JPH0443822B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a speed control device for a vehicle that operates a speed regulating element of a vehicle to maintain the traveling speed at a set target speed.

(Prior art) This type of vehicle speed control device is
It is generally known from No. 109092 etc. In known devices, an error signal (adjustment signal) representing the error between the actual speed of the vehicle and a set target speed is calculated by analog electrical calculation (or digital electrical calculation), and a predetermined control gain is applied to this error signal. The application is configured to create a correction signal proportional to the error signal and to control a speed regulating element of the vehicle in response to the correction signal.

(Problem to be Solved by the Invention) However, in such a device, when the vehicle goes from a flat road to a steep slope, a slope, or an uphill slope, when the vehicle load increases, the displacement of the speed regulating element tends to be insufficient. , there is a problem that the actual speed deviates from the target speed and the speed increases or decreases.

Therefore, prior to filing the present application, the inventors of the present application discovered that, in relation to the speed error between the actual speed and the target speed of the vehicle and the direction of increase/decrease in the speed error, when the actual speed deviates from the target speed, the actual speed changes to the target speed. By increasing the control gain compared to when the speed is approaching the target speed, the actual speed is prevented from departing from the target speed, and when the speed error is getting smaller, the control gain is reduced to suppress hunting and stabilize the speed. He invented a speed control device for vehicles that provides a comfortable ride and filed an application for the same (Japanese Patent Application No. 1977-97721).

However, although the above device has the advantage of preventing the actual speed from deviating from the target speed, it does not actually detect the vehicle load, so it cannot necessarily determine a control gain that corresponds to the running load. Therefore, when the speed error between the actual speed and the target speed becomes small, the controlled amount remains constant despite the existence of the speed error between the actual speed and the target speed. A problem arises in that the actual speed does not reach the target speed.

Therefore, the present invention has been made in view of the above problem. An object of the present invention is to provide a speed control device for a vehicle that performs control to bring an actual speed closer to a target speed.

(Means for Solving the Problems) In order to achieve the above object, the present invention is characterized by being constructed as shown in FIG. namely, a converting means for converting an actual vehicle speed into a speed signal, a setting means for generating a target signal corresponding to a target vehicle speed, and a difference signal generating a difference signal representing a relative difference between the speed signal and the target signal. signal generating means; determining means for determining whether the actual vehicle speed is closer to the target vehicle speed than at least the difference signal; and applying a predetermined gain to at least the difference signal when the determination result is negative. a first controlled variable calculation means that repeatedly generates a controlled variable signal corresponding to the sum of the first variable signal and a predetermined signal representing a predetermined magnitude; a second controlled variable calculation means that repeatedly generates a new controlled variable signal in response to the sum of a second variable signal to which a predetermined gain has been added and a previously generated controlled variable signal; and adjusting means for changing the adjustment amount of the speed adjustment element of the vehicle accordingly.

In the above configuration, each of the above means is realized by using a digital computer that repeats arithmetic processing according to a preset control program as one embodiment, or by the arithmetic processing thereof, or by combining with appropriate input/output devices. be done.

(Operation) By following the above configuration, the control amount of the speed adjustment element is determined by selectively using two preset calculation means depending on the approach state of the actual speed to the target speed.

When the difference between the first actual speed and the target speed is large, that is, immediately after speed control is started, or immediately after resume operation or acrylic operation, the control amount A is determined according to the following equation. be done.

A = Ai + K ₁ × ΔV ... (1) However, Ai is the control amount of the speed adjustment element on a flat road at the target vehicle speed (hereinafter referred to as the initial value), ΔV
is a speed difference indicating the shortfall between the actual speed and the target speed, and K ₁ is a proportionality constant.

Second, when the actual speed approaches the target speed,
The control amount A is determined according to the following equation.

A=A ₀ + ΔA ……(2) ΔA=K ₂ ×ΔV ……(3) However, A ₀ is the control amount determined by the preceding calculation process, and ΔA is the unit for the speed difference occurring. The amount of correction for each time, ΔV, is the speed difference mentioned above, and K ₂ is the proportionality constant.

In equation (2), the correction amount ΔA has the same sign as the speed difference ΔV. Therefore, as long as the difference signal exists, the control amount signal will be cumulatively added, and the difference signal will gradually decrease. On the other hand, when the speed difference ΔV disappears, that is, when the actual speed matches the target speed, there is no difference between the preceding control amount A ₀ and the new control amount A, and the speed adjustment element is maintained at that position. be done.

(Example) In an example of the present invention, the stability of the actual speed is calculated by adding the acceleration (temporal change) of the actual speed to the calculation processing corresponding to equations (1) and (2) above. can be increased.

The following will be described based on embodiments shown in the accompanying drawings. In this embodiment, a microcomputer is used to realize the central control function as shown in Fig. 2, and the control program is transferred to a third computer.
As shown in the figure.

In FIG. 2, reference numeral 10 indicates an on-vehicle DC power source (hereinafter referred to as a battery), and the battery 10 supplies power to a control circuit package 30 via an engine key switch 11 and an operation panel 20. The control circuit package 30 receives operating signals from the operating panel 20, release signals associated with several operating devices of the vehicle, and other control input signals. An actuating device 50 is connected to the output side of the control circuit package 30, and the actuating device 50 adjusts the opening degree of a throttle valve 60 of a speed-governing element of the vehicle, in this embodiment a prime mover internal combustion engine (not shown). In this way, the engine output torque is increased or decreased, and the vehicle running speed is increased or decreased.

The actuating device 50 is a reversibly rotating DC motor 51.
, an electromagnetic clutch 53 which has a biasing coil 52, is normally disconnected, and is connected when biased by the biasing coil 52;
The throttle valve 60 controls the displacement of the speed reduction mechanism 54 provided between the input plate of the clutch 53 and the DC motor 51 and the output rod 55 provided on the output plate of the clutch 53.
It has a link mechanism 56 that transmits the transmission to. Although not shown, an accelerator pedal operated by the driver is also operatively connected to the link mechanism 56.
The actuating device 50 also includes a potentiometer 57 coupled to the output plate of the clutch 53 to create a resistance value corresponding to the opening of the throttle valve 60.

The operation panel 20 has a main switch 21 inserted and connected between it and the power receiving terminal 30A of the control circuit package 30.
When the main switch 21 is closed by the driver, the circuit elements in the control circuit package 30 are enabled. Main switch 2
1 and the vehicle body ground 10A.Indicator lamp 2
2 is connected, and the lighting of this lamp 22 indicates that this device is ready for operation.

The operation panel 20 also has one end connected to the vehicle body ground 10A and the ground terminal 30B of the control circuit package 30, and the other end connected to the set signal input terminal 30CA, the accelerator signal input terminal 30CB, and the resume signal input terminal 30CC of the control circuit package 30. A set switch 23A, an accelerator switch 23B, and a resume switch 23C are connected to each other.

The control circuit package 30 further has three cancel signal input terminals 30E, 30F, and 30G, and the first cancel input terminal 30E has a stop switch 12 and a stop indicator lamp 13, which are closed in conjunction with the operation of the brake pedal. The potential at the connection point of the series circuit with is applied. The second cancel input terminal 30F is given the potential at the connection point of the series circuit between the parking switch 14 and the parking indicator lamp 15, which are closed in conjunction with the operation of the parking brake, and the third cancel input terminal 30F
A clutch switch 16, which is closed in conjunction with the operation of the clutch pedal, is connected to G.

In order for the control circuit package 30 to know the actual traveling speed of the vehicle, a speed signal generator 17 is provided which responds to the actual traveling speed of the vehicle and generates a pulse train signal whose period becomes shorter as the actual speed increases. The generated pulse train signal is connected to the speed signal input terminal 17B of the control circuit package 30. The speed signal generator 17 includes a permanent magnet 17A that rotates in synchronization with a speedometer cable (not shown) provided to rotate in synchronization with the output shaft of a transmission device (not shown), and a permanent magnet 17A. It is composed of a reed switch 17B whose contacts are swung to open and close.

The control circuit package 30 has an integrated circuit chip 31 (hereinafter referred to as computer) configured as a microcomputer. A computer 31 stores control programs and control constants.
ROM, RAM for temporary data storage, central processing unit (CPU), data lines, timing circuit, free run counter, input/output (I/O) circuit, and A
-D conversion circuit etc. are integrally constructed. Power is supplied to the power supply terminal VCC of the computer 31 by a three-terminal constant voltage circuit 32 and a smoothing capacitor 33 connected between the power receiving terminal 30A and the ground terminal 30B.
done through. The reset circuit 34 is a power receiving terminal
In response to the rise of the voltage applied to VCC, a reset signal is applied to the computer 31 to operate the computer 31 from its initial state. The control program of the computer 31 is executed based on an oscillation signal from an externally connected oscillation circuit 35.

In the control circuit package 30, an accelerator signal input terminal is connected between the set signal input terminal 30CA and the signal input terminal IN1A of the computer 31.
Between IN1B and resume signal input terminal IN1
C, buffers 38A, 38B, and 38C are connected to the set switch 23A, accelerator switch 23B, and volume switch 23, respectively.
The operation signal of C is transmitted to the computer 31.

NOR gate 4 is connected to the second and third cancel signal input terminals 30F and 30G in the package 30.
0 is connected, and an OR gate 41 is connected between the output terminal of the NOR gate 40, the fourth cancel signal input terminal 30E, and the signal input terminal IN3 of the computer 34, and a cancel signal based on the operation of each operation device is connected. is transmitted to the computer 31.

A buffer 42 is connected between the speed signal input terminal 30H in the package 30 and the interrupt input terminal IRQ of the computer 31, and the interrupt program of the computer 31 is activated every time the signal level of the speed pulse train signal changes. .

Analog signal input terminal 301 of package 30
and the analog signal input terminal ANIN of the computer are directly connected, and a voltage signal from the potentiometer 57 indicating the opening degree of the throttle valve 60 is applied to an A-D conversion circuit built in the computer 31. Note that both ends of the potentiometer 57 are connected to the three-terminal constant voltage circuit 32 through terminals 30J and 30K of the package 30.

Adjustment signal output terminal 3 of control circuit package 30
A DC motor 51 of an actuating device 50 is connected between 0L and 30M, and the output terminals 30L, 30
A pair of signal output terminals of M and computer 31
A drive circuit 36 is connected between OUT1 and OUT2.

The drive circuit 36 of the DC motor 51 includes two presettable timer circuits 36A, 36B and a first set of power transistors 44, 4 whose conduction and cut-off are simultaneously controlled by a first front-stage transistor 43.
5 and a second set of power transistors 47 and 48 whose conduction and cut-off are simultaneously controlled by the second front-stage transistor 46.

Presettable timer (hereinafter referred to as timer) circuit 36
A and 36B are presettable down counters whose data is preset by the output signal from the signal output terminal group OUT1 of the computer 31, and which immediately thereafter counts down until the data reaches "0" by a clock pulse of a constant frequency.
A high level output signal is generated until the data becomes "0".

If the first signal output terminal group of the computer 31
Although predetermined data is generated from OUT1 and no data is generated from the second signal output terminal OUT2, the drive circuit 36
is conductive for a time corresponding to the number of data preset in the timer 36A, and at the same time, the first set of power transistors 44 and 45 are conductive, causing the DC motor 51 to move in the direction of the arrow shown by the symbol I (the direction in which the throttle valve 60 is opened). ).

On the other hand, the second signal output terminal group of the computer 31
When data is applied to the timer circuit 36B from OUT2, the second front-stage transistor 46 of the drive circuit 36 becomes conductive for a time corresponding to the data.
As a result, the second set of power transistors 47,
48 becomes conductive, and a current flows in the direction opposite to arrow I through the DC motor 51. In this way, the drive circuit 3
6 is the signal output terminal OUT1 of the computer 31;
The rotation direction of the DC motor 51 can be selected according to the level of the signal generated from OUT2,
Also, the amount of rotation can be controlled.

The energizing coil 52 of the actuating device 50 is connected between the energizing signal output terminals 30N and 30O of the package 30. In the package 30, one energizing signal output terminal 30O is connected to a power receiving terminal 30A, and the other terminal 30N is connected to a drive circuit 37 responsive to a signal output terminal OUT3 of the computer 31.

The drive circuit 37 is composed of a paratransistor, and is connected to a signal output terminal of the computer 31.
Upon receiving a high level signal from OUT3, the energizing coil 52 is energized and the clutch 53 is connected to enable the DC motor 51 to control the opening and closing of the throttle valve 60.

3 to 7 show the implementation of a control program executed by computer 31. FIG.

FIG. 3 shows that the computer 31 resets the reset circuit 3.
4 shows the flow of the main program which starts processing upon receiving a reset signal. When the computer 31 starts processing the main program, it first sets the states of internal registers, temporary memory, output terminals, etc. to preset initial states (step 101). Next, the computer enters the fourth step in step 102.
Enable reception of the timer interrupt program shown in the figure,
At step 103, acceptance of the vehicle speed interrupt program shown in FIG. 5 is permitted.

The timer interrupt program will be explained with reference to FIG. The computer 31 has a built-in timer counter that generates an interrupt signal at regular intervals (for example, about 10 ms). When the computer recognizes this, it saves the register in step 201 and executes the following process. do.

The main role of the timer interrupt program is the operation panel 2.
0 and the operating states of various driving operation devices, and updating a timer counter for time measurement.

In steps 202 to 212, the signal input terminal INIA,
By checking INIB and INIC, the set switch 23A and accelerator switch 23 on the operation panel 20 can be
B. The operation of the resume switch 23C is flagged and the status of each switch is determined in the main routine.

In addition, the timer interrupt program
At step 213, a group of timer counters (T counters) set internally for use in time measurement is incremented. At the end of these processes, in step 214, the registers are restored, the execution of this interrupt program is ended, and the interrupted execution of the main program is resumed.

The vehicle speed interrupt program will be explained with reference to FIG. The computer 31 is activated once in one cycle of the pulse train signal based on the application of the pulse train signal from the speed signal generator 17. The role of the vehicle speed interrupt program is to internally take in sampling data for calculating the traveling speed of the vehicle.

After the computer 31 saves the register in step 301, the computer 31 reads the current data of the built-in free run counter in step 302. This read data is stored as data An.

Difference data DV ₀ between the read data An and the previous read data An _-1 is obtained (step 303), and this is used as instantaneous vehicle speed data. Steps 304, 305, 306,
307, four instantaneous vehicle speed data used for calculation.
Dv ₁ , Dv ₂ , Dv ₃ , Dv ₄ then new vehicle speed data
Dv ₀ , Dv ₁ , Dv ₂ , and Dv ₃ are updated respectively.
In this way, the latest four pieces of vehicle speed data Dv ₁ to Dv ₄ are always secured.

Next, in step 308, the read data An of this interrupt cycle is stored as the previous read data An _-1 , and in step 309, the register is restored, and the vehicle speed interrupt program is ended.

In the main program shown in Figure 3, the steps
104, the computer 31 checks whether there is an abnormality in the internal state. For example, the check item may be to check whether the data indicating the target speed in the temporary memory is "zero". In this case, it is impossible under normal conditions that the target speed is set even though the set switch 23 is not operated immediately after the computer 31 starts. Therefore, when the computer 31 recognizes that the target vehicle speed is other than "zero" in step 104, it stops the process in step 105.
Proceed to. At the stop step 105, the computer 31
stops all program processing and does not perform any operations.

If no abnormality is recognized, the computer 31 waits for a preset time in step 106. This time is set to correspond to the time during which four pieces of vehicle speed data are obtained by the vehicle speed interrupt program (FIG. 5) during a certain low speed run. Usually several hundred ms is enough. After this, the computer 31 performs step 107.
From step 112, step 116, or step 119, the program starts executing a circular program that returns to step 107 again.

In step 107, the computer 31 calculates actual vehicle speed data (Vs) based on the total value of the four vehicle speed data Dv ₁ to Dv ₄ . in this case,
Since the pulse train signal generated by the speed signal generator 17 is generated every time the vehicle travels a predetermined distance, the actual speed Vs can be obtained by dividing this previously known distance by the total value of the hourly vehicle speed data. It will be done.

The processing of the computer 31 differs greatly depending on whether constant speed driving control is in progress or not.
Whether or not it is under control is determined in step 108 by whether the control flag Fc is set to "1" or reset to "0".

If it is not under control, steps 109 and subsequent steps are processed in the route indicated by symbol A. In step 109, it is determined whether the set switch 23A has been operated or not based on the switch flag Fs described above. if,
As a result of determining whether or not the resume switch 23C has been operated in step 120 using the switch flag F _R , if there is no resume operation, the computer repeats the processing from step 107 again.

When the set switch 23 is operated and the switch flag Fs is set to "1", the computer 31 stores the actual speed Vs at that point in the target speed area of the temporary memory as the target speed _V0 in step 110. . Furthermore, in step 111, a high level signal is sent from the signal output terminal OUT3 in order to connect the clutch 53 of the actuating device 50. Further, in step 112, the control flag Fc is set to "1" indicating that the control is in progress, and further, in step 112B, the control flag Fi is set to "1" indicating that the initial opening is to be opened, and the process returns to step 107.

Once under control, the computer 31 checks in step 113 whether or not there is a cancel operation. If there is no cancel operation, the computer performs processing along route B from step 114 onwards. In step 114, the timing of processing to be performed at preset fixed time intervals is determined from the contents of the T counter. This will cause the step
115 and 116 are always executed at regular intervals.

During control, the computer 31
In step 115, the value of the adjustment signal (adjustment amount) to be applied to the actuator 50 in order to obtain the opening degree of the throttle valve 60 necessary to maintain the actual speed at the target speed is calculated. Step 116 based on the calculated adjustment amount
Then, output signals are given to the drive circuit 36 from the signal output terminal groups OUT1 and OUT2.

If a cancel operation is performed during control, the computer 31 follows route C and executes the processing from step 117 onwards. In step 117, actuator 5
Data corresponding to the time required to move the DC motor 51, which is in the zero position, to the initial position on the deceleration side is applied to the timer circuit 36B from the output terminal group OUT2.
This time is set to approximately a few seconds. Further, in step 118, the computer applies a low level signal to the signal output terminal OUT3 to disconnect the clutch 53. Further, in step 119, the control flag Fc is reset to "0", and the process returns to step 107.

When the resume operation is performed after this, the resume judgment in steps 107→109→120 becomes YES, and the clutch 53 of the actuating device 50 is activated in step 111.
A high level signal is sent from the signal output terminal OUT3 in order to connect the two. Furthermore, in step 112, the control flag Fc is set to "1" indicating that the control is in progress.
Return to 107. This is equivalent to setting the target vehicle speed without rewriting it, and therefore means that the vehicle will continue to drive at the previously set target vehicle speed.

By executing the control program having the above configuration, when the set switch 23 is operated, constant speed running is started from route A onwards at step 110 and below,
During the control, an appropriate control signal is applied to the actuating device 50 to maintain the actual speed of the vehicle at the target speed, and the control is canceled when the cancel switch 24 or a driving device such as a brake or clutch is operated.

Adjustment of the throttle valve 60 in constant speed running control is determined based on the calculation in step 115,
This step 115, in accordance with the spirit of the present invention, employs the control procedure illustrated in detail in FIG.

The adjustment amount calculation step (115) first begins with the step
The process begins in step 401 by calculating the error ΔV between the actual speed Vs and the target speed _V0 .

In step 402, the acceleration V of the actual speed is calculated, but the actual speed Vs and the previously calculated actual speed are
It is determined by the difference in Vs′.

The target throttle opening degree is calculated based on this error vehicle speed ΔV and acceleration V. There are three calculation methods.

During the operation of the accelerator switch, it is determined in step 403 that the accelerator switch flag F _A is "1", and the target throttle opening degree A is calculated by the following equation.

A=Ai+A _A ...(4) However, Ai is the above-mentioned initial opening degree, and A _A is the opening amount for accelerating the vehicle.

After operating the accelerator switch, operating the set switch, or operating the resume switch, the flag Fi
is "1", so when flag Fi is checked in step 404, the route is always to set "0" to flag Fi in step 407, and in step 409, the target throttle opening A is calculated by the following equation.

A=Ai+K ₁ × ΔV ...(1) Next, when entering step 115 again, the flag Fi is "0", so in step 405, the error vehicle speed ΔV is first calculated.
It is determined that the width Vu is greater than or equal to a predetermined width Vu, for example, greater than or equal to 4 km/h, and the calculation of equation (1) is performed.

If the acceleration is within Vu, step 406
However, it is determined that the width is greater than a predetermined width, for example, 0.2 Km/h/s or greater, and the calculation of equation (1) is performed.

Under other conditions, i.e., when the error vehicle speed and acceleration become approximately stable within the determined range,
In the next step 410 and step 411, the next target throttle opening degree is calculated.

ΔA=K ₂ ×ΔV−K ₃ ×V・……(3) A=ΔA+A0.……(2) However, in (3′), V represents the acceleration of the actual speed, and K ₃ is the proportionality constant. .

FIG. 7 shows in detail the adjustment output step 116 for sending the calculated adjustment amount to the drive circuit 36, following the adjustment amount calculation step 115 shown in FIG.

At step 501 in FIG.
1 is data “0” from signal output terminals OUT1, 2
is sent to timer circuits 36A and 36B. This allows these timer circuits to temporarily
3, 46, the output is converted to a low level and the two power transistor stages 45, 46, 47, 48 are output.
are all cut off, and the energizing current of the DC motor 51 disappears instantaneously. This is to ensure that a short-circuit current across both power transistor stages is prevented when one power transistor stage that has been cut off is later switched on to conduction and the other power transistor stage that was on is switched to cut off. .

In step 502, the computer receives the analog signal indicating the actual throttle valve opening from the potentiometer 57 from the analog signal input terminal ANIN, and uses the built-in A-D conversion circuit to obtain digital data As indicating the throttle valve opening. And remember this.

In step 503, the deviation DT between the target throttle valve opening A and the actual opening data As is calculated. In the next steps 504 and 505, it is determined whether or not the deviation DT is within a predetermined range. If the actual opening degree As is close to the target opening degree A and is within the range of the deviation width ±DTw arbitrarily determined as a dead zone, no data is given (steps 508 and 509) and the process in step 501 is performed. The DC motor 51 is stopped in accordance with the output, so the throttle valve opening degree is maintained.

In step 506, data S indicating the drive time to be given to the timer circuits 36A and 36B of the drive circuit 36 is calculated based on the following equation based on the magnitude of the deviation DT.

S=f(|DT|)+S _p ...(5) According to this formula, the driving time S is proportional to the deviation DT,
It is shown to have a constant offset _Sp .

In step 507, it is determined whether the deviation DT has a positive sign or a negative sign. If the deviation DT has a positive sign, the process proceeds to step 508, and if it has a negative sign, the process proceeds to step 509.

Step 508 if the deviation DT has a positive sign.
sends the drive data S calculated by equation (5) to the timer 36A from the first signal output terminal OUT1. Due to the operation of the timer 36A, the power transistor 44,
45 conducts, causing the DC motor 51 to rotate in the normal direction, thereby increasing the throttle valve opening and accelerating the vehicle. On the other hand, when the deviation DT has a negative sign, the drive data S is sent to the timer 36B from the second signal output terminal OUT2, and the throttle valve opening degree is decreased by reverse rotation of the DC motor 51.

In this way, the adjustment output is applied to the actuating device 50, and the DC motor 51 rotates forward or reverse at a predetermined time ratio to obtain the calculated adjustment target throttle valve opening, thereby opening the throttle valve. The degree changes.

Although one embodiment of the present invention has been described above, the present invention is not limited to the description of this embodiment. This book describes how to change the procedure when configuring a control program, how to create data such as calculations, the form of the signal that controls the speed adjustment element and how to give it, the selection of the actuating device, and the selection of the speed adjustment element to be applied. It is possible within the scope of the gist of the invention.

(Effects of the Invention) As described above, in the present invention, when the actual vehicle speed approaches the target vehicle speed, as long as the difference signal exists, it is cumulatively added to the control signal, and the difference signal is gradually added to the control signal. This has the excellent effect of bringing the actual vehicle speed closer to the target vehicle speed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing features of the configuration of the present invention, FIG. 2 is an overall configuration diagram of an embodiment, and FIGS. 3 to 7 are flowcharts showing a control program for the microcomputer 31 of the apparatus shown in FIG. 1. Chart,
FIG. 8 is a control characteristic diagram of the device. 17...Speed signal generator, 20...Operation panel, 2
3...Set switch, 30...Control circuit package, 31...Microcomputer, 36...
Drive circuit, 50...actuating device, 51...DC motor, 60...throttle valve (speed regulating element).

Claims (1)

[Claims] 1. Conversion means for converting an actual vehicle speed into a speed signal; Setting means for generating a target signal corresponding to a target vehicle speed; and a difference representing a relative difference between the speed signal and the target signal. difference signal generating means for generating a signal; determining means for determining whether or not the actual vehicle speed approaches the target vehicle speed based on at least the difference signal; a first controlled amount calculation means that repeatedly generates a controlled amount signal in response to a sum of a first variable signal to which a predetermined gain is given and a predetermined signal representing a predetermined magnitude; and when the determination result is affirmative; a second controlled variable calculation means that repeatedly generates a new controlled variable signal in response to a sum of a second variable signal obtained by adding a predetermined gain to at least the difference signal and a previously generated controlled variable signal; A speed control device for a vehicle, comprising: an adjustment means for changing an adjustment amount of a speed adjustment element of a vehicle in accordance with the control amount signal. 2. The determining means also determines whether the temporal change in the speed signal is smaller than a preset value, and whether the actual vehicle speed is stably approaching the target vehicle speed. The vehicle speed control device according to claim 1, which determines whether or not the vehicle is in use. 3. According to claim 1 or 2, the first controlled variable calculating means and the second controlled variable calculating means reflect a temporal change in the speed signal in the controlled variable signal. The vehicle speed control device described above.