Vehicle control apparatus

A vehicle includes a battery and an alternator as a power source, and a plurality of vehicle load groups that operate commonly receiving power supply from the power source. When a plurality of requests for actuating the plurality of loads are made simultaneously, a control circuit determines a request of higher priority and a request of lower priority based on a predetermined priority for each of said requests. The control circuit operates the corresponding load as requested in response to the request of high priority, and operates the corresponding load with the operation limited to consume smaller power than requested in response to the request of low priority. More preferably, one of the plurality of loads is variable valve timing apparatus changing a timing of opening/closing an intake valve or an exhaust valve of an internal combustion engine.

This nonprovisional application is based on Japanese Patent Application No. 2005-290980 filed with the Japan Patent Office on Oct. 4, 2005, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a vehicle control apparatus and, more specifically, to a vehicle control apparatus including a plurality of loads that operate commonly receiving power supply from a power source.

2. Description of the Background Art

Recently, various electronically controlled equipment and facilities have come to be mounted on a vehicle. When a plurality of devices having different power consumption capacities are to be actuated simultaneously, however, a voltage drop occurs, resulting in lower speed of overall actuation. As a solution, it has been necessary to install a large generator or to increase battery capacity.

Japanese Patent Laying-Open No. 2003-189696 discloses a technique in which priorities are set among a plurality of devices, and when drive of a device having high priority becomes necessary, supply of driving power to a device of lower priority is stopped, whereby the generator size is reduced.

When the supply of driving power to the device is stopped, however, the device is set to an inoperative state. Long duration of the inoperative state possibly leads to a problem. Further, the device of which operation is once stopped takes longer time to attain the target operation.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a vehicle control apparatus allowing appropriate operation of a plurality of loads while maintaining operations of the plurality of loads as much as possible.

In summary, the present invention provides a vehicle control apparatus, wherein the vehicle includes a power source apparatus and a plurality of loads that operate commonly receiving power supply from the power source apparatus; when a plurality of requests for actuating the plurality of loads are made simultaneously, the control apparatus determines a request of higher priority and a request of lower priority based on a predetermined priority for each of the requests, and the control apparatus operates the corresponding load as requested in response to the request of high priority, and operates the corresponding load with the operation limited to consume smaller power than requested in response to the request of low priority.

Preferably, the control apparatus limits an operation corresponding to the request of low priority when an output voltage of the power source apparatus is smaller than a prescribed threshold value, and does not limit an operation corresponding to the request of low priority when the output voltage of the power source apparatus is not lower than the prescribed threshold value.

Preferably, the vehicle further includes an internal combustion engine; and requests for the plurality of loads are classified in advance into a plurality of groups; and the priority differs group by group among the plurality of groups, and the priority is the same in each group.

More preferably, one of the plurality of loads is a variable valve timing apparatus changing a timing of opening/closing an intake valve or an exhaust valve of the internal combustion engine; one of the plurality of groups is a group to which a first request for actuating the variable valve timing apparatus belongs; and another one of the plurality of groups has the priority higher than the first request.

More preferably, one of the plurality of loads is a variable valve timing apparatus changing a timing of opening/closing an intake valve or an exhaust valve of the internal combustion engine; one of the plurality of groups is a group to which a first request for actuating the variable valve timing apparatus belongs; and another one of the plurality of groups has the priority lower than the first request.

More preferably, one of the plurality of loads is a variable valve timing apparatus changing a timing of opening/closing an intake valve or an exhaust valve of the internal combustion engine; one of the plurality of groups is a group to which a first request for actuating the variable valve timing apparatus at the time of starting belongs; and another one of the plurality of groups is a group to which a second request for actuating the variable valve timing apparatus after starting, having the priority lower than the first request, belongs.

According to another aspect, the present invention provides a vehicle control apparatus, wherein the vehicle includes a power source apparatus and a plurality of loads that operate commonly receiving power supply from the power source apparatus; when a plurality of requests for actuating the plurality of loads are made simultaneously, the control apparatus determines a load of higher priority and a load of lower priority based on a predetermined priority for each of the plurality of loads, and the control apparatus causes the power source apparatus to supply unlimited power to the load of high priority, and causes the power source apparatus to supply limited power to the load of lower priority.

Preferably, the control apparatus causes the power source apparatus to limit power supply to the load of lower priority when an output voltage of the power source apparatus is smaller than a prescribed threshold value, and does not cause the power source apparatus to limit power supply to the load of lower priority when an output voltage of the power source apparatus is larger than the prescribed threshold value.

Preferably, the vehicle further includes an internal combustion engine; the plurality of loads are classified in advance into a plurality of groups; and the priority differs group by group among the plurality of groups, and the priority is the same in each group.

More preferably, one of the plurality of loads is a variable valve timing apparatus changing a timing of opening/closing an intake valve or an exhaust valve of the internal combustion engine; one of the plurality of groups is a group to which the variable valve timing apparatus belongs; and another one of the plurality of groups has the priority higher than the variable valve timing apparatus.

More preferably, one of the plurality of loads is a variable valve timing apparatus changing a timing of opening/closing an intake valve or an exhaust valve of the internal combustion engine; one of the plurality of groups is a group to which the variable valve timing apparatus belongs; and another one of the plurality of groups has the priority lower than the variable valve timing apparatus.

According to a still further aspect, the present invention provides a method of controlling a vehicle including a power source apparatus and a plurality of loads that operate commonly receiving power supply from the power source apparatus, including: the step of detecting, when a plurality of requests for actuating the plurality of loads are made simultaneously, based on a predetermined priority for each of the requests, presence/absence of a first request of high priority; and the step of operating, in response to the first request, a corresponding load as requested, and operating, in response to a second request of lower priority than the first request, a corresponding load with the operation limited to consume smaller power than requested.

By the present invention, necessary power is supplied to a device of high priority, and therefore, control is possible without hindering the actuation thereof Further, power supply to a device of lower priority is not fully stopped but reduced and the operation is maintained, and therefore, even a device or devices of lower priority can attain to the target more quickly.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, the present invention will be described in detail with reference to the figures. Throughout the figures, the same or corresponding portions are denoted by the same reference characters and description thereof will not be repeated.

FIG. 1shows a configuration of a vehicle100in accordance with an embodiment of the present invention.

Referring toFIG. 1, vehicle100includes an internal combustion engine2, a buttery4, an alternator6, a control circuit8, a voltage sensor10and an accelerator sensor11.

Internal combustion engine2includes a cylinder30provided in a cylinder block, a piston32reciprocated in cylinder30, and a connecting rod34connecting piston32and a crank shaft36.

Internal combustion engine2further includes crank shaft36, an intake cam shaft20, a cam26fixed to intake cam shaft20, an intake valve28, which is an air valve opened/closed as it is pressed down by cam26along with the rotation of intake cam shaft20, and a valve timing varying unit varying the timing of rotation of intake valve28by changing a rotational phase of intake cam shaft with respect to crank shaft36.

Intake cam shaft20rotates as crank shaft36rotates. Cam26is fixed on intake cam shaft20, and determines opening position of intake valve28based on the distance of outer circumference from the rotation axis of intake cam shaft20.

Internal combustion engine2is provided with a variable valve timing (VVT) mechanism. Valve timing varying unit changes the timing of opening and closing intake valve28by changing the rotational phase of intake cam shaft with respect to crank shaft36based on a timing control signal SC.

The valve timing varying unit includes a VVT (Variable Valve Timing) motor14and an advancing mechanism16. The force of a sprocket wheel38mounted on the crank shaft is transmitted to a sprocket wheel18through a chain40, and rotates advancing mechanism16. VVT motor14rotates, receiving power from battery4. Advancing mechanism16rotates intake cam shaft20in accordance with the torque applied from a rotation axis15of VVT motor14and the torque applied from sprocket wheel18.

Internal combustion engine2further includes a cam angle sensor22detecting a rotation angle of intake cam shaft20by detecting rotation of a projection provided on intake cam shaft20, and a crank angle sensor24detecting a rotation angle of crank shaft36. Though not shown, internal combustion engine2is a double overhead cam shaft (DOHC) engine, and includes an exhaust cam shaft and an exhaust valve, not shown.

Control circuit8receives phase information θCA from cam angle sensor22and receives engine speed Ne and phase information θCR from crank angle sensor24, and controls rotation speed such that rotation axis15of VTT motor14rotates basically in the same phase as sprocket wheel18, by control signal SC.

Referring to a requested VVT advancing angle determined based on the output of accelerator sensor11and engine speed, control circuit8slightly increases or decreases the rotation speed of VVT motor14until the advancing angle is reflected on the phase difference in the output of cam angle sensor22and the output of crank angle sensor24.

When actuated abruptly, VVT motor14consumes large power. Therefore, in vehicle100, other vehicle loads are prioritized and classified, and the loads are controlled group by group classified based on the priority.

Vehicle100further includes a vehicle load group50having higher priority than VVT motor14, a load group60of large power consumption and lower priority than VVT motor14, and a load group70of small power consumption and lower priority than VVT motor14.

By way of example, load group50includes a head light52, a tail lamp54, an air bag sensor56, and an electric power steering58. These are highly important loads related to running of the vehicle.

Load group60includes a seat heater61, a defogger62implemented by a hot wire embedded in a rear window, an air-conditioner blower fan63, a fan64for feeding air to an air conditioner condenser, and a fan65feeding air to a radiator. These are loads mainly related to passenger comfort consuming relatively large power.

Load group70includes a car navigation system71and a room lamp72. These are loads mainly related to passenger comfort consuming relatively small power.

Specifically, vehicle100includes battery4and alternator6as power source apparatuses, and a plurality of load groups50,60and70that operate commonly receiving power supply from the power source. When there are a plurality of simultaneous requests for actuating the plurality of loads, control circuit8determines actuation requests of higher priority and actuation requests of lower priority based on predetermined priorities for respective requests, so that in response to a request of high priority, the corresponding load is operated as requested, and in response to a request of low priority, the corresponding load is operated with the operation limited to consume smaller power than requested. Priorities corresponding to respective requests are classified and stored in advance in a memory9provided in control circuit8.

FIG. 2is a flowchart representing a control structure of a program executed by control circuit8shown inFIG. 1upon reception of a VVT motor actuation request.

The flowchart is called from the main routine and executed when a request is made to actuate VVT, by an operation of accelerator sensor11or by load variation.

Referring toFIGS. 1 and 2, when the process starts, control circuit8determines whether the request for actuating VVT is for rapid actuation or not, at step S1. By way of example, the output of accelerator sensor11is monitored and when the amount of stepping of an accelerator pedal increases abruptly, or when the load or the rotation speed change abruptly because of road gradient variation or the like, then the target advancing angle of VTT changes abruptly.

If the difference between the target value and the present advance angle is large, proportional control corresponding to the difference is performed and, therefore, the request for VVT actuation is determined to be a request for rapid actuation.

When the condition of step S1is satisfied, the flow proceeds to step S2, and otherwise, the flow proceeds to step S8.

At step S2, whether there is a request for rapid actuation of a device of high priority or not is determined. Here, the device of high priority means the load belonging to load group50ofFIG. 1, including, for example, head light52, tail lamp54, air bag sensor56and electric power steering58.

At step S2, when there is a request for rapid actuation of the device of high priority, for instance, when head light52is turned on or power steering58is actuated by an abrupt operation of steering wheel, it is determined that there is a request for rapid actuation of the device of high priority. In that case, flow proceeds to step S7, and actuation control of the device of high priority is executed. VVT motor14is controlled such that gain for executing proportional control for a requested value determined by acceleration sensor11and vehicle load is reduced.

When it is determined at step S2that there is no request for rapid actuation of a device of high priority, flow proceeds to step S3.

At step S3, whether there is a request for actuating a device of large capacity with low priority or not is determined. Here, the device of large capacity with low priority means a device that causes, because of large power consumption, voltage drop when operated, though it need not be actuated with higher priority than VVT. By way of example, a load with power consumption of 80 W or more corresponds to the device of large capacity with low priority.

When it is determined at step S3that there is a request for actuating a device of large capacity with low priority, the flow proceeds to step S6. If it is determined that there is no request for actuating a device of large capacity with low priority, the flow proceeds to step S4.

At step S4, whether there is a request for actuating a device of small capacity with low priority or not is determined. Here, the device of small capacity with low priority corresponds to a load belonging to load group70ofFIG. 1, such as car navigation system71or room lamp72. The request corresponds to pressing of a search button of car navigation system71or lighting of room lamp72.

When it is determined at step S4that there is a request for actuating a device of small capacity with low priority, the flow proceeds to step S5. If it is determined that there is no such request, the flow proceeds to step S8.

At step S5, the voltage of power line BL is monitored by voltage sensor10and taken into control circuit8, and whether this value is not higher than a set value (for example, 10V) or not is determined. When the power supply voltage is not higher than the set value at step S5, the flow proceeds to step S6, and when the power supply voltage is higher than the set value at step S5, the flow proceeds to step S8.

The flow proceeds to step S8when the request for actuating VVT is not a request for rapid actuation, that is, when the power consumption is not very large; when the request for actuating VVT is a request for rapid actuation and there is no request for actuating other load circuits; or when the request is for a device of low capacity with low priority and the voltage of power line BL determined by battery4and alternator6is sufficiently high. In such a case, control with priority is not executed, and normal control is done in which no particular restriction is imposed on any request.

The flow proceeds to step S6when the request for actuating VVT is a request for rapid actuation and there is a request for actuating a device of large capacity with low priority, or when there is a request for actuating a device of small capacity with low priority and the power supply voltage of power line BL is not higher than the set value.

In such a case, actuation control with priority of VVT is executed, and the gain for actuation control of other devices with low priority is decreased. For instance, the value of a current caused to flow through seat heater61may be decreased to half the requested value, or air conditioner fan64, radiator fan65and air conditioner blower fan63may be operated with the rotation speed lowered. It is noted that a large current is caused to flow through VVT motor14by the rapid actuation of VVT for about 1 second, and therefore, it is not likely that the passenger feels uncomfortable because of, for example, weaker air-conditioning.

As for the car navigation system71that corresponds to the device of small capacity with low priority, even when there is a request for searching a route to a destination is input through an operation panel, the route search is not performed for a prescribed time period (about 1 second at the longest) until the rapid actuation of VVT is completed and the system is maintained in a state of low power consumption, and the route search is started after the prescribed time period, in accordance with an instruction from control circuit8.

When the process of step S6, S7or S8is complete, the flow proceeds to step S9, and the control returns to the main routine.

FIG. 3is a diagram of operational waveforms representing an example of current variation when control is performed in accordance with the flowchart ofFIG. 2.

Referring toFIG. 3, first, at time t1, an accelerator pedal is pressed and accelerator position θth starts to increase. In response, the target advancing angle θevvtt of VVT calculated inside the control circuit8increases rapidly. To follow the target advancing angle, control circuit8causes, by control signal SC, rapid increase of driving duty d of VVT motor14. As a result, the motor driving duty d exceeds the threshold voltage dth. It is noted that when motor driving duty d increases, the current consumed by VVT motor14also increases.

In response to the motor driving duty d exceeding the threshold value dth, control circuit8changes a current ih of seat heater61and a current if of air conditioner fan64. Heater current ih is decreased from i1to i2, and fan current if is decreased from i3to i4, and from time point t1to t2, operation of these loads is maintained.

In other words, in the time period from t1to t2, control gives higher priority to the operation of VVT motor than the heater or the fan.

When the VVT motor driving duty d becomes lower than the threshold value dth at time point t2, heater current ih is returned from the limited value i2to the requested current value i1, and fan current if is also returned from the limited value i4to the requested current value i3.

In this manner, according to the present embodiment, when a VVT motor that feeds large power when actuated rapidly is used in a power system such as a vehicle, other vehicle loads, that is, devices that consume power similar to the VVT motor, are classified in advance into loads to be operated with high priority, loads of large capacity with low priority and loads of small capacity with low priority, and when the VVT is actuated rapidly, actuation control with priority is executed, making determination with the state of power supply voltage taken into consideration.

Consequently, it becomes unnecessary to provide excessive margin on the power system, so that size reduction of power system becomes easier, and appropriate control of VVT apparatus is realized.

VVT is provided for improving mileage (fuel consumption) by changing timings of opening and closing intake valve and the like in accordance with vehicle load or accelerator position. If the timing of closing the intake valve is delayed too much at the start of operation, engine start may possibly fail because of insufficient compression of the intake air in the combustion chamber.

Therefore, at the time of starting, it is necessary to operate VVT motor14with priority to realize appropriate closing timing before engine ignition. Otherwise, the engine would not start. In other words, at the time of starting, VVT control must be done with higher priority than at other times.

FIG. 4is a flowchart representing a control structure of control executed in the first modification.

Referring toFIG. 4, first, at step S11, control circuit8determines whether the request for actuating VVT is made at the time of starting or not. It may be determined by monitoring an output of crank angle sensor24and checking whether the engine has already been rotating or not. Alternatively, it may be determined dependent on whether the request for actuating VVT is made simultaneously with a request for starting the engine.

At step S11, if the request for actuating VVT is made at the time of starting, the flow proceeds to step S12, and otherwise, the flow proceeds to step S14.

At step S12, control circuit8determines whether there is any other request for actuating other load or loads that can be limited.

By way of example, whether there is a request for actuating the room lamp or air conditioner fan or not is determined, and whether such devices are in operation or not upon request is determined. When it is determined at step S12that there is a request for actuating other load or loads, the flow proceeds to step S13, and control circuit8actuates other load or loads with limitation. After the end of processing of step S13, the flow proceeds to step S14.

When it is determined at step S12that there is not a request for actuating any other load, the flow proceeds to step S14.

At step S14, VVT actuation control is executed. Then, the flow proceeds to step S15and the control is returned to the main routine. Because of such processing, not all the requests for actuating VVT are set to have high priority than other loads of low priority but the requests are set to have priorities determined dependent on the contents of control. Consequently, more appropriate control becomes possible.

FIG. 5shows a configuration of a vehicle200in accordance with a second modification.

Referring toFIG. 5, a vehicle200includes a power source apparatus102; a head light111, a VVT motor112, an air conditioner fan114and a seat heater116as vehicle loads; an engine ECU118; and an air conditioner ECU120.

Power source apparatus102includes a battery104, an alternator105, and current limiting units106and108. By the state of charge of battery104, state of generation of alternator105and the state of current consumed by each load, the voltage on power line BL is determined.

Here, for air conditioner fan114and seat heater116that are devices of lower priority than VVT motor112, current limiting units106and108are provided between power line BL and the respective devices.

Engine ECU118controls VVT motor112and controls valve advancing angle, and controls current limitation by current limiting units106and108.

By such a structure, when a request for actuating air conditioner fan114and seat heater116is made independently by air conditioner ECU120, actuation with priority of VVT can be realized by adding or changing current limiting units106and/or108and by the contents of control of engine ECU118, while maintaining the state of ECU120as it is. In other words, actuation with priority of VVT can be realized without making any particular change to ECU120.

As described above, in the present embodiment, necessary power is supplied to the device of higher priority, and therefore, control without hindering the operation of the device becomes possible.

Further, it is not the case that the power is not supplied at all to the devices of lower priority, but devices of lower priority still operate with reduced power. Therefore, targets can be reached more quickly even in these devices.

When the priority is determined as the contents of control and not set device by device, more delicate control can be realized in an appropriate manner.

Further, when actuation is limited in view of the state of power supply voltage, unnecessary limit on the actuation can be avoided when the voltage state is satisfactory.