GB2401260A - Actuator apparatus - Google Patents

Abstract

An actuator apparatus enables simultaneous switching of two solenoid valves (3, 4) in response to an electrical signal generated by either one of two driver circuits (1, 2). The apparatus has particular application in nose dipping systems for motor vehicles.

Description

Actuator Ancaratus This invention relates to an actuator apparatus which

is particularly, though not exclusively, suitable for use in pre-crash nose dipping systems for motor vehicles.

WA-01/26922 discloses a safety arrangement for a motor vehicle wherein the vehicle is equipped with a front suspension arrangement whose height can be automatically lowered when a potential accident situation Is detected. Such safety arrangements are referred to as pre-crash nose dipping systems and typically comprise a sensor for detecting a potential accident situation and for generating a trigger system for controlling the height of the front suspension. The sensor typically receives signals from a forward looking radar mounted on the front of the vehicle. The radar is arranged to detect obstacles in the path of the equipped vehicle and to provide range reformation and closing speed information to the sensor. When a potential accident situation is sensed, the sensor generates a trigger signal which is used to dip the nose of the vehicle. This nose dipping can be achieved by rapidly exhausting air from the air springs of the front suspension arrangement.

Pre-crash nose dipping is particularly beneficial when used on "high" vehicles such as sport utility vehicles. As such vehicles have a comparatively high ground clearance, their bumpers are higher than those fitted to a conventional car. Thus during a frontal impact between a sport utility vehicle and a conventional vehicle, the bumpers do not engage.

Also, in the case of a side impact, the sport utility vehicle's bumpers do not engage with the reinforced floor pan but rather with the door or side panel. Damage can be lessened if the sport utility vehicle's bumpers can be aligned with the bumpers or floor pan of a conventional car. Pre- crash nose dipping systems aim to achieve this.

Dipping of the front suspension arrangement can be done by opening actuator valves which control the air springs on either side of the front suspension arrangement. When dipping the suspension under pre-crash nose dipping conditions, it is important that both - 2 left and right front suspension arrangements are dipped simultaneously. If only one side is dipped then this could affect stability of the equipped vehicle. It also preferable that the suspension is not dipped when no potential accident situation is detected, that is, the suspension actuating mechanism must be immune to false activations. False activations may be caused by short circuits or open circuits between a sensor and the suspension actuator valves. Suddenly dipping the front of the vehicle when no potential accident situation exists could also affect vehicle stability.

According to the present invention there is provided actuator apparatus including first and second driver circuits and first and second magnetically operated switches, wherein the magnetically operated switches each include first and second independent windings on a common former, and wherein the first driver circuit and first windings of each first and second switches are connected in series to form a first actuator circuit, and the second driver circuit and second windings of each first and second switches are connected in series to form a second actuator circuit electrically isolated from the first actuator circuit.

By virtue of this arrangement, turning on either one (or both) of the driver circuits will result in activation of both switches.

This is particularly advantageous when the apparatus is used to control nose dipping of a vehicle as it permits either a left hand sensor associated with a radar mounted towards the left hand side of the vehicle, or a right hand sensor associated with a radar mounted to the right hand side of the vehicle to dip the vehicle independently of the other.

Preferably, a diode is placed across each winding in order to limit the back EMF that is generated when each winding is de-energised.

Preferably, the first and second windings of each switch are wound on separate sections of the common former rather than on top of one another, in order to ensure the maximum possible electrical isolation. - 3

In one embodiment, a diagnostic system is incorporated in at least one, and preferably each driver circuit so that a single short circuit or open circuit can be detected.

An embodiment of the invention will now be described, by way of example only, with reference to the drawings of which; Fig. 1 is a circuit diagram of actuator apparatus in accordance with a preferred embodiment, and Fig. 2 is a circuit diagram of a diagnostic system incorporated in the apparatus of Fig. 1.

In Fig. 1, a right hand driver circuit 1 and a left hand driver circuit 2 are each l O connected with a right solenoid valve 3 and a left hand solenoid valve 4, respectively. rS Each solenoid valve 3, 4 is provided with a pair of coils 5, 6 and 7, 8 wound on a split former. This arrangement permits a current in either coil of either pair to actuate the solenoid even while the other coil of the pair is de-energised.

The right hand driver circuit 1 and a first coil of each pair of coils associated with both right hand and left hand valves 3, 4 are all connected in series. Similarly, the left hand driver circuit 2 and the other coil of each pair of coils associated with both right and left hand valves 3, 4 are all connected in series. Hence two isolated electrical circuits are provided, each capable of operating both solenoid valves 3, 4 in response to a trigger signal produced in either driver circuit 1, 2.

A diode 9 for limiting back EMF is connected across each coil 5, 6, 7, 8.

In a preferred embodiment, there is provided a diagnostic system so that malfunction of an actuator circuit can be detected. Each driver circuit 1, 2 is thus provided with a "Hl" output, a "LO" output and a "SENSE" input, with its associated coils being connected in series between high and low outputs, and the sense input being taken from a point at the junction of the coils. In a test mode the driver circuits 1, 2 can periodically check for circuit malfunction. Each one does this by temporarily setting its HI output to the low impedance state and verifying that the SENSE input responds in the appropriate manner. It then returns the HI output to the high impedance state. The apparatus then repeats the process with the LO output.

This procedure may be implemented using the transistor circuitry and voltage sensing device 10 of Fig. 2. Transistor T1 is turned on for a short period of time and any current flowing through the coil 7 is detected by monitoring voltage changes at the "SENSE" input.

Next, the transistor T2 is turned on for a short period of time and the SENSE input is monitored once more for detecting current flow through coil 5. In this way, malfunction of either coil circuit can be detected. Short pulses of current through either coil 5, 7 during the test procedure will not cause mechanical movement of the solenoid valves 3, 4, which have a finite response time. So if inputs A or B are set to energise their respective transistors, current through either coil will start to rise exponentially to a level sufficient to be detected by the device 10 but not sufficient to activate the valve. Both transistors T1, T2 are turned on for a relatively long period of time when activation of the solenoid valves 3, 4 is desired.

The actuator apparatus of Fig. 1 with or without the diagnostic system of Fig. 2 can readily be incorporated in a pre-crash nose dipping system. In such a case, the right hand and left hand driver circuits 1, 2 are each associated with right and left hand sensors (11 and 12 respectively) fitted to a vehicle (not shown). Each sensor incorporates a radar.

Having two radars positioned at opposite ends of a front bumper for example, enables a pre-crash nose dipping system to "see" obstacles across a large section in front of the equipped vehicle. Each sensor can then function independently of the other in order to detect potential collision targets in its field of view.

When either left or right hand sensors detect that a potential collision situation is imminent and that nose dipping should be initiated, either one (or both) sensors instructs its associated driver circuit to generate a trigger signal. This generated trigger signal drives a current through the coils associated with the driver circuit for activation of the solenoid valves 3, 4..

The solenoid valves 3, 4 are incorporated in front suspension air springs located to the right and to the left of the vehicle respectively. When the valves are activated, air is rapidly released from each air spring causing the nose of the vehicle to dip.

Any malfunction of the circuitry of Fig. 1 which had been detected during the aforementioned test mode can be used to trigger a mechanism (not shown) for safe shut- down of the pre-crash nose-dipping system.

Although the actuator apparatus of Figs 1 and 2 has been described in the context of pre-crash nose dipping, the apparatus is not restricted to this application and could be usefully employed in other electrically operated systems. Further, more than two driver circuits and actuator valves can be utilised.

Advantageously, because the coils connected to one driver circuit are connected in series, one actuator valve cannot be fired without firing the other one at the same time. In addition, because each actuator circuit is isolated from the other by virtue of the split bobbin design, extra failure modes involving inadvertent interconnection of the two firing circuits are avoided.

Hence the invention can be utilised for any system requiring high integrity control of multiple actuators. - 6

Claims (10)

1. Actuator apparatus including first and second driver circuits and first and second magnetically operated switches, wherein the magnetically operated switches each include first and second independent windings on a common former, and wherein the first driver circuit and first windings of each first and second switches are connected in series to form a first actuator circuit, and the second driver circuit and second windings of each first and second switches are connected in series to form a second actuator circuit, electrically isolated from the first actuator circuit.

2. Actuator apparatus as claimed in claim 1 and further comprising a diode connected across each winding.

3. Actuator apparatus as claimed in either preceding claim wherein the first and second windings are wound on separate sections of the common former.

4. Actuator apparatus as claimed in any preceding claim in which at least one of the driver circuits incorporates a diagnostic system for detecting malfunction of an actuator circuit.

5. Actuator apparatus as claimed in claim 4 in which the diagnostic system includes means for feeding current through each winding independently of the other and means for detecting current flow.

6. Actuator apparatus as claimed in claim 5 including a pair of transistors, each of which being switchable independently of the other and each for feeding a current to either one of the first and second windings.

7. A nose dipping actuation system for a vehicle comprising the actuator apparatus of any preceding claim. - 7

8. A nose dipping actuation system for a vehicle including a first forward looking vehicle mounted sensor and a second forward looking vehicle mounted sensor wherein each sensor is adapted to generate a trigger signal under pre-determined conditions of the vehicle and on sensing an object ahead of the vehicle, wherein the actuation system further includes a first driver circuit connected to the first sensor and adapted to receive a trigger signal therefrom, a second driver connected to the second sensor and adapted to receive a trigger signal therefrom, first and second magnetically operated switches, wherein the magnetically operated switches each include first and second independent windings on a common former, and wherein the first driver circuit and first windings of each first and second switches are connected in series to form a first actuator circuit, and the second driver circuit and second windings of each first and second switches are connected in series to form a second actuator circuit, electrically isolated from the first actuator circuit, and wherein the first and second switches are incorporated in first and second adjustment means respectively which are adapted to adjust the height of the front of the vehicle, whereby on receipt of a trigger signal by either driver circuit, both switches are activated, whereupon the front of the vehicle is lowered.

9. A vehicle including the nose dipping actuation system of either of claims 7 or 8.

10.Actuator apparatus substantially as hereinbefore described with reference to the drawings.