WO1996018533A1

WO1996018533A1 - Electromagnetically controlled valve, in particular for antislip hydraulic braking systems in motor vehicles

Info

Publication number: WO1996018533A1
Application number: PCT/DE1995/001609
Authority: WO
Inventors: Johann Herr; Klaus Heyer; Günther HOHL; Uwe Breithaupt; Massimo Ambrosi
Original assignee: Robert Bosch Gmbh
Priority date: 1994-12-17
Filing date: 1995-11-18
Publication date: 1996-06-20
Also published as: DE4445221A1; JPH11500678A; EP0796186A1; KR987000204A

Abstract

The object of the invention is to develop a valve having a simple design and cheap to produce capable of automatically setting a reduced flow cross-section depending on its closed position. The valve (14) has a magnet armature (33) that moves in the longitudinal direction in a valve dome (26) and a valve plunger (34) that actuates a seat valve (43). The seat valve lies in a valve chamber (48) from which hydraulic medium channels (65, 74) lead to both faces (59, 67) of the magnet armature (33). When the valve (14) moves away from its closed position, an additional force acts on the magnet armature (33) in the closing direction and places the seat valve in a partially closed position different from its rest position. The magnet armature (33) and the valve plunger (34) are separate pieces that engage each other at a tight seat (61). The valve plunger (34) is designed as a plastic injection-moulded part and has a valve partial chamber (51) that communicates with a longitudinal bore that forms a part of a hydraulic medium channel (65). The valve (14) is particularly suitable for antislip hydraulic braking systems of motor vehicles.

Description

Electromagnetically actuated valve, in particular for slip-controlled hydraulic brake systems in motor vehicles

State of the art

The invention is based on an electromagnetically actuated valve, in particular for slip-controlled hydraulic brake systems in motor vehicles, according to the preamble of claim 1.

Such a valve is known from DE 39 34 771 Cl, Figure 3. It has a control piston which is arranged in the valve dome and forms a stop for the magnet armature and which is guided in a longitudinally displaceable manner on a pin which starts from the valve body and penetrates the valve tappet pressed into the magnet armature. The control piston, with its base facing away from the anchor, delimits a control chamber which is formed in the valve dome and serves as a cylinder for the piston and which is connected to the pressure medium inlet of the known valve by a pressure medium channel penetrating the pin and the control piston at the same axis. While the magnet armature is pressure-balanced on both end faces, pressure introduced into the control chamber is able to axially move the control piston against a stop. This reduces the stroke of the Magnet armature by a predetermined amount, which results in a restriction of the flow cross-section.

This mode of operation of the known valve can be used in slip-controlled hydraulic brake systems in which the pressure medium inlet is connected to the master brake cylinder and the pressure medium outlet is connected to a wheel brake cylinder. E.g. in the event of a brake slip control, the valve is switched into its closed position by energizing the solenoid coil and, when the pressure in the wheel brake cylinder is reduced, a pressure gradient of sufficient height is generated between the pressure medium inlet and the pressure medium outlet, this causes the above-described displacement of the control piston with the result that When opening the valve, the above-mentioned throttling of the flow cross-section takes effect as long as the pressure difference between the inlet and outlet exists. The reduction in the flow cross-section has a favorable effect on the control quality and the noise behavior of the brake system due to the reduced pressure gradient in the pressure build-up of a brake slip control following a pressure reduction. With normal braking without risk of blocking, however, the full flow cross-section of the valve is available, which promotes a desired short response time of the brake system when the brake is applied.

The known valve is problematic in terms of production technology if it is taken into account that only very small amounts of pressure medium are displaced in modern slip-controlled hydraulic brake systems, in particular of passenger cars, which require valves of a size which is only about a fifth of the dimensions of that valve from the publication cited at the beginning corresponds. Accordingly, it is difficult to the pressure medium channel in the guide pin made of a metallic material for the magnet armature to produce by machining. In addition, a further machining operation is required in order to generate the valve sub-chamber acting as storage space by opening the guide pin on the valve seat side. Finally, the known valve is also expensive in that the valve tappet requires a gap seal on the guide pin in order to maintain the pressure balance of the magnet armature.

Advantages of the invention

The valve according to the invention with the characterizing features of claim 1 has the advantage that the magnet armature and the valve tappet are separate and thus mutually angularly movable components, but nevertheless a reliable transmission of the pressure through the first pressure medium channel into the control chamber remote from the locking member is ensured. Production-related misalignments between the magnet armature and the valve tappet can be tolerated because they do not impair the tightness of the pressure medium channel. In addition, the arrangement of the first pressure medium channel in the valve tappet simplifies the construction of the valve according to the invention compared to the known valve. In addition, the design of the valve tappet as a plastic injection molded part achieves a considerable cost advantage over a valve tappet made of steel which is produced by machining. The plastic injection molding technology also allows a pressure medium channel and a valve subchamber to be created in the valve tappet, which have a different cross-sectional profile, but still communicate with one another.

The measures listed in subclaims 2 to 5 are advantageous developments and Improvements of the valve specified in claim 1 possible.

These measures are distinguished by the fact that they can be produced on the valve lifter in a single molding process, that is to say without reworking.

Finally, sub-claim 6 specifies a thermoplastic which withstands the high stresses in a slip-controlled hydraulic brake system with a sufficient safety reserve.

drawing

An embodiment of the invention is shown in simplified form in the drawing and explained in more detail in the following description. 1 shows a longitudinal section through an electromagnetically actuated valve in a schematically indicated brake system of a motor vehicle, FIGS. 2 to 4 show a longitudinal view and end views in the direction of the arrows III and IV in FIG. 2 of a valve lifter used in the valve, and FIG. 5 shows a longitudinal section through the valve lifter along the line VV in FIG. 2.

Description of the embodiment

A brake slip-controlled hydraulic brake system 10 of a motor vehicle, which is shown in a very simplified form in FIG. 1, has a two-circuit master brake cylinder 11, from which a brake line 12 to a wheel brake cylinder 13 extends. Arranged in the course of the brake line 12 is an electromagnetically actuated valve 14 which acts as an inlet valve in a slip control. In a bypass line 15 bypassing the valve 14 there is a non-return Valve 16 with passage direction from the wheel brake cylinder 13 to the master brake cylinder 11. On the wheel brake cylinder side, a return line 17 extends from the brake line 12, which bypasses the valve 14 and the check valve 16 and is connected to the brake line 12 on the master brake cylinder side. In the return line 17 there is an outlet valve 18 and a return pump 19 for the wheel brake cylinder 13 removed pressure medium. A storage chamber 20 is connected to the return line 17 between the outlet valve 18 and the return pump 19.

The electromagnetically actuated valve 14 has a valve housing 23 which is intended to be received in a valve block (not shown) and which is firmly connected to a yoke disk 24. The valve housing 23 is over the yoke plate

24 continued with a pole core 25. On the pole core

25, a closed, capsule-shaped valve dome 26 is attached. It is tightly connected to the pole core 25 by welding. The valve dome 26 facing away from the pole core has a hemispherical termination.

The valve dome 26 is encompassed by an annular magnet coil 29. A bell-shaped housing 30 surrounds the magnetic coil 29. The housing 30 engages on the one hand with the valve dome 26; on the other hand, it is connected to the yoke plate 24.

In the valve dome 26, which is closed on the coil side, an essentially circular cylindrical magnet armature 33 is accommodated in a longitudinally movable manner. A valve tappet 34 is assigned to the magnet armature 33 as a separate component. The valve lifter 34, which has a substantially circular cross section, is produced as an injection molded part from a thermoplastic, for example from carbon fiber-filled polyaryl ether ketone (PAEK). The valve lifter 34 is received in a longitudinal bore 35 of the pole core 25 and valve housing 23 with play. On At its end facing away from the anchor, the valve lifter 34, which is further described in more detail, carries a closing element designated by 36 (FIGS. 2, 3 and 5).

In the section of the longitudinal bore 35 facing away from the anchor, a sleeve-shaped valve body 39 with a stepped bore 40 is pressed, which opens into a valve seat 42 shaped like a hollow cone after a through bore 41 of smaller diameter. The valve needle 36 and the valve seat 42 form a seat valve 43 of the electromagnetically actuated valve 14. When the solenoid 29 is not energized, as shown in FIG. 1, the seat valve 43 takes due to the action of a prestressed return spring acting on the valve stem 34 and on the valve body 39 44 its open position as the rest position, in which the valve tappet 34 is supported on the magnet armature 33 and this is axially supported on the valve dome 26. When the solenoid coil 29 is energized, the valve 14 is moved into the blocking position, in which the valve needle 36, which is formed at the end as a spherical section 45, engages the valve seat 42.

The valve housing 23 is provided with a transverse bore 47 crossing the longitudinal bore 35 at right angles. A valve chamber 48 accommodating the seat valve 43 is created in the penetration area of both bores 35 and 47. On the one hand, this is connected via the valve seat 42 and the central through bore 41 to the stepped bore 40 as a pressure medium inlet of the valve 14; on the other hand, a pressure medium outlet formed by the transverse bore 47 is connected to the valve chamber 48. (The designations inlet and outlet apply to the build-up of brake pressure in the wheel brake cylinder 13. In the case of non-slip-controlled braking, the pressure medium also flows through the valve 14 in the opposite direction.) As can best be seen from FIG. 5, the straight circular cylindrical valve needle 36 is surrounded by a hollow cylindrical recess which forms a valve partial chamber 51 which is open at the end against the valve seat 42. This, in turn, is enclosed on the circumferential side by a sleeve-shaped section 52 of the plunger 34 that extends coaxially with the valve needle 36. The section 52 ends at the end at a distance in front of the ball section 45 of the valve needle 36, so that it can engage the valve seat 42 in the closed position of the valve 14, while the sleeve-shaped section 52 is at a short distance from the valve body 39.

The valve needle 36 is connected towards the bottom of the valve chamber 51 by means of two diametrically opposed webs 55 which are approximately quarter-circular in cross section with the valve lifter 34. Following the valve needle 36, a longitudinal bore 56 is formed in the valve stem 34. This communicates with the valve subchamber 51 on the valve needle side (FIGS. 3, 4 and 5). On the magnet armature end 57 of the valve tappet 34, the longitudinal bore 56 opens into a spherical zone 58. This is associated with a hollow cone-shaped countersink 60 on the end 59 close to the closing element (FIG. 1). As a result, a sealing seat 61 is formed between the magnet armature 33 and the valve tappet 34 and, like the seat valve 43, has a cone-and-ball configuration. Deviating from this, the countersink 60 in the magnet armature 33 can also be hollow.

The longitudinal bore 56 of the valve tappet 34 is continued in the armature 33 through a stepped, continuous bore 64. The longitudinal bore 56 of the valve tappet 34 and the bore 64 of the magnet armature 33 form a first pressure medium channel 65, which extends from the valve sub-chamber 51 while penetrating the sealing seat 61 to one First control chamber 66 extends between the end 67 remote from the closing element of the magnet armature 33 and the valve dome 26. The sealing seat 61 ensures the leak-free passage of the first pressure medium channel 65 between the valve lifter 34 and the magnet armature 33. The sealing seat 61 maintains this sealing effect even when it is at an angle, ie when the axis 68 of the magnet armature 33 and valve tappet 34 bends. Such an inclination can occur in particular when the valve dome 26 is tilted and placed on the pole core 24 and the magnet armature 33 is accommodated in the valve dome with very little radial play. In addition, due to its shape, the sealing seat 61 ensures centering of the valve lifter 34 on the magnet armature 33 under the action of the force of the return spring 44 and hydraulic forces prevailing on the part of the seat valve 43.

The radial mobility of the valve tappet 34 required in the area of the magnet armature 33 is restricted by the guide section 71 facing away from the armature. This is designed as a spherical disk-shaped reinforcement that protrudes over the circumference of the valve lifter 34 and ends with a recess 72 on the sleeve-shaped section 52. While the guide section 71 engages with little play in the longitudinal bore 35, the recess 72 serves as a support surface for the return spring 44. In addition, the valve tappet 34 is also provided with three longitudinal flats 73 which are evenly distributed over its circumference in order to create a second pressure medium channel 74 , which starts from the valve chamber 48 outside the sleeve-shaped section 52 of the valve tappet and leads to a second control chamber 75 near the closing member between the pole core 25 and the magnet armature 33 (FIG. 1). Instead of the flats 73, longitudinal grooves can also be provided. Finally, it should also be pointed out that a sealing sleeve 76 on the circumferential side of the magnet armature 33 also against the first Control chamber 66 directed, on the valve dome 26 engaging sealing lip 77 is received.

The operation of the valve 14 is described in detail in the older DE application P 44 32 047.7. The content of that earlier application is therefore intended to be part of the disclosure of this application. It is only briefly noted that the valve 14 assumes its open position during normal braking and slip-controlled braking in pressure build-up phases, and is switched into its blocking position in pressure-maintaining and pressure reduction phases of the slip-controlled braking. If the valve 14 is electrically switched off after such phases, it automatically assumes a partially open position in the case of a sufficiently large pressure drop between the inlet and outlet sides, in which the flow cross-section of the seat valve 43 adjusts to largely constant flow rates which are lower than the full opening. This is caused by dynamic pressure which occurs when the seat valve 43 opens in the valve sub-chamber 51 and is transmitted through the first pressure medium channel 65 into the first control chamber 66, where it causes a force component directed against the tappet 34 on the magnet armature 33, which hydraulic opening forces and counteracts the force of the return spring 44.

Claims

Expectations

1. Electromagnetically actuated valve (14), in particular for slip-controlled hydraulic brake systems in motor vehicles, with the following features:

a magnet armature (33) is accommodated in a valve dome (26) and can be moved longitudinally,

- The valve dome (26) is encompassed by a magnetic coil (29),

- The solenoid armature (33) is assigned a valve tappet (34) with a closing element (36) of a seat valve (43) that faces away from the anchor,

a valve body (39) with a valve seat (42) with a central through-bore (41) as a pressure medium inlet of the seat valve (43) is fastened in a housing (23) of the valve (14),

- When the magnet coil (29) is not energized, the closing member (36) is lifted off the valve seat (42) due to the action of a return spring (44),

the closing member (36) and the part of the valve body (39) which has the valve seat (42) are located in a valve chamber (48) which is connected to a pressure medium outlet of the valve (14), - The valve chamber (48) has a valve compartment chamber (51) acting as storage space, from which a first pressure medium channel (65) extends to a control chamber (66) which is located between the end face (67) of the magnet armature (33) and the valve dome ( 26) is located

a second pressure medium channel (74) leading from the valve chamber (48) leads to the end face (59) of the magnet armature (33) close to the closing member,

- A pressure generated in the valve part chamber (51) is able to produce in the control chamber (66) a force acting counter to the force of the return spring (44), due to which the seat valve (43) assumes a partially closed position which deviates from its rest position through the other features:

- The magnetic armature (33) and the valve tappet (34) are designed as separate components and engage under the action of the return spring (44) in a sealing seat (61) encompassing the first pressure medium channel (65), which on one component has a countersink (60) and on the other component is designed as a raised spherical zone (58),

- The valve tappet (34), starting from its magnet armature-side end face (57), is provided with a longitudinal bore (56) forming the first pressure medium channel (65), which extends into a hollow cylindrical recess encompassing the closing member (36) as against the valve seat (42 ) passes over the valve part chamber (51),

- The valve lifter (34) is designed as a plastic injection molded part.

2. Valve according to claim 1, characterized in that radially extending webs (55) connect the closing member (36) formed as a straight circular cylindrical valve needle with an axially at least partially enveloping, sleeve-shaped section (52) of the valve tappet (34).

3. Valve according to claim 1, characterized in that the valve tappet (34) has a raised, spherical disk-shaped guide portion (71) on the circumferential side.

4. Valve according to claim 3, characterized in that the guide portion (71) of the valve lifter (34) against the valve seat (42) is limited by a recess (72) on which the return spring (44) engages.

5. Valve according to claim 1, characterized in that the second pressure medium channel (74) by at least one longitudinal, the circular cross-section of the valve lifter (34) trimming flat portion (73) or groove is formed.

6. Valve according to claim 1, characterized in that the valve lifter (34) consists of a carbon fiber filled polyaryl ether ketone (PAEK).