JPS60259532A - Automatic speed control device - Google Patents

Abstract

PURPOSE:To enable maintaining of running at a set automobile speed, by a method wherein, when an automobile speed is increased over the set speed irrespective of an engine brake running state, an engine brake effect is increased by shifting down an automatic transmission gear. CONSTITUTION:An engine 10 is provided independently from an accel pedal with an output control device 14, adpated to control the output of an engine, and the control device is controlled by a controller 60 so that an automobile is caused to run at a set speed set by a driver. Said device is provided with a down shift actuator 20 which is capable of forcibly shifting-down an automatic transmission gear 12. When it is detected that the output control device 14 is in a minimum output state during engine brake running and an actual speed is increased by a given value or more over a set speed, a down shift instruction signal is outputted from the controller 60. This causes actuation of the down shift actuator 20 and causes shifting-down of the automatic transmission gear 12.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field The present invention relates to an automatic speed control device for a vehicle.

(b) Prior art automatic speed control devices are devices that allow a vehicle to always run at a constant speed without the driver operating the accelerator pedal (for example, Japanese Patent Application Laid-Open No. 10454/1983).
5 etc.), automatic speed control devices generally include a vehicle speed detection device that detects vehicle speed, an engine output control device that can control engine output independently of the accelerator pedal, and a vehicle speed signal from the vehicle speed detection device as a feedback signal. The engine has a controller that operates an engine output control device so that the vehicle speed is constant. The controller has the function of starting or stopping the operation of the automatic speed control device based on the driver's will, the function of setting the vehicle speed desired by the driver, and the function of automatically stopping the operation of the automatic speed control device according to driving conditions. It also has the function of The automatic speed control device as described above allows the vehicle to continue traveling at a constant speed desired by the driver under normal driving conditions. However, when driving on a road with a large inclination angle, it may become impossible to maintain a constant vehicle speed. For example, when driving uphill, the engine output is insufficient and the vehicle speed decreases. Under such driving conditions, the aforementioned automatic speed control device releases overdrive in the case of a vehicle equipped with an automatic transmission with overdrive to prevent a drop in vehicle speed.
Furthermore, if the vehicle speed decreases significantly, the automatic speed control device is deactivated as control is impossible.

On the other hand, when going down a steep slope, the actual vehicle speed may be higher than the set vehicle speed even in the engine braking state. In such an operating state ρ, conventional automatic speed control devices are configured to leave the speed increasing state as it is. For this reason, even though an automatic speed control device is installed, when going down a slope, the vehicle may have to travel at a speed higher than the set vehicle speed, and the driver is not required to press the brake pedal. Not only is this unfortunate, but there is also the problem that the automatic speed control device is deactivated.

(c) Purpose of the Invention The object of the present invention is to provide an automatic speed control device that allows a vehicle to continue traveling at a set vehicle speed even when traveling downhill.

(d) Structure of the Invention The present invention provides for increasing the re-engine braking effect by downshifting the automatic transmission when the vehicle speed increases more than the set vehicle speed even though the vehicle is in an engine braking state; The above objective is achieved by maintaining running at a set vehicle speed. That is, as shown in FIG. 5, the automatic speed control device according to the present invention includes an engine brake detection means for detecting that the engine output control device is in the minimum output state, and a means for detecting the actual speed of the vehicle by the driver. A speed over detection means detects that the actual vehicle speed is greater than a predetermined value than a set vehicle speed, an engine brake detection means detects that the engine output control device is in the minimum output state, and an over speed detection means detects that the actual vehicle speed is higher than the set vehicle speed by a predetermined value. A town shift command means outputs a downshift command signal when detecting that the vehicle speed is higher than a predetermined value than the set vehicle speed, and an automatic transmission issues a downshift command based on the downshift command signal from the downshift command means. and a downshift actuator that switches the shift line so as to select a gear position with a higher gear ratio than when no signal is issued.

(e) Examples Examples of the present invention will now be described with reference to FIGS. 1 to 5 of the accompanying drawings.

As shown in FIG. 1, an engine 10 and an automatic transmission 12 are connected. The engine 10 is connected to an accelerator pedal via a linkage (not shown), and the output is controlled by this, but in addition to this, an engine output control device 14 is capable of controlling the engine output independently of the accelerator pedal. is provided. The engine output control device 14 is of a type that operates a diaphragm using, for example, a vacuum valve and an air valve operated by an electric signal, thereby controlling the throttle opening. The automatic transmission 12 includes a torque converter 16 and an automatic transmission mechanism section 18. As schematically shown in FIG. 2, the automatic transmission mechanism section 18 includes input work, output shaft 0, first planetary gear set G1, second planetary gear set Gz, front clutch F/C, rear clutch R/C, band brake B,
It has a low and reverse brake L&R/B and a one-way clutch OWC, which allows automatic gear shifting of three forward speeds and one reverse speed. The speed change of the automatic transmission mechanism section 18 is controlled by a hydraulic control device, and the hydraulic control device includes a downshift actuator 20 (described later) capable of forcibly downshifting the automatic transmission mechanism section 18 by switching the shift line. is provided.

The hydraulic control device is shown in FIG. This hydraulic control device includes an oil pump 22, a pressure regulator pulp 24
, manual valve 26, l-2 shift valve 28.2
-3 shift 8 valves 30, pressure modifier valve 32. /<Cue throttle valve 34, throttle backup valve 36, solenoid downshift l<lube 38, second lock no help 40. It has a timing valve 42 and a governor valve 44, which are connected to the torque converter 16. Front clutch F/C, rear clutch R/C, band brake B servo apply chamber S/A and servo release chamber S/R1
and low and reverse brake L&R/B as shown. The downshift actuator 20 described above is composed of a solenoid downshift valve 38 and a solenoid 46 capable of switching the solenoid downshift valve 38.

When the solenoid 46 is off, the solenoid downshift valve 38 does not supply the pressure of the oil passage 50 to the oil passage 48, but when the solenoid 46 is turned on, the solenoid downshift valve 38 switches to supply oil pressure. The line pressure of the oil passage 50 is supplied to the passage 48 . The line pressure supplied to the oil passage 48 acts on the ports of the 1-2 shift valve 28 and the 2-3 shift valve 30 on the side facing the governor pressure. Therefore, the 1-2 shift line and the 2-3 shift line obtained by the 1-2 shift valve 28 and the 2-3 shift/<lub 30, respectively, are much higher than in the normal case (i.e., the vehicle speed will not upshift unless it becomes very high). Conversely, if the solenoid 46 is turned on when the vehicle speed is not very high, a downshift will always occur. The detailed structure and operation of the above-mentioned hydraulic control device are described in, for example, Japanese Patent Laid-Open No. 54-13.
No. 2062.

The operations of the engine output control device 14 and downshift actuator 20 described above are controlled by electrical signals from a controller 60. A vehicle speed signal 63 from a vehicle speed detection device 62 is input to the controller 60. 1. When the driver turns on the automatic speed control device with the intention of using it, The engine output control device 14 is controlled using the vehicle speed signal 63 from the vehicle speed detection device 62 as a feedback signal so that the set vehicle speed set according to the driver's intention is always maintained. The general feedback control of vehicle speed in this normal case is the same as the conventional one. However, the controller 60 has a control function shown in the control flowchart of FIG. 4, and thereby the engine brake detection means 64 shown in FIG.
, overspeed detection means 66, and downshift command means 68. Engine brake detection means 64
The signal 7° output from the controller 6o to the engine output control device 4 is below a predetermined small value (that is, the engine output control device 14 operates to fully close or almost fully close the throttle). It is possible to detect that the engine output control device 14 is in the lowest output state from the fact that a signal is output. The overspeed detection means 66 is
It is possible to detect that the vehicle speed signal 63 input from the vehicle speed detection device 62 is higher than the set vehicle speed by a predetermined value or more. (Downshift) The command means 68 activates the downshift actuator 20 only when the engine brake detection means 64 detects that the engine is in the engine brake state and the overspeed detection means 66 detects that the vehicle speed is higher than the above value. Downshift command signal 7 to operate
2 is output, and in other cases it is commanded to perform normal control. When the downshift command signal 72 is output from the downshift command means 68 to the downshift actuator 20, the solenoid 46 is turned on, and the downshift solenoid valve 3 is activated as described above.
8 is switched. As a result, the shift line obtained by the hydraulic control device becomes higher, so a downshift is performed, and the automatic transmission mechanism section 18 is shifted to a state with a large gear ratio. Therefore, if the engine throttle is fully closed or almost fully closed, but the vehicle speed is higher than the set vehicle speed by a certain value (i.e., when driving on a steep downhill slope), the automatic transmission For example, 4U1818 switches from the third speed state to the second speed state. Therefore, the engine braking effect increases and the vehicle speed decreases, so that the vehicle speed can be maintained at the set vehicle speed. When the vehicle speed decreases to the set vehicle speed, the downshift command signal 72 is no longer output to the downshift actuator 20, so the solenoid 46 is turned off, and the automatic transmission mechanism section 18 is turned off.
Return to speed. As a result, due to the above-described effects, the vehicle can be driven at the set vehicle speed even when going down a steep downhill road.

(f) As described in detail, according to the present invention, the automatic speed control device includes an engine brake detection means for detecting that the engine output control device is in the minimum output state, and an engine brake detection means for detecting that the engine output control device is in the minimum output state; Overspeed detection means detects that the vehicle speed is higher than a set vehicle speed set by the driver by a predetermined value or more, and engine brake detection means detects that the engine output control device is in the lowest output state and detects overspeed. a downshift command means that outputs a downshift command signal when the detection means detects that the actual vehicle speed is higher than the set vehicle speed by a predetermined value; and an automatic downshift command signal based on the downshift command signal from the downshift command means. Since the transmission has a downshift actuator that switches the shift line to select a gear position with a higher gear ratio than when a downshift command signal is not issued, the vehicle speed is If the speed increases, the vehicle speed is downshifted to prevent the vehicle speed from becoming higher than the set vehicle speed, making it possible to always drive at the set vehicle speed.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an automatic speed control device according to the present invention, and FIG. 5 is a diagram showing the relationship between the constituent elements of the present invention. 10---Engine, 12---Automatic transmission, 14.-
・Engine output control device, 16... Torque converter, 18... Automatic transmission mechanism, 20... Downshift actuator, 38... Φ solenoid downshift valve, 46... Solenoid, 60... Controller, 6
2. Fist/vehicle speed detection it, 64... Engine brake detection means, 66... Speed over detection means, 68... Downshift command means. Patent applicant Nissan Motor Co., Ltd. Agent Patent attorney Toshiyuki Miyauchi

Claims (1)

[Scope of Claims] An automatic speed control device that controls engine output using a vehicle speed signal of a vehicle with an automatic transmission as a feedback signal so that the vehicle travels at a set vehicle speed set by a driver, comprising: engine brake detection means for detecting that the vehicle is in a minimum output state; overspeed detection means for detecting that the actual speed of the vehicle is greater than a set vehicle speed set by the driver by a predetermined value; When the means detects that the engine output control device is in the lowest output state and the speed over-detection means detects that the actual vehicle speed is greater than the set vehicle speed by a predetermined value or more, the downshift command signal is output. Based on the shift command means and the downshift command signal from the downshift command means, the automatic transmission switches the shift line so that the automatic transmission selects a gear position with a larger gear ratio than when the downshift command signal is not issued. An automatic speed control device comprising: a downshift actuator;