US3490377A

US3490377A - Pump

Info

Publication number: US3490377A
Application number: US749792A
Authority: US
Inventors: Egon Tittmann
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1967-08-23
Filing date: 1968-08-02
Publication date: 1970-01-20
Anticipated expiration: 1987-01-20
Also published as: DE1653811A1; GB1240328A; FR1573459A

Description

Jan. 20, 1970 E. TITTMANN 3,490,377

PUMP

Filed Aug. 2, 1968 4 Sheets-Sheet 1 .33 Lag Jan. 20, 1970 E. TITTMANN 3,490,377

PUMP

Filed Aug. 2, 1968 4 Sheets-Sheet 2 Jan. 20, 1970 E. TITTMANN PUMP 4 Sheets-Sheet 3 Filed Aug. 2 1968 Jan. 20, 1970 E. TITTMANN 3,490,377

PUMP

Filed Aug. 2, 1968 4 Sheets-Sheet 4 @y /Nl/fA/ra? @p y @an NWA/w AA M 5y United States Patent O 3,490,377 PUMP B 4 0 Int. Cl. F04b 49/08; 23/04; F04f 5/48 U.S. Cl. 103-42 14 Claims ABSTRACT OF THE DISCLOSURE A constant displacement rotary pump wherein a rotor conveys a uid stream from an outlet, through a consumer system and back to an inlet of the pump housing. A passage between the rotor and the inlet accommodates a jet pump having a tube and a nozzle which moves away from the tube and establishes a bypass passage within the connes of the pump housing for recirculation of some uid when the speed of the rotor exceeds a predetermined value. A pressure relief valve opens in response to a predetermined fluid pressure downstream of the rotor and permits some uid to ow through the pump housing and back to the inlet to thereby effect greater displacement of the nozzle and recirculation of a greater quantity of excess uid.

BACKGROUND OF THE INVENTION The present invention relates to pumps in general, and more particularly to improvements in constant displacement rotary pumps. Still more particularly, the invention relates to improvements in constant displacement pumps which can be utilized in power steering for automotive vehicles and wherein the rotor is driven at different speeds by the engine of the vehicle.

In power steering, the pump must deliver fluid at full rates at low r.p.m. (idling) of the engine in order to insure full control of the steering mechanism in parking condition. The pump should deliver fluid at the same rate when the engine operates at lmaximum speed, i.e., under cruising conditions. Such requirements cannot be met by any of the presently known constant delivery pumps. Therefore, pumps used in power steering are normally combined with a ow control device which is a valve serving to divert from the pressure outlet of the pump a certain amount of fluid when the r.p.m. of the engine rises to a predetermined value. Additional problems arise at higher r.p.m. of the engine because the fluid does not lill the intervane chambers of the pump which results in cavitation, generation of noise and a drop in pump output. Therefore, fluid diverted by the iiow control valve is fed to a jet pump which supercharges the suction chamber of the pump.

Patent No. 3,125,028 to Rohde discloses a constant displacement rotary pump wherein the ow control valve is mounted on an elastic diaphragm which is installed in the pump housing between two chambers one of which is maintained at full output pressure and the other of which is maintained at system pressure minus a pressure drop which develops across an orifice installed at the pump outlet. When the pressure diierential attains a certain value, the control valve opens a passage to a jet pump which thereupon supercharges the intake chamber.

A drawback of the just described rotary pump is that its jet pump and flow control valve comprise a large number of parts which must be installed in specially provided recesses machined into the pump housing or into attachments of such housing. This contributes to the initial cost of the pump. Moreover, the efficiency of the Patented Jan. 20, 1970 pump is rather low so that the supercharging effect of the jet pump is rather weak.

SUMMARY OF THE INVENTION It is an object of my present invention to provide a relatively simple, inexpensive and reliable constant displacement rotary pump.

Another object of the invention is to provide a constant displacement rotary pump of the type which can find application in power steering for automotive vehicles and wherein the jet pump performs several important functions to allow for elimination of certain parts which constitute essential components of conventional pumps.

A further object of the invention is to provide a constant displacement rotary pump wherein the jet pump can perform the function of a conventional flow control valve.

An additional object of the invention is to provide a constant displacement rotary pump wherein the jet pump also serves as a means for supplying fluid from the system back to the suction chambers of the rotary pump.

The invention is embodied in a constant displacement pumping apparatus which comprises a housing having an inlet, an outlet and rst and second passages respectively communicating with the inlet and the outlet, a rotor installed in the housing between the first and second passages and Operative to convey a stream of fluid from the outlet, through a consumer system and back to the inlet, drive means for operating the rotor at different speeds whereby the rate of` flow and the pressure of uid in the second passage rise in response to increasing speed of the rotor, a jet pump installed in the first passage and including a tube and a nozzle located downstream of the tube and movable with reference thereto to establish a bypass passage between the second passage and the interior of the nozzle and to thereby permit recirculation of some iiuid in the housing at a higher speed range of the motor, and diiusor means in the iirst passage for supplying to the rotor fluid which enters the housing by way of the inlet and also such fluid which is recirculated through the bypass passage at the higher speed range of the rotor.

The jet pump further comprises a resilient element which biases the nozzle against the tube to thus seal the bypass 4passage at a lower speed range of the rotor.

The novel features which ar-e considered as characteristic of the invention are set forth in particular in the appended claims. The improved pump itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specic embodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a sectional view of a pump which embodies one form of the invention;

FIG. 2 is a sectional view as seen in the direction of arrows fromthe line II-II of FIG. 1;

FIG. 3 is a section on the line III-III of FIG. 2;

FIG. 4 is a section on the line IV-IV of FIG. 1;

FIG. 5 is a section on the line V-V of FIG. l;

FIG. `6 is `an enlarged sectional view of a detail in the pump;

FIG. 6a illustrates a part of the structure shown in a different position;

FIG. 7 is an enlarged sectional view of a detail of a modified pump;

FIG. 7a illustrates the structure of FIG. 7 but with a movable part thereof in a different position;

FIG. 8 is a schematic View of the entire hydraulic system which embodies the pump of FIG. l; and

FIG. 9 is a diagram which facilitates the understanding of operation of the system shown in FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring rst to FIGS. l to 5, there is shown a constant displacement rotary pump whose housing comprises a main portion 10 and a cover portion 11. The latter is airixed to the main portion 10 by screws, bolts or analogous fasteners 11a. The main portion 10 is formed with a relatively large cylindrical cavity 12 which accommodates a cam ring 13 and a pressure plate or thrust plate 14 both held against rotation with reference to the housing by dowel pins 15. The cam ring 13 is disposed `between the cover portion 11 and pressure plate 14 and the latter is biased against the cam ring Iby -a helical expansion spring 16 which reacts against the bottom wall of the main portion 10.

The cover portion 11 is formed with a bore 17 which is coaxial with the cavity 12 and accommodates a rotary drive shaft 18 having an end portion 19 which extends into the interior of the cam ring 13 and is formed with splines which enter complementary grooves in the axial bore of a rotor 20. The axial length of the rotor 20 is slightly less than that of the cam ring 13. As shown in FIG. 5, the internal surface of the cam ring 13 is formed with two substantially sickle-shaped recesses or cutouts 21, 22 which are located diametrically opposite each other. These recesses constitute alternatingly the suction and pressure chambers of the pump. The rotor 20 is formed with several radial slits 23 which extend all the way between its axial ends. These slits receive portions of blades or vanes 24 in such a way that the varies are reciprocable radially but completely lled the corresponding portions of the slits.

The pressure plate 14 is formed with two openings or

holes

25, 26 which are located diametrically opposite each other and at such radial distance from the axis of the pressure plate as to be adjacent to the peripheral surface of the rotor 20. The cross-sectional outlines of

openings

25, 26 are indicated in FIG. 5 by broken lines. The space 27 between the botom wall of the main housing portion 10 and the pressure plate 1'4 constitutes a pressure chamber.

The drive shaft 18 for the rotor 20 has a iiange 28 which is fitted into a counter-bore of the cover portion 11 and is held fagainst axial movement by a washer 29 which is aiiixed to the housing. A seal 30 is provided in the cover portion 11 at the outer side of the washer 29 to seal the interior of the housing from the atmosphere. The housing portion 10 is further provided with a bore 31 Whose axis is parallel to that of the cavity 12 and which communicates with the pressure chamber 27 by way of a connecting port 32. The inner end portion of the bore 31 (i.e., that end portion which is remote from the cover portion 11) accommodates a supercharge tube 33 the right-hand end portion (as viewed in FIG. l) of which is chamfered to form a cone. The left-hand end portion of the tube 33 is formed with axially parallel radially extending slots 34 which extends all the way from its external surface to its internal surface. The slots 34 establish communication 'between the interior of the tube 33 and a bore 36 by way of a connecting port 35. The bore 36 is provided in the main housing portion 10 in parallelism with the bore 31 and communicates with an inlet 37 (FIG. 2) connected to a supply conduit l (FIG. 8) which is also connected to a container or tank B.

The bore 31 further accommodates a noozle 38 which has a piston-like annular ange 39 at one end. The latter is sealingly but reciprocaliy fitted into the bore 31 and is adjacent to the tube 33. The reduced-diameter portion or shank 40 of the nozzle 38, adjacent to the flange 39, extends into an annular seal 41 received in that end of the bore 31 which is adjacent to the cover portion 11. A helical regulating spring 42 operates in the bore 31 between the sealing ring 41 and flange 39 to bias a tapering internal conical surface 43 of the nozzle 38 against the cone at the right-hand end of the tube 33. The flange 39 divides the bore 31 into a left-hand pressure cornpartment 44 and a right-hand pressure compartment 45. The latter accommodates the regulating spring 42.

The connecting port 32 is in communication with a flow control or ow restricting oriice 46 which in turn communicates with a bore 47. The latter communicates with a discharge port or outlet 48. This outlet is connected with one end of a feed conduit l" which conveys uid to a consumer system 49 which, in the present instance, constitutes the working cylinder of a power steering for automotive vehicles (FIG. 8).

The bore 47 is in communication with a ilow restrlcting orice '50 (FIGS. 2, 3 and 8) which connects it with the pressure compartment 45 in the bore 31. The righthand end of the nozzle 38 (as viewed in FIG. l) discharges iiuid into a ditfusor 51 which forms an elbow and branches into two passages '52, 53 which are 1n communication with the suction side of the pump. These

passages

52, 53 have substantially kidney-shaped

end portions

54, 55 which are adjacent to the rotor 20. As shown in FIG. 5, the

end portions

54, 55 alternate with the

openings

25, 26 of the pressure plate 14 and each thereof is located midway between these openings.

The bore 36 is in communication with a bore 56 which in turn communicates with a bore 57 of the main housing portion 10. The bore 57 is parallel to the bore 36 and the bore 56 communicates with a central portion of the bore 57 (see FIG. 4). The latter is further in communication with a bore 58 which connects it with the pressure compartment 45 of the bore 31. At the point where the bore 58 communicates with the bore 57, there is provided a valve seat S9 for the valve member l60 of a pressure relief valve 61. The valve member 60 is biased by a valve spring 62.

The

parts

33, 38, 42 form a jetand venturi pump as well as a iiow regulating valve.

FIG. 8 illustrates the entire hydraulic system. The rotary pump proper (including the -rotor 20 and cam ring 13) is denoted schematically by the character A. The character B denotes the aforementioned tank or container and the just mentioned jet pump (tube 33 and nozzle 38) is indicated at C. The numeral QL denotes the consumer stream, namely, that portion of the discharge uid which flows to the system 49, the character QR the remaining excess stream, and 4the character QP the output of the pump A, i.e., the total discharge uid. Thus, QP equals QL plus QR. In the graph of FIG. 9, the rotational speed (n) of the pump A is measured along the abscissa and the output QP of pump A is measured along the ordinate.

Referring again to FIGS. 1 to 5, it will be noted -that the bore 36, the port 35, a portion of the bore 31, the

paths

52, 53 defined by the difiusor 51, and their

end portions

54, 55, and the chambers 21, 22 constitute a first passage extending between the rotor 20 and the inlet 37. A second passage which extends between the rotor 20 and the outlet 48 is defined by the

openings

25, 26, chamber 27, port 32, orifice 46 and bore 47. When the nozzle 38 moves away from the tube 33, it establishes a bypass passage which connects the second passage with the iirst passage and extends through the compartment 44 so that excess iluid then flows from the port 32, via compartment 44, through the nozzle 38 and into the diffusor 51.

The operation is as follows:

When the r.p.m. of the rotor 20 in the pump A is low, the output QP of this pump equals QL, i.e., all of the discharge fluid iiows from the

openings

25, 26 into the pressure chamber 27, through the connecting port 32 into the orice 46 and thence ito the bore 47 and through the outlet 48 on to the system 49. From the consumer 49, the uid ows through a conduit l, into the tank B to leave the tank B via supply conduit l whence it flows through the inlet 37, bore 36, connecting port 35, slots 34 of the supercharge tube 33, through the tube 33 and nozzle 38, through the diffusor 51,

branch passages

52, 53 and back to the suction side of -the pump A. The pressure of fluid increases in the intervane chambers between the varies 24 of the rotor 20 because the volume of intervane chambers (FIG. 5 between the vanes 24 decreases when the rotor 20 is driven. This causes the fluid to flow to the outlet 48.

The

orifices

46 and 50 cause a drop in fluid pressure so that the pressure of fluid in the compartment 44 exceeds that in the compartment 45. The latter communicates with the orifice 50 by way of the bore 47. The conical internal surface 53 of the nozzle 38 abuts against the conical end portion of the tube 33 under the action of the spring 42.

In the low r.p.m. range of the rotor 20, i.e., up to the point AA in the graph of FIG. 9, the pressure differential between the compartments 44, 45is insutiicient to effect axial displacement of the nozzle 38 against the opposition of the regulating spring 42. Thus, all of the displaced fluid flows to the system 49 and thence back to the pump A. In the absence of specific precautions, suction created by the rotor 20 in the higher r.p.m. range would not sufce to ll the chambers 21, 22 so -that the flow of fluid would be interrupted to cause cavitation with well known undesirable effects.

In the higher r.p.m. range of the rotor 20, (e.g., above 3,000 r.p.m.), the pressure drop at the orifices 46 and 50 (and hence the pressure differential between the compartments 44, 45) rises to a value at which the nozzle 38 is displaced against the opposition of the regulating spring 42. The pressure in the compartment 44 corresponds to full output pressure. When the nozzle 38 moves away from the tube 33, fluid can leave the pressure compartment 44 by flowing around the tube 33 and into the axial passage of the nozzle 38. Such iluid is accelerated in the nozzle whereby the pressure drops, i.e., the

parts

33, 38, 42 then form a flow regulating valve. The output of the rotary piston pump A is then divided into the consumer stream QL and the excess or remaining stream QR. The stream QL ows in a manner as described above, i.e., to the system 49, thence to the tank B and back to the inlet 37 of the pump A. The stream QR flows from the chamber 27 directly into the compartment 44. The pressure of fluid which forms the stream QR corresponds substantially to the output pressure of the pump A. The stream QL remains substantially constant and the rate of fluid flow into the compartment 44 (stream QR) increases in response to increasing width of the gap between the tube 33 and nozzle 38.

Due to suction which develops at the nozzle 38, lluid flowing therethrough is sucked with a higher force to insure that the pump A invariably draws at least such quantities of fluid as are necessary to form the consumer stream QL and that the diffusor 51 receives the full stream QR (i.e., QL plus QR). Thus, no break can develop in the ow of fluid.

The cross-sectional area of

branch passages

52, 53 increases in a direction from the diffusor 51 toward the

end portions

54, 55. Thus, the speed of fluid in these passages decreases whereby the 'iiuid'pressure rises. In other words, a slight coverpressure develops upstream of the chambers 21, 22 to thus prevent cavitation. This is the so-called loading or charging effect and is brought about by the jet pump C.

The jet of fluid which issues from the compartment 44 and flows around the tip of the tube 33 and enters the nozzle 38 resembles a hollow cylinder whose contents flow together in the nozzle to form a funnel-shaped mixing zone. The fluid surrounding such funnel-shaped mixing zone is of highly turbulent character and produces a highly satisfactory suction. The stream QR need not undergo very strong acceleration which reduces the losses in output. Since the stream QR circulates only in the interior of the pump A, such losses in output are important because they contribute to heating of the pump. The losses develop due to acceleration and throttling of uid at the nozzle 38. Since the latter is not subjected to any radial stresses, it cannot jam in the bore 31. In other words, the nozzle 38 is subjected solely to axial stresses (spring 42 and lluid pressure in the compartments 44, 45).

The main purpose of the orifice 46 is to utilize static pressure of increasing output stream QP for regulation of the stream. Such static pressure decreases in response to higher rate of flow of fluid from the outlet of the pump A. In the absence of the orifice 46, pressure in the cornpartment 45 would not drop whereby the quantity of fluid in the consumer stream QL would rise in response to higher r.p.m. of the pump A. The rate of uid flow in the stream QL should remain constant. If the orice 46 is omitted, the hydraulic system can be constructed in a manner as shown in FIG. 6. The total pressure drop Ap between the

compartments

44, 45 is the sum of pressure drops at the

orifices

46, 50.

FIG. 8 illustrates a ifurther orifice 63 which serves as a damper for axial movement of the nozzle 38. A further damper or orifice 64 is provided between the compartment 45 and the bore 58. This damper 64 is shown in FIG. 8.

When the pressure of the consumer stream QL rises to a predetermined maximum value, the valve member 60 of the relief valve `61 moves away from the seat 59. This permits escape of uid from the compartment 45 so that the pressure differential between the 'compartments 44, 45 increases suddenly and the fluid pressure in compartment 44 causes substantial axial displacement of the nozzle 38 against the opposition of the spring 42. Thus, the width of the gap between the tube 33 and nozzle 38I increases suddenly so that more iluid can ow to the suction side of the pump A whereby the pressure at the pump outlet drops. Fluid which ilows through the valve 61 enters the bore -36 by way of the bore 56.

If desired, the secondary stream QR can enter the cornpartment 44 tangentially. This produces a very satisfactory suction.

An advantage of the improved pump is that it need not be provided with a separate flow regulating valve because the function of such valve is performed by the jet pump C. Another advantage resides in the aforedescribed manner in which the fluid flows through the nozzle 38 of the jet pump C.

FIGS. 6, 6a and 7, 7a1 illustrates two embodiments of the tube in the jet pump C. The embodiment of FIGS. 6 and 6a is similar or identical to that shown in FIG. 1. Thus, that end portion of the tube 33` which is adjacent to the nozzle 38 is formed with a conical external surface 33a which tapers in a direction toward the nozzle and is received within the confines of the conical internal surface 43 of the nozzle. The conicity of the external surface 33a exceeds the conicity of the internal surface 43. Therefore, when the jet pump C is closed, the tip of the tube 33 bears aaginst an intermediate portion of the internal surface 43. The character 'F1 denotes the annular end face of the flange 39 in the pressure compartment 44. Since the width of the yannular gap F1' between the surfaces 33ai, 43 increases in response to greater axial displacement of the nozzle 38 away from the tube 33, the rate of flow of the secondary stream QR increases at the expense of the consumer stream QL which is desirable at at higher r.p.m. of the pump A.

In the embodiment of FIGS. 7 and 7a, the end portion of the sleeve 133 has a cylindrical external surface and its tip abuts against the median portion of the conical internal surface 43 of the nozzle 38 when the jet pump C is closed. The width of the gap F1 increases again when the nozzle is caused to move away from the sleeve 133. The latters end portion is formed with an internal conical surface.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can,

by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of my contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

1. In a constant displacement pumping apparatus, a combination comprising a housing having an inlet, an outlet and first and second passages respectively communicating with said inlet and said outlet; a rotor installed in said housing between said passages and operative to convey a fluid stream through a consumer system between said outlet and said inlet; drive means for operating said rotor at different speeds whereby the rate of flow and the pressure of fluid in said second passage rise in response to increasing speed of said rotor; a jet pump in said first passage, including a tube and a nozzle located downstream of and movable with reference to said tube to establish a bypass passage between said second passage and the interior of said nozzle and to thus permit recirculation of some fluid in said housing at a higher speed range of said rotor; and diffuser means in said first passage to supply to said rotor uid which enters by way of said inlet and such fluid which is recirculated through said bypass passage at said higher speed range of the rotor.

2. A combination as defined in claim 1, wherein said first passage includes a bore and said nozzle is slidably received in and divides said bore into first and second compartments in communication with said second passage, and further comprising means for reducing the fiuid pressure in said second compartment below the iiuid pressure in said lirst compartment so that the tiuid in said first compartment tends to move said nozzle with reference to said tube, said jet pump further comprising resilient means for opposing such movement of the nozzle at a lower speed range of said rotor.

3. A combination as defined in claim 1, further comrising ow restricting means provided in said second passage.

4. A combination as defined in claim 1, further comprising means for yieldably biasing said nozzle against said tube to seal said bypass passage at a lower speed range of said rotor.

5. A combination as defined in claim 4, wherein said nozzle has a conical surface which flares outwardly toward and abuts against said tube at said lower speed range of said rotor.

6. A Icombination as defined in claim 1, wherein said nozzle comprises a flange which is slidably telescoped into a portion of said first passage and a reduced-diameter portion adjacent to said flange and reciprocable in an annular seal provided therefore in said first passage.

7. A combination as defined in claim 1, wherein said nozzle is slidably telescoped into and divides aportion of said first passage into a pair of compartments which communicate with said second passage, and further comprising pressure relief valve means provided in said housing and arranged to open in response to a predetermined fluid pressure in one of said compartments to thereby 8 establish communication between said one compartment and said inlet.

8. A combination as defined in claim 7, wherein said housing is provided with a bore connecting said one compartment with said second passage and further cornprising damper means provided in said bore.

9. A combination as defined in claim 7, wherein said housing is provided with a bore connecting said one compartment with said inlet and accommodating said valve, and further comprising damper means in said bore.

10. A combination as dened in claim 1, wherein said first passage includes two suction chambers adjacent to said rotor and said ditusor means comprises a pair of branches each discharging uid into one of said suction chambers. A

11. A combination as' defined in claim 1, wherein said nozzle has a conical internal surface which flares outwardly toward said tube and said tube has a conical external surface which liares outwardly away from said nozzle and abuts against said internal surface to seal said bypass passage in the lower speed range of said rotor, the conicity of said external surface being greater than that of said internal surface. K

12. A combination as defined in claim 1, wherein said nozzle has a conical internal surface which flares outwardly toward said tube, said tubing having a cylindrical external surface which abuts against said internal surface to seal said bypass passage in the lower speed range of said rotor.

13. A combination as defined in claim 1, wherein said nozzle is designed to accelerate and to thus reduce the pressure of recirculated fluid so as to draw fiuid from said tube by suction and wherein the uid entering said diffusor means is decelerated so that its pressure rises upstream of said rotor to thus prevent cavitation at higher rotational speeds of the rotor. I

14. A combination as defined in claim 13, wherein fluid entering said inlet flows through said tube and thence through said nozzle and wherein said tube and said nozzle together constitute a kfiow regulating valve for excess fluid at higher rotational speeds of said rotor.

References Cited UNITED STATES PATENTS 2,327,637 8/ 1943 Harris 103-272 2,385,513 9/ 1945 Helvern et al. 103--5 2,399,249 4/ 1946 Perignat 10S-272 2,457,388 12/ 1948 Lung 103--5 2,861,585 ll/1958 Becker 103-42 2,865,297 12/ 1958 Cliborn et al. 103-42 2,938,465 5/ 1960 McFarland et al 103-42 3,125,028 3/1964 Rohde 103-42 3,250,227 5/ 1966 Kouns ID3-l 3,373,689 3/ 1968 Brunson 103-42 FOREIGN PATENTS 262,920 12/ 1926 Great Britain.

HARRY F. RADUAZO, Primary Examiner U.S. Cl. X.R. 103-5, 272