Vehicle Control Systems

Abstract

To prevent a driver from excessively stepping on an accelerator pedal in a state where a vehicle is traveling on a bad road and thereby preventing a drive wheel from spinning free and to prevent abrupt vehicle behavior in response to abrupt operation made to an accelerator pedal.SOLUTION: As a control system of a vehicle, a controller 14: determines an idling rotation speed of an engine 2; controls the engines 2 so that a rotation speed of the engine 2 while the same is idling corresponds to the idling rotation speed; and controls a lock-up clutch 4b so as to be switchable among a plurality of states including an engaged state and a disengaged state. When an off-road mode is selected through a travel mode selection switch SN1, the controller 14 sets the idling rotation speed higher than the same when a normal mode is selected and prohibits the lock-up clutch from being put into the engaged state.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a control system for a vehicle having an engine that provides power to drive drive wheels. [Background technology]

[0002] Conventionally, a technique has been proposed for intentionally releasing a lock-up clutch in order to suppress vibrations that occur in the vehicle body when the vehicle is traveling on a rough road. For example, Patent Document 1 discloses a technique for forcibly releasing the lock-up clutch when it is detected that the vehicle is traveling on a rough road, thereby reducing the mass of the powertrain that is connected to each other, thereby reducing the vibrations that occur in the vehicle body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-298145 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, when driving on a rough road with a rough surface such as an unpaved road, the driver tends to depress the accelerator pedal more than when driving on a paved road. However, the coefficient of friction of a rough road is generally small, so the driving wheels are more likely to spin. That is, even though the driving wheels are more likely to spin when driving on a rough road than usual, the driver depresses the accelerator pedal more than usual, so the driving torque transmitted to the driving wheels becomes excessive, making the driving wheels more likely to spin. In addition, the vehicle shakes due to the roughness of the road surface, so it is difficult to operate the accelerator pedal precisely, and the driver often depresses the accelerator pedal too much due to sudden vibrations. As a result, the vehicle accelerates suddenly and shocks occur.

[0005] To address this issue, it is conceivable to increase the engine idle speed to increase the driving torque from the idling engine, making it easier for the driver to move the vehicle forward without having to press the accelerator pedal hard. However, in this case, if the vehicle shakes due to unevenness in the road surface and the driver presses the accelerator pedal too hard, the driving torque from the engine will be large, which will result in sudden acceleration and greater shock for the vehicle. In addition, the technology described in the above-mentioned Patent Document 1 does not control the lock-up clutch taking into account excessive pressing of the accelerator pedal and increases in the idle speed when driving on rough roads.

[0006] The present invention has been made to solve the problems of the conventional technology described above, and has an object to provide a vehicle control system that prevents the driver from pressing the accelerator pedal excessively when driving on rough roads, thereby suppressing spin of the drive wheels, and that can suppress sudden vehicle behavior in response to sudden operation of the accelerator pedal. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a vehicle engine that supplies power for driving drive wheels, a torque converter that is provided on a power transmission path of the engine and has a lock-up clutch, and a lock-up clutch that is connected to an output shaft of the torque converter. 3 tiers or morea first driving mode selection means for selecting one of a plurality of driving modes including a first driving mode for normal driving and a second driving mode for driving on rough roads in response to an operation by a driver of the vehicle; an engine control means for determining an idle speed of the engine and controlling the engine so that the engine speed during idling is the idle speed; and a lock-up clutch control means for controlling a lock-up clutch to be switchable between a plurality of states including an engaged state and a released state, wherein when the second driving mode is selected by the driving mode selection means, the engine control means makes the idle speed higher than when the first driving mode is selected, and when the second driving mode is selected by the driving mode selection means, the lock-up clutch control means prohibits the lock-up clutch from being engaged, and when the second driving mode is selected by the driving mode selection means, permits the lock-up clutch to be engaged when the automatic transmission is in second gear and the vehicle speed is equal to or higher than a predetermined value, even when the second driving mode is selected by the driving mode selection means. Even when the second driving mode is selected by the driving mode selection means, if the automatic transmission is in the third gear or higher, the lock-up clutch is permitted to be in the engaged state regardless of the vehicle speed. The present invention is characterized by the above. According to the present invention thus configured, in a situation where the driver recognizes that the vehicle is traveling on a bad road and is likely to depress the accelerator pedal heavily, and the drive wheels are likely to spin, the engine control means sets the idle speed high, and the lock-up clutch control means prevents the lock-up clutch from being engaged. This makes it possible to increase the drive torque from the idling engine, so that the vehicle can easily move forward without the driver having to depress the accelerator pedal heavily. Even if the vehicle shakes due to unevenness in the road surface and the driver depresses the accelerator pedal too much, the lock-up clutch is released, so the transmission of drive torque to the drive wheels is mitigated, and sudden acceleration of the vehicle and shocks can be suppressed. Therefore, excessive depressing of the accelerator pedal by the driver is prevented, and the drive wheels are suppressed from spinning, and sudden behavior of the vehicle in response to sudden operation of the accelerator pedal can be suppressed. Also, in a situation where the torque required to drive the drive wheels is relatively large, even if the vehicle shakes due to unevenness in the road surface and the driver depresses the accelerator pedal too much, sudden acceleration of the vehicle and shocks are unlikely to occur. Therefore, by allowing the lock-up clutch to be in the engaged state, the transmission efficiency of the torque converter can be improved, and the fuel efficiency of the vehicle can be improved.

[0008] In the present invention, the vehicle control system preferably has gradient measurement means for measuring a road surface gradient along a longitudinal direction of the vehicle, and when the road surface gradient measured by the gradient measurement means is an upward gradient greater than a predetermined value in the vehicle's traveling direction and the second traveling mode is selected by the traveling mode selection means, the engine control means increases the idle speed compared to when the road surface gradient is equal to or less than the predetermined value and the second traveling mode is selected. According to the present invention thus configured, in a situation where the driver recognizes that the vehicle is traveling on a bad road and is likely to depress the accelerator pedal heavily, and further in a situation where the vehicle is traveling on a slope with an upward gradient greater than a predetermined value and where the drive wheels are likely to spin, the engine control means sets the idle speed even higher. This makes it possible to increase the drive torque from the engine during idling, so that the vehicle can easily move forward without the driver having to depress the accelerator pedal heavily. This prevents the driver from depressing the accelerator pedal excessively, and suppresses spinning of the drive wheels.

[0011] In another aspect, the present invention provides a transmission for a vehicle including an engine that supplies power for driving a driving wheel, a torque converter that is provided on a power transmission path of the engine and has a lock-up clutch, and a transmission for a vehicle connected to an output shaft of the torque converter. 3 tiers or more a drive mode selection switch that receives an operation for selecting one of a plurality of drive modes including a first drive mode for normal drive and a second drive mode for drive on rough roads, a memory that stores programs, and a processor that executes the programs, wherein the processor determines an idle speed of the engine, controls the engine so that the engine speed becomes the idle speed when idling, controls a lock-up clutch to be switchable between a plurality of states including an engaged state and a released state, and when the second drive mode is selected by the drive mode selection switch, makes the idle speed higher than when the first drive mode is selected, and prohibits the lock-up clutch from being engaged, and even when the second drive mode is selected by the drive mode selection switch, allows the lock-up clutch to be engaged when the automatic transmission is in second gear and the vehicle speed is equal to or higher than a predetermined value. Even if the second driving mode is selected by the driving mode selection switch, if the automatic transmission is in third gear or higher, the lock-up clutch is permitted to be engaged regardless of the vehicle speed. The present invention is characterized in that it is configured to According to the present invention configured as described above, in a situation where the driver recognizes that the vehicle is traveling on a bad road and is likely to depress the accelerator pedal heavily, and the drive wheels are likely to spin, the processor sets the idle speed high and prevents the lock-up clutch from being engaged. This makes it possible to increase the drive torque from the idling engine, so that the vehicle can easily move forward without the driver having to depress the accelerator pedal heavily. In addition, even if the vehicle shakes due to unevenness in the road surface and the driver presses the accelerator pedal too hard, the lock-up clutch is released, so the transmission of drive torque to the drive wheels is mitigated, and the occurrence of sudden acceleration and shock of the vehicle can be suppressed. Therefore, it is possible to prevent the driver from excessively depressing the accelerator pedal and suppress the idle of the drive wheels, and to suppress the sudden behavior of the vehicle in response to a sudden operation of the accelerator pedal. In addition, in a situation where the torque required to drive the drive wheels is relatively large, even if the vehicle shakes due to unevenness in the road surface and the driver presses the accelerator pedal too hard, the vehicle is unlikely to accelerate suddenly or shock. Therefore, by allowing the lock-up clutch to be engaged, the transmission efficiency of the torque converter can be improved, and the fuel efficiency of the vehicle can be improved. Effect of the Invention

[0012] According to the vehicle control system of the present invention, when driving on rough roads, it is possible to prevent the driver from pressing the accelerator pedal excessively, thereby suppressing spin of the drive wheels, and also to suppress sudden vehicle behavior in response to sudden operation of the accelerator pedal. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic configuration diagram of a vehicle to which a vehicle control system according to an embodiment of the present invention is applied. [Diagram 2] 1 is a block diagram showing an electrical configuration of a vehicle control system according to an embodiment of the present invention. [Diagram 3] 4 is a flowchart of a vehicle control process according to an embodiment of the present invention. [Figure 4] FIG. 4 is an explanatory diagram showing the relationship between a road surface gradient and a corrected engine revolution speed. [Diagram 5] 4 shows an example of a time chart when vehicle control according to the embodiment of the present invention is executed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A control device for a hybrid vehicle according to an embodiment of the present invention will now be described with reference to the accompanying drawings.

[0015] <Device configuration> First, the overall configuration of a vehicle to which a vehicle control system according to an embodiment of the present invention is applied will be described with reference to Fig. 1. Fig. 1 is a schematic configuration diagram of a vehicle to which a vehicle control system according to an embodiment of the present invention is applied.

[0016] As shown in FIG. 1, the vehicle 1 mainly has an engine 2, a torque converter 4, an automatic transmission 6, a front drive shaft 8, a pair of left and right front wheels 10, a pair of left and right rear wheels 12, a controller 14, a driving mode selection switch SN1, a wheel speed sensor SN2, an acceleration sensor SN3, a steering angle sensor SN4, and a shift position sensor SN5.

[0017] The vehicle 1 is a front engine, front drive (FF) two-wheel drive vehicle, with the front wheels 10 functioning as drive wheels. The vehicle 1 is also configured to steer the front wheels 10 in response to operation of a steering wheel (not shown). Note that at least a part of the present invention is not limited to application to the drive type of a four-wheel drive vehicle as shown in FIG. 1, but can also be applied to various drive types (for example, two-wheel drive vehicles such as FF or front engine, rear drive (FR) vehicles, and four-wheel drive vehicles based on the FF or FR systems, etc.).

[0018] The engine 2 burns a mixture of fuel and air to generate a driving torque (engine torque) as a propulsive force for the vehicle 1, and transmits the driving torque to the torque converter 4. The torque converter 4 includes a torus 4a that transmits the driving torque of the engine 2 to the automatic transmission 6 by fluid, and a lock-up clutch 4b that mechanically connects the engine 2 and the automatic transmission 6 directly. The automatic transmission 6 is a multi-speed gear mechanism that converts the rotation speed and torque by combining gears. Gears are switched using hydraulic pressure supplied from an oil pump (not shown). The automatic transmission 6 transmits the driving torque transmitted from the engine 2 via the torque converter 4 to the front wheels 10 via a front drive shaft 8.

[0019] The driving mode selection switch SN1 is a switch for selecting one of the driving modes, a normal mode (first driving mode) for normal driving on a smooth road surface such as a paved road, and an off-road mode (second driving mode) for driving on a rough road surface with severe bumps such as an unpaved road, and is disposed in a position where the driver of the vehicle 1 can operate it (typically on the center console or dashboard in the vehicle cabin). The driving mode selection switch SN1 may be capable of selecting other driving modes (e.g., sports mode, snow mode, etc.) in addition to the normal mode and the off-road mode. The wheel speed sensor SN2 detects the wheel speed. Typically, the wheel speed sensor SN2 is provided on each of the left and right front wheels 10 and the left and right rear wheels 12, and detects the speed of each wheel. The acceleration sensor SN3 is typically a three-axis acceleration sensor capable of measuring the acceleration of the vehicle 1 in three axes, namely, the front-rear direction, the left-right direction, and the up-down direction. The steering angle sensor SN4 detects the steering angle of the vehicle 1. For example, the steering angle sensor SN4 detects the steering angle based on the rotation angle of a steering shaft (not shown). The shift position sensor SN5 detects a shift position (e.g., P range, R range, D range, etc.) selected by a shift lever or paddle switch (not shown). The driving mode selection switch SN1, the wheel speed sensor SN2, the acceleration sensor SN3, the steering angle sensor SN4, and the shift position sensor SN5 output detection signals corresponding to the detected driving mode, wheel speed, acceleration, steering angle, and shift position, respectively, to the controller 14.

[0020] Next, FIG. 2 is a block diagram showing the electrical configuration of the vehicle control system according to the embodiment of the present invention.

[0021] As shown in FIG. 2, the controller 14 receives as input a signal from a driving mode selection switch SN1, a signal from a wheel speed sensor SN2, a signal from an acceleration sensor SN3, a signal from a steering angle sensor SN4, and a signal from a shift position sensor SN5.

[0022] The controller 14 is configured by a computer having one or more processors 14a (typically a CPU), various programs (including basic control programs such as an OS and application programs that are started on the OS and realize specific functions) interpreted and executed on the processor, and a memory 14b such as a ROM or RAM for storing the programs and various data. The controller 14 functions as the "driving mode selection means", "engine control means", "lock-up clutch control means" and "gradient measurement means" of the "vehicle control system" of the present invention.

[0023] Specifically, the controller 14 mainly outputs control signals to the engine 2, the lockup clutch 4b, and the automatic transmission 6 based on detection signals from the above-mentioned driving mode selection switch SN1, the wheel speed sensor SN2, the acceleration sensor SN3, the steering angle sensor SN4, and the shift position sensor SN5, and controls them. For example, the controller 14 performs control to adjust the ignition timing, fuel injection timing, and fuel injection amount of the engine 2, control to switch the lockup clutch 4b between a plurality of states including an engaged state and a released state, and control to switch the gear stages of the automatic transmission 6. More specifically, for example, the controller 14 controls the ignition plug, fuel injection valve, throttle valve, etc. of the engine 2, controls an oil pump and a hydraulic control valve that supply hydraulic pressure to the lockup clutch 4b, and controls an oil pump and a hydraulic control valve that supply hydraulic pressure to the clutch and brake of the automatic transmission 6.

[0024] <Vehicle Control> Next, in the embodiment of the present invention, a description will be given of the control contents performed by the controller 14. In this embodiment, the controller 14 executes a vehicle control process that determines the idle speed of the engine 2 and permits or prohibits engagement of the lock-up clutch 4b.

[0025] First, the basic control of the lock-up clutch 4b will be described. The controller 14 appropriately switches the state of the lock-up clutch 4b between a plurality of states including an engaged state, a released state, and a slip state by controlling an oil pump that supplies hydraulic pressure to the lock-up clutch 4b and a hydraulic control valve. For example, the controller 14 controls the lock-up clutch 4b so that the lock-up clutch 4b is in an engaged state when the vehicle speed is equal to or higher than a predetermined value Vn, and the lock-up clutch 4b is in a released state when the vehicle speed is less than Vn. Alternatively, the state of the lock-up clutch 4b may be set based on the vehicle speed and the accelerator opening, or the state of the lock-up clutch 4b may be set based on a condition other than the vehicle speed.

[0026] Next, the vehicle control process according to the embodiment of the present invention will be specifically described with reference to Fig. 3 and Fig. 4. Fig. 3 is a flowchart of the vehicle control process according to the embodiment of the present invention, and Fig. 4 is an explanatory diagram showing the relationship between the road surface gradient and the engine correction speed. The vehicle control process is started when the ignition of the vehicle 1 is turned on and the power is supplied to the vehicle system, and is repeatedly executed by the controller 14 at a predetermined cycle.

[0027] 3 is started, in step S11, the controller 14 acquires various information about the vehicle 1, including information corresponding to detection signals from the driving mode selection switch SN1, the wheel speed sensor SN2, the acceleration sensor SN3, the steering angle sensor SN4, and the shift position sensor SN5. Then, the controller 14 proceeds to step S12.

[0028] In step S12, the controller 14 calculates the normal idle speed Rs based on the information acquired in step S11. The normal idle speed Rs is the idle speed in a normal situation where the controller 14 does not correct the idle speed based on the driving mode or road surface gradient in the vehicle control process. Specifically, the controller 14 refers to an idle speed map (created in advance and stored in the memory 14b or the like) that defines the relationship between the coolant temperature of the engine 2, the operating state of the air conditioner compressor of the vehicle 1, the power usage state of the vehicle 1, and the idle speed, and calculates the normal idle speed Rs that corresponds to various current states of the vehicle 1 based on the information acquired in step S11. For example, the normal idle speed Rs is about 800 rpm.

[0029] Next, in step S13, the controller 14 judges whether or not the off-road mode is selected as the driving mode based on the detection signal from the driving mode selection switch SN1. Specifically, if the driver operates the driving mode selection switch SN1 to select the off-road mode, it is judged that the off-road mode is selected (step S13: Yes), and if the driver selects a driving mode other than the off-road mode (e.g., the normal mode), it is judged that the off-road mode is not selected (step S13: No).

[0030] In step S13, if it is determined that the off-road mode is selected (step S13: Yes), the process proceeds to step S14, where the controller 14 acquires a correction rotation speed. The correction rotation speed is a correction value for correcting the idle rotation speed when the off-road mode is selected. For example, the controller 14 obtains an angle between a gravity vector and a longitudinal axis of the vehicle 1 based on signals input from the wheel speed sensor SN2 and the acceleration sensor SN3, and calculates a road surface gradient along the longitudinal direction of the vehicle 1 from this angle. Furthermore, the controller 14 identifies the traveling direction of the vehicle 1 (forward direction in the case of D range, backward direction in the case of R range, etc.) based on a signal input from the shift position sensor SN5. This makes it possible to identify whether the road surface gradient along the longitudinal direction of the vehicle 1 is an upward gradient or a downward gradient toward the traveling direction of the vehicle 1. Then, the controller 14 refers to a map (created in advance and stored in a memory, etc.) that specifies the relationship between the road surface gradient in the traveling direction of the vehicle 1 and the correction rotation speed, as shown in FIG. 4, and acquires a correction rotation speed corresponding to the road surface gradient calculated as above. The horizontal axis in the map of FIG. 4 indicates the road surface gradient [%] in the traveling direction of the vehicle 1, and is a positive value when the gradient is upward in the traveling direction of the vehicle 1 (forward when moving forward, backward when moving backward), and is a negative value when the gradient is downward. The vertical axis indicates the corrected rotation speed [rpm]. As shown in FIG. 4, when the road surface gradient is 0%, the corresponding corrected rotation speed is Rc0. This Rc0 can be set according to the torque characteristics of the engine 2, the weight of the vehicle 1, the tire grip force, etc., and is, for example, 50 rpm. When the road surface gradient in the longitudinal direction of the vehicle 1 is greater than 0%, the larger the road surface gradient, the larger the corrected rotation speed becomes until the road surface gradient reaches the threshold value m1. In other words, when the upward gradient in the traveling direction of the vehicle 1 is large, the corrected rotation speed is larger than when the upward gradient is small. Furthermore, when the road surface gradient is m1 or more, the corrected rotation speed is set to the maximum value Rc max The maximum value of this correction speed Rc maxcan be set according to the reliability and NVH performance requirements of the engine 2, and is, for example, 700 rpm. Furthermore, the road gradient threshold m1 can be set according to, for example, the torque characteristics of the engine 2, the weight of the vehicle 1, the grip of the tires, and the like, and m1 is, for example, 30%.

[0031] After step S14, the process proceeds to step S15, where the controller 14 determines whether or not the gear position of the automatic transmission 6 is first gear. For example, the controller 14 determines whether or not the current gear position of the automatic transmission 6 is first gear based on the state of an oil pump or a hydraulic control valve that supplies hydraulic pressure to the clutch or brake of the automatic transmission 6.

[0032] As a result, if the gear position of the automatic transmission 6 is first gear (step S15: Yes), the process proceeds to step S16, where the controller 14 prohibits the lock-up clutch 4b from entering an engaged state. In this case, the controller 14 controls the lock-up clutch 4b to maintain the released state even if a condition for engaging the lock-up clutch 4b (for example, vehicle speed equal to or greater than a predetermined value Vn) is satisfied.

[0033] On the other hand, if it is determined in step S14 that the off-road mode has not been selected (step S14: No), the process proceeds to step S17, where the controller 14 permits the lock-up clutch 4b to enter an engaged state. In this case, when a condition for engaging the lock-up clutch 4b (for example, when the vehicle speed is equal to or greater than a predetermined value Vn) is satisfied, the controller 14 controls the lock-up clutch 4b to enter the engaged state.

[0034] Furthermore, in step S15, if the gear position of the automatic transmission 6 is not first gear (step S15: No), the process proceeds to step S18, where the controller 14 determines whether the gear position of the automatic transmission 6 is second gear or not. As a result, if the gear position of the automatic transmission 6 is not second gear either (step S18: No), that is, if the gear position of the automatic transmission 6 is third gear or higher, the process proceeds to step S17, where the controller 14 permits the lock-up clutch 4b to enter an engaged state.

[0035] On the other hand, if the gear position of the automatic transmission 6 is second gear in step S18 (step S18: Yes), the process proceeds to step S19, where the controller 14 determines whether the vehicle speed is less than a predetermined vehicle speed Vs (e.g., 10 km / h). As a result, if the vehicle speed is less than the predetermined vehicle speed Vs (step S19: Yes), the process proceeds to step S16, where the controller 14 prohibits the lock-up clutch 4b from entering an engaged state. On the other hand, if the vehicle speed is not less than the predetermined vehicle speed Vs (i.e., the vehicle speed is equal to or greater than Vs) (step S19: No), the process proceeds to step S17, where the controller 14 permits the lock-up clutch 4b to enter an engaged state.

[0036] After step S16 or step S17, the process proceeds to step S20, where the controller 14 determines the required idle speed. The required idle speed is the engine speed that the engine 2 should maintain during idling. Specifically, if it is determined in step S13 that the off-road mode is not selected (step S13: No), the controller 14 sets the normal idle speed Rs calculated in step S12 as the required idle speed as is. That is, if the normal idle speed is 800 rpm, the required idle speed is also 800 rpm. On the other hand, if it is determined in step S13 that the off-road mode is selected (step S13: Yes) and the corrected speed is acquired in step S14, the value obtained by adding the corrected speed to the normal idle speed calculated in step S12 is set as the required idle speed. For example, if the normal idle speed is 800 rpm and the corrected speed is 300 rpm, the required idle speed is 800+300=1100 rpm. After step S20, the controller 14 ends the vehicle control process.

[0037] When the engine 2 is made to idle, the controller 14 controls the engine 2 so that the rotation speed of the engine 2 becomes the requested idle rotation speed determined in the latest vehicle control process. For example, if the requested idle rotation speed while the vehicle 1 is stopped is 800 rpm, and then the requested idle rotation speed becomes 1040 rpm after the vehicle 1 starts traveling, and the vehicle 1 is stopped again, the controller 14 controls the engine 2 so that the idle rotation speed is maintained at 1040 rpm after it has dropped to that speed. In other words, the controller 14 does not perform control such that the idle rotation speed is once lowered to 800 rpm and then raised to 1040 rpm.

[0038] <Action and effect> Next, the operation and effects of the vehicle control system according to the embodiment of the present invention will be described.

[0039] Fig. 5 shows an example of a time chart when vehicle control according to an embodiment of the present invention is executed. The time chart in Fig. 5 shows, from the top, the driving mode selected by the driving mode selection switch SN1 (normal mode / off-road mode), the gear stage of the automatic transmission 6, the vehicle speed [km / h], permission or prohibition of the engagement state of the lock-up clutch 4b, the road surface gradient [%] in the longitudinal direction of the vehicle 1, and the required idle speed [rpm].

[0040] In the example shown in Fig. 5, the normal idle speed is assumed to be Rs [rpm] over the entire period. However, the normal idle speed may be a value different from that shown in the example of Fig. 5, and may change over time.

[0041] First, in the period up to time t1 in Fig. 5, the normal mode is selected as the driving mode, and the road surface gradient in the vehicle width direction of the vehicle 1 is 0%. Therefore, the controller 14 sets the normal idle speed Rs as the requested idle speed. In addition, the controller 14 permits the engagement of the lock-up clutch 4b. However, since the vehicle speed is 0 km / h and is less than the predetermined value Vn, the controller 14 does not engage the lock-up clutch 4b, but keeps it in the released state.

[0042] At time t1, the driver operates the driving mode selection switch SN1, and the driving mode is switched from the normal mode to the off-road mode. At this time, the automatic transmission 6 is in the first gear. That is, since the off-road mode is selected and the gear is in the first gear, the controller 14 prohibits the lock-up clutch 4b from being engaged. Also, since the off-road mode is selected, the controller 14 obtains the correction speed and adds the correction speed to the normal idle speed Rs to set the requested idle speed. That is, the requested idle speed is made higher than that before time t1 when the normal mode was selected. In particular, since the road gradient at time t1 is 0%, the correction speed is Rc0. That is, the requested idle speed is Rs+Rc0.

[0043] After time t2, the vehicle speed starts to increase. However, the automatic transmission 6 remains in first gear until time t3, so the controller 14 maintains the prohibition of the engagement of the lock-up clutch 4b. In addition, the road gradient is 0% between times t2 and t3, so the correction rotation speed remains at Rc0.

[0044] At time t3, the gear stage of the automatic transmission 6 is shifted from 1st gear to 2nd gear. However, since the vehicle speed is less than Vs until time t4, the controller 14 maintains the prohibition of the engagement state of the lock-up clutch 4b. In addition, since the road surface gradient is 0% between times t3 and t4, the correction rotation speed remains at Rc0.

[0045] After time t4, the vehicle speed becomes equal to or higher than Vs. That is, the off-road mode is selected, the gear is second gear, and the vehicle speed is not less than Vs, so the controller 14 permits the lock-up clutch 4b to enter an engaged state. In this case, if the vehicle speed becomes equal to or higher than a predetermined value Vn and the engagement condition of the lock-up clutch 4b is satisfied, the controller 14 controls the lock-up clutch 4b to enter an engaged state. In addition, since the road gradient is 0% between times t4 and t5, the corrected rotation speed remains at Rc0.

[0046] After that, after time t5, the gear of the automatic transmission 6 is shifted to third gear. In other words, since the off-road mode is selected and the gear is third gear or higher, the controller 14 permits the lock-up clutch 4b to be engaged. Since the driving mode and gear do not change after time t5, the controller 14 maintains the permission of the lock-up clutch 4b to be engaged. In addition, since the road gradient is 0% between times t5 and t6, the corrected rotation speed remains at Rc0.

[0047] After time t6, the road gradient starts to increase. This means, for example, that the vehicle 1 approaches an uphill road and the gradient starts to increase in the traveling direction. Between times t6 and t7, the road gradient increases from 0% to m1. As the road gradient increases, the corrected rotation speed also increases. Therefore, the greater the road gradient, the greater the required idle rotation speed is set by the controller 14.

[0048] After that, after time t7, the driving mode is the off-road mode, and the road surface gradient is equal to or greater than the threshold value m1. Therefore, after time t7, the corrected rotation speed is set to the maximum value Rc max In this case, the controller 14 calculates the normal idle speed Rs+corrected speed Rc max is the required idle speed.

[0049] As described above, in this embodiment, when the off-road mode is selected by the driving mode selection switch SN1, the required idle speed is set higher than when the normal mode is selected, and the lock-up clutch 4b is prohibited from being engaged. In other words, in a situation where the driver recognizes that the vehicle is traveling on a bad road and is likely to depress the accelerator pedal deeply, and the drive wheels are likely to spin, the controller 14 sets the required idle speed higher and prevents the lock-up clutch 4b from being engaged. This makes it possible to increase the drive torque from the engine 2 during idling, so that the vehicle 1 can easily move forward without the driver having to depress the accelerator pedal deeply. In addition, even if the vehicle 1 shakes due to unevenness in the road surface and the driver depresses the accelerator pedal too much, the lock-up clutch 4b is released, so that the transmission of the drive torque to the drive wheels is mitigated, and the sudden acceleration of the vehicle 1 and the occurrence of shock can be suppressed. Therefore, it is possible to prevent the driver from depressing the accelerator pedal excessively, thereby suppressing the drive wheels from spinning, and also to suppress the sudden behavior of the vehicle 1 in response to the sudden operation of the accelerator pedal.

[0050] According to this embodiment, when the road surface gradient is an upward gradient greater than 0% toward the traveling direction of the vehicle 1 and the off-road mode is selected by the traveling mode selection switch SN1, the controller 14 sets the required idle speed higher than when the normal mode is selected or when the road surface gradient is 0% or less. That is, in a situation where the driver recognizes that the vehicle is traveling on a bad road and is likely to depress the accelerator pedal heavily, and further in a situation where the vehicle is traveling on an uphill road where the drive wheels are likely to spin, the controller 14 sets the required idle speed even higher. This makes it possible to increase the drive torque from the engine 2 during idling, so that the vehicle 1 can easily move forward without the driver having to depress the accelerator pedal heavily. Therefore, it is possible to prevent the driver from depressing the accelerator pedal excessively and suppress the drive wheels from spinning.

[0051] According to this embodiment, even if the off-road mode is selected by the driving mode selection switch SN1, the controller 14 allows the lock-up clutch 4b to be engaged when the automatic transmission 6 is in second gear or higher and the speed of the vehicle 1 is equal to or higher than the predetermined vehicle speed Vs, or when the gear is in third gear or higher. In other words, in a situation where the torque required to drive the drive wheels is relatively large, even if the vehicle 1 shakes due to unevenness of the road surface and the driver presses the accelerator pedal too hard, sudden acceleration or shock of the vehicle is unlikely to occur. Therefore, by allowing the lock-up clutch 4b to be engaged, the transmission efficiency of the torque converter 4 can be improved, and the fuel efficiency of the vehicle 1 can be improved. [Explanation of symbols]

[0052] 1 vehicle 2 Engine 4 Torque converter 4b Lock-up clutch 6. Automatic transmission 10 Front wheels (drive wheels) 14 Controller 14a Processor 14b Memory SN1 Driving mode selection switch SN2 Wheel Speed ​​Sensor SN3 Accelerometer SN4 Steering Angle Sensor SN5 Shift position sensor

Claims

1. A control system for a vehicle having an engine that supplies power for driving drive wheels, a torque converter that is provided on a power transmission path of the engine and has a lock-up clutch, and an automatic transmission that is connected to an output shaft of the torque converter and has three or more gear stages, a driving mode selection means for selecting one driving mode from a plurality of driving modes including a first driving mode for normal driving and a second driving mode for driving on rough roads in response to an operation by a driver of the vehicle; an engine control means for determining an idle speed of the engine and controlling the engine so that the engine speed becomes the idle speed during idling; and a lock-up clutch control means for controlling the lock-up clutch so as to be switchable between a plurality of states including an engaged state and a released state, When the second driving mode is selected by the driving mode selection means, the engine control means sets the idle speed higher than when the first driving mode is selected, The lock-up clutch control means prohibits the lock-up clutch from being engaged when the second driving mode is selected by the driving mode selection means, Even when the second driving mode is selected by the driving mode selection means, when the automatic transmission is in second gear and the speed of the vehicle is equal to or higher than a predetermined value, the lock-up clutch is permitted to be in an engaged state, Even when the second driving mode is selected by the driving mode selection means, when the automatic transmission is in a third gear or higher, the lock-up clutch is permitted to be in an engaged state regardless of the vehicle speed. A vehicle control system comprising:

2. A gradient measuring means for measuring a road gradient along a front-rear direction of the vehicle, when the road surface gradient measured by the gradient measuring means is an upward gradient greater than a predetermined value in the traveling direction of the vehicle and the second traveling mode is selected by the traveling mode selection means, the engine control means increases the idle speed compared to when the road surface gradient is equal to or less than the predetermined value and the second traveling mode is selected. The vehicle control system according to claim 1 .

3. A control system for a vehicle having an engine that supplies power for driving drive wheels, a torque converter that is provided on a power transmission path of the engine and has a lock-up clutch, and an automatic transmission that is connected to an output shaft of the torque converter and has three or more gear stages, a driving mode selection switch that accepts an operation for selecting one driving mode from a plurality of driving modes including a first driving mode for normal driving and a second driving mode for driving on rough roads; A memory for storing programs; A processor for executing the program, The processor, determining an idle speed of the engine, and controlling the engine so that the engine speed becomes the idle speed during idling; The lock-up clutch is controlled so as to be switchable between a plurality of states including an engaged state and a released state, When the second driving mode is selected by the driving mode selection switch, the idle speed is made higher than when the first driving mode is selected, and the lock-up clutch is prohibited from being engaged. Even when the second driving mode is selected by the driving mode selection switch, when the automatic transmission is in second gear and the vehicle speed is equal to or higher than a predetermined value, the lock-up clutch is permitted to be in an engaged state, Even when the second driving mode is selected by the driving mode selection switch, when the automatic transmission is in third gear or higher, the lock-up clutch is permitted to be engaged regardless of the vehicle speed. A vehicle control system comprising:

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