DE2756405A1 - PNEUMATICALLY OPERATING BRAKE FORCE REDUCER - Google Patents

Description

/! 756405

Λ-

task

A brake reducer is to be created with a progressive one with a simple construction Dependency of the closing pressure on the Suspension of a vehicle axle can be achieved.

Advantages of the invention

The goal is with a brake reducer with the Features achieved according to the main claim. Only a small amount of construction work is required, and the brake force reducer works reliably without interference. The control part with the hydraulic piston and the housing with the pneumatic piston form a structural unit, hydraulic piston and pneumatic pistons are arranged coaxially and structurally it is of particular advantage if of the Pneumatic piston the outer ring piston on the housing

leads and delivers a guide cylinder for the central piston, which is attached to the hydraulic piston comes. The brake reducer is particularly compact if the central piston for receiving the spring is cup-shaped, so that the spring becomes one part

can be received inside the piston and

is supported on the housing via the open guide cylinder. According to the higher load on the vehicle, the shut-off pressure increases as the control pressure falls in the way you want.

drawing

An embodiment of the invention is in Drawing shown and explained in more detail in the following description. 1 shows a

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A schematic sectional view through the brake reducer, FIG. 2 a diagram of the pressure curve, the control pressure being plotted on the abscissa and the associated shut-off pressure in the brake reducer being plotted on the ordinate, and FIG. 3 the pressure curve between the input and the output on the brake reducer. The inlet pressure is plotted on the abscissa and the outlet pressure on the ordinate.

Description of the invention

A housing 1 of a control part 2 (hydraulic part) adjoins a housing 3 of a pneumatic part 4. The control part 2 has an inlet 5 for the fluid from a master cylinder, not shown, and an outlet 6, which is connected to a wheel brake cylinder, also not shown is. A hydraulic piston 7, which works together with a passage valve 8 and has a valve seat 9, is axially displaceable in it. A valve member 10 supported on the housing 1 penetrates the piston face.A guide part 11 is connected to the hydraulic piston 7, which is partially hollow and receives a spring 12 which is clamped between the guide part 11 and the valve member 10. The effective piston area is larger on the piston side 13, which is connected to the wheel brake cylinder, than that on the piston side 14, which faces the master brake cylinder. An opening 15 in the hollow area of the guide part 11 creates the connection to the valve seat 9.

In the housing 3 of the pneumatic part 4, two nested pneumatic pistons 16, 17 are accommodated, which are arranged coaxially to the hydraulic piston 7.

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The outer annular piston 18 is guided on the outside of the housing 3, and on the inside it is provided with a guide cylinder 19 for the central piston 20, which cooperates with its piston face with the guide part 11 of the hydraulic piston 7. The central piston 20 is Cup-shaped, one end of a spring 21 is supported on it, the other end on the housing and passes through the open guide cylinder. Between the annular piston 18 and the Housing 3 is clamped in a spring 22, which is made stronger in accordance with the areas. The guide cylinder 19 has an end stop 23 for resting on the housing 3 and an abutment 24 for a support surface 25 of the central piston 20. The springs 21,22 against overlying piston sides are under a control pressure which is supplied via an inlet 26 and comes from a modulator not shown, the delivers a proportionally decreasing control pressure when the rear axle of the vehicle is deflected.

Mode of action

If the rear axle of the vehicle has a large deflection, i.e. a heavy load, this is the one emitted by the modulator Control pressure low. In this case, the spring presses the abutment 24 of the annular piston 18 against the support surface 25 of the central piston 20, so that the forces Both springs 21, 22 come into effect via the contact of the pneumatic piston 17 on the guide part 11. Of the Valve seat 9 is lifted far away from valve member 10. Is now pressure medium from the master cylinder at the entrance introduced, it flows unhindered through the open port valve 8 to the outlet 6 and from there to the Wheel brake cylinders. The one building up at exit 6

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Pressure moves the control piston 7 to the right against the residual effect of the spring forces of the two springs 21, 22 until the valve seat 9 comes to rest on the valve member 10 and this lifts off the housing 1. In At this moment the connection from input 5 to output 6 is interrupted. As can be seen from the graph 2 results, one now has a shut-off pressure to the wheel brake cylinder of at a control pressure of 1 bar about 150 bar. If the control pressure at inlet 26 increases, so the effect of the two springs 21,22 on the guide part 11 is reduced and the valve member 10 separates the passage from input 5 to output β already at lower wheel brake cylinder pressures. At a control pressure of 2.3 bar there is only a shut-off pressure to the wheel brake cylinder of 40 bar. Now the stop 23 comes to rest on the housing 3 with the result that only the spring 21 of the central piston acts and this changes the characteristics for the closing force. A further increase in the control pressure leads to a ge lower decrease of the shut-off pressure to the Randbremszy lighter. At a control pressure of 6 bar, the valve member 10 blocks at a pressure of 10 bar.

The characteristic of the shut-off pressure curve therefore has a kink, so that braking behavior is achieved with which the regulations are met.

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Claims (8)

R. 4273
11/25/1977. RÜBERT BOSCH GMBH, 7000 STUTTGART 1 Expectations 1 / Pneumatically operated brake force reducer with a Control part for the pressure between the master brake cylinder and the wheel brake cylinder, characterized in that in the control part (2) a hydraulic piston (7) determining the opening of a passage valve (8) is provided one piston side (13) under the pressure of the wheel brake cylinder and its other piston side (14) under the The master cylinder is under pressure and can be adjusted axially by interlocking with one another connectable pneumatic pistons (16, 17), which are actuated on one side by a control pressure and on the other are loaded by springs (21,22). 2. Brake power reducer according to claim 1, characterized in that the control part (2) with the hydraulic piston (7) and the housing (3) with the pneumatic piston (16, 17) - 2 - 909825/0 39 U oBiGiNAL \ NSPBGTTED form a structural unit and hydraulic piston (7) and pneumatic piston (16, 17) are arranged coaxially. 3. Brake power reducer according to claim 1, characterized in that the through valve (8) is on Housing (1) of the control part (2) has a supportable valve member (10) and the hydraulic piston (7) the Valve seat (9) emits. 4 · Brake power reducer according to claim 1, characterized in that the pneumatic pistons (16, 17) consist of one on the housing (3) guided annular piston (18) and a central piston (20) which is guided on a guide cylinder (19) of the annular piston (18) and on Guide part (11) of the hydraulic piston (7) comes to rest. 5. Brake power reducer according to claim 1, characterized in that the annular piston (18) on the spring side has a stop (23) for a counter-stop fixed to the housing. 6. Brake power reducer according to claim 4, characterized in that the central piston (20) on the spring side has a support surface (25) for an abutment (24) on the annular piston (18). 909825/0394 ΙΊ 56405 7. Bremskraftmlnderer according to claim 1 and 4, characterized in that the central piston (20) for receiving the spring (21) is cup-shaped and this spring (21) over the open guide cylinder (19) as well as the concentric spring (22) for the annular piston (18) with one of its ends are supported on the housing (3). 8. Brake power reducer according to claim 1, characterized in that the strength of the springs (21,22), the piston surfaces and the pressure in the master cylinder are coordinated so that the pressure in the wheel brake cylinder increases with increasing control pressures first rapidly and then slowly falling 909825/0394