Hydraulic braking assembly for a vehicle comprising a hydraulic fluid level sensor

A hydraulic braking assembly (14) for a vehicle comprising an electric servomotor (15), a master cylinder (16), a hydraulic fluid tank (17) mounted on the master cylinder, a hydraulic fluid level sensor (25) situated inside the fluid tank and monitoring the hydraulic fluid level inside the tank. The fluid level sensor is connected from the tank to the computer of the electric servomotor by a cable (26).

BACKGROUND OF THE INVENTION

The invention relates to a hydraulic braking assembly of a vehicle comprising a hydraulic fluid tank, said tank being equipped with a hydraulic fluid level sensor. The aim of the invention is to simplify the fitting of a hydraulic braking assembly. Another aim of the invention is to reduce the manufacturing cost of this hydraulic assembly.

The invention can be applied to the motor vehicle field but could be applied to other fields.

FIG. 1diagrammatically illustrates a hydraulic braking assembly1of the state of the art. This hydraulic braking assembly1is formed by an electric servomotor2supporting braking (brake booster), a hydraulic master cylinder3, a hydraulic fluid tank4and at least one hydraulic braking circuit (not represented). The servomotor2comprises an electric motor5, a computer6and a battery7. The computer6forms an electronic control device and is connected to the battery7. A brake pedal (not represented) is connected to a control rod8, which is in turn mechanically connected to the servomotor2. The computer6is also connected to a central control member (not represented) by a first cable9. The central control member collects all the electronic vehicle data. The central control member may include a dashboard to which the first cable9is connected by means of a CAN (Controller Area Network) type bus.

The tank4is mounted on the master cylinder3to feed at least one chamber (not represented) of the master cylinder3with fluid. The hydraulic braking circuit connects the chamber of the master cylinder3to a braking device (not represented) mounted on a wheel of a vehicle.

The electric servomotor2comprises a screw/nut assembly10converting a rotational movement of the rotor-forming nut of the electric motor5into a rotational movement of the screw which displaces a support piston11toward the master cylinder3. The servomotor2is actuated by the control rod8displaced by the brake pedal. A force sensor (not represented) measures the force applied to the control rod8by the driver via the brake pedal. The information concerning the force applied to the control rod8is transmitted to the computer6. This computer6then generates, on the basis of this information, a control command to the electric motor5so as to displace the support piston11according to the force exerted on the control rod8.

The fluid tank4contains an amount of hydraulic fluid that makes it possible to permanently feed the chamber of the master cylinder3.

A hydraulic fluid level sensor12is placed inside this tank4. This sensor12is, in one example, of the REED glass envelope type or of the HALL effect type (or proximity magnetic sensor). In the case of a REED glass envelope sensor, it is formed by two electromagnetic blades and by an electromagnet. The two blades are in contact with one another as long as the electromagnet is placed above the blades, that is to say that the fluid level is above the blades. When the electromagnetic approaches the blades, they end up separating because of the proximity of the electromagnet tending to separate the blades from one another. The electrical contact is then broken and this information is transmitted to the driver via a light and/or audible signal communicated by a dashboard.

The sensor12is electrically connected to the central control member by a second cable13. The central control member may also include a central computer to which the second cable13is linked.

A first cable9and a second cable13are therefore necessary to connect the hydraulic braking assembly1to the central control member. The problem is that the second cable13is bulky, possibly measuring up to 50 cm to reach the central control member. This second cable13may be inadvertently caught when the bonnet of the vehicle has to be opened to check the condition of at least one member of the vehicle or to repair at least one member. This second cable13may then be cut or at least hinder the operator. To avoid the possible hindrance of this second cable13, it can be arranged in a controlled manner inside the space enclosed by the bonnet of the vehicle. To do this, this second cable13may be pressed against a wall of the cowl while being clipped, or else glued or clipped against another wall of a member of the vehicle. However, the surface of certain areas of the cowl (those exposed to external climatic variations), or the surface of a given member, may be subject to temperature variations that may damage the quality of this second cable13. Notably, the heat or cold may impede correct operation and/or cause premature wear of this second cable13. It is therefore important to be careful to choose the correct places, that is to say those which present least risk of damaging the quality of this second cable13.

Fitting such a second cable is therefore difficult, tedious and costly.

SUMMARY OF THE INVENTION

The object of the invention is therefore to remedy this problem.

More particularly, according to the invention, the level sensor is no longer directly connected to the central control member but to the computer of the servomotor. In this way, it is no longer necessary to provide the second cable. Only a third cable which directly connects the sensor to the computer of the servomotor is provided according to the invention. The length of this third cable is greatly reduced compared to that of the second cable since the computer of the servomotor is situated in proximity to the hydraulic tank.

Thus, the hydraulic assembly therefore forms a single-piece assembly which can be connected by a single cable to the central control member.

The invention also enables the manufacturer of the vehicle to be master of the technology associated with the level sensor and with the computer of the servomotor. The manufacturer can originate the design of the software used to receive and manage the information transmitted by the sensor. The manufacturer will be able to be free to choose what type of sensor he wants to fit according to the type of applications provided by such a type of sensor, the cost and the type of vehicle. The manufacturer will no longer be dependent on the central computer of the central control member in choosing the sensor.

The invention enables the vehicle manufacturer to have a choice as to the placement of the sensor in the tank and above all to have a choice as to the type of sensor to be installed.

The subject of the invention is therefore a hydraulic braking assembly for a vehicle comprising an electric servomotor comprising an electric motor and a computer, the computer being connected to a central control member by a first cable and being used to actuate the electric motor when a brake pedal is actuated by a driver, a master cylinder connected to the servomotor by a support piston actuated by the motor of the servomotor, a hydraulic fluid tank mounted on the master cylinder, said tank communicating with a chamber of the master cylinder to feed the master cylinder with hydraulic fluid, a hydraulic fluid level sensor situated in a wall of the fluid tank to monitor the hydraulic fluid level inside the tank, characterized in that the fluid level sensor is connected from the tank to the computer of the electric servomotor by a connection means.

DETAILED DESCRIPTION

FIG. 2illustrates another hydraulic braking assembly14of a vehicle, according to the invention. As for the hydraulic assembly1described inFIG. 1, this other hydraulic assembly14comprises an electric servomotor15supporting braking (brake booster), a master cylinder16, a hydraulic fluid tank17and at least one hydraulic braking circuit (not represented). The servomotor15comprises an electric motor18and a computer19. The computer19forms an electronic control device and is connected to a battery20. The computer19is also connected to a central control member (not represented). The central control member comprises a dashboard. The computer19can be connected to the dashboard by a CAN-type bus. The computer19is more particularly connected to the central control member via the bus by a first cable

A brake pedal (not represented) is connected to a control rod21, which is in turn mechanically connected to the servomotor15.

The tank17is mounted on the master cylinder16to feed at least one chamber (not represented) of the master cylinder16with fluid. The hydraulic braking assembly connects the chamber of the master cylinder16to a braking device (not represented) mounted on a wheel of a vehicle. The braking device may be a disk brake or even a drum brake.

The electric servomotor15comprises a screw/nut assembly22converting a rotational movement of the rotor-forming nut of the electric motor18into a rotational movement of the screw that displaces a support piston23toward the master cylinder. The servomotor15is actuated by the control rod21displaced by the brake pedal. As for the hydraulic assembly1described inFIG. 1, a force sensor (not represented) measures the force applied to the control rod21by the driver via the brake pedal.

The fluid tank17contains a quantity of fluid for feeding the chamber of the master cylinder16. The tank17feeds the master cylinder with fluid so that the pressure exerted by the support piston23on this fluid can allow a sufficient convergence of the brake pads relative to the disk or relative to the drum plate in order to bring about a braking of the vehicle.

A hydraulic fluid level sensor25is placed inside this tank17. As mentioned previously, this sensor25may be of the REED glass envelope type, or else of the HALL effect type, or any other type of sensor suitable for this type of application.

The level sensor25is placed through the wall of the tank17in a leak-tight manner so that it communicates with the fluid inside the tank17.

According to the invention, the level sensor25is connected to the computer19of the hydraulic assembly14by a second cable26or any other connection means26, rigid or otherwise.

The level sensor25is situated in proximity to the computer19, that is to say that its placement through the wall of the tank17is optimized so that the length of the second cable26which connects the level sensor25to the computer19is as short as possible. In one example, the length of this second cable26is between 2 and 6 cm, preferably 3 cm.

More specifically, the tank17has a face27which faces toward the computer19. The sensor19is housed in a wall of the tank17so that the second cable26leaves from this face27.

When the fluid level reaches a level which is detected by the level sensor25, a signal is produced which is sent from the sensor25to the computer19via the second cable26.

The computer19has first types of circuits28for transmitting the signal from the sensor25to the central control member. It is the central control member which then processes the information.

The computer19may also have second types of circuits29for receiving and processing the signal from the sensor25, these same second types of circuits then transmitting the processed signals to the central control member.

The signal transmitted by the sensor25may then be communicated to the driver via a sound and/or light indicator on the dashboard.