GB2157026A

GB2157026A - Cruise control unit for vehicles

Info

Publication number: GB2157026A
Application number: GB08503230A
Authority: GB
Inventors: Tomoharu Genka
Original assignee: Diesel Kiki Co Ltd
Current assignee: Bosch Corp
Priority date: 1980-01-22
Filing date: 1985-02-08
Publication date: 1985-10-16
Also published as: GB2157026B; GB8503230D0

Abstract

In a cruise control unit in which a stored desired speeds is compared with the actual speed measured at 4 to control an engine 12 there is also provided a data generator (6) for generating a provisional preset data representative of a provisional preset car speed changing with the passage of time from an actual car speed to a predetermined preset car speed for use while the cruising speed control is being restored after disconnection e.g. by clutch or brake and a circuit for supplying the provisional preset data to a control loop instead of the predetermined preset car speed when a restoring operation is commanded, whereby the transition to cruise control can be carried out smoothly without overshooting and undershooting the preset car speed. <IMAGE>

Description

SPECIFICATION Cruise control unit for vehicles The present invention relates to a cruise control unit for vehicles, particularly to a cruise control unit for vehicles by which the speed control of a vehicle, e.g. a car, can be smoothly carried out when a resume function of an automatic cruising unit returns the car speed to a target or preset car speed.

DESCRIPTION OF THE PRIOR ART Vehicle cruise control units capable of controlling the speed of a car to maintain it at a desired or preset level are widely used.

The cruise control unit according to the prior art is constructed in such a manner that the actual car speed is compared with a preset car speed and a car speed regulating member is regulated so as to reduce the difference between the actual car speed and the preset car speed to zero. In addition, in the control unit according to the prior art, the preset car speed is set by operating a set switch when the actual car speed has reached the predetermined or desired car speed so as to store this car speed in a memory and thereafter the car speed control is performed so as to make the actual car speed coincide with the preset car speed. No particular problems arise in this case insofar as the control is started from the condition of zero difference between the actual car speed and the preset car speed.

However, when the cruise control is temporarily released and some time later the cruise control is to be resumed again by a resume function, the difference is not normally zero. For this reason, when the actual car speed is below the preset car speed, the car speed control tends to overshoot. On the other hand, when the actual car speed is above the preset car speed, the control tends to undershoot, making it impossible to continue smooth car speed control. The statement "the cruise control is temporarily released" made above means the condition where cruise control is discontinued when the brake or clutch pedal is operated during cruising speed running. The term "resume function" used above means an operation by which the car speed is again made subject to cruise control.

In order to overcome the above problem, an apparatus has been proposed which comprises (1) a comparator for producing a speed difference signal when a difference arises between a signal representing the actual car speed and another signal representing the desired preset car speed and (2) an actuator responsive to the speed difference signal for controlling the throttle valve opening so as to increase or decrease the actual car speed to reduce the speed difference to zero, whereby the speed difference signal is fed back to the input of the comparator through a delay circuit of the resistor-capacitor coupling type. (See, for instance, U.S.P. No. 4,202,424).

In the proposed apparatus, however, since the output from the comparator is fed back to the actual car speed signal side through the delay circuit, e.g. an integration circuit consisting of resistor(s) and capacitor(s), the amount of the feedback is small just after the resume operation begins if the difference between the actual and preset car speeds is relatively large, and becomes larger with the passage of time. Nevertheless, the feedback characteristic is constant. Accordingly, there have been problems that the acceleration and deceleration become large just after the start of the resume operation, so that both driving safety and riding comfort are impaired.

It is, therefore, an object of the present invention to provide a cruise control unit for a vehicle powered by an internal combustion engine which, after the cruise control has been temporarily released, enables the car speed to be returned to the originally preset car speed, with smooth acceleration or deceleration, whereby the car speed can be smoothly returned to the preset car speed without overshooting or undershooting.

The vehicle cruise control unit according to the present invention has means for producing a car speed signal indicative of the actual car speed, means for storing first data representative of a preset car speed in response to both a signal from a switch unit and said car speed signal, comparing means responsive to said car speed signal and said first data for producing a second data indicative of the difference between said actual car speed and said preset car speed, means for controlling a car speed regulating member so as to reduce the difference to zero in response to said second data, releasing means for temporarily releasing the cruising speed control, and restoring means for suspending said temporary release of the cruising speed control and restoring said cruising speed control, and is characterized in that the unit comprises means for producing a third data representative of a provisional preset car speed which changes with time from the actual car speed to said preset car speed while said cruising speed control is being restored and means for supplying said third data to said comparing means instead of said first data in response to the operation of said restoring means.

In the cruising control unit according to the present invention, when the actual car speed and the preset car speed have come to differ because of the temporary release of the cruising speed control and the actual car speed is then to be made coincident with the preset car speed again, a provisional car speed is first set and the actual car speed is progressively brought closer to the final preset car speed by use of the provisional preset car speed.

As a result, when the cruising speed control is resumed by the operation of a resume switch, the transition to cruise control can be carried out smoothly from the very beginning and without overshooting and undershooting the preset car speed. Therefore, speed control can be carried out smoothly without causing any discomfort to the passengers.

The present invention will be better understood and the other objects and advantages thereof will be more apparent from the following detailed description of preferred embodiments with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an overall block diagram of one embodiment of the cruise control unit according to the present invention; Figure 2 is a block diagram of another embodiment of the cruise control unit according to the present invention; Figure 3 is a control program flow chart to be stored in the memory of the microprocessor shown in Figure 2; Figures 4A through 4C are deetailed program flow charts of important portions of the program shown in Figure 3; and Figures 5 and 6 are graphs for explaining the operation of the cruise control unit shown in Figure 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to Figure 1 showing a block diagram of one embodiment according to the present invention, the vehicle cruise control unit 1 according to the present invention comprises a switch unit 2 having at least a set switch 2a for setting a preset car speed, a release switch 2b for temporarily releasing the cruising speed control and a resume switch 2c for restoring cruising speed control after a temporary release thereof. It also comprises a condition detector 3 for detecting the state of each operating switch of the switch unit 2.

In the cruise control unit 1, when the detector 3 detects that a preset car speed has been commanded, data indicative of the actual car speed at that time detected by a speed detector 4 is stored in a memory 5. On the other hand, when the detector 3 detects that the resume switch 2c has been operated to issue a command for restoring cruising speed control, data indicative of a provisional preset car speed is output from a data generator 6 for generating data representing a provisional preset speed which varies with time from the actual car speed at that time to the present car speed stored in the memory 5.A data selector 7 is provided for selecting either the preset car speed data or the provisional preset car speed data in accordance with the result of detection by a coincidence detector 10 for detecting if the preset car speed and the provisional preset car speed coincide with each other as well as with the result of the detection by the condition detector 3. The data selected by the data selector 7 is compared in a comparator 8 with the data indicative of the actual car speed detected by the speed detector 4, and an actuator 9 for regulating the car speed is driven in accordance with the result of the comparison.

A more detailed description of another embodiment of the present invention will now be made with reference to the drawings.

Figure 2 is a block diagram of a second embodiment of the vehicle cruise control unit according to the present invention. The cruise control unit 11 is designed to control the speed of an internal combustion engine 12 so as to maintain the cruising speed of the car at a desired or preset car speed.

The unit 11 comprises a speed detector 13 for producing a car speed signal S1 indicative of the instantaneous speed of the car (not shown) driven by the internal combustion engine 12, and a switch unit 14.

The switch unit 14 comprises a main switch 15, a set switch 16, a resume switch 17 and a release switch 18, and is provided between a battery 21 and a microprocessor 22. The release switch 18 consists of a brake switch 19 and a clutch switch 20 connected in series.

The microprocessor 22, which receives power from the battery 21, operates in response to a signal from the switch unit 14 and produces a control signal S2 in accordance with a control program stored in advance in a read-only memory (ROM) 26 of the microprocessor 22. The control signal S2 thus produced is amplified by an amplifier 23 and is then applied to an actuator 24 which is coupled to the internal combustion engine 12 and which also regulates the engine speed.

A car speed regulating member 27, e.g. a throttle lever, which is coupled to the actuator 24 is operated in accordance with the signal S2 from the amplifier 23 and the car speed is controlled. The control program stored in ROM 26 of the microprocessor 22 is arranged to perform a control operation like that described regarding the unit shown in Figure 1. Figure 3 is a flow chart of the control program.

Referring to Figure 3, when the program is started, a decision is made in step 31 as to whether the cruise control unit is operating normally or not. If the decision is YES, the operation now moves to step 32 where the car speed data is read from the car speed signal S,. Then, in step 33, a decision is made as to whether or not the car speed data is in the normal range and if the decision is YES, the operation moves to step 34 and step 35, where decisions are made as to whether a complete release of cruise control should be made (step 34) or a provisional release of the same should be made (step 35), on the basis of the signal from the switch unit 14. If the decision in either step 31 or step 33 is NO, or if the decision in step 34 is YES, the operation moves to step 36, where cruise control is completely released. A cruise lamp 25 (Figure 2) is then turned OFF in step 37. If the decision in step 35 is YES, the operation moves to step 38, where cruise control is provisionally released whereafter the cruise lamp 25 is turned OFF and the operation returns to the first step 31.

On the other hand, if the decision is NO in step 35, the operation moves to step 39 where calculations for carrying out cruise control are performed and then the operation moves to step 40, where a PI control operation is performed in accordance with the result of the calculations. Then the operation moves to step 41, where the control signal S2 is output. After this operation, the cruise lamp 25 is turned ON in step 42 and the operation returns to step 31.

Figures 4A through 4C show program steps 34, 35 and 39 in detail.

In operation, as shown in Figure 4A, the ON/OFF condition of the main switch 15 is detected in the step 51. If it is OFF (NO decision), cruise control is completely released. When the result of step 51 is YES, the ON/OFF condition of the release switch 18 is detected in step 52 and if OFF, provisional release is carried out. However, if the decision in step 52 is YES, the operation moves to step 53, where another decision is made regarding the ON/ OFF condition of the set switch 16. If the set switch 16 is ON, flag F1 is set to "1 in step 54 and the operation moves to step 37. In step 53, if the set switch 16 is OFF, the operation moves to step 55, where a decision is made as to whether flag F, is set to "1" or not.If the decision in step 55 is YES, i.e. the set switch 16 is turned from ON to OFF and the operation moves to step 56, where the flag F1 indicating that the set switch 16 is now ON, a flag F2 indicative of the operating condition of the brake or the clutch and a flat F2 which is set to "1 when the resume switch 17 is pushed during the provisional release state or when the accelerator pedal is depressed during cruise control, are reset to "0".

Then, the operation moves to step 57, where the preset car speed T1 and the provisional preset car speed T2 are both set at the actual car speed value V at that time and the operation moves to step 58, where a flag F4 indicating that a preset car speed has been set is set to "1.

After these operations, the operation moves to step 40, where control is carried out to make the car speed coincide with the preset car speed just set, whereby cruising speed control is realized. In this cruising speed control condition, the decision in step 55 in the subsequent program cycle becomes NO and the operation now moves to step 59, where a decision is made as to whether the flag F4 should be set to "1". Since the flag F4 should be set to "1" in this case, the operation moves to step 60 (Figure 4C), where another decision is made as to whether the flag F2 is set to "1".

If the car is running under the cruising control state, both the flags F2 and F2 have been set to "0, so that the decisions in step 60 and the following step 61 both become NO and the operation moves to step 62, where a decision is made as to whether the car has been accelerated by operation of the accelerator pedal. If the decision is NO, the operation moves to step 40.

That is, when the set switch 16 is turned from ON to OFF, a predetermined car speed is set and cruising speed control is carried out. It is to be noted that if the decision in step 59 is NO, cruise control is completely released.

An explanation is now made of the control where provisional release is carried out during cruising speed control condition.

When the release switch 18 is turned OFF, the decision in step 52 becomes NO, and the operation moves to step 63, where the flag F2 is set to "1" and the control is provisionally released. Accordingly, in this case, even if the release switch 18 should be turned ON in the subsequent program cycle, the decision in step 60 becomes YES and the operation moves to step 64, where the actual car speed V is compared with the preset car speed T,.

If T1 > V is found in this case, a flag RF is set to "0", while if T1' V, the flag RF is set to "1" (in steps 65 and 66). Then, in step 67, a decision is made as to whether the resume switch 17 is ON. If the decision in step 67 is NO, i.e. the switch 17 is OFF, the operation moves to step 68, where a decision is made as to whether the flag F3 is set at "1".

If the decision in step 68 is NO, the operation moves to step 69. However, when the resume switch 17 is ON, the flag F2 is set to "1" in step 70 and the operation now moves to step 69.

Accordingly, the decision in step 68 becomes YES only when the resume switch 17 has changed from ON to OFF, and the operation then moves to step 71.

In step 69, a decision regarding the flag RF is made. Namely, when T, > V is found, the provisional preset car speed T2 is changed to V + X, and the content of a counter A is set to "0", i.e. is reset, in step 72. On the other hand, when T, > V is found, the provisional preset car speed T2 is changed to V - Y, and the counter B is reset to "0" in step 73. In this manner, preparation is made for the turning OFF of the resume switch 17.

As described in the foregoing, when the actual car speed V differs from the preset speed T1, the provisional preset car speed T2 begins from that set when the resume operation was started and is made to gradually approach the preset car speed T1 by successively addition thereto or subtracting therefrom predetermined very small increments of car speed every time the counters A and B reach predetermined values A, and B,, respectively.

Whether the increments are added or subtracted depends on the relationship between the preset car speed and the actual car speed V at that time.

In this embodiment of the invention, the very small speed increments are set as follows. When T1 > V is found, X 1 is given as an initial value and X2 is added thereto every time the counter A reaches A1. On the other hand, when the condition T, ' V is found, Y1 is given as an initial value and Y2 is added thereto every time the counter B reaches B1.

Now, when the resume switch 17 is switched from ON to OFF, a decision regarding the flag condition RF is made in step 71. If the flag RF is found to be set to "0", the operation moves to step 74, where another decision is made as to whether the counter A has reached A,. If A > A, is found, the operation moves to step 75, where 1 is added to the content of the counter A. After this operation, a comparison of the provisional preset speed T2 with the preset speed T, is carried out in step 76. If the result of the comparison is T, > T2, the operation now moves to step 40.

In the manner as described, when the count of the counter A reaches A1, the counter A is reset (set to "0") and the provisional preset speed is increased by a predetermined increment X2 in step 77. In this manner, the provisional preset speed T2 is increased by the increment X2 and when the condition T1 ' T2 is established, the operation moves to step 78, where both the flags F2 and F3 are reset to "0. The operation then moves to step 40 after the preset speed T1 has been set to the provisional speed T2. From this time point, the control is returned to the normal cruising speed control condition.

On the other hand, if the result of the decision in step 71 is YES, the operation moves to step 79, where a decision is made as to whether the counter B has reached B1. If the result of the decision is B < B1, the content of the counter B is increased by 1 in step 80 and the operation moves to step 81, where a comparison of the provisional preset speed T2 with the preset speed T1 is carried out. If the result of the comparison is T1 = T2, the operation moves to step 40.

In the manner as described, when the count of the counter B reaches B1, the counter B is reset to "0" and the provisional preset speed is reduced by the predetermined value Y2 in step 82. When, after repeated reduction of the provisional preset speed T2 by increments of Y2, the condition T1 > T2 is found, the step 78 is executed and the operation returns to the normal cruising speed control.

It is to be noted that when the accelerator pedal is depressed, the decision in step 62 becomes YES and in the subsequent step 63, the flag F3 is set to "1", while the counter B is reset, with the result that the provisional preset speed T2 is set at V - K1 (K1 indicates a constant). After this operation, in order to successively make the provisional preset speed T2 approach the final preset speed T1, the same operation as that in the case where the decision is YES in step 71 is executed.

Description will now be made with reference to Figure 5 of the case where the cruising speed control is temporarily released by the operation of the brake during cruising speed control and cruising speed control is then resumed by the operation of the resume switch 17.

When the brake pedal is depressed at the time point t = t1, the cruising speed control is temporarily released and the actual car speed V indicated by the solid line falls below the preset car speed T1 indicated by the dotted line. Then, when the resume switch 17 is switched from ON to OFF at time t = t2, the provisional preset car speed T2, (indicated by the chain line) is set. The provisional preset car speed T2 increases stepwise with time until it reaches the final preset car speed T1. Accordingly, after the time point t2, the actual car speed V increases gradually as if pursuing the provisional preset car speed, until the required final preset speed T1 is reached, thus effectively suppressing the overshoot phenomena which ofter occurs in similar control units according to the prior art.

Figure 6 shows another example of the operation where the resume switch 17 is switched from ON to OFF when the actual car speed V is above the preset car speed T1. In this case, after the cruise control has been temporarily released by the depression of the accelerator pedal at the time point t = t3, the car accelerates from the time t = t4. When the actual car speed V indicated by the solid line rises above the preset car speed T1 indicated by the dotted line, the switching of the resume switch 17 from ON to OFF at the time t = t5 permits the preset car speed T2 (indicated by the chain line) to be set. In this case, the provisional preset car speed T2 decreases stepwise with time, until it reaches to the final preset car speed T1.Accordingly, after the time point t5, the actual car speed V decreases gradually in accordance with the provisional preset speed, thus preventing undershooting and enabling an extremely smooth return to the original preset speed.

When the car has accelerated because of depression of the accelerator pedal without release of cruise control, a similar operation to that of setting the provisional preset speed as shown in Figure 6 is carried out. In this case, however, no particular operation of the resume switch 17 is required.

Moreover, optimum control of the acceleration and deceleration of the car during the resume operation can be performed by setting the variables X1, X2, Y1, and Y2 at desired values, so that a smooth sequence of operations can be realized during the transition from the provisionally released condition to the resume operation. In addition, the variables X1, X2, Y1 and Y2 may be set in accordance with the difference between the instantaneous car speed, i.e. actual car speed, and the preset car speed, with the result that more suitable control becomes possible.

Claims

1. A cruise control unit for vehicles having means for producing a first signal relating to the actual vehicle speed, means for storing a first data indicative of a desired preset vehicle speed, a first means responsive to said first signal and said first data for producing a second data indicative of the difference between said actual vehicle speed and said preset vehicle speed, means for controlling a vehicle speed regulating member so as to make the difference become zero in response to said second data, a releasing means for temporarily releasing the cruising speed control and a restoring means for suspending the temporary release of the cruising speed control to return the control to the cruising speed control, said unit comprising:: a data producing means for producing a third data representing a provisional preset vehicle speed which changes with the passage of time from the actual vehicle speed at that time to said preset vehicle speed in response to the operation of said restoring means; and a changing means for supplying said third data instead of said first data to said first means in response to the operation of said restoring means.

2. A cruise control unit as claimed in Claim 1 wherein said changing means has a selecting means for selectively outputting either said first or third data, a second means responsive to said first and third data for detecting whether or not said provisional preset vehicle speed is coincident with said preset vehicle speed and a controlling means for controlling said selecting means in such a way that said third data is output instead of said first data in response to the restoring of the cruise speed control by means of the operation of said restoring means and when thereafter said provisional preset vehicle speed is detected by said second means to be coincident with said preset vehicle speed, said first data is supplied to said first means again instead of said third data.

3. A cruise control unit as claimed in Claim 1 wherein said restoring means comprises at least a resume switch.

4. A cruise control unit as claimed in Claim 1 wherein said data producing means has a discriminating means responsive to said first signal and said first data for discriminating the magnitude of the difference between the actual vehicle speed and the preset vehicle speed when the cruise speed control is temporarily released by means of said releasing means, means for detecting the end of the temporary release of the cruise speed control by said restoring means, and a data generating means for obtaining said third data by sequentially adding or subtracting a predetermined value to or from the actual vehicle speed at that time in accordance with the result of the discimination of saqid discriminating means when the end of the temporary release of the cruising speed control is detected.

5. A cruise control unit as claimed in claim 4 wherein said data generating means has a third means for producing said third data by sequentially adding the predetermined value to the actual vehicle speed at that time when the temporary release of the cruising speed control has ended and in the case where the result of the discimination by said discriminating means indicates that the actual vehicle speed is more than the preset vehicle speed, and a fourth means for producing said third data by sequentially subtracting the predetermined value from the actual vehicle speed at that time when the temporary release of the cruising speed control has ended and in the case where the result of the discrimination by said discriminating means indicates that the actual vehicle speed is less than the preset vehicle speed.

6. A cruise control unit as claimed in Claim 4 wherein said third means has a first storing means for storing the result of subtracting a first initial value from the actual vehicle speed at that time in response to the temporary release of the cruising speed control and means for sequentially subtracting a first value from the result stored in said first storing means till the third data is equal to the first data.

7. A cruise control unit as claimed in Claims 5 and 6 wherein said fourth means has a second storing means for storing the result of adding a second initial value to the actual vehicle speed at that time in response to the temporary release of the cruising speed control and means for sequentially adding a second value to the result stored in said second storing means till the third data is equal to the first data.

8. A cruise control unit as claimed in Claim 6 wherein said first value is fixed at a predetermined value.

9. A cruise control unit as claimed in Claim 6 wherein said first value is a function of at least one condition parameter indicating the state of the cruising control of the vehicle.

10. A cruise control unit as claimed in Claim 7 wherein said second value is fixed at a predetermined value.

11. A cruise control unit as claimed in Claim 7 wherein said second value is a function of at least one condition parameter indicating the cruise control state of the vehicle.

12. A cruise control unit as claimed in Claim 1 and substantially as hereinbefore described with reference to, and as shown in any one of the embodiments illustrated in the accompanying drawings.