Automatic braking device for a vehicle

An automatic braking device for a vehicle equipped with at least one fluid circuit connecting a master cylinder (10) to a consumer circuit including at least one brake motor and possessing, furthermore, a pump (30) capable of delivering to the consumer circuit, via a non-return valve (31), fluid under high pressure taken from the master cylinder (10) comprises, in combination, a proportional solenoid valve connected to the consumer circuit and having a regulating outlet (20), during operation in the solenoid valve regulating the pressure of the fluid in the consumer circuit in relation to that of the fluid in the feed circuit of the pump, and a regulating slide (16) arranged between the master cylinder and the feed circuit of the pump in order to regulate the pressure of the fluid in the latter circuit and determine a reference pressure for the solenoid valve.

BACKGROUND OF THE INVENTION 
The present invention relates to an automatic braking device for a vehicle 
equipped with at least one fluid circuit connecting a master cylinder to a 
consumer circuit including at least one brake motor and possessing, 
furthermore, a pump capable of delivering to the brake motor fluid under 
high pressure taken from the master cylinder. 
Such a device has many uses which an average person skilled in the art can 
easily combine. For example, it can be employed in a vehicle equipped with 
a wheel anti-lock system, for automatically commanding braking in response 
to a signal emitted by a marker or by a radar detecting an obstacle. It 
can also be employed for braking the driving wheels automatically when a 
skid is detected, especially during acceleration. 
In all instances, for obvious safety reasons, the driver of the vehicle 
thus equipped must be able to brake his vehicle even if the device is in 
the automatic operating mode. 
The document EP-A-0,230,213 describes a circuit allowing an automatic 
control of braking in the event that an obstacle is detected. However, 
this circuit does not make it possible to perform all the functions 
described above. 
SUMMARY OF THE INVENTION 
It is therefore an object of the invention to provide a device capable of 
performing all these functions. 
According to the invention, the automatic braking device comprises, in 
combination, a proportional solenoid valve connected to the consumer 
circuit and having a regulating outlet, during operation this solenoid 
valve regulating the pressure of the fluid in the consumer circuit in 
relation to that of the fluid in the feed circuit of the pump, and a 
regulating slide valve arranged between the master cylinder and the feed 
circuit of the pump in order to regulate the pressure of the fluid in the 
latter circuit and determine a reference pressure for the solenoid valve.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to this single FIGURE, a master cylinder connected to a 
conduit 12 will be seen at 10. This conduit 12 is open onto a regulating 
slide valve 16 returned to rest by a spring 17, so as to allow open 
communication between this conduit 12 and a chamber 14, made on one side 
of the slide valve 16, and a conduit 18 forming part of the feed circuit 
of the pump 30. The chamber 24 made on the other side of the regulating 
slide valve 16 receives the atmospheric pressure. When this regulating 
slide valve 16 is displaced under the effect of the difference between the 
pressures prevailing in the chambers 14 and 24, it regulates the pressure 
of the fluid in the conduit 18 of the suction circuit of the pump. 
In a known way, the pump 30 is capable of feeding fluid under high pressure 
to the brake motor 22 via a non-return valve 31. The feed inlet of the 
pump 30 is connected to the reservoir 28 by means of the conduits 12 and 
18 and the master cylinder 10. This conduit 18 is likewise in 
communication with the two ends of the slide valve 36 of the solenoid 
valve, so as to determine a reference pressure for the proportional 
solenoid valve. 
The solenoid valve comprises a core 32 subjected to a magnetic field 
intended for moving, by means of a push rod 35, the slide valve 36 
returned to rest by a spring 44. A needle 40 immobile relative to the body 
of the assembly as a whole penetrates into a bore made in this slide valve 
36 so as to determine a reaction chamber 38. This latter chamber 38 is 
permanently in communication with the consumer circuit comprising the 
anti-lock device 41 and the brake motor 22. 
The core 32 has a shutter 45 for closing communication between the conduit 
18 and the feed conduit of the pump 30 in the non-automatic operating 
mode. Such a shutter 45 is necessary only if the anti-lock device 41 makes 
use of the same pump 30. In this case, the feed conduit of the pump is 
also connected to a low-pressure reservoir (not shown in the FIGURE) via a 
non-return valve. 
During normal braking, the pressure generated by the master cylinder is 
therefore repeated in the brake motor 22 since the slide valve 36 remains 
in the rest position and the solenoid valve is not energized. When a wheel 
lock is imminent, the anti-lock device 41 functions in the usual way. 
Now during automatic operation, that is to say in response to an external 
command, since no pressure is generated by the master cylinder 10, the 
pump 30 and the solenoid valve are activated simultaneously. Communication 
between the feed inlet of the pump and the reservoir 28 is ensured by the 
shutter 45, then open, and by the regulating slide valve 16. The fluid 
sucked up by the pump 30 therefore remains at low pressure in the conduit 
18. The regulating port of the solenoid valve is in communication with the 
reservoir 28 by way of the master cylinder 10, in the brake motor 22 in a 
controlled manner. The wheel anti-lock device 41 remains in operation in 
order to prevent any inopportune locking of the wheels. 
If the driver wishes to brake his vehicle during the automatic braking 
time, a pressure is generated in the master cylinder 10. The regulating 
slide valve 16 then performs its function by regulating the pressure of 
the fluid sucked up by the pump 30 via the conduit 18 to a relatively low 
value which is essentially a function of the rigidity of the spring 17 and 
of the active hydraulic cross-section of the slide valve 16. 
To attempt to regulate the pressure according to the instruction received, 
the port 20 then opens to a greater extent. The pressure generated by the 
master cylinder 10 is thus applied to the brake motor 22. 
This device therefore makes it perfectly possible to perform the 
abovementioned functions in complete safety. In particular, it has the 
advantage compared to many known devices of allowing the vehicle to be 
braked during an anti-skid period, if the automatic operating mode is 
provided for preventing the skidding of the driving wheels and a 
progressive transfer, without pressure surges, between the automatic 
operating mode and the manual operating mode. 
It will be appreciated that an average person skilled in the art can easily 
make modifications to this device, without departing from the scope of the 
invention, as defined by the accompanying claims.