JP2000314373A - Piston pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate assembling operation of a piston pump, while reducing its structural length and reduce manufacturing cost of a piston of the piston pump. SOLUTION: A piston 16 is composed as a hollow piston, having an inner chamber forming a push-away chamber 42 of a piston pump 10. The piston pump 10 has a stationary internal part 24 entering an opening side of the piston 16. The piston 16 can axially be shifted along the internal part 24. The piston 16 is connected to the internal part 24 so as to make it incapable of being missed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a hydraulic brake system of the slip control type for a vehicle, which is of the type defined as a superordinate concept of the present invention.
The present invention relates to a piston pump having a piston driven for reciprocating stroke movement.

[0002]

2. Description of the Prior Art A piston pump of the above-mentioned type is known, for example, from DE-A-4107979. Known piston pumps have a cylindrical bolt-shaped piston, which is manufactured by machining to have a groove (undercut), a lateral hole and an axial blind hole. Manufacture of the piston is cumbersome and expensive because of the cutting process. The piston is guided slidably in the axial direction in the pump bore of the pump casing and is driven by a rotatable eccentric for reciprocating stroke movement in the axial direction. The piston is pressed against the peripheral surface of the eccentric ring by a piston return spring inserted into the pump hole. The piston return spring makes assembly of the piston pump difficult. This is because the piston return spring pushes the individual components of the piston pump out of the pump bore, unless the individual components are still secured in the pump housing. The displacement chamber of the piston pump is connected to the piston at one end face side of the piston in the pump hole. This has the disadvantage that the known piston pumps are long and require large construction volumes.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to reduce the cost of manufacturing a piston of a piston pump, in combination with making the structure of the piston pump short and simplifying the operation at the time of assembly. To achieve.

[0004]

Means for Solving the Problems According to the present invention, a piston is formed as a hollow piston, and an inner chamber of the hollow piston forms a displacement chamber of a piston pump. A piston pump having a stationary internal portion which penetrates into the open side of the piston, wherein the piston is axially shiftable along an outer periphery of the internal portion, and wherein the piston and the internal portion are It is irretrievably connected to each other.

[0005]

In summary, the piston pump according to the present invention, which has the structure described in the first aspect, has a piston configured as a hollow piston, and the inner chamber of the hollow piston is provided with a piston pump. A displacement chamber is formed. Since the piston is formed as a hollow piston and the displacement chamber can be displaced into the piston, a piston pump having a short structure and a compact structure can be obtained. A stationary interior part penetrates into the open side of the piston, which defines a displacement chamber on one side of the piston. Due to the internal part penetrating into the piston, the dead volume of the displacement chamber, in other words the minimum volume at the end of the discharge stroke, is reduced to almost zero, which results in a high efficiency of the piston pump. The piston and the inner part form a pre-assembled arrangement, because the piston is axially shiftable along the outer circumference of the stationary inner part and is permanently connected to said inner part. Thus, this pre-assembled arrangement is assembled independently of the other parts of the piston pump and can be stocked separately. This pre-assembly arrangement facilitates the operation up to the assembly operation of the piston pump, and in particular fits the piston together with the internal part into the pump bore, including the piston return spring present in the piston. Operation is remarkably simplified. It is no longer necessary to secure the piston on the internal part after assembling the pre-assembled components into the pump casing. This is because the piston is already secured on the inner part by the eccentric. Therefore, only small demands are made on the quality and strength of the non-lost joint between the piston and the internal part.

Claims 2 to 10 relate to advantageous embodiments and improvements of the constituent means of the present invention described in claim 1.

[0007] As can be seen from the third and fourth aspects, the piston has a snap joint or a mating joint with the internal part. This is not fixed again, and the piston snaps or meshes with the inner part when it is fitted over the inner part, whereby the piston is permanently connected to the inner part, and the Is formed. The snap joint is disengaged from the internal part by forcing the piston down. Both joints are shape-fitting joints that are realized by elastic deformation when the piston is fitted over the internal part.

[0008] The piston can be, for example, a plastic product. As described in claim 5, the piston of the piston pump according to the present invention is manufactured as a plastic deformation molded part by, for example, deep drawing, cold upsetting or cold extrusion pressing. The piston is, for example, tubular or sleeve-shaped and is formed with an integral piston end wall closing the piston on one side. The piston does not have an undercut at the time of its manufacture, so that it can be manufactured quickly and easily by plastic deformation in one operation step. The undercut portion of the piston, which engages the undercut portion of the inner portion in order to irreversibly couple the piston with the inner portion, is formed by, for example, edge bending, rolling, or the like when the piston is fitted over the inner portion. It can be integrally molded with the piston by stamping one or more projections. If the non-lost joint is a snap joint or a mating joint, an undercut is integrally formed with the piston before the piston is fitted over the internal part. It is also possible to harden the piston in order to increase the wear resistance, and it is not necessary to perform other processing or post-processing such as precision processing of the piston surface. This allows the piston to be manufactured inexpensively and quickly.

In accordance with another feature of the invention, the piston is designed as a stepped piston, ie the piston is guided along a pump bore in a pump casing at two different diameter sections which are axially separated from one another. And it is sealed. The design of the piston as a stepped piston results in an annular chamber surrounding the piston, the volume of which alternately increases and decreases during the reciprocating stroke movement of the piston. During the discharge stroke of the piston, which reduces the displacement chamber volume, the volume of the annular chamber increases, whereby fluid is drawn into the annular chamber by the piston pump. During the return stroke of the piston, the volume of the annular chamber decreases, but the volume of the displacement chamber increases more than the volume of the annular chamber decreases, so that the piston pump sucks fluid. By configuring the piston as a stepped piston, the piston pump of the present invention essentially sucks fluid both during the discharge stroke and during the return stroke. This has the advantage that the suction volume flow is more even and thus the suction and filling behavior of the displacement chamber of the piston pump is improved.

According to a seventh aspect of the present invention, a check valve (an inlet valve or an outlet valve) that controls the flow direction of the fluid discharged by the piston pump is provided in the internal portion. Is housed. By incorporating the check valve in the internal part, the structural space is reduced and a compact structure of the piston pump is obtained.

In a further embodiment, the check valve has a valve closure which is guided in the direction of the valve stroke by a valve closure guide. At least one fluid passage is provided to allow fluid to flow past the valve closure when the check valve is open. This fluid passage makes it possible to reduce the tolerance of the valve closing body guide relative to the valve closing body. Narrow tolerance valve closure guides have the advantage of reducing noise. Because
Lateral movement of the valve closing body which is opened and separated from the valve seat (i.e., lateral movement of the valve closing body caused by fluid flowing along the periphery of the valve closing body) is sufficiently prevented by the valve closing body guide. This is because that. In one embodiment of the invention, the valve closure guide has a guide rib extending in the valve stroke direction and formed, for example, in the form of a multi-shaped groove. Between the guide ribs, there are flow channels, which, in total, have a large area, so that even in the case of narrow tolerance valve closure guides, low flow of the check valve is achieved. Resistance occurs.

The piston pump of the present invention is provided as a pump used particularly in a vehicle brake system, and is used for controlling the pressure in a wheel brake cylinder. Depending on the brake system, the abbreviations ABS, A
SR, FDR, EHB are used. In a brake system, the pump may be, for example, to send brake fluid from one or more wheel brake cylinders back to a master brake cylinder (ABS) and / or to pump brake fluid from a storage tank to one or more wheel brake cylinders. (ASR, FDR, EHB).
The pump is, for example, in the case of a brake system with wheel slip control (ABS, ASR) and / or in the case of a brake system serving as a steering aid (FD).
R) and / or in the case of electro-hydraulic brake systems (EH
B). Wheel slip control system (AB
S, ASR), for example, blocking the wheels by applying a strong depressing force to a brake pedal during a braking operation (ABS) and / or idling the driving wheels of the vehicle by applying a strong depressing force to an accelerator pedal (ASR). Is prevented. In the case of a braking device serving as a steering assist (FDR), one or more wheel brakes are provided, regardless of the actuation of the brake pedal or the accelerator pedal, for example to prevent the vehicle from deviating from the driver's desired trajectory. Brake pressure builds up in the cylinder. The pump is an electro-hydraulic brake device (EH
B) can also be used, in which case the pump pumps the brake fluid to one or more wheel brake cylinders when the electric brake pedal sensor detects the actuation of the brake pedal, or It also serves to fill the accumulator of the brake system.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described in detail with reference to the drawings.

The illustrated piston pump 10 of the present invention is fitted in a pump hole 12 of a hydraulic block forming a pump casing 14. A hydraulic block (however, only the peripheral portion of the hydraulic block surrounding the piston pump 10 is shown in the drawing) is a hydraulic control circuit device (not shown) for a slip-controlled hydraulic brake device of a vehicle. Z). In the hydraulic block, other than the piston pump 10, a plurality of other hydraulic elements, such as an electromagnetic valve, are fitted and hydraulically connected to each other.

The piston pump 10 has a piston 16 formed as a hollow piston, which is sleeve-shaped and one end face of which is closed by a piston end wall 18 integrally formed with the piston 16. Have been. The piston 16 is enlarged in diameter toward the open end by a ring step 20 at about its longitudinal midpoint. The piston 16 is designed as a stepped piston, i.e., is sealed with different diameters in the region of its two ends. At the end closed by the piston end wall 18, the piston 16 is sealed by a seal ring 21 fitted in an annular groove formed in the peripheral wall of the pump hole 12, and the seal ring is In contact with the outer circumference. At its open end, the piston 16 is sealed by a seal and guide ring 28, which will be described later, or by a seal lip 32, which will be described later.
2 is in contact with the inner circumference of the piston 16.

The seal / guide ring 28 or the seal lip 32 contacts the large-diameter portion of the piston 16 and seals the piston 16 at a larger diameter portion than the seal ring 21 at the closed end of the piston 16. By sealing the piston 16 at different diameter locations, the piston 16 forms a stepped piston that causes the piston pump 10 to draw fluid both during the discharge stroke and during the return stroke. Thereby, the suction behavior of the piston pump 10 is improved. In contrast to the embodiment shown, the piston 16 can also be configured as a so-called single-acting piston, which is sealed at equal end portions in both end regions. For this purpose, in the embodiment shown, the ring step 20 must increase the piston radius by the thickness of the piston wall. Also, the piston 16 is manufactured without a step,
It is also possible to seal the outer periphery of both ends.

The piston 16 does not have any undercuts at the time of its manufacture and can therefore be manufactured without problems and simply by plastic deformation. In the embodiment shown, the piston 16 is made from a metal sheet by deep drawing. The piston is hardened to increase its wear resistance and no other processing or post-processing is performed.

A spigot-shaped attachment portion 22 of an inner portion 24 fixed in the pump hole 12 penetrates into the open end of the piston 16. The spigot-shaped attachment portion 22 integrally projects from a circular bottom disk 26 of the inner portion 24, and the inner portion 24 is fixed in the pump hole 12 by the bottom disk. The piston 16 is guided and slidably guided in the axial direction along the outer periphery of the spigot-shaped attachment portion 22 in the enlarged diameter region. In the illustrated embodiment of the invention for guiding and sealing, two different embodiments are illustrated in the left and right halves of the drawing. It should be noted that the two aspects shown are not realized together. Drawing the two embodiments together in the same drawing serves as a contrast for both embodiments.

In the left half of the drawing, a seal and guide ring 28 is provided.
Are mounted on the spigot-shaped attachment portion 22, and the spigot-shaped attachment portion 22
Is held on the outer periphery of Seal and guide ring 28
Is in liquid-tight contact with the inner peripheral surface of the piston 16. In the embodiment of the present invention shown in the left half of the drawing, the inner part 24 is used.
Can be manufactured together with the spigot-shaped attachment 22 from, for example, steel.

In the embodiment of the invention shown in the right half of the drawing, the inner part 24 is made of plastic, for example by injection molding. The spigot-shaped attachment portion 22 of the internal portion 24 has an annular seal lip 32 integrally formed with the spigot-shaped attachment portion, and the seal lip is in liquid-tight contact with the inner peripheral surface of the piston 16. In addition, the piston 16 is slidably guided in the axial direction. With this embodiment of the invention, a separate seal and guide ring is omitted.

The piston pump 10 is connected to the pump casing 1
After mounting the piston 16 on the inner part 24, the free edge 34 of the piston 16 is, for example, edge-bent, so that the piston 16 is permanently connected to the inner part 24 until it is assembled in the inner part 24. Alternatively, it is plastically deformed inward in the radial direction by rolling. The inwardly deformed free edge 34 engages the rear side of a ring step 35 provided on the inner part 24. The ring step 35 forms an undercut 36 of the internal part 24. In the embodiment shown in the left half of the figure, in order to form the undercut 36, the ring step 35 causes the seal and guide ring 28 to extend radially outward beyond the outer periphery of the spigot-shaped attachment 22 of the inner part 24. It is formed by overhanging. In the embodiment shown in the right half of the drawing, the ring step 35 is directly formed integrally with the spigot-shaped attachment part 22 of the inner part 24. By irreversibly connecting the piston 16 to the internal part 24, a pre-assembly arrangement is obtained which greatly simplifies the operation when stocking, transporting and assembling in the pump casing 14.

In order to drive the piston 16 to reciprocate in the axial direction within the pump hole 12, the piston pump 10 has an eccentric wheel 38 that is driven to rotate by an electric motor. Around the
The piston end wall 18 of the piston 16 is pressed by a piston return spring 40 formed as a compression coil spring. The piston return spring 40 is disposed in the inner chamber of the piston 16 and is supported by the spigot-shaped attachment portion 22 of the internal portion 24.
8 is pressed. The inner chamber of the piston 16, which is defined by the spigot-shaped attachment portion 22 penetrating into the open side of the piston 16, forms a displacement chamber 42 of the piston pump 10, and the volume of the displacement chamber is determined by the reciprocating stroke of the piston 16. The piston pump 10 discharges a fluid (brake fluid) in a known manner.

An inlet valve 44 of the piston pump 10 is housed in the inner chamber of the piston 16 forming the displacement chamber 42. The inlet valve 44 is configured as a spring-loaded check valve. The inlet valve 44 has a pot-shaped valve seat portion 46.
The valve seat part is made as a plastic part and contacts the inner wall of the piston end wall 18 by the bottom. The piston return spring 40 presses the valve seat portion 46 from the inside against the piston end wall 18, thereby retaining the valve seat portion 46 in the piston 16.

Since the valve seat portion 46 has a diameter smaller than the inner diameter of the piston 16, an annular chamber 48 is formed between the valve seat portion 46 and the piston 16. The annular chamber 48 is closed on the open side of the piston 16 by a sealing lip 50. The sealing lip 50 separates the displacement chamber 42 from the annular chamber 48. The bottom of the valve seat portion 46 is penetrated by a center hole 52, the opening of which is formed as a conical valve seat 54 of the inlet valve 44. A plurality of radial grooves 56 radially drilled in the bottom of the valve seat portion 46 communicate the annular chamber 48 with the center hole 52.

The inlet valve 44 has a valve ball 58 as a valve closing body, which is pressed against the conical valve seat 54 by a compression coil spring as a valve closing spring 60. Valve closing spring 6
0 is supported by a spigot-shaped attachment portion 22 of an internal portion 24 that enters the piston 16.

The intake of fluid into the piston pump 10 is effected by means of an inlet bore 62 which is formed in the pump casing 14 and extends radially through the pump bore 1.
It opens to 2. From the pump hole 12, a plurality of through-holes 64 punched and formed from the peripheral wall of the piston 16 are formed.
And flows into the annular chamber 48 between the valve seat portion 46 and the peripheral wall of the piston 16 and from there further through the radial groove 56 and the center hole 52 to the inlet valve 44.

The outlet valve 66 of the piston pump 10 is housed in a center hole 68 that passes through the internal part 24 in the axial direction. The center hole 68 expands conically to form a valve seat 70. A compression coil spring as the valve closing spring 72 presses a valve ball 74 as a valve closing body against the valve seat 70.

The valve closing spring 72 is supported by a circular closing disk 76, which is fitted in the pump hole 12. The closing disk 76 is held in the pump hole 12 by an annular caulking portion 78 of the pump casing 14 and seals the pump hole 12 with pressure tightness. The closing disk 76 itself holds the internal part 24 fixedly in the pump bore 12 at the bottom disk 26 of the internal part.

Fluid flowing out of the outlet valve 66 passes through a plurality of radial passages 80 radially disposed between the bottom disk 26 and the closing disk 76 of the inner portion 24 to form an outlet hole 82.
The outlet hole is formed in a pump casing 14 radially with respect to the pump hole 12.

The inner part 2 surrounding the valve ball 74 of the outlet valve 66
The center hole 68 has a plurality of guide ribs 84 arranged in parallel to the axis, and the guide ribs are formed in the form of inner knurled or multi-shaped grooves. The guide rib 84 guides the valve ball 74 in the valve stroke direction, that is, in the axial direction, with a narrow radial tolerance. There is a flow groove between the guide ribs 84, and the flow groove is
It has a large area for passing the fluid flowing out through the outlet valve 66.

[Brief description of the drawings]

FIG. 1 is an axial sectional view of a piston pump according to a preferred embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 10 piston pump, 12 pump hole, 14 pump casing, 16 piston, 18 piston end wall, 20 ring step, 21 seal ring,
22 spigot-shaped attachment part, 24 internal part, 2
6 bottom disk, 28 seal and guide ring, 30 caulked portion, 32 seal lip, 34 free edge,
36 undercut part, 38 eccentric ring, 40 piston return spring, 42 displacement chamber, 44 inlet valve, 46 valve seat part, 48 annular chamber, 50 seal lip, 52 center hole, 54 conical valve seat, 5
6 radial groove, 58 valve ball, 60 valve closing spring,
62 inlet hole, 64 through port, 66 outlet valve,
68 center hole, 70 valve seat, 72 valve closing spring,
74 valve ball, 76 closing disk, 78 caulking part,
80 radial passage, 82 exit hole, 84 guide rib

Claims (10)

[Claims] 1. A piston pump having a piston driven for reciprocating stroke movement, wherein the piston (16) is configured as a hollow piston, and the inner chamber of the hollow piston is a displacement chamber (42) of the piston pump (10). ) And a piston pump (10)
Has a stationary internal part (24) which penetrates into the open side of said piston (16), and said piston (16) is axially shiftable along said internal part (24);
And a piston pump characterized in that said piston (16) and the internal part (24) are undetachably connected to each other. 2. An internal part (24) comprising a piston (16).
2. An undercut portion (36) of the first member.
The described piston pump. 3. The piston pump according to claim 1, wherein the non-lostable connection between the piston (16) and the internal part (24) is a holding joint. 4. The piston pump according to claim 3, wherein the holding joint is a snap joint or a meshing joint. 5. The piston pump according to claim 1, wherein the piston is a plastically deformed part. 6. The piston pump according to claim 1, wherein the piston (16) is formed as a stepped piston. 7. The piston according to claim 1, wherein a check valve (66) for controlling the flow direction of the fluid flowing through the piston pump (10) is accommodated in the inner part (24). pump. 8. The non-return valve (66) includes a valve closing body (74).
And a valve closing body guide (84) for guiding the valve closing body (74) in the valve stroke direction.
8. The piston pump according to claim 7, wherein 4) has at least one fluid passage for allowing fluid to flow along the valve closing body (74) when the check valve (66) is opened. 9. A check valve (66) having a plurality of guide ribs (84) as valve closure guides for a valve closure (74), said guide ribs (84) flowing between each other. Define a groove,
The piston pump according to claim 8, wherein the check valve (66) is allowed to flow along the valve closing body (74) when the check valve is opened. 10. A check valve (44) for controlling the direction of flow of a fluid flowing through a piston pump (10) is arranged in the inner chamber (42) of the piston (16). Piston pump.