Vehicle control apparatus

Abstract

To provide a vehicle control apparatus capable of suppressing occurrence of a crank shock.SOLUTION: When a deceleration of a vehicle is equal to or greater than a predetermined deceleration and a torque is being transmitted from a power source to a propeller shaft, the torque transmitted from the power source to the propeller shaft is made to be equal to or less than a predetermined torque. Accordingly, surface pressure at a sliding portion is reduced, and the sliding portion is made less likely to maintain a state of being changed to expand and contract. That is, stick-slip is made less likely to occur at the sliding portion. Therefore, occurrence of a crank shock can be suppressed.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a control device for a vehicle equipped with a propeller shaft having a sliding portion. [Background technology]

[0002] Vehicles equipped with a propeller shaft having a sliding portion that can expand and contract in the axial direction and that constitutes part of a power transmission device that transmits power from a power source to drive wheels are well known. For example, a vehicle described in Patent Document 1 is such a vehicle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-267413 Summary of the Invention [Problem to be solved by the invention]

[0004] Here, the sliding portion of the propeller shaft expands or contracts due to changes in vehicle attitude, such as suspension movement, during acceleration or deceleration. For example, when the vehicle brakes, the sliding portion slides and extends due to changes in vehicle attitude. At this time, if torque is transmitted from the power source to the propeller shaft, the sliding portion is likely to maintain its expanded or contracted state due to surface pressure. For example, even after the deceleration decreases, the sliding portion is likely to remain in a tensioned state. Thereafter, when the torque transmitted to the propeller shaft decreases, the expanded or contracted state of the sliding portion returns to its original state, which may result in a shock (crank shock). In other words, physical stick-slip may occur in the sliding portion, causing a crank shock. This phenomenon is more pronounced the greater the deceleration and the more likely the sliding portion is to expand or contract.

[0005] The present invention has been made in light of the above circumstances, and an object of the present invention 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) a control device for a vehicle having a power source and a propeller shaft having a sliding portion that can expand and contract in the axial direction and that forms part of a power transmission device that transmits power from the power source to drive wheels, and (b) when the deceleration of the vehicle is equal to or greater than a predetermined deceleration and torque is being transmitted from the power source to the propeller shaft, the control device reduces the torque transmitted from the power source to the propeller shaft to less than a predetermined torque. [Effects of the Invention]

[0007] According to the first aspect of the present invention, when the deceleration of the vehicle is equal to or greater than a predetermined deceleration and torque is being transmitted from the power source to the propeller shaft, the torque transmitted from the power source to the propeller shaft is reduced to equal to or less than the predetermined torque. This reduces the surface pressure on the sliding portion, making it difficult for the sliding portion to maintain a state in which it has expanded or contracted. In other words, stick-slip is made difficult to occur in the sliding portion. This makes it possible to suppress the occurrence of crank shock. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a schematic configuration of a vehicle to which the present invention is applied; [Figure 2] FIG. 10 is a diagram illustrating an example in which a crank shock occurs. [Figure 3] 4 is a flowchart illustrating a main part of the control operation of the electronic control device, and is a flowchart illustrating the control operation for suppressing the occurrence of crank shock. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Example]

[0010] Fig. 1 is a diagram illustrating a schematic configuration of a vehicle 10 to which the present invention is applied. Fig. 1(a) is a diagram illustrating a schematic configuration of the entire vehicle 10. Fig. 1(b) is a diagram illustrating an example of a propeller shaft 24 provided in the vehicle 10.

[0011] 1(a), a vehicle 10 is a hybrid vehicle equipped with an engine 12 and an electric motor MG, which function as a power source SP. The vehicle 10 also includes drive wheels 14 and a power transmission device 20 provided in a power transmission path between the engine 12 and the drive wheels 14.

[0012] The engine 12 is a known internal combustion engine, and an electronic control device 50 (described later) controls the engine torque Te of the engine 12. The electric motor MG is a known motor generator, and an electronic control device 50 (described later) controls the electric motor torque Tm of the electric motor MG.

[0013] The power transmission device 20 includes a clutch K0, an automatic transmission 22, a propeller shaft 24, a differential gear 26, and the like, each of which constitutes part of the power transmission device 20. The clutch K0 is a clutch provided between the engine 12 and the electric motor MG. The automatic transmission 22 is connected to the clutch K0 and is disposed in a power transmission path between the power source SP and the drive wheels 14. The electric motor MG is connected to the power transmission path between the clutch K0 and the automatic transmission 22 so as to be able to transmit power. In other words, the electric motor MG is connected to the automatic transmission 22 so as to be able to transmit power without going through the clutch K0.

[0014] In the vehicle 10, when the clutch K0 is engaged, the engine 12 and the automatic transmission 22 are connected to each other so that power can be transmitted between them. On the other hand, when the clutch K0 is disengaged, power transmission between the engine 12 and the automatic transmission 22 is interrupted. Because the electric motor MG is connected to the automatic transmission 22, the clutch K0 functions as a connecting / disconnecting clutch that connects and disconnects the engine 12 from the electric motor MG.

[0015] When the clutch K0 is engaged, the power transmission device 20 transmits power from the engine 12 to the drive wheels 14, sequentially via the clutch K0, the automatic transmission 22, the propeller shaft 24, the differential gear 26, etc. Furthermore, regardless of the control state of the clutch K0, the power transmission device 20 transmits power from the electric motor MG to the drive wheels 14, sequentially via the automatic transmission 22, the propeller shaft 24, the differential gear 26, etc.

[0016] 1(b), the upper left portion shows a cross-sectional view of the propeller shaft 24, and the rest is a front view showing the exterior. 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 is connected to the input shaft 26a of the differential gear 26 via the second universal joint 29 (see FIG. 1(a)).

[0017] The propeller shaft 24 has a sliding portion 30 that is extendable and contractible in the axial direction, i.e., in the direction of the axis CL of the propeller shaft 24. The sliding portion 30 is a sliding mechanism that follows changes in the length between the automatic transmission 22 and the differential gear 26 due to changes in the vehicle posture, for example, during acceleration or deceleration.

[0018] 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. The first hollow shaft 32 has a male spline 32a formed on a portion of its outer circumferential surface for spline engagement. The second hollow shaft 34 has a female spline 34a formed on a portion of its inner circumferential surface for spline engagement. The first hollow shaft 32 and the second hollow shaft 34 are spline-engaged with each other through the male spline 32a and the female spline 34a, and are connected so as to be non-rotatable about the axis CL but 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 the portion where the first hollow shaft 32 and the second hollow shaft 34 are spline-engaged from the outside.

[0019] The vehicle 10 further includes an electronic control unit 50 including a control device for the vehicle 10. The electronic control unit 50 includes a so-called microcomputer equipped with, for example, a CPU, RAM, ROM, an input / output interface, etc. The CPU executes various controls of the vehicle 10 by performing signal processing in accordance with a program stored in advance in the ROM while utilizing the temporary storage function of the RAM.

[0020] The electronic control device 50 is supplied with various signals based on detection signals from various sensors (not shown) provided in the vehicle 10. The various signals include, for example, engine rotation speed Ne, motor rotation speed Nm, transmission input rotation speed Ni, transmission output rotation speed No, vehicle acceleration G, accelerator opening θacc, etc.

[0021] The engine rotation speed Ne is the rotation speed of the engine 12. The electric motor rotation speed Nm is the rotation speed of the electric motor MG. The transmission input rotation speed Ni is the input rotation speed of the automatic transmission 22. The transmission output rotation speed No is the output rotation speed of the automatic transmission 22, and is a rotation speed corresponding to the vehicle speed V. The vehicle acceleration G is a signal representing the acceleration Ga or deceleration Gd of the vehicle 10. The accelerator opening θacc is the amount of accelerator operation by the driver, which represents the magnitude of the driver's acceleration operation. If the acceleration Ga is a positive value, the deceleration Gd will be a negative value, but for convenience, the magnitude of the deceleration Gd will be compared in absolute value.

[0022] The electronic control device 50 outputs various command signals for controlling various devices (e.g., the engine 12, the electric motor MG, the clutch K0, the automatic transmission 22, etc.) provided in the vehicle 10. The various command signals include, for example, an engine control command signal Se, an electric motor control command signal Sm, a clutch pressure control command signal Sk0, and a transmission control command signal Sat.

[0023] The electronic control unit 50 calculates the amount of driving demand made by the driver to the vehicle 10, such as the required driving torque Trdem at the drive wheels 14, for example, by applying the accelerator opening θacc and the vehicle speed V to a driving demand map. The electronic control unit 50 outputs various command signals and the like to realize the required driving torque Trdem, taking into consideration the auxiliary load, the gear ratio of the automatic transmission 22, and the like.

[0024] When the required drive torque Trdem can be satisfied solely by the output of the electric motor MG, the electronic control unit 50 establishes the BEV mode as the drive mode for driving the vehicle 10. The BEV mode is an electric drive mode that enables motor driving (BEV driving) in which the vehicle runs using only the electric motor MG as the power source SP with the clutch K0 disengaged and the engine 12 stopped. On the other hand, the electronic control unit 50 establishes the HEV mode as the drive mode when the required drive torque Trdem cannot be satisfied without using at least the output of the engine 12. The HEV mode is a hybrid drive mode that enables engine driving, i.e., hybrid driving (HEV driving), in which the vehicle runs using at least the engine 12 as the power source SP with the clutch K0 engaged. On the other hand, even when the required drive torque Trdem can be satisfied solely by the output of the electric motor MG, the electronic control unit 50 establishes the HEV mode as the drive mode when, for example, a battery (not shown) needs to be charged or the engine 12 needs to be warmed up. The battery is an electricity storage device that exchanges electric power with the electric motor MG.

[0025] FIG. 2 is a diagram illustrating an example of the occurrence of crank shock. In FIG. 2, when the vehicle 10 is braked, the sliding portion 30 of the propeller shaft 24 slides and extends due to a change in vehicle posture caused by the stroke of the rear suspension (see "P / S slide amount" in the figure). When the vehicle 10 is stopped by braking, the vehicle posture is returned to its original position. At this time, if the engine 12 is in an operating state (e.g., idling), engine torque Te is transmitted to the propeller shaft 24. The extended state of the sliding portion 30 is maintained by surface pressure caused by propeller torque Tps (see "P / S torque" in the figure), which is torque transmitted from the power source SP to the propeller shaft 24. Therefore, even after the deceleration Gd decreases, the sliding portion 30 remains in a tensioned state. The propeller torque Tps is increased by downshifting the automatic transmission 22 to first gear 1st in preparation for stopping the vehicle 10. Thereafter, when the vehicle 10 starts moving with the brakes released and the propeller torque Tps is reduced, the tensioned state of the sliding portion 30 is rapidly released, causing the sliding portion 30 to contract, resulting in a so-called crank shock. In this way, depending on the situation in which surface pressure is applied to the sliding portion 30, stick-slip may physically occur in the sliding portion 30, resulting in a crank shock. This phenomenon is more pronounced the greater the deceleration Gd and the more easily the sliding portion 30 is subject to expansion / contraction, or the greater the propeller torque Tps and the higher the surface pressure on the sliding portion 30. The higher the surface pressure on the sliding portion 30, the more easily the sliding portion 30 is maintained in the expanded / contracted state.

[0026] Therefore, when the deceleration Gd of the vehicle 10 is equal to or greater than a predetermined deceleration Gdf and torque is being transmitted from the power source SP to the propeller shaft 24, the electronic control device 50 sets the propeller torque Tps to equal to or less than a predetermined torque Tpsf. The predetermined deceleration Gdf is a predetermined threshold value for determining whether the deceleration Gd is so great that a crank shock may occur, for example. The case where torque is being transmitted from the power source SP to the propeller shaft 24 is synonymous with the case where a crank shock may occur, for example. The predetermined torque Tpsf is the upper limit of a predetermined range of the propeller torque Tps in which the sliding portion 30 of the propeller shaft 24 is unlikely to maintain its expanded or contracted state, for example.

[0027] The electronic control device 50 reduces the torque of the power source SP so as to reduce the propeller torque Tps, for example, to make the propeller torque Tps equal to or less than a predetermined torque Tpsf. The electronic control device 50 reduces the torque of the power source SP, for example, by transitioning the drive mode from HEV mode to BEV mode. By reducing the propeller torque Tps, the surface pressure on the sliding portion 30 of the propeller shaft 24 is reduced, making it possible to suppress the occurrence of crank shock.

[0028] Alternatively, the electronic control device 50 may, for example, cut off the transmission of torque from the power source SP to the propeller shaft 24, thereby setting the propeller torque Tps to a predetermined torque Tpsf or less. The electronic control device 50 may, for example, stop the power source SP and cut off the power transmission between the power source SP and the propeller shaft 24, thereby cutting off the power transmission between the power source SP and the propeller shaft 24. The electronic control device 50 may, for example, place the automatic transmission 22 in a neutral state in which power transmission is cut off, thereby cutting off the power transmission between the power source SP and the propeller shaft 24. Cutting off the torque transmitted to the propeller shaft 24 can suppress the occurrence of crank shock.

[0029] Alternatively, the electronic control device 50 may, for example, absorb the engine torque Te with the negative torque of the electric motor MG, thereby keeping the propeller torque Tps equal to or less than a predetermined torque Tpsf. Absorbing the negative torque of the electric motor MG means, for example, causing the electric motor MG to function as a generator using the power of the engine 12. For example, by having the electric motor MG absorb the idling torque of the engine 12, the propeller torque Tps is reduced, and the occurrence of crank shock can be suppressed.

[0030] For example, when performing control to absorb engine torque Te by the negative torque of the electric motor MG, the electronic control device 50 keeps the battery charged at a lower level in a driving state in which there is a possibility of crank shock occurring, compared to when there is no possibility of crank shock occurring. By keeping the battery charged at a low level, the electric power generated by the electric motor MG can be absorbed, and control to absorb engine torque Te by the negative torque of the electric motor MG can be performed.

[0031] FIG. 3 is a flowchart illustrating the main control operations of the electronic control unit 50, which are executed repeatedly, for example, to suppress the occurrence of crank shock.

[0032] In FIG. 3, each step in the flowchart corresponds to a function of the electronic control device 50. In step (hereinafter, "step" will be omitted) S10, it is determined whether the deceleration Gd is equal to or greater than a predetermined deceleration Gdf. If the determination in S10 is negative, S10 is repeatedly executed. If the determination in S10 is positive, it is determined in S20 whether there is a possibility of crank shock occurring, that is, whether torque is being transmitted from the power source SP to the propeller shaft 24. If the determination in S20 is negative, the process returns to S10. If the determination in S20 is positive, it is determined in S30 whether a transition to the BEV mode is possible. For example, it is determined whether a transition to the BEV mode is possible based on whether stopping the engine 12 is unlikely to cause any problems. If the determination in S30 is positive, a transition to the BEV mode is made in S40. Next, in S50, it is determined whether the deceleration Gd is less than a predetermined deceleration Gdf. If the determination in S50 is negative, S50 is repeatedly executed. On the other hand, if the determination in S30 is negative, in S60, the electric motor MG absorbs the idling torque of the engine 12. Next, in S70, it is determined whether the deceleration Gd is less than a predetermined deceleration Gdf. If the determination in S70 is negative, S70 is repeatedly executed. If the determination in S50 is positive, or if the determination in S70 is positive, this routine is terminated.

[0033] As described above, according to this embodiment, when the deceleration Gd of the vehicle 10 is equal to or greater than the predetermined deceleration Gdf and torque is being transmitted from the power source SP to the propeller shaft 24, the propeller torque Tps is made equal to or less than the predetermined torque Tpsf. This reduces the surface pressure on the sliding portion 30 of the propeller shaft 24, making it difficult for the sliding portion 30 to maintain a state in which it has expanded or contracted. In other words, stick-slip is made difficult to occur in the sliding portion 30. This makes it possible to suppress the occurrence of crank shock.

[0034] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the present invention can also be applied to other embodiments.

[0035] For example, in the above-described embodiment, the present invention can be applied even if the vehicle 10 is an engine vehicle using only the engine 12 as the power source SP, or an electric vehicle (BEV) using only the electric motor MG as the power source SP. For example, if the vehicle 10 is an engine vehicle, the propeller torque Tps is set to a predetermined torque Tpsf or less by interrupting the transmission of engine torque Te to the propeller shaft 24. The electronic control device 50 interrupts the transmission of engine torque Te to the propeller shaft 24, for example, by performing idling stop control of the engine 12 while the vehicle is traveling and interrupting the power transmission between the engine 12 and the propeller shaft 24.

[0036] It should be noted that the above is merely one embodiment, and the present invention can be embodied in various forms with various modifications and improvements based on the knowledge of those skilled in the art. [Explanation of symbols]

[0037] 10: Vehicle 12: Engine (power source) 14: Drive wheels 20: Power transmission device 24: Propeller shaft 30: Slide section 50: Electronic control device (control device) MG: Electric motor (power source) SP: Power source

Claims

[Claim 1] A control device for a vehicle including a power source and a propeller shaft having a slide portion that is extendable and contractible in an axial direction and that constitutes a part of a power transmission device that transmits power from the power source to drive wheels, A vehicle control device characterized in that, when the deceleration of the vehicle is equal to or greater than a predetermined deceleration and torque is being transmitted from the power source to the propeller shaft, the torque transmitted from the power source to the propeller shaft is set to be equal to or less than a predetermined torque.

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