Vehicle control system

Abstract

To improve operability of a vehicle with an accelerator pedal by making a driver easily actually feel change of an acceleration of the vehicle according to stepping-back of the accelerator pedal.SOLUTION: A vehicle control system includes: an accelerator sensor detecting an accelerator opening; a target acceleration determination portion for determining a target acceleration of the vehicle on the basis of the detected accelerator opening; a target torque determination portion for determining a target torque of a driving source on the basis of the determined target acceleration; and a driving source control portion for controlling a driving source so that the determined target torque is generated. When the target acceleration in increasing the accelerator opening is regarded as a target acceleration in additional stepping, and the target acceleration in decreasing the accelerator opening is regarded as a target acceleration in stepping-back, the target acceleration determination portion determines the target acceleration so that the target acceleration in stepping-back becomes less than the target acceleration in additional stepping, under a condition that the accelerator openings are same.SELECTED DRAWING: Figure 15

Description

Technical Field

[0001] The present invention relates to a system for controlling a vehicle including a drive source that generates driving power for traveling and an accelerator pedal operated by a driver.

Background Art

[0002] Conventionally, a technique for controlling a drive source of a vehicle according to an operation of an accelerator pedal has been known. For example, Patent Document 1 below discloses a control device including an accelerator opening sensor that detects an opening degree of the accelerator pedal (accelerator opening), a target acceleration setting unit that sets a target acceleration of the vehicle based on the detected accelerator opening, and an engine control unit that controls the engine so that the set target acceleration is achieved.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1 described above, the target acceleration is set such that it increases as the accelerator opening increases. However, in the range where the accelerator opening is medium or more, there is a tendency for the slope (operation gain) of the change in the target acceleration with respect to the change in the accelerator opening to become smaller toward the high opening side. This is a natural characteristic considering the output limit of the drive source (engine), but depending on the situation, it can be a factor that gives the driver a sense of discomfort. For example, in a situation where the driver is stepping harder on the accelerator pedal, even if the operation gain decreases in the high opening range along the characteristics of the target acceleration described above, for the driver who feels the output limit of the drive source, such a decrease in the operation gain does not lead to a particular sense of discomfort. However, when the accelerator pedal is then released, if the target acceleration is changed along the same characteristics, there is a possibility that the decrease in the operation gain will give the driver a sense of discomfort. That is, there is a high possibility that the change (decrease) in acceleration remains at a level that is difficult for the driver to actually feel even though the accelerator pedal is being released, and this can give the driver a sense of discomfort (such as the feeling that the vehicle is accelerating on its own).

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a vehicle control system capable of making it easier for a driver to feel the change in the acceleration of a vehicle in response to the release of the accelerator pedal, thereby improving the operability of the vehicle by the accelerator pedal.

Means for Solving the Problem

[0006] As a solution to the above problems, the present invention is a system for controlling a vehicle including a drive source that generates driving power for traveling and an accelerator pedal operated by a driver, the system including: an accelerator sensor that detects an accelerator opening that is the opening degree of the accelerator pedal; a target acceleration setting unit that sets a target acceleration of the vehicle based on the accelerator opening detected by the accelerator sensor; a target torque setting unit that sets a target torque of the drive source based on the target acceleration set by the target acceleration setting unit; and a drive source control unit that controls the drive source to generate the target torque set by the target torque setting unit. The target acceleration setting unit sets the target acceleration based on the accelerator opening such that, in a predetermined opening range where the accelerator opening is higher than the opening at which the target acceleration becomes zero, the slope of the change in the target acceleration with respect to the change in the accelerator opening becomes smaller toward the high-opening side. When the target acceleration when the accelerator opening is increasing is defined as the target acceleration during stepping down and the target acceleration when the accelerator opening is decreasing is defined as the target acceleration during stepping back, the target acceleration setting unit sets the target acceleration such that, under the condition that the accelerator opening is the same within the predetermined opening range, the target acceleration during stepping back is smaller than the target acceleration during stepping down. That is, when the accelerator opening is the same under the condition of being lower than the predetermined opening range, the target acceleration during pedal release is set to be the same as the target acceleration during pedal depression. This is characterized by this (Claim 1).

[0007] According to the present invention, under the condition that the accelerator opening is the same, the target acceleration during stepping back, which is the target acceleration of the vehicle when the accelerator opening is decreasing, is set to be smaller than the target acceleration during stepping down, which is the target acceleration of the vehicle when the accelerator opening is increasing. Based on the target acceleration having such a hysteresis characteristic, the output torque of the drive source is controlled. Therefore, even when the target acceleration is set such that the operation gain of the accelerator pedal (the slope of the change in acceleration with respect to the change in the accelerator opening) becomes smaller toward the high-opening side, it is possible to make it easier for the driver to actually feel the change in the acceleration of the vehicle when the accelerator pedal is stepped back, and it is possible to improve the operability of the vehicle by the accelerator pedal.

[0008] When the rate of change of acceleration is defined as the jerk and the target value of the jerk is defined as the target jerk, it is preferable that the target acceleration setting unit calculates the target jerk from the rate of change of the accelerator opening degree and sets the target acceleration based on the integral value obtained by integrating the calculated target jerk (Claim 2).

[0009] In this way, when the target jerk is calculated from the rate of change of the accelerator opening degree, which is an index of the strength of the driver's acceleration intention, and the target acceleration is set based on the integral value obtained by integrating the calculated target jerk, it is possible to appropriately impart the above-described hysteresis characteristic (the characteristic that the target acceleration when stepping back is smaller than the target acceleration when stepping on more) while accelerating the vehicle in a manner faithful to the driver's intention.

[0010] In the above configuration, more preferably, the target acceleration setting unit sets an upper limit acceleration based on the accelerator opening degree and sets a lower limit acceleration that is smaller than the upper limit acceleration by a specific ratio. When the integral value of the target jerk is smaller than the upper limit acceleration and larger than the lower limit acceleration, the integral value is set as the target acceleration. When the integral value of the target jerk is equal to or greater than the upper limit acceleration, the upper limit acceleration is set as the target acceleration. When the integral value of the target jerk is equal to or less than the lower limit acceleration, the lower limit acceleration is set as the target acceleration (Claim 3).

[0011] According to this configuration, the difference between the target acceleration when stepping on more and the target acceleration when stepping back is appropriately limited, so it is possible to prevent the accelerator opening degree for obtaining the same acceleration from being significantly different when stepping on more and when stepping back. As a result, while optimizing the response feeling (the feeling of acceleration change) that the driver receives when stepping on the accelerator pedal more / stepping back, it is possible to reduce the sense of discomfort given to the driver by the difference in acceleration characteristics when stepping on more / stepping back.

[0012] In the above configuration, more preferably, when the accelerator opening is decreasing, the closer the most recently calculated target acceleration is to the lower limit acceleration, the closer the target jerk is brought to zero, and when the accelerator opening is increasing, the closer the most recently calculated target acceleration is to the upper limit acceleration, the closer the target jerk is brought to zero (Claim 4).

[0013] According to this configuration, when the target acceleration increases up to the upper limit acceleration due to stepping on the accelerator pedal more, or when the target acceleration decreases down to the lower limit acceleration due to stepping back the accelerator pedal, it is possible to prevent a sudden change in the operation gain of the accelerator pedal, and it is possible to ensure good ride comfort of the vehicle.

Effect of the Invention

[0016] As described above, according to the vehicle control system of the present invention, it is possible to make it easier for the driver to actually feel the change in the acceleration of the vehicle in response to stepping back the accelerator pedal, and thus improve the operability of the vehicle by the accelerator pedal.

Brief Description of the Drawings

[0017]

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Embodiments for Carrying Out the Invention

[0018] (1) Overall Configuration of the System FIG. 1 is a diagram for explaining a preferred embodiment of the present invention, and is a diagram schematically showing a specific example of a vehicle to which the vehicle control system of the present invention is applied. As shown in this figure, the vehicle includes an engine 1 mounted in an engine room ER, a transmission 101 connected to a crankshaft 20 which is an output shaft of the engine 1, a pair of drive shafts 102 connected to the transmission 101, and a pair of wheels 103 attached to outer ends in the vehicle width direction of each drive shaft 102. The rotation (output rotation) of the crankshaft 20 of the engine is transmitted to each drive shaft 102 and each wheel 103 after being shifted by the transmission 101. That is, the engine 1 mounted in the vehicle of the present embodiment is a power source for driving the vehicle, and rotationally drives the wheels 103 via the transmission 101 and the drive shafts 102.

[0019] The transmission 101 incorporates a gear mechanism 101A. The gear mechanism 101A is a mechanism capable of achieving a plurality of gear stages (for example, 1st speed to 6th speed) with different gear ratios, and interlocks and connects the crankshaft 20 (output shaft) of the engine 1 and the pair of drive shafts 102 to each other. The output rotation of the engine 1 is transmitted to each wheel 103 after being shifted at a gear ratio corresponding to the gear stage achieved by the gear mechanism 101A of the transmission 101. Here, the transmission 101 is a manual transmission (MT) that changes the gear stage in response to a manual operation by the driver. However, an automatic transmission (AT) that automatically changes the gear stage according to the driving conditions of the vehicle or the engine 1 may be used as the transmission 101.

[0020] FIG. 2 is a system diagram showing a schematic configuration of the engine 1. Here, the engine 1 is a four-cycle gasoline engine, and includes an engine body 10 that burns a mixture of fuel (gasoline) and air, an intake passage 30 through which air (intake air) introduced into the engine body 10 flows, and an exhaust passage 40 through which exhaust gas discharged from the engine body 10 flows.

[0021] The engine body 10 includes a housing (such as a cylinder block and a cylinder head) in which a plurality of cylinders 11 shown in FIG. 1 are formed inside, and pistons 21 reciprocally accommodated in the respective cylinders 11. Below the pistons 21, the above-described crankshaft 20 is disposed. The pistons 21 and the crankshaft 20 are connected via a connecting rod or the like so that the crankshaft 20 rotates as the pistons 21 reciprocate. A crank angle sensor SN1 for detecting the angle of the crankshaft 20 (crank angle) and the rotational speed of the crankshaft 20 (engine rotational speed) is provided at the lower part (cylinder block) of the engine body 10.

[0022] Above the pistons 21 of the respective cylinders 11, combustion chambers 12 are defined respectively. An intake port 13 and an exhaust port 14 are open in each combustion chamber 12. At the upper part (cylinder head) of the engine body 10, a combination of an injector 15, a spark plug 16, an intake valve 17, and an exhaust valve 18 is provided for each cylinder 11. The injector 15 is an injection valve that injects fuel (gasoline) into the combustion chamber 12. The spark plug 16 is a plug that ignites the air-fuel mixture in which the injected fuel and air are mixed. The intake valve 17 is a valve that opens and closes the intake port 13. The exhaust valve 18 is a valve that opens and closes the exhaust port 14. At the upper part of the engine body 10, a valve operating mechanism 19 for opening and closing the intake valve 17 and the exhaust valve 18 of each cylinder 11 in conjunction with the rotation of the crankshaft 20 is provided.

[0023] The intake passage 30 is connected to one side surface of the engine body 10 so as to communicate with the intake port 13 of each cylinder 11. In the intake passage 30, an air cleaner 31 for removing foreign substances in the intake air, an openable and closable throttle valve 32 for adjusting the intake air flow rate, and a surge tank 33 are provided in this order from the upstream side (the side far from the engine body 10). An air flow sensor SN2 for detecting the intake air flow rate is provided at a portion between the air cleaner 31 and the throttle valve 32 in the intake passage 30.

[0024] The exhaust passage 40 is connected to the other side surface of the engine body 10 so as to communicate with the exhaust ports 14 of the respective cylinders 11. A plurality of catalysts 41 for purifying harmful components in the exhaust gas are provided in the exhaust passage 40.

[0025] FIG. 3 is a functional block diagram showing the control system of the vehicle or the engine 1. As shown in FIG. 3 and FIGS. 1 and 2 above, the vehicle is provided with an accelerator pedal 60 operated by a driver who drives the vehicle, and an ECU 50 that controls the output of the engine 1 in response to the operation of the accelerator pedal 60 by the driver. Further, the vehicle is provided with an accelerator sensor SN3 that detects the opening degree of the accelerator pedal 60 (hereinafter referred to as the accelerator opening), a vehicle speed sensor SN4 that detects the traveling speed of the vehicle (hereinafter referred to as the vehicle speed), and a gradient sensor SN5 that detects the gradient of the road surface on which the vehicle is traveling (hereinafter referred to as the road surface gradient). Note that the gradient sensor SN5 may be a type of sensor that directly specifies the road surface gradient by detecting the inclination degree of the vehicle, or a type of sensor that indirectly specifies the road surface gradient from an estimation based on the detection result of detecting the acceleration of the vehicle or the like.

[0026] The ECU 50 is composed of a microcomputer including a processor (CPU) that performs calculations, a memory such as a ROM and a RAM, and various input / output buses. Detection information from various sensors is input to the ECU 50. For example, the ECU 50 is electrically connected to the above-described crank angle sensor SN1, air flow sensor SN2, accelerator sensor SN3, vehicle speed sensor SN4, and gradient sensor SN5, and various information detected by these sensors, that is, information such as the crank angle, engine rotation speed, intake air flow rate, accelerator opening, vehicle speed, and road surface gradient, is sequentially input to the ECU 50.

[0027] Based on the input information from each of the above sensors (such as SN1 to SN5), the ECU 50 controls each actuator of the engine while performing various determinations and calculations. For example, the ECU 50 is electrically connected to a plurality of actuators including the injector 15, the ignition plug 16, and the throttle valve 32, and appropriately outputs control signals based on the above determinations and calculations to each of these actuators.

[0028] As functional elements related to the above control, the ECU 50 has a target acceleration setting unit 51, a target torque setting unit 52, an engine control unit 53, and a gear stage estimation unit 54. The target acceleration setting unit 51 is a control module that sets the target acceleration of the vehicle based on various information including the accelerator opening detected by the accelerator sensor SN3. The target torque setting unit 52 is a control module that sets the target torque of the engine 1 (the target value of the rotational torque of the crankshaft 20) based on the target acceleration set by the target acceleration setting unit 51. The engine control unit 53 is a control module that controls the engine 1 so as to generate the target torque set by the target torque setting unit 52. The gear stage estimation unit 54 is a control module that estimates the gear stage of the transmission 101 from the relationship between the vehicle speed detected by the vehicle speed sensor SN4 and the engine rotational speed detected by the crank angle sensor SN1. Note that the engine control unit 53 corresponds to the "drive source control unit" in the present invention.

[0029] (2) Basic control Next, the basic control executed by the ECU 50 during the running of the vehicle will be described with reference to the flowchart of FIG. 4. When the control shown in FIG. 4 starts, the ECU 50 acquires various information representing the current state of the vehicle or the engine 1 (step S1). For example, the ECU 50 acquires the crank angle and the engine rotational speed detected by the crank angle sensor SN1, the intake air flow rate detected by the air flow sensor SN2, the accelerator opening detected by the accelerator sensor SN3, the vehicle speed detected by the vehicle speed sensor SN4, the road surface gradient detected by the gradient sensor SN5, and the gear stage of the transmission 101 estimated by the gear stage estimation unit 54, respectively.

[0030] Next, the target acceleration setting unit 51 of the ECU 50 sets the target acceleration Ac of the vehicle based on the information such as the accelerator opening acquired in the above step S1 (step S2). The details of the method for setting this target acceleration Ac will be described in item (3) below.

[0031] Next, the target torque setting unit 52 of the ECU 50 sets the target torque Tr, which is the output torque of the engine 1 required to achieve the target acceleration Ac set in the above step S3 (step S3). Specifically, the target torque setting unit 52 sets the target torque Tr of the engine 1 based on the target acceleration Ac set in the above step S2 and the vehicle speed acquired in the above step S1. The vehicle speed is considered in the setting of the target torque Tr because the higher the vehicle speed, the greater the running resistance of the vehicle. In other words, the target torque setting unit 52 estimates the current running resistance of the vehicle from the information such as the vehicle speed acquired in the above step S1, calculates the output torque of the engine 1 required to accelerate the vehicle at the target acceleration Ac against the estimated running resistance, and sets the calculated output torque as the above target torque Tr.

[0032] Next, the engine control unit 53 of the ECU 50 sets control target values for each actuator of the engine 1 to achieve the target torque Tr set in the above step S3 (step S4). For example, the engine control unit 53 sets target values of control amounts including the injection amount / injection timing of the injector 15, the ignition timing of the spark plug 16, and the opening degree of the throttle valve 32 so that a combustion force corresponding to the target torque Tr is generated in each cylinder 11 of the engine 1.

[0033] Next, the engine control unit 53 controls each actuator of the engine 1 in accordance with the control target value set in the above step S4 (step S5). For example, the engine control unit 53 controls the injector 15, the ignition plug 16, and the throttle valve 32 so that the control amounts of the injector 15, the ignition plug 16, and the throttle valve 32 match the control target values set in the above step S4. Thereby, an output torque equivalent to the target torque Tr set in the above step S3 is generated in the engine 1. This output torque accelerates the vehicle at an acceleration equivalent to the target acceleration Ac set in the above step S2.

[0034] (3) Basic flow of target acceleration setting Next, the control content of the above step S2 for setting the target acceleration Ac of the vehicle will be specifically described. FIG. 5 is a subroutine showing the details of the control in the above step S2. When the control shown in this figure starts, the target acceleration setting unit 51 of the ECU 50 calculates the upper limit acceleration Amax of the vehicle based on the accelerator opening, vehicle speed, and gear position acquired in the above step S1 (FIG. 4) (step S11). The upper limit acceleration Amax is the upper limit value of the target acceleration Ac of the vehicle and is a value that can be adopted when the driver performs an operation of stepping on the accelerator pedal 60 more (increasing the accelerator opening). Hereinafter, the information such as the accelerator opening acquired in the above step S1 may be referred to as the current accelerator opening, etc., but in any case, it means the latest information acquired within the currently ongoing processing routine, and the meaning is the same.

[0035] The upper limit acceleration Amax is determined according to an acceleration characteristic map that defines the relationship between the accelerator opening and the target acceleration (hereinafter also referred to as the acceleration characteristic) for each vehicle speed and gear position. FIG. 9 is a diagram showing an example of this acceleration characteristic map. FIG. 9 illustrates an acceleration characteristic map set when the transmission 101 is a six-speed forward transmission. Each of the graphs (a) and (b) shows the map when the vehicle speed is V1 and V2, respectively. In this example, it is assumed that the vehicle speed V2 is greater than the vehicle speed V1 (V2 > V1). The six characteristic lines Q1 to Q6 in each graph represent the acceleration characteristics at different gear positions. Q1 represents the acceleration characteristic at the first gear, Q2 represents the acceleration characteristic at the second gear, Q3 represents the acceleration characteristic at the third gear, Q4 represents the acceleration characteristic at the fourth gear, Q5 represents the acceleration characteristic at the fifth gear, and Q6 represents the acceleration characteristic at the sixth gear. In other words, FIG. 9(a) is a map that defines the acceleration characteristics at the vehicle speed V1 for each gear position (from the first gear to the sixth gear), and FIG. 9(b) is a map that defines the acceleration characteristics at the vehicle speed V2 (> V1) for each gear position. For the acceleration characteristics defined in any of the maps, the target acceleration is set to increase as the accelerator opening increases, and under the condition of the same accelerator opening (except when the accelerator opening is very small), the target acceleration is set to decrease as the gear position becomes higher. These acceleration characteristic maps are pre-stored in the storage medium in the ECU50 together with the maps for various vehicle speeds other than V1 and V2.

[0036] In the above step S11, the target acceleration setting unit 51 calculates the upper limit acceleration Amax by applying the accelerator opening, vehicle speed, and gear position obtained in the above step S1 to the acceleration characteristic map shown in FIG. 9. For example, when the current vehicle speed is V1 and the current gear position is the third gear, the target acceleration setting unit 51 calculates, as the upper limit acceleration Amax, the value on the characteristic line Q3 in the map of FIG. 9(a) corresponding to the current accelerator opening.

[0037] Next, the target acceleration setting unit 51 calculates a lower limit acceleration Amin of the vehicle based on the accelerator opening, vehicle speed, gear position, and road surface gradient acquired in the above step S1 (step S12). The lower limit acceleration Amin is the lower limit value of the target acceleration Ac of the vehicle and is a value that can be adopted when the driver performs an operation of stepping back the accelerator pedal 60 (decreasing the accelerator opening). Details of the method for calculating this lower limit acceleration Amin will be described in item (4) below.

[0038] Next, the target acceleration setting unit 51 calculates a target jerk Je of the vehicle based on the accelerator opening, vehicle speed, and gear position acquired in the above step S1 (step S13). In this specification, jerk means the change rate of acceleration (the value obtained by differentiating acceleration with respect to time), and the target jerk Je means the target value of the jerk. Details of the method for calculating this target jerk Je will be described in item (5) below.

[0039] Next, the target acceleration setting unit 51 calculates a target acceleration Ac of the vehicle based on the upper limit acceleration Amax, lower limit acceleration Amin, and target jerk Je calculated in the above steps S11 to S13 (step S14). Details of the method for calculating this target acceleration Ac will be described in item (6) below.

[0040] (4) Calculation flow of lower limit acceleration Next, the control content of the above step S12 for calculating the lower limit acceleration Amin of the vehicle will be specifically described. FIG. 6 is a subroutine showing the details of the control in the above step S12. When the control shown in this figure starts, the target acceleration setting unit 51 determines whether or not the accelerator opening acquired in the above step S1 is included in a predetermined hysteresis region Rh (step S21). The hysteresis region Rh is a region where a difference is provided between the lower limit acceleration Amin and the upper limit acceleration Amax, and is predetermined for each condition of vehicle speed and gear position.

[0041] Figure 10 is a graph showing an example of the hysteresis region Rh. The characteristic line Qx of the solid line in this Figure 10 is the characteristic of the target acceleration adapted to the current vehicle speed and gear position, and is selected from the map of Figure 9. For example, when the current vehicle speed is V1 and the current gear position is the third gear, the characteristic line Q3 in the map of Figure 9(a) is selected as the characteristic line Qx. As shown in Figure 10, the hysteresis region Rh is a region located between two boundary points X1 and X2 on the characteristic line Qx. In this hysteresis region Rh, the characteristic line Qx has a characteristic such that the slope (operation gain) of the change in the target acceleration with respect to the change in the accelerator opening becomes smaller on the high opening side. In other words, the hysteresis region Rh is set to include a curved portion that curves so as to draw a convex arc upward in the characteristic line Qx. Among the boundary points X1 and X2 of the hysteresis region Rh, if the boundary point X1 on the low opening side is the first boundary point and the boundary point X2 on the high opening side is the second boundary point, the first boundary point X1 is set at a position where the target acceleration is near zero, and the second boundary point X2 is set at a position where the accelerator opening is at a high opening (for example, around 90%) close to full opening. Hereinafter, the accelerator opening corresponding to the first boundary point X1 is referred to as the first opening Px1, and the accelerator opening corresponding to the second boundary point X2 is referred to as the second opening Px2.

[0042] In the above step S21, the target acceleration setting unit 51 compares the accelerator opening obtained in the above step S1 with the openings of the above-described first and second boundary points X1 and X2, that is, the first opening Px1 and the second opening Px2, and when it is confirmed that the accelerator opening is larger than the first opening Px1 and smaller than the second opening Px2, it is determined that the accelerator opening is included in the hysteresis region Rh.

[0043] When it is determined as NO in step S21 above and it is confirmed that the current accelerator opening is outside the hysteresis region Rh, the target acceleration setting unit 51 sets the same value as the upper limit acceleration Amax calculated in step S11 as the lower limit acceleration Amin (step S26). This means that the upper limit acceleration Amax calculated in step S11 (i.e., the value on the characteristic line Qx in FIG. 10) is set as the target acceleration Ac as it is. However, since the accelerator opening is outside the hysteresis region Rh, the target acceleration Ac set here is any value on the characteristic line Qx located outside the hysteresis region Rh.

[0044] On the other hand, when it is determined as YES in step S21 above and it is confirmed that the current accelerator opening is included in the hysteresis region Rh, the target acceleration setting unit 51 calculates a provisional lower limit acceleration Amin0 based on the accelerator opening acquired in step S1 above (step S22). Specifically, the target acceleration setting unit 51 calculates the value on the provisional lower limit line Qy0 shown in FIG. 10 as the provisional lower limit acceleration Amin0. The provisional lower limit line Qy0 is defined as a line linearly connecting the first boundary point X1, which is the boundary on the low opening side of the hysteresis region Rh, and the second boundary point X2, which is the boundary on the high opening side of the hysteresis region Rh. In step S22 above, the target acceleration setting unit 51 calculates, as the provisional lower limit acceleration Amin0, the value on this provisional lower limit line Qy0 corresponding to the current accelerator opening.

[0045] Next, the target acceleration setting unit 51 calculates a first internal division ratio α1 that defines the relationship among the lower limit acceleration Amin, the upper limit acceleration Amax, and the provisional lower limit acceleration Amin0 to be set, based on the vehicle speed and the gear position acquired in step S1 above (step S23). That is, the lower limit acceleration Amin is variably set between the upper limit acceleration Amax and the provisional lower limit acceleration Amin0. Therefore, in step S23, in order to determine how close the lower limit acceleration Amin should be set to the upper limit acceleration Amax or the provisional lower limit acceleration Amin0, the first internal division ratio α1 based on the vehicle speed and the gear position is calculated.

[0046] The first internal ratio α1 is variably set between 0 and 1. Specifically, the first internal ratio α1 is set to 0 when the lower limit acceleration Amin coincides with the upper limit acceleration Amax, and is set to 1 when the lower limit acceleration Amin coincides with the temporary lower limit acceleration Amin0. Also, when the lower limit acceleration Amin is smaller than the upper limit acceleration Amax and larger than the temporary lower limit acceleration Amin0, the first internal ratio α1 is set to an intermediate value between 0 and 1. In other words, the closer the first internal ratio α1 is to 0, the closer the lower limit acceleration Amin is set to a value close to the upper limit acceleration Amax (far from the temporary lower limit acceleration Amin0), and the closer the first internal ratio α1 is to 1, the closer the lower limit acceleration Amin is set to a value close to the temporary lower limit acceleration Amin0 (far from the upper limit acceleration Amax).

[0047] Next, the target acceleration setting unit 51 calculates a second internal ratio α2 based on the road surface gradient and the gear position acquired in the above step S1 (step S24). Similar to the first internal ratio α1 described above, the second internal ratio α2 is also a value that defines the relationship between the lower limit acceleration Amin to be set, the upper limit acceleration Amax, and the temporary lower limit acceleration Amin0, and is variably set between 0 and 1. The closer the second internal ratio α2 is to 0, the closer the lower limit acceleration Amin is set to a value close to the upper limit acceleration Amax (far from the temporary lower limit acceleration Amin0), and the closer the second internal ratio α2 is to 1, the closer the lower limit acceleration Amin is set to a value close to the temporary lower limit acceleration Amin0 (far from the upper limit acceleration Amax). However, the parameters for determining the second internal ratio α2 are the road surface gradient and the gear position, and in this sense, it is different from the first internal ratio α1 determined based on the vehicle speed and the gear position.

[0048] As shown in Fig. 11, the first internal ratio α1 and the second internal ratio α2 set in the above steps S23 and S24 are set to be smaller as any one of the vehicle speed, the gear position, and the road surface gradient is larger. This means that the higher the vehicle speed, the closer the lower limit acceleration Amin is set to a value close to the upper limit acceleration Amax, the higher the gear position, the closer the lower limit acceleration Amin is set to a value close to the upper limit acceleration Amax, and the larger the road surface gradient, the closer the lower limit acceleration Amin is set to a value close to the upper limit acceleration Amax. Here, the premise for treating the gradient of the uphill road as a positive gradient is assumed when it is said that "the road surface gradient is large". In other words, a large road surface gradient means that the traveling road of the vehicle is a relatively steep uphill road.

[0049] Next, the target acceleration setting unit 51 calculates the lower limit acceleration Amin of the vehicle based on the upper limit acceleration Amax calculated in the above step S11, the provisional lower limit acceleration Amin0 calculated in the above step S22, and the first internal ratio α1 and the second internal ratio α2 calculated in the above steps S23 and S24 (step S25). Specifically, the target acceleration setting unit 51 calculates the lower limit acceleration Amin using the following formula (1).

[0050] Amin = Amax - min[α1, max{(Amax - Ac’) / (Amax - Amin0), α2}] × (Amax - Amin0) ‥‥(1) Here, Ac’ is the previous target acceleration, that is, the target acceleration calculated by the immediately preceding processing routine that has already been completed.

[0051] According to the above formula (1), the lower limit acceleration Amin is calculated based on, in principle, the upper limit acceleration Amax, the provisional lower limit acceleration Amin0, and the smaller value of either the first internal ratio α1 or the second internal ratio α2. That is, the lower limit acceleration Amin is calculated by subtracting from the upper limit acceleration Amax a value obtained by multiplying the difference (Amax - Amin0) between the upper limit acceleration Amax and the provisional lower limit acceleration Amin0 by the smaller value of either the first internal ratio α1 or the second internal ratio α2. However, when the ratio (Amax - Ac’) / (Amax - Amin0) obtained by dividing the difference (Amax - Ac’) between the upper limit acceleration Amax and the previous target acceleration Ac by the difference (Amax - Amin0) between the upper limit acceleration Amax and the provisional lower limit acceleration Amin0 is greater than the second internal ratio α and smaller than the first internal ratio α1, this ratio is used instead of the above internal ratios α1 and α2.

[0052] Figure 12 is a diagram showing an example of the lower limit acceleration Amin calculated in step S25 above. In the example shown in this figure, the lower limit acceleration Amin is set on a lower limit line Qy located between a characteristic line Qx that defines the upper limit acceleration Amax and a provisional lower limit line Qy0 that defines the provisional lower limit acceleration Amin0. The lower limit line Qy is a line that divides the space between the characteristic line Qx and the provisional lower limit line Qy0 at a certain ratio, and the value on this lower limit line Qy corresponding to the current accelerator opening is calculated as the above lower limit acceleration Amin.

[0053] As shown in Figure 12, when the difference between the upper limit acceleration Amax and the lower limit acceleration Amin is defined as the up-down limit difference HA, this up-down limit difference HA becomes smaller the closer it is to the boundary (the first boundary point X1 or the second boundary point X2) of the hysteresis region Rh, and becomes larger towards the central side of the hysteresis region Rh. In other words, the up-down limit difference HA becomes zero when the accelerator opening is the boundary opening of the hysteresis region Rh, that is, the first opening Px1 or the second opening Px2, and is set to expand as the accelerator opening approaches the intermediate value between the first opening Px1 and the second opening Px2. In step S25 above, the target acceleration setting unit 51 sets the up-down limitThe lower limit acceleration Amin is set so that the differential HA changes in such a tendency.

[0054] (5) Calculation Flow of Target Jerk Next, the control content of step S13 for calculating the target jerk Je of the vehicle will be specifically described. FIG. 7 is a subroutine showing the details of the control of step S13. When the control shown in this figure starts, the target acceleration setting unit 51 calculates the throttle opening change rate ΔP which is the change rate of the throttle opening (step S31). The throttle opening change rate ΔP is a value obtained by differentiating the throttle opening with respect to time, and is calculated from, for example, the history of the throttle opening acquired over a recent predetermined period. In this case, the target acceleration setting unit 51 calculates the throttle opening change rate ΔP based on the changes in the data of a plurality of throttle openings including the throttle opening acquired in the currently ongoing processing routine (step S1 above) and the throttle opening acquired in the most recent completed processing routine. The throttle opening change rate ΔP is calculated as a positive value when the accelerator pedal 60 is being depressed further, and as a negative value when the accelerator pedal 60 is being depressed back. Hereinafter, the throttle opening change rate ΔP will be appropriately referred to as the accelerator pedal opening change rate ΔP.

[0055] Next, the target acceleration setting unit 51 calculates a basic jerk Je0 based on the accelerator pedal opening change rate ΔP calculated in step S31 and the vehicle speed and gear position acquired in step S1 (step S32). Specifically, the target acceleration setting unit 51 calculates the basic jerk Je0 by multiplying the coefficient obtained from the vehicle speed and gear position based on a predetermined map or the like by the accelerator pedal opening change rate ΔP. The coefficient used here (the coefficient to be multiplied by the accelerator pedal opening change rate ΔP) can be appropriately determined according to the vehicle speed and gear position, and is set, for example, to be smaller as the gear position is higher.

[0056] FIG. 13 is a graph showing the relationship between the accelerator opening change rate ΔP and the basic jerk Je0. As described above, since the basic jerk Je0 is a value obtained by multiplying the coefficient determined from the vehicle speed and the gear position by the accelerator opening change rate ΔP, this basic jerk Je0 changes in proportion to the accelerator opening change rate ΔP under the condition that the vehicle speed and the gear position are the same. That is, the basic jerk Je0 takes a positive value when the accelerator pedal 60 is depressed more (when ΔP is positive), and is calculated so as to increase to the positive side as the depression speed is faster. Conversely, the basic jerk Je0 takes a negative value when the accelerator pedal 60 is depressed back (when ΔP is negative), and is calculated so as to increase to the negative side as the depression-back speed is faster.

[0057] Next, the target acceleration setting unit 51 calculates a first correction coefficient k1 based on the accelerator opening change rate ΔP calculated in the above step S31 (step S33). For example, a map shown in FIG. 14 is applied to calculate this first correction coefficient k1. As a result, the first correction coefficient k1 is set to 0 when the accelerator opening change rate ΔP is greater than or equal to -p1 and less than or equal to +p1, and is set to 1 when the accelerator opening change rate ΔP is less than -p1 or greater than +p1. Note that p1 (absolute value) is set to a relatively small value. This is to avoid the change in the target acceleration from reaching even when the accelerator opening fluctuates slightly unintentionally due to vehicle vibration or the like.

[0058] Next, the target acceleration setting unit 51 calculates a previous internal division ratio α' based on the previous target acceleration Ac', the upper limit acceleration Amax calculated in step S11, and the lower limit acceleration Amin calculated in step S12 (step S34). The previous internal division ratio α' is a value that defines the relationship between the previous target acceleration Ac', which is the target acceleration calculated by the most recently completed processing routine, and the upper limit acceleration Amax and the lower limit acceleration Amin, and is variably set between 0 and 1. The closer the previous target acceleration Ac' is to the upper limit acceleration Amax (farther from the lower limit acceleration Amin), the closer the previous internal division ratio α' is set to a value close to 0, and the closer the previous target acceleration Ac' is to the lower limit acceleration Amin (farther from the upper limit acceleration Amax), the closer the previous internal division ratio α' is set to a value close to 1.

[0059] Next, the target acceleration setting unit 51 determines whether or not the accelerator opening change rate ΔP calculated in step S31 is greater than zero (step S35). The fact that the accelerator opening change rate ΔP is greater than zero means that the accelerator opening is increasing, that is, the accelerator pedal 60 is being depressed further. Conversely, the fact that the accelerator opening change rate ΔP is less than zero means that the accelerator opening is decreasing, that is, the accelerator pedal 60 is being released.

[0060] When it is determined as YES in step S35 and it is confirmed that the accelerator opening is increasing (the accelerator pedal 60 is being depressed further), the target acceleration setting unit 51 calculates a second correction coefficient k2 based on the accelerator opening acquired in step S1 and the previous internal division ratio α' calculated in step S34 (step S36). For example, the target acceleration setting unit 51 calculates the second correction coefficient k2 by applying the current accelerator opening and the previous internal division ratio α' to a predetermined map. The second correction coefficient k2 is set to be smaller as the accelerator opening is larger and smaller as the previous internal division ratio α' is smaller.

[0061] Next, the target acceleration setting unit 51 calculates the target jerk Je of the vehicle based on the basic jerk Je0 calculated in step S32, the first correction coefficient k1 calculated in step S33, and the second correction coefficient k2 calculated in step S36 (step S37). Specifically, the target acceleration setting unit 51 calculates the target jerk Je using the following formula (2).

[0062] Je = Je0 × k1 × k2 ··· (2) Here, as a prerequisite for reaching step S37, since the accelerator opening change rate ΔP is positive (YES in step S35), the basic jerk Je0 in formula (2) is positive. Also, as described above, the second correction coefficient k2 is a coefficient that becomes smaller as the previous interpolation ratio α' becomes smaller. Therefore, through the calculation of formula (2), the target jerk Je is calculated to be smaller as the previous interpolation ratio α' becomes smaller within a range greater than zero. This means that the closer the previous target acceleration Ac' is to the upper limit acceleration Amax, the smaller (closer to zero) the target jerk Je becomes.

[0063] Next, the control when it is determined NO in step S35, that is, when it is confirmed that the accelerator opening is decreasing (the accelerator pedal 60 is being released) or the accelerator opening is being held constant, will be described. In this case, the target acceleration setting unit 51 calculates a third correction coefficient k3 based on the accelerator opening and the gear position acquired in step S1 (step S39). For example, the target acceleration setting unit 51 calculates the third correction coefficient k3 by applying the current accelerator opening and the gear position to a predetermined map. The third correction coefficient k3 is set to become smaller as the accelerator opening becomes larger and to become smaller as the gear position becomes larger.

[0064] Next, the target acceleration setting unit 51 calculates a fourth correction coefficient k4 based on the gear position acquired in step S1 and the previous interpolation ratio α' calculated in step S34 (step S40). For example, the target acceleration setting unit 51 calculates the fourth correction coefficient k4 by applying the current gear position and the previous interpolation ratio α' to a predetermined map. The fourth correction coefficient k4 is set to be smaller as the gear position is larger and smaller as the previous interpolation ratio α' is larger.

[0065] Next, the target acceleration setting unit 51 calculates a target jerk Je of the vehicle based on the basic jerk Je0 calculated in step S32, the first correction coefficient k1 calculated in step S33, the third correction coefficient k3 calculated in step S39, and the fourth correction coefficient k4 calculated in step S40 (step S41). Specifically, the target acceleration setting unit 51 calculates the target jerk Je using the following formula (3).

[0066] Je = Je0 × k1 × k3 × k4 ··· (3) Here, as a prerequisite for reaching step S41, since the accelerator opening change rate ΔP is zero or negative (NO in step S35), the basic jerk Je0 in the above formula (3) is zero or negative. Also, as described above, the fourth correction coefficient k4 is a coefficient that becomes smaller as the previous interpolation ratio α' is larger. Therefore, by the calculation of the above formula (3), the target jerk Je is calculated such that its absolute value becomes smaller as the previous interpolation ratio α' is larger in the range of zero or less. This means that the absolute value of the target jerk Je becomes smaller (closer to zero) as the previous target acceleration Ac' is closer to the lower limit acceleration Amin.

[0067] (6) Calculation flow of target acceleration Next, the control content of the above step S14 for calculating the target acceleration Ac of the vehicle will be specifically described. FIG. 8 is a subroutine showing the details of the control of the above step S14. When the control shown in this figure starts, the target acceleration setting unit 51 calculates an integrated value Zj obtained by integrating the target jerk Je (step S51). The integrated value Zj is calculated, for example, by accumulating the target jerk Je calculated over a recent predetermined period. In this case, the target acceleration setting unit 51 accumulates data of a plurality of target jerks Je including the target jerk Je calculated in the currently ongoing processing routine (the above step S13) and the target jerk Je already calculated in the most recent completed processing routine to calculate the integrated value Zj.

[0068] Next, the target acceleration setting unit 51 determines whether the absolute value of the (current) target jerk Je calculated in the above step S13 is smaller than a predetermined threshold value β, that is, whether the relationship of -β < Je < β holds (step S52).

[0069] When it is determined as YES in the above step S52 and it is confirmed that the absolute value of the target jerk Je is smaller than the threshold value β, the target acceleration setting unit 51 calculates the target acceleration Ac based on the upper limit acceleration Amax calculated in the above step S11, the lower limit acceleration Amin calculated in the above step S12, and the previous interpolation ratio α' calculated in the above step S34 (step S53). Specifically, the target acceleration setting unit 51 calculates the target acceleration Ac using the following formula (4).

[0070] Ac = Amax - α' × (Amax - Amin) ··· (4) As shown in the above formula (4), in the above step S53, the target acceleration Ac is calculated using the same interpolation ratio as the previous time. That is, when the above step S53 is executed, the target acceleration Ac is maintained at a value that divides the upper limit acceleration Amax and the lower limit acceleration Amin at the same ratio.

[0071] On the other hand, when it is determined YES in the above step S52 and it is confirmed that the absolute value of the target jerk Je is equal to or greater than the threshold value β, the target acceleration setting unit 51 determines whether or not the integrated value Zj of the target jerk Je calculated in the above step S51 is equal to or greater than the upper limit acceleration Amax calculated in the above step S11 (step S54).

[0072] When it is determined YES in the above step S54 and it is confirmed that the integrated value Zj of the target jerk Je is equal to or greater than the upper limit acceleration Amax, the target acceleration setting unit 51 sets the upper limit acceleration Amax calculated in the above step S11 as the target acceleration Ac (step S55).

[0073] On the other hand, when it is determined NO in the above step S54 and it is confirmed that the integrated value Zj of the target jerk Je is smaller than the upper limit acceleration Amax, the target acceleration setting unit 51 determines whether or not the integrated value Zj of the target jerk Je calculated in the above step S51 is equal to or less than the lower limit acceleration Amin calculated in the above step S12 (step S56).

[0074] When it is determined YES in the above step S56 and it is confirmed that the integrated value Zj of the target jerk Je is equal to or less than the lower limit acceleration Amin, the target acceleration setting unit 51 sets the lower limit acceleration Amin calculated in the above step S12 as the target acceleration Ac (step S57).

[0075] On the other hand, when it is determined NO in the above step S56 and it is confirmed that the integrated value Zj of the target jerk Je is greater than the lower limit acceleration Amin, that is, when it is confirmed that the relationship Amin < Zj < Amax holds, the target acceleration setting unit 51 sets the integrated value Zj of the target jerk Je calculated in the above step S51 as the target acceleration Ac (step S58).

[0076] (7) Actions, etc. As described above, in the present embodiment, the target jerk Je, which is the target value of the vehicle's jerk (the rate of change of acceleration), is calculated each time from the accelerator opening change rate ΔP, and the target acceleration Ac of the vehicle is set based on the integrated value Zj, which is the value obtained by integrating the target jerk Je. Therefore, in the opening range where the operation gain of the accelerator pedal 60 (the slope of the change in acceleration with respect to the change in accelerator opening), that is, the hysteresis region Rh, where the operation gain becomes smaller toward the high opening side, the target acceleration Ac when the accelerator pedal 60 is released (hereinafter also referred to as the target acceleration at release) can be made smaller than the target acceleration Ac when the accelerator pedal 60 is depressed further (hereinafter also referred to as the target acceleration at further depression).

[0077] That is, the target jerk Je set according to (proportional to) the accelerator opening change rate ΔP is smaller when the accelerator opening decreases (ΔP becomes negative), i.e., when the pedal is released, than when the accelerator opening increases (ΔP becomes positive), i.e., when the pedal is depressed further. Therefore, the integrated value Zj obtained by integrating such a target jerk Je is smaller when the pedal is released than when the pedal is depressed further under the condition that the accelerator opening is the same. This means that the target acceleration Ac calculated based on the integrated value Zj becomes relatively smaller when the accelerator pedal 60 is released. As a result, in the hysteresis region Rh where the operation gain becomes smaller toward the high opening side, it is possible to make it easier for the driver to sense the change in the acceleration of the vehicle when the accelerator pedal 60 is released.

[0078] For example, in the above-mentioned hysteresis region Rh, the target acceleration is set such that the operation gain corresponding to the slope of the characteristic line Qx becomes smaller toward the high opening degree side. Therefore, if the target acceleration is uniformly set along the characteristic line Qx, there is a possibility that the driver may feel discomfort, especially when the accelerator pedal 60 is released. For example, in a situation where the driver is stepping harder on the accelerator pedal 60 within the hysteresis region Rh, even if the operation gain decreases in the high opening degree range along the characteristic line Qx, for a driver who senses the output limit of the engine, such a decrease in the operation gain does not lead to any particular discomfort. However, when the accelerator pedal is released later and the target acceleration is changed along the same characteristic line Qx, there is a possibility that the driver may feel discomfort due to the above-mentioned decrease in the operation gain. That is, although the accelerator pedal 60 is being released, the change (decrease) in acceleration may remain at a level that is difficult for the driver to actually feel, and this may give the driver a sense of discomfort (such as the feeling that the vehicle is accelerating on its own). In contrast, in the present embodiment, in the hysteresis region Rh, the target acceleration when releasing the pedal is made smaller than the target acceleration when stepping harder on the pedal. Therefore, it is possible to make the driver easily feel the change (behavior change) in the acceleration of the vehicle when the accelerator pedal 60 is released, and it is possible to improve the operability of the vehicle by the accelerator pedal 60.

[0079] Also, in the present embodiment, an upper limit acceleration Amax and a lower limit acceleration Amin are set based on a plurality of information including the accelerator opening (accelerator opening, vehicle speed, gear position, road surface gradient), and the integrated value Zj of the above-described target jerk Je is adopted as the target acceleration Ac only when the integrated value Zj falls between the upper and lower limit accelerations Amax and Amin. In other words, when the integrated value Zj is equal to or greater than the upper limit acceleration Amax, the upper limit acceleration Amax is adopted as the target acceleration Ac, and when the integrated value Zj is equal to or less than the lower limit acceleration Amin, the lower limit acceleration Amin is adopted as the target acceleration Ac. According to such a configuration, the difference between the target acceleration during acceleration and the target acceleration during deceleration is appropriately limited, so that it is possible to prevent the accelerator opening for obtaining the same acceleration from greatly differing between acceleration and deceleration. As a result, while giving the driver an appropriate response feeling (a feeling that the acceleration changes appropriately) when the accelerator pedal 60 is accelerated / decelerated, it is possible to reduce the discomfort given to the driver by the difference in the acceleration characteristics between acceleration / deceleration.

[0080] FIG. 15 is a diagram for specifically explaining the above-described effects, and shows the change in the target acceleration Ac when the driver once depresses the accelerator pedal 60 further and then releases it. In the example of FIG. 15, after the accelerator opening increases from P1 to P2 due to the further depression of the accelerator pedal 60, the accelerator opening decreases from P2 to P0 (<P1) due to the release of the accelerator pedal 60. Such a change in the accelerator opening causes the target acceleration Ac to change as Ac1 → Ac2 → Ac3 → Ac4. Ac1 is the target acceleration when the further depression of the accelerator pedal 60 starts, and is the intermediate value between the upper limit acceleration Amax and the lower limit acceleration Amin at the accelerator opening P1 at that time. Ac2 is the target acceleration when the further depression of the accelerator pedal 60 ends, and coincides with the upper limit acceleration Amax at the accelerator opening P2 at that time. Ac3 is the target acceleration when the accelerator pedal 60 is released until the accelerator opening decreases to P2, and is smaller than the target acceleration Ac1 at the start of the further depression (here, it almost coincides with the lower limit acceleration Amin at the accelerator opening P2). Ac4 is the target acceleration when the release of the accelerator pedal 60 ends, and coincides with the lower limit acceleration Amin at the accelerator opening P0 at that time.

[0081] In the above example, when comparing the target acceleration Ac in the same accelerator opening range from P1 to P2, the target acceleration during pedal release (thick dashed arrow), which is the target acceleration when the accelerator pedal 60 is being released, is smaller than the target acceleration during pedal depression (thick solid arrow), which is the target acceleration when the accelerator pedal 60 is being depressed further. By imparting such a hysteresis characteristic, in the present embodiment, compared to the case where there is no hysteresis characteristic, the change (decrease) in the acceleration of the vehicle due to the release of the accelerator pedal 60 becomes larger, and the driver can accurately feel the change in acceleration. As a result, an appropriate response feeling can be obtained when the accelerator pedal 60 is released, so that the operability of the vehicle by the accelerator pedal 60 can be improved. Further, since the target acceleration during pedal depression and the target acceleration during pedal release are set only between the characteristic line Qx that defines the upper limit acceleration Amax and the lower limit line Qy that defines the lower limit acceleration Amin, it is possible to prevent the difference between the target acceleration during pedal depression and the target acceleration during pedal release from expanding unreasonably, and the discomfort of the driver can be reduced.

[0082] Also, in the present embodiment, when calculating the target jerk Je from the accelerator opening change rate ΔP, the proximity of the previous (most recently calculated) target acceleration Ac' to the upper limit acceleration Amax or the lower limit acceleration Amin is considered. That is, when the accelerator pedal 60 is being depressed further (when ΔP > 0), the target jerk Je (>0) is calculated using the second correction coefficient k2 that becomes smaller as the previous target acceleration Ac' is closer to the upper limit acceleration Amax, and when the accelerator pedal 60 is being released (when ΔP < 0), the target jerk Je (<0) is calculated using the fourth correction coefficient k4 that becomes smaller as the previous target acceleration Ac' is closer to the lower limit acceleration Amin. According to such a configuration, when the target acceleration Ac increases to the upper limit acceleration Amax due to the depression of the accelerator pedal 60, or when the target acceleration Ac decreases to the lower limit acceleration Amin due to the release of the accelerator pedal 60, it is possible to prevent the operation gain of the accelerator pedal 60 (the slope of the change in acceleration with respect to the change in accelerator opening) from changing abruptly.

[0083] That is, as the target acceleration Ac approaches the upper limit acceleration Amax or the lower limit acceleration Amin, the absolute value of the target jerk Je is reduced, and this suppresses the change speed of the target acceleration Ac (= the integrated value Zj of the target jerk Je), so that the target acceleration Ac smoothly converges to the upper limit acceleration Amax or the lower limit acceleration Amin. For example, when the accelerator pedal 60 is depressed more, the target acceleration Ac gradually changes as shown by the thick solid line arrow Z1 in FIG. 16, and smoothly converges to the upper limit acceleration Amax. The thick dashed line arrow Z2 shows the change of the target acceleration Ac when the above-described control is not adopted. In this case, the operation gain suddenly changes when the upper limit acceleration Amax is reached. According to this embodiment in which such a situation can be avoided, the acceleration of the vehicle can be smoothly changed, and a good riding comfort can be ensured.

[0084] Further, in the present embodiment, since the target jerk Je is calculated using the first correction coefficient k1 that becomes zero when the accelerator opening change rate ΔP is within a predetermined range (-p1 or more and +p1 or less) including zero, it is possible to avoid the target acceleration Ac from changing even when the accelerator opening slightly fluctuates unintentionally due to vehicle vibration or the like, and it is possible to prevent the driver from feeling discomfort due to an unintended change in the behavior of the vehicle.

[0085] As described above, the preferred embodiments of the present invention have been described. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0086] For example, in the above embodiment, a gasoline engine, which is a spark ignition internal combustion engine, is used as the drive source of the vehicle. However, the drive source may be any device that can generate power for running. For example, a diesel engine may be used as the drive source. Further, the drive source is not limited to an internal combustion engine, and may be an electric motor.

Description of Reference Numerals

[0087] 1 Engine (drive source) 51 Target acceleration setting unit 52 Target torque setting unit 53 Engine control unit (drive source control unit) 60 Accelerator pedal Amax Upper limit acceleration Amin Lower limit acceleration SN3 Accelerator sensor

Claims

1. A system for controlling a vehicle comprising a drive source that generates driving power for traveling and an accelerator pedal operated by a driver, an accelerator sensor that detects an accelerator opening that is the opening of the accelerator pedal, a target acceleration setting unit that sets a target acceleration of the vehicle based on the accelerator opening detected by the accelerator sensor, a target torque setting unit that sets a target torque of the drive source based on the target acceleration set by the target acceleration setting unit, and a drive source control unit that controls the drive source to generate the target torque set by the target torque setting unit, the target acceleration setting unit sets the target acceleration based on the accelerator opening such that, in a predetermined opening range where the accelerator opening is higher than the opening at which the target acceleration becomes zero, the slope of the change in the target acceleration with respect to the change in the accelerator opening becomes smaller on the high-opening side, when the target acceleration when the accelerator opening is increasing is defined as the target acceleration during stepping down, and the target acceleration when the accelerator opening is decreasing is defined as the target acceleration during stepping back, the target acceleration setting unit sets the target acceleration such that, under the condition that the accelerator opening is the same within the predetermined opening range, the target acceleration during stepping back is smaller than the target acceleration during stepping down, and under the condition that the accelerator opening is the same on the lower-opening side than the predetermined opening range, the target acceleration during stepping back is set to be the same as the target acceleration during stepping down. A vehicle control system characterized by this.

2. In the vehicle control system according to Claim 1, when the rate of change of acceleration is defined as jerk and the target value of the jerk is defined as the target jerk, the target acceleration setting unit calculates the target jerk from the rate of change of the accelerator opening and sets the target acceleration based on the integrated value obtained by integrating the calculated target jerk. A vehicle control system characterized by this.

3. In the vehicle control system according to Claim 2, the target acceleration setting unit, Set an upper limit acceleration based on the accelerator opening, and set a lower limit acceleration that is smaller than the upper limit acceleration by a specific ratio. When the integrated value of the target jerk is smaller than the upper limit acceleration and larger than the lower limit acceleration, set the integrated value as the target acceleration. When the integrated value of the target jerk is greater than or equal to the upper limit acceleration, set the upper limit acceleration as the target acceleration. When the integrated value of the target jerk is less than or equal to the lower limit acceleration, set the lower limit acceleration as the target acceleration. A vehicle control system characterized by this.

4. In the vehicle control system according to claim 3. The target acceleration setting unit When the accelerator opening is decreasing, the closer the most recently calculated target acceleration is to the lower limit acceleration, the closer the target jerk is to zero. When the accelerator opening is increasing, the closer the most recently calculated target acceleration is to the upper limit acceleration, the closer the target jerk is to zero. A vehicle control system characterized by this.

Images