FR2485457A1 - VEHICLE HYDRAULIC BRAKING SYSTEM - Google Patents

Abstract

THE PRESENT INVENTION CONCERNS A HYDRAULIC BRAKING SYSTEM FOR A VEHICLE WHOSE LOAD FREQUENTLY VARIES BETWEEN A MAXIMUM VALUE AND A MINIMUM VALUE. THE SYSTEM INCLUDES HYDRAULICALLY DOUBLE DOSING VALVES IN SERIES 14, 16, A VALVE 16 INCLUDING A CAM 25 DRIVEN BY A SPRING, WHICH RESPONDS TO THE COMPRESSION OF THE VEHICLE'S SUSPENSION SYSTEM SELECTS THE RELATIONSHIP BETWEEN THE PRESSURE IN THE MASTER- CYLINDER 11 AND THE BRAKE PRESSURE 15 ACCORDING TO THE STATE OF CHARGE OF THE VEHICLE.

Description

1.

  The present invention relates to improvements

elements supplied to a load-sensing hydraulic brake pressure control device, intended for use in the hydraulic circuit between the master cylinder and the rear wheel brake cylinders. The device

is intended to detect variations in the separation distance

the chassis of a vehicle and the axle shaft suspended

of.

We know that the variation in the load of a vehicle

causes it to vary its braking ability. For example, when a vehicle is fully loaded, the wheels

rear have a braking capacity almost identical to that

  the front wheels. However, when the vehicle load is low, the rear wheels may have a capacity to

  less braking than the front wheels. So the possibility

  bility of a premature rear wheel lock turns out

  much larger when stopping a weak vehicle-

  fully loaded, when stopping a vehicle at full load

ge. In order to compensate for the inherent imbalance between frei-

swimming in the front wheels and braking the rear wheels,

  In the past, a dosing valve has been used which

  mites the passage of fluid towards the rear wheel brake cylinders after a predetermined level of

  pressure. But such valves constitute a compromise between-

be the desirable characteristics of the system for 2.

full load and for light loads. Thus, the charac-

  the selected dosing valve characteristics are not suitable for full load or low

  charge. Numerous flap mechanisms allowing the

tection of the load or the height of the vehicle have been

  proposed in the prior art, but they prove to be useless-

complex or unsuitable for modern vehicles. We are

relate, for example, to patents. United States of America No. 3,362,758; No. 3.503.657; No. 3,649,084, No. 3,684,320; no 3,734,574, no 3,768,876; no.3,848,932; No. 4,150,855; and

no 4,159,855.

  The present invention relates to a perfected device

  hydraulic brake pressure control,

  sensitive to the load, which is arranged in the hydrau-

li upstream of the rear wheels and detect the variations in the distance between the chassis and the axle of a motor vehicle, and control the hydraulic pressure supplied Dar

  the master cylinder to the rear wheel brake cylinders

  re in response to such variations.

  The present invention provides a first assembly and a second metering valve assembly which are connected to each other in series. The first assembly is: placed downstream of the master cylinder and the second between the first assembly and the brakes of the rear wheels of the vehicle. The first valve

metering produces an outlet pressure suitable for a vehicle

  cule being in full load. The second metering valve

  ge, which receives the outlet pressure from the first valve as inlet pressure, acts to modify or adjust the pressure from this first valve to produce an outlet pressure suitable for a lightly loaded vehicle.

  The second metering valve assembly is fixed ri-

  frame to the chassis of the vehicle and includes a rotatable cam

  ve driven by a mechanical link which is fixed to the axle of the vehicle. While the vehicle is loaded, the

compression of the suspension system reduces the separation distance

  the axle chassis. The mechanical link, in re-

  3. does not reduce this distance, turns the cam

  up to a position where the mechanism of the second valve

  sage is off. So the outlet pressure of the first

valve is transmitted without being disturbed by the second

seems to brake the rear wheels of the vehicle.

  The cam sits in rotation on a drive shaft

  axial drag so as to allow relative rotation between these elements. A torsion spring fixed to the cam has one end fixed on it and its other end in

  contact with a flat diametrical surface for lPar cam

  bre training. Thus, the cam is caused to rotate at the same time as the drive shaft. However, as a result

  the presence of the torsion spring, a drive mechanism

  a unique result is obtained which takes account of the relative movement

  between the chassis of the vehicle and the axle during

operation of the vehicle, allowing relative rotation

  ve between the cam and the drive shaft whenever the rotation of the cam is prevented by the operation of the

metering valve mechanism.

  Although the detection metering valve assembly

be described here as being in series with a pre-

  mier together with metering valve, it will be understood that the valve

  load detection can be used alone in systems

temes o the master cylinder outlet pressure is intended to be transmitted without the intervention of a metering valve,

directly to the vehicle brakes when the load is heavy

bearing. The present invention will be well understood during the

  following description made in conjunction with the drawings below

  seals in which: Figure 1 is a schematic view of a hydraulic braking system incorporating a metering valve with

load detection according to the present invention; -

Figure 2 is a graph showing the charac-

  of a brake dosing system according to the present

  the invention; FIG. 3 is an illustration of a typical installation 4. in a vehicle of a load sensing metering valve according to the present invention;

  Figure 4 is a partly sectional view of the screen.

  metering pet used in the braking system shown in figure 1; Figure 5 is a sectional view taken along line 5-5 of Figure 4; Figure 6 is a partly sectional view taken along line 6-6 of Figure 4; Figure 7 is a partly sectional view taken along line 7-7 of Figure 4;

  Figure 8 is an exploded illustration of the in-

  seems elements constituting the cam part of a metering valve with load detection; Figure 9 is an illustration of the cam after rotating 180? compared to Figure 8; Figure 10 is a schematic representation of the metering valve when the vehicle load is low; Figure 11 is a schematic representation

metering valve when the vehicle load is high

aunt; Figures 12 and 13 are schematic representations of the metering valve when account is taken of an over-rotation of the cam drive shaft; and Figure 14 is a partly sectional view of the

  metering valve, similar to that of figure 6, where the

  cam mechanism is shown when there is a clockwise rotation of the drive shaft

of the cam.

  In connection with the figures, there is shown in figure

  gure 1 a hydraulic vehicle braking system according to

the present invention. A master cylinder 11 provides a fluid

  hydraulic pressure actuation of brakes via a line F to the brakes 13L and 13R

  front wheels of the vehicle after passing through a key assembly

metering pet, not shown, contained in a combination assembly 12. A pipe R likewise constitutes a source

  independent of hydraulic fluid under operating pressure

  5. ment of brakes for a first metering valve assembly 14, shown diagrammatically in combination with assembly 12, for supplying the fluid to the brakes 15L and 15R of the

rear wheels.

The metering valve 14 can be of a type known in the prior art, for example the valve described in US Patent No. 3,423,936, having a single burst point between the hydraulic pressure d 'Entrance

and the hydraulic outlet pressure. According to this iïnven-

  tion, the metering valve 14 is designed to produce a pressure

  outlet pressure linked to the inlet pressure as shown in L in figure 2. The burst point at which the valve 14

  begins to carry out the dosing being represented in L. The cour-

  be L of FIG. 2 represents the relationship between the pressure in the master cylinder and the pressure in the rear wheel brakes in the case of a vehicle loaded beyond half-load up to the gross weight of the vehicle. The pressure of the hydraulic fluid leaving the valve 14 is transmitted to the

  rear wheel brakes via Rl and R2 lines, which

pour a device 20 comprising a metering valve with

load protection.

The device 20 comprises a second assembly

metering pet 16, described in more detail below, the construction of which is similar to that of the metering assembly 14

  contained in combination set 12. The key set

metering pet 16, when allowed to operate, works

  when the hydraulic outlet pressure from the metering valve 14 is applied, in such a way that the relationship between the pressure of the master cylinder (inlet to

  metering flap 14) and the rear brake pressure (out-

part of the metering flap 16) is represented by curve E in FIG. 2. Curve E represents the relationship between the pressure in the master cylinder and the pressure in the rear brakes which is acceptable for

vehicle load falling below the mid-condition

load selected.

A cam mechanism 25 is provided in the device 6. so as to put the metering valve 16 in the position

  fully open when the vehicle is heavily loaded.

Thus, when the vehicle load is beyond the selected half load, the metering valve 16 is turned off by the action of the cam 25, which allows transmission without disturbing the pressure. hydraulic and

translated by the relation corresponding to the curve L of the figu-

  re 2. However, when the vehicle load is low, the

  metering valves 14 and 16 operate in series, and the rela-

tion between the master cylinder pressure and the rear brake pressure is represented by curve E in FIG. 2. FIG. 3 is an illustration of an installation

  typical on vehicle of the metering valve with tank detection

ge of the present invention. The device 20 is fixed rigidly

ment to an unsprung part of the chassis 35 of the vehicle.

A drive shaft 50 is fixed to a link 30, so that during the rotation of this link, the shaft

  drive 50 rotates cam 25 via

re of a drive mechanism which will be described below in detail. The rod 30 is fixed to the tube 31 of the axle of the vehicle or to any other appropriate element of the part

  suspended from the rear wheel system.

  The cam 25, under the action of the link 30 fixed to the axle 31, responds to the compression or expansion of

vehicle suspension (not shown). When the biel-

  lette is expanding (reference 30, figure 1), the charge of

  vehicle is weak and the metering flap 16 is brought to function

  tion. However, when the link is compressed (re-

  ference 30 ', Figure 1), the vehicle load is high and the cam 25 is caused to rotate to a position o

  the metering valve 16 does not work.

  In connection with FIG. 5, the metering valve assembly 16 as shown and described here, represents

  simply a known metering flap mechanism, and does not

  does not affect part of the present invention. Considering

  than any known metering valve mechanism that can be modified

  set to work as described here is usable in

* 2485457

  7- the present invention, the operation of the assembly 16

  will be described only to the extent that it allows

  take its relationship with the cam of the present invention and its operation in the overall hydraulic braking system.

  The metering valve assembly 16 includes a nozzle

  ton 40 placed axially inside a bore 45, and

  extending into a bore 45a of smaller diameter, the-

  which opens into a cavity 70 containing a cam. An O-ring 47 hydraulically seals the bore 45 with respect to the bore 45a, which has the effect of avoiding the

  circulation of hydraulic fluid in bore 45a. The pis-

  tone 40 has an extension portion in the form of a small axis 48, which projects into a bore 49. The piston 40 can move axially inside the bore 45a, so that the axis 48 can be in protrusion in the cavity 70,

as will be described below.

  The opposite end of the piston 40 comprises a valve head 43 with a diameter less than that of the bore 45b, which allows an unimpeded flow of the hydraulic fluid. The

  piston 40 has on the other hand a cap 41, which comprises a

  check mark 42. The piston 40 is normally biased to the left

  che by a spring 46, so that the cap is stressed

  so as to abut against the end of the bore 45b.

  Hydraulic fluid can thus enter the inlet

  mission R1, pass freely between the piston 40 and the elastomer valve seat 44, pass at the level of the head 43,

  and via the notch 42 exit through the orifice R2.

  Thus, in the configuration shown in FIG. 5, the pressure

  fluid pressure at outlet R2 will be equal to the pressure

  sion of the fluid at the inlet port Rl.

  During application of the brakes, the previous route

  fluid tooth through the assembly 16 remains open until the pressure of the fluid supplied to the outlet port RI reaches a predetermined level. At that time, the head of

  valve 43 will close against seat 44. The level of pressure

  sion at which this occurs is a function of the tension of the 8. spring 46 relative to the effective surface of the piston 40 on

  which acts the pressure of the inlet fluid in a direction

  tiQn opposite the spring tension. The effective area

  is equal to the diameter D of the piston 40 since the end

  right half of the piston 40 protruding into the bore 45a is

  not subject to inlet fluid pressure due to -

  presence of O-ring 47, then believed this pressure acts

  on all the other parts of the piston 40.

  After pressing the valve head 43 against the seat

  ge 44 and increase of the fluid pressure at the orifice

  input Rl, this greater pressure will act on a surface

  this effective circular of the piston 40 with a diameter equal to

  main sealing diameter of the head 43 minus the surface

  this in section of the piston 40 extending in the bore 45a. This has the effect of producing a force acting on the piston 40

  in the same direction as the spring 46 to reopen the head

  valve te 43 and supply at least a portion of the fluid at higher pressure to the outlet port R2. However, any supply of this type to the outlet port R2 creates a force opposing the movement of the piston 40. This force

  tends to close the head 43 against the seat 44. This form

  this tends to keep the head 43 very close to the seat 44, which has the consequence of limiting the flow of fluid between the inlet port R1 and the outlet port R2, creating pressure at the outlet port R2 increasing at a rate

  less than the pressure at the inlet Rl. Rap-

  pressure port is determined by the relationship between the effective surfaces discussed above and therefore, the pressurized fluid passing through the valve 16

  can be dosed to follow a predetermined relationship.

  - During this part of the application of the brakes

  o the pedal force is reduced following an application

  cation of the brakes with sufficient intensity to have

  moved the piston 40 to the limit position of the

  bit, the forces tending to move the piston 40 to the left

  che are reduced and the piston 40 moves to the right

  under the effect of the pressure prevailing at the outlet orifice R2.

  9. As the piston 40 moves to the right, the head

  valve 43 can slide in the internal peripheral surface

  seat 44, which has the effect of increasing the volume available for the fluid to the rear brake cylinders lSL and 15R and of achieving a reduction in the pressure at the outlet orifice R2. The pressure in this R2 port can never

  be greater than the pressure in the inlet port RI par-

  that the seat 44 also acts as a shut-off valve allows

  both the circulation of the fluid between the orifice R2 and the bore 45. Reference is made to US Pat. No. 3,423,936 of January 28, 1969 in the name of William Stelzer for

  find a more detailed description of the function-

  the metering valve and the design of the elements of a

special dosing valve.

  Reference is made to FIGS. 4 to 9 for the description

  tion of cam 25, its construction and its operation

  is lying. The housing 19 of the device 20 has a bore with two steps. The bottom 69 of the bore 60 contains a

  semicircular groove 67 and a bearing groove 68. The rear

  bre 50 cam drive is supported and maintained

  indicated to me in figure 4. The bearing 51 of the shaft 50 is received

  - in rotation in the recess 68. The shaft 50 extends generally-

  perpendicular to the bottom 69 crossing an ex- cap

  end 61 which supports it in rotation. Hat 61 is my-

  tee with tight fit in the bore 60a and pressed against a shoulder 62 by a circlip 63. An O-ring 55 serves to seal the chamber 70 for cam against the entry of

  foreign bodies. The cam drive shaft 50 is in sail-

  binds on the outside of the cap 61, over a sufficient length

  you to allow its engagement in a rod 30 (see

  figure 3). Thus, the drive shaft 50 is brought to turn-

  ner following the same angular displacement as the rod 30.

  The cam 25 is rotatably supported by a bearing 52 of the drive shaft 50 so that it can rotate

  relative to this tree. The cam 25 has a small recess

  ripherique 26 and knurling 24 directed axially on at least 10. its working periphery. The working periphery of

  cam 25 will appear in the additional description of

  its function and operation. An axis 32 is axial-

  ment projecting from the cam 25 and engages in a slot 67 in which it slides, slot made in the bottom 69

  of the bore, which has the effect of limiting the angle of rotation

  tion of the cam 25 to the rotation allowed by this slot. The inner side 22 of the cam 25 is milled to give a stepped surface 27 facing inward. A circular recess 21 extends axially in the cam 25 between the outer surface 28 and the surface 27, which constitutes a passage 23 between the surfaces 28 and 27. A mandrel 33 is mounted axially inside the circular recess 21 extending outward and slightly r-right of the outer surface 28. A torsion spring 34 surrounds the

  mandrel 33, its helical part being seated in the recess

  circular mint 21, so that its inner end

  34a extends in passage 23 while being juxtaposed on the over-

  face and engages in a spring retaining hole 29. The ex-

  outer end 34b of the spring is juxtaposed with the surface

  this 28 of the cam. 25, extends into a slot 54 of the drive shaft 50 and is in contact with a cam surface

  53. Under the normal mounting conditions described above

  above and represented in FIG. 6, the ends 34a and 34b of the torsion spring are under tension so as to apply a force directed angularly towards the outside - on the spring retaining hole 29 and on the flat cam surface 53 of the drive shaft 50. A slot 56 is made at the outer end of the shaft 50 so as to allow a

external adjustment.

  In operation, the cam 25 is brought to turn-

  ner with the shaft 50 under the effect of the spring 34 which applies its tension on the surface 53 of the shaft 50. But, in the case where the cam 25 is prevented from rotating due to a

  contact between axis 32 and groove 67 or a contact between

  be the cam 25 and the axis 48 of the piston 40, the shaft 50 could nevertheless rotate relative to the cam 25 thanks to a

2.85457

11.

  new compression of the torsion spring 34. Thus,

  holds a spring drive mechanism between the shaft 50

  of the cam and cam 25, which allows an over-

  believes the shaft 50 travels when the rotation of the cam 25 is moreover limited. Figures 3, 5 to 7, and 10 show the shape of the device 20 with metering valve and load detection in the case where the vehicle load is of low value. The chassis 35 of the vehicle is relatively high relative to the suspended axle 31. Thus, the link 30 positions the cam 25 in such a way that the peripheral recess 26 allows the axis 48 of the piston 40 to move axially to enter and exit the chamber 70. The metering valve 16 can thus operate freely, which results in a relationship between the pressure of the master cylinder and the pressure

  rear brakes represented by curve E in FIG. 2.

  As long as the vehicle is lightly charged, the

  metering pet 16 works. The peripheral recess 26 does not interfere with the operation of the valve 16. However, in the case where the axis 48 of the piston is projecting into the chamber

  as a result of the vehicle braking and o the vehicle

  against bad road conditions which cause a

  momentary over-rotation of the shaft 50 due to compression

  excessive suspension of the vehicle suspension system, the cam 25 momentarily comes into contact with the axis 48 of the piston, which stops its rotation in an anti-clockwise direction. However, the cam drive shaft 50 can continue to rotate anti-clockwise by compression of the torsion spring 34. Such

  situation is shown in figure 13.

  When the vehicle is at maximum load, the system

* suspension head is compressed, so that the distance ver-

  between the frame 35 and the axle 31 is reduced.

  The rod 30 takes the position shown in Figure 11, which causes the cam 25 to rotate counterclockwise as shown. In

  this situation, the outermost periphery of the

  25 turns to a position that turns off 12.

  the valve 26, which has the effect of avoiding free transla-

  piston 40. Thus, at full load, as is re-

  presented in figure 11, the relation between the pressure of the evil-

the cylinder and the rear brake pressure is given by curve L in FIG. 2. As long as the vehicle is in these fully loaded conditions, the outer periphery

  of cam 25 will keep the position where it has been switched off

operation of the valve piston as shown in Figures 11 and 12. In this position, and when the

applied braking load is such that the piston 40 is

to move to the right, the axis 48 of the piston abuts against the cam 25 and engages in the axial parts

  knurled 24 of the outer periphery of the cam 25. Ain-

  if, the cam 25 is prevented from rotating freely. Any rota-

  subsequent drive shaft 5C0 of the cam

  resulting from vascillations of the axle 31 due to the road will

accepted by compression of the torsion spring 34, as re-

presented in figure 12.

  - The angle A (Figure 6) between the central line of the axis 48 and the step 26a of the cam determines the vehicle loading conditions for which the metering valve 16 is put out of operation; therefore, it is necessary that this angle be set precisely. The angle A is determined

  for an unloaded vehicle and represents the angle according to-

which drive shaft 50 will rotate while the vehicle

  is loaded until mid-charge, for which you do not want to-

  ser from curve E to curve L in FIG. 2. The step 26b is placed so as not to interfere with the operation of the metering valve 16; the axis 32 and the groove 67 can also have a shape such that the rotation of the cam 25 clockwise is limited, which has the effect

  to prevent the step 26b from interfering with the operation

metering valve 16.

  The metering and load detection valve device shown in FIGS. 1 to 13 makes it possible to take account of a rotation of the shaft 50 anticlockwise during the compression of the suspension system. of the vehicle. However, this device can be easily adapted to take into account a clockwise rotation as shown in FIG. 14. A new positioning of the groove 67, as shown in FIG. 14, makes it possible to adapt the one-way mechanism

rotation having this sense.

The present invention is not limited to the examples

ples of realization which have just been described, it is at.

otherwise subject to variations and modifications which

will appear to those skilled in the art.

14.

Claims (8)

  1 - Dosing valve for hy- braking system   vehicle hydraulics, comprising a deactivation mechanism   operation by which the valve can be made selected tively inoperative for given load conditions of the vehicle, characterized in that it comprises a valve means comprising a piston means responding to a hy-   hydraulics for its actuation; a rotary cam means having a cam profile communicating with the piston means, a rotary shaft, a means of coupling between the cam and the shaft, following what the rotation of the shaft acts on the rotation of the rotary cam, the cam profile is as it allows   to limit the displacement of the piston means when the turns me to a given angular position, which has the effect of locking the valve means in a non-operating position, a means for rotating the rotary shaft in response to the load conditions of the vehicle. 2 - Valve according to claim 1, characterized in that the rotary cam comprises a stop means, as a result of which the angle of rotation of the cam is limited to a predetermined value. 3- valve according to claim 2, characterized in that the coupling means comprises an elastic means that, which has the effect of allowing the rotary shaft to rotate at an angle of rotation greater than that of the rotating cam. 4 - Valve according to claim 1, characterized in that the rotary cam is coaxial with the rotary shaft and can rotate around it, the shaft comprising a D-shaped part extending axially and the coupling means comprising a torsion spring, one of which 15. 2485457 one end is fixed to the rotary cam and the other end is in driving contact with the flat surface of the D-shaped part of the rotary shaft, after which this shaft will rotate independently of the rotary cam and by relative to this each time the shaft torque is sufficient to cause the torsion spring to flex. 5 Metering valve for a vehicle's hydraulic braking system, comprising means for blocking   valve, as a result of which, the valve can be rendered inoperative   rant in an open bypass position for selected vehicle load conditions, characterized in that he understands. - a housing comprising a first bore and a second bore, the axes of which intersect at right angles, the first bore containing a metering valve means   taking a piston means extending axially therein ci and in the second bore;   - a rotary shaft means coaxial with the second bore -   ge and extending axially therein, a cam means   circular coaxial to the second axis of bore extending radially   outwardly from a rotary shaft means, a coupling means between the rotary shaft and the circular cam means, as a result of which the rotation of the shaft acts on the rotation of the circular cam, the circular cam means having a cam profile which communicates with the piston means of the metering valve, the cam profile being such that it limits the movement of the piston means when the cam means rotates in a position given angle, giving the valve an inoperative configuration of open bypass, a means for rotating the rotary shaft in   response to vehicle charging conditions.   6 - Valve according to claim 5, characterized in that the rotary cam comprises a stop means, at the as a result of which its angle of rotation is limited to a pre-arc determined. 16. 2485457   7 - Valve according to claim 6, characterized in that the coupling means comprises an elastic means, which allows the rotary shaft to rotate at an angle   higher than that of the rotary cam. 8 - Valve according to claim 5, characterized in that the circular cam means can rotate around   the rotary shaft, the shaft having a D-shaped portion extends   axially, and the coupling means comprising a torsion spring, one end of which is fixed to the cam   tative and the other end is in drive contact with the flat surface of the D-shaped part of the rotating shaft tif, after which the rotating shaft will rotate independently ment of the rotary cam and in relation to it whenever the torque of the rotary shaft is sufficient to cause deflection of the torsion spring.