US 4,072,014 A · Control means for a two stage servomotor

Abstract

The control valve for a two stage servomotor used in a braking system. A two stage servomotor has a housing with a stepped bore therein for retaining a piston and a cylindrical body. A deformable member adjacent the cylindrical body transmits a first operational input into the piston. A first operational input moves the piston and produces a pressure signal. The first operational input and the resistance to movement by the piston changes the shape of the deformable member. The changes in the shape of deformable member moves the control valve and allows the pressure signal to be communicated to the cylindrical body. The pressure signal acting on the cylindrical body provides an additional second operational force for moving the piston.

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Claims16

Dependent claims

In a two stage servomotor for energizing the wheel brakes of a vehicle in a first stage with a fluid pressure created by moving a piston means in a pressurizing chamber of an actuator bore by a first input force and in a second stage by moving said piston means in the pressurizing chamber through a combined forced of a second input force and pressure force created by the fluid pressure acting on the piston means in an input chamber, actuation means for shifting the operation of said two stages servomotor from said first stage to said second stage, comprising:

cylindrical means associated with said piston means in said actuator bore for establishing said input chamber and a reservoir chamber, said cylindrical means having a passageway for connecting said input chamber with said pressurizing chamber and said reservoir chamber, said cylindrical means being responsive to said first and second input forces;
deformable means for transmitting said first and second input forces from the cylindrical means to said piston means, said first and second input forces and the fluid pressure in the pressurizing chamber causing said deformable means to change shape;
and
valve means located in said bore and responsive to said change in shape of said deformable means for preventing fluid communication through said passageway from said pressurizing chamber to said reservoir chamber and said input chamber while allowing fluid to be communicated from said reservoir chamber to said input chamber in said first stage of operation and for preventing fluid communication from said reservoir chamber to said pressurizing chamber and said input chamber when said fluid pressure in the pressurizing chamber reaches a predetermined value and thereafter allows fluid communication between said pressurizing and input chambers to initiate said second stage of operation, said fluid pressure communicated to said input chamber acting on a portion of said cylindrical means which in turn abuts the piston means to aid in the movement thereof.

1 more element

In a two stage servomotor for energizing the wheel brakes of a vehicle in a first stage of operation with a first pressure signal created from a first input force developed through the movement of a wall means, means for combining an additive input force with a second input force to create a second pressure signal in a second stage of operation, said combining means comprising:

a housing having a bore therein with a first section and a second section, said housing having a first port and a second port for connecting said first and second sections with a reservoir;
piston means located in said first section of said bore for establishing a pressurizing chamber, said piston means having a control chamber located therein, said piston means having a first passageway for connecting the control chamber with the pressurizing chamber, a second passageway and a third passageway in said piston means;
cylindrical means fixed to said wall means and located in said second section in said bore to establish a reservoir chamber and an input chamber, said input chamber being connected to said control chamber through said second passageway, said reservoir chamber being connected to said control chamber through said third passageway;
deformable means located in said bore for transmitting the first and second input forces from the cylindrical means to move said piston means in said pressurizing chamber past said first port and create said first and second pressure signals, said first and second input forces and first and second pressure signals causing said deformable means to change shape;
and
valve means connected to said control chamber and responsive to said change in shape of said deformable means for preventing communication through the first passageway from said pressurizing chamber to said reservoir and input chambers in the first stage of operation while allowing communication between the reservoir chamber and the input chamber through the control chamber and for preventing communication through the third passageway from the reservoir chamber to said input and pressurizing chambers when the first pressure signal in the first stage of operation reaches a predetermined value to allow communication of fluid between the pressurizing chamber and the input chamber through the control chamber, said fluid communicated to said input chamber acting on the cylinder means which in turn abuts the piston means to develop said additive input force.

3 more elements

In a two stage servomotor for energizing the wheel brakes of a vehicle with an operational fluid pressure created by moving a piston means in a pressurizing chamber of a bore by a first input force in a first mode of operation and in a second mode of operation by moving the piston means by combining the forces of a second input force and a force created by the operational fluid pressure acting on a portion of the piston means in an input chamber, actuation means for shifting the operation of the two stage servomotor from the first mode to the second mode comprising:

cylindrical means located in said bore defining a reservoir chamber and an input chamber having a first passage for connecting the fluid reservoir chamber to a control chamber defined in said piston means, a second passage in said piston means for connecting the control chamber to the pressurizing chamber and a third passage in said cylinder means for connecting the control chamber to the input chamber;
deformable means for transmitting said first and second input forces to said piston means, said first and second input forces and the operational fluid pressure in the pressurizing chamber causing said deformable means to change shape;
and
valve means located in said control chamber and responsive to said change in shape of said deformable means for preventing communication from said pressurizing chamber to said reservoir chamber and said input chamber through said second passage while allowing communication from the reservior chamber to the input chamber through said first and third passages in said first mode of operation and in said second mode of operation preventing fluid communication from the reservoir chamber through said first passage to said pressurizing chamber and said input chamber when the fluid pressure in the outlet chamber reaches a predetermined value and thereafter allow fluid communication from the pressurizing chamber to the input chamber through the second and third passages, said fluid communicated from the pressurizing chamber to the input chamber acting on a portion of the cylindrical means which in turn abuts the piston means to aid in the movement thereof.

1 more element

Dependencies are inferred from the claim text.

Description2,936 words

Summary853 words

#In U.S. Pat. No. 3,559,406, incorporated herein by reference, I disclosed a servomotor for a braking system having concentric pistons located in a pressurizing chamber for sequentially producing first and second operational braking forces. A pressure differential responsive wall in the servomotor moves the concentric pistons simultaneously until an optimum pressure differential develops within the servomotor. Thereafter, a manual input applied to the concentric pistons provides an additional pressurization force for moving the pistons in the pressurizing chamber. Unfortunately, the additional pressurizing forces acts on all the concentric pistons thereby reducing the effect of the manual input.

#Later, in U.S. Pat. No. 3,910,048, I disclosed a two stage servomotor having a locking means for holding an exterior concentric piston in a stationary position during a transfer of a manual operational input to an interior piston. A valve in the exterior piston allows fluid to flow to the back side of the exterior piston during the simultaneous movement of the concentric pistons. The manual input from the operator moves the interior piston away from the exterior piston and allows a spring to close a flow-through valve. With the flow-through valve closed, the fluid on the back side of the exterior piston resists expansion of the pressurizing chamber thereby essentially eliminating any loss of pressurization through the manual input.

#I have now devised a two stage servomotor having a control valve means for diverting a portion of the output of a piston means to a cylindrical means as a function of a change in shape of a reaction means. The piston means is located in a first bore to establish a first chamber. The reaction means is located between a cylindrical means and the piston means. The cylindrical means is located in a larger second bore to establish a reservoir chamber and a second chamber. A sleeve actuator means is held against the reaction means by a first resilient means. The sleeve actuator means has a first passageway which connects the first pressurizing chamber with a control chamber. The control chamber is connected to the second chamber through a second passageway and to the reservoir chamber through a third passageway in the piston means. A poppet valve is held against a shoulder on the sleeve actuator means by a second resilient means to prevent communication through the first passageway in a first stage of operation.

Brief description of the drawings3 figures

#FIG. 1 is a schematic illustration of a braking system having a two stage servomotor made according to the teachings of my invention;

#FIG. 2 is a sectional view of the reaction means of the two stage servomotor of FIG. 1 illustrating the relationship between the piston means, input means and the valve actuator means during a first mode of operation; and

#FIG. 3 is a sectional view of the reaction means of FIG. 2 illustrating a second mode of operation.

Detailed description2,002 words

#The braking system 10 shown in FIG. 1 has a two stage servomotor 12 connected to a master cylinder 14 which supplies the front wheel brakes 16 and the rear wheel brakes 18 with an operational braking force in response to an input force applied to pedal 20 by an operator.

#The two stage servomotor 12 has a front shell 22 joined to a rear shell 24 by a bayonet type twist lock arrangement 26. A diaphragm 28 has a first bead 30, held between the front shell 22 and the rear shell 24 by the twist lock arrangement 26, and a second bead 32 located in groove 34 of a hub means 36. The bead 32 of the diaphragm 28 holds a support plate 38 against shoulder 40 of the hub means 36. The diaphragm 28 and the backing plate 38 form the wall means 44 which separates the interior of the two stage servomotor 12 into a first variable volume chamber 42 and a second variable volume chamber 46.

#The hub means 36 has a rearwardly extending projection 48 which is carried by a bearing seal 50 located in axial opening 52 of the rear shell 24. The hub means 36 has a stepped axial bore 54 in which a control valve means 56 is located.

Control means for a two stage servomotor

Life of this patent

Control means for a two stage servomotor

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims16

Description2,936 words

Drawings

Classification2 codes

Life of this patent

Description2,936 words