JP3767258B2 - Automatic engine stop device for AT cars - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an automatic stop device that realizes reduction of exhaust gas, fuel saving, etc. by executing automatic stop of an engine of an AT car at an intersection or the like, and in particular, an automatic engine stop device that can reduce shock at the time of automatic stop. About.
[0002]
[Prior art]
Conventionally, the engine of AT vehicles (automatic vehicles) is stopped by shutting off the fuel supply to the engine by turning off the ignition key switch of the driver in the parking range (P range) or neutral range (N range). ing. At this time, the output torque of the engine rapidly decreases, and at the same time, the engine speed rapidly decreases and becomes zero. Thereafter, the idle air amount control device (ISC) is fully opened so that the intake air can be smoothly introduced at the next engine start, and the relay for supplying the power supply voltage to the engine ECU is turned off.
[0003]
By the way, in recent years, in order to reduce exhaust gas and save fuel, when an AT car stops at an intersection or the like, the engine is automatically stopped under a predetermined stop condition, and then the engine is operated under a predetermined start condition. An automatic stop / start device for restarting is known. Since such an AT vehicle automatically stops and starts in the drive range (D range), the stop frequency is higher than the stop frequency in the P range and the N range. For this reason, the ride comfort of the vehicle at the time of stoppage has become a more important problem for the driver.
[0004]
[Problems to be solved by the invention]
However, since the rotation shaft of the engine is connected to the axle in the D range, the engine torque is transmitted to the axle when the engine is stopped in the D range. That is, a sudden change in engine torque causes a large imbalance in the output torque of each cylinder and makes the rotation speed of the crankshaft unstable. This sudden change is transmitted to the axle through a torque converter and an automatic transmission. This causes fluctuations in the axle torque, which is transmitted to the driver as a shock (front and rear G).
[0005]
Furthermore, when the engine speed naturally decreases after the combustion ends, the engine speed passes through the resonance frequency range of the drive line. At this time, the engine vibrates around its output shaft, and the vibration Vibrates the car body through the engine mount. This vibration appears as vibration in the pitch direction in the horizontally mounted engine shown in FIG. Similarly, in the vertical engine shown in FIG. 9B, it appears as vibration in the roll direction, causing shocks of up and down G and left and right G.
[0006]
For this reason, in the automatic engine stop frequently performed at an intersection or the like, the above-described shock has given the driver discomfort.
[0007]
An object of the present invention is to provide an automatic engine stop device that can effectively reduce a shock at the time of automatic stop in the D range.
[0008]
[Means for Solving the Problems]
In view of the above problems, the automatic engine stop device for an AT vehicle according to claim 1 reduces the engine speed in the D range when a predetermined engine stop condition is satisfied. The change time point is set in the descending slope. Then, the descending gradient of the engine speed before the change time is set to be gentler than the descending gradient of the engine speed after the change time.
[0009]
FIG. 1 shows an outline of the engine speed control mode in comparison with the prior art. In the figure, the solid line indicates the control mode according to the first aspect, and the double-dashed line indicates the control mode corresponding to the prior art.
[0010]
As can be seen from the figure, in the prior art, when the automatic engine stop condition is satisfied, the engine speed naturally decreases with a substantially constant gradient from the start of deceleration until the stop is reached.
[0011]
On the other hand, in the apparatus according to the first aspect, the engine speed is gradually lowered until the engine speed reaches the change point of the descending gradient. For this reason, fluctuations in the output torque of the engine (hereinafter referred to as “engine torque”) can be suppressed to a smaller level than before. For this reason, the front-rear G of the vehicle body due to a sudden change in engine torque can be reduced. In this case, the gradient of decrease in engine speed becomes steep after the time of change, but since the engine speed has decreased to some extent until the time of change, the difference in engine speed from the time of change is less than that of the conventional case. Get smaller. For this reason, the front-rear G of the vehicle body due to a sudden change in engine torque can be suppressed as compared with the conventional case.
[0012]
Specifically, in the apparatus according to the first aspect, the combustion is continued so as to generate the engine torque until the time of change, and the combustion is stopped so as to make the engine torque zero after the time of change.
[0013]
That is, conventionally, when the engine stop condition is satisfied, the combustion is completely stopped, and the engine speed is thereby rapidly decreased. For this reason, the engine torque suddenly changes as described above, and the front and rear G of the vehicle body occur.
[0014]
On the other hand, in the apparatus according to the first aspect, the degree of combustion is gradually reduced until the change point is reached after the engine stop condition is satisfied, and the combustion is completely stopped when the change point is reached. By controlling in this way, the engine speed can be gradually decreased until the change point is reached, and the engine speed can be rapidly changed after the change point. As a result, as described above, the torque fluctuation can be reduced as a whole, and the longitudinal G can be suppressed.
[0015]
As described above, according to the apparatus of the first aspect, the front-rear G generated in the vehicle body as a whole is suppressed by controlling the descending state of the engine speed when the engine is stopped in a stepwise manner. Discomfort can be eliminated.
[0016]
In addition, as a specific configuration of the engine automatic stop device, as described in claim 2, engine speed detection means for detecting the engine speed is provided, and the change point is determined by the engine speed detection means. It can be considered that the detected engine speed is set to be a point in time during which the detected engine speed reaches a predetermined value or less.
[0017]
This configuration takes into account, for example, that the resonance frequency of the drive line exists below the engine idle speed. In other words, when the engine speed decreases, it passes through the resonance frequency range of the drive line, but while passing, the engine vibration is amplified to generate front and rear G, up and down G, or left and right G of the vehicle. Will cause discomfort to the driver. The longer it takes to pass through this resonance frequency range, the greater the driver discomfort.
[0018]
Therefore, in the automatic engine stop device according to claim 2 , when the engine speed detected by the engine speed detecting means reaches a predetermined value, for example, a slightly higher speed than the upper limit of the resonance frequency range in the descending process. In this case, the change time is set and the descending gradient of the engine speed after the change time is made steep to shorten the passage time in the resonance frequency range.
[0019]
With such a configuration, in the process of decreasing the engine speed when the engine is stopped, the decreasing gradient can be moderated until the engine speed reaches the time of change, and the longitudinal G of the vehicle body can be suppressed. By making the descending gradient thereafter steep, for example, the time for passing through the resonance frequency region can be made shorter than before. As a result, the vehicle front-rear G due to a sudden change in the engine speed, and the vehicle front-rear G, vertical G (horizontal engine) or left-right G (vertical engine) due to passing through the resonance frequency range It can be effectively suppressed.
[0020]
In the above description, the engine speed that defines the change point is detected by monitoring the engine speed detecting means. However, the engine speed detecting means is not provided. Is also possible.
[0021]
For example, as described in claim 3, the time point of the change is considered to be after a predetermined time has elapsed from the time point when the engine stop condition is satisfied and the engine stop command is issued, and the automatic stop is performed in the same manner as described above. A device is conceivable.
[0022]
This is because the engine speed decreases while drawing a predetermined descending straight line (or descending curve) when a predetermined time elapses after the engine stop command is issued. For example, when the predetermined time is set to 0.1 seconds, the engine speed is gradually reduced until 0.1 seconds elapses after the engine stop command is issued and the stop mode is entered. After the elapse of time, control is performed so as to descend rapidly. This predetermined time is determined in advance from the time when the stop command is issued to the time of change (for example, the time from when the stop command is received until the engine speed reaches a speed slightly higher than the upper limit of the resonance frequency range). It is conceivable to obtain the time by experiment or the like and set the time. A timer or the like can be used to measure this time.
[0023]
Note that, in the automatic engine stop device for an AT vehicle, as shown in FIG. 2, the control of the descending gradient of the engine speed can be realized by the engine torque control by the engine torque control means. This focuses on the fact that the engine speed changes almost in proportion to the engine torque. Further, when the engine torque control means makes the output torque of the engine zero, the intake air amount control means can quickly reduce the intake air amount of the engine so that the descending gradient of the engine speed can be made steep. .
[0035]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below with reference to the drawings.
[0036]
In this embodiment, the automatic engine stop device according to the present invention is applied to an AT vehicle equipped with a 6-cylinder engine.
[0037]
As shown in FIG. 3, an intake pipe 2 for taking in air is connected to each cylinder of the engine 1, and an electronic throttle 3 and an electronic throttle 3 for adjusting the intake air flow rate are connected to the intake pipe 2. Bypass path 4 for bypassing and taking in air at idle, ISC 5 provided in bypass path 4 for adjusting the intake air quantity, upstream of electronic throttle 3 and ISC 5, and intake air quantity detection sensor 6 for detecting the intake air quantity , And a fuel injection device 7 and the like are provided. The electronic throttle 3 drives the throttle valve 3a with an actuator (not shown), and controls the intake air amount by its opening degree. The ISC 5 adjusts the intake air amount during idling by adjusting the opening of the control valve 5a with an actuator (not shown). Further, the engine 1 is provided with an ignition device 9, and the ignition device 9 includes an ignition plug 9a corresponding to the number of cylinders of the engine.
[0038]
An engine speed detection sensor 13 for detecting the rotation speed of the crankshaft 11 of the engine 1, that is, the engine speed, that is, the engine speed is attached. The torque converter 14 directly connected to the crankshaft 11 includes a pump 15, a turbine 16 and a stator 17, and an automatic transmission 20 is connected to an output shaft 18 of the turbine 16. The automatic transmission 20 has a plurality of solenoid valves, and when each solenoid valve is turned on / off, a hydraulic circuit corresponding to each transmission gear position is formed and a predetermined gear position is selected. The automatic transmission 20 is connected to an output shaft 24, and a vehicle speed sensor 25 is provided to detect the rotational speed of the output shaft 24 as a vehicle speed.
[0039]
The signals from the sensors are transmitted to an electronic control unit 30 (hereinafter referred to as “ECU 30”), and an actuator for driving the engine 1, the control valves, the automatic transmission 20, and the like The drive is controlled by the ECU 30.
[0040]
FIG. 4 shows the configuration of the control circuit of the automatic stop device of this embodiment.
[0041]
Although not shown, the ECU 30 is a CPU that controls various devices, a ROM in which various numerical values and programs are written in advance, a RAM in which numerical values and flags of calculation processes are written in a predetermined area, and an analog input signal that is converted into a digital signal. An A / D converter, an input / output interface (I / O) from which various digital signals are input and from which various digital signals are output, a timer, and a bus line to which these devices are respectively connected are configured. A control program shown in a flowchart described later is written in advance in the ROM.
[0042]
As shown in FIG. 4, the ECU 30 includes an engine speed detection sensor 13, a vehicle speed sensor 25, a shift position sensor that detects the current set range, a throttle position detection sensor that detects the throttle opening, and brake pedals. Output signals from the brake stroke detection sensor, the intake air amount detection sensor 6 and the like for detecting the depression amount are input via the I / O.
[0043]
Based on the information from each of these sensors, the CPU performs a calculation process according to a predetermined control program, and a control signal obtained from the calculation result, that is, an injection amount control signal, an electronic throttle opening setting signal An ignition timing control signal, an ISC opening setting signal, a VVT (variable valve timing control) signal, and the like are output to the engine side.
[0044]
Next, the engine stop control method of the automatic stop device executed by the control program will be described in detail with reference to FIGS.
[0045]
The automatic stop device of the present embodiment reduces the shock that occurs when the engine is stopped in the D range by controlling the engine speed according to the control program.
[0046]
In FIG. 5, an example of engine torque control in the present invention is shown by a solid line. In this control, the engine torque is controlled by adjusting the fuel injection amount. As a comparative example, a conventional control mode is indicated by a two-dot chain line.
[0047]
Specifically, in the descending process of the engine speed, a preset engine speed, that is, a time point when the engine speed becomes slightly higher than the upper limit of the resonance frequency range of the drive line is set as a change time point of the descending gradient, Control is performed so that the engine speed is gradually decreased until the time of the change, and the engine speed is rapidly decreased when the time of change has elapsed. For this reason, the descending gradient of the engine speed before the change time is gentler than before, and the descending gradient of the engine speed after the change time is steeper than before.
[0048]
That is, as shown in the upper part of FIG. 5, the engine speed rotates at a constant idling speed immediately after the vehicle stops. Then, when an automatic engine stop condition, which will be described later, is satisfied and an engine stop command is issued, as shown in the middle part of FIG. Reduced gradually. At this time, the engine speed gradually decreases in proportion to the decrease in engine torque. When the engine speed decreases to the preset speed, the fuel injection is stopped and the engine torque is rapidly reduced. At this time, the engine speed rapidly decreases in proportion to the decrease in engine torque.
[0049]
Further, when the engine speed is set in advance, the fuel injection is stopped as described above and the engine torque is drastically decreased. At the same time, as shown in the lower part of FIG. Reduce air volume and increase pumping loss. This is because there is a limit to the engine torque reduction (downward gradient) by fuel injection control, so that the pumping loss is increased by reducing the intake air amount to increase the mechanical resistance and promote the reduction of the engine speed. is there.
[0050]
As described above, after the change time point, the engine speed is drastically reduced by the synergistic effect of the reduction of the engine torque and the reduction of the intake air amount, thereby shortening the passing time in the resonance frequency range.
[0051]
Thus, in the control mode shown in FIG. 5, the engine speed gradually decreases until the engine speed reaches the time of change. For this reason, fluctuations in engine torque can be kept small until the time of change, and the longitudinal G of the vehicle body due to sudden changes in engine torque can be reduced. Also, in this case, the engine speed is controlled so that the gradient of decrease in the engine speed becomes steep after the time of change, but the engine speed has decreased to some extent by the time of change. Is small. For this reason, the front-rear G of the vehicle body due to a sudden change in engine torque can be kept small.
[0052]
Also, in the process of decreasing the engine speed, a change time is set when the engine speed reaches a slightly higher speed than the resonance frequency range, and the engine speed is controlled so that the gradient of the engine speed after this change becomes steep. Since the passing time in the frequency range is shortened, the front and rear G of the vehicle due to a sudden change in the engine speed, and the front and rear G, the vertical G and the left and right G of the vehicle due to passing through the resonant frequency range are effectively suppressed. be able to.
[0053]
Note that after the engine speed reaches zero, the ISC opening that is in the fully closed state is set to the fully open state. This is to facilitate smooth air intake when the engine is started next time as in the prior art.
[0054]
FIG. 6 shows an experimental result of measuring the magnitude of shock when the engine is vertically controlled as shown in FIG. 5 in comparison with the prior art. In this experiment, the front and rear G observed before passing through the resonance frequency range, and the left and right G and upper and lower G observed when passing through the resonance frequency are measured. In the figure, the solid line indicates the experimental result in the vehicle equipped with the apparatus of the present embodiment, and the double-dot chain line indicates the experimental result in the vehicle using the conventional apparatus. Note that the magnitude of the amplitude represents the magnitude of the shock generated in the vehicle.
[0055]
From the top of FIG. 6, in the vehicle equipped with the device of the present embodiment, the front-rear G generated when the engine speed before the resonance frequency passes is greatly reduced than the front-rear G generated in the vehicle equipped with the conventional device. I understand that Further, from the middle stage and the lower stage of FIG. 6, in the vehicle equipped with the device of this embodiment, the left and right G and the up and down G that are generated when the engine speed changes suddenly when the resonance frequency passes are It can also be seen that it is significantly lower than the upper and lower G.
[0056]
Thus, it can be seen that, by controlling the lowering state of the engine speed when the engine is stopped in a stepwise manner, the shock generated in the vehicle body as a whole is suppressed, and the driver's discomfort caused by this is eliminated.
[0057]
On the other hand, in FIG. 7, a mode in which engine torque is controlled by ignition timing control is shown by a solid line. As a comparative example, a conventional control mode is indicated by a two-dot chain line in the figure.
[0058]
In the example shown in FIG. 7, the control for gradually reducing the engine speed is performed by gradually shifting the ignition timing by the ignition device 9 to the retard side.
[0059]
That is, as shown in the upper part of FIG. 7, the engine speed rotates at a constant idling speed immediately after the vehicle stops. When an automatic engine stop condition (to be described later) is satisfied and an engine stop command is issued, the ignition torque is gradually shifted from the advance side to the retard side as shown in the middle part of FIG. Is gradually reduced. At this time, the engine speed gradually decreases in proportion to the decrease in engine torque.
[0060]
When the engine speed decreases to a preset engine speed, that is, to a time point (change time point) at which the engine speed is slightly higher than the upper limit of the resonance frequency range of the drive line, the ignition timing is fixed.
[0061]
Further, as shown in the lower part of FIG. 7, when the engine speed reaches the resonance frequency region, the ISC opening is adjusted to reduce the intake air amount and increase the pumping loss.
By reducing the intake air amount, the engine speed is drastically reduced and the passing time in the resonance frequency range is shortened.
[0062]
As described above, in the example shown in FIG. 7, in the process of decreasing the engine speed, the gentle decrease is performed by the ignition timing control, and the rapid decrease is performed by controlling the intake air amount. By controlling in this way, as in the case of the fuel injection amount control, the vehicle front-rear G due to a sudden change in the engine speed, and the vehicle front-rear G, vertical G, or left-right G due to passage through the resonance frequency range. Can be effectively suppressed.
Then, by controlling the descending state of the engine speed when the engine is stopped in stages, the front-rear G generated in the vehicle body as a whole is suppressed, and the driver's discomfort caused by this is eliminated.
[0063]
As in the example shown in FIG. 5 above, after the engine speed reaches zero, the ISC opening that has been fully closed is set to the fully open state. This is to facilitate smooth air intake when the engine is started next time.
[0064]
Further, since the effect of the embodiment shown in FIG. 7 is the same as the effect of the embodiment shown in FIG. 5 (FIG. 6), the description thereof is omitted.
[0065]
Next, a series of operations of the automatic stop / start device according to this embodiment will be described.
[0066]
FIG. 8 shows a flowchart of an automatic engine stop process executed by the ECU 30.
[0067]
First, when the vehicle stops at an intersection or the like, it is determined whether or not an engine stop condition is satisfied (S110). (1) The shift position detection sensor detects that the current drive is set to the D range. (2) The brake stroke detection sensor detects that the brake is fully depressed. (3) It is assumed that the engine stop condition is satisfied on the condition that the vehicle speed detected by the vehicle speed sensor 25 is detected to be zero.
[0068]
If it is determined that the engine stop condition is satisfied (S110: YES), the engine torque is gradually reduced according to the control method shown in FIG. 5 or 7 (S120).
[0069]
Then, the engine speed detection sensor 13 determines whether or not the engine speed has reached a preset speed, that is, a speed slightly larger than the upper limit of the resonance frequency range (S130). When it is determined that the engine speed has reached the engine speed (S130: YES), the engine torque is rapidly reduced and the intake air amount is reduced (S140). Then, the engine speed detection sensor 13 determines whether or not the engine speed has become zero (S150). If it is determined that the engine speed has become zero (S150: YES), the next engine start is started. Therefore, the intake air amount is set to the initial value (S160).
[0070]
With the above series of operations, the engine is stably stopped in the D range.
[0071]
Incidentally, Te embodiment odor, engine rotational speed sensor 13 corresponds to the engine speed detecting means.
[0072]
Of the processes executed by the ECU 30, the process of S1 30 corresponds to the process as the engine speed detecting means.
[0073]
As mentioned above, although the Example of this invention was described, it cannot be overemphasized that embodiment of this invention can take various forms, as long as it belongs to the technical scope of this invention, without being limited to the said Example at all. Nor.
[0074]
For example, in the above embodiment, a mode for controlling the fuel injection amount and a mode for controlling the ignition timing are shown as means for reducing the engine torque, but in addition to this, the ISC opening and the electronic throttle opening are controlled. It is also possible to adopt the form to do. In this case, the control mode is the same as the fuel injection amount control (see FIGS. 5 and 7).
[0075]
In this embodiment, the “change time point” is set to a time point when the engine speed is slightly larger than the upper limit of the resonance frequency range, but may be a time point when other conditions are satisfied.
[0076]
Further, in the above-described embodiment, the time point at which the engine torque is reduced and the time point at which the intake air amount is reduced are taken at the same time, but it goes without saying that these may be slightly changed. Explanation】
FIG. 1 is an explanatory diagram showing a control mode of engine speed applied to an automatic engine stop device of the present invention.
FIG. 2 is an explanatory diagram of an engine automatic stop control method applied to the engine automatic stop device of the present invention.
FIG. 3 is a schematic diagram of an engine automatic stop device according to an embodiment of the present invention.
FIG. 4 is a schematic configuration diagram of a control circuit that realizes automatic engine stop control according to an embodiment of the present invention.
FIG. 5 is an explanatory diagram of engine automatic stop control according to an embodiment of the present invention.
FIG. 6 is a diagram showing the effect of engine automatic stop control according to an embodiment of the present invention (vertical engine).
FIG. 7 is an explanatory diagram of further engine automatic stop control according to the embodiment of the present invention.
FIG. 8 is a flowchart showing an engine automatic stop process according to an embodiment of the present invention.
FIG. 9 is a diagram for explaining a problem of the prior art.
[Explanation of symbols]
1 ... engine, 2 ... intake pipe, 3 ... electronic throttle,
3a ... throttle valve, 4 ... bypass path,
5 ... Air amount control device (ISC) at idle, 5a ... Control valve,
6 ... intake air amount detection sensor, 7 ... fuel injection device,
9 ... Ignition device, 9a ... Ignition plug,
11 ... crankshaft, 13 ... engine speed detection sensor,
14 ... torque converter, 20 ... automatic transmission,
25 ... Vehicle speed sensor, 30 ... Electronic control circuit (ECU)

Claims (3)

When the engine stop condition is satisfied, in the automatic engine stop device of the AT car that lowers the engine speed in the drive range,
A change time point of the descending gradient of the engine speed is set,
The descending gradient of the engine speed before the change time is set more gently than the descending gradient of the engine speed after the change time,
Until the time of the change, combustion is continued to produce engine output torque,
An automatic engine stop device that stops combustion after the time of the change so as to make the output torque of the engine zero. The automatic engine stop device according to claim 1,
An engine speed detecting means for detecting the engine speed is provided,
The automatic engine stop device according to claim 1, wherein the change time point is a time point when the engine speed detected by the engine speed detecting means reaches a predetermined value or less in the descending process. When the engine stop condition is satisfied, in the automatic engine stop device of the AT car that lowers the engine speed in the drive range,
A change time point of the descending gradient of the engine speed is set,
The descending gradient of the engine speed before the change time is set more gently than the descending gradient of the engine speed after the change time,
An engine stop command is issued when the engine stop condition is satisfied,
The automatic engine stop device according to claim 1, wherein the change time point is after a predetermined time has elapsed since the stop command was issued.

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