DE102014006899A1 - Hydraulic transmission element - Google Patents

Abstract

The invention relates to a hydraulic transmission element (10) comprising a piston (14) axially movably mounted in a housing (12) with a first piston surface (16) and an axially opposite second piston surface (18), the first piston surface (16) first active surface (16-1) and a second active surface (16-2) arranged in series therewith, wherein the first active surface (16-1) is filled with hydraulic fluid first pressure chamber (20) and the second active surface (16-2 ) define a filled with a hydraulic fluid second pressure chamber (22), wherein the first and second pressure chambers (20, 22) via means are interconnected such that only after exceeding a predetermined pressure level in the first pressure chamber (20) and / or after a predetermined travel of the piston (14), the first and second pressure chambers (20, 22) communicate hydraulically with each other.

Description

The invention relates to a hydraulic transmission element according to claim 1.

With the aid of hydraulic systems, movements are often carried out, which are first characterized by a high path and then by a high force.

An example of this are conventional hydraulic brake systems of a motor vehicle, in which first overcome the clearance and then high forces are applied to generate sufficient friction effect. However, the hydraulic ratio between brake pedal and piston movement in the calipers is linear.

In the case of the brake system overcoming the air gap is perceived as dead time, which leads to a poor pedal feel and increased braking distances. However, the pedal ratio must be chosen so that even if a brake circuit or the brake assist, the driver can still generate the necessary force.

The invention has for its object to provide a hydraulic transmission element that when pressurized initially allows a quick piston movement and then a piston movement with high force.

This object is solved by the features of claim 1.

The dependent claims form advantageous developments of the invention.

According to the invention, the hydraulic transmission element comprises a housing axially movably mounted in a piston having a first piston surface and an axially opposite second piston surface. In this case, the first piston surface is designed such that it has a first active surface and a second active surface arranged in series therewith. In addition, the piston is arranged and guided in the housing such that the housing and the first active surface define a hydraulic fluid-filled first pressure chamber and the housing and the second active surface define a hydraulic fluid-filled second pressure chamber. Furthermore, the first and the second pressure chamber are connected to each other via means such that only after exceeding a predetermined pressure level in the first pressure chamber and / or after a predetermined travel of the piston, the first and second pressure chambers communicate hydraulically with each other.

The inventive design is now advantageously ensured that at a pressure increase in the first pressure chamber initially only the first effective area of the piston is exposed to the hydraulic pressure. This results in a fast piston movement with little force. Since upon reaching the predetermined pressure level in the first pressure chamber and / or reaching a predetermined Kolbenverfahrposition the two pressure chamber communicate hydraulically with each other via means, now both active surfaces are exposed to the hydraulic pressure, with the result that the piston moves slower, but with high force ,

Preferably, the two pressure chambers are connected to each other via hydraulic lines, in which a valve, in particular a pressure relief valve or an actively switchable valve, is arranged.

Particularly preferably, both pressure chambers are communicatively connected to one another via at least one bore introduced into the housing, in which a spring-loaded valve piston is arranged. The communicating connection of the two pressure chamber by means of a bore introduced in the housing has the advantage that a compact design is ensured.

According to a first embodiment, the hydraulic transmission element is integrated in a tandem master cylinder:
In known manner, the tandem master cylinder comprises a filled with hydraulic fluid brake cylinder housing in which a standing in operative connection with a brake pedal actuating piston and a floating piston are guided axially movable. Here, the piston of the hydraulic transmission element is viewed in the axial direction between the actuating piston and the floating piston in the brake cylinder housing and guided in the brake cylinder housing, that the first pressure chamber between piston action surface of the actuating piston, brake cylinder housing and first effective surface of the piston of the hydraulic transmission element is formed, while the second Pressure chamber between the brake cylinder housing and the second effective surface of the piston of the hydraulic transmission element is formed.

The brake cylinder with integrated hydraulic transmission element proves to be particularly advantageous because the caused by a brake pedal pressure increase in the first pressure chamber initially leads to a rapid piston movement, so that the clearance is overcome quickly, and thus a fast response is guaranteed with "good pedal feel". Particularly advantageous is the positioning in the tandem master cylinder also because at one stroke all four brakes have this quick overcoming of the clearance.

According to a second embodiment, the hydraulic transmission element is integrated in a brake caliper:
In a known manner, the brake caliper comprises a caliper housing filled with hydraulic fluid, in which a brake caliper piston having a brake lining is guided axially movably. Here, the piston of the hydraulic transmission element replaces the standard caliper piston, wherein the second piston surface of the piston of the hydraulic transmission element is provided with the brake pad. In addition, the piston of the hydraulic transmission element is arranged and guided in the caliper housing such that the first pressure chamber between the caliper housing and the first active surface of the piston of the hydraulic transmission element and the second pressure chamber between the caliper housing and the second effective surface of the piston of the hydraulic transmission element are formed.

The inventive integration of the hydraulic transmission element in the caliper has the effect that when a brake pressure in the first chamber, d. H. an increase in pressure in the first chamber, due to the small first effective area a rapid piston movement occurs and thus the air gap between the brake disc and brake pad is overcome quickly and thus the perceived by the driver dead time response time is significantly reduced.

According to a third embodiment, the hydraulic transmission element is integrated in a hydraulic cylinder:
In a known manner, the hydraulic cylinder comprises a hydraulic cylinder housing, in which a hydraulic piston is guided axially movable. In addition, the hydraulic cylinder housing has a hydraulic connection.

According to the invention, the piston of the hydraulic transmission element replaces the hydraulic piston provided as standard. The piston is arranged and guided in the hydraulic cylinder housing in such a way that the first pressure chamber is formed between a region of the hydraulic cylinder having the hydraulic connection and the first active surface of the piston of the hydraulic transmission element and the second pressure chamber is formed between the hydraulic cylinder housing and second active surface of the piston of the hydraulic transmission element.

By integrating the hydraulic transmission element in the hydraulic cylinder is advantageously ensured that a targeted pressure and / or path-controlled transmission of the hydraulic cylinder is possible.

Further advantages, features and possible applications of the present invention will become apparent from the following description in conjunction with the embodiments illustrated in the drawings.

In the description, the claims, and the drawing, the terms and associated reference numerals used in the list of reference numerals below are used.

In the drawing:

1 a sectional view of a hydraulic transmission element;

2 a sectional view of a tandem master cylinder, in which a hydraulic transmission element according to the invention is integrated;

3 a section of the tandem master cylinder 2 wherein the two pressure chambers are communicatively connected to each other via bores;

4 a section of the tandem master cylinder 2 wherein the two pressure chambers are communicatively connected to each other via bores;

5 a caliper with integrated hydraulic transmission element in a sectional view, and

6 a hydraulic cylinder with integrated hydraulic transmission element in a sectional view

1 shows a total with the reference numeral 10 designated hydraulic transmission element. The hydraulic transmission element 10 includes a housing filled with hydraulic fluid 12 in which a piston 14 is guided axially movable. The piston 14 has a first piston surface 16 and an axially opposed second piston surface 18 on.

As 1 can be seen further, is the first piston surface 16 formed in two parts, namely with a first effective area 16-1 and a second active surface arranged in series therewith 16-2 , While the first effective area 16-1 and the case 12 a first pressure chamber 20 limit is through the second effective area 16-2 and the case 12 a second pressure chamber 22 Are defined.

In addition, the two pressure chambers 20 . 22 via hydraulic lines 24 communicating with each other. In the hydraulic lines 24 is a two-way valve 26 arranged over which the two pressure chambers 20 . 22 hydraulically communicable with each other are connectable and via the one connection between the second pressure chamber 22 and a hydraulic fluid reservoir 28 is separable.

In the present case, it is the valve 26 to a pressure-controlled valve, the only after reaching a predetermined pressure level in the first pressure chamber 20 opens and the two pressure chambers 20 . 22 connects to each other and the second pressure chamber 22 from the hydraulic fluid reservoir 28 separates

The operation of the hydraulic transmission element 10 is explained below:
The application of an actuating pressure in the first pressure chamber 20 leads to an increase in pressure in the first pressure chamber 20 and thus to a movement of the piston 14 in the case 12 , Due to the small size of the first effective area 16-1 the piston moves 14 doing fast, but with little power.

The movement of the piston 14 leads to a negative pressure in the second pressure chamber 24 , so that hydraulic fluid from the hydraulic fluid reservoir 28 in the second pressure chamber 22 continues to flow.

Upon reaching the predetermined pressure level in the first pressure chamber 20 , the valve turns off 26 ie the two pressure chambers 20 . 22 are hydraulically communicating with each other and the second pressure chamber 24 is from the hydraulic fluid reservoir 28 separated.

After switching the valve 26 is the first and second active surface leaps and bounds 16-1 . 16-2 exposed to the operating pressure. The consequence of this is that the movement of the piston 12 now slower, but with higher power.

2 shows a total with the reference numeral 100 designated tandem master cylinder, in which the hydraulic transmission element described above 10 is integrated.

In a known manner, the tandem master cylinder comprises 100 a filled with hydraulic fluid brake cylinder housing 112 in which an actuating piston operatively connected to a brake pedal 114 and a floating piston 116 are guided axially movable. The floating piston 116 divided the brake cylinder housing 112 in two separate brake cylinder pressure chambers to provide two separate brake circuits.

The piston 14 the hydraulic transmission element is - like 2 it can be seen - between the actuating piston 114 and floating piston 116 arranged such that the first pressure chamber 20 between brake cylinder housing 112 , Actuating piston 114 and first effective area 16-1 and the second pressure chamber 22 between brake cylinder housing 112 and second effective area 16-2 is trained.

The first effective area 16-1 facing piston surface of the actuating piston 114 is hereinafter referred to as piston action surface 114-1 designated.

The hydraulic connection of the two pressure chambers 20 . 22 is accordingly too 1 educated.

Moves the actuating piston 114 due to an operation of a - not shown here for reasons of clarity - brake pedal, so the pressure in the first pressure chamber increases 20 , When moving the piston 114 There is thus a transmission ratio i = (first effective area 16-1) / (piston effective area 114-1)

Because the first effective area 16-1 in comparison to the piston effect surface 114-1 is much smaller, the piston moves 14 with less force but significantly faster than the actuating piston 114 , Because of now in the second pressure chamber 22 occurring negative pressure hydraulic fluid flows from the hydraulic fluid reservoir 28 in the second pressure chamber 22 to.

Is now in the first pressure chamber 20 reaches the predetermined pressure level, the valve switches 26 ie the connection between the hydraulic fluid reservoir 28 as well as second pressure chamber 22 is separated and the two pressure chambers 20 . 22 with their associated active surfaces 16-1 and 16-2 be connected.

The translation jumps at this moment jumped to the value i = (first active area 16-1 + second active area 16-2) / (piston effective area 114-1)

If one now sets the area ratios of 2 At the bottom, the piston moves 14 just as fast and with the same force as the actuating piston 114 ,

In the 3 and 3 illustrated embodiments of the tandem master cylinder 100 with integrated hydraulic translation element 10 corresponds essentially and in function of in 2 illustrated embodiment.

Unlike the in 2 illustrated embodiment are according to 3 and 4 the first and second pressure chambers 20 . 22 however, in the brake cylinder housing 112 introduced holes 118 . 120 ( 3 ) or bore 122 ( 4 ).

According to 3 is the hydraulic fluid reservoir 28 to the brake cylinder housing 112 screwed on and stands with a spring-loaded valve piston 124 in active connection.

The spring element is present in the form of a helical spring. The bias of the spring element can be adjusted.

For the sake of completeness, it is pointed out that the in 3 shown holes 118 . 120 not both must be present; These are only shown in combination to explain the different possibilities of the control.

Should the hydraulic transmission element 10 be formed purely pressure-controlled, is only hole 120 required, for a purely path-controlled variant or a path-controlled and from a certain travel pressure-controlled variant is only bore 118 necessary. Analog is a purely weggesteuerte solution (without connection pressure relief valve to volume 20 ) or a variant in which the first pressure controlled and controlled away from a certain pressure, possible.

Below is the operation of the purely pressure-controlled Variant, ie bore 118 is open, bore 120 is not necessary for this:
A movement of the actuating piston 114 and the associated pressure increase in the first pressure chamber 20 conditionally a movement of the piston 14 , Due to the negative pressure in the second pressure chamber 22 Hydraulic fluid flows into the second pressure chamber 22 ,

Between actuating piston 114 and pistons 14 there is a translation ratio i = (first effective area 16-1) / (piston effective area 114-1)

At a further pressure increase in the first pressure chamber 20 becomes the spring-loaded valve piston 124 pushed down so that the second pressure chamber 22 from the hydraulic fluid reservoir 28 is separated and at the same time the two pressure chambers 20 . 22 get connected.

The translation jumps up: i = (first active area 16-1 + second active area 16-2) / (piston effective area 114-1)

The pressure drops again because of the actuating piston 114 is reset, the reverse process occurs.

The valve piston 124 closes the hole 120 and gives the connection of the second pressure chamber 22 to the hydraulic fluid reservoir 28 free. The retreating piston 12 presses the previously removed hydraulic fluid back into the memory 28 until the end position is reached.

It should be noted that instead of a reset of actuating piston 114 It is also conceivable that the force on the piston 14 subsides. For example, brake pads can wear, which increases the clearance. The pressure change point then turns to another relative position of the piston 14 relative to the actuating piston 114 one. The resulting difference volume in the hydraulic fluid is automatically the hydraulic fluid reservoir 28 taken.

According to 4 is the hydraulic fluid reservoir 28 in the brake cylinder housing 112 is integrated and that the valve piston 124 associated spring element is designed as a gas spring. In this embodiment, the gas pressure is to be adjusted precisely around the turnaround point, ie separating the second pressure chamber 22 from the hydraulic fluid reservoir 28 and connecting the two pressure chambers 20 . 22 , define. In addition, the gas volume must be large enough so that the pressure does not drop too much when changing the volume.

In 5 is a total with the reference number 200 designated caliper shown in the under 1 described hydraulic transmission element 10 is integrated.

In a known manner, the caliper comprises 200 a hydraulic fluid filled caliper housing 212 , Instead of a standard in the caliper housing 212 axially movably guided caliper piston, is - like 5 shows - the piston 14 the hydraulic transmission element 10 in the caliper housing 212 arranged.

The piston 14 is doing so in the caliper housing 212 arranged and guided that the piston 14 with its second piston surface 18 from the caliper housing 212 protrudes and between the first effective area 16-1 and caliper housing 212 the first pressure chamber 20 and between second effective area 16-2 and caliper housing 212 the second pressure chamber 22 is trained.

As 5 can be seen further, has the second piston surface 18 a brake pad 214 on.

The hydraulic connection of the two pressure chambers 20 . 22 is accordingly too 1 educated.

If there is now a brake pressure and then increases the pressure in the first pressure chamber 20 , this causes a fast movement of the piston 14 with little force. Due to the negative pressure in the second pressure chamber 22 Hydraulic fluid flows into the second pressure chamber 22 to.

Upon reaching a predetermined pressure level in the first pressure chamber 20 switches the valve 26 ie the second pressure chamber 22 is from the hydraulic fluid reservoir 28 separated and the two pressure chambers 20 . 22 is hydraulically communicating with each other.

6 shows a total with the reference numeral 300 designated hydraulic cylinder, in which the above-described hydraulic transmission element 10 is integrated.

In a known manner, the hydraulic cylinder comprises 300 a filled with hydraulic fluid, a hydraulic connection 310 having hydraulic cylinder housing 312 , As 6 can be seen further, instead of a standard in the hydraulic cylinder housing 312 axially movable guided hydraulic piston, the piston 14 the hydraulic transmission element 10 in the hydraulic cylinder housing 312 arranged.

Here is the piston 14 such in the hydraulic cylinder housing 312 arranged and guided that the first pressure chamber 20 between a hydraulic connection 310 having housing portion of the hydraulic cylinder housing 312 and first effective area 16-1 of the piston 14 the hydraulic transmission element 10 and the second pressure chamber 22 between hydraulic cylinder housing 312 and second effective area 16-2 of the piston 14 the hydraulic transmission element 10 are formed.

The hydraulic connection between the two pressure chambers 20 . 22 is accordingly too 1 educated.

The mode of action is corresponding to the under 1 already explained, ie that upon reaching a predetermined pressure level in the first pressure chamber 20 and switching the valve 26 , are the first and second active surface 16-1 . 16-2 abruptly exposed to the hydraulic pressure, with the result that a non-linear characteristic curve is provided.

LIST OF REFERENCE NUMBERS

10

Hydraulic transmission element

12

casing

14

piston

16

first piston surface

16-1

first effective area

16-2

second effective area

18

second piston surface

20

first pressure chamber

22

second pressure chamber

24

hydraulic line

26

Valve

28

Hydraulic fluid reservoir

100

Tandem master cylinder

112

Brake cylinder housing

114

actuating piston

114-1

Piston action area

116

floating piston

118

drilling

120

drilling

122

drilling

124

plunger

126

hydraulic lines

128

Pressure relief valve

200

caliper

212

Caliper housing

214

brake lining

300

hydraulic cylinders

310

hydraulic connection

312

Hydraulic cylinder housing

a

axial direction

Claims (8)

Hydraulic transmission element ( 10 ), comprising one in a housing ( 12 ) axially movably mounted piston ( 14 ) with a first piston surface ( 16 ) and an axially opposite second piston surface ( 18 ), wherein the first piston surface ( 16 ) a first effective area ( 16-1 ) and a second active surface arranged in series ( 16-2 ), wherein the first active surface ( 16-1 ) filled with hydraulic fluid first pressure chamber ( 20 ) and the second effective area ( 16-2 ) a filled with a hydraulic fluid second pressure chamber ( 22 ), the first and second pressure chambers ( 20 . 22 ) are connected to each other by means such that only after exceeding a predetermined pressure level in the first pressure chamber ( 20 ) and / or after a predetermined travel of the piston ( 14 ) the first and second pressure chambers ( 20 . 22 ) communicate with each other hydraulically. Hydraulic transmission element ( 10 ) according to claim 1, characterized in that the first and second pressure chambers ( 20 . 22 ) via hydraulic lines ( 24 ) communicating with each other in which a valve ( 26 ) is arranged. Hydraulic transmission element ( 10 ) according to claim 2, characterized in that it is in the valve ( 26 ) is a pressure relief valve. Hydraulic transmission element ( 10 ) according to claim 2, characterized in that it is in the valve ( 10 ) is an actively switchable valve. Hydraulic transmission element ( 10 ) according to claim 1, characterized in that the first and second pressure chambers ( 20 . 22 ) about at least one. in the housing ( 12 ) introduced bore ( 118 . 120 . 120 ) are communicatively connected to each other, in which a spring-loaded valve piston ( 124 ) is arranged. Tandem master cylinder ( 100 ) for a brake circuit of a motor vehicle, comprising a hydraulic fluid-filled brake cylinder housing ( 112 ), in which an actuating piston ( 114 ) and a floating piston ( 116 ) are guided axially movable, characterized in that in the brake cylinder housing ( 112 ) between the actuating piston ( 114 ) and the floating piston ( 116 ) a hydraulic transmission element ( 10 ) is integrated according to one of claims 1 to 5, wherein the piston ( 12 ) of the hydraulic transmission element ( 10 ) in the brake cylinder housing ( 112 ) is arranged and guided such that the first pressure chamber ( 20 ) between piston action surface ( 114-1 ) of the actuating piston ( 114 ), Brake cylinder housing ( 112 ) and first effective area ( 16-1 ) of the piston ( 14 ) of the hydraulic transmission element ( 10 ) and the second pressure chamber ( 22 ) between brake cylinder housing ( 112 ) and second effective area ( 16-2 ) of the piston ( 14 ) of the hydraulic transmission element ( 10 ) is trained. Caliper ( 200 ) for a brake circuit of a motor vehicle, comprising a filled with hydraulic fluid caliper housing ( 212 ), in which a brake pad ( 214 ) having caliper piston is axially movably guided, characterized in that in the caliper housing ( 212 ) a hydraulic transmission element ( 10 ) is integrated according to one of claims 1 to 5, wherein the piston ( 14 ) of the hydraulic transmission element ( 10 ) replaced the caliper piston, and the second piston surface ( 18 ) of the piston ( 14 ) of the hydraulic transmission element ( 10 ) with the brake pad ( 214 ), wherein the piston ( 14 ) of the hydraulic transmission element ( 10 ) in the caliper housing ( 212 ) is arranged and guided, that the first pressure chamber ( 20 ) between caliper housing ( 212 ) and first active area ( 16-1 ) of the piston ( 14 ) of the hydraulic transmission element ( 10 ) and the second pressure chamber ( 22 ) between caliper housing ( 212 ) and second effective area ( 22 ) of the piston ( 14 ) of the hydraulic transmission element ( 10 ) are formed. Hydraulic cylinder ( 300 ), comprising a hydraulic connection ( 310 ) filled with Hydraulikfuid hydraulic cylinder housing ( 312 ), in which a hydraulic piston is guided axially movable, characterized in that in the hydraulic cylinder housing ( 312 ) a hydraulic transmission element ( 10 ) is integrated according to one of claims 1 to 5, wherein the piston ( 14 ) of the hydraulic transmission element ( 10 ) replaced the hydraulic piston, the piston ( 14 ) of the hydraulic transmission element ( 10 ) in the hydraulic cylinder housing ( 312 ) is arranged and guided, that the first pressure chamber ( 20 ) between a housing having the hydraulic connection housing portion of the hydraulic cylinder housing ( 312 ) and first active area ( 16-1 ) of the piston ( 14 ) of the hydraulic transmission element ( 10 ) and the second pressure chamber ( 22 ) between hydraulic cylinder housing ( 312 ) and second effective area ( 16-2 ) of the piston ( 14 ) of the hydraulic transmission element ( 10 ) are formed.

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