Vehicle control system

Abstract

The present invention provides a vehicle control device that can suppress the occurrence of crank shock. [Solution] When the vehicle 10 is decelerating and the vehicle speed V is less than or equal to a predetermined value SV, crank shock suppression control SS is performed, which switches the gear stage POSsh of the automatic transmission 22 to the neutral gear stage N, which does not transmit power. As a result, torque is no longer transmitted from the engine 12 to the propeller shaft 24, the propeller torque Tps becomes 0, the surface pressure on the sliding part 30 is reduced, and the sliding part 30 is less likely to maintain its expanded and contracted state. In other words, stick-slip is less likely to occur in the sliding part 30. Therefore, the occurrence of crank shock can be suppressed.

Description

Technical Field

[0001] The present invention relates to a control device for a vehicle provided with a propeller shaft having a slide portion.

Background Art

[0002] In a vehicle, a propeller shaft that transmits power from a power source to drive wheels rotates at high speed and needs to follow changes in the vehicle posture due to inertial forces during starting and stopping, and is provided with a slide portion that can expand and contract in the axial direction. Patent Document 1 discloses suppressing the occurrence of stick-slip in which the slide portion expands and contracts intermittently by a combination of coating on the sliding structural member of the slide portion and a lubricating composition.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, the technique described in Patent Document 1 has an effect of suppressing slip-stick by maintaining the sliding characteristics of the slide portion for a long period under predetermined conditions (temperature, torque). However, for example, when a large torque load is applied to the propeller shaft when the vehicle decelerates and stops, there is room for improvement in countermeasures. During vehicle deceleration, the slide portion slides and expands due to changes in the vehicle posture. At this time, if a large torque is transmitted from the power source to the propeller shaft, the expanded and contracted state of the slide portion is likely to be held by surface pressure, and the slide portion is likely to be in a stretched state even after the vehicle stops. Then, when the torque transmitted to the propeller shaft is reduced, the expanded and contracted state of the slide portion is restored, and physical stick-slip may occur, resulting in the occurrence of shock (crank shock).

[0005] The present invention was made against the above circumstances, and its objective is to provide a vehicle control device that can suppress the occurrence of crank shock. [Means for solving the problem]

[0006] The gist of the first invention is a control device for a vehicle that transmits power from a power source to the drive wheels via a propeller shaft having an axially extendable and retractable sliding portion from an automatic transmission, and (b) when the vehicle is decelerating and the vehicle speed is below a predetermined value, the control device performs crank shock suppression control to put the automatic transmission into a neutral state that does not transmit power. [Effects of the Invention]

[0007] According to the first invention, when the vehicle is decelerating and the vehicle speed is below a predetermined value, crank shock suppression control is performed to put the automatic transmission into a neutral state that does not transmit power. As a result, torque is no longer transmitted from the power source to the propeller shaft, the surface pressure on the sliding part is reduced, and the sliding part is less likely to maintain its expanded and contracted state. In other words, stick-slip is less likely to occur in the sliding part. Therefore, the occurrence of crank shock can be suppressed.

[0008] Preferably, along with the implementation of the crank shock suppression control, a deceleration equivalent braking torque, corresponding to the deceleration torque transmitted by the power source, is generated by a braking device located on the drive wheel side of the propeller shaft and transmitted to the drive wheel. As a result, even when the vehicle is in neutral, the deceleration equivalent braking torque is generated instead of the deceleration torque transmitted from the power source, so that the driver does not feel any discomfort with the vehicle's behavior during deceleration.

[0009] Preferably, if the driver accelerates after the crank shock suppression control has been implemented, the automatic transmission is set to transmit power, and the generation of the deceleration-equivalent braking torque is stopped. This prevents the driver from feeling any discomfort with the vehicle's behavior during acceleration. [Brief explanation of the drawing]

[0010] [Figure 1] This diagram illustrates the schematic configuration of a vehicle to which the present invention is applied. [Figure 2] This diagram illustrates an example of crank shock occurring. [Figure 3] This flowchart explains the key aspects of the control operation of an electronic control unit, specifically the control operation for suppressing crank shock. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Examples]

[0012] Figure 1 is a diagram illustrating the schematic configuration of a vehicle 10 to which the present invention is applied. Figure 1(a) is a diagram illustrating the schematic configuration of the entire vehicle 10. Figure 1(b) is a diagram illustrating an example of a propeller shaft 24 provided in the vehicle 10.

[0013] In Figure 1(a), the vehicle 10 is equipped with an engine 12. The vehicle 10 also includes drive wheels 14 and a power transmission device 20 provided in the power transmission path between the engine 12 and the drive wheels 14. The engine 12 corresponds to the "power source" of the present invention.

[0014] Engine 12 is a known internal combustion engine, and its torque, engine torque Te, is controlled by an electronic control device 50, which will be described later.

[0015] The power transmission system 20 includes an automatic transmission 22, a propeller shaft 24, a differential gear 26, etc., and transmits power from the engine 12 to the drive wheels 14 sequentially via the automatic transmission 22, the propeller shaft 24, and the differential gear 26, etc.

[0016] The automatic transmission 22 is a known planetary gear type stepped transmission that allows for the selection of multiple gear stages POSsh, comprising, for example, multiple sets of planetary gears and multiple hydraulic engagement devices such as clutches and brakes.

[0017] The gear stage POSsh includes, for example, multiple drive gear stages Dsh, such as the first gear stage 1st and the second gear stage 2nd for forward driving, a reverse gear stage R for reverse driving, and a neutral gear stage N that does not transmit power (driving torque) output from the engine 12. Any of the gear stages POSsh is selected according to a command from the electronic control unit 50, which will be described later. The neutral gear stage N corresponds to the "neutral state" of the present invention.

[0018] Furthermore, the drive wheels 14 are equipped with wheel brakes 16. The wheel brakes 16 are braking devices that apply a braking torque Tb generated by the wheel brakes 16 to the drive wheels 14 in accordance with commands from the electronic control device 50, which will be described later.

[0019] In Figure 1(b), the upper left portion shows a cross-sectional view of the propeller shaft 24, while the rest is a front view showing its external shape. The power transmission device 20 further includes a first universal joint 28 and a second universal joint 29. The propeller shaft 24 is connected to the output shaft 22a of the automatic transmission 22 via the first universal joint 28, and to the input shaft 26a of the differential gear 26 via the second universal joint 29 (see Figure 1(a)).

[0020] The propeller shaft 24 has a slide portion 30 that can expand and contract in the axial direction, that is, in the direction of the axis CL of the propeller shaft 24. The slide portion 30 is a slide mechanism for following a change in the length between the automatic transmission 22 and the differential gear 26 due to a change in the vehicle attitude during, for example, acceleration or deceleration.

[0021] The slide portion 30 includes a first hollow shaft 32, a second hollow shaft 34, and a cover member 36. The first hollow shaft 32 is joined to the first universal joint 28. The second hollow shaft 34 is joined to the second universal joint 29. On a part of the outer peripheral surface of the first hollow shaft 32, a male spline 32a for spline fitting is formed. On a part of the inner peripheral surface of the second hollow shaft 34, a female spline 34a for spline fitting is formed. The first hollow shaft 32 and the second hollow shaft 34 are connected such that the male spline 32a and the female spline 34a are spline-fitted, and they are non-rotatable relative to each other around the axis CL and movable relative to each other in the direction of the axis CL. The cover member 36 is a member for preventing foreign matter from entering from the outside into, for example, the portion where the first hollow shaft 32 and the second hollow shaft 34 are spline-fitted.

[0022] The vehicle 10 further includes an electronic control device 50 including a control device of the vehicle 10. The electronic control device 50 is configured to include a so-called microcomputer.

[0023] Various signals (such as signals such as the engine rotational speed Ne, the transmission input rotational speed Ni, the transmission output rotational speed No, the longitudinal acceleration Gx, the accelerator opening θacc, etc.) based on detection values by various sensors etc. (such as an engine rotational speed sensor 52, an input rotational speed sensor 54, an output rotational speed sensor 56, an acceleration sensor 58, an accelerator opening sensor 60, etc.) provided in the vehicle 10 are respectively supplied to the electronic control device 50.

[0024] Engine rotational speed Ne is the rotational speed of engine 12. Transmission input rotational speed Ni is the input rotational speed of automatic transmission 22. Transmission output rotational speed No is the output rotational speed of automatic transmission 22, which corresponds to the vehicle speed V. Longitudinal acceleration Gx is the longitudinal acceleration of vehicle 10; a positive value (Gx>0) indicates that vehicle 10 is accelerating, and a negative value (Gx<0) indicates that it is decelerating. Accelerator opening θacc is the amount of accelerator operation by the driver, representing the magnitude of the driver's acceleration operation.

[0025] The electronic control unit 50 outputs various command signals for controlling various devices (e.g., engine 12, wheel brakes 16, automatic transmission 22, etc.) installed in the vehicle 10. Examples of these command signals include the engine control command signal Se, the wheel brake control command signal Sb, and the transmission control command signal Sat.

[0026] The electronic control unit 50 calculates the amount of drive requested by the driver to the vehicle 10, for example, the requested drive torque Trdem at the drive wheels 14, by applying the accelerator opening θacc and the vehicle speed V to the drive request amount map, and outputs various command signals to realize the requested drive torque Trdem.

[0027] The electronic control unit 50 performs a gear shift determination for the automatic transmission 22 by applying the requested drive torque Trdem and vehicle speed V to the gear shift map, for example, and performs gear stage switching control as needed. The gear shift map is a predetermined relationship that has a gear shift line on a two-dimensional coordinate system where the requested drive torque Trdem and vehicle speed V are variables, for example, in order to determine whether the automatic transmission 22 is shifting.

[0028] Figure 2 illustrates an example of crank shock occurring. In Figure 2, during deceleration of the vehicle 10 (longitudinal acceleration Gx < 0), the sliding portion 30 of the propeller shaft 24 slides and extends due to the change in vehicle posture accompanying the stroke of the rear suspension (see "P / S slide amount" in the figure). When the vehicle 10 stops, the vehicle posture returns to normal, but at this time, if the engine 12 is running (for example, idling), engine torque Te is transmitted to the propeller shaft 24. If the absolute value of the torque transmitted from the engine 12 to the propeller shaft 24 is the propeller torque Tps (see "P / S torque" in the figure), the extended state of the sliding portion 30 is maintained by the surface pressure associated with the propeller torque Tps. Therefore, even after the vehicle speed V has decreased until just before stopping, the sliding portion 30 remains in a taut state. The propeller torque Tps is increased when the automatic transmission 22 downshifts from 2nd gear to 1st gear in preparation for the vehicle 10 to stop. Subsequently, when the vehicle 10 starts moving due to the release of the brakes, the propeller torque Tps decreases, and the taut state of the slide portion 30 is rapidly released, causing the slide portion 30 to compress and resulting in a so-called crank shock. Thus, as the vehicle 10 decelerates and stops, depending on the surface pressure applied to the slide portion 30, stick-slip may occur in the slide portion 30, potentially causing a crank shock. This phenomenon is more pronounced when the propeller torque Tps is large and the surface pressure on the slide portion 30 is high. The higher the surface pressure on the slide portion 30, the easier it is for the slide portion 30 to be held in a state of expansion and contraction.

[0029] Therefore, when the vehicle 10 is decelerating (longitudinal acceleration Gx < 0) and the vehicle speed V is less than or equal to a predetermined value SV (V ≤ SV), the electronic control unit 50 performs crank shock suppression control SS, which switches the gear stage POSsh of the automatic transmission 22 to the neutral gear stage N, which does not transmit power. As a result, torque is no longer transmitted from the engine 12 to the propeller shaft 24, the propeller torque Tps becomes 0, the surface pressure on the sliding part 30 is reduced, and the sliding part 30 is less likely to maintain its expanded and contracted state. In other words, stick-slip is less likely to occur in the sliding part 30. Thus, the occurrence of crank shock can be suppressed. The predetermined value SV is a threshold value that has been determined in advance through design or experimentation to make stick-slip less likely to occur as the vehicle 10 decelerates and stops.

[0030] Preferably, the electronic control device 50, along with implementing crank shock suppression control SS, generates a deceleration equivalent braking torque TB, which corresponds to the deceleration torque transmitted by the engine brake from the engine 12, in the wheel brake 16, which is a braking device located on the drive wheel 14 side of the propeller shaft 24 (braking torque Tb = TB). As a result, even when the vehicle is switched to the neutral gear N, the deceleration equivalent braking torque TB is generated instead of the deceleration torque from the engine brake, so that the driver does not feel any discomfort with the behavior of the vehicle 10 during deceleration.

[0031] Preferably, after the crank shock suppression control SS is performed, if the driver performs an acceleration operation, i.e., if the accelerator opening θacc becomes greater than or equal to a predetermined value θn, the electronic control unit 50 switches the gear stage POSsh to a predetermined drive gear stage Dsh based on the shift map and stops the generation of deceleration equivalent braking torque TB. This prevents the driver from feeling any discomfort with the behavior of the vehicle 10 accompanying the acceleration operation. The predetermined value θn is a preset threshold for determining the acceleration operation.

[0032] Figure 3 is a flowchart illustrating the main part of the control operation of the electronic control device 50, and is a flowchart illustrating the control operation to suppress the occurrence of crank shock, which is, for example, executed repeatedly.

[0033] In Figure 3, each step in the flowchart corresponds to a function of the electronic control unit 50. In step S10 (the steps will be omitted hereafter), it is determined whether the vehicle 10 is decelerating (longitudinal acceleration Gx < 0) and whether the vehicle speed V is less than or equal to a predetermined value SV (V ≤ SV). If the determination in S10 is negative, the routine is terminated. If the determination in S10 is positive, in S20 the gear stage POSsh is switched to the neutral gear stage N, and in S30 a deceleration equivalent braking torque TB is generated in the wheel brake 16. Next, in S40 it is determined whether the driver has performed an acceleration operation, i.e., whether the accelerator opening θacc is greater than or equal to a predetermined value θn, and in S50 it is determined whether the vehicle 10 has come to a complete stop, i.e., whether the vehicle speed V is 0 (V = 0). If both the determinations in S40 and S50 are negative, the routine is terminated. If either the judgment in S40 or S50 is affirmed, in S60 the gear stage POSsh is switched to a predetermined drive gear stage Dsh based on the shift map, and in S70 the generation of the deceleration equivalent braking torque TB is stopped, and this routine is terminated.

[0034] As described above, according to this embodiment, when the vehicle 10 is decelerating and the vehicle speed V is less than or equal to a predetermined value SV, crank shock suppression control SS is performed, which switches the gear stage POSsh of the automatic transmission 22 to the neutral gear stage N, which does not transmit power. As a result, torque is no longer transmitted from the engine 12 to the propeller shaft 24, the propeller torque Tps becomes 0, the surface pressure on the sliding part 30 is reduced, and the sliding part 30 is less likely to maintain its expanded and contracted state. In other words, stick-slip is less likely to occur in the sliding part 30. Therefore, the occurrence of crank shock can be suppressed.

[0035] Furthermore, according to this embodiment, along with the implementation of crank shock suppression control SS, a deceleration-equivalent braking torque TB, which corresponds to the deceleration torque transmitted by the engine brake from the engine 12, is generated in the wheel brake 16, which is a braking device located on the drive wheel 14 side of the propeller shaft 24. As a result, even when the vehicle is switched to the neutral gear N, the deceleration-equivalent braking torque TB is generated instead of the deceleration torque from the engine brake, so that the driver does not feel any discomfort with the behavior of the vehicle 10 during deceleration.

[0036] Furthermore, according to this embodiment, if the driver accelerates after the crank shock suppression control SS is implemented, that is, if the accelerator opening θacc becomes greater than or equal to a predetermined value θn, the gear stage POSsh is switched to a predetermined drive gear stage Dsh based on the shift map, and the generation of deceleration equivalent braking torque TB is stopped. This prevents the driver from feeling any discomfort with the behavior of the vehicle 10 during acceleration.

[0037] Although embodiments of the present invention have been described in detail above with reference to the drawings, the present invention is also applicable to other embodiments.

[0038] For example, in the above-described embodiment, the vehicle 10 was an engine-powered vehicle powered solely by the engine 12. However, the present invention can also be applied to hybrid vehicles (HEVs) powered by both an engine and an electric motor, or electric vehicles (BEVs) powered solely by an electric motor.

[0039] Furthermore, in the above-described embodiment, the deceleration equivalent braking torque TB was generated by the wheel brake 16, but it may also be generated by an electric motor provided on the drive wheel 14 side of the propeller shaft 24 and transmitting power (torque) to the drive wheel 14.

[0040] It should be noted that the above-described embodiment is merely one example, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art. [Explanation of Symbols]

[0041] 10: Vehicle 12: Engine (power source) 14: Drive wheels 20: Power transmission system 22: Automatic transmission 24: Propeller shaft 30: Sliding part 50: Electronic control unit (control unit) N: Neutral gear position (neutral state) SS: Crank shock suppression control SV: Predetermined value V: Vehicle speed

Claims

[Claim 1] A control device for a vehicle that transmits power from a power source to the drive wheels via a propeller shaft having an axially extendable sliding section from an automatic transmission, A vehicle control device characterized by performing crank shock suppression control, which puts the automatic transmission into a neutral state without transmitting power when the vehicle is decelerating and the vehicle speed is below a predetermined value.

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