JP4884403B2 - Vehicle control method - Google Patents

Description

The present invention relates to a vehicle control method including an engine and an automatic transmission connected to the engine via a torque converter, and more particularly to a control method when shifting from the N range to the D range during traveling. is there.

The automatic transmission automatically determines the gear position from the shift diagram according to the driving conditions such as the vehicle speed and the throttle opening, and shifts. In such an automatic transmission, when the accelerator is depressed immediately after shifting from the N range to the D range, there is a possibility that a problem such as a decrease in durability due to engine blow-up or slipping of the friction engagement element may occur.

As a method for solving such a problem, Patent Document 1 describes a racing select, that is, when shifting to the D range or R range with the engine speed increased in the N range, depending on the accelerator depression amount immediately after the shift. A control device that performs engine torque reduction control has been proposed. In order to reduce the engine torque, for example, a method of suppressing fuel injection by a fuel injection valve or delaying ignition timing by an ignition device (retarding control) is employed.

FIG. 7 shows an example of engine torque reduction control (torque down control) disclosed in Patent Document 1. 7A shows the rotational speed, FIG. 7B shows the throttle opening, FIG. 7C shows the clutch hydraulic pressure, and FIG. 7D shows the required retarding level for the engine. When the shift is made from the N range to the D range at time t1, the clutch hydraulic pressure starts to gradually increase. If the accelerator is depressed at time t2, if the retard control is not performed, the engine speed increases as shown by the solid line, the rising of the clutch hydraulic pressure cannot catch up, and there is a concern that the engine blows up near time t6. On the other hand, when the retard control is performed simultaneously with the depression of the accelerator, an increase in engine speed is suppressed as shown by a broken line, and an engine blow-up can be suppressed. In addition, a dashed-dotted line is the synchronous turbine rotation speed in D range.

As shown in FIG. 7, the retard request to the engine is triggered by engine idle switch off (accelerator on), and retard control is started simultaneously with the depression of the accelerator. Thus, when the retard control is started simultaneously with the depression of the accelerator when shifting from the N range to the D range, if the retard is applied too much, the engine speed immediately after time t2 (indicated by the region A) decreases too much, There is concern that engine stall will occur. On the other hand, if the retardation is small, engine blow-up near time t6 (indicated by region B) cannot be suppressed, and the durability of the clutch may be reduced. Thus, the conventional engine torque reduction control has a problem that the degree of freedom for achieving both clutch protection and engine stall resistance is small.

On the other hand, in Patent Document 2, when shifting from the N range to the D range during traveling, the clutch hydraulic pressure after the shift from the N range to the D range is gradually increased. A method of entering the connection completion state and preventing the engine from blowing up is disclosed. However, this method is intended only to prevent the engine from being blown up when the accelerator is depressed, and a shock is likely to occur because the clutch is suddenly engaged.
JP-A-7-96779 JP-A-8-177893

Therefore, an object of the present invention is to prevent engine stall and clutch durability deterioration when shifting from the neutral range to the travel range during traveling, and to achieve both freedom of clutch protection and engine stall resistance. An object of the present invention is to provide a method for controlling a large vehicle.

In order to achieve the above object, the present invention comprises an engine and an automatic transmission in which engine power is transmitted via a torque converter, and the automatic transmission is a frictional engagement by hydraulic control according to at least the vehicle speed and the throttle opening. In a vehicle that is capable of shifting to a traveling range in which engine power is transmitted to wheels and a neutral range in which engine power is not transmitted to wheels, while performing connection / disconnection control of the coupling element and selecting a desired gear stage Detecting the shift from the neutral range to the traveling range, detecting the accelerator depression, and estimating the synchronous turbine speed in the traveling range when the shift is detected and the accelerator is depressed. A step of subtracting the estimated synchronous turbine rotational speed from the engine rotational speed; If the calculated value is negative and the absolute value exceeds a predetermined value, engine torque reduction control is prohibited, and engine torque reduction control is performed when the calculated value is other than the above. And a method for controlling the vehicle.

In the present invention, when shifting from the neutral range to the travel range during travel and when the accelerator is depressed, it is determined whether or not the engine torque reduction control is to be performed by determining whether the engine speed and travel range at that time are to be executed. This is based on the difference from the synchronous turbine rotational speed at. First, the synchronous turbine rotation speed in the travel range is estimated. The synchronous turbine rotational speed is estimated based on the vehicle speed, throttle opening, and the like, and the synchronous turbine rotational speed is estimated from the shift speed and the vehicle speed. Next, the synchronous turbine speed is subtracted from the engine speed. When the subtracted calculated value is a negative value and the absolute value thereof exceeds a predetermined value, that is, when the engine speed is lower than the synchronous turbine speed by a predetermined amount or more, engine torque reduction control is prohibited. In this way, when the engine speed is lower than the synchronous turbine speed by a predetermined value or more, the engine torque reduction control is prohibited, thereby eliminating the possibility of engine stall due to a decrease in engine speed. On the other hand, if the value obtained by subtracting the synchronous turbine rotational speed from the engine rotational speed is a positive value or a negative value, but the absolute value is not more than the predetermined value, engine torque reduction control is performed. However, engine torque reduction control is performed because there is no fear of engine stall and it is possible to suppress a decrease in clutch durability due to engine blow-up. As described above, in the present invention, it is determined whether or not the engine torque reduction control is to be performed based on the difference between the engine speed and the synchronous turbine speed. Therefore, the engine torque reduction control can be performed only when necessary. This makes it possible to achieve both engine stall resistance and clutch protection.

The predetermined value that is a criterion for determining whether or not to perform engine torque reduction control is, for example, about 100 to 500 rpm. This rotational speed difference is determined based on the stall resistance performance. The engine torque reduction control method can be implemented, for example, by retarding the ignition timing of the engine ignition device, throttle control of the electronic throttle, injection control of the fuel injection valve, or the like. Of these, the retard angle control has the highest response, so it is desirable for the torque down control.

When the calculated value obtained by subtracting the synchronous turbine rotational speed from the engine rotational speed is positive, it is desirable that the reduction amount of the engine torque is larger than the negative case. That is, when the engine speed is higher than the synchronous turbine speed, the engine torque reduction amount is increased, and when the engine speed is lower than the synchronous turbine speed, the engine torque reduction amount is decreased. Thus, there is an advantage that engine blow-up can be quickly reduced.

It is desirable to include a step of reading the engine torque along with calculation of a calculation value obtained by subtracting the synchronous turbine rotation speed from the engine rotation speed, and to control the engine reduction amount based on these values. For example, in relation to the engine torque and the difference between the engine speed and the synchronous turbine speed, a reduction amount of the engine torque (for example, a required retard angle level) is set as a two-dimensional map. For example, the retard angle request level may be set to increase as the engine torque increases, and the retard angle request level to increase as the difference between the engine speed and the synchronous turbine speed increases. Then, in accordance with the actual engine torque and the difference between the engine speed and the synchronous turbine speed, a reduction amount of the engine torque may be read from the two-dimensional map and controlled so as to be the reduction amount. In this method, the amount of torque reduction of the engine is finely controlled according to the degree of deviation from the synchronous turbine rotational speed of the travel range, so that synchronization can be completed quickly while reducing engine blow-up.

As described above, according to the present invention, when the vehicle is shifted from the neutral range to the traveling range during traveling and the accelerator is depressed, it is determined whether or not to perform the engine torque reduction control at that time point. Since the engine speed is controlled based on the difference between the engine speed and the synchronous turbine speed in the travel range, optimal engine torque reduction control can be performed, and both engine stall resistance and clutch protection can be achieved.

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

FIG. 1 shows a vehicle system equipped with an automatic transmission according to the present invention. The output of the engine 1 is transmitted to the transmission mechanism 4 via the torque converter 3 of the automatic transmission 2, and the transmission mechanism 4 is connected to wheels (not shown) via the output shaft 5. The automatic transmission 2 includes a hydraulic control device 7, and a plurality of solenoid valves 7 a to 7 c provided in the hydraulic control device 7 are controlled by the control unit 20, so that the friction engagement incorporated in the transmission mechanism 4. The hydraulic pressure of the element is controlled according to the running state. Here, an example in which the hydraulic control device 7 is provided with three solenoid valves 7 a to 7 c is shown, but the solenoid valves can be appropriately increased or decreased for various controls of the automatic transmission 2.

The control unit 20 includes an engine speed sensor 21 to an engine speed, a throttle opening sensor 22 to a throttle opening, a turbine speed sensor 23 to a turbine speed, a vehicle speed sensor 24 to a vehicle speed, and a shift position switch 25 to P and R. , N, D, L shift position signals, and an idle switch signal from the idle switch 26 are input. Other signals may be input. In addition to the shift control of the automatic transmission 2, the control unit 20 also performs engine torque-down control as will be described later, and controls the ignition timing (retard) in the ignition device 6 of the engine 1 for that purpose. .

FIG. 2 shows an example of the speed change mechanism 4 of the automatic transmission 2. The speed change mechanism 4 includes an input shaft 10 to which engine power is transmitted via a torque converter 3, three clutches C1 to C3 and two brakes B1 and B2, which are friction engagement elements, a one-way clutch F, a Ravigneaux type planet, A gear mechanism 11 and a differential device 14 are provided.

The forward sun gear 11a and the input shaft 10 of the planetary gear mechanism 11 are connected via a C1 clutch, and the rear sun gear 11b and the input shaft 10 are connected via a C2 clutch. The carrier 11c is connected to the center shaft 15, and the center shaft 15 is connected to the input shaft 10 via a C3 clutch. The carrier 11c is connected to the transmission case 16 via a B2 brake and a one-way clutch F that allows only forward rotation (engine rotation direction) of the carrier 11c. The carrier 11c supports two types of pinion gears 11d and 11e, the forward sun gear 11a meshes with a long pinion 11d having a long axial length, and the rear sun gear 11b meshes with the long pinion 11d via a short pinion 11e having a short axial length. . A ring gear 11f that meshes only with the long pinion 11d is coupled to the output gear 12. The output gear 12 is connected to the differential device 14 via the intermediate shaft 13.

FIG. 3 shows the operations of the clutches C1, C2, C3, the brakes B1, B2 and the one-way clutch F provided in the transmission mechanism 4. In FIG. 3, the black circles indicate the action state of the hydraulic pressure in the clutch and the brake, and the locked state in the one-way clutch. In the P and N ranges (neutral range), all the friction engagement elements are released, and in the R range, the C1 clutch and the B2 brake are engaged. In the D range, the C2 clutch is engaged at the first speed, the one-way clutch F is locked, the C2 clutch and the B1 brake are engaged at the second speed, and the C2 clutch and the C3 clutch are engaged at the third speed. The C3 clutch and the B1 brake are engaged at the fourth speed. In the L range, the C2 clutch and the B2 brake are engaged.

The control unit 20 stores a shift map of the automatic transmission 2, a power on / off determination map, and the like, and controls the solenoid valve according to a preset program. In addition to the control map for the automatic transmission 2, a map for engine torque-down control is set. FIG. 4 is an example of a retardation request level map for torque down control, where the X-axis is engine torque, the Y-axis is the difference between the engine speed and the D-range synchronous turbine speed, and these engine torque and engine speed The required retarding level of the ignition timing is set according to the difference (ΔN) between the number and the D range synchronous turbine rotation speed. The retardation request level is not a retardation request amount itself but a coefficient for the retardation request amount. The larger the numerical value, the greater the retardation amount. Specifically, the retardation request level increases as the engine torque increases. As the level increases and the difference ΔN between the engine speed and the D-range synchronous turbine speed increases, the required retard angle level is set larger. Therefore, when the engine torque is large and the difference ΔN between the engine speed and the D range synchronous turbine speed is large, the retardation request amount increases and the engine torque down amount also increases.

FIG. 5 shows an example of a flowchart of engine torque-down control in the present invention. When starting, it is determined whether the vehicle speed is equal to or higher than a predetermined vehicle speed V ₀ (for example, 10 km / h), and it is determined whether the vehicle is traveling (step S1). The vehicle speed V ₀ is set, for example, using a rotational speed at which the engine rotational speed is close to the idle rotational speed as a guide. Next, it is determined whether or not the shift lever has been shifted from the N range to the D range (step S2). This determination is continued for a predetermined time after the shift to the D range. Next, when the shift is made to the D range, the depression of the accelerator is detected (step S3). This detection can be detected based on whether the idle switch 26 is turned off. When the depression of the accelerator is detected, the synchronous turbine rotation speed Nt in the D range is estimated (step S4). The synchronous turbine rotational speed Nt can be obtained by calculation from the gear ratio of the gear and the vehicle speed after estimating the gear in the D range from the throttle opening and the vehicle speed at that time.

Next, a difference ΔN between the engine speed Ne and the synchronous turbine speed Nt obtained in step S4 is calculated (step S5).
ΔN = Ne−Nt
It is determined whether the difference value ΔN is a negative value and its absolute value is greater than a predetermined value α (step S6). That is, it is determined whether ΔN <0 and | ΔN |> α. The predetermined value α is set based on the stall resistance performance, and is preferably about 300 rpm, for example. If ΔN <0 and | ΔN |> α, the required retard amount to the engine is kept at 0. That is, engine torque-down control is prohibited (step S7). On the other hand, when ΔN ≧ 0, or when ΔN <0 and | ΔN | ≦ α, torque down control is performed (step S8).

FIG. 6 shows some examples of torque-down control in the present invention. 6, (a) is the engine speed, (b) is the throttle opening, (c) is the engine torque, (d1) is the first embodiment of torque down control, (d2) is the second embodiment, d3) shows a third embodiment.

When the shift lever is switched from the N range to the D range at time t1, the gear position is determined according to the shift map from the vehicle speed and the throttle opening at that time, and the friction engagement element to be engaged is determined. For example, when the gear position at that time is the third speed, the friction engagement elements to be engaged are the C2 clutch and the C3 clutch, so that hydraulic pressure is supplied to these clutches simultaneously with switching to the D range. . When the accelerator is depressed at time t2, the idle switch is turned off and control is started. First, a difference ΔN between the engine speed Ne at this time t2 and the synchronous turbine speed Nt of the D range is obtained. If ΔN <0 and | ΔN |> α, the retardation request amount to the engine is set to 0. Leave as it is. That is, engine torque-down control is prohibited. In cases other than the above (for example, when ΔN ≧ 0, ΔN <0 and | ΔN | ≦ α), torque down control is performed. In FIG. 6, since the difference value ΔN at time t2 is ΔN <0 and | ΔN |> α, torque down control is prohibited from time t2 to time t3 when ΔN = −α.

Thus, since the torque-down control is prohibited between times t2 and t3 when the engine speed is low, it is possible to suppress a decrease in the engine speed when the accelerator is depressed and to prevent engine stall. On the other hand, when ΔN ≧ 0, or when ΔN <0 and | ΔN | ≦ α, the torque-down control is performed, so that the engine speed can be reliably prevented from rising.

As an implementation method, in the first embodiment (d1), the retardation request amount is made constant, and torque reduction control is performed from time t3 when ΔN = −α to time t5 when the engine speed almost converges.
In the second embodiment (d2), from the time t3 to the time t4 when ΔN = 0, the retardation request amount is set to a small value to suppress the torque down control. That is, while the differential rotation ΔN takes a negative value, the reduction amount of the engine torque is reduced and the decrease in the engine speed is suppressed. After time t4 when ΔN ≧ 0, the retardation request amount is made constant as in the first embodiment, and the processing is performed until time t5 when the engine speed almost converges. That is, when the differential rotation ΔN becomes positive, the engine torque reduction amount is increased to quickly suppress the engine speed from being increased.
The third embodiment (d3) is the same as the first and second embodiments in that torque down control is started at time t3, but the retardation request amount is varied in consideration of the engine torque value. . More specifically, the retard request amount is determined from the engine torque and the differential rotation ΔN according to the retard request amount map shown in FIG. 4, and torque down control is performed according to the retard request amount. In this way, the required amount of retardation is determined by the engine torque and the differential rotation ΔN, and the amount of torque reduction is finely controlled by the degree to which the engine speed deviates from the synchronous turbine speed in the D range. The synchronization can be completed quickly while reducing.

In the third embodiment (d3), the required retardation amount is changed according to the engine torque. However, since the engine torque and the throttle opening are correlated, the engine torque may be estimated from the throttle opening. That is, the required retardation amount may be changed according to the throttle opening.

In FIG. 6, the example in which the accelerator is depressed after shifting from the N range to the D range has been described, but the accelerator may be depressed before shifting from the N range to the D range. In this case, since the engine speed is expected to be higher than the synchronous turbine speed of the D range, the torque down control is started simultaneously with the shift from the N range to the D range as in the prior art.

In the above embodiment, the torque down control is performed by the retard amount of the ignition timing of the engine ignition device, but may be performed by the throttle control of the electronic throttle, the injection control of the fuel injection valve, or the like. However, since the retard angle control has the highest response, it is desirable for the torque down control.
The automatic transmission according to the present invention is not limited to an automatic transmission having three clutches C1 to C3 and two brakes B1 and B2 as shown in FIG.

It is a system diagram carrying the automatic transmission for vehicles in the present invention. FIG. 2 is a skeleton diagram of a transmission mechanism of the automatic transmission of FIG. 1. 3 is an operation table of each friction engagement element of the speed change mechanism shown in FIG. 2. It is an example of the retardation request | requirement level map set to the control unit. It is a flowchart figure of an example of the torque down control in this invention. It is a time chart figure of an example of torque down control in the present invention. It is a time chart figure of torque reduction control in the past.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Automatic transmission 3 Torque converter 4 Transmission mechanism 6 Ignition device 20 Control unit 21 Engine speed sensor 22 Throttle opening sensor 23 Turbine speed sensor 24 Vehicle speed sensor 25 Shift position sensor 26 Idle switch

Claims (3)

An engine and an automatic transmission in which engine power is transmitted via a torque converter, the automatic transmission performing at least connection / disconnection control of a friction engagement element by hydraulic control according to at least a vehicle speed and a throttle opening, In a vehicle that can be shifted to a traveling range that transmits engine power to wheels and a neutral range that does not transmit engine power to wheels,
Detecting a shift from the neutral range to the driving range during driving;
Detecting the depression of the accelerator,
A step of detecting the shift and estimating the synchronous turbine rotation speed in the travel range when the accelerator is depressed; and
Subtracting the estimated synchronous turbine speed from the engine speed;
A step of prohibiting engine torque reduction control when the subtracted calculated value is a negative value and the absolute value thereof exceeds a predetermined value;
And a step of performing engine torque reduction control when the subtracted calculated value is other than the above. The control method according to claim 1, wherein when the calculated value obtained by subtraction is positive, the reduction amount of the engine torque is set larger than when the calculated value is negative. 3. The control method according to claim 1, further comprising a step of reading engine torque along with the calculation of the subtracted calculated value, and controlling a reduction amount of the engine based on these values.

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