Vehicle control system

Abstract

To reduce discomfort of a driver, while applying hysteresis control capable of providing the driver operating an accelerator pedal with proper response feeling.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 additional stepping and the target acceleration in stepping-back are different from each other within a predetermined range of an upper limit acceleration or less and a lower limit acceleration or more 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 an 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 an 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 on the high-opening side. When the operation gain decreases on the high-opening side, there is a problem that it becomes difficult for the driver to feel the acceleration change (behavior change) of the vehicle, particularly in a situation where the driver depresses the accelerator pedal deeply and then slightly releases it. As a countermeasure against such a problem, it is proposed to adopt control that makes the target acceleration under the same condition of the accelerator opening different between when the accelerator pedal is depressed further and when it is released, that is, hysteresis control. However, if the difference in the acceleration characteristics between when the pedal is depressed further and when it is released is enlarged by the hysteresis control, there is a possibility that the driver's sense of discomfort will increase.

[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 reducing the driver's sense of discomfort while adopting hysteresis control that can give an appropriate response feeling to the driver who operates the accelerator pedal.

Means for Solving the Problems

[0006] As a means for solving the above problems, the present invention is a system for controlling a vehicle including a drive source that generates power for running and an accelerator pedal operated by a driver, the system including 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 so as to generate the target torque set by the target torque setting unit. The target acceleration setting unit As the opening degree at which the target acceleration approaches zero equal to or greater than a predetermined first opening and Predetermined as a high opening degree close to full openingWhen the accelerator opening is in the range of the second opening or less, based on the accelerator opening detected by the accelerator sensor, an upper limit acceleration which is the upper limit value of the target acceleration and a lower limit acceleration which is the lower limit value of the target acceleration are set. When the target acceleration when the accelerator opening is increasing is defined as the target acceleration during acceleration pedal depression and the target acceleration when the accelerator opening is decreasing is defined as the target acceleration during acceleration pedal release, the target acceleration setting unit sets the target acceleration such that, when the accelerator opening is in the range of the first opening or more and the second opening or less, under the condition that the accelerator opening is the same, the target acceleration during acceleration pedal depression and the target acceleration during acceleration pedal release are different from each other within the range of being less than or equal to the upper limit acceleration and greater than or equal to the lower limit acceleration. When the difference between the upper limit acceleration and the lower limit acceleration is defined as the upper and lower limit difference, the target acceleration setting unit sets the upper limit acceleration and the lower limit acceleration such that the upper and lower limit difference becomes zero when the accelerator opening is the first opening or the second opening, and the upper and lower limit difference expands as the accelerator opening approaches the intermediate value between the first opening and the second opening (Claim 1).

[0007] According to the present invention, the target acceleration during acceleration pedal depression which is the target acceleration of the vehicle when the accelerator opening is increasing and the target acceleration during acceleration pedal release which is the target acceleration of the vehicle when the accelerator opening is decreasing are set to be different from each other under the condition that the accelerator opening is the same. Further, based on the target acceleration having such a hysteresis characteristic, the output torque of the drive source is controlled. Therefore, an appropriate response feeling (a feeling that the acceleration changes appropriately) can be given to the driver when the accelerator pedal is depressed / released. Moreover, since the upper limit and the lower limit are given to the target acceleration in advance, the difference between the target acceleration during acceleration pedal depression and the target acceleration during acceleration pedal release is appropriately limited. Thus, it is possible to prevent the accelerator opening for obtaining the same acceleration from being significantly different between when the accelerator pedal is depressed and when it is released, and to reduce the sense of discomfort that such a difference may give to the driver.

[0009] Moreover, the control (hysteresis control) that makes the target acceleration during acceleration stepping different from the target acceleration during stepping back is executed in an accelerator opening range equal to or higher than a predetermined first opening degree and equal to or lower than a second opening degree. The upper and lower limit difference, which is the difference between the upper limit acceleration and the lower limit acceleration, becomes zero when the accelerator opening is the first opening degree or the second opening degree, and expands as the accelerator opening approaches the intermediate value between the first opening degree and the second opening degree. TherebyThe difference between the target acceleration when the accelerator pedal is depressed and the target acceleration when the accelerator pedal is released can be changed continuously within a specific range of accelerator pedal depression, and the target acceleration can be changed smoothly according to the accelerator pedal depression.

[0010] Preferably, the vehicle control system further includes a gradient sensor that detects a road gradient, which is a gradient of a road along which the vehicle runs, and the target acceleration setting unit sets the upper and lower limit accelerations so that the upper and lower limit difference decreases as the road gradient detected by the gradient sensor increases. ( Claim 2).

[0011] If the throttle opening required to drive a vehicle at a constant speed is taken as the equilibrium opening, then limit If the difference (the difference between the upper limit acceleration and the lower limit acceleration) is set to a uniform value regardless of the road gradient, the difference in the balanced opening degree when the accelerator pedal is depressed further / depressed back when the vehicle is traveling uphill will tend to increase. limit If the difference is reduced, the difference in equilibrium opening degree when the accelerator pedal is depressed further / depressed back when traveling uphill can be reduced, thereby reducing the discomfort that the driver may feel when traveling uphill and improving the operability of the accelerator pedal when traveling uphill.

[0012] Preferably, the upper limit acceleration is set along a characteristic line that is curved upwardly convexly in an accelerator opening range equal to or larger than the first opening and equal to or smaller than the second opening on a map having the accelerator opening as a horizontal axis and the target acceleration as a vertical axis, and the lower limit acceleration is set to a value between the upper limit acceleration and a provisional lower limit acceleration that is defined by a straight line connecting two points on the characteristic line corresponding to the first opening and the second opening. is limited (Claim 3).

[0013] According to this configuration, the lower limit acceleration is appropriately set It is possible. Effect of the Invention

[0014] As described above, according to the vehicle control system of the present invention, it is possible to reduce the discomfort of the driver while adopting the hysteresis control that can give an appropriate response feeling to the driver who operates the accelerator pedal.

Brief Description of the Drawings

[0015]

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Mode for Carrying Out the Invention

[0016] (1) Overall Configuration of the System FIG. 1 is a diagram for explaining a preferred embodiment of the present invention, and schematically shows 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.

[0017] 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 with 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.

[0018] Figure 2 is a system diagram showing the schematic configuration of the engine 1. The engine 1 is a four-cycle gasoline engine here, 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.

[0019] 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 a piston 21 reciprocally accommodated in each cylinder 11. Below the piston 21, the above-described crankshaft 20 is disposed. The piston 21 and the crankshaft 20 are connected via a connecting rod or the like so that the crankshaft 20 rotates as the piston 21 reciprocates. 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.

[0020] Above the piston 21 of each cylinder 11, a combustion chamber 12 is 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 mixture of the injected fuel and air. 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 is provided that opens and closes the intake valve 17 and the exhaust valve 18 of each cylinder 11 in conjunction with the rotation of the crankshaft 20.

[0021] The intake passage 30 is connected to one side surface of the engine body 10 so as to communicate with the intake ports 13 of the respective cylinders 11. In the intake passage 30, an air cleaner 31 for removing foreign matters in the intake air, an openable and closable throttle valve 32 for adjusting the flow rate of the intake air, 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 flow rate of the intake air is provided at a portion between the air cleaner 31 and the throttle valve 32 in the intake passage 30.

[0022] 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.

[0023] 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 according to the operation of the accelerator pedal 60 by the driver. Further, the vehicle is provided with an accelerator sensor SN3 for detecting the opening degree of the accelerator pedal 60 (hereinafter referred to as the accelerator opening degree), a vehicle speed sensor SN4 for detecting the traveling speed of the vehicle (hereinafter referred to as the vehicle speed), and a gradient sensor SN5 for detecting 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 degree of inclination of the vehicle, or may be 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.

[0024] The ECU 50 is composed of a microcomputer including a processor (CPU) that performs calculations, memories 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 crank angle, engine rotational speed, intake air flow rate, accelerator opening, vehicle speed, and road surface gradient, is sequentially input to the ECU 50 respectively.

[0025] Based on the input information from the above sensors (such as SN1 to SN5), the ECU 50 controls each actuator of the engine while executing various determinations and calculations. For example, the ECU 50 is electrically connected to a plurality of actuators including an injector 15, a spark plug 16, and a throttle valve 32, and appropriately outputs control signals based on the above determinations and calculations to these actuators.

[0026] 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 (target value of the rotational torque of the crankshaft 20) of the engine 1 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.

[0027] (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 engine 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 position of the transmission 101 estimated by the gear position estimation unit 54.

[0028] 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 step S1 above (step S2). The details of the method for setting this target acceleration Ac will be described in item (3) below.

[0029] 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 step S2 above (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 step S2 above and the vehicle speed acquired in step S1 above. 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 step S1 above, 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 target torque Tr.

[0030] 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 step S3 above (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 combustion force corresponding to the target torque Tr is generated in each cylinder 11 of the engine 1.

[0031] Next, the engine control unit 53 controls each actuator of the engine 1 according to the control target values set in step S4 above (step S5). For example, the engine control unit 53 controls the injector 15, the spark plug 16, and the throttle valve 32 so that the control amounts of the injector 15, the spark plug 16, and the throttle valve 32 match the control target values set in step S4 above. As a result, an output torque equivalent to the target torque Tr set in step S3 above is generated in the engine 1. This output torque accelerates the vehicle at an acceleration equivalent to the target acceleration Ac set in step S2 above.

[0032] (3) Basic flow of target acceleration setting Next, the control content of 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 step S2 above. 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 step S1 (FIG. 4) above (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 step S1 above 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.

[0033] 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, and 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 in the first gear, Q2 represents the acceleration characteristic in the second gear, Q3 represents the acceleration characteristic in the third gear, Q4 represents the acceleration characteristic in the fourth gear, Q5 represents the acceleration characteristic in the fifth gear, and Q6 represents the acceleration characteristic in the sixth gear. In other words, FIG. 9(a) is a map that defines the acceleration characteristics for each gear position (from the first gear to the sixth gear) when the vehicle speed is V1, and FIG. 9(b) is a map that defines the acceleration characteristics for each gear position when the vehicle speed is V2 (> V1). 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 that the accelerator opening is the same (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 stored in advance in the storage medium in the ECU50 together with the maps for various vehicle speeds other than V1 and V2.

[0034] 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.

[0035] 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 step S1 above (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.

[0036] 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 step S1 above (step S13). In this specification, jerk means the rate of change 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.

[0037] 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 steps S11 to S13 above (step S14). Details of the method for calculating this target acceleration Ac will be described in item (6) below.

[0038] (4) Calculation flow of lower limit acceleration Next, the control content of 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 step S12 above. When the control shown in this figure starts, the target acceleration setting unit 51 determines whether or not the accelerator opening acquired in step S1 above is included in a predetermined hysteresis region Rh (step S21). The hysteresis region Rh is a region in which 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.

[0039] FIG. 10 is a graph showing an example of the hysteresis region Rh. The characteristic line Qx of the solid line in FIG. 10 is the characteristic of the target acceleration adapted to the current vehicle speed and gear position, and is selected from the map of FIG. 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 FIG. 9(a) is selected as the characteristic line Qx. As shown in FIG. 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 among 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. In the following, 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.

[0040] In step S21, the target acceleration setting unit 51 compares the accelerator opening obtained in step S1 with the respective openings of the first and second boundary points X1 and X2 described above, 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.

[0041] When it is determined as NO in the above step S21 and it is confirmed that the current accelerator opening degree is outside the hysteresis region Rh, the target acceleration setting unit 51 sets the same value as the upper limit acceleration Amax calculated in the above step S11 as the lower limit acceleration Amin (step S26). This means that the upper limit acceleration Amax calculated in the above step S11 (that is, 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 degree 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.

[0042] On the other hand, when it is determined as YES in the above step S21 and it is confirmed that the accelerator opening degree 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 degree acquired in the above step S1 (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 degree side of the hysteresis region Rh, and the second boundary point X2, which is the boundary on the high opening degree side of the hysteresis region Rh. In the above step S22, the target acceleration setting unit 51 calculates the value on this provisional lower limit line Qy0 corresponding to the current accelerator opening degree as the provisional lower limit acceleration Amin0.

[0043] 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 the above step S1 (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 to what extent the lower limit acceleration Amin is set to a value close 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.

[0044] 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 is equal to the upper limit acceleration Amax, and is set to 1 when the lower limit acceleration Amin is equal to 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).

[0045] Next, the target acceleration setting unit 51 calculates a second internal ratio α2 based on the road surface gradient and the gear position obtained 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 that determine 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.

[0046] 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 as the vehicle speed is higher, the lower limit acceleration Amin is set to a value closer to the upper limit acceleration Amax, as the gear position is higher, the lower limit acceleration Amin is set to a value closer to the upper limit acceleration Amax, and as the road surface gradient is larger, the lower limit acceleration Amin is set to a value closer to the upper limit acceleration Amax. Here, the so-called "large road surface gradient" assumes that the gradient of the uphill road is treated as a positive gradient. In other words, a large road surface gradient means that the traveling road of the vehicle is a relatively steep uphill road.

[0047] 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).

[0048] 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 most recent processing routine that has already been completed.

[0049] 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.

[0050] FIG. 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.

[0051] As shown in FIG. 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 as it approaches the boundary (the first boundary point X1 or the second boundary point X2) of the hysteresis region Rh, and becomes larger toward the center 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 performs the up-down limitThe lower limit acceleration Amin is set so that the differential HA changes in such a tendency.

[0052] (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 in step S13. When the control shown in this figure starts, the target acceleration setting unit 51 calculates the opening change rate ΔP which is the change rate of the accelerator opening (step S31). The opening change rate ΔP is a value obtained by differentiating the accelerator opening with respect to time, and is calculated, for example, from the history of the accelerator opening acquired over a recent predetermined period. In this case, the target acceleration setting unit 51 calculates the opening change rate ΔP based on the changes in the data of a plurality of accelerator openings including the accelerator opening acquired in the currently ongoing processing routine (step S1 above) and the accelerator opening acquired in the most recent completed processing routine. The 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 opening change rate ΔP will be appropriately referred to as the accelerator opening change rate ΔP.

[0053] Next, the target acceleration setting unit 51 calculates a basic jerk Je0 based on the accelerator 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 opening change rate ΔP. The coefficient used here (the coefficient to be multiplied by the accelerator 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.

[0054] 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 same conditions of vehicle speed and gear position. That is, the basic jerk Je0 takes a positive value when the accelerator pedal 60 is being depressed further (when ΔP is positive), and is calculated to increase more on the positive side as the rate of further depression is faster. Conversely, the basic jerk Je0 takes a negative value when the accelerator pedal 60 is being depressed back (when ΔP is negative), and is calculated to increase more on the negative side as the rate of depression back is faster.

[0055] Next, the target acceleration setting unit 51 calculates a first correction coefficient k1 based on the accelerator opening change rate ΔP calculated in 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.

[0056] Next, the target acceleration setting unit 51 calculates a previous interpolation 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 interpolation ratio α' is a value that defines the relationship between the previous target acceleration Ac', which is the target acceleration calculated by the most recent processing routine that has already been completed, 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 interpolation 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 interpolation ratio α' is set to a value close to 1.

[0057] Next, the target acceleration setting unit 51 determines whether 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.

[0058] 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 interpolation 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 interpolation 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 interpolation ratio α' is smaller.

[0059] Next, the target acceleration setting unit 51 calculates the target jerk Je of the vehicle based on the basic jerk Je0 calculated in the above step S32, the first correction coefficient k1 calculated in the above step S33, and the second correction coefficient k2 calculated in the above step S36 (step S37). Specifically, the target acceleration setting unit 51 calculates the target jerk Je using the following formula (2).

[0060] Je = Je0 × k1 × k2 ··· (2) Here, as a prerequisite for reaching the step S37, since the acceleration pedal opening change rate ΔP is positive (YES in step S35), the basic jerk Je0 in the above 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, by the calculation of the above 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 target jerk Je becomes smaller (closer to zero) as the previous target acceleration Ac' approaches the upper limit acceleration Amax.

[0061] Next, the control when it is determined as NO in the above step S35, that is, when it is confirmed that the acceleration pedal opening is decreasing (the accelerator pedal 60 is being depressed backward) or the acceleration pedal 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 acceleration pedal opening and the gear position acquired in the above step S1 (step S39). For example, the target acceleration setting unit 51 calculates the third correction coefficient k3 by applying the current acceleration pedal opening and the gear position to a predetermined map. The third correction coefficient k3 is set to become smaller as the acceleration pedal opening becomes larger and to become smaller as the gear position becomes larger.

[0062] Next, the target acceleration setting unit 51 calculates a fourth correction coefficient k4 based on the gear position acquired in the above step S1 and the previous interpolation ratio α' calculated in the above 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.

[0063] Next, the target acceleration setting unit 51 calculates the target jerk Je of the vehicle based on the basic jerk Je0 calculated in the above step S32, the first correction coefficient k1 calculated in the above step S33, the third correction coefficient k3 calculated in the above step S39, and the fourth correction coefficient k4 calculated in the above step S40 (step S41). Specifically, the target acceleration setting unit 51 calculates the target jerk Je using the following formula (3).

[0064] Je = Je0 × k1 × k3 × k4 ··· (3) Here, as a prerequisite for reaching the 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.

[0065] (6) Calculation flow of target acceleration Next, the control content of 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 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 (step S13) and the target jerk Je already calculated in the most recent completed processing routine to calculate the integrated value Zj.

[0066] Next, the target acceleration setting unit 51 determines whether the absolute value of the (current) target jerk Je calculated in step S13 is less than a predetermined threshold value β, that is, whether the relationship -β < Je < β holds (step S52).

[0067] If it is determined as YES in step S52 and it is confirmed that the absolute value of the target jerk Je is less 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 step S11, the lower limit acceleration Amin calculated in step S12, and the previous interpolation ratio α' calculated in step S34 (step S53). Specifically, the target acceleration setting unit 51 calculates the target acceleration Ac using the following formula (4).

[0068] Ac = Amax - α'×(Amax - Amin) ··· (4) As shown in the above formula (4), in step S53, the target acceleration Ac is calculated using the same interpolation ratio as the previous time. That is, when 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.

[0069] On the other hand, 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 equal to or greater than the threshold value β, the target acceleration setting unit 51 determines whether or not the integral 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).

[0070] When it is determined as YES in the above step S54 and it is confirmed that the integral 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).

[0071] On the other hand, when it is determined as NO in the above step S54 and it is confirmed that the integral 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 integral 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).

[0072] When it is determined as YES in the above step S56 and it is confirmed that the integral 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).

[0073] On the other hand, when it is determined as NO in the above step S56 and it is confirmed that the integral 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 integral value Zj of the target jerk Je calculated in the above step S51 as the target acceleration Ac (step S58).

[0074] (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 hysteresis region Rh where the operation gain of the accelerator pedal 60 (the slope of the change in acceleration with respect to the change in accelerator opening) 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).

[0075] 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) during release than when the accelerator opening increases (ΔP becomes positive) during further depression. Therefore, the integrated value Zj obtained by integrating such a target jerk Je is smaller during release than during further depression 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 actually feel the change in the acceleration of the vehicle when the accelerator pedal 60 is released.

[0076] For example, in the above-described 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 risk that the driver may feel discomfort, especially when the accelerator pedal 60 is released. For example, in a situation where the driver is pressing down 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 risk that the driver may feel discomfort due to the above-described decrease in the operation gain. That is, there is a high possibility that the change (decrease) in acceleration remains at a level where it is difficult for the driver to actually feel it despite the accelerator pedal 60 being released, 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 released is made smaller than the target acceleration when pressing down harder, so it is possible to make the driver more likely to actually feel the change (behavior change) in the vehicle's acceleration when the accelerator pedal 60 is released, and it is possible to improve the operability of the vehicle with the accelerator pedal 60.

[0077] In addition, in the present embodiment, the upper limit acceleration Amax and the 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 integral value Zj of the above-described target jerk Je is within the upper and lower limit accelerations Amax and Amin. Only in this case is the integral value Zj adopted as the target acceleration Ac. In other words, when the integral value Zj is greater than or equal to the upper limit acceleration Amax, the upper limit acceleration Amax is adopted as the target acceleration Ac, and when the integral value Zj is less than or equal to 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 being significantly different 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 and deceleration.

[0078] FIG. 15 is a diagram for specifically explaining the above-described effects, and shows changes in the target acceleration Ac when the driver once depresses the accelerator pedal 60 more 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 changes the target acceleration Ac as Ac1 → Ac2 → Ac3 → Ac4. Ac1 is the target acceleration when the further depression of the accelerator pedal 60 is started, 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.

[0079] In the above example, when comparing the target accelerations Ac in the same accelerator opening range from P1 to P2, the target acceleration when the accelerator pedal 60 is released (thick dashed arrow) is smaller than the target acceleration when the accelerator pedal 60 is further depressed (thick solid arrow). By providing such a hysteresis characteristic, in this embodiment, the change (decrease) in the acceleration of the vehicle due to the release of the accelerator pedal 60 is larger than if there was no hysteresis characteristic, and the driver can accurately feel the change in acceleration. As a result, an appropriate response feeling is obtained when the accelerator pedal 60 is released, and the operability of the vehicle by the accelerator pedal 60 can be improved. In addition, the target acceleration when depressing the pedal and the target acceleration when depressing the pedal are set only between the characteristic line Qx that specifies the upper limit acceleration Amax and the lower limit line Qy that specifies the lower limit acceleration Amin, so that it is possible to prevent the difference between the target acceleration when depressing the pedal and the target acceleration when depressing the pedal from increasing unnecessarily, thereby reducing the sense of discomfort felt by the driver.

[0080] In this embodiment, in the hysteresis region Rh where the accelerator opening is equal to or larger than the first opening Px1 and equal to or smaller than the second opening Px2, the difference between the upper limit acceleration Amax and the lower limit acceleration Amin becomes smaller toward the center of the hysteresis region Rh. limit That is, the upper limit acceleration Amax and the lower limit acceleration Amin are set so that ... limit The higher the difference HA becomes zero and the closer the accelerator opening becomes to the midpoint between the first opening Px1 and the second opening Px2, the lower the limit With this configuration, the difference between the target acceleration when the accelerator pedal is depressed and the target acceleration when the accelerator pedal is released can be changed continuously within the hysteresis region Rh, and the target acceleration can be changed smoothly according to the accelerator pedal opening.

[0081] Further, in the present embodiment, when calculating the lower limit acceleration Amin, by applying the second internal division ratio α2 that becomes smaller as the road surface gradient (uphill gradient) increases, the vertical limit difference HA is set to decrease (the lower limit acceleration Amin approaches the upper limit acceleration Amax), so that it is possible to avoid variations in the opening required to drive the vehicle at a constant speed (hereinafter referred to as the balance opening) during uphill driving, and improve the operability of the accelerator pedal 60 during uphill driving.

[0082] FIG. 16 is a graph showing the acceleration characteristics (relationship between the accelerator opening and the target acceleration) during uphill driving. In this figure, lines L0 and L1 represent the constant acceleration lines (zero acceleration lines) where the acceleration becomes zero. L0 is for driving on a flat road with a zero gradient, and L1 is for driving on an uphill road with a positive gradient. The zero acceleration line L1 during uphill driving shifts upward from the zero acceleration line L0 during flat road driving. The shifted line L1 is positioned at a height that crosses the characteristic line within the hysteresis region Rh. As a result, the accelerator opening, that is, the balance opening required to drive the vehicle at a constant speed (zero acceleration), becomes different between when the accelerator pedal 60 is depressed further and when it is released. The difference in the balance opening between when it is depressed further / when it is released increases as the road surface gradient increases from zero (as the line L1 moves away from the line L0), but especially the vertical limitWhen the differential HA is set uniformly regardless of the road surface gradient, this tendency becomes prominent. For example, assuming that the lower limit line Qy defining the lower limit acceleration Amin is fixed by a line Qy2 (the same as the provisional lower limit line Qy0 in Fig. 10) that linearly connects the boundary points X1 and X2 of the hysteresis region Rh, the difference in the equilibrium opening during stepping-up / stepping-back may be up to HP2 at maximum. That is, when adopting a uniform lower limit line Qy2 independent of the road surface gradient, the difference in the equilibrium opening during stepping-up / stepping-back may expand up to HP2 (=P12 - P10), which is the difference between the opening P10 on the characteristic line Qx defining the upper limit acceleration Amax and the opening P12 on the above lower limit line Qy2. On the other hand, when setting the lower limit acceleration Amin by the method of this embodiment, that is, when adopting a lower limit line Qy1 that approaches the characteristic line Qx as the road surface gradient increases and setting the lower limit acceleration Amin on the lower limit line Qy1, the difference in the equilibrium opening during stepping-up / stepping-back expands only up to HP1 at maximum. That is, HP1 (=P11 - P10), which is the difference between the opening P10 on the characteristic line Qx and the opening P11 on the lower limit line Qy1, becomes the maximum value of the difference in the equilibrium opening during stepping-up / stepping-back, and this value is smaller than the maximum difference HP2 in the above-described case (when setting the lower limit acceleration Amin regardless of the road surface gradient).

[0083] Thus, in this embodiment, the difference in the equilibrium opening during stepping-up / stepping-back that may occur during uphill driving can be reduced, so that the discomfort that can be given to the driver during uphill driving can be alleviated, and the operability of the accelerator pedal 60 during uphill driving can be improved.

[0084] Further, in the present embodiment, when the absolute value of the target jerk Je is equal to or less than a predetermined threshold value β, in other words, when the acceleration pedal opening change rate ΔP is within a predetermined range including zero, the internal division ratio of the target acceleration Ac with respect to the upper limit acceleration Amax and the lower limit acceleration Amin is maintained at the same value as the previous time (previous internal division ratio α'), so that the acceleration of the vehicle can be gently changed along with the driver's intention. That is, the small absolute value of the acceleration pedal opening change rate ΔP indicates the driver's intention to gently change the acceleration of the vehicle. In the present embodiment, in such a case, the target acceleration Ac is set according to the same internal division ratio as the previous time, so that a sudden change in the acceleration of the vehicle can be avoided, and the driver can be prevented 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 driving 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 an electric motor may also be used.

Explanation 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 HA Up and down limit Difference Px1 First opening Px2 Second opening SN3 Accelerator sensor SN5 Gradient 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 which 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, When the target acceleration setting unit is in an accelerator opening range that is equal to or greater than a first opening degree predetermined as an opening degree at which the target acceleration becomes near zero and equal to or less than a second opening degree predetermined as a high opening degree close to full opening, based on the accelerator opening detected by the accelerator sensor, an upper limit acceleration that is an upper limit value of the target acceleration and a lower limit acceleration that is a lower limit value of the target acceleration are set, When the target acceleration when the accelerator opening is increasing is defined as the target acceleration when stepping on more, and the target acceleration when the accelerator opening is decreasing is defined as the target acceleration when stepping back, the target acceleration setting unit, when in the accelerator opening range that is equal to or greater than the first opening degree and equal to or less than the second opening degree, sets the target acceleration so that the target acceleration when stepping on more and the target acceleration when stepping back are different from each other within a range that is equal to or less than the upper limit acceleration and equal to or greater than the lower limit acceleration under the condition that the accelerator opening is the same, When the difference between the upper limit acceleration and the lower limit acceleration is defined as the upper and lower limit difference, the target acceleration setting unit sets the upper limit acceleration and the lower limit acceleration such that the upper and lower limit difference becomes zero when the accelerator opening is the first opening degree or the second opening degree, and the upper and lower limit difference expands as the accelerator opening approaches the intermediate value between the first opening degree and the second opening degree. A vehicle control system characterized by this.

2. In the vehicle control system according to claim 1, The vehicle control system further includes a gradient sensor that detects a road surface gradient, which is the gradient of the traveling road of the vehicle. The target acceleration setting unit sets the upper limit acceleration and the lower limit acceleration such that the greater the road surface gradient detected by the gradient sensor, the smaller the difference between the upper and lower limits.

3. In the vehicle control system according to claim 1, The upper limit acceleration is set along a characteristic line that is convex upward in the accelerator opening range greater than or equal to the first opening and less than or equal to the second opening on a map with the accelerator opening on the horizontal axis and the target acceleration on the vertical axis. The lower limit acceleration is set to a value between the provisional lower limit acceleration defined by a straight line connecting two points on the characteristic line corresponding to the first opening and the second opening and the upper limit acceleration.

Images