DE19905790A1 - Piston pump for hydraulic motor vehicle brake systems has permanent magnet to hold piston in engagement on engagement on eccentric jacket - Google Patents

Abstract

The pump has a piston engaging with its end face on an eccentric. Piston (20) and/or eccentric (62) have a permanent magnet (66) to hold the piston in engagement on the eccentric circumference. The piston has a back pressure valve (42) to regulate a fluid flow through the piston pump (10). Valve and magnet are fitted into a hole (32) in the piston. The piston is magnetic.

Description

State of the art

The invention relates to a piston pump according to the preamble of claim 1.

Piston pumps of this type are known, for example, from DE 41 07 979 A1 or DE 40 27 794 A1. The known piston pumps have a piston on, which is axially displaceable in a cylinder bore in a pump housing is recorded. The cylinder bore can be directly in the pump housing to be appropriate. Another option is to drill a cylinder inserting bushing into the pump housing. To drive the Piston to a reciprocating reciprocating movement in the axial direction in a manner known per se for promoting fluid, it is rotating driven eccentric provided on one end of the piston is arranged and its axis of rotation at right angles to the piston and Cylinder bore runs.

Around the piston with an end face in contact with a circumference of the eccentric holding are two common ways. The first way is to Piston with a helical compression spring as piston return spring on a side of the piston facing away from the eccentric in the cylinder bore is to press against the circumference of the eccentric. The sees this possibility DE 41 07 979 A1 already mentioned. This type of piston return has the  Disadvantage that the eccentric works against the force of the piston return spring, which is why a correspondingly larger drive power is necessary. Further The disadvantage is that the piston return spring space in the cylinder bore needed, resulting in a dead or damaged space in a displacement space in the Cylinder bore is enlarged, which increases the efficiency of the piston pump worsened. In addition, there is the disadvantage that the piston pump Return spring required as an additional component that this additional component be inserted into the cylinder bore when assembling the piston pump must and thereby causes additional workload and that the Piston return spring can tire or break.

The second possibility of piston reset is in the already mentioned DE 40 27 994 A1 disclosed. This possibility sees an essentially C-shaped one Bow spring in front, which engages around the eccentric and with both ends Heads of two oppositely arranged in a boxer arrangement Piston attacks and holds them in contact with the circumference of the eccentric. The Bow spring has the disadvantage that it is enlarged to accommodate them Makes eccentric space necessary. Another disadvantage is that heads on the pistons or piston grooves are required to attack the bow spring, which the Increase manufacturing costs for the pistons. Furthermore has this Possibility of piston return to the piston return spring mentioned disadvantage that an additional component is required with the bow spring is, which increases the assembly effort of the piston pump and that Bow spring can break. Furthermore, she makes a boxer arrangement of the Pistons required, so at least two pistons are necessary, their Arrangement is not free.

Advantages of the invention

In the piston pump according to the invention with the features of claim 1 the piston is held in contact with the circumference of the eccentric by magnetic force. The piston pump according to the invention has the advantage that its  Piston reset requires no additional space. Another advantage is a simplified assembly. In addition, there is no spring for Piston reset is provided, which can break or tire, so that a Failure probability of the piston pump according to the invention is reduced and their lifespan is increased. Furthermore, the magnetic force causes the Piston to rest against the circumference of the eccentric, none Counterforce to the driving force exerted by the eccentric on the piston. For A return spring can also be provided to support the magnetic force his.

The subclaims have advantageous refinements and developments the subject of the invention specified in claim 1.

For example, to form the piston with a permanent magnet a permanent magnet, the one end of the piston facing the eccentric forms, be firmly connected to the piston (claim 2).

Another option is to place a permanent magnet in a hole in the piston to use. This configuration is particularly advantageous if that Hole serves a fluid inlet in or a fluid outlet from the piston pump and a check valve is inserted into the hole or at a mouth of the Hole a check valve is attached, which serves as an inlet or outlet valve Control of a fluid flow through the piston pump is used (claim 3). In In this case, the permanent magnet is already present in the piston Hole used, which reduces the manufacturing costs and a secure fit causes the permanent magnet in the piston, especially when the hole is on the eccentric side is a closed blind hole (claim 4).

Another possibility is to design the piston magnetically, that is Magnetize pistons or manufacture them as permanent magnets 5).  

To increase the magnetic force between the piston and the eccentric according to claim 5, a concavely curved end face is provided with which the Piston abuts the circumference of the eccentric.

The piston pump according to the invention is in particular as a pump in a brake System provided a vehicle and is used in controlling the pressure in wheel brake cylinders used. Depending on the type of brake system for such Brake systems have the abbreviations ABS or ASR or FDR or EHB ver turns. In the brake system, the pump is used, for example, for the return flow of brake fluid from a wheel brake cylinder or from several Wheel brake cylinders in a master brake cylinder (ABS) and / or for conveying of brake fluid from a reservoir into a wheel brake cylinder or in several wheel brake cylinders (ASR or FDR or EHB). The pump will for example in a brake system with wheel slip control (ABS or ASR) and / or with a braking system (FDR) serving as a steering aid and / or required for an electro-hydraulic brake system (EMS). With the Wheel slip control (ABS or ASR) can, for example, block the Wheels of the vehicle during braking when the pressure is high Brake pedal (ABS) and / or a spinning of the driven wheels of the Vehicle with strong pressure on the accelerator pedal (ASR) can be prevented. At a brake system serving as a steering aid (FDR) becomes independent of one Actuation of the brake pedal or accelerator pedal a brake pressure in or in several wheel brake cylinders built, for example, to break out of the Prevent vehicle from the lane desired by the driver. The pump can also be used with an electro-hydraulic brake system (EMS), in which the pump the brake fluid in the wheel brake cylinder or in the Wheel brake cylinder promotes when an electric brake pedal sensor Actuation of the brake pedal detected or at which the pump to fill a Memory of the brake system is used.

drawing

The invention is based on a preferred and in the Drawing illustrated embodiment explained in more detail. Show it:

FIG. 1 is an axial section of a piston pump according to the invention;

FIG. 2 shows a detail of a modified embodiment of the invention according to arrow II in FIG. 1; and

Fig. 3 shows a detail view of a further modified embodiment according to the arrow III in FIG. 1.

Description of the embodiment

The piston pump according to the invention shown in FIG. 1, generally designated 10 , has a liner 12 which is inserted into a stepped cylinder bore 14 of a hydraulic block, which forms a pump housing 16 . The liner 12 has a liner bottom 18 which is integral with it. The hydraulic block, of which only a fragment surrounding the piston pump 10 is shown in the drawing for clarity of illustration, is part of a slip-controlled hydraulic vehicle brake system, which is otherwise not shown. In addition to the piston pump 10, further hydraulic components, not shown, such as solenoid valves and hydraulic accumulators are used in it and hydraulically interconnected. The hydraulic block is connected to a master brake cylinder, not shown, and edge brake cylinders, not shown, are connected to the hydraulic block.

A cylindrical piston 20 is axially displaceably received in the liner 12 . An end of the piston 20 facing the bushing base 18 is guided axially displaceably with a guide ring 22 on the inner surface of the bushing 12 and sealed with a sealing ring 24 . A protruding from the bush 12 the end of the piston 20 is guided axially by a guide ring 26 which is inserted in the stepped cylinder bore 14 slidably in the pump housing 16 and sealed with a sealing ring 28 which is inserted snugly into the cylinder bore 14 on the guide ring 26 . An end edge 30 of the liner 12 holds the guide ring 26 and the sealing ring 28 in the cylinder bore 14 . A diameter of the piston 20 corresponds to an inner diameter of the liner 12 , with a clearance fit between the piston 20 and the liner 12 , ie the piston 20 has an undersize with respect to the liner 12 , which ensures the axial displacement of the piston 20 .

For the fluid inlet, the piston 20 is provided with an axial blind hole 32 which opens at an end face of the piston 20 facing the liner bottom 18 and which is crossed by transverse bores 34 . The blind hole 32 and the transverse bores 34 communicate through a wide groove 36 in the circumference of the piston 20 and through liner windows 38 with an inlet bore 40 made in the pump housing 16, which opens radially to the piston pump 12 into the cylinder bore 14 .

As the inlet valve 42 , the piston pump 10 according to the invention has a spring-loaded check valve, which is attached to the end face of the piston 20 facing the liner bottom 18 : An opening of the blind hole 32 is designed as a conical valve seat 44 , against which a valve ball 46 as a valve closing body is provided by a helical compression spring Valve closing spring 48 is pressed. The valve ball 46 and the valve closing spring 48 are received in a valve cage 50 , against the bottom of which the valve closing spring 48 is supported. The valve cage 50 is made of sheet metal as a deep-drawn part and is provided with fluid passages 52 . On its open side, the valve cage 50 has a circumferential ring step 54 , with which it rests on the end face of the piston 20 facing the liner bottom 18 . For attachment to the piston 20 , the valve cage 50 has inwardly bent claws 56 which engage in a groove in the piston 20 .

The guide ring located in the bush 12 22 and sealing ring 24 are in the axial direction between an attached to the piston 20 perforated disc 58, which is held by the valve cage 50 on the piston 20, and an annular step 60 of the piston fixed on the piston 20 twentieth The distance between the perforated disk 58 and the ring step 60 is such that the guide ring 22 and the sealing ring 24 are not compressed.

To drive the piston 20 to a reciprocating reciprocating movement in the axial direction, the piston pump 10 according to the invention has an eccentric 62 which can be driven by an electric motor, on the circumference of which the piston 20 rests with its end face facing away from the bushing base 18 on its end face projecting from the bushing 12 . In order to keep the piston 20 with its end face 64 in contact with the circumference of the eccentric 62 , the piston 20 has a permanent magnet 66 which is pressed into the blind hole 32 of the piston 20 to the bottom thereof. With regard to the transverse bores 34 , the permanent magnet 66 is located on a side of the blind hole 32 facing away from the inlet valve 42 , so that the permanent magnet 66 does not hinder the fluid inlet through the transverse bores 34 and the blind hole 32 . The blind hole 32 ends at a distance from the end face 64 of the piston 20 which bears against the circumference of the eccentric 62 , so that there is an end wall 68 with which the piston 20 bears against the circumference of the eccentric 62 . By a magnetic force of the permanent magnet 66 , the piston 20 is held in contact with the circumference of the eccentric 62 , so that when the eccentric 62 is driven in a rotating manner, the piston 20 executes a reciprocating axial movement in the bushing 12 , which conveys brake fluid by means of the piston pump 10 in a manner known per se. It is understood that the eccentric 62 consists of a magnetically attractable material, for example steel.

A cylindrical closure element 70 is placed on the liner bottom 18 and connected to the liner 12 with a flange 72 . The closure element 70 serves for the pressure-tight closing of the cylinder bore 14 and for fixing the liner 12 in the pump housing 16 . It is kept pressure-tight with a circumferential caulking 71 of the pump housing 16 . An outlet valve 74 in the form of a spring-loaded check valve is accommodated in the closure element 70 : The closure element 70 has a coaxial blind hole 76 , into which a helical compression spring as a valve closing spring 78 and a valve ball 80 as a valve closing body are inserted. The valve ball 80 interacts with a conical valve seat 82 , which is attached to an opening of a central bore 84 , which axially penetrates the bushing base 18 . The valve seat 82 is shaped and solidified by stamping. The fluid is discharged through radial channels 86 between the liner bottom 18 and the closure element 70 into an outlet bore 88 in the pump housing 16 .

Fig. 2 and 3 show modifications of the piston pump shown in Fig. 1, fiction, modern 10th The same reference numbers are used for the same components. In order to avoid repetitions, only the differences between the modified embodiments are explained below and reference is made to the statements relating to FIG. 1.

In the embodiment of the invention shown in FIG. 2, the eccentric 62 is designed as a permanent magnet in order to hold the piston 20 on the circumference of the eccentric 62 . To increase the magnetic force, the piston 20 can also have the permanent magnet 66 already described, but only the eccentric 62 can also be designed as a permanent magnet. It is understood that the piston 20 , at least if it is not magnetic and has no magnet, made of magnetically attractable material, for example made of steel.

In order to form the eccentric 62 as a permanent magnet, the eccentric 62 has a magnetic ring 90 , which is non-rotatably placed thereon and has radial magnetization. The magnetization of the magnetic ring 90 is shown in FIG. 2 by permanent magnets 92 , indicated by broken lines, which are inserted radially and with the same polarity in the magnetic ring 90 .

The magnetic ring 90 preferably does not have individual permanent magnets 92 , but the magnetic ring 90 is provided with radial magnetization. The magnetic poles of the permanent magnets 92 and the magnetic ring 90 are indicated by the letters N and S, it being irrelevant which pole is on the outside and which is on the inside. It is only necessary that the same pole is always on the outside and that the magnetization of the outside of the magnetic ring 90 is opposite to the magnetization of the permanent magnet 66 arranged in the piston 20 , so that the magnetic forces increase and do not repel.

In the illustrated in Fig. 3 embodiment of the invention applied to the circumference of the eccentric 62 end face 64 of the piston 20 is curved channel-shaped concave in the circumferential direction of the eccentric 62. Due to the concave design of the end face 64 , a contact surface of the piston 20 on the circumference of the eccentric 62 is enlarged and a gap 94 in the edge region of the piston 20 between the end face 64 of the piston 20 and the circumference of the eccentric 62 is smaller than that shown in FIG. 1 Embodiment of the invention. The concave design of the end face 64 causes an increased magnetic force between the piston 20 and the eccentric 62 . A radius of curvature of the concave end face 64 is larger than a radius of the eccentric 62 in order to ensure that the piston 20 always remains in good contact with the eccentric 62 , since the eccentric 62 also moves transversely to the piston 20 due to its eccentricity when it is rotating.

Claims (6)

1. Piston pump with a piston which is axially displaceably received in a cylinder bore in a pump housing, and with a rotatably drivable eccentric, on the circumference of which the piston rests with an end face, characterized in that the piston ( 20 ) and / or the eccentric ( 62 ) has a permanent magnet ( 66 , 92 ) which holds the piston ( 20 ) in contact with the circumference of the eccentric ( 62 ). 2. Piston pump according to claim 1, characterized in that a permanent magnet ( 66 ) is attached to the piston ( 20 ). 3. Piston pump according to claim 2, characterized in that the piston ( 20 ) has a check valve ( 42 ) for controlling a fluid flow through the piston pump ( 10 ), the check valve ( 42 ) on or in a hole ( 32 ) of the piston ( 20 ) is attached and that the permanent magnet ( 92 ) is inserted into the hole ( 32 ). 4. Piston pump according to claim 3, characterized in that the hole ( 32 ) is a blind hole ( 32 ). 5. Piston pump according to claim 1, characterized in that the piston ( 20 ) is magnetic. 6. Piston pump according to claim 1, characterized in that the piston ( 20 ) has a concavely curved end face ( 64 ) with which it rests on the circumference of the eccentric ( 62 ).