Technical Field

This invention relates to a system that increases the safety and the driving comfort of wheeled vehicles, eliminating the risk of an unintended displacement of the vehicle after a stop. The system can be applied to any type of wheeled vehicle, being particularly well suited for automobiles, trucks, and industrial vehicles.

Background Art When driving a car, releasing the brake after a stop would permit a forward or backward displacement of the vehicle, caused by either gravity, if the surface on which the vehicle stands is not perfectly levelled, or by the engine "push" in automatic-transmission vehicles. The prior art, for the purpose of preventing such a displacement, is either to use the hand brake or to keep the foot on the brake pedal for as long as the vehicle is to be in a still state. In automatic- transmission cars, the driver can also place the shift lever in the "park" (P) position. This can be very inconvenient, especially in a congested traffic, where stops are very frequent, and may not be sufficiently

safe in that a human driver may forget to engage the hand brake or the parking position, or may inadvertently release the brake pedal.

Disclosure of Invention

According to the present invention, there is provided a system that maintains the brake fully engaged after a stop, and releases it automatically when the accelerator pedal is depressed. It will be appreciated that the brake holding device should not be activated when the vehicle is in motion at any significant speed.

In a preferred implementation of the invention, a SPEED SENSOR, a SIGNAL CONVERTER, a BRAKE SENSOR, an ACCELERATOR SENSOR, a PARK SENSOR, an ELECTROVALVE, and a SWITCHING DEVICE are employed.

For the purpose of illustrating the functioning principle, an embodiment of the invention will now be described in greater detail with reference to FIG.l in the accompanying drawings, which includes a SERVICE SWITCH 8 to permit the eventual disconnection of the entire system, and a BATTERY 9 as a source of electrical power.

The SPEED SENSOR 1 supplies an electronic signal

when the vehicle is moving, and no signal when the vehicle is still.

The SIGNAL CONVERTER 2 interprets the signal and absence of signal from the speed sensor and supplies an appropriate DC voltage.

The BRAKE SENSOR 3 closes an electric circuit whenever pressure is applied to the brake hydraulic circuit, and opens the electric circuit when the hydraulic pressure is released.

The ACCELERATOR SENSOR 4 closes an electric circuit whenever the accelerator pedal is depressed, and opens the electric circuit when the lever is placed in any other position. Alternatively, the park sensor closes an electric circuit whenever the parking brake (or hand brake) is fully engaged, and opens the circuit when the parking brake is released.

The ELECTROVALVE 6 holds the hydraulic pressure in the brake system by closing the return of the hydraulic circuit when the valve is energized, and opens the return of the hydraulic circuit when the valve is no longer energized. Ideally, the electrovalve is located

between the master cylinder and the slave cylinder of the brake pump. If this is not feasible, then in vehicles with dual or multiple brake circuits, an electrovalve is required for each circuit. An indicator lamp on the instrument panel is connected to the electrovalve circuit to indicate when the holding device is on.

The SWITCHING DEVICE 7 consists of two single pole-single track relays, one normally open 7a and the other normally closed 7b, connected in series, that command the electrovalve. Solid state relays (SSR) are preferred but electro-magnetic relays (EMR) can also be used. The switching device commands the brake holding device as follows:

a) When the speed of the vehicle is close to zero, the signal converter connected to the speed sensor energizes the relay 7a of the switching device, and the circuit connecting the brake holding device to the power supply is closed. In this condition, if the brake pedal is depressed, pressurizing the hydraulic circuit, and causing the electric circuit of the brake sensor 3 to be closed, the electrovalve 6, connected in series with the brake sensor, is energized, closing the return of the hydraulic circuit, thereby maintaining the brake

engaged .

b) If the accelerator pedal is depressed, causing the circuit of the accelerator sensor 4 to be closed,

95 or if the shift lever is placed in the "park" position or the parking brake is fully engaged, causing the circuit of the park sensor 5 to be closed, the relay 7b is energized and the circuit connecting the electrovalve 6 to the power supply is open, releasing

100 both the electrovalve and the brake.