Exit passage 25.1, 25.2 Exit hole 26.1, 26.2 Valve ring 27 Entrance surface 28 Entrance room 29, 30 Lubrication passage 31, 32 Arrow 33 Aperture 34, 35 End face 36 Seal member

Claims (9)

[Claims] 1. An internal gear pump for hydraulic fluids, in which an internal gear with internal teeth forms a stationary, closed interior chamber and a relatively small external gear with external teeth. The external gear rotates eccentrically with respect to the internal gear along the driven eccentric body (11) and meshes with the internal gear,
The difference in the number of teeth between the internal gear (6) and the external gear (14) is at least 2, and the inlet is provided in the end wall and is concentric with the internal gear and has a perfect circular cylindrical shape. It has a room,
For types in which the radius of the outer diameter of the inlet chamber is smaller than the sum of the eccentricity and the radius of the dedendum circle of the external gear, and larger than the difference between the radius of the dedendum circle of the external gear and the eccentricity, Gear (1)
4) partially covers the inlet chamber (28) and opens a rotating crescent-shaped inlet face (27), which inlet face extends over a central angle measured in the pump axis (13). , this central angle is the pitch angle and the rotating crescent chamber (23
) is smaller than the sum of the central angle measured in the pump axis (13). [Claim 2] A plurality of pairs of teeth are closely meshed each time in the meshing region between the intersection points of the addendum circles, forming a closed displacement chamber, and an outlet closed by a check valve in each tooth groove. 2. The pump according to claim 1, wherein a channel (25) is assigned and a plurality of outlet channels are each assigned to a discharge chamber (4). Claim 3: The eccentric body (11) is connected to the inlet chamber (28) on the one hand;
), and on the other hand abuts a perfect circular cylindrical distribution chamber (20), the distribution chamber is connected to the inlet passage, and the radius of the outer diameter is smaller than the radius of the root circle of the external gear. 3. Pump according to claim 1, characterized in that the distribution chamber (20) and the inlet chamber (28) are connected by an axis-parallel passage (19, 29, 30). Claim 4: The eccentric body is arranged in a passage parallel to the axis (19, 29
, 30), and the passage is located in the eccentric region. 5. The eccentric body (11) is rotatably mounted on a pin (10) fixedly and cantilevered in the casing and concentric to the axis (13) of the pump. The pump according to any one of items 1 to 4. 6. Axis-parallel channels (19, 29, 30) are formed in the form of axial grooves in the sliding bearing of the eccentric on the pin and/or in the sliding bearing of the external gear on the eccentric. 6. The pump according to claim 5, wherein: 7. Pump according to claim 5, wherein the eccentric is narrower on the side of the inlet chamber (28) and/or on the side of the distribution chamber (20) than the external gear (14). 8. The eccentric body is connected to the drive shaft via an eccentric driver (coupling piece 17) of the drive shaft, the driver engaging in the notch (driver pocket 18), 6. Pump according to claim 5, wherein the entrainment pocket serves as a passage between the inlet chamber (28) and the distribution chamber (20). 9. The distribution chamber (20) is smaller than the difference obtained by subtracting the eccentricity (E) of the eccentric body (11) from the radius of the root circle of the external gear (14). Any one
Pumps listed in section.