Compact eccentric-driven pump for a controlled braking system

Abstract

An eccentric-driven piston pump for a vehicle controlled braking system has a pump drive apparatus including a stub shaft having an eccentric journalled in a pump housing for self-supported rotation about a stub shaft axis by a first and a second rotating bearing disposed on opposite axial sides of the eccentric. The stub-shaft is operatively connected to the rotating drive shaft of a motor, and the eccentric is connected for imparting reciprocating motion to the pistons. A pair of thrust bearings including a counterweight for balancing the pump drive apparatus, are disposed on the stub shaft adjacent the eccentric at opposite axial ends thereof between the eccentric and first and second rotating bearings. The motor includes a spherical bearing for alignment of a motor drive shaft with the stub shaft, and a bushing for loosely supporting the drive shaft prior to attaching the drive shaft to the stub shaft.

Description

TECHNICAL FIELD OF THE INVENTION

[0001] This invention relates piston pumps, and more particularly to hydraulic piston pumps of the type used in controlled braking systems for vehicles.

BACKGROUND OF THE INVENTION

[0002] Modem vehicles, such as automobiles, trucks, buses, motorcycles, and motor homes are often equipped with sophisticated controlled braking systems that provide anti-lock braking (ABS), traction control (TCS), or stability control (SCS). During controlled braking events, an automated control unit takes control of the brake system and regulates the flow and pressure of hydraulic brake fluid to the brakes in a manner that would not be achievable through manual control by the driver.

[0003] Such controlled braking systems typically include a hydraulic pump driven by an electric motor that is activated during controlled braking events, to provide a continuous flow of pressurized brake fluid for use by control valves connected to the brakes, in accordance with control signals received from the automated control unit. The pump in a controlled braking system generally includes one or more positive displacement, reciprocating piston assemblies, driven by an eccentric on a pump drive shaft that is in turn driven by an electric motor.

[0004] In a typical prior controlled braking pump 10, as shown in FIG. 1, the pump drive shaft 12 extends from the rotor 14 of an electric motor 16. The drive shaft 12 is supported within the motor 16 on a pair of bearings 13, 15. The electric motor 16 is adapted for attachment to a pump housing 18.

[0005] The pump drive shaft 12 is a single piece, machined and ground in multiple operations to define a stepped distal end 17 thereof, for engaging a third bearing 19 mounted in the pump housing 18. The drive shaft 12 includes an eccentric 20 for receipt of a needle bearing 22 adapted to bear against and drive one or more piston assemblies 24. Two thrust washers 26 are pressed onto the eccentric 20 on either side of the needle bearing 22, for retaining the needle bearing on the eccentric 20.

[0006] In order to compensate for the material removed from the drive shaft 12 in forming the eccentric, and to balance the rotating assembly formed by the drive shaft 12 and the motor rotor 14, extra partial laminations, or a brass counterweight 28 are attached to one end the rotor 14 at a position diametrically opposite from the direction that the eccentric 20 is offset from the centerline 30 of the pump drive shaft 12.

[0007] While a controlled braking pump 10 constructed as described above functions well, there are several areas in which it would be desirable to make improvements for facilitating manufacturing, reducing cost, and allowing a single same motor and drive shaft assembly to be used for a family of pumps having different displacement requirements.

[0008] Changing the distance ‘d’ that the eccentric 20 is offset from the centerline 30 of the drive shaft 12, to generate a shorter or longer stroke of the piston assemblies 24 in controlled braking pumps 10 of different displacements, requires significant changes in machining set-ups and tooling. Changing the offset distance ‘d’ also changes the size of the counterweight 28 required for balancing the rotating assembly, thereby necessitating the fabrication and stocking of motors 16 having a different shaft 12, rotor 14 and counterweight 28 for each desired displacement necessary for supporting alternate vehicle applications.

[0009] Having the drive shaft 12 supported by three bearings 13, 15, 19, two of which are part of the motor 16 and one mounted in the housing 18, makes assembly difficult, and sets up a condition where the three bearings 13, 15, 19 may fight each other, if they are not precisely aligned with one another, and impose undesirable side loads on the drive shaft 12. It is also generally necessary for the bearing 15 in the motor 16 to be a different physical size than the bearing 19 at the end of the drive shaft 12, in order to provide sufficient support for the drive shaft 12 to resist operational side loads inherent in having the eccentric 20 drive the pistons 24.

[0010] Advances in the design of the piston assemblies 24, as disclosed in our co-pending patent application bearing the docket number DP-307647, allow the displacement of the pump 10 to be increased for meeting the demands for larger flows of brake fluid required in modern controlled braking systems. Producing a larger flow of braking fluid in a pump 10 of the type described above requires increasing the piston bore diameter and/or stroke. Increasing the bore diameter and/or stroke of the piston assemblies 24 increases the side load imposed on the eccentric 20 of the drive shaft 16, and may result in side loads increasing to levels that are very difficult to accommodate with the three bearing approach, as described above, used in prior controlled braking pumps 10.

[0011] What is needed, therefore, is an improved, eccentric driven, controlled braking pump that provides a solution to one or more of the problems described above.

SUMMARY OF THE INVENTION

[0012] Our invention provides an improved pump, suitable for use in vehicle controlled braking systems, through utilization of a pump drive apparatus including a stub shaft having an eccentric between a driven end and an end of the stub shaft opposite the driven end. The stub shaft is journalled in a pump housing for self-supported rotation about a stub shaft axis by a first and a second rotating bearing disposed on opposite axial sides of the eccentric. The driven end of the stub-shaft is adapted for operative connection to a rotating drive shaft to be rotated thereby, and the eccentric is adapted for operative connection to one or more pistons for imparting reciprocating motion to the pistons.

[0013] The pump drive apparatus may include a pair of thrust bearings disposed on the stub shaft adjacent the eccentric at opposite axial ends thereof between the eccentric and first and second rotating bearings. One or both of the thrust bearings may including a counterweight for balancing the pump drive apparatus.

[0014] The pump drive apparatus may also include a motor having a motor housing for attachment of the motor to the pump housing, a rotating drive shaft having an anti-drive end within the motor housing and a drive end connected to the driven end of the stub shaft. A rotating drive shaft bearing, attached to the motor housing, and having a spherical outer surface thereof operatively connected to the motor housing for allowing the rotating shaft to nutate about the axis of the rotating drive shaft, may be used for journaling the anti-drive end of the rotating drive shaft. The pump drive apparatus may further include a bushing attached to the motor housing adjacent the drive end of the rotating drive shaft, for loosely journaling the drive end of the drive shaft during assembly and test operations performed on the motor prior to attaching the drive end of the motor drive shaft to the drive end of the stub shaft.

[0015] The foregoing and other features and advantages of our invention are apparent from the following detailed description of exemplary embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 is cross-section of prior art eccentric-driven piston pump, for a controlled braking system;

[0017] FIG. 2 is a cross section of a first exemplary embodiment of an eccentric-driven piston pump, according to our invention, for a controlled braking system,;

[0018] FIG. 3 is an enlarged cross section of the pump drive apparatus of the pump of FIG. 2; and

[0019] FIGS. 4-7 are enlarged cross sections of exemplary embodiments of several alternate drive mechanisms, according to of our invention.

DETAILED DESCRIPTION

[0020] FIG. 2 shows a first exemplary embodiment of a pump 100, according to our invention. The pump 100 includes a first and a second pump module 112, 114, a pump housing 116, and a pump drive apparatus 118.

[0021] The first and second pump modules 112, 114 are retained in respective cavities 123, 124 in the housing 16 by staking a portion of the housing 116 against the outer of the first and second pump modules 112, 114, as indicated by arrows 125 in FIG. 2.

[0022] As shown in FIGS. 2 and 3, the pump drive apparatus 118 includes a stub shaft 138 and an electric motor 140. The stub shaft 138 is journalled in a cavity 136 of the pump housing 16, connecting the cavities 123, 124 in the housing 116 for receiving the first and second pump modules 112, 114. The stub shaft 138 includes a rotating eccentric 142 and a driven end 144 of the stub shaft 138 adapted for operative connection to a rotating drive shaft 146 extending from the motor 140. The pump drive apparatus 118, of FIGS. 2 and 3, further includes a needle bearing 148 disposed between the rotating eccentric 142 and the exposed ends 102 of the pistons 104 of the first and second modules 112, 114. A pair of thrust bearings 150 are disposed on the stub shaft 138 and abutting the needle bearing 148 at opposite axial ends of the needle bearing 148. A pair of rotating bearings 152 are disposed between the stub shaft 138 and the pump housing 16, abutting the thrust bearings 150 on opposite sides of the rotating eccentric 142 for supporting the pump drive apparatus 18 in the housing 16.

[0023] The drive apparatus 18 in the embodiment shown in FIGS. 2 and 3 includes a retainer element in the form of a retaining ring 154 abutting the top surface of the top rotating bearing 152 and connected to the housing 116 through staking, or alternatively by being inserted into a groove in the housing 116, for limiting axial movement of the stub shaft 138 in the housing 116. A thrust washer, in the form of a wavy spring washer 156, is disposed between the housing 116 and the rotating bearing 152 at the end 158 of the stub shaft 138 opposite the drive end 144 for loading the pump drive apparatus 118 against the retaining ring 154.

[0024] There are many other ways in which the drive apparatus 118 can be retained axially against the force exerted by the wavy spring washer 156. For example, as shown in FIG. 5, a contoured retaining ring 155 is operatively connected to the housing 116 by clamping the contoured retaining ring 155 between the top surface of the top bearing 152 and a lower surface 165 of the motor housing 164.

[0025] The thrust bearings 150 are each configured to provide a counterweight 160 for balancing the pump drive apparatus 118, to counteract dynamic forces generated by the eccentric 142 and needle bearing 148 as the stub shaft 138 rotates about a rotational axis 162 of the drive apparatus 18. Configuring the thrust washers 150 to include the counterweights 160 provides a significant advantage over prior controlled braking pumps without the separately supported stub shaft 138.

[0026] The motors in prior pumps had to include extra laminations or brass weights on the motor rotor for balancing those prior pumps against the dynamic forces generated by the eccentric elements attached to the motor drive shaft. These counterweights inside the motors of prior pumps had to be specifically matched to one particular drive mechanism. If the offset of the eccentric was increased or decreased to change the stroke of the prior pumps, for instance, a different motor having appropriate counterweights was required. Eliminating the counterweights inside the motor 140 by having the drive mechanism 138 be self-supporting, according to our invention, allows a given motor 140 to be used in multiple pump embodiments that may have different drive mechanisms 118 for providing different displacements, thereby greatly facilitating construction of the pump 10 and reducing inventory requirements for the motors 140 required for providing a number of pump 100 configurations specifically configured to the requirements of the vehicle in which the pump 10 is to be installed.

[0027] Having the drive apparatus 118 be self supported within the housing 116 on the two rotating bearings 152 provides further advantages for simplifying the construction and reducing the cost of the motor 140. The addition of the upper bearing 152 in the drive apparatus 118 allows a similar bearing, required in the motors of prior controlled braking pumps at the point where the motor drive shaft emerges from the motor, to be eliminated from the motor 140 in the exemplary embodiments of our invention shown in FIGS. 2 through 5.

[0028] As shown in FIGS. 2 and 3, the motor 140 in the exemplary embodiments of our invention described thus far includes a motor housing 164 for attachment of the motor 140 to the pump housing 116. The rotating drive shaft 146 defines an axis of rotation 166, a drive end 168 adapted for operative connection to the driven end 144 of the stub shaft 138, and an anti-drive end 170 at the upper end of the motor 140 as depicted in. FIGS. 2 and 3.

[0029] A rotating drive shaft bearing 172 is attached to the motor housing 164 for journaling the anti-drive end 170 of the rotating drive shaft 146. The drive shaft bearing 172 has a spherical outer surface 174 thereof operatively connected to the motor housing 164 for allowing the rotating drive shaft 146 to nutate about the axis 166 of the rotating drive shaft 146. Having the drive shaft 146 supported at its anti-drive end 170 in the bearing 172 in this manner, facilitates alignment of the axis 166 of the drive shaft 166 of the motor 140 to the axis 162 of the stub shaft 138, to prevent binding and introduction of undesirable side loads or bending forces on the motor drive shaft 166 and stub shaft 138.

[0030] A bushing 176 of a low friction material, such as Nylon, plastic or an oil impregnated bronze, is attached to the motor housing 164 adjacent the drive end 168 of the rotating drive shaft 146, for loosely journaling the drive end 168 of the drive shaft 146 during assembly and test operations performed on the motor 140 prior to attaching the drive end 168 of the motor drive shaft 146 to the drive end 168 of the stub shaft 138. This bushing 164 is not necessarily used for supporting the motor drive shaft 146 during operation of the pump 100, and may thus be fabricated by inexpensive methods, such as molding, from a low cost material.

[0031] The drive end 168 of the rotating drive shaft 146 of the motor 140 is connected to the driven end 144 of the stub shaft 138 by a compliant drive coupling 178, for accommodating misalignment of the axes 166, 162 of the drive shaft 146 and stub shaft 138. In the embodiments shown in FIGS. 2 and 3, the drive end 168 of the motor drive shaft 146 includes a cylindrical pilot segment 180, of reduced diameter, that engages a close fitting cylindrical pilot bore 182 in the driven end 144 of the stub shaft 138. The clearances and fits between the motor shaft 146 and bushing 176 are constructed in accordance with the clearances and fits between the motor shaft pilot segment 180 and stub shaft pilot bore 182, so that the lowest cost, smoothest operating pump drive assembly is achieved.

[0032] Extending from the end of the pilot 180 of the motor drive shaft 146 is a hex-shaped drive element 184 that drivingly engages a corresponding hex-shaped socket 186 extending from the bottom end of the pilot bore 182 into the stub shaft 138. Other types of drivers and sockets such as square, D-shaped, torx, etc. may also be employed in this concept.

[0033] While the description of our invention above has utilized certain exemplary embodiments for the purpose of explanation, our invention may also be practiced in a number of other embodiments. Furthermore, various changes and modifications can be made from the disclosed embodiments without departing from the spirit and scope of the invention.

[0034] For example, in the embodiments shown in FIGS. 2 through 7, the first and second pump modules 112, 114 include a return spring 106 and retaining ring 108 for holding the exposed ends 102 of the pistons 104 against the outer race the needle bearing 148. In other embodiments of our invention, the return springs 106 and retaining rings 108 may be eliminated from the pump modules 112, 114, and the exposed ends 102 of the pistons 104 connected to the eccentric 142 on the stub shaft 138 with a retainer clip, in the same manner as indicated at 110 in FIG. 1.

[0035] Our invention may also utilize a different type of compliant coupling 178 for joining the drive end 168 of the motor drive shaft 146 to the driven end 144 of the stub shaft 138. For example, as shown in FIG. 4 the compliant coupling 178 may include a separate quill shaft 210 having a cylindrical pilot central section 212 and a hex-drive element 184 at each end of the quill shaft 210. The motor drive shaft 146 includes a cylindrical pilot bore 214, that engages in a close fit the cylindrical pilot section 212 of the quill shaft 210 in the drive end 168 of the motor drive shaft 146. Extending from the end of the cylindrical pilot bore 214 into the motor drive shaft 146 is a hex-shaped drive socket 216 that drivingly engages the corresponding hex-shaped element 184 extending from the upper end of the quill shaft 210. The compliant coupling 178 may further include a small compression spring 218 disposed in a spring pocket 220 extending into the motor drive shaft 146 from the upper end of the hex-shaped socket 214, for keeping the quill shaft 210 from vibrating axially, thereby reducing noise in the drive mechanism 18 and preventing brinelling wear of the quill shaft 210 and the bores 182, 184, 214, 216 engaging the quill shaft 210.

[0036] Our invention may also be practiced with motors 16 of the type shown in FIG. 1 having a bearing 15 attached to the motor housing at the drive end of the drive shaft, as shown in FIGS. 6 and 7, in accordance with various aspects and elements of the exemplary embodiments described above.

[0037] The scope of the invention is indicated in the appended claims. We intend that all changes or modifications within the meaning and range of equivalents are embraced by the claims.

Claims

1. A pump apparatus for a controlled braking system in a vehicle, the pump comprising:

a pump housing for receiving at least one pump module having a reciprocating piston with an exposed end thereof extending from the module; and

a pump drive apparatus attached to the pump housing and including a stub shaft having an eccentric between a driven end and an end of the stub shaft opposite the driven end, the stub shaft journalled within the housing for self-supported rotation about a stub shaft axis by a first and a second rotating bearing disposed on opposite axial sides of the eccentric, the driven end of the stub-shaft adapted for operative connection to a rotating drive shaft to be rotated thereby, and the eccentric adapted for operative connection to the exposed end of the piston for imparting reciprocating motion to the piston within the pump module.

2. The pump apparatus of claim 1 wherein the pump drive apparatus further includes:

a needle bearing mounted on the eccentric and having an outer race adapted for contacting the exposed end of the piston;

a pair of thrust bearings disposed on the stub shaft and abutting the needle bearing at opposite axial ends thereof between the first and second rotating bearings; and

a thrust washer disposed between the housing and the rotating bearing at the end of the stub shaft opposite the drive end for urging the pump drive apparatus along the stub-shaft axis in a direction away from the thrust washer.

3. The pump apparatus of claim 2 wherein the drive apparatus further includes a retainer element abutting one of the rotating bearings adjacent the driven end of the stub shaft and operatively connected to the housing for limiting axial movement of the stub shaft in the housing.

4. The pump apparatus of claim 2 wherein at least one of the thrust bearings includes a counterweight for balancing the pump drive apparatus.

5. The pump apparatus of claim 4 wherein the pump drive apparatus includes a motor having a rotating drive shaft extending therefrom operatively connected to the drive end of the stub shaft.

6. The pump apparatus of claim 5 wherein the motor includes a drive apparatus retainer element abutting one of the rotating bearings adjacent the driven end of the stub shaft for limiting axial movement of the stub shaft in the housing.

7. The pump apparatus of claim 5 wherein the motor does not include a counterweight for balancing the pump drive apparatus.

8. The pump apparatus of claim 5 wherein the rotating drive shaft defines an axis of rotation, a drive end adapted for operative connection to the stub shaft, and an anti-drive end, and the motor further comprises:

a motor housing for attachment of the motor to the pump housing;

a rotating drive shaft bearing attached to the motor housing for journaling the anti-drive end of the rotating drive shaft, and having a spherical outer surface thereof operatively connected to the motor housing for allowing the rotating shaft to nutate about the axis of the rotating drive shaft; and

a bushing attached to the motor housing adjacent the drive end of the rotating drive shaft and loosely journaling the drive end of the drive shaft during assembly and test operations performed on the motor prior to attaching the drive end of the motor drive shaft to the drive end of the stub shaft.

9. The pump apparatus of claim 8 further including a compliant drive coupling connecting the drive end of the motor rotating drive shaft to the driven end of the stub shaft, for accommodating misalignment between the drive and stub shafts.

10. The pump apparatus of claim 9 wherein:

the drive end of the motor rotating drive shaft includes a reduced diameter cylindrical pilot extending thereform along the drive shaft axis, and a hex drive segment extending along the drive shaft axis from the cylindrical pilot; and

the driven end of the stub shaft includes a cylindrical pilot bore extending into the stub shaft along the axis of the stub shaft, and a hex socket extending into the stub shaft along the axis of the stub shaft from the pilot bore, the pilot bore and hex socket receiving the cylindrical pilot and hex drive segment of the rotating drive shaft of the motor.

11. The pump apparatus of claim 10 wherein the cylindrical pilot and pilot bore are sized for providing a tight circumferential fit between one another.

12. The pump apparatus of claim 9 wherein:

the drive and stub shafts each define a diameter at the drive and driven ends respectively thereof:

the compliant coupling includes a quill shaft having a cylindrical central pilot segment with a diameter less that the respective diameters of the drive and driven ends of the drive and stub shafts, the quill shaft also having a hex drive segment extending from either end of the cylindrical central pilot segment;

the drive end of the motor drive shaft includes a cylindrical pilot bore extending into the drive shaft along the axis of the drive shaft, and a hex socket extending into the drive shaft along the axis of the drive shaft from the pilot bore;

the driven end of the stub shaft includes a cylindrical pilot bore extending into the stub shaft along the axis of the stub shaft, and a hex socket extending into the stub shaft along the axis of the stub shaft from the pilot bore; and

the pilot bores and hex sockets in the drive and stub shafts are adapted for receiving the cylindrical pilot and hex drive segments of the quill shaft.

13. The pump apparatus of claim 12 wherein:

the drive end of the drive shaft further includes a spring pocket extending into the drive shaft along the axis of the drive shaft; and

the compliant coupling further includes a compression spring disposed in the spring pocket between the quill shaft and the spring pocket for urging the quill shaft to move along the drive shaft axis toward the stub shaft.

14. The pump apparatus of claim 9 further including at least one pump module defining a cylinder bore and a reciprocating axis extending through the cylinder bore from a first to a second axial end of the module, and having a piston in the cylinder bore for sliding motion along the reciprocating axis, the piston having an exposed end thereof extending from the second end of the module and connected to a drive mechanism.

15. The pump apparatus of claim 14 wherein the drive apparatus includes a return clip for attaching the exposed end of the piston to the eccentric.

16. The pump apparatus of claim 14 wherein the pump module includes a return spring for urging the exposed end of the piston into contact with outer race of the needle bearing.

17. A pump drive apparatus for a installation in a pump housing and imparting reciprocating motion to a piston operatively installed in the housing, the pump drive apparatus comprising:

a stub shaft having an eccentric between a driven end and an end of the stub shaft opposite the driven end, the stub shaft journalled for self-supported rotation about a stub shaft axis by a first and a second rotating bearing disposed on opposite axial sides of the eccentric, the driven end of the stub-shaft adapted for operative connection to a rotating drive shaft to be rotated thereby, and the eccentric adapted for operative connection to the piston for imparting reciprocating motion to the piston; and

a motor including a motor housing for attachment of the motor to the pump housing, a rotating drive shaft having an anti-drive end within the motor housing and a drive end connected to the driven end of the stub shaft, a rotating drive shaft bearing attached to the motor housing for journaling the anti-drive end of the rotating drive shaft and having a spherical outer surface thereof operatively connected to the motor housing for allowing the rotating shaft to nutate about the axis of the rotating drive shaft.

18. The pump drive apparatus of claim 17 further comprising a bushing attached to the motor housing adjacent the drive end of the rotating drive shaft and loosely journaling the drive end of the drive shaft during assembly and test operations performed on the motor prior to attaching the drive end of the motor drive shaft to the drive end of the stub shaft.

19. A pump drive apparatus for installation into a pump housing and imparting reciprocating motion to a piston operatively installed in the housing, the pump drive apparatus comprising:

a stub shaft having an eccentric between a driven end and an end of the stub shaft opposite the driven end, the stub shaft journalled for self-supported rotation about a stub shaft axis by a first and a second rotating bearing disposed on opposite axial sides of the eccentric, the driven end of the stub-shaft adapted for operative connection to a rotating drive shaft to be rotated thereby, and the eccentric adapted for operative connection to the piston for imparting reciprocating motion to the piston; and

a pair of thrust bearings disposed on the stub shaft adjacent the eccentric at opposite axial ends thereof between the eccentric and first and second rotating bearings;

at least one of the thrust bearings including a counterweight for balancing the pump drive apparatus.

20. The pump drive apparatus of claim 19 further comprising a motor having a rotating drive shaft attached to the driven end of the stub shaft, the motor not including any counterweights for balancing any part of the pump drive apparatus other than the motor itself.