Control method and control device for vehicle internal combustion engine

Abstract

A torque converter (3) disposed between an internal combustion engine (1) and an automatic transmission (2) has a lockup clutch (3a). During acceleration in a non-lockup state, such as when starting, torque limitation is performed to suppress excessive acceleration. Torque limitation is prohibited / released when a heating request is made (S1), when going uphill / pulling (S2), at high vehicle speed (S3), when the accelerator pedal opening is greater than or equal to a specified value (S4), when the torque limitation value exceeds the target torque (S5), in a gear other than the D gear (S6), or in a mode other than the normal mode (S7).

Description

Technical Field

[0001] The present invention relates to control of a vehicle internal combustion engine connected to an automatic transmission via a torque converter having a lock-up mechanism. Background Art

[0002] Patent document 1 discloses the following technology, namely, regarding a structure for connecting an internal combustion engine to an automatic transmission via a torque converter with a locking mechanism, when accelerating in a non-locking area such as just after the vehicle starts, the torque output by the internal combustion engine is limited to a lower level than the torque equivalent to the accelerator pedal opening input by the driver, thereby suppressing excessive acceleration (pickup, increase in rotational speed) of the internal combustion engine.

[0003] However, in the above-mentioned conventional technology, the torque of the internal combustion engine is always limited during acceleration in the unlocked state, which may cause problems such as insufficient vehicle driving force or inability to achieve the acceleration performance intended by the driver, depending on the situation.

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-125213 Summary of the Invention

[0005] The present invention relates to control of a vehicle internal combustion engine for limiting the torque of the internal combustion engine during acceleration in an unlocked state, wherein the torque limitation is prohibited when a predetermined condition is satisfied.

[0006] Even in the unlocked state under such specific conditions, torque limitation is prohibited, thereby allowing acceleration of the internal combustion engine under such conditions and obtaining the required torque, thereby enabling control appropriate to the situation. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a structural explanatory diagram showing the structure of a power transmission system of a vehicle according to the present invention.

[0008] Figure 2 This is a flowchart showing the flow of processing for prohibiting torque limitation during acceleration in the unlocked state.

[0009] Figure 3 This is a timing chart showing an example in which the accelerator pedal opening is greater than or equal to a predetermined opening as one of the prohibition conditions.

[0010] Figure 4 This is a timing chart of an example in which a heating request is input as one of the prohibition conditions.

[0011] Figure 5 This is a timing chart showing an example in which uphill slope determination is performed as one of the prohibition conditions.

[0012] Figure 6This is a timing chart showing an example of performing a traction determination as one of the prohibition conditions.

[0013] Figure 7 This is a timing chart showing an example of performing a high vehicle speed determination as one of the prohibition conditions.

[0014] Figure 8 This is a timing chart showing an example in which the vehicle is in a range other than the D range as one of the prohibition conditions.

[0015] Figure 9 This is a timing chart showing an example of a mode other than the normal mode as one of the prohibition conditions.

[0016] Figure 10 This is a timing chart showing a situation where the torque limit value exceeds the target torque. DETAILED DESCRIPTION

[0017] Hereinafter, one embodiment of the present invention will be described in detail based on the accompanying drawings.

[0018] Figure 1 This is an explanatory diagram showing the structure of a powertrain system for a vehicle to which the present invention is applied. This powertrain system includes an internal combustion engine 1 serving as a driving source, a belt-type continuously variable transmission (CVT) 2 serving as an automatic transmission, and a torque converter 3 located between the internal combustion engine 1 and the CVT 2. The internal combustion engine 1 can be either a gasoline or diesel engine. In one embodiment, it is a gasoline, spark-ignition engine. Furthermore, the automatic transmission can be a stepped transmission.

[0019] The torque converter 3 includes a lockup clutch 3 a capable of directly coupling a pump impeller as an input element and a turbine as an output element. The lockup clutch 3 a is engaged and disengaged by hydraulic control based on an output signal from a transmission controller 12 .

[0020] The continuously variable transmission 2 includes a primary pulley 2a on the driving side, a secondary pulley 2b on the driven side, and a metal belt 2c wound between them. The pulley width of the primary pulley 2a can be adjusted by hydraulic pressure, and the pulley width of the secondary pulley 2b changes accordingly, enabling stepless speed change. The transmission input shaft, which serves as the rotation axis of the primary pulley 2a, is connected to the output shaft of the torque converter 3 via a forward / reverse switching mechanism 4 utilizing a planetary gear mechanism. The transmission output shaft, which serves as the rotation axis of the secondary pulley 2b, transmits power to the drive wheels 6 via a final gear 5 and a differential gear (not shown). The speed ratio of the continuously variable transmission 2 is controlled by a transmission controller 12 based primarily on the accelerator pedal position and vehicle speed.

[0021] Furthermore, the continuously variable transmission 2 , the forward / reverse switching mechanism 4 , and the torque converter 3 are housed in a single housing 7 , and are mounted on the vehicle body together with the internal combustion engine 1 .

[0022] Fuel injection, ignition, etc. of the internal combustion engine 1 are controlled by an engine controller 11. The engine controller 11 and the transmission controller 12 are connected via an in-vehicle network 13 such as CAN communication, and transmit and receive necessary signals to each other.

[0023] Various sensors, switches, and the like, not shown in the figure, are connected to the controllers 11 and 12. For example, there are an accelerator opening sensor for detecting the opening of the accelerator pedal operated by the driver, a vehicle speed sensor for detecting the vehicle speed, an internal combustion engine rotational speed sensor for detecting the rotational speed of the internal combustion engine 1, a turbine rotational speed sensor for detecting the rotational speed of the turbine of the torque converter 3 (i.e., the rotational speed of the input shaft of the continuously variable transmission 2), and a water temperature sensor for detecting the temperature of the cooling water of the internal combustion engine 1.

[0024] The engagement / disengagement of the lockup clutch 3a of the torque converter 3 is controlled based on various operating conditions such as vehicle speed and accelerator pedal opening. For example, the lockup clutch 3a is in an unlocked state during startup acceleration and in a locked state during steady running.

[0025] Furthermore, during acceleration of the internal combustion engine 1 with the lockup clutch 3a in the unlocked state, the torque of the internal combustion engine 1 is limited to suppress excessive acceleration (increase in rotational speed) of the internal combustion engine 1 due to slippage of the torque converter 3. Specifically, the actual torque of the internal combustion engine 1 is limited to a relatively lower value compared to the target torque corresponding to the accelerator pedal opening. The transmission controller 12 limits the torque of the internal combustion engine 1 based on the torque limit value assigned to the engine controller 11. Specifically, the transmission controller 12 calculates the torque limit value required to suppress acceleration based on, for example, the speed difference between the input rotational speed of the torque converter 3 (i.e., the rotational speed of the internal combustion engine 1) and the output rotational speed (i.e., the transmission input rotational speed), and outputs this value to the engine controller 11. The engine controller 11 then performs torque limitation so that the output torque conforms to this torque limit value.

[0026] The torque can be limited by an appropriate method such as reducing the throttle opening (including reducing the fuel injection amount) or retarding the ignition timing.

[0027] Here, in this embodiment, the limitation of the torque during acceleration in the non-locked state is prohibited when a predetermined condition is satisfied.

[0028] Figure 2The flowchart shows the flow of a prohibition process for prohibiting torque limitation. The engine controller 11 sets / resets a flag indicating whether torque limitation should be prohibited (including cancellation) based on the flowchart.

[0029] In step 1, it is determined whether a heating request is being issued by the vehicle air conditioner (not shown). The determination of the presence of a heating request is based on a signal provided by the air conditioner to the engine controller 11. If a heating request is being issued, torque limitation is prohibited to ensure the cooling water temperature. In other words, if a heating request is being issued, the process proceeds from step 1 to step 9, where torque limitation is prohibited or released. If a heating request is not being issued, the process proceeds to step 2.

[0030] In step 2, a determination is made as to whether the vehicle is traveling uphill or towing. If so, the process proceeds to step 9, where torque limitation is inhibited or released. For example, the vehicle's uphill state can be determined by detecting the vehicle's inclination using a gravity sensor, or by detecting uphill travel using a GPS system utilizing high-precision map data. Furthermore, the vehicle's towing state (towing another vehicle) can be determined, for example, based on input from a switch on the vehicle's towing device that is activated during towing, or a switch located on the driver's seat that is operated by the driver.

[0031] When the vehicle is going uphill or towing, ensuring the driving force of the vehicle is a priority, so torque limitation is prohibited. If it is not going uphill or towing, the process proceeds to step 3.

[0032] In step 3, it is determined whether the vehicle is in a high-speed state, greater than or equal to a predetermined speed. If so, the process proceeds to step 9, where torque limitation is prohibited or released. Specifically, torque limitation is prohibited because high-speed conditions, such as when catching up or overtaking, may result in insufficient torque. If not, the process proceeds to step 4.

[0033] In step 4, a determination is made as to whether the accelerator pedal opening is greater than or equal to a predetermined opening. If so, the process proceeds to step 9, where torque limitation is prohibited or lifted. The "predetermined opening" in this context refers to an accelerator pedal opening greater than the opening corresponding to acceleration that would result in torque limitation in the unlocked state. In other words, a driver's deep depression of the accelerator pedal indicates a driver's request for sufficient acceleration performance, prioritizing ensuring driving force over suppressing acceleration of the internal combustion engine 1. If not, the process proceeds to step 5.

[0034] In step 5, a determination is made as to whether the torque limit value in the torque limitation process exceeds the target torque corresponding to the accelerator pedal opening. If the torque limit value exceeds the target torque, the process proceeds to step 9, where torque limitation is prohibited or released. For example, if the rotational speed differential of torque converter 3, which is in the unlocked state, decreases during vehicle acceleration from a standing start, the torque limit value is gradually increased until it exceeds the target torque. At this point, torque limitation is terminated. If the determination in step 5 is negative, the process proceeds to step 6.

[0035] In step 6, it is determined whether the continuously variable transmission 2 is in a gear other than D (drive). If it is in a gear other than D, such as a low-speed gear or reverse gear, the process proceeds to step 9, where torque limitation is disabled or lifted. For example, in a low-speed gear, vehicle acceleration performance is prioritized. If it is in D, the process proceeds to step 7.

[0036] In step 7, it is determined whether the shift mode of the continuously variable transmission 2 is a mode other than the normal mode. In a shift mode other than the normal mode, such as the sport mode, priority is given to vehicle acceleration performance, so the process proceeds to step 9 to prohibit or remove torque limitation. If the mode is the normal mode, the process proceeds to step 8.

[0037] In step 8, the prohibition flag indicating that the torque limitation should be prohibited is maintained in a reset state. In step 9, the prohibition flag is set to prohibit or release the torque limitation. Figure 2 As is clear from the flowchart, in this embodiment, the plurality of prohibition conditions shown in steps 1 to 7 are in a so-called OR relationship, and when any one of the conditions is satisfied, the prohibition flag is turned ON.

[0038] Next, based on Figure 3 The following timing chart illustrates an example where the accelerator pedal opening is greater than or equal to a predetermined opening as one of the prohibition conditions. This is the prohibition condition for step 4 described above. While the state of the lockup clutch 3a is not shown in the figure, the lockup clutch 3a is in the unlocked state during the period shown in the figure.

[0039] (a) in the figure represents the accelerator pedal opening, (b) represents the torque, and (c) represents the ON / OFF state of the aforementioned prohibition flag. The column (b) for torque shows the characteristics of three values: target torque T1, actual torque T2, and torque limit value Tlim. Target torque T1 is the value of the torque corresponding to the accelerator pedal opening, in other words, the torque requested by the driver by stepping on the accelerator pedal. Actual torque T2 is the torque actually output by the internal combustion engine 1 due to torque limitation. Strictly speaking, actual torque T2 is not a directly measured torque value, but an estimated value. Torque limit value Tlim is the value of the torque that the transmission controller 12 issues a command to the engine controller 11 based on the rotational speed difference of the torque converter 3 in the unlocked state. This torque limit value Tlim is a sufficiently high value as shown in the figure, such as in the initial state where torque limitation is not required.

[0040] At time t1, the accelerator pedal opening increases. At the start of acceleration, the prohibition flag is reset, but torque limit value Tlim remains high, preventing substantial torque restriction. Since the lockup clutch 3a is unlocked, the rotational speed difference between the input and output shafts of the torque converter 3 increases. Consequently, the transmission controller 12 reduces torque limit value Tlim assigned to the engine controller 11, thereby limiting the torque of the internal combustion engine 1. In other words, the actual torque T2 is less than the target torque T1 corresponding to the accelerator pedal opening, thus suppressing excessive acceleration of the internal combustion engine 1.

[0041] In the illustrated example, at time t2, if the accelerator pedal opening is detected to be greater than the specified opening, the prohibition flag is set to ON. Consequently, the torque limit is lifted. This release of the torque limit brings the actual torque T2 into line with the target torque T1. In other words, ensuring driving force is prioritized to achieve the acceleration performance desired by the driver.

[0042] and Figure 3 Similarly, Figures 4 to 9 Examples of timing charts corresponding to the prohibition conditions of steps 1, 2, 3, 6, and 7 are shown. Note that the changes in actual torque T2 are omitted in the timing charts. Actual torque T2 changes according to torque limit value Tlim during torque limitation and matches target torque T1 after torque limitation is lifted.

[0043] Figure 4 The timing diagram corresponds to the presence or absence of a heating request. If a heating request is generated at time t2 as shown in column (d), the prohibition flag turns on, and the torque limit is released. As a result, the internal combustion engine 1 operates at a relatively high torque, providing heat for heating to the cooling water.

[0044] Figure 5The timing diagram shows the prohibition of torque limitation during uphill driving. If the uphill state is determined at time t2 as shown in column (e), the prohibition flag turns on and the torque limitation is released. This allows for a higher driving force.

[0045] Figure 6 The timing chart shows the prohibition of torque limitation during towing. If it is determined at time t2 that towing is in progress, as shown in column (f), the prohibition flag turns on and the torque limitation is released. This allows a higher driving force to be obtained.

[0046] Figure 7 The timing diagram shows the prohibition of torque limitation at high vehicle speeds. If the vehicle speed is determined to be greater than or equal to the specified speed at time t2, as shown in column (g), the prohibition flag turns on, and the torque limitation is lifted. This allows for higher driving force at high vehicle speeds.

[0047] Figure 8 The timing diagram shows the prohibition of torque limitation associated with the gear position of the continuously variable transmission 2. If, as shown in column (h) at time t2, the gear position is determined to be other than D (e.g., a low-speed gear), the prohibition flag turns on, and the torque limitation is released. This allows for a higher driving force in accordance with the driver's wishes, such as in a low-speed gear.

[0048] Figure 9 The timing diagram shows the prohibition of torque limitation associated with the shift mode of the continuously variable transmission 2. If, as shown in column (i) at time t2, the shift mode is determined to be other than the normal mode (e.g., the sport mode), the prohibition flag turns on, and the torque limitation is lifted. This allows for a higher driving force that meets the driver's intent in the sport mode, etc.

[0049] In addition, Figures 4 to 9 In the timing chart of , if any prohibition condition is satisfied during the execution of the torque limitation, the torque limitation is released. However, if the prohibition condition is satisfied after the initial stage, the torque limitation is prohibited after the initial stage.

[0050] Figure 10 The timing diagram shows Figure 2 The torque limit corresponding to step 5 of the timing diagram is released. Specifically, after the accelerator pedal opening increases and acceleration begins at time t1, torque limit value Tlim is applied as described above to limit the torque of internal combustion engine 1. However, as the rotational speed difference of torque converter 3 decreases, torque limit value Tlim gradually increases. In the illustrated example, at time t2, torque limit value Tlim exceeds target torque T1 corresponding to the accelerator pedal opening, and the prohibition flag turns on, releasing the torque limit.

Claims

1. A method for controlling a vehicle internal combustion engine connected to an automatic transmission via a torque converter having a lock-up mechanism, wherein: During acceleration in the unlocked state, the torque of the internal combustion engine is limited by a torque limit value based on the speed difference between the input rotational speed and the output rotational speed of the torque converter. The above-mentioned torque limitation is prohibited when the predetermined conditions are met.

2. The method for controlling a vehicle internal combustion engine according to claim 1, wherein: As the predetermined condition, the torque limitation is prohibited when the accelerator opening is equal to or greater than a predetermined opening.

3. The control method for a vehicle internal combustion engine according to claim 1 or 2, wherein: As the predetermined condition, the limitation of the torque is prohibited when the vehicle is traveling uphill.

4. The method for controlling a vehicle internal combustion engine according to any one of claims 1 to 3, wherein: As the predetermined condition, the limitation of the torque is prohibited when the vehicle is towing another vehicle.

5. The control method for a vehicle internal combustion engine according to any one of claims 1 to 4, wherein: As the predetermined condition, the torque limitation is prohibited at a high vehicle speed equal to or higher than a predetermined vehicle speed.

6. The control method for a vehicle internal combustion engine according to any one of claims 1 to 5, wherein: As the predetermined condition, the torque limitation is prohibited when there is a request for heating the vehicle.

7. The control method for a vehicle internal combustion engine according to any one of claims 1 to 6, wherein: As the predetermined condition, the limitation of the torque is prohibited when the gear position of the automatic transmission is a gear position other than the D range.

8. The method for controlling a vehicle internal combustion engine according to any one of claims 1 to 7, wherein: As the predetermined condition, the limitation of the torque is prohibited when the shift mode of the automatic transmission is a mode other than the normal mode.

9. The method for controlling a vehicle internal combustion engine according to any one of claims 1 to 8, wherein: After the torque limitation is started, the torque limitation is released when the torque limitation value serving as the target during limitation becomes larger than the target torque corresponding to the accelerator opening.

10. A control device for a vehicle internal combustion engine, the vehicle internal combustion engine being connected to an automatic transmission via a torque converter having a lock-up mechanism, wherein: The control device includes a controller, The controller is configured to limit the torque of the internal combustion engine applied to the automatic transmission. During acceleration in the unlocked state, the torque of the internal combustion engine is limited by a torque limit value based on the speed difference between the input rotational speed and the output rotational speed of the torque converter. The above-mentioned torque limitation is prohibited when the predetermined conditions are met.

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