DE8805352U1 - Load-dependent brake force regulator - Google Patents

Description

R. 21776 30.3.1988 Ee/Hl

ROBERT BOSCH GMBH, 7000 Stuttgart 1 Load-dependent brake force regulator

The invention is based on a load-dependent brake force regulator according to the type of the main claim.

Such a brake force regulator is known (DE-PS 23 15 84). Depending on the load of the vehicle, this controls a more or less reduced brake pressure in the wheel brake cylinders, whereby a keg signal corresponding to the deflection of the Hagen spring is fed to the brake force regulator.

Such brake force regulators should be installed on the front axle, particularly on trailers, in order to avoid the need for complex pipework. However, installing such brake force regulators on the front axle is problematic in that the front axle is exposed to a greater degree than the rear axle when the vehicle is decelerating due to dynamic axle load shifts. The strong pitching movements of the front axle triggered by this cause an increased hedging signal and thus an adjustment of the brake force regulator, which results in progressive deceleration.

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Arrangements have already been made to eliminate these disadvantages. German patent application 12 87 960, for example, discloses a device on a control valve in which a support sleeve, adjustable by the master pressure , is provided with locking teeth on its outer circumference, into which correspondingly toothed, radially movable segments engage, the radial displacement of which can be blocked by driving over the segments using a sleeve, so that in the event of a dynamic change in the axle load, the resulting increased master pressure cannot move the support sleeve any further axially. This device has the disadvantage that the teeth make stepless adjustment impossible. There is also the risk that the locking segments

! get into a "tooth-tooth" position with the supporting member, in which

.' the locking sleeve no longer moves over the segments when the piston is loaded.

component and the locking device is blocked.

The invention is based on the object of creating simple and reliable means that enable the actuator to be held in place during braking and a continuous load-dependent adjustment of the actuator in the unbraked state.

This object is solved according to the invention by the characterizing features of the main claim.

An embodiment is shown in the drawing and explained in more detail in the following description.

Xm upper part of a housing 1, a stepped piston 2, 3 is arranged in a movable and sealed manner, which has an inlet valve seat 4 and a spring-loaded double valve body 5 in its interior. A number of radial sipes 6 are connected to the stepped piston 2, 3, the end face of which facing the membrane 3 of the stepped piston 2/3 forms parts of a conical shell. In the

i| a number of radial ribs 7 are also provided, which

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and in the spaces between which the ribs 6 engage without contact and whose end faces facing the membrane Z form parts of an opposing conical shell. In the position shown in the drawing, the membrane 3 rests against these latter end faces.

The membrane 3 is attached with its outer edge to the housing 1, while its inner edge is attached to the piston 2, 3. In this way, a stepped piston is formed, the effective area of which is fixed in chamber I, but variable in chamber III.

An actuator 9 is guided in a central bore of the housing i, the upper face of which forms an outlet valve seat 10 and the cavity of which is vented via a chamber II and a check valve 12. The actuator 9 is connected in a force-locking manner to the free end of a lever 13, which can execute angular deflections that are proportional to the vehicle load.

Compressed air supplied by a brake valve (not shown) enters chamber I via a connection 14. Chamber II is connected to the atmosphere. Wheel brake cylinders (not shown) are connected via connection 16 of chamber III.

In the middle part of the housing 1 there is a sliding*

1 and the actuator piston 19 is arranged in a sealed manner on the actuator 9.

net, which can be acted upon by the brake pressure being applied or released. |

The actuating piston 19 has an inner conical surface 20 with which it can be used for a § Outer conical surface 21 of a clamping ring 22. The clamping j

ring 22 is designed as a hollow cone and is longitudinally |

slots and surrounds the actuator 9 with a cylindrical inner 1:

surface 23 except for the Shiita completely. With its base lies |

it is attached to a housing wall 24. !■

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The operation of the Bz'emskfaftregler according to the invention is as follows

The compressed air supplied to connection 14 from the brake valve during brake actuation pressurizes part 2 of the stepped piston 2, 3 and moves it downwards until the double valve body 5 closes the outlet valve and opens the inlet valve, so that the compressed air can flow to the wheel brake cylinders via connection 16. When part 2 of the stepped piston 2, 3 moves downwards, the membrane 3 is pressed by the

Q The front surfaces of the ribs 7 are raised by the front surfaces of the ribs 6, so that the effective area of the diaphragm piston 3 is increased. An air pressure is established in chamber III, the level of which is related to that in chamber I as the effective area of the part 2 of the stepped piston 2, 3 is related to the current effective area of the diaphragm 3. The ratio of these effective areas is influenced by the position of the exhaust valve seat 10 on the actuator 9. The lower the axle load of the vehicle, the further the lever 13 is turned clockwise and in this way determines the position of the exhaust valve seat 10 and thus also the position of the stepped piston 2, 3, whereby the effective area of the diaphragm 3 is automatically predetermined and proportional to the vehicle load.

V/ In order to prevent further displacement of the actuator 9 during the braking process due to the increased pitching movement occurring as a result of the dynamic axle load shift, the locking element consisting of the clamping ring 22 and the inner conical surface 20 of the actuating piston, the structure of which has already been described, becomes effective. At the same time as the wheel brake cylinders are acted upon, the actuating piston 19 of the locking element 20/21 is acted upon by the brake pressure, and the inner diameter of the clamping ring 22 is reduced by pressure on its outer conical surface 21 until the clamping ring 22 clamps the actuator 9. Then further displacement of the actuator 9 is prevented. This prevents undesired loading of the wheel brake cylinders.

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brake cylinder with a brake pressure other than that corresponding to the actual axle load, especially at the start of the braking process, switched off.

When the brake valve is released, chamber I is vented and piston 2, 3 is pushed upwards/ whereby the inlet valve closes and the outlet valve opens* In this way, piston 19 is also relieved of the brake pressure and the locking of actuator 9 is released»

Claims (2)

R.21776
30.3.1988 He/Wl ROBERT BOSCH GMBH, 7000 Stuttgart 1 Expectations L Load-dependent brake force regulator for a compressed air brake system for vehicles, in particular trucks and truck trailers, which influences the wheel brake cylinder pressure by means of a stepped piston and an inlet and outlet valve, the inlet valve seat of which is arranged in the stepped piston and the outlet valve seat of which is displaceable depending on the load, wherein a constant effective area of the stepped piston is acted upon by the brake valve pressure and a variable effective area in the form of a rolling membrane in the opposite direction is acted upon by the wheel brake cylinder pressure, and wherein the actuator having the outlet valve seat and displaceable in its longitudinal axis is continuously adjustable depending on the loading state and can be locked by means of a pressure-loaded locking member, characterized in that the locking member is formed by a part (inner cone surface 20) of an actuating piston (19) acted upon by the brake pressure controlled in or out and a clamping ring (20) arranged concentrically to the actuating piston (19), which acts as longitudinally slotted hollow cone with a cylindrical inner surface almost completely enclosing the actuator (9), and that the clamping ring (22) can be reduced in size by applying pressure to its outer conical surface (21) with narrowing of the slot in the inner diameter. 2. Brake force regulator according to claim 1, characterized in that the outer conical surface (21) of the clamping ring (22) is opposed by an inner conical surface (20) of the axially movable actuating piston (19) as a pressure piece. I I .1 I . I Il * I · &bull; ti ii &bgr;