Patent Description:
Acquisition of the speed limit of a place where a vehicle is traveling, and limiting of the vehicle speed to be less than or equal to the acquired speed limit has been discussed in the related art (for example, see <CIT>). <CIT> and <CIT> disclose other examples of methods and devices for limiting the speed of a motor vehicle.

According to the present invention, a vehicle speed limiting apparatus as defined in claim <NUM> comprises a vehicle speed control apparatus including at least one processor configured to determine an upper-limit speed of a vehicle each time a speed limit of a road on which the vehicle is traveling changes; and to control a speed of the vehicle in such a manner as to not exceed the upper-limit speed even if the vehicle's accelerator pedal depression amount would increase the speed of the vehicle over the upper-limit speed. The at least one processor is configured to control, until a predetermined timing, that the speed of the vehicle does not exceed the upper-limit speed, the upper-limit speed being determined before the start of the vehicle's lane change is estimated, if (i) the start of the vehicle's lane change is estimated, and (ii) a reduction in the speed limit is determined, and to control, after the predetermined timing, that the speed of the vehicle does not exceed the currently determined upper-limit speed.

Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.

For the purpose of convenience, the description of the above-mentioned related art will be continued first.

In the related art, if the speed limit of the road where the vehicle is travelling changes, the vehicle speed is automatically limited to the new speed limit without regard to whether the vehicle is carrying out a lane change. If the speed limit of the road is reduced just at a time of carrying out a lane change, the vehicle may automatically decelerate even though the driver does not wish to decelerate the vehicle because of carrying out a lane change.

Therefore, an object of the present invention is to provide a vehicle speed limiting apparatus, whereby it is possible to reduce a likelihood of deceleration of a vehicle which may otherwise occur against the driver's intention.

<FIG> is a block diagram illustrating an example of a configuration of a vehicle speed limiting apparatus <NUM> including a vehicle speed control apparatus <NUM>. The vehicle speed limiting apparatus <NUM> is an example of an apparatus that limits a vehicle speed within an upper-limit speed determined depending on the speed limit of a road. The vehicle speed limiting apparatus <NUM> is an on-vehicle apparatus installed in a vehicle. The vehicle speed limiting apparatus <NUM> includes, for example, a vehicle speed detection part <NUM>, a speed limit determination part <NUM>, a lane change estimation part <NUM>, an other-lane vehicle speed measurement part <NUM>, an own-lane vehicle speed measurement part <NUM>, an accelerator pedal <NUM>, a depression amount detection part <NUM>, the vehicle speed control apparatus <NUM>, a power train <NUM>, and a reporting part <NUM>.

The vehicle speed detection part <NUM> is an example of a sensor detecting a vehicle speed V. Specific examples of a vehicle speed detection part <NUM> may include, for exmaple, a wheel speed sensor, which detects the vehicle speed V by monitoring the rotation of the wheel(s).

The speed limit determination part <NUM> is an example of a device that is configured to determine the speed limit Vr of the road on which the vehicle is travelling. The speed limit determination part <NUM> includes, for example, a camera that takes an image in the front of the vehicle, and an image recognition part that carries out an image recognition process to acquire a road sign or the speed limit Vr indicated on the road sign from the image taken by the camera. Alternatively, the speed limit determination part <NUM> can be, for example, a memory that stores the respective speed limits Vr of roads, and an extraction part that extracts the speed limit Vr of the road where the vehicle currently is, from the memory (e.g., a car navigation device having a route searching function, or the like).

The speed limit determination part <NUM> may determine the speed limit for each lane of a road, for example, where the speed limit Vr of the road is set for each lane included in the road. In this case, the speed limit determination part <NUM> include, for example, a memory that stores the speed limits Vr of the respective lanes included in the roads Vr, and an extraction part that extracts the speed limit Vr of the lane of the road in which the vehicle is present from the memory. Therefore, for example, in <FIG>, the speed limit determination part <NUM> is capable of determining the speed limit Vr of the lane of the road <NUM> in which the vehicle <NUM> is currently traveling (i.e., the lane <NUM> before a lane change is started, or the lane <NUM> after the lane change is finished). Also, the speed limit determination part <NUM> is capable of determining the speed limit Vr of the lane <NUM> to which the vehicle <NUM> is to move through the lane change before the lane change is finished.

Returning to <FIG>, the lane change estimation part <NUM> is an example of a device that estimates whether the vehicle will start a lane change, and to estimate whether the vehicle has finished the lane change. The lane change estimation part <NUM> outputs an estimation signal Lc having an active level during an estimation period (hereinafter, referred to as an " estimation period of time Ta") starting from when it estimates that the vehicle will start a lane change until when it estimates that the vehicle has finished the lane change. The lane change estimation part <NUM> outputs the estimation signal Lc having a high level during the estimation period of time Ta, and outputs the estimation signal Lc having a low level during a period of time (hereinafter, referred to as an "other-than estimation period of time Tb") other than the estimation period of time Ta, for example The lane change estimation part <NUM> estimates whether the vehicle is changing into the left or right lane. The lane change estimation part <NUM> has a function of estimating whether the vehicle will start a lane change in front of another vehicle that is in the destination lane.

The lane change estimation part <NUM> estimates a start and an end of the lane change based on, for example, a change in a signal of the vehicle's direction indicator. In this case, when a change in the signal of the direction indicator from its turned off state to its turned on state is detected, the lane change estimation part <NUM> estimates that the vehicle will start a lane change. When the signal of the direction indicator is switched from its turned on state to its turned off state, the lane change estimation part <NUM> estimates that the vehicle has finished the lane change.

Alternatively, the lane change estimation part <NUM> may also estimate the start and the end of a lane change based on changes in the extent to which the width of the vehicle overlaps with the width of the lane in which the vehicle is traveling. In this case, the lane change estimation part <NUM> estimates that the vehicle will start a lane change when it detects that the extent of overlap falls below a predetermined value. The lane change estimation part <NUM> estimates that the vehicle has finished the lane change when it detects that the extent of overlap exceeds a predetermined value.

Alternatively, the lane change estimation part <NUM> may estimate the start and the end of a lane change based on changes in the number of lanes of the road on which the vehicle is traveling.

In this case, for example, in <FIG>, the lane change estimation part <NUM> estimates that the vehicle <NUM> will start a lane change when it detects that the travel time to elapse until the vehicle <NUM> reaches the reduced-number-of-lanes position <NUM> or the distance to the position becomes less than or equal to a predetermined threshold P. In fact, in such a case, the lane change estimation part <NUM> is capable of estimating a lane change of the vehicle <NUM> to the lane <NUM>. The "reduced-number-of-lanes position" <NUM> means a position where the lane <NUM> ends due to the reduction in the number of lanes of the road <NUM> on which the vehicle <NUM> is currently traveling, and may include a position near the position where the lane <NUM> ends. The threshold P is determined to be any value greater than <NUM>.

The lane change estimation part <NUM> estimates that the vehicle <NUM> has finished the lane change to the lane <NUM> when it detects that the travel time having elapsed after the vehicle <NUM> passed through the reduced-number-of-lanes position <NUM> or the travel distance therefrom becomes greater than or equal to a predetermined threshold Q. The threshold P is determined to be any value greater than or equal to <NUM>.

For example, in <FIG>, the lane change estimation part <NUM> estimates that the vehicle <NUM> will start a lane change when it detects the signal from the direction indicator of the vehicle <NUM> suggesting a lane change to the lane <NUM> starting at the increased-number-of-lanes position <NUM>, while the travel time to elapse until the vehicle <NUM> reaches the number-of-lane increase position <NUM> or the travel distance thereto is less than or equal to a predetermined threshold R. In fact, in such a case, the lane change estimation part <NUM> is capable of estimating a lane change of the vehicle <NUM> to the lane <NUM>. The "increased-number-of-lanes position" <NUM> means a position where the lane <NUM> adjacent to the lane <NUM> in which the vehicle <NUM> is currently traveling starts due to the increase in the number of lanes of the road <NUM>, and can include a position near the position where the lane <NUM> starts. The threshold R is determined to be any value greater than <NUM>. The lane <NUM> is, for example, a passing lane having the same speed limit Vr as the lanes <NUM> and <NUM> or greater than the lanes <NUM> and <NUM>, or a branch lane having the speed limit Vr that is the same as the lanes <NUM> and <NUM> or less than the lanes <NUM> and <NUM> (for example, a connection road at an interchange, or the like).

The lane change estimation part <NUM> estimates that the vehicle has finished the lane change when it detects that the travel time after the vehicle <NUM> passed through the increased-number-of-lanes position <NUM> or the travel distance therefrom becomes greater than or equal to a predetermined threshold S, and the signal of the direction indicator of the vehicle <NUM> is switched from its turned on state to its turned off state. The threshold S is determined to be any value greater than or equal to <NUM>.

An actual method of estimating lane changes by the lane change estimation part <NUM> is not limited thereto, and any other method can be used. In order to avoid erroneous estimates of lane changes, any one of the above-mentioned methods can be combined. In order to avoid erroneous estimates of lane changes, estimation of a lane change can be carried out in such a manner as to additionally use at least one item of information of steering information, yaw rate information, image information taken by a camera, the vehicle position information, and so forth, in a combining manner.

Returning to <FIG>, the other-lane vehicle speed measurement part <NUM> is an example of such a sensor that measures the vehicle speed Va of another vehicle that is travelling on a lane different from the lane in which the vehicle equipped with the vehicle speed limiting apparatus <NUM> is traveling. The own-lane vehicle speed measurement part <NUM> is an example of such a sensor that measures the vehicle speed Vb of another vehicle travelling in the same lane as the lane in which the vehicle is traveling. The other-lane vehicle speed measurement part <NUM> and the own-lane vehicle speed measurement part <NUM> are examples of a speed measuring part that measures the vehicle speed of another vehicle. For example, in <FIG>, the other vehicle speed measurement part <NUM> is capable of measuring the vehicle speed Va of the other vehicle <NUM> travelling in the lane <NUM> adjacent to the lane <NUM> when the vehicle <NUM> is traveling in the lane <NUM>. Also, the own vehicle speed measurement part <NUM> is capable of measuring the vehicle speed Vb of the other vehicle <NUM> travelling in the lane <NUM> when the vehicle <NUM> is travelling in the lane <NUM>. Specific examples of these vehicle speed measurement parts <NUM> and <NUM> include sensors that emit electric waves towards another vehicle to measure the vehicle speed of the other vehicle, communication devices that receive the other vehicle's vehicle speed through vehicle-vehicle or road-vehicle radio communication, or the like.

Returning to <FIG>, the depression amount detection part <NUM> is an example of a sensor detecting the depression amount Ac of the accelerator pedal <NUM> depressed by the driver. The depression amount Ac of the accelerator pedal <NUM> is also called an "opening" Ac of the accelerator pedal <NUM> depressed by the driver.

The vehicle speed control apparatus <NUM> is an example of a device that carries out control to limit the vehicle speed (i.e. "vehicle speed limiting control") so that it does not exceed an upper-limit speed determined according to the determined speed limit Vr of the road. The vehicle speed control apparatus <NUM> includes an upper-limit determination part <NUM>, a vehicle speed control part <NUM>, and an excess determination part <NUM>. The vehicle speed control apparatus <NUM> is, for example, an electronic control unit (so-called, "ECU") that includes a microcomputer (as will be described later with reference to <FIG>) implementing the upper-limit determination part <NUM>, the vehicle speed control part <NUM>, and the excess determination part <NUM>.

The upper-limit determination part <NUM> is an example of a device that determines the vehicle's upper-limit speed (hereinafter, referred to as an "upper-limit speed Vu") each time the speed limit Vr of the road determined by the speed limit determination part <NUM> changes. The upper-limit determination part <NUM> determines the upper-limit speed Vu to be such a value as to have a difference from the speed limit Vr less than a predetermined amount. In other words, the upper-limit speed Vu can be determined to be the same as the speed limit Vr, a value acquired from adding a predetermined difference to the speed limit Vr, a value acquired from subtracting a predetermined difference from the speed limit Vr, or the like. For example, if the determined speed limit Vr is <NUM> kph, the upper-limit determination part <NUM> can determine that the upper-limit speed Vu is <NUM> kph, <NUM> kph, <NUM> kph, or the like. Note that "kph" denotes "km/h".

The vehicle speed control part <NUM> is an example of a device that controls the vehicle speed V using the upper-limit speed Vu as the upper-limit (in other words, to not exceed the upper-limit speed Vu) even if the depression amount AC of the vehicle's accelerator pedal <NUM> would increase the vehicle speed V over the upper-limit speed Vu. The depression amount AC is detected by the depression amount detection part <NUM>. The vehicle speed control part <NUM> includes a speed adjustment part <NUM> that outputs a control signal Z for adjusting the vehicle speed V.

The power train <NUM> is an example of a mechanism for transmitting, via a gearbox, the power of at least one of an engine and a motor to the wheels of the vehicle according to the control signal Z that is output from the speed adjustment part <NUM>. The power train <NUM> includes, for example, at least one of the engine, the motor, and the gearbox. As a result of the power train <NUM> transmitting the power to the wheels according to the control signal Z, it is possible to accelerate or decelerate the vehicle.

The vehicle speed control part <NUM> carries out "deceleration limiting control" until a predetermined timing if the lane change estimation part <NUM> estimate that the vehicle will start a lane change, and the speed limit determination part <NUM> determines a reduction in the speed limit Vr. The "deceleration limiting control" means controlling the vehicle speed V using the upper-limit speed Vu as the upper-limit, the upper-limit speed Vu being determined by the upper-limit determination part <NUM> before the lane change estimation part <NUM> estimates that the vehicle will start a lane change. After the predetermined timing, the vehicle speed control part <NUM> controls the vehicle speed V using the upper-limit speed Vu as the upper-limit, the upper-limit speed Vu being currently determined by the upper-limit determination part <NUM>. Thus, even if the speed limit Vr is decreased when the vehicle carries out the lane change, the vehicle speed V is not limited to the reduced speed limit Vr but is temporarily limited to the upper-limit speed Vu determined before the start of the lane change is estimated. Therefore, it is possible to reduce a likelihood of the vehicle automatically decelerating against the driver's intention. "Determining a reduction in the speed limit Vr" can mean "determining that the speed limit Vr will decrease", and also, can mean "determining that the speed limit Vr has been decreased".

A hardware configuration of the vehicle speed control apparatus <NUM> will now be described. <FIG> illustrates an example of the hardware configuration of the vehicle speed control apparatus <NUM>.

As shown in <FIG>, the vehicle speed control apparatus <NUM> includes a Central Processing Unit (CPU) <NUM>, a Random Access Memory (RAM) <NUM>, a connection part <NUM>, and a Read-Only Memory (ROM) <NUM>. Note that these elements of the vehicle speed control apparatus <NUM> are mutually connected by a bus <NUM>.

The CPU <NUM> executes a program stored by the ROM <NUM> to implement the upper-limit determination part <NUM>, the vehicle speed control part <NUM>, and the excess determination part <NUM> described above with reference to <FIG>.

The RAM <NUM> is a main storage such as a Dynamic Random Access Memory (DRAM), a Static Random Access Memory (SRAM), or the like. The RAM <NUM> provides a work area where the program stored by the ROM <NUM> is expanded to be executed by the CPU <NUM>. Also, the RAM <NUM> provides a storage area to temporarily store information generated as a result of the execution by the CPU <NUM> of the program stored by the ROM <NUM>.

The connection part <NUM> is an interface that is connected to various connection destinations such as the vehicle speed detection part <NUM>, the speed limit determination part <NUM>, the lane change estimation part <NUM>, the other-lane vehicle speed measurement part <NUM>, the own-lane vehicle speed measurement part <NUM>, the depression amount detection part <NUM>, the vehicle speed control apparatus <NUM>, the power train <NUM>, and the reporting part <NUM>, and sends and receives various information items among these various connection destinations.

The ROM <NUM> is a main storage such as an Erasable Programmable ROM (EPROM), an Electrically Erasable Programmable ROM (EEPROM), or the like, and stores the program to be executed by the CPU <NUM>, and information used when the CPU <NUM> executes the program.

In <FIG>, it is assumed that the upper-limit speed Vu determined by the upper-limit determination part <NUM> before the lane change estimation part <NUM> estimates that the vehicle will start a lane change is <NUM> kph, for example. Also, it is assumed that, during the vehicle <NUM> carrying out a lane change while traveling at the vehicle speed V of <NUM> kph, the speed limit Vr is reduced from <NUM> kph, which is higher than the current vehicle speed V, to <NUM> kph, which is also higher than the current vehicle speed V. In this case, although the speed limit determination part <NUM> determines that the speed limit Vr is reduced from <NUM> kph to <NUM> kph during the vehicle <NUM> carrying out a lane change in a state of traveling at <NUM> kph, the vehicle speed control part <NUM> controls that the vehicle speed V does not exceed <NUM> kph until a predetermined timing.

In other words, the vehicle speed V after the speed limit Vr is reduced is not limited to be less than or equal to the reduced speed limit Vr that is <NUM> kph, but limited to be less than or equal to the upper-limit speed Vu, that is, <NUM> kph, from before start of the lane change is estimated, until the predetermined timing. Therefore, for immediately and smoothly completing the lane change, the driver is allowed to accelerate the vehicle <NUM> from <NUM> kph to <NUM> kph, thus exceeding <NUM> kph, until the predetermined timing, by depressing the accelerator pedal <NUM>.

Then, after the predetermined timing, the vehicle speed control part <NUM> controls the vehicle speed V using the upper-limit speed Vu (for example, <NUM> kph determined by the upper-limit determination part <NUM> according to the <NUM> kph that is the reduced speed limit Vr) as the upper-limit. Thereby, after the predetermined timing, the control is allowed to automatically return to such normal vehicle speed limiting control as to limit the vehicle speed V so that it does not exceed the upper-limit speed Vu (in this example, <NUM> kph) currently determined according to the currently determined speed limit Vr (in this example, <NUM> kph).

Thus, it is possible to reduce a likelihood that the vehicle automatically decelerates to a speed (in this example, <NUM> kph) different from the driver's intention.

Also, for example, in <FIG>, it is assumed that the upper-limit speed Vu determined by the upper-limit determination part <NUM> before the lane change estimation part <NUM> estimates that a lane change will start is <NUM> kph. However, now, it is assumed that, when the vehicle <NUM> changes lanes while traveling at the vehicle speed V of <NUM> kph, the speed limit Vr of the road is reduced from <NUM> kph, which is higher than the vehicle speed V, to <NUM> kph, which is lower than the vehicle speed V. In this case, although the speed limit determination part <NUM> determines that, when the vehicle <NUM> changes lanes while traveling at the vehicle speed V of <NUM> kph, the speed limit Vr is reduced from <NUM> kph to <NUM> kph, the vehicle speed control part <NUM> controls that the vehicle speed V does not exceed <NUM> kph, until the predetermined timing.

In other words, the vehicle speed V after the speed limit Vr is reduced is not limited to be less than or equal to the reduced speed limit Vr, i.e., <NUM> kph, but limited to be less than or equal to the upper-limit speed Vu before the start of the lane change was estimated, i.e., <NUM> kph, until the predetermined timing Therefore, as long as the driver depresses the accelerator pedal <NUM> with a constant depression amount, the driver can complete the lane change of the vehicle <NUM>, in a state where the vehicle <NUM> does not automatically decelerate from <NUM> kph to <NUM> kph against the driver's intention and the vehicle speed V is maintained at <NUM> kph, until the predetermined timing.

Then, after the predetermined timing, the vehicle speed control part <NUM> controls the vehicle speed V using the upper-limit speed Vu (for example, <NUM> kph determined by the upper-limit determination part <NUM> according to <NUM> kph, which is the reduced speed limit Vr) as the upper-limit. Thus, after the predetermined timing, the control is allowed to automatically return to such normal vehicle speed limiting control as to limit the vehicle speed V so that it does not exceed the upper-limit speed Vu (in this example, <NUM> kph) currently determined according to the currently determined speed limit Vr (in this example, <NUM> kph).

Thus, it is possible to reduce a likelihood that the vehicle automatically decelerates to a speed different from the driver's intention (in this example, <NUM> kph).

The vehicle speed control part <NUM> can carry out "deceleration limiting control" until a predetermined timing, if the lane change estimation part <NUM> estimates that the vehicle will start a lane change in front of another vehicle and the speed limit determination part <NUM> determines a reduction in the speed limit Vr. Note that "deceleration limiting control" means controlling the vehicle speed V using the upper-limit speed Vu as the upper-limit, the upper-limit speed Vu being determined by the upper-limit determination part <NUM> before the lane change estimation part <NUM> estimates that the vehicle will start a lane change. Thus, the vehicle speed V is not limited to be less than or equal to the reduced speed limit Vr. Therefore, it is possible to prevent the other vehicle following the vehicle from approaching the vehicle too much. After the predetermined timing, the vehicle speed control part <NUM> controls the vehicle speed V using the upper-limit speed Vu as the upper-limit. Here, the upper-limit speed Vu is one currently determined by the upper-limit determination part <NUM>.

For example, in <FIG>, the vehicle speed control part <NUM> carries out deceleration limiting control, until a predetermined timing, if the vehicle <NUM> is estimated to start a lane change in front of the other vehicle <NUM> and the speed limit Vr is determined as being reduced below the vehicle speed V. Thus, the vehicle speed control part <NUM> is capable of preventing the other vehicle <NUM> following the vehicle <NUM> from approaching the vehicle <NUM> too rapidly. In fact, if the vehicle <NUM> automatically decelerates to have a speed near the speed limit Vr as a result of the speed limit Vr being reduced below the vehicle speed V of the vehicle <NUM>, the other vehicle <NUM> following the vehicle <NUM> may approach the vehicle <NUM> rapidly.

Also, for example, in <FIG>, the vehicle speed control part <NUM> carries out deceleration limiting control, until a predetermined timing, if the vehicle <NUM> is estimated to start a lane change in front of the other vehicle <NUM> and the speed limit Vr is determined as being reduced to be lower than or equal to the vehicle speed Vc of the other vehicle <NUM>. Thereby, the vehicle speed control part <NUM> is capable of preventing the other vehicle <NUM> following the vehicle <NUM> from approaching the vehicle <NUM> too rapidly. In fact, if the vehicle <NUM> automatically decelerates to a speed near the speed limit Vr as a result of the speed limit Vr being reduced to be lower than or equal to the vehicle speed Vc of the other vehicle <NUM>, the other vehicle <NUM> following the vehicle <NUM> may approach the vehicle <NUM> rapidly. The vehicle speed Vc of the other vehicle <NUM> can be measured by the other-lane vehicle speed measurement part <NUM> before the lane change, and can be measured by the own-lane vehicle speed measurement part <NUM> after the lane change.

The above-mentioned cases where the speed limit Vr is reduced are not limited to cases where the speed limit Vr of the entire road on which the vehicle is traveling is reduced. The above-mentioned cases where the speed limit Vr is reduced can be also cases where the vehicle changes lanes from a lane having a higher speed limit Vr to a lane having a lower speed limit Vr. In the same way, a case where the speed limit Vr is increased is not limited to cases where the speed limit Vr of the entire road on which the vehicle is traveling is increased. The cases where the speed limit Vr is increased can be also cases where the vehicle changes lanes from a lane having a lower speed limit Vr to a lane having a higher speed limit Vr.

Also, the lane change estimation part <NUM> estimates that the vehicle will start a lane change in front of another vehicle, if a "moving direction detection part" detects that the vehicle moves in front of another vehicle. The "moving direction detection part" is a device that detects whether the vehicle moves in front of another vehicle. The moving direction detection part is, for example, capable of detecting whether the vehicle moves in front of another vehicle, based on relationships between the relative position of the other vehicle with respect to the vehicle, the vehicle speed V detected by the vehicle speed detection part <NUM>, and the vehicle speed Va of the other vehicle measured by the other-lane vehicle speed measurement part <NUM>. The relative position of the other vehicle with respect to the vehicle can be determined using, for example, a camera, a radar, a vehicle-vehicle communications, or the like. Any other method can also be used to estimate whether the vehicle will start a lane change in front of another vehicle.

In <FIG>, the vehicle speed control part <NUM> includes, for example, a speed command generation part <NUM>, an upper-limit command generation part <NUM>, a temporary command generation part <NUM>, and a speed adjustment part <NUM>.

The speed command generation part <NUM> is an example of a device that generates a speed command value X to control the vehicle speed V, according to the depression amount Ac of the accelerator pedal <NUM> detected by the depression amount detection part <NUM>.

The upper-limit command generation part <NUM> is an example of a device that generates a limit command value Y to control the vehicle speed V at the upper-limit speed Vu determined by the upper-limit determination part <NUM>.

The temporary command generation part <NUM> is an example of a device that generates a temporary command value W to control the vehicle speed V at the upper-limit speed Vu (hereinafter, referred to as a "temporary upper-limit speed Vw") determined by the upper-limit determination part <NUM> before the lane change estimation part <NUM> estimates that the vehicle will start a lane change. The temporary upper-limit speed Vw denotes an upper-limit speed temporarily used at a time of a lane change instead of the upper-limit speed Vu. The temporary command value W denotes a limit command value used temporarily at a time of a lane change instead of the limit command value Y.

The speed adjustment part <NUM> outputs a control signal Z to adjust the vehicle speed V according to the speed command value X generated by the speed command generation part <NUM> or the limit command value Y generated by the upper-limit command generation part <NUM>, whichever results in the lower vehicle speed V, during a period of time during which the lane change estimation part <NUM> does not estimate that the vehicle will carry out a lane change. The "period of time during which the lane change estimation part <NUM> does not estimate that the vehicle will carry out a lane change" denotes the above-mentioned other-than estimation period of time Tb, and, for example, a period of time during which the lane change estimation part <NUM> outputs the estimation signal Lc having the low level.

During a period of time during which the lane change estimation part <NUM> estimates that the vehicle will carry out a lane change, the speed adjustment part <NUM> outputs the control signal Z to adjust the vehicle speed V according to the speed command value X generated by the speed command generation part <NUM> or the temporary command value W generated by the upper-limit command generation part <NUM>, whichever results in the lower vehicle speed V. The "period of time during which the lane change estimation part <NUM> estimates that the vehicle will carry out a lane change" denotes the above-mentioned estimation period of time Ta, and, for example, a period of time during which the lane change estimation part <NUM> outputs the estimation signal Lc having the high level.

For example, the speed adjustment part <NUM> outputs the control signal Z to adjust the vehicle speed V according to the speed command value X, if, in the other-than estimation period of time Tb or the estimation period of time Ta, the command value X or Y/W, whichever results in the lower vehicle speed V, is the speed command value X. It can be said that the state where command value X or Y/W, whichever results in the lower vehicle speed V, is the speed command value X is the state where the speed determined by the depression amount AC of the accelerator pedal <NUM> (hereinafter, referred to as an "accelerator depression amount corresponding speed Vo") is less than the upper-limit speed Vu or the temporary upper-limit speed Vw. Therefore, if the command value X or Y/W, whichever results in the lower vehicle speed V, is the speed command value X, the speed adjustment part <NUM> is allowed to adjust the vehicle speed V at the accelerator depression amount corresponding speed Vo by adjusting the vehicle speed V according to the speed command value X, in a speed zone below the upper-limit speed Vu, or the temporary upper-limit speed Vw, without being limited by the upper-limit speed Vu or the temporary upper-limit speed Vw.

In contrast, the speed adjustment part <NUM> outputs the control signal Z to adjust the vehicle speed V according to the limit command value Y, if, in the other-than estimation period of time Tb, the command value X or Y, whichever results in the lower vehicle speed V, is the limit command value Y. It can be said that the state where the command value that results in the lower vehicle speed V being the limit command value Y is the state where the accelerator depression amount corresponding speed Vo is greater than the upper-limit speed Vu. Therefore, the vehicle speed V is maintained at the upper-limit speed Vu as a result of the speed adjustment part <NUM> adjusting the vehicle speed V according to the limit command value Y, if, in the other-than estimation period of time Tb, the command value that results in the lower vehicle speed V is the limit command value Y.

The speed adjustment part <NUM> outputs the control signal Z to adjust the vehicle speed V according to the temporary command value W, if, in the estimation period of time Ta, the command value X or W, whichever results in the lower vehicle speed V, is the temporary command value W. It can be said that, the state where the command value that results in the lower vehicle speed V being the temporary command value W is the state where the accelerator depression amount corresponding speed Vo is greater than the temporary upper-limit speed Vw. Therefore, if, in the estimation period of time Ta, the command value that results in the lower vehicle speed V is the temporary command value W, the vehicle speed V is maintained at the temporary upper-limit speed Vw as a result of the speed adjustment part <NUM> adjusting the vehicle speed V according to the temporary command value W.

If, in the other-than estimation period of time Tb, either one of the speed command value X and the limit command value Y results in the same vehicle speed V, the speed adjustment part <NUM> outputs the control signal Z to adjust the vehicle speed V according to a predetermined one of the speed command value X and the limit command value Y. It can be said that the state where either one of the speed command value X and the limit command value Y results in the same vehicle speed V is the state where the accelerator depression amount corresponding speed Vo is coincident with the upper-limit speed Vu. Therefore, if, in the other-than estimation period of time Tb, either one of the speed command value X and the limit command value Y results in the same vehicle speed V, the vehicle speed V is maintained at the upper-limit speed Vu, as a result of the speed adjustment part <NUM> adjusting the vehicle speed according to a predetermined one of the speed command value X and the limit command value Y.

The speed adjustment part <NUM> outputs the control signal Z to adjust the vehicle speed V according to a predetermined one of the speed command value X and the temporary command value W, if, in the estimation period of time Ta, either one of the speed command value X and the temporary command value W results in the same vehicle speed V. It can be said that the state where either one of the speed command value X and the temporary command value W results in the same vehicle speed V is the state where the accelerator depression amount corresponding speed Vo is coincident with the temporary upper-limit speed Vw. Therefore, if, in the estimation period of time Ta, either one of the speed command value X and the temporary command value W results in the same vehicle speed V, the vehicle speed V is maintained at the temporary upper-limit speed Vw as a result of the speed adjustment part <NUM> adjusting the vehicle speed V according to the predetermined one of the speed command value X and the temporary command value W.

For example, the speed command value X is a value to control the vehicle speed V at a target speed Vt corresponding to the depression amount Ac. In this case, the speed adjustment part <NUM> compares the target speed Vt and the upper-limit speed Vu in the other-than estimation period of time Tb. Then, if the target speed Vt is below the upper-limit speed Vu, the speed adjustment part <NUM> adjusts the vehicle speed V according to the speed command value X. If the target speed Vt is greater than or equal to the upper-limit speed Vu, the speed adjustment part <NUM> adjusts the vehicle speed V according to the limit command value Y. In the estimation period of time Ta, the speed adjustment part <NUM> compares the target speed Vt and the temporary upper-limit speed Vw. Then, if the target speed Vt is below the temporary upper-limit speed Vw, the speed adjustment part <NUM> adjusts the vehicle speed V according to the speed command value X. If the target speed Vt is greater than or equal to the temporary upper-limit speed Vw, the speed adjustment part <NUM> adjusts the vehicle speed V according to the temporary command value W.

For example, the speed command value X can be a value indicating a target acceleration At to control the vehicle speed V; the limit command value Y can be a value indicating a limit acceleration Ar to control the vehicle speed V at the upper-limit speed Vu; and the temporary command value W can be a value indicating a temporary acceleration Aw to control the vehicle speed V at the temporary upper-limit speed Vw. In this case, the speed adjustment part <NUM> compares the target acceleration At and the limit acceleration Ar in the other-than estimation period of time Tb. Then, if the target acceleration At is below the limit acceleration Ar, the speed adjustment part <NUM> adjusts the vehicle speed V according to the speed command value X. If the target acceleration At is greater than or equal to the limit acceleration Ar, the speed adjustment part <NUM> adjusts the vehicle speed V according to the limit command value Y. In the estimation period of time Ta, the speed adjustment part <NUM> compares the target acceleration At and the temporary acceleration Aw. Then, if the target acceleration At is below the temporary acceleration Aw, the speed adjustment part <NUM> adjusts the vehicle speed V according to the speed command value X. If the target acceleration At is greater than or equal to the temporary acceleration Aw, the speed adjustment part <NUM> adjusts the vehicle speed V according to the temporary command value W. The target acceleration At, the limit acceleration Ar, and the temporary acceleration Aw are accelerations of the vehicle itself.

For example, the speed command value X can be a value indicating a target driving force Dt to control the vehicle speed V; the limit command value Y can be a value indicating a limit driving force Dr to control the vehicle speed V at the upper-limit speed Vu; and the temporary command value W can be a value indicating a temporary driving force Dw to control the vehicle speed V at the temporary upper-limit speed Vw. In this case, the speed adjustment part <NUM> compares the target driving force Dt and the limit driving force Dr in the other-than estimation period of time Tb. Then, if the target driving force Dt is below the limit driving force Dr, the speed adjustment part <NUM> adjusts the vehicle speed V according to the speed command value X. If the target driving force Dt is greater than or equal to the limit driving force Dr, the speed adjustment part <NUM> adjusts the vehicle speed V according to the limit command value Y. In the estimation period of time Ta, the speed adjustment part <NUM> compares the target driving force Dt and the temporary driving force Dw. Then, if the target driving force Dt is below the temporary driving force Dw, the speed adjustment part <NUM> adjusts the vehicle speed V according to the speed command value X. If the target driving force Dt is greater than or equal to the temporary driving force Dw, the speed adjustment part <NUM> adjusts the vehicle speed V according to the temporary command value W. The target driving force Dt, the limit driving force Dr, and the temporary driving force Dw are driving outputs of the driving source (for example, an engine, a motor, or the like) to drive the wheels of the vehicle.

For example, the speed command value X can be a value indicating a target throttle valve opening St to control the vehicle speed V; the limit command value Y can be a value indicating a limit throttle valve opening Sr to control the vehicle speed V at the upper-limit speed Vu; and the temporary command value W can be a value indicating a temporary throttle valve opening Sw to control the vehicle speed V at the temporary upper-limit speed Vw. In this case, the speed adjustment part <NUM> compares the target throttle valve opening St and the limit throttle valve opening Sr in the other-than estimation period of time Tb. Then, if the target throttle valve opening St is below the limit throttle valve opening Sr, the speed adjustment part <NUM> adjusts the vehicle speed V according to the speed command value X. If the target throttle valve opening St is greater than or equal to the limit throttle valve opening Sr, the speed adjustment part <NUM> adjusts the vehicle speed V according to the limit command value Y. In the estimation period of time Ta, the speed adjustment part <NUM> compares the target throttle valve opening St and the temporary throttle valve opening Sw. Then, if the target throttle valve opening St is below the temporary throttle valve opening Sw, the speed adjustment part <NUM> adjusts the vehicle speed V according to the speed command value X. If the target throttle valve opening St is greater than or equal to the temporary throttle valve opening Sw, the speed adjustment part <NUM> adjusts the vehicle speed V according to the temporary command value W. The target throttle valve opening St, the limit throttle valve opening Sr, and the temporary throttle valve opening Sw are the openings of the throttle valve to adjust the intake air quantity of the engine of the vehicle.

For example, the speed command value X can be a value indicating a target engine speed Rt to control the vehicle speed V; the limit command value Y can be a value indicating a limit engine speed Rr to control the vehicle speed V at the upper-limit speed Vu; and the temporary command value W can be a value indicating a temporary engine speed Rw to control the vehicle speed V at the temporary upper-limit speed Vw. In this case, the speed adjustment part <NUM> compares the target engine speed Rt and the limit engine speed Rr in the other-than estimation period of time Tb. Then, if the target engine speed Rt is below the limit engine speed Rr, the speed adjustment part <NUM> adjusts the vehicle speed V according to the speed command value X. If the target engine speed Rt is greater than or equal to the limit engine speed Rr, the speed adjustment part <NUM> adjusts the vehicle speed V according to the limit command value Y. In the estimation period of time Ta, the speed adjustment part <NUM> compares the target engine speed Rt and the temporary engine speed Rw. Then, if the target engine speed Rt is below the temporary engine speed Rw, the speed adjustment part <NUM> adjusts the vehicle speed V according to the speed command value X. If the target engine speed Rt is greater than or equal to the temporary engine speed Rw, the speed adjustment part <NUM> adjusts the vehicle speed V according to the temporary command value W. The target engine speed Rt, the limit engine speed Rr, and the temporary engine speed Rw are the engine speeds of the vehicle.

In <FIG>, the speed adjustment part <NUM> of the vehicle speed control part <NUM> sends information indicating that a vehicle speed V temporarily exceeding the upper-limit speed Vu at a time of a lane change will be allowed, to the excess determination part <NUM>. If information indicating allowance of the vehicle speed V to temporarily exceed the upper-limit speed Vu is received, the excess determination part <NUM> determines whether the current vehicle speed V actually exceeds the upper-limit speed Vu. When the excess determination part <NUM> determines that the vehicle speed V actually exceeds the upper-limit speed Vu, the excess determination part <NUM> reports the driver that the vehicle speed V exceeds the upper-limit speed Vu (that can be the speed limit Vr) through the reporting part <NUM>. Thus, it is possible to report the driver that the upper-limit speed Vu or the speed limit Vr is exceeded. The reporting part <NUM> warns that the upper-limit speed Vu or the speed limit Vr is exceeded in such a manner as to cause the driver to be able to determine that the upper-limit speed Vu or the speed limit Vr is exceeded through, for example, at least one of an indication, a sound, a vibration, and so forth.

<FIG> is a flowchart illustrating an example of operations of the vehicle speed control apparatus <NUM>. The vehicle speed control apparatus <NUM> repeats a vehicle speed limiting method shown in the flowchart every predetermined cycle. <FIG> is an example of a flowchart to be executed subsequent to the flowchart of <FIG>.

In step S10 of <FIG>, the vehicle speed control part <NUM> determines whether the lane change estimation part <NUM> estimates that the vehicle will start a lane change.

When the vehicle speed control part <NUM> determines in step S10 that the lane change estimation part <NUM> does not estimate that the vehicle will start a lane change (NO), the vehicle speed control part <NUM> proceeds to step S20. The vehicle speed control part <NUM> controls, in step S20, the vehicle speed V in such a manner as to not exceed the upper-limit speed Vu even if the depression amount Ac of the accelerator pedal <NUM> would increase the vehicle speed V over the upper-limit speed Vu. After executing step S20, the vehicle speed control part <NUM> returns to step S10.

On the other hand, the vehicle speed control part <NUM> proceeds to step S50 when the vehicle speed control part <NUM> determines in step S10 that the lane change estimation part <NUM> estimates that the vehicle will start a lane change (YES).

In step S50, after the lane change estimation part <NUM> estimates that the vehicle will start a lane change, the vehicle speed control part <NUM> determines whether the speed limit determination part <NUM> determines a reduction in the speed limit Vr. If the speed limit determination part <NUM> does not determine in step S50 a reduction in the speed limit Vr (NO), the vehicle speed control part <NUM> controls that the vehicle speed V does not exceed the upper-limit speed Vu (step S20). But, if the speed limit determination part <NUM> determines in step S50 a reduction in the speed limit Vr (YES), the vehicle speed control part <NUM> controls that the vehicle speed V does not exceed the upper-limit speed determined before the lane change (that is, the temporary upper-limit speed Vw) (step S60).

In step S90, the excess determination part <NUM> determines whether the vehicle speed V exceeds the upper-limit speed Vu. If the vehicle speed V exceeds the upper-limit speed Vu, the excess determination part <NUM> reports the driver that the upper-limit speed Vu (that can be the speed limit Vr) is exceeded through the reporting part <NUM> (step S100). On the other hand, if the vehicle speed V does not exceed the upper-limit speed Vu, the excess determination part <NUM> does not report the driver that the upper-limit speed Vu and the speed limit Vr are exceeded (step S110). Note that steps S90, S100 and S110 can be skipped.

In this case, the vehicle speed control part <NUM> executes steps S120, S130 and S140 of <FIG>, in parallel, after step S60.

If any one of the determination conditions of steps S120, S130 and S140 is satisfied (YES), the vehicle speed control part <NUM> determines that it becomes less necessary to control the vehicle speed V using the temporary upper-limit speed Vw as the upper-limit and it is a timing to stop controlling the vehicle speed V using the temporary upper-limit speed Vw as the upper-limit. Therefore, the vehicle speed control part <NUM> stops controlling the vehicle speed V using the temporary upper-limit speed Vw as the upper-limit, and proceeds to step S20.

In contrast, if none of the determination conditions of step S120, S130 and S140 is satisfied (NO), the vehicle speed control part <NUM> determines that it is still necessary to control the vehicle speed V using the temporary upper-limit speed Vw as the upper-limit, and it is not a timing to stop controlling the vehicle speed V using the temporary upper-limit speed Vw as the upper-limit. Therefore, the vehicle speed control part <NUM> continues controlling the vehicle speed V using the temporary upper-limit speed Vw as the upper-limit (step S60).

In step S120, the vehicle speed control part <NUM> determines whether the lane change estimation part <NUM> estimates that the vehicle has finished the lane change. When the vehicle speed control part <NUM> determines that the lane change estimation part <NUM> estimates that the vehicle has finished the lane change (NO), the vehicle speed control part <NUM> stops controlling the vehicle speed V using the temporary upper-limit speed Vw as the upper-limit, and controls that the vehicle speed V does not exceed the upper-limit speed Vu (step S20).

In step S130, if the vehicle carries out the lane change in front of another vehicle, the vehicle speed control part <NUM> determines whether the speed limit Vr is less than or equal to the vehicle speed Vc of the other vehicle in the destination lane of the lane change. For example, in <FIG>, if, as described above, the vehicle <NUM> carries out a lane change in front of the other vehicle <NUM>, and the vehicle speed V of the vehicle <NUM> is decreased to around the speed limit Vr as a result of the speed limit Vr being reduced to be less than or equal to the vehicle speed Vc, a likelihood that the other vehicle <NUM> following the vehicle <NUM> rapidly approaches the vehicle <NUM> increases.

Therefore, when the vehicle speed control part <NUM> determines in step S130 that the speed limit Vr will become less than or equal to the vehicle speed Vc of another vehicle if the vehicle carries out the lane change in front of the other vehicle under the condition where none of steps S120 and S140 is satisfied (NO), the vehicle speed control part <NUM> continues controlling the vehicle speed V using the temporary upper-limit speed Vw as the upper-limit (step S60). On the other hand, when the vehicle speed control part <NUM> determines in step S130 that the speed limit Vr is greater than the vehicle speed Vc of another vehicle if the vehicle carries out the lane change in front of the other vehicle (YES), the vehicle speed control part <NUM> stops controlling the vehicle speed V using the temporary upper-limit speed Vw as the upper-limit, and controls that the vehicle speed V does not exceed the upper-limit speed Vu (step S20).

When the vehicle speed control part <NUM> determines in step S130 that the speed limit Vr is greater than or equal to the vehicle speed Vc if the vehicle carries out the lane change to the rear of the other vehicle under the condition where none of steps S120 and S140 is satisfied (NO), the vehicle speed control part <NUM> continues controlling the vehicle speed V using the temporary upper-limit speed Vw as the upper-limit (step S60). On the other hand, when the vehicle speed control part <NUM> determines in step S130 that the speed limit Vr is less than the vehicle speed Vc if the vehicle carries out the lane change to the rear of the other vehicle (YES), the vehicle speed control part <NUM> stops controlling the vehicle speed V using the temporary upper-limit speed Vw as the upper-limit, and controls that the vehicle speed V does not exceed the upper-limit speed Vu (step S20).

In step S140, the vehicle speed control part <NUM> determines whether the vehicle speed V is decreased below the speed limit Vr after exceeding the speed limit Vr. When the vehicle speed control part <NUM> determines that the vehicle speed V is decreased below the speed limit Vr after exceeding the speed limit Vr, the vehicle speed control part <NUM> stops controlling the vehicle speed V using the temporary upper-limit speed Vw as the upper-limit, and controls that the vehicle speed V does not exceed the upper-limit speed Vu (step S20).

Thus, the vehicle speed control apparatuses and the vehicle limiting apparatuses have been described in the embodiments. However, the present invention is not limited to these embodiments. Various modifications and/or improvements such as combinations with part or all of another embodiment(s), a replacement(s) with part of another embodiment(s), and so forth, can be made without departing from the claimed invention as defined by the appended claims.

Claim 1:
A vehicle speed limiting apparatus (<NUM>) comprising:
a vehicle speed control apparatus (<NUM>):
a depression amount detection part (<NUM>) that is configured to detect the vehicle's accelerator pedal depression amount;
a speed limit determination part (<NUM>) that is configured to determine the speed limit of the road on which the vehicle is traveling; and
an estimation part (<NUM>) that is configured to estimate the start of the vehicle's lane change;
the vehicle speed control apparatus (<NUM>) comprising:
an upper-limit determination part (<NUM>) that is configured to determine an upper-limit speed of the vehicle according to the speed limit of the road determined by the speed limit determination part (<NUM>); and
a vehicle speed control part (<NUM>) that is configured to control a speed of the vehicle according to a speed command value generated according to the depression amount of the vehicle's accelerator pedal or a speed command value generated according to the upper-limit speed, whichever results in a lower vehicle speed,
the vehicle speed limiting apparatus being characterized in that the vehicle speed control part (<NUM>) is configured to control a speed of the vehicle according to the speed command value generated according to the depression amount of the vehicle's accelerator pedal or a speed command value generated according to the upper-limit speed that is determined by the upper-limit determination part (<NUM>) before a start of the vehicle's lane change is estimated by the estimation part (<NUM>), whichever results in a lower vehicle speed, during a period of time during which the estimation part estimates the vehicle's lane change and the speed limit determination part (<NUM>) determines a reduction of the speed limit.