Pressure control valve arrangement having pressure medium guiding surface integrally formed onto a projection of the cover

A pressure control valve arrangement for controlling a fluid pressure in an ABS brake system of a vehicle so that, while there is a tendency of individual wheels of the vehicle to lock, the brake pressure in at least one associated brake cylinder can be adaptively adjusted, including: a housing; and at least one diaphragm valve is accommodated in the housing, the diaphragm valve having a diaphragm as the valve body, which diaphragm can be acted upon by introducing pressure medium into a control chamber that is covered on the outside of the housing by a cover so that the control chamber is formed between the diaphragm and the cover, wherein at least one pressure medium channel carrying pressure medium is formed in the housing in the region of the cover, wherein at least one cover has at least one projection projecting into the pressure medium channel in the housing, a pressure medium guiding surface for directing the flow of the pressure medium carried in the pressure medium channel being formed on the projection.

FIELD OF THE INVENTION

The present invention relates to a pressure control valve arrangement for controlling the fluid pressure in an ABS brake system of a vehicle in such a way that, while there is a tendency of individual wheels of the vehicle to lock, the brake pressure in at least one associated brake cylinder can be adaptively adjusted, wherein at least one diaphragm valve is accommodated in a housing of the pressure control valve arrangement, the diaphragm valve having a diaphragm as the valve body, which diaphragm can be acted upon by introducing pressure medium into a control chamber that is covered on the outside of the housing by a cover in such a way that the control chamber is formed between the diaphragm and the cover, and wherein at least one pressure medium channel carrying pressure medium is formed in the housing in the region of the cover, in accordance with the features described herein.

BACKGROUND INFORMATION

ABS (antilock brake system) prevents wheels from locking and comes into operation when a higher friction coefficient between a tire and the road is demanded than can be transmitted, i.e. when the driver brakes too hard. In the case of excessively hard braking, the central electronic control unit of the ABS brake system detects the tendency for one or more wheels to lock from rotational speed detector signals and, from these signals, calculates the activation of the pressure control valve arrangement acting on the associated brake cylinder. The brake pressure is then adjusted to an optimum slip of the pressure control valve arrangement, which lowers, holds or builds up the pressure in accordance with the wheel behavior and hence with the friction conditions between the tire(s) and the road.

ABS pressure control valve arrangements without a relay action, to which the exemplary embodiments and/or exemplary methods of the present invention relate, are used on vehicles such as commercial vehicles, buses, semitrailer trucks and trailers. Pressure control valve arrangements without a relay action generally have 3/2-way solenoid valves as pilot control valves for diaphragm valves, wherein an electronic control device activates the 3/2-way solenoid valves to enable the functions required for ABS operation, “pressure holding”, “pressure reduction” and “pressure buildup”, to be carried out. During a braking operation which does not involve a response by the ABS (no tendency for a wheel to lock), the pressure medium, generally air, flows through the pressure control valve arrangements unhindered in both directions during air admission to and venting from the brake cylinders. This ensures that the operation of the service brake system is not affected by the ABS pressure control valve arrangement.

Within the housing, pressure control valves of the type in question in the form of single-channel pressure control valves for antilock systems of motor vehicles have respective diaphragm valves as a holding valve and an outlet valve and respective solenoid control valves for the holding valve and the outlet valve. The two diaphragm valves each contain a diaphragm, which can be acted upon by the pressure in a control chamber, wherein the control chamber is closed off from the outside by a cover secured on the housing.

A pressure control valve arrangement of the type in question for an ABS brake system is known from EP 0 266 555 A1, for example. In the prior-art pressure control valve arrangements, the two diaphragm valves are generally arranged on the side of the housing, wherein the corresponding pilot control spaces are closed off by covers secured on the side of the housing. These covers are produced by primary forming processes such as injection molding. Pressure medium channels are furthermore formed in the housing in order to carry pressure medium within the housing to and from the various connections of the pressure control valve arrangement and to and from the diaphragm valves and to and from the solenoid valves controlling the above valves.

The pressure medium channels may run in a vertical and/or horizontal direction within the housing because then the housing does not have to be re-clamped during the machining of the pressure medium channels of a machining center, for example. A change in the direction of such a pressure medium channel is problematic in terms of flow engineering because the deflection of the flow in the pressure medium channel concerned is then generally 90 degrees (deflection from the vertical to the horizontal or vice versa) and this results in relatively high flow losses due to the abrupt deflection in such a pressure medium channel elbow. However, because a high dynamic response is required in pressure control valve arrangements for ABS/ASR systems and as rapid as possible venting of the brake cylinder concerned is required, for example, in the context of the “pressure lowering” function when the permissible wheel slip is exceeded, such flow losses caused by deflections must be kept as small as possible.

Because the installation dimensions of such a pressure control valve arrangement, especially the installation width thereof, are standardized and invariable owing to restricted space conditions, a solution to this problem cannot consist in enlarging the flow cross sections of the pressure medium channels.

Given this situation, it is the underlying object of the invention to develop a pressure control valve arrangement of the type mentioned at the outset in such a way that the flow losses or flow resistance, especially in pressure medium channels deflecting a pressure medium flow, are reduced. At the same time, the outlay on the production and finishing of the manner for achieving this object should be as low as possible.

SUMMARY OF THE INVENTION

According to the present invention, this object may be achieved by the features described herein.

The exemplary embodiments and/or exemplary methods of the present invention provide that at least one cover has at least one projection projecting into the pressure medium channel in the housing, a pressure medium guiding surface for directing the flow of the pressure medium carried in the pressure medium channel being formed on the projection.

Since such a cover is present in any case for the purpose of covering and/or sealing off a control chamber of a diaphragm valve of the pressure control valve arrangement and, according to an additional function, it is now also the carrier of a projection with a pressure medium guiding surface which guides the flow or, in the case of a deflection, deflects the flow, it advantageously performs a dual function in a single component.

In this case, the flow-guiding or flow-deflecting pressure medium guiding surface of the projection projecting into the pressure medium channel is advantageously configured in such a way that the flow losses or flow resistance of the pressure medium channel concerned, excluding the surface in the pressure medium channel, is/are reduced.

Owing to the reduced flow resistance, the pressure control valve arrangement consequently has an improved dynamic response without a change in the flow cross section of the pressure medium channel concerned, and this has a positive effect in terms of the required rapid succession of pressure reduction, pressure holding and pressure increasing phases.

Advantageous developments and improvements of the exemplary embodiments and/or exemplary methods of the present invention indicated herein are possible of the measures presented in the further description herein.

The projection having the pressure medium guiding surface may project into the pressure medium channel at a location at which deflection of the flow of the pressure medium within the pressure medium channel from a section of the pressure medium channel which leads in one direction into a section of the pressure medium channel which leads in another direction is envisaged. In order to achieve this, one or the other section of the pressure medium channel can, for example, extend as far as an aperture in a side face of the housing, into which opening the projection of the cover then projects in the manner of a spigot.

The deflection of the flow of the pressure medium within the pressure medium channel may be substantially 90 degrees, wherein the pressure medium guiding surface of the projection is designed to deflect the flow of the pressure medium from one direction to the other.

According to a development, the pressure medium channel is a vent channel, which carries compressed air from a diaphragm valve designed as an outlet valve to a vent of the pressure control valve arrangement. In this case, a central area of the cover may serve to cover the control chamber of the diaphragm valve designed as an outlet valve, and the at least one projection having the pressure medium guiding surface is formed at the edge of a nose of the cover.

If the cover provided with the projection and the pressure medium guiding surface is designed as an integral injection molding made of plastic or metal, production and assembly costs are advantageously low.

Further measures that improve the exemplary embodiments and/or exemplary methods of the present invention are explained in greater detail below together with the description of an embodiment of the invention with reference to the drawings.

DETAILED DESCRIPTION

According toFIG. 1, a vehicle fitted with an ABS brake system has a front axle1and a rear axle2. Wheels3aand3bare arranged on the front axle1; the rear axle2has wheels4aand4b, each fitted with twin tires, for example. In this case, the ABS brake system used to brake these wheels3a,3band4a,4bis in the form of a four-sensor/4-channel system. This means that, in this case, a total of four rotational speed sensors5a-5band four pressure control valve arrangements7a-7dare available. The pressure control valve arrangements7a-7dare used to control respectively associated brake cylinders6a-6d. All the pressure control valve arrangements7a-7dare connected to a foot brake valve9by a branching pneumatic brake pressure line8.

In actuating the foot brake valve9, the driver generates a brake pressure, which, passing through the pressure control valve arrangements7a-7dvia the pneumatic brake pressure line8, is transmitted to the brake cylinders6a-6dassociated with wheels3a,3band wheels4a,4b.

The pressure control valve arrangements7a-7dcan be activated by integrated solenoid valves15a,15b, shown inFIG. 2a,FIG. 2bandFIG. 4, and, for this purpose, are connected electrically to a central electronic control unit10. On the input side, the electronic control unit10is connected to the four rotational speed sensors5a-5bthat detect the wheel speeds. If a wheel3a-3dlocks, the brake pressure input by the driver via the foot brake valve9is reduced by the corresponding pressure control valve arrangement7a-7din an ABS control operation under the command of the electronic control unit10until locking has been eliminated. The ABS brake system in the embodiment under consideration furthermore comprises an ASR function, which comprises an ASR unit11for reducing the engine torque, an ASR solenoid valve12and a shuttle valve13.

Here, the pressure control valve arrangement7used for the purpose of ABS control as part of the ABS brake system in accordance withFIG. 2ais constructed in the manner of a single-channel pressure control valve arrangement and essentially comprises two integrated diaphragm valves14aand14band two spring-loaded solenoid valves15a,15b,which control the diaphragm valves. The diaphragm valves14aand14bare each biased in the closing direction by spring elements16a,16band are pilot-controlled of the respectively associated solenoid valves15aand15b.

InFIG. 2a, the pressure control valve arrangement7is shown in the open position thereof, in which a pressure buildup to the connected brake cylinder6takes place. In this case, neither of the solenoid valves15aand15bis electrically activated. In the position shown, the compressed air coming from the foot brake valve9pushes open diaphragm valve14a, which is designed as an inlet valve. The normally closed solenoid valve15aprevents the associated diaphragm valve14afrom being closed again. Via the normally open second solenoid valve15b, the brake pressure coming from the foot brake valve9closes the second diaphragm valve14b, which serves as an outlet valve. The compressed air thus passes unhindered through the pressure control valve arrangement7. The pressure control valve arrangement7is in this state also when there is no ABS control taking place.

To hold the brake pressure constant in a brake cylinder6ato6d, all that is required is to energize solenoid valve15a, as a result of which the valve opens and, as a consequence, the brake pressure coming from the foot brake valve9pushes shut the inlet-side diaphragm valve14a. The pressure on the right hand side and the left hand side of diaphragm valve14ais now equal. However, since the effective area on the left hand side of diaphragm valve14ais larger, diaphragm valve14ais closed. The same applies to the outlet-side diaphragm valve14bcontrolled by solenoid valve15b. To hold the pressure constant, the pressure control valve arrangement7thus closes the pneumatic brake pressure line8running from the foot brake valve9to the brake cylinder6.

According toFIG. 2b, a pressure reduction in a brake cylinder6ato6dis achieved by energizing both solenoid valves15aand15b. The statements made above on maintaining the pressure apply to solenoid valve15aand the associated inlet-side diaphragm valve15a. The other solenoid valve15b, on the other hand, is closed due to energization. The pressure coming from the brake cylinder6therefore pushes the outlet-side diaphragm valve14bopen, and the brake cylinder6is vented.

The above-described functions of the pressure control valve arrangement7are carried out in the manner described at the outset as part of an ABS/ASR control operation under the command of the electronic control unit10.

InFIG. 3andFIG. 4, the pressure control valve arrangement7illustrated only schematically inFIG. 2aandFIG. 2bis shown in a specific embodiment in the installed position, i.e. the components described above are at the top. In this embodiment, the two solenoid valves15a,15bfor pilot control of the diaphragm valves14a,14bare combined in a dual solenoid valve, although it operates in a manner similar to individual valves15a,15b.

The two solenoid valves15a,15bhave a double magnet18housed in a block17, having two magnet coils, which interact with two solenoid valve seats. Magnet armatures, which interact with the solenoid valve seats of the solenoid valves15a,15band are not shown explicitly here, are operated as valve closing members by energizing the magnet coils.

The block17surrounding the double magnet18is secured on a housing21of the pressure control valve arrangement7, which may be on the front side, and has a plug connection22for supplying power to the double magnet18. This housing21furthermore has a pressure medium connection23for supplying pressure to and/or relieving pressure from the pressure control valve arrangement7, and a working connection24for connection of the brake cylinder6(FIG. 3).

AsFIG. 2aandFIG. 2bshow, the pressure medium connection23is connected to the foot or service brake valve9of the fluid-pressure-actuated braking device by the brake pressure line8and is supplied with air or vented in accordance with an actuation of the foot brake valve9.

As is apparent especially fromFIG. 3, the housing21is provided with at least one and, in this case, for example, two through holes20a,20bopening into both side faces19a,19bof the housing21, through which holes holding arrangements, e.g. screws, for holding the pressure control valve arrangement on a support, e.g. on a chassis of the vehicle, project. The center lines of the two through holes20a,20bmay be parallel to each other. The axial length of the through holes20a,20bapplies as a standardized installation dimension of the pressure control valve arrangement7and, for reasons of space, is fixed and invariable, defining the maximum permissible width B of the housing21.

One diaphragm valve14amay be arranged on the side of the housing21, and the other diaphragm valve14bmay be arranged on the bottom of the housing21, asFIG. 4shows. As a valve body, a diaphragm valve14a,14bof this kind has a diaphragm25a,25b, which can be acted upon by introducing pressure medium into a control chamber26a,26b, each of which is covered on the outside of the housing by a cover27a,27bproduced by a primary forming process, such as injection molding, which is secured on the housing21. In this arrangement, the control chamber26a,26bis formed between the diaphragm25a,25band the cover27a,27b.

As is apparent especially fromFIG. 4, the cover27aclosing the control chamber26aof the diaphragm valve14aarranged on the side has a projection or spigot28which projects from the outside into an aperture29of a pressure medium channel30in the housing. A pressure medium guiding surface31for directing the flow of the pressure medium carried in the pressure medium channel30is formed on the projection28.

The pressure medium channel30may be intended to bring about deflection of the flow of the pressure medium from an upstream part of the pressure medium channel30, which leads in one direction, into a downstream part of the pressure medium channel30, which leads in another direction.

In the exemplary embodiment, for example, the pressure medium channel30brings about a 90-degree deflection of the flow of the pressure medium from a first section32of the pressure medium channel30, the section being vertical inFIG. 4and having a flow connection to a valve seat of the diaphragm valve14aacting as an outlet valve, the control chamber26aof which is covered by the cover27a,into a section33of the pressure medium channel30, the section being horizontal inFIG. 4and having a flow connection to a vent connection (not explicitly visible here) formed on the housing21, as the arrow34inFIG. 4symbolizing the direction of flow illustrates.

As seen from the interior of the housing21, the horizontal section33of the pressure medium channel is extended as far as the aperture29in the side face19aof the housing21. The projection28of the cover27aprojects into this aperture29in the manner of a spigot.

In the present case, the pressure medium channel30therefore may be a vent channel, which carries compressed air from the working connection24, which is connected to a brake cylinder, via the outlet valve embodied as a diaphragm valve14a, to a vent of the pressure control valve arrangement7.

The pressure medium guiding surface31of the projection28is designed to deflect the flow of the pressure medium from one direction (in this case the vertical direction) to the other (in this case the horizontal direction) or to assist such a deflection, which may be by a spherical surface.

In a particular embodiment, the cover27aprovided with the projection28and the pressure medium guiding surface31is designed as an integral injection molding made of plastic or metal.

In a particular embodiment, the central area of the cover27aserves to cover the control chamber26a, and the projection28having the pressure medium guiding surface31is formed at the edge of the cover27a, e.g. on a nose35of the cover27a, as illustrated byFIG. 3. A corresponding seal36in the region of the aperture29ensures that the pressure medium channel30is sealed off from the outside.

A cover27ahaving a projection28and a pressure medium guiding surface31is not necessarily restricted to use for a pressure medium channel30having a 90-degree deflection of the direction of flow. On the contrary, such a cover27acan be used for any kind of pressure medium channel30, especially for those without flow deflection, in which a reduction in the flow resistance can be achieved by a pressure medium guiding surface.

LIST OF REFERENCE SIGNS