GB2055180A - Pedal mechanism for hydraulic brake systems - Google Patents
Pedal mechanism for hydraulic brake systems Download PDFInfo
- Publication number
- GB2055180A GB2055180A GB8024614A GB8024614A GB2055180A GB 2055180 A GB2055180 A GB 2055180A GB 8024614 A GB8024614 A GB 8024614A GB 8024614 A GB8024614 A GB 8024614A GB 2055180 A GB2055180 A GB 2055180A
- Authority
- GB
- United Kingdom
- Prior art keywords
- pedal
- master cylinder
- arm
- ratio
- lever
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T11/00—Transmitting braking action from initiating means to ultimate brake actuator without power assistance or drive or where such assistance or drive is irrelevant
- B60T11/04—Transmitting braking action from initiating means to ultimate brake actuator without power assistance or drive or where such assistance or drive is irrelevant transmitting mechanically
- B60T11/08—Transmitting braking action from initiating means to ultimate brake actuator without power assistance or drive or where such assistance or drive is irrelevant transmitting mechanically providing variable leverage
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T7/00—Brake-action initiating means
- B60T7/02—Brake-action initiating means for personal initiation
- B60T7/04—Brake-action initiating means for personal initiation foot actuated
- B60T7/06—Disposition of pedal
Landscapes
- Engineering & Computer Science (AREA)
- Transportation (AREA)
- Mechanical Engineering (AREA)
- Braking Elements And Transmission Devices (AREA)
Abstract
A pedal mechanism for actuating a master cylinder (M) of an hydraulic braking system comprises a pedal lever (G) with a fixed pivot (O) and to one end of which the braking effort (E) is applied, a bell crank lever (H) coupled to the master cylinder (M), and a link rod (K) interconnecting the pedal and bell crank levers for transmitting the braking effort (E) to the master cylinder and increasing the pedal ratio of the mechanism as the pedal lever (G) pivots under the action of the braking effort (E). <IMAGE>
Description
SPECIFICATION
Pedal mechanism for hydraulic brake systems
This invention relates to a hydraulic brake system, and more particularly to a pedal mechanism for such a system having a variable pedal ratio.
The pedal ratio of a pedal mechanism represents the mechanical advantage of the brake pedal lever; in other words, it is the ratio between the output effort at the push-rod of a master cylinder of the braking system, and the corresponding input impulse or human effort at the brake pedal.
In most known pedal mechanisms, the brake pedal actuating the master cylinder is assigned a fixed ratio which multiplies the input impulse or human effort at the brake pedal for conversion to an adequate hydraulic thrust at the master cylinder.
In the operation of an hydraulic brake system, the actuation of the master cylinder piston is initially intended to displace the fluid in the master cylinder to the wheel cylinders for taking up mechanical clearance; accordingly, during this stage of travel of the piston, a low pedal ratio would suffice. Once, however, such mechanical clearance is taken up, higher pressures in the master cylinder are necessitated in the next stage during further travel of the piston or human effort at the brake pedal. It is to reduce such impulse or effort at the brake pedal to comfortable levels, that a correspondingly higher pedal ratio is desirable.
According to the present invention there is provided a pedal mechanism for an hydraulic braking system, comprising a pedal lever pivotable about a fixed axis and including a first arm to which a braking effort is applied in use of the mechanism and a second arm, a bell crank lever pivotable about a fixed axis and having a first arm for actuating a master cylinder of the braking system and a second arm, and a member interconnecting and pivoted to the second arms of the pedal and bell crank levers whereby, in use, applying a braking effort to the first arm of the pedal lever causes actuation of the master cylinder, and the pedal ratio of the mechanism increases with the pivoting of the pedal lever under the action of the applied effort.
With such a pedal mechanism an appropriate variable pedal ratio is obtainable that is to say, a low pedal ratio which is sufficient for the purpose of the initial travel of the master cylinder piston and corresponding low pressure demand in the master cylinder; and a succeeding, progressively increasing pedal ratio during the further travel of the piston to correspond to the progressively increasing pressure demand in the master cylinder, whereby the input impulse or human effort at the brake pedal is maintained at comfortable levels throughout the brake operation, i.e., not only during the initial travel of the piston in the master cylinder when the pressure demand therein is low, but also during the further travel of the piston when the pressure demand rises appreciably.Another advantage is that higher deceleration levels can be achieved and, furthermore, friction linings having a low coefficient of friction may be used without detracting from the overall performance of the braking system.
A better understanding of the invention will be had from the following detailed description which is given with reference to the accompanying drawings in which: Figure 1 schematically illustrates one possible pedal mechanism embodying the invention;
Figure 2 schematically illustrates another pedal mechanism embodying the invention;
Figure 3 schematically illustrates a slightly modified form of the pedal mechanism of Figure 1, and shows the different positions during brake operation;
Figure 4 is a graph showing master cylinder piston travel T plotted against the pedal ratio R, for braking systems having pedal mechanisms with a fixed pedal ratio and a variable pedal ratio according to the invention;
Figure 5 is a graph showing the master cylinder piston travel T plotted against the hydraulic pressure Y within the master cylinder;;
Figure 6 is a graph showing the pedal travel S plotted against the hydraulic pressure Y within the master cylinder for a braking system having a pedal mechanism with a fixed pedal ratio; and
Figure 7 is a graph showing the pedal travel S plotted against the hydraulic pressure Y within the master cylinder for a braking system having a pedal mechanism according to the invention.
In the pedal mechanism illustrated in Figure 1 a master cylinder M will be actuated by one arm H of a bell crank lever H whenever an input impulse or human effort E applied at the brake pedal F is transmitted to one arm G, of the cooperating brake pedal lever G. The bell crank lever H and the brake pedal lever G are rigidly pivoted at 0' and 0 respectively.
In the known pedal mechanism having a fixed pedal ratio the two arms H2 and G2 of the bell crank
lever H and the brake pedal lever G would be connected directly together at their ends B and A. In the
pedal mechanism illustrated, however, an intermediate member K is disposed between, and movably
pivoted to, the said two arms H2 and G2 at B and A, respectively, whereby the input impulse or human
effort E applied at the pedal F is transmitted by the brake pedal lever G, through the intermediate
member K, to the bell crank lever H and thence to the piston rod of the master cylinder M. The member
K forms a "floating link" between the brake pedal lever G and the bell crank lever H to furnish a variable
pedal ratio, as will become clear from the description of Figure 3.
In practical applications the lengths OA, AB, O'B, O'C and other parameters of the system are
dependent upon the specific vehicle under consideration and the variable pedal ratio obtainable may range from 2:1 to 14:1.
The embodiment illustrated in Figure 2 of the drawings corresponds to the pendent type pedal arrangement. The various components of the pedal mechanism are identified by the same reference letters as the corresponding parts in Figure 1. The operation is essentially the same as that of the embodiment illustrated in Figure 1 of the drawings, and further description of the Figure 2 construction should not be necessary.
Figure 3 of the drawings illustrates a pedal mechanism which is substantially the same as the embodiment in Figure 1. The slight modifications will be apparent from the drawings, in which corresponding parts are identified by the same reference letters in Figures 1 and 3. For various positions
P1 to P5 of the brake pedal lever G, the corresponding positions of the intermediate member K and positions Q1 to Q5 of the bell crank lever H, are depicted. For the following specific dimensions a-f as indicated in Figure 3, the pedal ratio for each of the illustrated pedal positions is a shown in the table below.
a = 354 mm b = 86 mm c = 87 mm d = 88 mm e = 50 mm f = 240 mm Pedal position Pedal ratio P1 3.91 P2 5.96 Pa 7.56 P4 9.25 P, 12.03 From the above table it can be seen that the pedal ratio increases with the pedal travel, which is also shown in Figure 4.
From the graph of Figure 4 in which the pedal ratio R is plotted against the pedal travel T it can be seen that for a fixed pedal ratio as used in the prior art the pedal ratio RF remains constant, whereas with a pedal mechanism according to the present invention the pedal ratio RV increases at a gradually increasing rate as the pedal travel increases.
The graph of Figure 5 illustrates the relationship between the pressure Y in a master cylinder and the travel T of the master cylinder piston. The pressure increases slowly until all the mechanical clearances in the braking system have been taken up, after which the pressure increases rapidly with further piston displacement. Larger forces are then necessary to produce a further increment of the piston travel for which reason a pedal mechanism with a variable pedal ratio according to the invention is of advantage.
Referring now to Figure 6 in which the master cylinder pressure is plotted against pedal travel T for a pedal mechanism with a fixed pedal ratio, as is to be expected the curve follows essentially the same bent path as that of Figure 5. In contrast, the corresponding curve, plotted in Figure 7, for a pedal mechanism in accordance with the invention is much less severely bent and increases almost linearly throughout the full range of pedal movement.
Claims (3)
1. A pedal mechanism for an hydraulic braking system, comprising a pedal lever pivotable about a fixed axis and including a first arm to which a braking effort is applied in use of the mechanism and a second arm, a bell crank lever pivotable about a fixed axis and having a first arm for actuating a master cylinder of the braking system and a second arm, and a member interconnecting and pivoted to the second arms of the pedal and bell crank levers whereby, in use, applying a braking effort to the first arm of the pedal lever causes actuation of the master cylinder, and the pedal ratio of the mechanism increases with the pivoting of the pedal lever under the action of the applied effort.
2. A pedal mechanism according to claim 1 wherein said member comprises a rectilinear, rigid rod.
3. A pedal mechanism substantially as herein described with reference to Figures 1 to 4 and 7 of the accompanying drawings.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
IN143/MAS/79A IN149241B (en) | 1979-08-02 | 1979-08-02 |
Publications (1)
Publication Number | Publication Date |
---|---|
GB2055180A true GB2055180A (en) | 1981-02-25 |
Family
ID=11093849
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB8024614A Withdrawn GB2055180A (en) | 1979-08-02 | 1980-07-28 | Pedal mechanism for hydraulic brake systems |
Country Status (2)
Country | Link |
---|---|
GB (1) | GB2055180A (en) |
IN (1) | IN149241B (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2657051A1 (en) * | 1990-01-13 | 1991-07-19 | Fichtel & Sachs Ag | CLUTCH OPERATING DEVICE. |
US6898995B1 (en) * | 1999-06-17 | 2005-05-31 | Continental Teves Ag & Co. Ohg | Actuation device for a motor vehicle |
GB2423566A (en) * | 2005-02-25 | 2006-08-30 | Bamford Excavators Ltd | A variable ratio brake pedal assembly |
CN104670015A (en) * | 2013-12-03 | 2015-06-03 | 现代自动车株式会社 | Apparatus for reducing effort of clutch pedal for vehicle |
-
1979
- 1979-08-02 IN IN143/MAS/79A patent/IN149241B/en unknown
-
1980
- 1980-07-28 GB GB8024614A patent/GB2055180A/en not_active Withdrawn
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2657051A1 (en) * | 1990-01-13 | 1991-07-19 | Fichtel & Sachs Ag | CLUTCH OPERATING DEVICE. |
GB2240374A (en) * | 1990-01-13 | 1991-07-31 | Fichtel & Sachs Ag | A clutch actuating system |
US5127506A (en) * | 1990-01-13 | 1992-07-07 | Fichtel & Sachs Ag | Clutch actuating system |
GB2240374B (en) * | 1990-01-13 | 1993-11-24 | Fichtel & Sachs Ag | A clutch actuating system |
US6898995B1 (en) * | 1999-06-17 | 2005-05-31 | Continental Teves Ag & Co. Ohg | Actuation device for a motor vehicle |
GB2423566A (en) * | 2005-02-25 | 2006-08-30 | Bamford Excavators Ltd | A variable ratio brake pedal assembly |
CN104670015A (en) * | 2013-12-03 | 2015-06-03 | 现代自动车株式会社 | Apparatus for reducing effort of clutch pedal for vehicle |
US9304529B2 (en) * | 2013-12-03 | 2016-04-05 | Hyundai Motor Company | Apparatus for reducing effort of clutch pedal for vehicle |
Also Published As
Publication number | Publication date |
---|---|
IN149241B (en) | 1981-10-17 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |