JP3970830B2 - Control device for four-wheel drive vehicle - Google Patents

Description

  The present invention relates to a control device for a four-wheel drive vehicle that can be driven by an electric motor that is driven by power generation of an alternator that drives one of the front and rear wheels by an engine and drives the other wheel by the engine.

  In recent years, as a form of a four-wheel drive vehicle, there is a four-wheel drive vehicle that can be driven by an electric motor that is operated by power generation of an alternator that drives one of the front and rear wheels by an engine and the other wheel driven by the engine. It has been developed and put into practical use.

For example, in Japanese Patent Application Laid-Open No. 2000-142155, in a slip state, a four-wheel drive vehicle that normally switches a changeover switch connecting an alternator and a battery and supplies power generated by the alternator to an electric motor that drives a rear wheel is disclosed. It is disclosed. In this technology, the power generation amount of the alternator is controlled according to the accelerator opening degree in the slip state. When the accelerator opening degree is large and the engine output is large, the power generation amount of the alternator is increased and the accelerator opening degree is increased. When the engine output is small, the power generation amount of the alternator is gradually increased. Accordingly, it is intended to prevent engine stall due to a heavy load applied to the engine in a state where the engine output is small.
JP 2000-142155 A

  However, in Patent Document 1 described above, the main focus is on preventing the engine stall in the slip state. For example, when the accelerator opening is large and the engine output is large despite the small slip state. Since the power generation amount of the alternator is increased, the rear wheel is driven with a large output by the electric motor in an attempt to eliminate the slip state. For this reason, the appropriate power distribution between the front wheels and the rear wheels, which reflects the actual slip state, cannot be performed, and the electric motor that has been driven with a large output suddenly stops when the slip state is resolved. There is a problem that the driver feels uncomfortable.

  The present invention has been made in view of the above circumstances, and optimally controls the driving force distribution between the front wheels and the rear wheels by reflecting the actual slip state without applying an excessive load to the engine, and is excellent in drive feeling. Another object of the present invention is to provide a control device for a four-wheel drive vehicle.

  The present invention relates to a control device for a four-wheel drive vehicle that can be driven by an electric motor that is driven by power generation of an alternator that drives one of the front and rear wheels by an engine and the other wheel driven by the engine. The difference rotation calculation means for calculating the difference between the rotation speed of the vehicle and the rotation speed of the rear wheel as a front-rear difference rotation, the slip condition detection means for detecting the slip condition of the vehicle, and the slip condition detection means detects the slip condition of the vehicle. And when the engine speed and / or the vehicle speed exceed a preset threshold, the alternator control means for generating the alternator according to the forward / backward differential rotation, and the slip state detection The means detects the slip state of the vehicle, and at least one of the engine speed and the vehicle speed is set in advance. Does not exceed the value is characterized in that an engine load suppressing means to suppress the load on the engine.

  According to the control device for a four-wheel drive vehicle according to the present invention, the driving force distribution between the front wheels and the rear wheels is optimally controlled by reflecting the actual slip state without imposing an excessive load on the engine. The effect is excellent.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 5 show a first embodiment of the present invention, FIG. 1 is a schematic explanatory diagram showing the entire drive system and control system of a four-wheel drive vehicle, and FIG. 2 is a flowchart of a main program for four-wheel drive control. FIG. 3 is an explanatory diagram of a map of an alternator load that is set according to the front-rear differential rotation when the engine speed is high in the slip state, and FIG. 4 is set according to the engine speed when the engine speed is low in the slip state. FIG. 5 is a time chart showing an example of the effect of the four-wheel drive control when starting and accelerating on a low μ road.

  In FIG. 1, reference numeral 1 denotes a four-wheel drive vehicle. In this four-wheel drive vehicle 1, the driving force generated by the engine 2 is transmitted to the front wheels 5 fl and 5 fr via the automatic transmission 3 and the front differential 4. The

  In FIG. 1, reference numeral 6 denotes an alternator that is driven by the engine 2 to generate electric power. The electric motor (rear wheel drive motor) 7 is operated by the electric power generated by the alternator 6. The driving force generated by the rear wheel drive motor 7 is transmitted to the rear wheels 5rl and 5rr via a predetermined speed reducer 8 and a rear differential 9.

  On the other hand, the four-wheel drive vehicle 1 is provided with sensors such as four wheel speed sensors 11fl, 11fr, 11rl, 11rr and an engine speed sensor 12, and four wheels from these sensors. The signals of the speeds ωfl, ωfr, ωrl, ωrr, and engine speed NE are input to the control device 20 that performs four-wheel drive control described later.

  The control device 20 receives signals from the above-described sensors, and controls the alternator 6 while monitoring the motor speed of the rear wheel drive motor 7 and the like. That is, the control device 20 is configured to have functions as a front-rear differential rotation calculation unit, a slip state detection unit, an alternator control unit, and an engine load suppression unit. This will be described with reference to the flowchart of FIG.

  First, in step (hereinafter abbreviated as “S”) 101, necessary parameters, that is, signals of four-wheel wheel speeds ωfl, ωfr, ωrl, ωrr, and engine speed NE are read.

  Next, in S102, the difference between the rotational speed of the front wheels ((ωfl + ωfr) / 2) and the rotational speed of the rear wheels ((ωrl + ωrr) / 2) is calculated as the front-rear differential rotation ΔFR.

  Next, the process proceeds to S103, where the forward / backward differential rotation ΔFR is compared with a value Δc1 obtained in advance through experiments or the like, and when the forward / backward differential rotation ΔFR is smaller than Δc1 (when ΔFR <Δc1), it is determined that there is no slip state. In S104, the power supply to the rear wheel drive motor 7 by the alternator 6 is stopped, and the program is exited.

  If the result of determination in S103 is that the forward / backward differential rotation ΔFR is equal to or greater than Δc1 (when ΔFR ≧ Δc1), it is determined that the vehicle is slipping and the process proceeds to S105 and thereafter.

  In S105, the engine speed NE is set in advance by comparing the engine speed NE with a preset threshold value NEC (for example, idling speed +500 rpm, specifically about 1000 rpm). If it is determined that the threshold value is more than NEC (when NE ≧ NEC), it is determined that the engine output is sufficient, and the process proceeds to S106. The alternator 6 generates power according to the rotation ΔFR, and the rear wheel drive motor 7 is driven with this power generation amount. The power generation of the alternator 6 according to the front-rear differential rotation ΔFR is performed based on a map stored in advance. In this map, as shown in FIG. 3, the larger the forward / backward differential rotation ΔFR is, the larger the power generation of the alternator 6 is, the greater the rear wheel side driving force distribution is, and the rear wheel side is driven faster to drive forward / backward differential rotation. ΔFR is reduced.

  If it is determined in S105 that the engine speed NE is smaller than the preset threshold NEC (when NE <NEC), the engine output is insufficient to supplement the power generation of the alternator 6. In step S107, the power generation amount of the alternator 6 is limited to suppress the load on the engine 2. The power generation amount of the alternator 6 is limited by, for example, a map as shown in FIG. 4, and the alternator 6 does not generate power in a region where the engine speed NE is extremely low. It is set such that the power generation amount of the alternator 6 gradually increases as the number NE increases.

  After the processing of S106 or S107, the process proceeds to S108, where the power supply to the rear wheel drive motor 7 is executed based on the power generation amount of the alternator 6 set in S106 or S107, and the program is exited.

  In the four-wheel drive vehicle 1 driven by the rear wheel drive motor 7 driven by the power generation of the alternator 6 that drives the front wheels by the engine 2 and drives the rear wheels by the engine 2 as in the first embodiment, When starting and accelerating with slip on the μ road, for example, as shown in FIG. 5, the front and rear wheels tend to rotate faster on the front wheel side.

  That is, on a low μ road with a slip, when the vehicle 1 starts to accelerate (from time t1), the wheel speed on the front wheel side increases and no control is performed as it is. As indicated by the one-dot broken line in FIG. 5, there is a possibility that the difference in wheel speed between the front wheels and the rear wheels (front / rear rotational difference ΔFR) is widened, the grip force is lost, and stable start / acceleration cannot be performed.

  In the first embodiment, when the front-rear rotational difference ΔFR is equal to or greater than the value Δc1 previously obtained through experiments or the like (time t2), it is determined that a slip condition has occurred, and the engine speed NE is determined in advance. If it is determined that the output is smaller than the preset threshold NEC, the power output of the alternator 6 is limited so that the engine 2 is not burdened because the output of the engine 2 is insufficient. On the other hand, when it is determined that a slip condition has occurred and the engine speed NE is determined to be greater than or equal to a preset threshold value NEC, it is determined that the engine output is sufficient, and the excessive driving force of the engine 2 is increased by the alternator 6. In order to utilize this power generation, the engine 2 causes the alternator 6 to generate power in accordance with the forward / backward differential rotation ΔFR, and the rear wheel drive motor 7 is driven with this power generation amount. As a result, the driving force distribution on the rear wheel side increases, and the rear wheel side is driven quickly to reduce the front-rear differential rotation ΔFR.

  Next, FIGS. 6 to 8 show a second embodiment of the present invention, FIG. 6 is a schematic explanatory diagram showing the entire drive system and control system of a four-wheel drive vehicle, and FIG. 7 is a main view of four-wheel drive control. FIG. 8 is a flowchart of the program, and FIG. 8 is an explanatory diagram of a map of clutch engagement force set according to the engine speed when the engine speed is low in the slip state. In the second embodiment, a hydraulic clutch capable of controlling transmission of engine driving force is provided between the engine 2 and the automatic transmission 3, and this hydraulic pressure is output when the output of the engine 2 is insufficient in a slip state. Unlike the first embodiment, the load on the engine 2 is limited by controlling the clutch, and the power generation amount of the alternator is performed in accordance with the forward / backward differential rotation ΔFR. Since other configurations and operations are the same as those of the first embodiment, the same reference numerals as those of the first embodiment are used, and description thereof is omitted.

  That is, as shown in FIG. 6, a hydraulic clutch (clutch control means) 31 is provided between the engine 2 and the automatic transmission 3 as drive force transmission control means that can control transmission of engine drive force. In addition, the clutch fastening force of the hydraulic clutch 31 is controlled by a signal from the control device 30.

  Specifically, as shown in the flowchart of FIG. 7, in step S105, the engine speed NE is compared with a preset threshold NEC, and it is determined that the engine speed NE is equal to or greater than the preset threshold NEC. If this is the case (NE ≧ NEC), it is determined that the engine output is sufficient, and the process proceeds to S106. In order to utilize the excessive driving force of the engine 2 for power generation of the alternator 6, the engine 2 responds to the forward / backward differential rotation ΔFR. The alternator 6 generates power, and the rear wheel drive motor 7 is driven with this power generation amount. The power generation of the alternator 6 according to the front-rear differential rotation ΔFR is performed based on a map as shown in FIG. 3 stored in advance, for example, as in the first embodiment. Then, after S106, the process proceeds to S108, where power is supplied to the rear wheel drive motor 7 based on the power generation amount of the alternator 6 set in S106, and the program is exited.

  On the other hand, as a result of the determination in S105, if it is determined that the engine speed NE is smaller than the preset threshold NEC (when NE <NEC), the engine output is insufficient to supplement the power generation of the alternator 6. In step S201, the hydraulic clutch 31 is controlled to suppress the load on the engine 2. The control of the hydraulic clutch 31 is performed based on, for example, a map as shown in FIG. 8, and in a region where the load of the alternator 6 is assumed to be higher than the engine output torque, the clutch engagement force is 0, that is, the hydraulic clutch 31. Is controlled so that the engine driving force is not transmitted to the front wheels. Conversely, in a region where the load on the alternator 6 is assumed to be smaller than the engine output torque, control is performed so that the clutch engagement force is gradually increased and the driving force is transmitted to the front wheels. By controlling the fastening force of the hydraulic clutch 31 in this way, it is possible to prevent an excessive load from being applied to the engine 2.

  Thereafter, the process proceeds to S202, and in the same manner as S106, the engine 2 causes the alternator 6 to generate power according to the forward / backward differential rotation ΔFR, and the process proceeds to S108. Supply power to and exit the program.

  As described above, according to the second embodiment, when it is determined that the engine speed NE is smaller than the preset threshold NEC due to the slip state, the output of the engine 2 is insufficient. By controlling the hydraulic clutch 31, the transmission of the driving force to the front wheels is suppressed, thereby suppressing an excessive load on the engine 2. About the effect other than this, the effect similar to the said 1st form is acquired.

  In the second embodiment, the example in which the hydraulic clutch 31 is used to control the transmission of the engine driving force has been described. However, an electromagnetic clutch or the like may be used instead.

  In the first and second embodiments, the front wheel is driven by the engine 2 and the rear wheel is driven by the electric motor 7. However, the rear wheel is driven by the engine 2 and the electric motor 7 is driven. Thus, it goes without saying that the present invention can be applied even to a vehicle that drives the front wheels.

  In the first and second embodiments of the present invention, the determination as to whether or not the engine 2 has a sufficient output, that is, the determination in S105 is performed based on the engine speed NE and a preset threshold NEC. However, it may be performed by comparing the vehicle speed V with a preset threshold value of the vehicle speed.

Schematic explanatory view showing the entire drive system and control system of a four-wheel drive vehicle according to the first embodiment of the present invention. Same as above, flowchart of main program for four-wheel drive control Same as above, explanatory diagram of alternator load map set according to front / rear differential rotation when engine speed is high in slip state Same as above, explanatory diagram of alternator load map set according to engine speed when engine speed is low in slip state Same as above, time chart showing an example of the effect of this four-wheel drive control when starting and accelerating on a low μ road Schematic explanatory diagram showing the entire drive system and control system of a four-wheel drive vehicle according to a second embodiment of the present invention. Same as above, flowchart of main program for four-wheel drive control As above, an explanatory diagram of a map of clutch engagement force set according to the engine speed when the engine speed is low in the slip state

Explanation of symbols

1 Four-wheel drive vehicle 2 Engine 5fl, 5fr Front wheel 5rl, 5rr Rear wheel 6 Alternator 7 Electric motor (rear wheel drive motor)
11 fl, 11 fr, 11 rl, 11 rr Wheel speed sensor 12 Engine speed sensor 20 Control device (front-rear differential rotation calculation means, slip state detection means, alternator control means, engine load suppression means)
Attorney Susumu Ito

Claims (4)

In a control device for a four-wheel drive vehicle that can be driven by an electric motor driven by power generation of an alternator that drives one of the front and rear wheels by an engine and the other wheel driven by the engine,
Front-rear differential rotation calculation means for calculating the difference between the front wheel rotation speed and the rear wheel rotation speed as a front-rear differential rotation;
Slip state detecting means for detecting the slip state of the vehicle;
When the slip state detecting means detects the slip state of the vehicle and at least one of the engine speed and the vehicle speed exceeds a preset threshold value, the alternator generates power according to the forward / backward differential rotation. Alternator control means to be performed;
Engine load suppression for suppressing the load on the engine when the slip state detecting means detects the slip state of the vehicle and at least one of the engine speed and the vehicle speed does not exceed the preset threshold value. Means,
A control device for a four-wheel drive vehicle.   2. The control apparatus for a four-wheel drive vehicle according to claim 1, wherein when the engine load suppression means suppresses the load on the engine, the engine load suppression means limits the power generation amount of the alternator. A driving force transmission control means for controlling transmission of the engine driving force between the engine and the one drive wheel from the engine;
2. The control apparatus for a four-wheel drive vehicle according to claim 1, wherein the engine load suppression means controls the driving force transmission control means when the load on the engine is suppressed.   4. The control apparatus for a four-wheel drive vehicle according to claim 3, wherein the driving force transmission control means is a clutch control means.

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