Suspension system

The invention detects at least either one of a supply fault and a ground fault distinctively from a disconnection. A compressor relay 22 is placed between a battery 21 and an air compressor module 5. The compressor relay 22 controls the drive and stop of the air compressor module 5. A compressor driver 26 outputs a drive signal to the compressor relay 22. A ground-side voltage monitor 28 detects the drive voltage of the compressor relay 22. A pressure sensor 17 detects air pressure in a discharge side of the air compressor module 5. A microcomputer 30 of a controller 25 detects a ground fault and a disconnection of the drive signal of the compressor 22 distinctively from each other on the basis of a voltage value Vg detected by the ground-side voltage monitor 28 and a pressure valve P detected by the pressure sensor 17.

TECHNICAL FIELD

The invention relates to suspension systems suitable for being installed in vehicles, such as four-wheeled vehicles.

BACKGROUND ART

Air suspension systems are one of the known suspension systems. An air suspension system includes an air compressor, an air suspension body, and a plurality of valves. In the air suspension system, the valves determine flow passages. The air compressor pressurizes and supplies air to the air suspension body to raise vehicle height, and the air is discharged from the air suspension body to lower the vehicle height.

Electric instruments installed in a vehicle are equipped with various types of failure detectors (see Patent Literature 1, for example). The Patent Literature 1 discloses a system including current source circuits for detecting failures, and current detection devices for detecting the current of the circuits. The system makes a comparison with proper two reference currents and distinguishes between a normal operation, a disconnection failure, and a ground fault failure.

CITATION LIST

Patent Literature

SUMMARY Of INVENTION

Technical Problem

When an air suspension system has, for example, a disconnection in a drive circuit of an electric motor which is used in an air compressor, the air compressor is stopped. This discontinues she compressed air supply to an air suspension body, so that vehicle height is not raised. If the system has a ground fault in the drive circuit of the electric motor, the air compressor is driven. The compressed air is therefore supplied to the air suspension body, which raises the vehicle height. In this way, the air compressor and the air suspension body each behave differently between when a disconnection occurs and when a ground fault occurs. This makes it possible to implement control appropriate to each case. The same can be said for a disconnection and a supply fault. However, conventional suspension systems do not distinguish a disconnection, a ground fault, and a supply fault from one another, and the whole systems stop in any of these cases.

The failure detector discussed in the Patent Literature 1 needs to be provided with a separate current source circuit or the like in order to detect a disconnection failure and a ground fault failure distinctively from each other. This causes the problem that production cost is increased.

An object of the invention is to provide a suspension system capable of detecting at least either one of a supply fault and a ground fault distinctively from a disconnection.

Solution to Problem

A suspension system according to one embodiment of the invention includes a battery installed in a vehicle; a fluid power pump operated by being powered by the battery; a relay connecting the battery and the fluid power pump; fluid power suspension bodies mounted on a plurality of wheels of the vehicle; supply/exhaust valves placed between the fluid power pump and the respective fluid power suspension bodies; an exhaust valve configured to discharge a working fluid in a discharge side of the fluid power pump; a pressure detection device configured to detect pressure of the working fluid in the discharge side of the fluid power pump; a relay driving device configured to output a drive signal to the relay; a voltage detection device configured to detect drive voltage of she relay; a vehicle behavior detection device configured to detect behavior of the vehicle; and a control device. The control device includes a failure determination device configured to detect at least either one of a supply fault and a ground fault of the drive signal of the relay distinctively from a disconnection on the basis of a voltage value detected by the voltage detection device and a pressure value detected by the pressure detection device.

The one embodiment of the invention makes it possible to detect at least either one of a supply fault and a ground fault distinctively from a disconnection.

DESCRIPTION OF EMBODIMENTS

An air suspension system as a suspension system according to embodiments of the invention will be explained in details with reference to the attached drawings, taking as an example a situation where the system is installed in a vehicle, such as a four-wheeled vehicle.

FIGS. 1 to 6show a first embodiment of the invention. InFIG. 1, left-front and right-front wheels2A and2B (front wheels) and left-rear and right-rear wheels2C and2D (rear wheels) are disposed under (on a road side of) a vehicle body1comprising a body of the vehicle.

Air suspensions3configure fluid (oil and/or air) power suspension bodies. The air suspensions3are provided to the four wheels2A to2D of the vehicle. More specifically, the air suspensions3are interposed between the vehicle body1and the wheels2A to2D in the vehicle. The air suspensions3include four air suspensions3so as to correspond to the four wheels2A to2D (FIG. 2shows only two of the four wheels). The air suspensions3each include an air spring4, The air suspensions3tire configured to supply or discharge air as a working fluid to adjust vehicle height of the vehicle1.

When compressed air is supplied or discharged through diverging conduits14A to14D and supply/exhaust valves15, described later, the air springs4vertically expand or contract in accordance with a supply or discharge amount (air amount). This causes the air suspensions3to individually perform the vehicle height adjustment of the vehicle1, so that the vehicle height is raised or lowered with respect to each of the wheels2A to2D.

An air compressor module5includes an air compressor6and an electric motor7, and configures a fluid power pump operated by being powered by a battery21. The air compressor module5is installed, for example, in a rear part of the vehicle1, and supplies compressed air to the air springs4of the air suspensions3.

The air compressor6comprises, for example, a reciprocating compressor, a scroll compressor or the like. Check valves6A are respectively placed on an intake side and a discharge side of the air compressor6. The air compressor6is driven by the electric motor7functioning as a drive source. The air compressor6compresses external or atmospheric air which is sucked from an intake filter8side, to thereby generate compressed air (air). The intake filter8also serves as a silencer for reducing noises generated during the air suction.

A supply/exhaust conduit9is connected to the discharge side of the air compressor6. As shown inFIG. 2, the supply/exhaust conduit9is connected to the discharge side of the air compressor6in one side (proximal end side) and extends to outside the air compressor module5in the other side (distal end side). Connected to the distal end side of the supply/exhaust conduit9are the after-mentioned diverging conduits14A to14D.

An air dryer10is interposed in the supply/exhaust conduit9. The air dryer10is configured to dry air. The air dryer10contains, for example, a moisture absorbing agent, not shown, or the like. The air dryer10is disposed between a slow return valve11and an exhaust conduit13described later. The slow return valve11includes a parallel circuit formed of a throttle11A and a check valve11B. The check valve11B opens to a forward flow which travels from the air compressor6toward the air suspensions3, and does not reduce a flow rate of the compressed air. However, the check valve11B is closed to a backward flow, and the flow rate of the compressed air is reduced by the throttle11A. The compressed air then slowly flows backward at a low flow rate.

When the compressed air created in the air compressor6forwardly flows in the direction of the air suspensions3, the air dryer10brings the compressed air into contact with the moisture absorbing agent located inside to absorb moisture. The air dryer10then supplies the dried compressed air toward the air springs4. When the compressed air discharged from she air springs4(exhaust air) flows backward within the air dryer10, the air which flows backward within the air dryer10is dried air. During this time, the dried air desorbs the moisture of the moisture absorbing agent in the air dryer10. The moisture absorbing agent is thus regenerated and recovers a moisture absorbable condition.

An exhaust valve12(air release valve) discharges air (working fluid) existing in a discharge side of the air compressor module5(air compressor6). The exhaust valve12is connected to the supply/exhaust conduit9through the exhaust conduit13. The exhaust valve12includes a solenoid (coil)12A. The exhaust valve12comprises, for example, a 2-port 2-position electromagnetic switching valve (spring-offset normally closed valve). The exhaust valve12is normally closed to block the exhaust conduit13. When the solenoid124of the exhaust valve12is energized by a controller25to be excited, the exhaust valve12is opened to bring the exhaust conduit13into communication. The exhaust valve12thus discharges (releases) the compressed air existing in the supply/exhaust conduit9into the atmosphere.

The diverging conduits14A to14D are formed by dividing the supply/exhaust conduit9into four correspondingly to the wheels2A to2D and extend toward the air suspensions3of the wheels2A to2D. The four diverging conduits14A to14D connect, the air compressor module5to the air springs4of the air suspensions3. The diverging conduits14A to14D diverge at a tip of the supply/exhaust conduit9to connect the air springs4to the supply/exhaust conduit9.

The supply/exhaust valves15(supply-and-exhaust valves) are placed between the air compressor module5and the respective air suspensions3. To be specific, the supply/exhaust valves15are placed in the four diverging conduits14A to14D so as to be located between the air compressor6of the air compressor module5and the air springs4of the air suspensions3. Each of the supply exhaust valves15is configured in the same manner as the exhaust valve12. The supply exhaust valve15therefore includes a solenoid15A and comprises, for example, a 2-port 2-position electromagnetic switching valve, in this case, the supply exhaust valve15is configured as a spring-offset normally closed valve. The present embodiment employs the supply exhaust valves15each in which an air supply valve and an air exhaust valve are integral with each other. However, the air supply valve and the air exhaust valve may be separately provided.

The solenoids15A are electrically connected to the controller25. When the solenoids15A are powered by the controller25, the supply/exhaust valves15suction (displace) plungers, not shown, against spring force to be opened. In this open valve state, the compressed air can be supplied to or discharged from the corresponding air suspensions3. When the power supply to the solenoids15A is discontinued, the supply/exhaust valves15are closed due to the spring force. This closed valve state allows the supply/exhaust valves15to discontinue the compressed air supply or discharge to or from the air suspensions3.

Each of the air suspensions3is provided with a vehicle height sensor16. The vehicle height sensor16configures a vehicle behavior detection device for detecting behavior of a vehicle. Each of the vehicle height sensors16detects the vehicle height of the corresponding air suspension3on the basis of a length dimension (vertical dimension) of the air spring4in a direction where the air spring4expands or contracts, the vehicle height sensor16then outputs a detection signal of the vehicle height to a microcomputer30of the controller25. The detection signal comprising an analogue signal, which is outputted from the vehicle height sensor16, is converted into a digital signal by an A/D converter31installed in the microcomputer30. The detection signal is then inputted to the microcomputer30.

The supply/exhaust conduit9is provided with a pressure sensor17. The pressure sensor17is placed between the slow return valve11and the supply/exhaust valves15. The pressure sensor17configures a pressure detection device and detects a pressure value P of the compressed air (air) existing in the discharge side of the air compressor module5(air compressor6). More precisely, the pressure sensor17detects the pressure value P of the compressed air supplied to the air springs4. The pressure sensor17then outputs a detection signal of the pressure value P to the microcomputer30of the controller25. The detection signal comprising the analogue signal, which is outputted from the pressure sensor17, is converted into a digital signal by the A/D converter31installed in the microcomputer30. The detection signal is then inputted to the microcomputer30.

An electric circuit for driving the air compressor6and the electric motor7will be now discussed with reference toFIG. 3.

The battery21is installed in the vehicle. The battery21, which works as a power source, is connected with a positive terminal of the electric motor7via a compressor relay22and a fuse23. A negative terminal of the electric motor7is connected to the ground. The positive and negative terminals of the electric motor7are connected with a choke coil7A for preventing or reducing inrush current or the like. The positive terminal of the electric motor7is further connected to a thermal relay24at a position between the choke coil7A and the battery21(seeFIG. 2).

As shown inFIG. 3, the compressor relay22(relay) connects the battery21and the air compressor module5. The compressor relay22includes a coil22A and a junction22B. The junction22B of the compressor relay22is normally off. When the coil22A of the compressor relay22is supplied with current, the junction22B is switched on. When the junction22B is turned on, the compressor relay22connects the battery21and the electric motor7of the air compressor module5.

The coil22A is connected to the battery21in one end via the controller25. The other end of the coil22A is connected to the ground via the controller25.

The controller25controls the driving of the electric motor7and also controls the opening and closing of the supply/exhaust valves15and those of the exhaust valve12. The controller25includes a compressor driver26, a fail-safe relay27(hereinafter, referred to as FS relay27), voltage monitors28and29, the microcomputer30, etc.

The controller25has a battery-side terminal25A which is connected to the one end of the coil22A of the compressor relay22. The controller25has a ground-side terminal25B which is connected to the other end of the coil22A of the compressor relay22.

The compressor driver26configures a relay driving device configured to output a drive signal to the compressor relay22. The compressor driver26is connected to a downstream side of the compressor relay22. In particular, the compressor driver26is connected to the ground-side terminal25B in one end and connected to the ground in the other end. The compressor driver26includes an overcurrent protection circuit26A and a switching circuit26B. The overcurrent protection circuit26A comprises, for example, a resistor for detecting overcurrent, a comparator, etc. If overcurrent flows to the coil22A, the overcurrent protection circuit26A detects the overcurrent.

The switching circuit26B includes a switching element, such as an n-type MOSFET. The switching circuit26B is disposed, for example, so as to be connected in series to an upstream side of the overcurrent protection circuit26A. In response to a control signal from the microcomputer30and a detection signal from the overcurrent protection circuit26A, the switching circuit26B connects or disconnects the ground-side terminal25B to or from the ground. When the switching circuit26B comes into connection, the compressor driver26supplies the coil22A with a relay current as a drive signal.

The PS relay27configures another relay driving device which outputs a drive signal to the compressor relay22. The FS relay27is connected to either an upstream side or the downstream side of the compressor relay22, whichever is opposite to the compressor driver26. In this case, the FS relay27is connected to the upstream side of the compressor relay22. The FS relay27is configured in substantially the same manner as the compressor relay22. The FS relay27is connected to the battery-side terminal25A in one end and connected to the battery21in the other end. The FS relay27has a control terminal which is connected to an I/O port32of the microcomputer30. In response to the control signal from the microcomputer30, the FS relay27is switched between an ON state which connects the batter-side terminal25A to the battery21and an OFF state which disconnects the battery-side terminal25A from the battery21.

The ground-side voltage monitor28is connected to the downstream side of the compressor relay22. The ground-side voltage monitor28detects a voltage value Vg of the ground-side terminal25B as a voltage value on a downstream side of the coil22A. An input side of the ground-side voltage monitor28is connected in between the compressor driver26and the ground-side terminal25B. An output side of the ground-side voltage monitor28is connected to the microcomputer30. The ground-side voltage monitor28outputs to the microcomputer30a detection signal according to the voltage value Vg of the ground-side terminal25B. The detection signal comprising an analogue signal, which is outputted from the ground-side voltage monitor28, is converted into a digital signal by the A/D converter31installed in the microcomputer30. The detection signal is then inputted to the microcomputer30.

The battery-side voltage monitor29is connected to the upstream side of the compressor relay22. The battery-side voltage monitor29detects a voltage value Vb of the battery-side terminal25A as voltage on the upstream side of the coil22A. An input side of the battery-side voltage monitor29is connected in between the FS relay27and the battery-side terminal25A. An output side of the battery-side voltage monitor29is connected to the microcomputer30. The battery-side voltage monitor29outputs to the microcomputer30a detection signal corresponding to the voltage value Vb of the battery-side terminal25A. The detection signal comprising an analogue signal, which is outputted from the batter-side voltage monitor29, is converted into a digital signal by the A/D converter31installed in the microcomputer30. The detection signal is then inputted to the microcomputer30. The voltage monitors28and29configure voltage detection devices which detect drive voltage of the compressor relay22.

The microcomputer30configures a control device. The microcomputer30controls the drive and stop of the air compressor module5comprising the air compressor6and the electric motor. The microcomputer30further controls the opening and closing of the exhaust valve12and those of the supply/exhaust valve15. An input side of the microcomputer30connected with the vehicle height sensor16, the pressure sensor1and the voltage monitors28and29. An output side of the microcomputer30is connected to the FS relay27and the compressor driver26.

The microcomputer30includes a memory section30A comprising, for example, a ROM a RAM, a non-volatile memory, etc. The memory section30A stores, for example, a program for air suspension control processing which is illustrated inFIGS. 4 and 5. The microcomputer30executes the program stored in the memory section30A. The microcomputer30thus controls the air suspensions3to adjust the vehicle height of the vehicle. More specifically, the microcomputer30controls the current supplied to the electric motor7in accordance with the detection signals inputted from the vehicle height sensor16, the pressure sensor17, and the like. The microcomputer30further controls the current supplied to the solenoid12A of the exhaust valve12and the current supplied to the solenoid15A of the supply/exhaust valve15.

The microcomputer30includes a failure determination device. When executing the air suspension control processing described later, the microcomputer30detects a ground fault of the drive signal of the compressor relay22distinctively from, a disconnection on the basis of the voltage value Vg detected by the ground-side voltage monitor28and the pressure value P detected by the pressure sensor17.

Discussed below with reference toFIGS. 4 and 5is the air suspension control processing including vehicle height adjustment processing by the microcomputer30. The air suspension control processing inFIGS. 4 and 5is repeatedly executed at preset time intervals.

A Step1makes a determination as to whether a disconnection is detected. For example, in failure situations of various kinds, failure codes corresponding to the respective failure situations are stored in the memory section30A of the microcomputer30. The microcomputer30reads out the failure codes from the memory section30A and determines whether the failure code corresponding to a disconnection failure is stored. If the determination in the Step1is “YES,” the microcomputer30has already detected the disconnection occurrence in connection lines including the coil22A of the compressor relay22. The routine then moves to a Step9. The Step9executes processing for the case where a disconnection is confirmed.

If the determination in the Step1is “NO,” the microcomputer30has not set detected any disconnection. The routine therefore moves to a Step2. The FS relay27is brought into the ON state (connected state), and the compressor driver26into the OFF state disconnected state). In this state, the microcomputer30reads the voltage value Vg detected by the ground-side voltage monitor28. In a subsequent Step3, it is determined whether the voltage value Vg is Low, that is, whether the voltage value Vg of the ground-side terminal25B is in the vicinity of the ground (0[V], for example).

At this moment, the FS relay27is ON, and the compressor driver26is OFF, so that the connection lines including the coil22A are connected to the battery21. In a normal state (ordinary state) where the drive signal (relay current) is supplied, the voltage value Vg of the ground-side terminal25B is in the vicinity of supply voltage from the battery21. In a disconnection state where the connection lines including the coil22A are disconnected or in a ground fault state where the downstream side of the coil22A is connected to the ground, the voltage value Vg of the ground-side terminal25B is in the vicinity of the ground.

If the determination in the Step3is “NO” the voltage value Vg is in the vicinity of the supply voltage from the battery21, meaning that the voltage value Vg is High. The connection lines including the coil22A are therefore determined to be in the normal state, and the routine moves to a Step4. In the Step4, the microcomputer30executes a normal control mode and outputs a target value of the vehicle height in order to adjust the vehicle height of the vehicle according to the vehicle height outputted from the vehicle height sensor16, and the like. At this point of time, the microcomputer30clears the failure codes relating to a disconnection failure and a short circuit failure.

A subsequent Step10calculates a control command for controlling the air compressor6, the exhaust valve12, and the supply/exhaust valve15in accordance with the target value of the vehicle height. The control command (control signal) calculated in the Step10is outputted to the compressor driver26, the solenoid12A of the exhaust valve12, and the solenoid15A of the supply/exhaust valve15in a Step11. This enables the controller25to open or close the exhaust valve12and the supply-exhaust valve15to raise or lower the vehicle height of the vehicle to the target value while the air compressor6is in operation or at rest.

If the determination of the Step3is “YES,” the voltage value Vg is in the vicinity of the ground, which means that the voltage value Vg is Low. It is then determined that there is a disconnection or a ground fault in the connection lines including the coil22A. The routine therefore moves to the Step5. The Step5starts ground fault/disconnection distinguishing control. The microcomputer30closes both the exhaust valve12and the supply/exhaust valve15in response to the control, signal outputted to the solenoids12A and15A. In a subsequent Step6, the microcomputer30turns on the FS relay27and turns off the compressor driver26.

A Step7makes a determination as to whether the pressure value P detected by the pressure sensor17has been increased. To be more specific, the microcomputer30determines whether the pressure value P has been increased beyond a predetermined pressure difference ΔP since the beginning of the ground fault/disconnection distinguishing control. Alternatively, the microcomputer30may determine whether the pressure value P has been increased beyond, for example, a predetermined threshold value, instead of the pressure difference ΔP.

If the determination of the Step7is “NO,” the connection lines including the coil22A are determined to be disconnected. It is therefore also determined that the compressor relay22is in the OFF state, and thus that the air compressor6is at rest. The routine moves to a Step8. The Step8executes disconnection confirming processing and stores the failure code corresponding to a disconnection into the memory section30A.

In the subsequent Step9, the microcomputer30executes a limitation control authorization mode and controls the vehicle height adjustment only if the situation is likely to render the vehicle defective. For example, if the vehicle height is high while the vehicle is traveling on an expressway, the vehicle height needs to be lowered, to improve the driving stability of the vehicle. For another example, if the vehicle is unloaded in a garage, and the vehicle height is raised to make the vehicle contact the ceiling of the garage, it is necessary to lower the vehicle height. The microcomputer30then outputs the target value of the vehicle height in order to adjust the vehicle height of the vehicle according to the vehicle height outputted from the vehicle height sensor16, and the like. The routine then moves to the Step10. The Step10calculates the control command for controlling the air compressor6, the exhaust valve12, and the supply/exhaust valve15on the basis of the target value. The control command (control signal) calculated in the Step10is outputted by the Step11to the compressor driver26, the solenoid12A of the exhaust valve12, and the solenoid15A of the supply/exhaust valve15. This enables the controller25to implement air exhaustion control which opens the exhaust valve12and the supply/exhaust valve15, and lower the vehicle height of the vehicle to the target value while the air compressor6is at rest.

If the determination of the Step7is “YES,” the air compressor6is in operation. It is therefore determined that the downstream side of the coil22A is connected to the ground, and that there is the ground failure. The routine then moves to a Step12. If the Step12executes ground failure confirming processing and stores the failure code corresponding to a ground failure in the memory section30A.

A subsequent Step13executes a fail-safe mode (hereinafter, referred to as an FS mode) and opens the exhaust valve12to reduce the pressure value P in the discharge side of the air compressor6to a predetermined value which is previously determined. For example, when the pressure value P is decreased to the predetermined value or after the exhaust valve12is open for a predetermined time period, the microcomputer30outputs a power-off request for discontinuing the power supply from the battery21. The vehicle height needs to be raised if the compressed air in the air springs4has predetermined or lower pressure or if a vehicle bottom touches snow on a road. The FS mode implements control for raising the vehicle height to a limited extent if the vehicle height is lower than a predetermined value or if the vehicle bottom touches a road surface or stones. To be more precise, the microcomputer30outputs the target value of the vehicle height in order to adjust the vehicle height of the vehicle according to the vehicle height, outputted from the vehicle height sensor16, and the like. The microcomputer30then opens the supply exhaust valve15to turn on the FS relay27and thus implements air supply control. This makes it possible to raise the vehicle until the target value is reached.

A Step14makes a determination as to whether the power-off request has been outputted. If the determination of the Step14is “NO,” the processing of the Step13is continued. If the determination of the Step14is “YES,” the power off request has been outputted, and therefore, the routine moves to a Step15. In the Step15, the microcomputer30outputs a control signal to the FS relay27and switches the FS relay21into an OFF state (disconnected state), resulting in a disconnection between the upstream side of the coil22A and the battery21. The coil22A of the compressor relay22is accordingly not supplied with power even in a ground fault state, which turns off the compressor relay22and stops the air compressor6.

A detection behavior of the microcomputer30for detecting a ground fault and a disconnection will be now explained with reference toFIGS. 3 and 6.

If both the compressor driver26and the FS relay2are turned or in the ordinary state (normal state), a normal current 10 [A] flows to the coil22A of the compressor relay22to turn on the compressor relay22, driving the air compressor6. This allows the compressed air to be supplied from the air compressor module5to the air suspensions3. If the compressor driver26is switched off, the coil22A of the compressor relay22is not supplied with current, which turns off the compressor relay22and slops the air compressor6.

Let us assume, for example, that a ground fault or a disconnection has occurred in the middle (“A” point onFIG. 3) between the coil22A and the ground-side terminal25B, which is located on the downstream, side of the coil22A of the compressor relay22. Regardless of whether what has occurred is a ground fault or a disconnection, the voltage on the downstream side of the coil22A of the compressor relay22becomes 0[V]. The microcomputer30therefore detects the occurrence of a ground fault or a disconnection on the basis of the voltage value Vg detected, by the ground-side voltage monitor28.

When making a failure determination, the microcomputer30turns on the FS relay27and turns off the compressor driver26. As shown inFIG. 6, in the ordinary state where the drive signal of the compressor relay22is normal, the voltage value Vg detected by the ground-side voltage monitor28is in the vicinity of supply voltage from the battery21, meaning that the voltage value Vg is High. In the case of either a ground fault or a disconnection, the voltage value Vg detected by the ground-side voltage monitor28comes close to 0[V], which means that the voltage value Vg becomes Low. Therefore, when the voltage value Vg detected by the ground-side voltage monitor28becomes Low, it can be determined that either a ground fault or a disconnection has occurred.

When a ground fault occurs, a ground-limit current If1[A] flows to the coil22A of the compressor relay22to turn on the compressor relay22. She air compressor6is driven even if the vehicle height adjustment control is not carried out (the supply/exhaust valve15and the exhaust valve12are closed). This increases the pressure value P in a discharge-side portion of the air compressor6within the air compressor module5.

In the event of a disconnection, current does not flows to the coil22A of the compressor relay22, so that the compressor relay22comes into the OFF state. Since the air compressor6is suspended in such a case, the pressure value P is not increased unlike in the ease of ground faults. The microcomputer30thus detects a ground fault and a disconnection distinctively from each other on the basis of whether or not the pressure value P is increased.

In this way, according to the air suspension system of the first embodiment, the microcomputer30detects a ground fault of the drive signal of the compressor relay22distinctively from a disconnection on the basis of the voltage value Vg detected by the ground-side voltage monitor28and the pressure value P detected by the pressure sensor17. The air suspension system is capable of distinguishing between a ground fault failure and a disconnection failure when a failure occurs in the drive signal of the compressor relay22. This reduces a cost burden at repair plants.

The microcomputer30detects a ground fault failure and a disconnection failure distinctively from each other on the basis of the voltage value Vg detected by the ground-side voltage monitor28and the pressure value P detected by the pressure sensor17without using current which can be used as a drive signal of the compressor relay22. This eliminates the necessity of installation of a current monitor circuit in an electronic control unit (ECU) which comprises the controller25and the other devices. It is then possible to reduce a unit cost of the ECU and thus cut the production cost.

The compressor driver26and the ground-side voltage monitor28are connected to the downstream side of the compressor relay22. The microcomputer30detects a disconnection and a ground fault of the drive signal of the compressor relay22distinctively from each other. Therefore, if the compressor driver26is turned off while the upstream side of the compressor relay22is connected to the battery21, this makes it possible to detect the occurrence of a disconnection failure or a ground fault failure of the drive signal of the compressor relay22on the basis of the voltage value Vg detected by the ground-side voltage monitor28.

In addition, if the compressor driver26is turned off while the upstream side of the compressor relay22is connected to the battery21, the compressor relay22comes into either the ON state or the OFF state, depending on whether a failure is a disconnection or a ground fault. This enables the microcomputer30to detect a disconnection and a ground fault of the drive signal of the compressor relay22distinctively from each other on the basis of whether or not the pressure value P detected by the pressure sensor17is increased.

Upon detection of a disconnection, the microcomputer30implements control for lowering the vehicle height of the vehicle. If a disconnection occurs in the drive signal of the compressor relay22, the air compressor6cannot be driven. However, the air exhaustion control can be implemented to discharge the compressed air from the air suspensions5. This makes it possible to implement the vehicle height control for lowering the vehicle height according to vehicle conditions.

Upon detection of a ground fault, the microcomputer30turns on the FS relay27, which allows the air compressor6to be driven. This makes it possible to implement the vehicle height control for raising or lowering the vehicle height according to vehicle conditions.

FIGS. 3, 7 and 8show a second embodiment of the invention. The second embodiment is characterized in that a pressure value in a discharge side of an air compressor is previously reduced at the time of detecting a ground fault and a disconnection distinctively from each other. In the second embodiment, the same constituent elements as those of the first embodiment will be provided with the same reference marks, and description thereof will be omitted.

FIG. 7shows a part of air suspension control processing according to the second embodiment. As in the first embodiment a microcomputer30repeatedly executes the air suspension control processing shown inFIGS. 7 and 5at preset time intervals.

The air suspension control processing of the second embodiment is substantially the same as the air suspension control processing of the first embodiment. However, in the second embodiment, if the determination of the Step3is “YES,” pressure reduction processing of a Step21is executed before the start of the ground fault/disconnection distinguishing control in the Step5. In this respect, the second embodiment differs from the first.

In the pressure reduction processing of the Step21, the microcomputer30makes a determination as to whether a pressure value P in a discharge side of an air compressor6is higher than a predetermined upper limit Ph. If the pressure value P is higher than the upper limit Ph, initial air exhaustion control is implemented to reduce the pressure value P to, for example, a value that is roughly equal to atmospheric pressure. More specifically, the initial air exhaustion control opens an exhaust valve12with a supply/exhaust valve15closed. Compressed air is thus discharged from the discharge side of the air compressor6, and the pressure-value P detected by a pressure sensor17is accordingly reduced. When the pressure value P is reduced to a predetermined value which is previously determined or after the exhaust valve12is open for a predetermined time period, the routine moves to the Step5. The microcomputer30closes both the exhaust valve12and the supply/exhaust valve15and starts the ground fault/disconnection distinguishing control.

According to the second embodiment, the pressure reduction processing described above is executed when the ground fault/disconnection distinguishing control is implemented. This pressure reduction processing, as shown inFIG. 8, reduces initial pressure (pressure value P) in the discharge side of the air compressor6to pressure which, is substantially equal to the atmospheric pressure or pressure in a standard state, through the air exhaustion control. An FS relay27is then turned on, and a compressor driver26is turned off while the exhaust valve12and the supply/exhaust valve15are both closed. This causes a significant change in the pressure value P in the discharge side of the air compressor6in the event of a ground fault, as compared to when the pressure value P is high. This facilitates the detection of an increase in the pressure value P in the discharge side of the air compressor6.

In this way, the second embodiment also provides substantially the same operation and advantageous effects as those of the first embodiment. If the pressure value P is too high, a change in pressure is minor even if the air compressor6is driven, which deteriorates accuracy in distinction between the ground fault and the disconnection. The second embodiment reduces the pressure value P in the discharge side of the air compressor6before starting the ground fault/disconnection distinguishing control. This reduction of the pressure value P makes significant a change in the pressure value P, which takes place with pressure increase, in the case where the air compressor6is driven due to the occurrence of a ground fault failure. This can improve a ground fault detection accuracy.

FIGS. 9 to 11show a third embodiment of the invention. The third embodiment is characterized in that a compressor driver and a battery-side voltage monitor are connected to an upstream side of a compressor relay. In the third embodiment, the same constituent elements as those of the first embodiment are provided with the same reference marks, and description thereof will be omitted.

A compressor driver41configures a relay driving device which outputs a drive signal to a compressor relay22. The compressor driver41is connected to an upstream side of the compressor relay22. To be more specific, the compressor driver41is connected to a battery-side terminal25A in one end, and is connected to a battery21in the other end. The compressor driver41is configured in the same manner as a compressor driver26of the first embodiment. The compressor driver41includes an overcurrent protection circuit41A and a switching circuit41B. When overcurrent flows to a coil22A, the overcurrent protection circuit41A detects the overcurrent. The switching circuit41B connects or disconnects the battery-side terminal25A to or from the battery21in accordance with a control signal from the microcomputer30and a detection signal from the overcurrent protection circuit41A.

A fail-safe relay42(hereinafter, referred to as an FS relay42) configures another relay driving device which outputs a drive signal to the compressor relay22. The FS relay42is connected to either the upstream side or a downstream side of the compressor relay22, whichever is opposite to the compressor driver41. In this case, the FS relay42is connected to the downstream side of the compressor relay22. The FS relay42is connected to a ground-side terminal25B in one end, and is connected to the ground in the other end. The FS relay42has a control terminal connected to an I/O port32of the microcomputer30. In response to the control signal from the microcomputer30, the FS relay42is switched between an ON state which connects the ground-side terminal25B to the ground and an OFF state which disconnects the ground-side terminal25B from the ground.

The battery-side voltage monitor43is connected to the upstream side of the compressor relay22. The battery-side voltage monitor43detects a voltage value Vb of the battery-side terminal25A as voltage on an upstream side of the cod22A. An input side of the battery-side voltage monitor43is connected in between the FS relay42and the battery-side terminal25A. An output side of the battery-side voltage monitor43is connected to the microcomputer30via an A/D converter31. The battery-side voltage monitor43outputs to the microcomputer30a detection signal corresponding to the voltage value Vb of the battery-side terminal25A.

A ground-side voltage monitor44is connected to the downstream side of the compressor relay22. The ground-side voltage monitor44detects a voltage value Vg of the ground-side terminal25B as a voltage value on a downstream side of the coil22A. An input side of the ground-side voltage monitor44is connected in between the compressor driver26and the ground-side terminal25B. An output side of the ground-side voltage monitor44is connected to the microcomputer30via the A/D converter31. The ground-side voltage monitor44outputs to the microcomputer30a detection, signal corresponding to the voltage value Vg of the ground-side terminal25B. The voltage monitors43and44configure voltage detection devices which detect the drive voltage of the compressor relay22.

Air suspension control processing including vehicle height adjustment, processing by the microcomputer30will be explained below with reference toFIG. 10.

FIG. 10shows a part of the air suspension control processing according to the third embodiment. As in the first embodiment, the microcomputer30repeatedly executes the air suspension control processing shown inFIGS. 10 and 5at preset time intervals.

The air suspension control processing of the third embodiment is substantially the same as the air suspension control processing of the first embodiment. However, the connecting location of the FS relay42and the compressor driver41in the third embodiment is opposite to that of the FS relay27and the compressor driver26in the first embodiment. The FS relay42is connected to the downstream side of the coil22A, whereas the compressor driver41is connected to the upstream side of the coil22A. Accordingly, the third embodiment executes Steps31and32, instead of the Steps2and6executed by the first embodiment. In this respect, the third embodiment differs from the first.

In the Step31, the FS relay42is brought into an OFF state (disconnected state), and the compressor driver41into an ON state (connected state). In this state, the microcomputer30reads the voltage value Vg detected by the ground-side voltage monitor44. The Step3and subsequent processing are then executed.

If the determination of the Step3is “YES,” the routine moves to the Step5. The Step5starts the ground fault/disconnection distinguishing control. In a subsequent Step32, the microcomputer30turns off the FS relay42and turns on the compressor driver41. The Step7and subsequent processing are then executed.

A detection behavior of the microcomputer30for detecting ground faults and disconnections will be now explained with reference toFIGS. 9 and 11.

When making the failure determination, the microcomputer30turns off the FS relay42and turns on the compressor driver41. As shown inFIG. 11, in an ordinary state where the drive signal of the compressor relay22is normal, the voltage value Vg detected by the ground-side voltage monitor44is High. On the other hand, for example, if a ground fault or a disconnection occurs in the middle (“A” point onFIG. 9) between the coil22A and the ground-side terminal25B, the voltage value Vg detected by the ground-side voltage monitor44comes close to 0[V], which means that the voltage value Vg becomes Low. When the voltage value Vg detected by the ground-side voltage monitor44becomes Low, this allows the detection of a ground-fault or disconnection occurrence.

When a ground fault occurs, a ground fault current If1flows to the coil22A to turn on the compressor relay22. In the ground fault state, therefore, an air compressor6is driven, which increases the pressure value P in a discharge side portion of the air compressor6. In the event of a disconnection, the compressor relay22is maintained in the OFF state, in the disconnection state, therefore, the air compressor6is suspended, so that the pressure value P is not increased. The microcomputer30thus can detect a ground fault and a disconnection distinctively from each other on the basis of whether or not the pressure value P is increased.

In this way, the third embodiment can provide substantially the same operation and advantageous effects as the first embodiment. The third embodiment is applicable to the second embodiment.

FIGS. 9 and 12 to 14show a fourth embodiment of the invention, the fourth embodiment is characterized in that a supply fault and a disconnection are detected distinctively from each other, in the fourth embodiment, the same constituent elements as those of the first and third embodiments will be provided with the same reference marks, and description thereof will be omitted.

FIGS. 12 and 13show air suspension control processing according to the fourth embodiment. As in the third embodiment, a microcomputer30repeatedly executes the air suspension control processing shown inFIGS. 12 and 13at preset time intervals.

The air suspension control processing of the fourth embodiment is substantially the same as the air suspension control processing of the third embodiment. According to the fourth embodiment, however, if the determination of the Step1is “NO,” processing of Steps41and42or another processing is executed to determine whether there is a supply fault before the voltage value Vg is read from the ground-side voltage monitor44in the Step31. In this respect, the fourth embodiment differs from the third.

In the Step41, the FS relay42is brought into an ON state (connected state), and the compressor driver41into an OFF state (disconnected state). In this state, the microcomputer30reads the voltage value Vb detected by the battery-side voltage monitor43.

A subsequent Step42makes a determination as to whether the voltage value Vb is High, that is, whether the voltage value Vb of the battery-side terminal25A is in the vicinity of a supply voltage from a battery21.

At this point of time, the FS relay42is in the ON state, and the compressor driver41is in the OFF state. The battery-side terminal25A and the battery21are therefore disconnected from each other. In the ordinary state, the ground fault state, and the disconnection slate, the voltage value Vb of the battery-side terminal25A is in the vicinity of the ground (0[V], for example), in the supply fault state where an upstream side of a coil22A is short-circuited to the battery21, the voltage value Vb of the battery-side terminal25A is in the vicinity of the supply voltage from the battery21.

If the determination of the Step42is “NO,” the voltage value Vb is Low and is in the vicinity of the ground. The circuit is then determined not to be in the supply fault state. The Step31and subsequent processing are then executed to determine whether the circuit is in the ordinary state, the disconnection state or the ground fault state.

If the determination of the Step42is “YES,” the voltage value Vb is in the vicinity of the supply voltage from the battery21, which means that the voltage value Vb is High. It is therefore determined that the upstream side of the coil22A is connected to the battery21, and that there is a supply fault. The routine moves to a Step43. The step43executes supply fault confirmation processing and stores a failure code corresponding to a supply fault in the memory section30A. Thereafter, fail-safe processing of the Step13and the subsequent steps are executed as in the case of ground faults.

A detection behavior of the microcomputer30for detecting supply faults will be now explained with reference toFIGS. 9 and 14.

Let us assume for example, that a supply limit or a disconnection has occurred in the middle (“B” point onFIG. 9) between the coil22A and the battery-side terminal25A, which is located on the upstream side of the coil22A of the compressor relay22. If what has occurred is a disconnection, the voltage value Vb detected by the battery-side voltage monitor43comes close to 0[V] from the battery21by turning off the compressor driver41, which means that the voltage value Vb becomes Low, as in the normal state or the ground fault state. If it is a supply fault which has occurred, however, the voltage value Vb detected by the battery-side voltage monitor43comes close to the supply voltage from the battery21, which means that the voltage value Vb becomes High.

When making a supply fault determination, the microcomputer30turns on the FS relay42and turns off the compressor driver41. As shown inFIG. 14, the voltage value Vb is Low in an ordinary state where the drive signal of the compressor relay22is normal. The voltage value Vb is Low also in the case of either ground limits or disconnections.

In the event of a supply fault, however, the voltage value Vb becomes High. At this point of time, a supply fault current If2[A] flows to the coil22A of the compressor relay22, which turns on the compressor relay22. When the voltage value Vb detected by the battery-side voltage monitor43becomes High, it is determined that there is a supply fault. In this way, the microcomputer30can detect a supply fault and a disconnection distinctively from each other on the basis of the voltage value Vb detected by the battery-side voltage monitor43.

As described above, the fourth embodiment provides substantially the same operation and advantageous effects as the first embodiment. The fourth embodiment further makes it possible to detect a supply fault and a disconnection distinctively from each other. When a supply fault failure is detected, the FS relay42placed on the downstream side of the compressor relay22is brought into the OFF state (disconnected state), which makes it possible to avoid wasting the power of the battery21.

The fourth embodiment has been discussed with the example where the fourth embodiment is applied to the third. However, the fourth embodiment may be applied to the first and second embodiments. The fourth embodiment is designed to detect the three kinds of states including a supply fault, a ground fault, and a disconnection, distinctively from one another. However, the invention is not limited to such a configuration, and may be configured to, for example, detect a supply fault and a disconnection distinctively from each other without detecting ground faults. Such a configuration may be applied to the first and second embodiments.

The embodiments have explained specific examples of failure determination devices by referring to the Steps5to8,12and41to43shown inFIGS. 4, 5, 7, 10, 12 and 13.

According to the embodiments, the air suspensions3are provided to all the wheels2A to2D, that is, the left front, right front, left rear, and right rear wheels. However, the invention is not limited to such a configuration, and the air suspensions may be provided to only the front or rear wheels.

The embodiments have been discussed, taking as an example the pneumatic suspension system including the air compressor module5as a fluid power pump, and the air suspensions3as fluid power suspension bodies. The invention is not limited to such a configuration. The invention may be applied to, for example, a hydraulic suspension system including a hydraulic pump as a fluid power pump, and a hydraulic damper and a hydraulic cylinder as fluid power suspension bodies. In such a case, instead of the compressor relay, a pump relay is utilized, which connects the electric motor for driving the hydraulic pump to the battery.

According to the embodiments, the vehicle height sensor16is used as the vehicle behavior detection device. However, the vehicle behavior detection device may be any device as long as it detects the behavior of the vehicle. Conceivable vehicle behavior detection devices include an acceleration sensor for detecting accelerations in up-down, forward-rearward, and right-left directions, an angular velocity sensor for detecting a roll and a pitch, and other devices.

The embodiments have been discussed with reference to the case in which the air suspension system of the invention is applied to a vehicle, such as a four-wheeled vehicle, the invention is not limited to such a configuration and may be applied to other vehicles including rail vehicles.

Inventions included in the above-discussed embodiments will be described below. According to the invention, the control device includes the failure determination device configured to detect at least either one of a supply fault and a ground fault of the drive signal of the relay distinctively from a disconnection on the basis of the voltage value detected by the voltage detection device and the pressure value detected by the pressure detection device. If a failure occurs in the drive signal of the relay, it is possible to distinguish between a ground fault failure and a disconnection failure. This reduces a cost burden at repair plants.

The invention is also capable of distinguishing between a ground fault failure and a disconnection failure on the basis of the voltage value detected by the voltage detection device and the pressure value detected by the pressure detection device without using current functioning as the drive signal of the relay. This eliminates the necessity of installation of a current monitor circuit in the control device, which reduces production costs.

According to the invention, the relay driving device and the voltage detection device are connected to the downstream side of the relay. The failure determination device detects a disconnection and a ground fault of the drive signal of the relay distinctively from each other. Therefore, if the relay driving device is turned off while the upstream side of the relay is connected to the battery, it is possible to detect a disconnection or ground-fault occurrence in the drive signal of the relay on the basis of the voltage value detected by the voltage detection device. In addition, if the relay driving device is turned off while the upstream side of the relay is connected to the battery, the relay is turned on or off, depending on whether what has occurred is a disconnection or a ground fault. The failure detection device is capable of detecting a disconnection, and a ground fault of the drive signal of the relay distinctively from each other according to whether or not the pressure value detected by the pressure detection device is increased.

According to the invention, the relax driving device and the voltage detection device are connected to the upstream side of the relay. The failure determination device detects a disconnection and a supply fault of the drive signal of the relay distinctively from each other. It is then possible to avoid wasting the power of the battery by disconnecting the downstream side of the relay when a supply fault is detected.

According to the invention, the control device implements the control for lowering the vehicle height of the vehicle when a disconnection is detected by the failure determination device. The disconnection occurrence in the drive signal of the relay makes it impossible to drive the fluid power pump. However, the air exhaustion control can be carried out to discharge oil and air from the fluid power suspension bodies. This allows the vehicle height control to be implemented for lowering the vehicle height in accordance with vehicle conditions.

In a first aspect of the suspension system, the suspension system includes a battery installed in a vehicle; a fluid power pump operated by being powered by the battery; a relay connecting the battery and the fluid power pump; fluid power suspension bodies mounted on a plurality of wheels of the vehicle; supply/exhaust valves placed between the fluid power pump and the respective fluid power suspension bodies; an exhaust valve configured to discharge a working fluid in a discharge side of the fluid power pump; a pressure detection device configured to detect pressure of the working fluid in the discharge side of the fluid power pump; a relax driving device configured to output a drive signal to the relay; a voltage detection device configured to detect the drive voltage of the relay; a vehicle behavior detection device configured to detect behavior of the vehicle; and a control device. The control device includes a failure determination device configured to detect at least either one of a supply fault and a ground fault of the drive signal of the relay distinctively from a disconnection on the basis of a voltage value detected by the voltage detection device and a pressure value detected by the pressure detection device.

In a second aspect of the suspension system according to the first aspect, the relay driving device and the voltage detection device may be connected to a downstream side of the relay, and the failure determination device may be configured to detect a disconnection and a ground fault of the drive signal of the relay distinctively from each other.

In a third aspect of the suspension system according to the first aspect, the relay driving device and the voltage detection device may be connected to an upstream side of the relay, and the failure determination device may be configured to detect a disconnection and a supply fault of the drive signal of the relay distinctively from each other.

In a fourth aspect of the suspension system according to any one of the first to third aspects, the control device may be configured to implement control for lowering vehicle height of the vehicle when the failure determination device detects a disconnection.

In a fifth aspect of the suspension system according to the first aspect the failure determination device may be configured to reduce the pressure value of the discharge side of the fluid power pump before starting control for distinguishing between a ground fault and a disconnection of the drive signal of the relay.

The foregoing description refers to only some embodiments of the invention. One skilled in the art should easily understand that the exemplary embodiments may be modified or improved in various ways without materially departing from the novel teachings and advantages of the invention. Accordingly, all such modifications and improvement are ended to be included within the technical scope of the invention. The embodiments may be combined in any ways.

The present application claims priority under Japanese Patent Application No. 2015-131334 filed on Jun. 30, 2015. The entire disclosure of Japanese Patent Application No. 2015-131334 filed on Jun. 30, 2015, including the description, claims, drawings and abstract, is incorporated herein by reference in its entirety.

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