Multi-piston pump and valve arrangement

Abstract

A multi-piston pump includes a housing defining a first plurality of N bores therein, where N is the number of bores in the first plurality. The first plurality of N bores is offset from one another. The housing defines a second plurality of N bores therein. The second plurality of N bores is offset from one another. Each bore of the second plurality of N bores is offset from a corresponding bore of the first plurality of N bores. A substantially straight cylindrical piston is disposed in each of said bores for reciprocal movement along a longitudinal axis therein. The pistons in the first plurality of N bores are operable to induce fluid flow in hydraulic fluid. The pistons in the second plurality

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates in general to hydraulic pumps.

2. Description of Related Art

A hydraulic brake system is one type of generally known brake system for vehicles. A vehicle hydraulic brake system typically has a master cylinder, a number of wheel brake cylinders, and a hydraulic pump with which brake fluid can be delivered from the master cylinder to the wheel brake cylinders. For example, the hydraulic pump may be used for hydraulic brake boosting. The hydraulic pump may also be used, in conjunction with a series of valves in a hydraulic control unit (HCU) for antilock braking system (ABS), traction control (TC), and vehicle stability control (VSC) functions. One known method for carrying out these functions is to program an electronic control unit (ECU) to reduce pressure in the wheel brake cylinders by way of controlling (solenoid) valves in the HCU. In one known system the intake side of the hydraulic pump is connected to the wheel brake cylinders and the pressure side of the hydraulic pump is connected to the master cylinder. A vehicle hydraulic brake system of this kind has been disclosed by DE 195 01 760 A1.

It is generally known to use a dual piston pump for the hydraulic pump in such a system. The dual piston pump typically includes pistons disposed opposite each other in a boxer arrangement, which are driven by a common cam disposed between the two pistons. The two pistons operate in anti-phase, i.e. while one of the two pistons is executing a delivery stroke, the other piston is executing a return stroke. The delivery stroke is the stroke in which the piston decreases the volume of a displacement chamber in a cylinder of the piston pump and thus displaces fluid from the piston pump. In the return stroke, the volume of the displacement chamber is increased again; this stroke is also often called the intake stroke. Due to their oscillating operation, piston pumps have an oscillating intake volume flow and cause pressure pulsations on the intake side, which have repercussions on the master cylinder and produce an unpleasant sensation in a foot brake pedal and generate clearly audible noise. Both of these are undesirable, particularly if the hydraulic pump is used for hydraulic brake boosting, i.e. is operated with each braking maneuver. These are also undesirable during antilock braking, traction control, and vehicle stability control. Therefore, it is desirable to reduce the pressure pulsations. It is also known to embody the pistons of the piston pump as stepped pistons which have the advantage of aspirating brake fluid during both the delivery stroke and the return stroke. A stepped piston has the advantage over a simple piston of a more uniform intake volume flow with a reduced amplitude and a doubled frequency. U.S. Pat. No. 6,446,435 describes a motor driven pump using an even number of stepped pistons to reduce amplitudes of pressure pulsations in the inlet of the pump.

In operation of the pump, it is desirable that the pump be reliable, relatively low cost to manufacture, operate with low noise and vibration, and minimize pressure pulsations in the brake system that are felt by the driver of the vehicle.

BRIEF SUMMARY OF THE INVENTION

This invention relates in general to hydraulic pumps and more specifically to a multi-piston hydraulic pump and a valve arrangement.

A first aspect of the present invention includes a multi-piston pump includes a housing defining a first plurality of N bores therein, where N is the number of bores in the first plurality. The bores of the first plurality of N bores are offset from one another. The housing defines a second plurality of N bores therein. The bores of the second plurality of N bores are offset from one another. Each bore of the second plurality of N bores is also offset from a corresponding bore of the first plurality of N bores. A substantially straight cylindrical piston is disposed in each of said bores for reciprocal movement along a longitudinal axis therein. The pistons in the first plurality of N bores are operable to induce fluid flow in a first hydraulic circuit. The pistons in the second plurality of N bores are operable to induce fluid flow in a second hydraulic circuit.

In another aspect of the present invention, a valve arrangement includes a main valve body having a plurality of bores formed therein. The valve arrangement is suitable to form a portion of a multi-piston pump and includes first and second pluralities of non-stepped pistons disposed in the bores. The valve arrangement is suitable for controlling fluid flow in a hydraulic circuit.

Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic circuit diagram of a vehicular brake system.

FIG. 2 is a schematic representation of a six-piston pump in accordance with the present invention suitable for use in the vehicular brake system shown in FIG. 1.

FIG. 3 is a cross-sectional view of a portion of the pump of FIG. 2 taken along line 3-3.

FIG. 4 is an enlarged view of a portion of FIG. 3.

FIG. 5 is a top view of the sleeve of FIGS. 3 and 5.

FIG. 6 is a cross-sectional view of the sleeve of FIG. 5 taken along line 6-6

FIG. 7 is an enlarged view of a portion of FIG. 6 as indicated at circle 7.

DETAILED DESCRIPTION OF THE INVENTION

A vehicular brake system is indicated generally at 10 in FIG. 1. The system 10 includes valves and other components described below suitable to provide anti-lock braking (ABS), traction control (TC), and vehicle stability control (VSC) functions.

In the system 10, a brake pedal 12 is connected to a master cylinder 14 to provide pressurized brake fluid to wheel brakes 16. The master cylinder 14 is in fluid communication with a master cylinder brake fluid reservoir 15. The reservoir 15 is a source of bake fluid for the master cylinder 14.

A hydraulic control unit (HCU) 18 includes a housing having bores for receiving control valves and other components described below. Fluid passageways or conduits are provided between the bores to provide fluid communication between the valves and other components.

The HCU 18 includes normally open control valves 20, commonly referred to as apply valves, disposed between the master cylinder 14 and the wheel brakes 16. Each apply valve 20 is preferably formed as a solenoid valve switchable between two positions. The apply valve 20 includes a coil subassembly that creates an electromagnetic flux to slide an internal armature between the two positions.

The HCU 18 also includes normally closed control valves 22, commonly known as dump valves, disposed between the wheel brakes 16 and the master cylinder brake fluid reservoir 15. Each dump valve 22 is preferably formed as a solenoid valve switchable between two positions. The dump valve 22 includes a coil subassembly that creates an electromagnetic flux to slide an internal armature between the two positions.

An isolation valve 28 is provided in each circuit. The isolation valves 28 are in fluid communication with the master cylinder brake fluid reservoir 15 and the apply valves 20. The valves 28 each include a coil subassembly that creates an electromagnetic flux to slide an internal armature between two positions.

A supply valve 30 is provided in each circuit. The supply valves 30 are in fluid communication with the master cylinder 14 and the control valves 22. The valves 30 each include a coil subassembly that creates an electromagnetic flux to slide an internal armature between two positions.

The system 10 of FIG. 1 is illustrated as a diagonally split system, wherein the right front wheel RF and the left rear wheel LR are included in a first circuit I, and the left front wheel LF and the right rear wheel RR are included in a second circuit II. Other configurations of the braking system 10 can be provided.

The valves 20, 22, 28, and 30 are electrically connected to an electronic control unit 27 and operated to provide desired ABS, TC, and VSC functions in a well known manner.

The brake system 10 includes a pump 166 that supplies pressurized fluid to the brake system 10 during, for example, ABS, TC, and VSC functions. The pump 166 is driven by a motor 48 in a well known manner. Preferably, the motor 48 is an electric motor, for example a flux switching motor. It must be understood, however that the motor 48 may be any suitable motor.

Referring to FIG. 2, the pump 166 is illustrated as a six-piston pump and is suitable for use in the vehicular brake system 10. It must be understood, however, that the pump 166 may be a pump with any suitable number of pistons. For example, the multi-piston pump 166 may be a pump with any suitable even number of pistons, as will be described below.

The multi-piston pump 166 includes a main pump housing 130. The main pump housing 130 is preferably made of a metal, such as aluminum or any other suitable metal. However, it must be understood that the main pump housing 130 may be made of any suitable material. The main pump housing 130 includes a plurality of bores 132 formed generally in a star shape, meaning that the bores 132 radiate in a plane from a single point. The main pump housing 130 is illustrated as including six bores 132. It must be understood, however, that similar to the number of pistons in the multi-piston pump 166, the main pump housing 130 may include any suitable number of bores. For example, the main pump housing 130 may include any suitable even number of bores, as will be described below.

The bores 132 are disposed about and extend perpendicularly from a central bore 133. A cam element 70 that can be driven to rotate by the pump motor 48 is disposed in the central bore 133. As illustrated in FIG. 2, the bores 132 are formed in the main pump housing 130 around the central bore 133 each at a respective angle of 0 degrees, 30 degrees, 120 degrees, 150 degrees, 240 degrees, and 270 degrees. It must be understood, however, that the bores may be formed at any suitable angle, as will be described below.

The bores 132 are preferably each formed with a plurality of stepped sections that have successively more reduced diameters toward the interior (i.e., center) of the housing 130 (or near to the motor 48 and the cam 70), i.e., the sections of the bore 132 closest to the central bore 133 have a smaller diameter than the adjacent segment further away form the central bore 133. It must be understood, however, that the bores need not necessarily include stepped section and, indeed, may have any suitable form.

The main pump housing 130 includes a plurality of inlet ports 134 and outlet ports 136 formed therein. Each bore 132 is in fluid communication with a respective inlet port 134 and a respective outlet port 136. As shown, the inlet ports 134 of the bores 132 at 0 degrees, 120 degrees, and 240 degrees are connected to the first circuits I. As also shown, the outlet ports 136 of the bores 132 at 0 degrees, 120 degrees, and 240 degrees are connected to the first circuits I. Similarly, the inlet ports 134 and the outlet ports 136 of the bores 132 at 30 degrees, 150 degrees, and 270 degrees are connected to the second circuit II. Thus, the bores 132 alternately form portions of the first and second circuits I and II.

As best shown in FIG. 3, the multi-piston pump 166 further includes a plurality of piston/cylinder arrangements 140, one piston/cylinder arrangement 140 disposed in each of the bores 132. The piston/cylinder arrangements 140 thereby have an alternating phase shift of 30 degrees and 90 degrees.

As illustrated in FIG. 3, the piston/cylinder arrangement 140 includes a generally cylindrical sleeve 142, a clinched gland, i.e., plug, 144, and a non-stepped piston 168. However, it must be understood that the piston/cylinder arrangement 140 may be any suitable piston/cylinder arrangement.

The sleeve 142 is a substantially straight cylindrical sleeve that sealingly engages the bore 132. The sleeve 142 is essentially a cylinder with a pair of seals that separate portions of the bore 132 as to isolate the inlet and outlet ports 134 and 136 from each other. The sleeve 142 is a simplified sleeved design as compared to the sleeves of previous multi-piston pumps. The simplified design provides for reduced costs in manufacturing. The simplified sleeve design of the sleeve 142 allows for a reduced piston size while permitting 30 degree spacing between the sleeves 142, and while maintaining desired packaging size of the housing 130. It must be understood, however, that the sleeve 142 may be ay suitable sleeve.

Each cylindrical sleeve 142 is disposed in a respective bore 132 and sealed in position by a respective clinched gland 144. The use of the clinched gland 144 reduces production costs as compared to other means for securing the sleeve 142 in the bore 132. Further, as compared to other types of securing means the clinched gland 144 secures the sleeve 142 in the bore 132 without distorting the bore 132. It must be understood, however, that sealing/securing mechanism may be used, such as a threaded arrangement, weld, or any other suitable mechanism.

Each non-stepped piston 168 is disposed in a respective generally cylindrical sleeve 142. The piston 168 is a non-stepped piston, i.e., a substantially straight cylindrical piston, for reciprocal movement along a longitudinal axis. The piston 168 is operable to induce fluid flow in a hydraulic circuit. While the piston 168 may be any suitable size, the piston 168 is most preferably a piston sized between 5 and 6 millimeters.

The multi-piston pump 166 includes an inlet check valve arrangement 150 and an outlet check valve arrangement 152 associated with a respective piston/cylinder arrangement 140. As shown in FIG. 3, the inlet check valve arrangement 150 is preferably included within the non-stepped piston 168 and is suitable to control fluid flow in one of the first hydraulic circuit and the second hydraulic circuit. It must be understood, however, that the multi-piston pump 166 may include any suitable inlet control valve, in any suitable configuration.

The outlet check valve 152 is formed between the sleeve 142 and the clinched gland 144. The outlet check valve 152 includes a valve ball 154 and a deep ball seat 156 formed in the sleeve 142. Due to the deep ball seat 156 the valve ball 154 will travel significantly when transitioning from a closed position of the seat 156 to an open position above the seat 156. The outlet check valve 152 is thus a high lift outlet check valve. The high lift aspects of the outlet check valve 152 minimizes noise as compared to previous pumps when the pump is run at reduced speed/low output flow.

The use of the inlet check valve 150 and the outlet check valve 152 minimizes the unswept pump chamber volume as compared to previous designs and allows for the use of the non-stepped piston 168 in the piston/cylinder arrangement 140.

The multi-piston pump 166 includes six non-stepped pistons 168 alternating in two sets of three, one set of pistons 168 offset from the other set of pistons 168 by 30 degrees.

As shown in FIG. 2, the six non-stepped pistons 168 are disposed in the bores 132 around the cam element 70. The non-stepped pistons 168 are shown disposed at angles of 0 degrees, 30 degrees, 120 degrees, 150 degrees, 240 degrees, and 270 degrees. As illustrated, the non-stepped pistons 168 thereby have an alternating phase shift of 30 degrees and 90 degrees. A first set of three non-stepped pistons 168 offset from one another by 120 degrees are hydraulically connected to one another in parallel and are associated with the first brake circuit I. The remaining three non-stepped pistons 168, which are offset from one another by 120 degrees similar to the first set, form a second set of three non-stepped pistons 168 that is offset from the first set of three non-stepped pistons 168 by 30 degrees. Similar to the non-stepped pistons 168 of the first set and the first circuit, the non-stepped pistons 168 of the second set are likewise hydraulically connected to one another in parallel, and connected to the second brake circuit II. The three non-stepped pistons 168 of the first set are offset from one another by 120 degrees and are also offset from the three non-stepped pistons 168 of the second set by 30 degrees.

In principle, the phase shifting of the six non-stepped pistons 168 by 30 degrees and 90 degrees produces a compensation effect of the pressure pulsations on the intake sides of the non-stepped pistons 168. The total intake volume flow, i.e., the sum of all six intake volume flows, has a significantly reduced fluctuation amplitude in comparison to a six-piston pump with pistons, stepped or non-stepped, that are each uniformly offset from on another by 60 degrees. The use of the non-stepped pistons 168 and their alternating disposition offset from one another by 30 degrees and 90 degrees results in a uniform phase shifting of the intake volume flows by 30 degrees in relation to one another. Whereas, in the case of a uniformly distributed disposition of pistons, for example, six pistons offset by 60 degrees, the intake volume flows of opposing pistons 168 travel in anti-phase with each other without a phase shift; and in sum, result in intake volume flows with twice the amplitude of the six intake volume flows of the six-piston pump shown in FIG. 2.

While the multi-piston pump 166 has been described with six non-stepped pistons, it must be understood that the present invention contemplates a variety of multi-piston pumps including a variety of numbers of non-stepped pistons. For example, the present invention includes a multi-piston pump having a housing defining a first set of N bores therein, where N is the number of bores in the first set. The first set of N bores are offset from (i.e., not aligned with) one another. The housing also defines a second set of N bores therein. The bores in the second set of N bores are offset from one another. Each bore of the second set of N bores is offset from a corresponding bore of the first of N bores set. While some configurations are more preferred over others, one such configuration is described above, it must be understood that any configuration where the spacing between the bores is not 360/2N degrees in sufficiently offset. One multi-piston pump, with a preferred configuration includes a first set of N bores offset from one another by approximately 360/N degrees and a second set of N bores offset from one another by approximately 360/N degrees with each bore of the second set being offset from a corresponding bore of the first set by approximately 90/N degrees. In such a pump a preferred number N is three. It must be understood however that N may be any suitable number.

The principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.

Claims

1. A multi-piston pump comprising:

a housing defining a first plurality of N bores therein, where N is the number of bores in said first plurality, said first plurality of N bores being offset from one another, said housing defining a second plurality of N bores therein, said second plurality of N bores being offset from one another, each bore of said second plurality of N bores being offset from a corresponding bore of said first plurality of N bores; and

a non-stepped piston disposed in each of said bores for reciprocal movement along a longitudinal axis therein, said pistons in said first plurality of N bores being operable to induce fluid flow in a first hydraulic circuit, said pistons in said second plurality of N bores being operable to induce fluid flow in a second hydraulic circuit.

2. The multi-piston pump of claim 1 wherein said non-stepped piston includes a valve arrangement for controlling fluid flow in one of said first hydraulic circuit and said second hydraulic circuit.

3. The multi-piston pump of claim 2 wherein said valve arrangement includes a check valve.

4. The multi-piston pump of claim 2 wherein said non-stepped piston is between 5 mm and 6 mm.

5. The multi-piston pump of claim 1 further comprising a generally cylindrical sleeve disposed in each of said bores, said sleeve having a substantially straight cylindrical longitudinal cavity defined therein, wherein said non-stepped piston is a substantially straight cylindrical piston slidably disposed in said cavity.

6. The multi-piston pump of claim 5 further comprising a clinched gland sealingly securing said sleeve in said bore.

7. The multi-piston pump of claim 6 further comprising an outlet check valve formed between said sleeve and said clinched gland, where in said outlet check valve includes a valve ball and a deep ball seat formed in said sleeve.

8. The multi-piston pump of claim 1 wherein said first set of N bores are offset from one another by approximately 360/N degrees, said second set of N bores are offset from one another by approximately 360/N degrees, and each bore of said second set of N bores are offset from a corresponding bore of said first of N bores set by approximately 90/N degrees.

9. The multi-piston pump of claim 8 wherein N is three.

10. A valve arrangement for controlling fluid flow in a hydraulic circuit comprising;

a main valve body suitable to form a portion of a multi-piston pump, said main valve body having a plurality of bores formed therein; and

first and second pluralities of non-stepped pistons disposed in said bores.

11. The valve arrangement of claim 10 wherein a generally cylindrical sleeve is disposed in each of said bores within said main valve body, each of said sleeves forming valve seat.

12. The valve arrangement of claim 10 wherein said valve seat forms a portion of high lift outlet check valve.

13. A multi-piston pump comprising:

a housing defining a first set of N bores therein, where N is the number of bores in said first set, said first set of N bores being offset from one another, said housing defining a second set of N bores therein, said second set of N bores being offset from one another, each bore of said second set of N bores being offset from a corresponding bore of said first of N bores set; and

a non-stepped piston disposed in each of said bores for reciprocal movement along a longitudinal axis therein, said pistons in said first set of N bores being operable to induce fluid flow in a first hydraulic circuit, said pistons in said second set of N bores being operable to induce fluid flow in a second hydraulic circuit; and

a valve arrangement for controlling fluid flow in at least one of the first hydraulic circuit and the second hydraulic circuit, the valve arrangement including a main valve body suitable to form a portion of a multi-piston pump.

14. A multi-piston pump comprising:

a housing defining a first plurality of N bores therein, where N is the number of bores in said first plurality, said first plurality of N bores being offset from one another, said housing defining a second plurality of N bores therein, said second plurality of N bores being offset from one another, each bore of said second plurality of N bores being offset from a corresponding bore of said first plurality of N bores; and

a non-stepped piston disposed in each of said bores for reciprocal movement along a longitudinal axis therein, said pistons in said first plurality of N bores being operable to induce fluid flow of hydraulic fluid, said pistons in said second plurality of N bores being operable to induce fluid flow of hydraulic fluid.