GB2063998A

GB2063998A - I.C. Engine Exhaust Brake for Motor Vehicles

Info

Publication number: GB2063998A
Application number: GB8036822A
Authority: GB
Original assignee: Daimler Benz AG
Current assignee: Daimler Benz AG
Priority date: 1979-11-20
Filing date: 1980-11-17
Publication date: 1981-06-10
Also published as: FR2470250B1; DE2946747C2; DE2946747A1; GB2063998B; FR2470250A1

Abstract

A pressure relief valve 6 is provided to divert exhaust gases round the angularly adjustable brake valve plate 4, when this is closed and greater than a predetermined pressure prevails upstream of the plate 4. The valve 6 has a valve disc 8 which forms part of the wall of the exhaust pipe. The disc 8 is responsive to the pressure upstream of the plate 4 to open against the bias of a spring (12), Fig. 1 (not shown). A bore (20), Fig. 3 (not shown), in the disc 8 may form a bearing for a journal (19) on the plate 4. <IMAGE>

Description

SPECIFICATION Engine Brake for Motor Vehicles The invention relates to an engine brake for motor vehicles having an internal combustion engine with an exhaust pipe, the brake including a brake flap arranged in the exhaust pipe, so as to be moveable to a closed position, a pressure relief valve being provided in the region of the brake flap and being adapted to open and divert exhaust gases round the brake flap in the presence of a predetermined excess pressure upstream of the closed brake flap.

An engine brake with a pressure relief valve of this type is known from German Auslegeschrift 1,555,833. In this construction the pressure relief valve is arranged axially to the pivot axis of a pivotabie brake flap in the prolongation of the latter so that it lies beneath a brake flap bearing block provided in the lower part of the brake housing. Here, before the pressure of the exhaust gases, impounded by the brake flap when this occupies the closed position, attains a level which causes the discharge valve to be forced open, the exhaust gases flow through flow channels arranged in the brake housing of the brake flap, through a space beneath the bearing block and through return channels in the brake housing, finally into the part of the exhaust pipe leading into the atmosphere.

The underlying aim of the invention is to produce an engine brake with a pressure relief valve of the type initially mentioned, which besides an extremely simple and compact construction also permits short flow paths for bypassing the brake flap. Durable and reliable operation of the engine brake should also be ensured.

According to the invention there is provided an engine brake for motor vehicles, having an internal combustion engine with an exhaust pipe, the brake including a brake flap arranged in the exhaust pipe so as to be movable to a closed position a pressure relief valve being provided in the region of the brake flap and being adapted to open to divert exhaust gases round the brake flap in the presence of a predetermined excess pressure upstream of the closed brake flap, wherein the pressure relief valve forms a wall part of the exhaust pipe.

With a wall part of this type, which can be forced away from the closed brake flap by a specific positive pressure, by-passing of the brake flap is achieved in the simplest manner.

In the previously known engine brake described initially, structurally more onerous measures for the diversion of the impounded exhaust gases are adopted, which result from the arrangement of the channels provided in the brake housing upstream and downstream of the brake flap. Another disadvantage of this construction is that part of the exhaust gases also enters the channels when the brake flap is open and may cause increasing constriction of the channels by deposits of foreign bodies.

In a preferred embodiment of the invention the pressure relief valve includes a valve closure member having a valve stem and a valve disc, the surface of the valve disc simultaneously forming the wall partof the exhaust pipe.

With a view to easy assembly the part of the exhaust pipe housing the brake flap may be constructed as a brake housing with a cylindrical recess and the valve disc of the pressure relief valve is arranged to move longitudinally in this recess. A simple mounting for the pressure relief valve may be obtained by providing a bearing part attached to the brake housing, in which the valve stem of the pressure relief valve is guided for longitudinal sliding.

The cylindrical recess may be of stepped construction in the region of the brake flap and may provide a valve seat for the pressure relief valve. Preferably, a chamber between the valve disc and the bearing part is connected by a vent hole to a part of the exhaust pipe vented to atmosphere.

The invention will now be described, by way of example, with reference to the accompanying drawing, wherein: Fig. 1 shows a brake housing installed in an exhaust pipe of the internal combustion engine with a simply mounted open brake flap and closed pressure relief valve in section, Fig. 2 shows the brake housing according to Fig. 1, but with closed brake flap and open pressure relief valve in section and Fig. 3 shows the brake housing with a modified mounting of the brake flap, in section.

An engine brake 1 provided for motor vehicles having an internal combustion engine with an exhaust pipe, has, in a specific part of the exhaust pipe 2, shown in Fig. 1, a brake housing 3. A pivotable brake flap 4 unilaterally mounted on a single journal and a pressure relief valve 6 arranged coaxially to the bearing axis 5 of this brake flap 4 are arranged in the housing. The valve 6 has a valve closure member having a valve disc 8 with a plane bottom surface 7, and a valve stem 9.

The valve disc 8 of the pressure relief valve 6 is located in a cylindrical recess 10 the axis of which is oriented transversely tothe axis of the exhaust pipe 2 in the brake housing 3, whilst the valve stem 9 is guided for longitudinal sliding along the axis of the recess counter to the pressure of a spring 12 in a bearing part 11 firmly connected to the brake housing 3 and partly in the cylindrical recess 10.

The cylindrical recess 10 is of stepped construction at a point 13, to form an annular shoulder which serves as a valve seat for the pressure relief valve 6.

A supporting part 15 of pot-like construction abuts against the valve stem end 14 of the pressure relief valve 6 and has an annular valve seat which receives the spring 12. The valve 6 is thus biassed onto its valve seat 13 by virtue of the pretensioned spring 12. The spring 12 is braced against a cap 16 firmly connected to the bearing part 11.

The engine brake is illustrated in the inoperative position in Fig. 1. The brake flap 4 adapted to the cross-section of the exhaust pipe is fully open, whilst the pressure relief valve 6 is closed. In this closed position of the valve the valve disc 8 forms with its bottom surface 7 a wall part of the brake housing 3, past which the exhaust gases flow.

In the position of the engine brake illustrated in Fig. 2, the brake flap 4 occupies the closed position, i.e. transverse to the flow direction of the exhaust gases to thereby prevent the flow of exhaust gas through the exhaust pipe. As soon as inadmissibly high pressures occur upstream of the brake flap 4, the spring-loaded pressure relief valve 6 or discharge valve opens automatically and part of the exhaust gases (designated by arrows) is diverted round the brake flap 4.

A vent hole 18 connects the chamber 17 located behind the valve disc 8 to the part of the exhaust pipe 2 located downstream of the brake flap 4 which is vented to atmosphere, in order to vent the chamber 17.

The embodiment according to Fig. 3 shows a double mounting of the brake flap 4. Here a lower journal 19 of the brake flap 4 is guided in a housing bore 20 in the valve disc 8 of the pressure relief valve 6, whereas in the embodiment af Figures 1 and 2, the flap 4 is supported on one journal only.

The engine brake with the pressure relief valve may also be provided in twin-flow exhaust pipes if desired. The construction according to the invention is moreover also suitable for exhaust pipes of supercharged or turbo-charged internalcombustion engines.

Claims

1. An engine brake for motor vehicles, having an internal combustion engine with an exhaust pipe, the brake including a brake flap arranged in the exhaust pipe so as to be movable to a closed position a pressure relief valve being provided in the region of the brake flap and being adapted to open to divert exhaust gases round the brake flap in the presence of a predetermined excess pressure upstream of the closed brake flap, wherein the pressure relief valve forms a wall part of the exhaust pipe.

2. An engine brake according to Claim 1, wherein the pressure relief valve includes a valve closure member having a valve stem and a valve disc, the surface of the valve disc simultaneously forming the wall part of the exhaust pipe.

3. An engine brake according to Claim 2, wherein the part of the exhaust pipe housing the brake flap is constructed as a brake housing with a cylindrical recess and the valve disc of the pressure relief valve is arranged to move longitudinally in this recess.

4. An engine brake according to Claim 3, wherein a bearing part attached to the brake housing is provided in which the valve stem of the pressure relief valve is guided for longitudinal sliding.

5. An engine brake according to Claim 3 or 4, wherein the cylindrical recess is of stepped construction in the region of the brake flap and provides a valve seat for the pressure relief valve.

6. An engine brake according to Claim 4 or 5 when dependent thereon wherein a chamber between the valve disc and the bearing part is connected by a vent hole to a part of the exhaust pipe vented to atmosphere.

7. An engine brake for motor vehicles substantially as described herein with reference to, and as illustrated in, the accompanying drawings.