CROSS-REFERENCE TO RELATED APPLICATIONS
The present invention relates to a braking system for a vehicle, more particularly to a pneumatic braking system of a heavy vehicle, such as a vehicle with multiple axles, at least two of them being front axles.
Heavy vehicles can include several front and/or rear axles required by the high weight of the vehicle or of the carried load.
According to recent regulations in the field of heavy vehicles, the vehicle must be able to brake within a preset distance based on the type of vehicle.
With traditional braking systems, i.e. rear braking systems, such braking distances could not be guaranteed. This was the reason for developing front braking circuits so that the braking torque, acting both at the front and at the rear, could brake the vehicle within the preset distance required by the regulations.
However, such front braking systems are expensive and bulky, above all due to the necessary emergency circuit required by the aforementioned recent regulations.
There is therefore a need to improve braking systems for heavy vehicles so that braking can be performed under normal and under emergency conditions in an optimized and inexpensive way.
The object of the present invention is to satisfy the requirements set forth above.
SUMMARY OF THE INVENTION
The above object is achieved by means of a braking system as claimed in the attached claims.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the present invention, a preferred embodiment is described below by way of nonlimiting example and with reference to the attached drawings, in which:
Figure 1 shows a diagram of a circuit of a braking system according to the invention in a first operating step; and
Figure 2 shows the diagram of Figure 1 in a second operating step.
DETAILED DESCRIPTION OF THE INVENTION
The accompanying figures show a braking system 1 for one of the front axles (not shown) of a group of front axles of a heavy vehicle (not shown), in particular, the second front axle of a truck or a lorry.
According to the invention, as shown in Figure 1, the braking system 1 essentially comprises a first portion 2 configured to allow the braking of the front axle under normal conditions and a second portion 3 configured to allow the braking under emergency conditions, fluidically connected together by a safety valve 4 as described in detail below.
In particular, the portion 2 comprises a first accumulator 5 of pressurized air fluidically connected by means of a duct 6 to braking means configured to brake the front axle to be braked. These braking means can be of any known type.
In particular, the duct 6 branches into two branches 6a, 6b to introduce this pressurized air into the left and into the right braking means. The portion 1 can further comprise, for each of the branches 6a, 6b and fluidically interposed on them, a switching valve (also called relay valve) 6c, configured to distribute, as already known, the braking pressure both on the right and on the left side of the axle.
Along the duct 6, the portion 2 comprises a control unit 7 or "CBU" (Control Brake Unit), configured to regulate the passage of air from the accumulator 5 to the braking means through the duct 6 when requested by the user of the vehicle, for example by pressing a special pedal.
The first accumulator 5 is also fluidically connected to the safety valve 4 through a relative duct 8, preferably joining the duct 6 upstream of the control unit 7. The accumulator 5 is of a known type and is configured to be able to introduce air at a pressure between 8 and 10 bar, preferably 8 bar.
The second portion 3 comprises a second accumulator 9 fluidically connected to the front axle to be braked by a respective duct 11. Advantageously, the accumulator 9 is of a known type, is configured to be able to introduce air at a pressure between 8 and 10 bar, preferably 8 bar, and is part of the parking braking circuit of the vehicle.
In particular, the duct 11 branches off into two branches 11a, 11b to introduce this pressurized air into the left and right braking means. Advantageously, the two branches 11a, 11b are fluidically connected to the branches 6a, 6b of the duct 6, upstream of the braking means, through a respective valve 12, preferably a pressure selector valve (also known as shuttle valve) configured to allow pressurized air to go from the branch at the higher pressure among the branches 6a, 11a and 6b, 11b to the front axle of the vehicle.
Advantageously, the safety valve 4 is configured to detect a failure condition of the portion 2, e.g. a pressure drop in the duct 6 as described below, and consequently allow the connection of the portion 3 to the braking means of the front axle.
According to the described embodiment, the safety valve 4 is fluidically connected to the portion 2 through a duct 13, which fluidically connects the duct 11, upstream of the branch in the portions 11a, 11b, with the safety valve 4.
In particular, this duct 13 can fluidically connect to the duct 11 through a switching valve 11c configured to allow the passage of pressurized air from the accumulator 9 to the front axle through the duct 11, when actuated. Advantageously, the actuation of this valve 11c can be carried out pneumatically by the pressure present in the duct 13.
The safety valve 4 can also be fluidically connected through a duct 14 to a braking circuit of the rear axle, for example an EBS (Electronic Brake System), or even better to a valve of such a system.
Advantageously, the safety valve 4 is a two-way, two-position valve configured not to allow the passage of an air flow under normal conditions (Figure 1) or to allow the passage of an air flow under failure conditions from the rear braking system to the portion 3 (Figure 2), when the pressure in the portion 2 (and therefore in the duct 8) falls below a preset threshold. For example, this preset threshold can be a pressure lower than 3 bar.
Preferably, the safety valve 4 is pneumatically controlled with respect to elastic reaction means by the pressure in the duct 8. When this pressure is higher than the preset value, the elastic force of the reaction means is overcome and therefore the valve 4 remains in the zero flow condition, whereas when this pressure is lower, the elastic force of the means moves the valve 4, thus allowing the flow from the rear braking system to the second portion 3.
The operation of the braking system 1 according to the invention is as follows.
Under normal operating conditions (Figure 1), the pressure in the portion 2 is higher than the preset threshold, namely above 3 bar. Therefore, the valve 4 is arranged so that the pressurized air coming from the duct 14, namely from the rear braking circuit, does not pass into the portion 3. In this configuration then, as regulated by the control unit 7, the air from the accumulator 5 flows towards the right and the left braking means, passing through the duct 6 and the related switching valves 6c and selector valves 12.
Under failure conditions (Figure 2), the pressure in the portion 2 falls below the preset level, therefore below 3 bar, and the valve 4 switches, thus allowing the pressurized air from the rear circuit to flow towards the switching valve 11c, which allows the pressurized air in the tank 9 to flow through the duct 11 and the selector valves 12 towards the front right and left brakes of the second front axle.
In this way, even in the event of a failure in the front system, braking is allowed anteriorly and posteriorly through the signal coming from the rear axle. Then, braking at the rear, the user also automatically activates the braking of the second front axle.
From the foregoing, the advantages of a braking system 1 for heavy vehicles according to the invention are clear.
Thanks to the safety valve 4 it is possible to pass from the portion 2 relating to the normal operation of the braking system 1 to the portion 3 relating to the emergency operation.
The use of pressure from the rear circuit, brought to the valve 4 through the duct 14, allows the front brakes to be controlled easily and practically even in the event of any failure of the portion 2.
The layout of the system according to the invention therefore satisfies the requirements of the regulations, while maintaining a minimum bulk and a reduced number of elements. Consequently, it is inexpensive and easy to assemble.
Finally, it is clear that modifications and variations may be made to the heavy vehicle braking system according to the present invention, which however do not depart from the scope of protection defined by the claims.
For example, the layout could be implemented differently from what described and the safety valve 4 could be manufactured differently from what described.
1. A braking system (1) for supplying air to braking means of a heavy vehicle front axle, said system (1) comprising a first portion (2) provided with a first accumulator (1) for pressurised air fluidically connectable to said braking means through a first duct (6) and with a control unit (7) configured to adjust the fluidic communication between said first accumulator (1) and said braking means, said system further comprising a second portion (3) provided with a second accumulator (9) for pressurised air fluidically connectable through a second duct (11) to said braking means and a safety valve (4) configured to fluidically connect said second accumulator (9) to said braking means once detected a failure in said first portion (2).
2. The system according to claim 1, wherein said failure is detected when the pressure of said first duct (6) drops below a preset value.
3. The system according to claim 1 or 2, wherein said preset pressure value is less than 3 bar.
4. The system according to any one of the claims 1 to 3, wherein said valve (4) is a two-way two-position valve.
5. The system according to any one of the preceding claims, wherein said valve (4) is a pneumatically controlled valve.
6. The system according to claim 5, wherein said pneumatic control is carried out by said first duct (6).
7. The system according to any one of the preceding claims, wherein the portion (3) comprises an on-off valve (11c) fluidically interposed on said second duct (11) and fluidically connected to said valve (4) and wherein said valve (4) is fluidically connected to a braking system of a rear axle of said vehicle through a third duct (14), when said pressure in said first portion (6) drops below said preset threshold, said valve (4) allows the flow of the pressurised fluid in said duct (14) in said on-off valve (11c) that in turn allows the fluidic connection between said second accumulator (9) and said braking means.
8. The system according to any one of the preceding claims, wherein said first and second ducts (6, 11) are fluidically connected to one another upstream of said braking means by means of respective selector valves (12).
9. The system according to any one of the preceding claims, wherein said second accumulator (9) is part of a parking braking circuit of said vehicle.
10. A heavy vehicle comprising at least a rear axle and at least a front axle, said rear axle comprising a pneumatic braking system, said vehicle comprising a braking system for one of said at least one front axle according to any one of the preceding claims.