Vehicle control system

Abstract

The present invention provides a vehicle control device that improves the responsiveness of clutch state determination during vehicle startup. [Solution] When the first electric motor MG1 is driven and the vehicle 10 is started using only the rear wheels 14, the electronic control unit 80 determines that the dog clutch 60 is engaged if the front-to-rear wheel speed difference ΔVmg, which is the absolute value of the difference between the first vehicle speed Vmg1 calculated from the first rotational speed Nmg1 and the second vehicle speed Vmg2 calculated from the second rotational speed Nmg2, is less than or equal to the first threshold N1. As a result, the determination of the state of the dog clutch 60 when the vehicle 10 is started is performed using the first rotational speed Nmg1 and the second rotational speed Nmg2 detected by the MG1 rotation sensor 90 and the MG2 rotation sensor 92, which have no time lag until detection (output), instead of using the wheel speed sensor 94 which has a time lag until detection (output). This improves the responsiveness of the determination of the state of the dog clutch 60 when the vehicle 10 is started.

Description

Technical Field

[0001] The present invention relates to a control device for a vehicle including a power source that drives a main drive wheel, an electric motor that drives a sub-drive wheel, and a clutch provided in a power transmission path between the sub-drive wheel and the electric motor.

Background Art

[0002] A control device for a vehicle including a power source that drives a main drive wheel, an electric motor that drives a sub-drive wheel, and a clutch provided in a power transmission path between the sub-drive wheel and the electric motor is well known. For example, the vehicle control device described in Patent Document 1 is such a device. In this Patent Document 1, in the engaged state of the clutch, the rotational speeds of the main drive wheel and the sub-drive wheel are detected by wheel speed sensors, and when the decrease rate of the rotational speed of the sub-drive wheel is greater than a predetermined value and the rotational speed of the sub-drive wheel is smaller than that of the main drive wheel by a predetermined value or more, it is disclosed that the clutch is disengaged.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] With the aforementioned wheel speed sensor, when the vehicle is in motion, i.e., when the wheels are rotating, the rotational speed is detected (output) in accordance with the change in rotational speed. However, when the wheels start rotating from a standstill, a considerable time lag occurs before the rotational speed is detected (output). Therefore, when determining the clutch state during vehicle startup, i.e., whether it is engaged or disengaged, by driving the power source to start the vehicle with only the main drive wheels and comparing the rotational speed detected by the wheel speed sensor of the auxiliary drive wheels with the rotational speed of the electric motor, there is a problem that the clutch state determination is delayed because of the time lag before the rotational speed is detected (output) from the wheel speed sensor.

[0005] The present invention was made against the above circumstances, and its objective is to provide a vehicle control device that improves the responsiveness of clutch state determination when the vehicle starts moving. [Means for solving the problem]

[0006] The gist of the first invention is a control device for a vehicle comprising: (a) a power source for driving the main drive wheels; an electric motor for driving the auxiliary drive wheels; a clutch provided in the power transmission path between the auxiliary drive wheels and the electric motor; a power source rotation sensor for detecting the rotational speed of the power source as a first rotational speed; and an electric motor rotation sensor for detecting the rotational speed of the electric motor as a second rotational speed, wherein (b) when the power source is driven and the vehicle is started using only the main drive wheels, the control device determines that the clutch is engaged if the difference between the front and rear wheel speeds, which is the difference between the vehicle speed calculated from the first rotational speed and the vehicle speed calculated from the second rotational speed, is less than or equal to a first threshold.

[0007] The gist of the second invention is that the determination of whether the difference in front and rear wheel speeds is less than or equal to the first threshold is made when the vehicle speed calculated from the first rotational speed is greater than or equal to the second threshold.

[0008] The gist of the third invention is to increase the first threshold and / or decrease the second threshold as the coefficient of friction of the road surface increases. [Effects of the Invention]

[0009] According to the first invention, when the power source is driven and the vehicle is started using only the main drive wheels, if the difference between the front and rear wheel speeds, which is the difference between the vehicle speed calculated from the first rotational speed and the vehicle speed calculated from the second rotational speed, is less than or equal to the first threshold, the clutch is determined to be engaged. As a result, the clutch state determination when the vehicle is started is performed using the first rotational speed and the second rotational speed detected by the power source rotation sensor and the electric motor rotation sensor, which have no time lag until detection (output), rather than using a wheel speed sensor which has a time lag until detection (output). This improves the responsiveness of the clutch state determination when the vehicle is started.

[0010] According to the second invention, the determination of whether the difference in front and rear wheel speeds is less than or equal to the first threshold is performed when the vehicle speed calculated from the first rotational speed is greater than or equal to the second threshold. This allows the clutch state determination to be performed at an appropriate timing while improving responsiveness.

[0011] According to the third invention, the greater the coefficient of friction of the road surface, the larger the first threshold and / or the smaller the second threshold. As a result, the less slippery the road surface, the earlier the timing of the clutch state determination is made, thus improving responsiveness. [Brief explanation of the drawing]

[0012] [Figure 1] This diagram illustrates the schematic configuration of a vehicle to which the present invention is applied. [Figure 2] This is a time chart illustrating an example of the detection operation of the rotational speeds of the auxiliary drive wheels, electric motor, and power source when the vehicle starts up. [Figure 3] This is a flowchart illustrating the key aspects of the control operation of an electronic control unit. [Modes for carrying out the invention]

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Examples]

[0014] Figure 1 is a diagram illustrating the schematic configuration of a vehicle 10 to which the present invention is applied. In Figure 1, the vehicle 10 is equipped with left and right front wheels 12, a front drive unit 20 that drives the front wheels 12, left and right rear wheels 14, and a rear drive unit 30 that drives the rear wheels 14, all spaced apart from each other. The vehicle 10 is also equipped with a battery 40, which is a rechargeable DC power source. Note that "left and right" above refers to left and right with respect to the forward direction of the vehicle 10.

[0015] Vehicle 10 is an all-wheel drive vehicle in which the drive torque distribution between the front wheels 12 and the rear wheels 14 can be adjusted. All-wheel drive (AWD) and four-wheel drive (4WD) are synonymous. In addition to driving in 4WD mode, vehicle 10 can also drive in two-wheel drive (2WD) mode in which drive torque is distributed only to the rear wheels 14. The rear wheels 14 correspond to the "main drive wheels" of this invention, and the front wheels 12 correspond to the "secondary drive wheels" of this invention.

[0016] The front drive unit 20 comprises a second electric motor MG2 and a front PCU (Power Control Unit) 24. The second electric motor MG2 is a known AC synchronous motor, a so-called motor generator, and is connected to the battery 40 via the front PCU 24. The second electric motor MG2 is the motor that drives the front wheels 12, which are auxiliary drive wheels. The front PCU 24 is a power control device that controls the power exchanged between the battery 40 and the second electric motor MG2. The front PCU 24 controls the power of the second electric motor MG2 by being controlled by the electronic control device 80 described later.

[0017] The front drive unit 20 includes a counter gear mechanism 50, a counter shaft 52, a final gear 54, a front differential gear (hereinafter referred to as the front wheel differential) 56, etc. The front drive unit 20 also includes left and right front drive shafts 58 connected to the front differential 56, etc. The counter gear mechanism 50 is a gear pair having a drive gear 50a and a driven gear 50b that meshes with the drive gear 50a. The drive gear 50a is connected to the second electric motor MG2, and the driven gear 50b is connected to the final gear 54 via the counter shaft 52. The final gear 54 meshes with the differential ring gear 56r of the front differential 56. The front drive shafts 58 connect the front differential 56 to the front wheels 12. The front drive unit 20 transmits power from the second electric motor MG2 to the front wheels 12.

[0018] The front drive unit 20 includes a dog clutch 60 and an actuator 62. The dog clutch 60 is a known meshing clutch provided in the power transmission path between the front wheel 12 and the second electric motor MG2. The actuator 62 controls the switching between the engaged and disengaged states of the dog clutch 60 by being controlled by the electronic control unit 80 described later. The dog clutch 60 corresponds to the "clutch" of the present invention.

[0019] The dog clutch 60 is provided, for example, in the power transmission path between the front differential 56 and the left front wheel 12. The dog clutch 60 has a first dog tooth 60a and a second dog tooth 60b as opposing meshing teeth. The first dog tooth 60a is connected to the front differential 56 and is the meshing tooth on the second electric motor MG2 side of the opposing meshing teeth. The second dog tooth 60b is connected to the left front drive shaft 58 and is the meshing tooth on the front wheel 12 side of the opposing meshing teeth. The dog clutch 60 is engaged when the first dog tooth 60a and the second dog tooth 60b mesh, and is released when their meshing is disengaged.

[0020] The rear drive device 30 includes a first electric motor MG1 and a rear PCU 34. The first electric motor MG1 is a known AC synchronous motor, which is a so-called motor generator, and is connected to the battery 40 via the rear PCU 34. The first electric motor MG1 is a power source for driving the rear wheels 14, which are the main drive wheels. The rear PCU 34 has the same functions as the front PCU 24 and controls the power of the first electric motor MG1 by being controlled by an electronic control device 80 described later.

[0021] The rear drive device 30 includes a counter gear mechanism 70, a counter shaft 72, a final gear 74, a rear differential gear 76, left and right rear drive shafts 78, etc. The rear drive device 30 has the same functions as the front drive device 20 and transmits the power from the first electric motor MG1 to the rear wheels 14.

[0022] In the vehicle 10, the rear wheels 14 are driven when in the 2WD state and the 4WD state, and the front wheels 12 are driven only when in the 4WD state. The 4WD state is a driving state in which the front wheels 12 and the rear wheels 14 are driven in the engaged state of the dog clutch 60, and the power transmission path between the front wheels 12 and the second electric motor MG2 is in a connected state, that is, a connect state. The 2WD state is a driving state in which only the rear wheels 14 are driven in the released state of the dog clutch 60, and the power transmission path between the front wheels 12 and the second electric motor MG2 is in a disconnected state, that is, a disconnect state. By being in the disconnect state during the 2WD state, the rotation of the rotating members of the front drive device 20 on the second electric motor MG2 side and the rotation of the second electric motor MG2 are stopped compared to the dog clutch 60. Thereby, the occurrence of power loss due to the rotation of the counter gear mechanism 50, the final gear 54, the front differential 56, etc. is prevented or suppressed. The dog clutch 60 is a disconnect mechanism capable of disconnecting the power transmission path between the front wheels 12 and the second electric motor MG2.

[0023] The vehicle 10 further includes an electronic control device 80 configured to include a so-called microcomputer as a control device of the vehicle 10.

[0024] The electronic control unit 80 is supplied with various signals based on detection values ​​from various sensors installed in the vehicle 10. These sensors include, for example, the MG1 rotation sensor 90, the MG2 rotation sensor 92, the wheel speed sensor 94, the accelerator opening sensor 96, the brake sensor 98, and the on-board camera 100. The signals include, for example, the first rotation speed Nmg1, which is the rotation speed of the first motor MG1; the second rotation speed Nmg2, which is the rotation speed of the second motor MG2; the left front wheel rotation speed Nwfl; the right front wheel rotation speed Nwfr; the accelerator opening θacc; the brake operation amount Bra; and on-board camera image information Iard. The front wheel rotation speed Nwf is the average value of the left front wheel rotation speed Nwfl and the right front wheel rotation speed Nwfr. The MG1 rotation sensor 90 and the MG2 rotation sensor 92 are configured to include a known resolver for detecting the rotation angle of the motor generator, and can detect the rotation speed by precisely tracking it from a stopped state. Furthermore, the first rotational speed Nmg1 corresponds to the vehicle speed V of the vehicle 10, and the second rotational speed Nmg2 corresponds to the dog rotational speed Ndg1, which is the rotational speed of the first dog tooth 60a. The MG1 rotation sensor 90 corresponds to the "power source rotation sensor" of the present invention, and the MG2 rotation sensor 92 corresponds to the "motor rotation sensor" of the present invention.

[0025] The electronic control unit 80 outputs various command signals to each device installed in the vehicle 10. These devices include, for example, the front PCU 24, the rear PCU 34, and the actuator 62. The various command signals include, for example, the MG2 control signal Smg2 for controlling the second motor MG2, the MG1 control signal Smg1 for controlling the first motor MG1, and the actuator control signal Sc for controlling the switching between the engaged and disengaged states of the dog clutch 60.

[0026] The electronic control unit 80 calculates the required acceleration or deceleration for the vehicle 10 based on the accelerator opening θacc and / or brake operation amount Bra, and determines whether to switch the drive state based on the required acceleration or deceleration, wheel slip, and the driver's selection of the driving mode. For example, if the required acceleration or deceleration is increased while in 2WD state, the electronic control unit 80 determines whether to switch to 4WD state, controls the second rotation speed Nmg2 (second electric motor MG2) so that the dog rotation speed Ndg1 of the first dog tooth 60a and the left front wheel rotation speed Nwfl, which corresponds to the rotation speed of the second dog tooth 60b, are synchronized, and operates the actuator 62 to engage the dog clutch 60.

[0027] Figure 2 is a time chart illustrating the changes in front wheel speed Vwf, second vehicle speed Vmg2, and first vehicle speed Vmg1, respectively, when the vehicle 10 is started using only the rear wheels 14 by driving the first electric motor MG1. The front wheel rotation speed Nwf, the second rotation speed Nmg2, the second rotation speed Nmg1, and the first rotation speed Nmg1, respectively, are converted to vehicle speed V. The vertical axis represents the converted values ​​to vehicle speed V, allowing for a comparison of the changes on the same scale. In Figure 2, the upper section shows the case when the dog clutch 60 is engaged, and the lower section shows the case when the dog clutch 60 is disengaged.

[0028] In the upper part of Figure 2, at time t0, the first electric motor MG1 starts to drive, the rear wheels 14 drive the road surface, and the vehicle 10 starts to move. As the vehicle 10 starts to move, the front wheels 12 and the second electric motor MG2, which is connected to the front wheels 12 via the dog clutch 60, also rotate. As a result, the second vehicle speed Vmg2, calculated from the second rotational speed Nmg2 detected by the MG2 rotation sensor 92, increases in line with the increase in the first vehicle speed Vmg1, and both become equal in speed. Here, "equal speed" means that the speeds are close enough to be judged as equal, and more precisely, it means that the absolute value of the difference between the speeds is less than or equal to a preset threshold NS (|Vmg1-Vmg2|≦NS). In the upper part of Figure 2, it is shown that the first vehicle speed Vmg1 and the second vehicle speed Vmg2 are judged to be equal in speed at time t1 when they have increased to vehicle speed Vb. On the other hand, the front wheel speed Vwf, calculated from the front wheel rotation speed Nwf detected by the wheel speed sensor 94, is detected (output) from t2 as shown in Figure 2 because there is a time lag between when the front wheel 12 starts rotating at t0 and when the rotation speed is detected (output). At t4, when the speed has increased to Vc, it is determined to be the same speed as the first vehicle speed Vmg1 and the second vehicle speed Vmg2. In contrast, in the lower part of Figure 2 (when the dog clutch 60 is released), the dog clutch 60 is in the released state, and even if the front wheel 12 rotates, the second motor MG2 does not rotate, so the second vehicle speed Vmg2 remains 0.

[0029] Incidentally, when the vehicle 10 starts moving as described above, the state of the dog clutch 60 (determining whether it is engaged or disengaged) was conventionally determined by comparing the front wheel speed Vwf with the second wheel speed Vmg2. For example, in Figure 2, at point t4 when the front wheel speed Vwf has increased to the vehicle speed Vc, if the front wheel speed Vwf and the second wheel speed Vmg2 are determined to be at the same speed (|Vwf-Vmg2| ≤ threshold NS), it is determined to be engaged. At point t3 when the front wheel speed Vwf has increased to a predetermined vehicle speed Va, if the second wheel speed Vmg2 is 0 and their rotational speeds are diverging, it is determined to be disengaged. Thus, the conventional determination could only be performed after point t2 when the front wheel speed Vwf was detected (output) from the wheel speed sensor 94, which resulted in a delay in determining the state of the dog clutch 60.

[0030] Furthermore, the state of the dog clutch 60 can also be determined by, for example, generating a predetermined driving force (torque) in the second electric motor MG2 that is not large enough to start the vehicle 10 when the vehicle 10 is stopped. If the second electric motor MG2 does not rotate due to the generated driving force (torque) (the second rotational speed Nmg2 does not increase), it is determined to be in an engaged state. If the second electric motor MG2 rotates (the second rotational speed Nmg2 increases), it is determined to be in a disengaged state. However, this method has the problem that it is necessary to drive the second electric motor MG2 in order to determine the state of the dog clutch 60, which worsens the power consumption.

[0031] Therefore, the electronic control device 80 of this embodiment determines the state of the dog clutch 60 by comparing the first vehicle speed Vmg1 and the second vehicle speed Vmg2. For example, in Figure 2, at time t1 when the first vehicle speed Vmg1 has increased to vehicle speed Vb, if the first vehicle speed Vmg1 and the second vehicle speed Vmg2 are determined to be at the same speed (|Vmg1-Vmg2| ≤ threshold NS), the state is determined to be engaged; otherwise, if they are not determined to be at the same speed (|Vmg1-Vmg2| > threshold NS), the state is determined to be released. This allows the state of the dog clutch 60 to be determined at time t1, which is earlier than the aforementioned time t2. Furthermore, by suitably adjusting the values ​​of the vehicle speed Vb and the threshold NS, it is also possible to perform the determination at an earlier timing than time t1.

[0032] Figure 3 is a flowchart illustrating the main parts of the control operation of the electronic control unit 80, and is a flowchart illustrating the control operation for determining the state of the dog clutch 60. This flowchart is executed, for example, when the first electric motor MG1 is driven and the vehicle 10 is started using only the rear wheels 14.

[0033] First, in step S10 (the steps will be omitted hereafter), the first vehicle speed Vmg1, the second vehicle speed Vmg2, the first threshold N1, and the second threshold N2 are read.

[0034] Next, in S20, it is determined whether the first vehicle speed Vmg1 is greater than or equal to the second threshold N2 (Vmg1≧N2). If the determination in S20 is negative, steps S10 and below are repeated. If the determination in S20 is positive, in S30, it is determined whether the front-to-rear wheel speed difference ΔVmg, which is the absolute value of the difference between the first vehicle speed Vmg1 and the second vehicle speed Vmg2, is less than or equal to the first threshold N1 (ΔVmg=|Vmg1-Vmg2|≦N1).

[0035] If the determination in S30 is positive, in S40 the dog clutch 60 is determined to be engaged; if the determination in S30 is negative, in S50 the dog clutch 60 is determined to be released, and this routine is terminated.

[0036] The second threshold N2 is a fixed value that has been pre-designed or experimentally set so that the determination in S30, i.e., the determination of the state of the dog clutch 60, is expedited and performed at an appropriate timing (corresponding to time t1 in Figure 2). The first threshold N1 is also a fixed value that has been pre-designed or experimentally set so that the determination of the state of the dog clutch 60 is performed favorably in the determination in S30.

[0037] Preferably, in S10, the road surface friction coefficient RE is calculated according to a predetermined calculation method based on information from the road surface image acquired from, for example, the onboard camera imaging information Iard from the onboard camera 100. The first threshold N1 and / or the second threshold N2 are calculated, for example, by referring to a predetermined map, such that the larger the road surface friction coefficient RE, the larger the first threshold N1 and / or the smaller the second threshold N2. As a result, in S10, the larger the road surface friction coefficient RE, the larger the first threshold N1 and / or the smaller the second threshold N2 is set to be, so the larger the road surface friction coefficient RE, the earlier the timing of the judgment in S30, i.e., the dog clutch 60 state determination. In other words, the less slippery the road surface, the earlier the timing of the dog clutch 60 state determination is, thus improving responsiveness.

[0038] Furthermore, the determination of S20 may be made not by the first vehicle speed Vmg1, but by the first rotational speed Nmg1 and the second threshold N2 which is set in accordance with the first rotational speed Nmg1.

[0039] As described above, according to the electronic control device 80 of this embodiment, when the first electric motor MG1 is driven and the vehicle 10 is started using only the rear wheels 14, if the front-to-rear wheel speed difference ΔVmg, which is the absolute value of the difference between the first vehicle speed Vmg1 calculated from the first rotational speed Nmg1 and the second vehicle speed Vmg2 calculated from the second rotational speed Nmg2, is less than or equal to the first threshold N1, the dog clutch 60 is determined to be engaged. As a result, the determination of the state of the dog clutch 60 when the vehicle 10 is started is performed using the first rotational speed Nmg1 and the second rotational speed Nmg2 detected by the MG1 rotation sensor 90 and the MG2 rotation sensor 92, which have no time lag until detection (output), rather than using the wheel speed sensor 94 which has a time lag until detection (output). Therefore, the responsiveness of the determination of the state of the dog clutch 60 when the vehicle 10 is started is improved.

[0040] Furthermore, according to the electronic control device 80 of this embodiment, the determination of whether the front-to-rear wheel speed difference ΔVmg is less than or equal to the first threshold N1 is performed when the first vehicle speed Vmg1 calculated from the first rotational speed Nmg1 is greater than or equal to the second threshold N2. As a result, the state determination of the dog clutch 60 is performed at an appropriate timing while improving responsiveness.

[0041] Furthermore, according to the electronic control device 80 of this embodiment, the larger the road surface friction coefficient RE, the larger the first threshold N1 and / or the smaller the second threshold N2. As a result, the less slippery the road surface, the earlier the timing of the dog clutch 60 state determination is made, thus improving responsiveness.

[0042] 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.

[0043] For example, in the embodiment described above, the power source for the rear drive unit 30 may be an engine in addition to, or instead of, the first electric motor MG1. Alternatively, the main drive wheels may be the front wheels 12 and the secondary drive wheels may be the rear wheels 14. In this case, the system includes a power source for driving the front wheels 12, an electric motor for driving the rear wheels 14, and a clutch provided in the power transmission path between the rear wheels 14 and the electric motor.

[0044] 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]

[0045] 10: Vehicle 12: Front wheels (auxiliary drive wheels) 14: Rear wheels (main drive wheels) 60: Dog clutch (clutch) 80: Electronic control unit (control unit) 90: MG1 rotation sensor (power source rotation sensor) 92: MG2 rotation sensor (motor rotation sensor) MG1: First motor (power source) MG2: Second motor (motor) N1: First threshold N2: Second threshold Nmg1: First rotation speed Nmg2: Second rotation speed Vmg1: First vehicle speed (vehicle speed calculated from first rotation speed) Vmg2: Second vehicle speed (vehicle speed calculated from second rotation speed) RE: Road surface friction coefficient (road surface friction coefficient) ΔVmg: Front and rear wheel speed difference

Claims

1. A control device for a vehicle comprising: a power source for driving the main drive wheels; an electric motor for driving the auxiliary drive wheels; a clutch provided in the power transmission path between the auxiliary drive wheels and the electric motor; a power source rotation sensor for detecting the rotational speed of the power source as a first rotational speed; and an electric motor rotation sensor for detecting the rotational speed of the electric motor as a second rotational speed, When the power source is driven and the vehicle is started using only the main drive wheels, if the difference between the front and rear wheel speeds, which is the difference between the vehicle speed calculated from the first rotational speed and the vehicle speed calculated from the second rotational speed, is less than or equal to the first threshold, the clutch is determined to be engaged. A vehicle control device characterized by the following features.

2. The determination of whether the difference in front and rear wheel speeds is less than or equal to the first threshold is made when the vehicle speed calculated from the first rotational speed is greater than or equal to the second threshold. A vehicle control device according to feature 1.

3. The greater the coefficient of friction of the road surface, the larger the first threshold and / or the smaller the second threshold. A vehicle control device according to feature 2.

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