JPH07172211A - Speed control for automobile - Google Patents

Abstract

PURPOSE:To accurately and quickly adjust a desired distance between cars by controlling car speed so that the relative speed between driver's own car and preceding one is set to a predetermined value when a change-over switch is changed over to ON and carrying out between-car type feed back control with the between-car distance set as the desired distance between cars when the switch is changed to OFF. CONSTITUTION:A vehicle speed sensor 12, set switch 20 for setting desired vehicle speed, proximity switch 21, separation switch 22, acceleration switch 24 are provided, and the detecting signals of these switches 20-24 are inputted to a control unit 4. When the proximity switch 21 is changed over to ON position, proximity control is carried out to make the car approach the preceding car while the relative speed between the car and the preceding car is kept at a predetermined value. When the separation switch 22 is changed over to ON, the separation control is carried out for the preceding car while relative speed is kept at the predetermined value. A distance between both cars when the proximity switch 21 or separation switch 22 is changed over to the OFF position is set to a desired distance between both cars.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle speed control method for controlling the vehicle speed of an automobile.

[0002]

2. Description of the Related Art Conventionally, as a method of controlling a vehicle speed of an automobile, a vehicle speed feedback control for keeping a vehicle speed of an own vehicle constant and an inter-vehicle feedback for keeping an inter-vehicle distance between an own vehicle and a preceding vehicle constant are provided. Some control. As the latter, for example, Japanese Patent Application Laid-Open No. 58-213313 discloses a radar device for detecting the actual inter-vehicle distance between the host vehicle and the preceding vehicle, and control for controlling the vehicle speed by adjusting the throttle opening of the engine and the like. It is disclosed that the vehicle speed control is performed so that the actual vehicle-to-vehicle distance becomes a target vehicle-to-vehicle distance set by the driver. In addition, the actual development Sho 60-14419
Japanese Unexamined Patent Publication No. 9 and Japanese Patent Application Laid-Open No. 61-6031 disclose that a driver can adjust a target inter-vehicle distance.

Further, Japanese Patent Laid-Open No. 61-150835 discloses a vehicle speed feedback control and an inter-vehicle feedback control which both perform a vehicle speed feedback control before the vehicle speed loss when the preceding vehicle is lost during the vehicle-interval feedback control. It is disclosed that the vehicle speed is changed to the target vehicle speed of the feedback control when the driver performs an operation for shifting to the vehicle speed type feedback control.

[0004]

By the way, there are various problems when changing the target inter-vehicle distance of the inter-vehicle feedback control or the target vehicle speed of the vehicle speed feedback control.

That is, when the target vehicle distance of the inter-vehicle feedback control changes, and the degree of approach of the host vehicle to the preceding vehicle changes momentarily, the target vehicle distance may not be adjusted exactly as desired. is there. Also,
It is not appropriate to control the host vehicle so that the target vehicle gradually approaches the preceding vehicle while changing the target inter-vehicle distance because the time required to change the target inter-vehicle distance becomes long. In addition, because the running stability of the vehicle varies depending on the road environment such as the friction coefficient of the road surface and the curvature of the road, the target vehicle speed of the vehicle speed feedback control is changed, and the acceleration / deceleration when the vehicle speed changes accordingly. It is not appropriate to uniformly set

The present invention has been made in view of the above points, and an object of the present invention is to appropriately perform vehicle speed control when changing a target vehicle distance of inter-vehicle feedback control or a target vehicle speed of vehicle speed feedback control. You can set the target inter-vehicle distance accurately and quickly as desired,
Alternatively, another object of the present invention is to provide a vehicle speed control method for an automobile that can ensure traveling stability when the target vehicle speed is changed.

[0007]

In order to achieve the above object, the invention according to claim 1 is as a vehicle speed control method for an automobile which performs at least an inter-vehicle feedback control for keeping a constant inter-vehicle distance between a vehicle and a preceding vehicle. An ON-OFF switch for changing the target inter-vehicle distance of the inter-vehicle feedback control is provided, and when the switch is switched to the ON position, the vehicle speed is controlled so that the relative speed between the own vehicle and the preceding vehicle becomes a predetermined value. The inter-vehicle feedback control is performed with the inter-vehicle distance when the switch is switched to the OFF position from this state as the target inter-vehicle distance. Here, in the invention according to claim 2, the predetermined value is set to a larger value as the inter-vehicle distance between the own vehicle and the preceding vehicle before the change is longer.

According to a third aspect of the present invention, as a vehicle speed control method for an automobile that performs at least a vehicle-to-vehicle feedback control for keeping a vehicle-to-vehicle distance between a vehicle and a preceding vehicle constant, a target vehicle-to-vehicle distance of the vehicle-to-vehicle feedback control is a predetermined distance. A switch for changing is provided, and when the target inter-vehicle distance is changed by the switch, the vehicle speed is controlled so that the relative speed between the own vehicle and the preceding vehicle is increased first and then the relative speed is decreased. Here, in the invention according to claim 4, the initial relative speed at the time of changing the target inter-vehicle distance is set to a larger value as the changing distance is longer.

According to a fifth aspect of the present invention, as a vehicle speed control method of a vehicle for performing at least a vehicle speed feedback control for maintaining a constant vehicle speed, a switch for changing a target vehicle speed of the vehicle speed feedback control is provided, and the target vehicle speed by the switch is provided. The configuration is such that the acceleration / deceleration when the vehicle speed changes due to the change of is changed according to the road environment.

[0010]

With the above construction, in the invention according to claim 1,
When the target inter-vehicle distance of the inter-vehicle feedback control is changed by the ON-OFF switch, first, when the switch is switched to the ON position, the relative speed between the own vehicle and the preceding vehicle becomes a predetermined value, that is, the preceding vehicle. The vehicle speed is controlled so that the degree of approach of the host vehicle with respect to is constant, and in this state, the switch is turned to the OFF position, and the inter-vehicle distance at that time is used as the target inter-vehicle distance to perform the inter-vehicle feedback control. Can be ensured as desired.

Here, unlike the actual approaching degree, the approaching degree felt by the driver when the inter-vehicle distance is changed is higher when the inter-vehicle distance between the own vehicle and the preceding vehicle is shorter than when it is long. Therefore, in the invention according to claim 2, the predetermined value is set to a larger value as the inter-vehicle distance between the own vehicle and the preceding vehicle before the change is longer.
The driver feels that the degree of approach is constant regardless of the actual inter-vehicle distance, and does not give the driver any anxiety.

According to the third aspect of the present invention, when the target inter-vehicle distance of the inter-vehicle feedback control is changed by the switch by a predetermined distance, first the relative speed between the own vehicle and the preceding vehicle is increased,
After that, the vehicle speed is controlled so as to reduce the relative speed, so that it is possible to surely change the inter-vehicle distance as desired and to shorten the time required for the change. In particular, in the invention according to claim 4, since the initial relative speed at the time of changing the target inter-vehicle distance is set to a larger value as the distance to be changed is longer, the time required for the change can be further shortened.

According to the fifth aspect of the invention, when the target vehicle speed of the vehicle speed type feedback control is changed by the switch,
Since the acceleration / deceleration when the vehicle speed changes in accordance with the change is changed according to the road environment, the running stability is always good regardless of the road environment.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the overall construction of a vehicle speed control system for a vehicle for carrying out a vehicle speed control method according to an embodiment of the present invention. Reference numeral 1 denotes an engine intake system throttle valve (not shown).
Is a throttle control device for automatically adjusting the opening degree of the control device, 2 is a control device for an electronically controlled automatic transmission (EAT), and 3 is a brake control device for automatically adjusting the braking force applied to each wheel.
Although not shown, each of these three types of control devices 1 to 3 has an actuator, and each actuator is
It is controlled by the control unit 4. That is,
The control unit 4 outputs a target throttle opening signal to the actuator of the throttle control device 1 for control, and outputs a target brake amount signal to the actuator of the brake control device 3 for control.
The control unit 4 receives a shift position signal from a sensor (not shown) for detecting the shift position of the EAT control device 2 and outputs a shift control signal to an actuator of the EAT control device 2 to perform control. .

Reference numeral 6 denotes an information display device provided on an instrument panel or the like in the vehicle compartment. The information display device 6 is turned on upon receiving an alarm signal from the control unit 4 although not shown. An alarm lamp and a display unit for displaying a screen upon receiving a self-diagnosis signal from the control unit 4 are provided. Reference numeral 7 denotes a radar device for detecting an obstacle existing in front of the own vehicle such as a preceding vehicle. In the case of the present embodiment, the radar device 7 transmits far infrared rays as a radar wave toward the front of the own vehicle. In addition, it is configured to receive the reflected wave reflected by the preceding vehicle and measure the distance between the own vehicle and the obstacle by the time difference between the reception time and the transmission time. A certain inter-vehicle distance signal is input to the control unit 4.

Further, 11 is a throttle opening sensor for detecting the opening of the throttle valve, 12 is a vehicle speed sensor for detecting the vehicle speed, 13 is a steering angle sensor for detecting the steering angle of the steering wheel, 1
Reference numeral 4 is a yaw rate sensor for detecting the yaw rate generated in the vehicle, 15 is a road surface μ sensor for detecting the friction coefficient μ of the road surface, 16 is a light intensity sensor for detecting the brightness outside the vehicle, and 17 is ON when the brake pedal is depressed. Brake switch, 18 is a clutch switch that is turned on according to the operating state of the clutch, 19 is a main switch for starting auto cruise, 20 is a set switch for the driver to set a target vehicle speed, and 21 is inter-vehicle feedback. An approach switch for changing the target inter-vehicle distance of the control to the approach direction, 22 is a separation switch for changing the target inter-vehicle distance of the inter-vehicle feedback control to the separation direction, and 23 is a target vehicle speed of the vehicle speed feedback control for the acceleration direction. An acceleration switch for changing, 24 is a deceleration method for the target vehicle speed of the vehicle speed type feedback control This is a deceleration switch for changing the direction, and the detection signals of these sensor switches 11 to 24 are all input to the control unit 4.
Further, each of the switches 17 to 24 is ON-O.
It consists of an FF selector switch. Incidentally, detection signals of other sensors and switches (not shown) such as an engine speed sensor are also input to the control unit 4.

The vehicle speed control method according to one embodiment of the present invention is used for the vehicle speed control by the control unit 4, and this vehicle speed control is performed according to the flow charts shown in FIGS. Hereinafter, these flowcharts will be sequentially described.

FIG. 2 shows a main routine of vehicle speed control by the control unit 4. In this figure, after starting, it is first determined in step S1 whether or not the driver has turned on the main switch 19 to start the auto cruise. If this determination is NO, the set flag Fset is set in step S7. Is cleared, step S8
After deactivating the auto cruise with, return.

On the other hand, when the determination in step S1 is YES, it is determined in step S2 whether or not the set switch 20 is turned on. When this judgment is NO, it is judged in step S6 whether or not the set flag Fset is set. Since the set flag Fset is not set unless the set switch 20 is turned on (step S3), when the set switch 20 is turned off, the process proceeds to step S8 and the automatic cruise is deactivated. Therefore, in the case of the present embodiment, in order to actually start the auto cruise, not only the driver pushes the main switch 19 to turn it on, but also the set switch 2
It is necessary to press 0 once to turn it on.

When the determination in step S2 is YES,
That is, when the set switch 20 is pressed to be turned on, the set flag Fset is set in step S3,
After the vehicle speed v at the time when the set switch 20 is pressed is set to the target vehicle speed TGV in step S4, the automatic cruise is activated in step S5 and the process returns. Even when the set switch 20 is turned on once and then turned off again, the set flag Fset remains set unless the main switch 19 is turned off.
→ Step S2 → Step S6 → Step S5, and the auto cruise operation is performed.

FIG. 3 shows a subroutine of the automatic cruise operation (step S5). In FIG. 3, first, in step S11, it is determined whether or not the radar device 7 detects a preceding vehicle within a predetermined distance range from the own vehicle, and step S12
Then, it is determined whether or not the inter-vehicle feedback control (following traveling) mode is selected by the manual switch (not shown). If either of the above determinations is NO, vehicle speed feedback control for maintaining the vehicle speed constant is performed in step S16, and the process returns.

When both the determinations in step S11 and step S12 are YES, the target inter-vehicle distance for inter-vehicle feedback control is set in step S13 using the map shown in FIG. In the map shown in FIG. 7, the target inter-vehicle distance increases like a quadratic curve as the vehicle speed of the preceding vehicle (the preceding vehicle speed) increases. Subsequently, after changing the target inter-vehicle distance in step S14, inter-vehicle feedback control for controlling the vehicle speed is executed to maintain the actual inter-vehicle distance between the own vehicle and the preceding vehicle at the target inter-vehicle distance in step S15, and then the return is performed. To do.

FIG. 4 shows a subroutine for changing the target inter-vehicle distance (step S14). In FIG. 4, first, in step S21, it is determined whether or not the approach switch 21 is switched to the ON position, and in step S22, it is similarly determined whether or not the separation switch 22 is switched to the ON position. When neither the approach switch 21 nor the separation switch 22 has been switched to the ON position, the target inter-vehicle distance is not changed (step S27) and the process returns.

On the other hand, when the approach switch 21 is switched to the ON position, the vehicle speed is controlled so that the own vehicle approaches the preceding vehicle while the relative speed between the own vehicle and the preceding vehicle is maintained at a predetermined value in step S23. (Approach control). When the separation switch 22 is switched to the ON position, vehicle speed control (separation control is performed so that the own vehicle separates from the preceding vehicle in a state where the relative speed between the own vehicle and the preceding vehicle is maintained at a predetermined value in step S24. )I do. The predetermined value of the relative speed becomes larger as the inter-vehicle distance between the own vehicle and the preceding vehicle becomes longer, as shown by the solid line K1 and the broken line K2 in FIG. 8 in both the approach control and the separation control. Is set to.

After the approach control or the separation control is performed, it waits for the approach switch 21 or the separation switch 22 to be switched from the ON position to the OFF position in step S25. Then, the inter-vehicle distance between the host vehicle and the preceding vehicle when the vehicle is switched to the OFF position in step S26 is set as the target inter-vehicle distance, and the process returns.

Here, the inter-vehicle feedback control mode is, for example, as shown in FIG. 9, an area A where the relative speed between the own vehicle and the preceding vehicle is large in the positive direction (approaching direction) and the degree of danger is high.
In this case, the alarm is activated by the operation of the information display device 6 and the braking is activated by the operation of the brake control device 3, so that the risk of B is medium.
In the area, braking by the operation of the brake control device 3 and EAT
The shift down is performed by the operation of the control device 2, and only the throttle opening adjustment by the operation of the throttle control device 1 is performed in the C region where the degree of risk is low. In FIG. 9, the vehicle speed control is performed when the inter-vehicle distance between the own vehicle and the preceding vehicle is a predetermined value or more.

5 and 6 show a subroutine of the vehicle speed type feedback control (step S16 in FIG. 3).
In FIG. 5, first, in step S31, as the road environment,
Road friction coefficient μ detected by the road surface μ sensor 15, outside brightness lx detected by the light intensity sensor 16, curvature radius R of the road
And the road width B are read. Here, the radius of curvature R of the road
Is regarded as equal to the turning radius of the own vehicle, and R = (1 + A × v ² ) × N × L / (v × θ) based on the steering angle θ of the own vehicle and the vehicle speed V 0 by the following formula. It is calculated. However, A is a stability factor, N is a steering gear ratio, and L is a wheel base. Also,
The road width B is input by a driver using a manual switch, or automatically read by the radar device 7 from the positions of reflectors provided on guide rails at the left and right ends of the road, for example.

Subsequently, in steps S32 to S35, the correction coefficient a1 based on the friction coefficient μ of the road surface, the correction coefficient a2 based on the brightness lx outside the vehicle, the correction coefficient a3 based on the radius of curvature R of the road, and the road width B are set. Based correction coefficient a4
Set each from the map. Here, the correction coefficient a1
Is 1 in the region where the friction coefficient μ of the road surface is higher than μ 1, and is set to be gradually smaller than 1 because the friction coefficient μ of the road surface becomes lower than μ 1. The correction coefficient a2 is set to 1 in a region where the brightness lx outside the vehicle is larger than lx1, and the brightness lx outside the vehicle is set to be smaller than 1x1. The correction coefficient a3 is set to 1 in the region where the radius of curvature R of the road is larger than R1, and is set to gradually become smaller than 1 because the radius of curvature R of the road becomes smaller than R1. The correction coefficient a4 is 1 in a region where the road width B is larger than B1, and becomes smaller than 1 as the road width B becomes smaller than B1.
Is set to a predetermined value k (1>k> 0) in an area smaller than B2.

After setting the four types of correction coefficients a1 to a4, these correction coefficients a1 to a4 are integrated with the reference acceleration / deceleration G0 to calculate the acceleration / deceleration G in step S36. That is, the acceleration / deceleration G is G = G0 * a1 * a2 * a3 * a4. Then, the process proceeds to step S37 in FIG.

In FIG. 6, it is determined in step S37 whether the deceleration switch 24 is switched to the ON position, and in step S38 it is determined whether the acceleration switch 23 is switched to the ON position. When neither the deceleration switch 24 nor the acceleration switch 23 has been switched to the ON position, the target vehicle speed TGV remains unchanged (step S4 in FIG. 2) and the process returns.

On the other hand, when the deceleration switch 24 is switched to the ON position, the above deceleration (-
Decelerate with G). When the acceleration switch 23 is switched to the ON position, the acceleration G
Accelerate with. After such acceleration or deceleration, step S
At 41, wait until the deceleration switch 24 or the acceleration switch 23 is switched from the ON position to the OFF position. Then, in step S42, the own vehicle speed v when the vehicle is switched to the OFF position is updated as the target vehicle speed TGV, the vehicle speed is controlled so as to keep the vehicle speed at the target vehicle speed TGV, and the process returns.

As described above, in the above-described embodiment, when the target inter-vehicle distance is changed to the approaching direction by the approaching switch 21 or the leaving direction by the separating switch 22 during the inter-vehicle feedback control, the approaching switch 21 or When the separation switch 22 is switched to the ON position, the vehicle speed is controlled so that the relative speed between the own vehicle and the preceding vehicle becomes a predetermined value, that is, the degree of approach or separation of the own vehicle from the preceding vehicle becomes constant. In this state, the approach switch 21 or the separation switch 22 is switched to the OFF position, and the inter-vehicle feedback control is performed with the inter-vehicle distance between the host vehicle and the preceding vehicle at that time as the target inter-vehicle distance, so that the target inter-vehicle distance can be changed as desired. Can be done.

Here, the approaching degree (approaching degree or approaching degree) that the driver feels when the inter-vehicle distance is changed is different from the actual approaching degree, and when the inter-vehicle distance between the own vehicle and the preceding vehicle is shorter than that when the inter-vehicle distance is long. Become higher. In response to this, in this embodiment, the predetermined value is set to a larger value as the inter-vehicle distance between the own vehicle and the preceding vehicle before the change is longer (see FIG. 8).
Therefore, when the inter-vehicle distance is changed, the driver feels that the approaching degree is constant regardless of the actual inter-vehicle distance, and does not give the driver any anxiety.

Further, when the target vehicle speed TGV is changed to the acceleration direction by the acceleration switch 23 or to the deceleration direction by the deceleration switch 24 during the vehicle speed type feedback control, the acceleration / deceleration G when the vehicle speed changes with the change. Change according to the road environment. That is, when the friction coefficient μ of the road surface is low, the acceleration / deceleration G becomes smaller than when it is high, and when the outside of the vehicle is dark, the acceleration / deceleration G becomes smaller than when it is bright, and the radius of curvature R of the road is relatively small. The acceleration / deceleration G on the road is smaller than that on the straight road, and the acceleration / deceleration G on the road with a narrow road width B is smaller than that on the wide road. Therefore, the running stability is always improved. can do.

In the above embodiment, when the target inter-vehicle distance of the inter-vehicle feedback control is changed, it is turned on and off.
Although the approach switch 21 and the separation switch 22 which are changeover switches are used, the present invention is also applied to the case where the target inter-vehicle distance is changed by a switch such as a rotary switch instead of the ON-OFF changeover switch. can do. In this case, the vehicle speed is controlled so that the relative speed between the own vehicle and the preceding vehicle is increased at the beginning of the change, and then the relative speed is decreased. As a result, it is possible to surely change the inter-vehicle distance as desired, and it is possible to shorten the time required for the change. In particular, if the initial relative speed at the time of change is set to a larger value as the distance to be changed is longer, the time required for the change can be shortened as much as possible without making the driver feel uneasy.

[0037]

As described above, according to the first aspect of the invention, when the target inter-vehicle distance of the inter-vehicle feedback control is changed by the ON-OFF changeover switch, first, when the switch is changed over to the ON position, it is preceded. The vehicle speed is controlled so that the degree of approach of the host vehicle to the vehicle becomes constant, and in this state, the switch is turned to the OFF position, and the inter-vehicle distance at that time is used as the target inter-vehicle distance to perform the inter-vehicle feedback control. Changes can be made reliably as desired.

In particular, according to the second aspect of the present invention, the degree of approach that the driver feels when changing the inter-vehicle distance can be made constant regardless of the actual inter-vehicle distance, and the driver feels uneasy. It also has the effect of not giving.

According to the third aspect of the present invention, when the target inter-vehicle distance of the inter-vehicle feedback control is changed by the switch by a predetermined distance, the relative speed between the own vehicle and the preceding vehicle is first increased, and then the relative speed is increased. Since the vehicle speed is controlled so as to be smaller, it is possible to surely change the inter-vehicle distance as desired, and it is possible to shorten the time required for the change.

In particular, according to the fourth aspect of the invention, since the initial relative speed at the time of changing the target inter-vehicle distance is set to a larger value as the distance to be changed is longer, the time required for the change is further shortened. be able to.

Further, according to the fifth aspect of the invention, when the target vehicle speed of the vehicle speed type feedback control is changed by the switch, the acceleration / deceleration when the vehicle speed changes in accordance with the change is changed according to the road environment. Therefore, it is possible to always improve the traveling stability regardless of the road environment.

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing an overall configuration of a vehicle speed control device for an automobile for implementing a vehicle speed control method according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a main routine of vehicle speed control.

FIG. 3 is a flowchart showing an automatic cruise operation routine.

FIG. 4 is a flowchart showing a routine for changing a target inter-vehicle distance.

FIG. 5 is a partial view of a flowchart showing a vehicle speed type feedback control routine.

FIG. 6 is a partial view of the flowchart.

FIG. 7 is a diagram showing a match used for setting a target inter-vehicle distance.

FIG. 8 is a diagram showing a match used for setting a predetermined value for vehicle speed control.

FIG. 9 is a diagram for explaining an aspect of inter-vehicle feedback control.

[Explanation of symbols]

 4 control unit 7 radar device 12 vehicle speed sensor 21 approach switch (ON-OFF changeover switch) 22 separation switch (ON-OFF changeover switch) 23 acceleration switch 24 deceleration switch

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoru Ando No. 3 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Co., Ltd. (72) Inventor Kazunori Okuda No. 3 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Corporation (72) Inventor Chiji Izumi, 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Co., Ltd. (72) Inventor, Kenji Shimizu 3--1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture (72) Invention Ms. Yoshiaki Sugamoto 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Motor Corporation

Claims (5)

[Claims] 1. A vehicle speed control method for an automobile that performs an inter-vehicle feedback control for maintaining a constant inter-vehicle distance between at least one vehicle and a preceding vehicle, the method being an ON-OFF switch for changing a target inter-vehicle distance of the inter-vehicle feedback control. Provide a switch and turn it on
When the vehicle is switched to the position, the vehicle speed is controlled so that the relative speed between the own vehicle and the preceding vehicle becomes a predetermined value, and the vehicle-to-vehicle feedback control is performed with the vehicle-to-vehicle distance when the switch is switched to the OFF position from this state as the target vehicle-to-vehicle distance. And a vehicle speed control method for an automobile. 2. The predetermined value is set to a larger value as the inter-vehicle distance between the own vehicle and the preceding vehicle before the change is longer.
The vehicle speed control method for the described vehicle. 3. A vehicle speed control method for an automobile, which performs inter-vehicle feedback control for keeping at least the inter-vehicle distance between the own vehicle and the preceding vehicle constant, and a switch for changing a target inter-vehicle distance of the inter-vehicle feedback control by a predetermined distance. When the target inter-vehicle distance is changed by a predetermined distance by the switch, the vehicle speed is controlled so that the relative speed between the own vehicle and the preceding vehicle is first increased and then the relative speed is decreased. Control method. 4. The vehicle speed control method for an automobile according to claim 3, wherein the initial relative speed at the time of changing the target inter-vehicle distance is set to a larger value as the changing distance is longer. 5. A vehicle speed control method for a vehicle for performing a vehicle speed feedback control for keeping a vehicle speed at least constant, wherein a switch for changing a target vehicle speed of the vehicle speed feedback control is provided, and the target vehicle speed is changed by the switch. A vehicle speed control method, characterized in that the acceleration / deceleration when the vehicle speed changes is changed according to the road environment.