JP2006213130A - Torque distribution device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a torque distribution device capable of maintaining accelerating performance even in an output limited state. <P>SOLUTION: This torque distribution device is for each of wheels 46 for a movable body furnished with a plurality of the wheels 46, the total sum of torque distributed to each of the wheels 46 is corrected so as not to exceed the potential output power in the case when power demanded by a system exceeds the potential output power of a motive power source 10 of the system, and the torque of each of the wheels 46 is distributed so that acceleration of the movable body can be maintained. It is possible to restrain lowering of the accelerating performance as the torque of the wheels 46 is distributed so that acceleration of the movable body can be maintained even in the case of the output limited, and a sense of incongruity in operating feeling is never given to a driver. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an improvement in a technique for distributing wheel torque according to various conditions in a four-wheel drive vehicle or the like.

  In a four-wheel drive vehicle, the rotational force of a drive source such as a motor is transmitted by mechanical elements such as a transfer, a propeller shaft, and a differential to generate torque on each wheel, or by two or more drive sources. There are electrical controls that drive different wheels. The former mechanical four-wheel drive vehicle is generally not accurate and cannot distribute torque between the front and rear wheels. In this regard, the latter, which is based on electrical control, determines the torque distribution according to the change in the ground contact load of the wheel due to acceleration of the tire driving force, load movement due to turning, etc., so that stable four-wheel driving is possible. .

Conventionally, as a driving force control device for a four-wheel drive vehicle using such a plurality of drive sources, there has been one disclosed in, for example, Japanese Patent Laid-Open No. 5-328542 (Patent Document 1). According to this publication, the driving force distribution means calculates the driving force distribution value for each wheel based on the detection signals of the driving force detection means, the vehicle state detection means, and the driving state detection means. By such calculation, it is possible to determine the distribution value of the driving force of each wheel according to the movement of the ground load of the inner wheel and the ground load of the outer wheel at the time of turning. He was able to prevent falling into an unstable situation.
Japanese Patent Laid-Open No. 5-328542 (paragraph 0024, etc.) Japanese Patent Laid-Open No. 2-31929 JP 2002-78110 A

  However, in the conventional driving force control device, sufficient acceleration may not be obtained depending on the traveling state of the vehicle.

  For example, in the driving force control according to the above technique, the outputtable torque at that time is distributed to each wheel, and even when the outputable torque is limited by the state of the vehicle or the power source, The torque was evenly distributed to each wheel at the same rate. However, in a situation where the output of the power source that supplies power to the drive source must be limited, the output of the reduced power source is further distributed, so that less torque is supplied to each loaded wheel. It will be a thing.

  However, the timing at which acceleration is required is irrelevant whether or not the power source is in the output limited state. For this reason, even if acceleration operation, such as depressing an accelerator, is performed, the subject that the vehicle may not accelerate according to it occurred. Such driving force control gives the driver a sense of incongruity on the operational sensation and misunderstands that the vehicle is fundamentally insufficient in power.

  Accordingly, an object of the present invention is to provide a torque distribution device that can maintain acceleration performance even in an output limited state.

  In order to achieve the above object, the present invention provides a torque distribution device to each wheel for a moving body having a plurality of wheels, wherein the power required for the system is an outputable power of the power source of the system. The total torque distributed to each wheel is corrected so as not to exceed the output power, and the torque of each wheel is distributed so that the acceleration of the moving body can be maintained. It is characterized by.

  Further, the present invention is a torque distribution device to each wheel for a moving body having front wheels and rear wheels, and when the power required for the system exceeds the output power of the power source of the system, Means for correcting the sum of the torques distributed to the wheels so as not to exceed the output power of the power source of the system, and the torque between the front wheels and the rear wheels so that the acceleration of the moving body can be maintained. And means for distributing.

  Furthermore, the present invention provides a torque distribution device to each wheel for a moving body having a front wheel and a rear wheel, and when the torque to be distributed to each wheel is in an output limited state, the torque of the rear wheel is The torque of the front wheel and the rear wheel is distributed so as to be equal to or less than a predetermined value.

  If the power that can be supplied by the system is less than the power that is originally required, it must be corrected to a range of power that can cover the torque supplied to the wheels. However, even in a wheel with a large load state, if the torque is reduced according to the output limit, the acceleration performance itself is affected. In this respect, according to the configuration of the present invention, the torque of the wheel is distributed so that the torque of the rear wheel becomes a predetermined value or less, for example, so that the acceleration of the moving body can be maintained even if the torque correction according to the output restriction is performed. Therefore, torque distribution without reducing the acceleration performance is possible. As an example, in a moving body with a power source etc. stored on the front side, the load on the front wheel side is greater than that on the rear wheel side, so acceleration performance can be achieved by increasing the torque distribution on the front wheel side compared to the torque distribution on the rear wheel side. Can be suppressed.

  Here, “to maintain acceleration performance” means to suppress the degree of the decrease even if the acceleration performance is reduced (changed) to some extent, in addition to maintaining the same acceleration performance as when there is no output restriction. Including the case of torque distribution.

  “Front wheels” and “rear wheels” are concepts determined by whether the relative arrangement of a plurality of wheels is forward or backward with respect to a direction suitable for high-speed traveling. .

  Further, “exceeding” includes not only a larger value but also a case where the required power is less than or equal to the outputable power but is approaching a certain value range. This is because it is conceivable to change the torque distribution as soon as possible by securing an operation margin.

  For example, the torque distribution for each wheel is determined according to the load distribution for each wheel. This is because the acceleration performance can be improved by increasing the torque distribution of the wheel having the larger load distribution.

  Here, when grasping the torque distributed to the front wheels and the rear wheels, it is preferable to stop the antilock brake function and / or the traction control function. This is because these functions are accompanied by locking and braking of the wheels, and therefore, when calculating the correct torque distribution, it is desirable to stop the operation to increase accuracy.

  Further, the present invention is a torque distribution device to each wheel for a moving body having a plurality of wheels, and when the power required for the system exceeds the power that can be output from the power source of the system, It is also a torque distribution device in which the total torque distributed to each wheel is corrected so as not to exceed the output power, and the torque distribution of each vehicle is determined according to the load distribution on each wheel. Thus, the torque distribution may be determined according to the load distribution of the wheels, not from the viewpoint of whether acceleration can be maintained. This is because the acceleration performance can be improved by increasing the torque distribution of the wheel having the larger load distribution.

  According to the present invention, according to the configuration of the present invention, even if the output is limited, the torque of the wheel is distributed so that the acceleration of the moving body can be maintained, so that the acceleration performance is prevented from deteriorating. Therefore, the driver does not feel uncomfortable with the operational feeling.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.
These embodiments are examples in which the torque distribution device of the present invention is mounted on an electric vehicle using a fuel cell as a power source. The present invention is not limited to this embodiment and can be variously modified and implemented.

(Embodiment 1)
The first embodiment relates to a four-wheel drive vehicle in which a motor as a drive source is provided on each wheel.
FIG. 1 shows a system configuration diagram of a four-wheel drive vehicle in the present embodiment. As shown in FIG. 1, the four-wheel drive vehicle includes a fuel cell system, a power system 4, and a control system 5.
The electric power system 4 includes a secondary battery 40, a high voltage converter 41, a low voltage converter 42, a low voltage system auxiliary machine 43, traction inverters 44fR, 44fL, 44rR, 44rL (hereinafter, represented by “traction inverter 44”), and a traction motor 45fR. , 45fL, 45rR, 45rL (hereinafter represented by “traction motor 45”) and wheels 46fR, 46fL, 46rR, 46rL (hereinafter represented by “wheel 46”).

  The secondary battery 40 is an auxiliary power source for the fuel cell system, and is configured by stacking a large number of battery modules such as nickel metal hydride. The secondary battery 40 supplies power at a predetermined voltage (for example, 200 V) or charges surplus power. Is possible. That is, when the power (power) required by the system exceeds the power (power) that can be output from the fuel cell stack 10, the secondary battery 40 compensates for the power shortage. Further, when the electric vehicle is decelerated and regenerative power is supplied by the traction motor 45, or when surplus power is generated when the power generation amount of the fuel cell stack 10 exceeds the required power of the system, the regenerative power and surplus Charge the power. A battery computer 51 described later is connected to the output terminal of the secondary battery 40.

  The high voltage converter 41 is a voltage converter that converts electric power input to the primary side (input side) into a voltage value different from that of the primary side and outputs the voltage value to the secondary side. For example, the output voltage (for example, 500 V) of the fuel cell stack 10 on the primary side is stepped down to a low voltage (for example, about 200 V) on the secondary side. The high voltage converter 41 has a circuit configuration as, for example, a three-phase bridge type converter. The circuit configuration of the three-phase bridge converter combines an inverter-like circuit part that once converts an input DC voltage into AC, and a part that rectifies the AC again and converts it to a different DC voltage. The input / output current and the input / output voltage of the high-voltage converter 41 can be actually measured by a current sensor and a voltage sensor (not shown).

  The low voltage converter 42 is configured to step down the secondary voltage of the high voltage converter 41 to a low voltage supply voltage (for example, several tens of volts) required for the operation of the low voltage auxiliary machine 43. The low-voltage auxiliary machine 43 is a generic name for auxiliary machines driven by the low-voltage supply voltage of the low-voltage converter 42. For example, such a low-pressure auxiliary machine includes a sound device such as a car audio, a control device such as a navigation system, and lamps.

  The traction inverter 44 and the traction motor 45 are respectively provided so as to correspond to the respective wheels of the four-wheel drive vehicle. And a motor 45fL, an inverter 44rR and a motor 45rR for the rear wheel right wheel 46rR, and an inverter 44rL and a motor 45fL for the rear wheel left wheel 46rL. Each inverter 44 outputs an independent three-phase alternating current in response to a drive signal from the control unit 50, and each motor 45 is driven with an independently set torque corresponding thereto.

  Each traction inverter 44 has a circuit configuration of a voltage-type PWM inverter having a switching element such as an IGBT (Insulated Gate Bipolar Transistor), for example, and a DC current supplied from the secondary side of the power system 4 has an arbitrary amplitude during acceleration. The three-phase AC current is supplied to the traction motor 45, which is the main engine. Further, at the time of deceleration, the three-phase alternating current regenerative power supplied from the traction motor 45 can be converted into a corresponding direct current and supplied to the secondary battery 40.

  Each traction motor 45 is a so-called AC synchronous motor, and when accelerating, the electric energy supplied as a three-phase AC from the traction inverter 44 is returned to the torque that is the corresponding rotational force to rotate each wheel 46, and the electric vehicle Move. Further, at the time of deceleration, the rotational force of each wheel 46 is converted into electric energy to generate regenerative power, and a regenerative braking force is applied to each wheel 46.

Next, the control system 5 will be described. The control system 5 includes a control unit 50, a battery computer (SOC) 51, and the like.
Control unit 50 is a known computer system, such as ECU (E lectric C ontrol U nit ), CPU (not shown) (central processing unit) and a memory, an interface circuit, a software program by the CPU are stored in the ROM or the like It is possible to make this system function as the torque distribution device of the present invention by executing each of the above. That is, when the power required for the system exceeds the power that can be output from the fuel cell stack 10 that is the power source of the system by the procedure described later (FIG. 2), the total torque distributed to each wheel 46 is The torque of each wheel 46 is distributed so that the power that can be output is not exceeded and the acceleration of the four-wheel drive vehicle that is a moving body can be maintained.

The battery computer 51 is configured to be controllable so as to maintain the state of charge (SOC) of the secondary battery 40 in an appropriate range. For example, it is discharged to supply a shortage of electric power when the load is high, such as during acceleration, and regenerative power generated by regenerative braking is charged during deceleration, and these discharge and charge are repeated. The battery computer 51 detects the voltage, temperature, current, ambient temperature, etc. of each cell constituting the secondary battery 40, and integrates the charge / discharge amount of the secondary battery 40 to indicate a relative value indicating the state of charge. The SOC value is output to the control unit 50 as a detection signal S _SOC indicating the state of charge.

  The control unit 50 receives detection signals from other sensors (not shown) for measuring the operation state and the traveling state of the four-wheel drive vehicle. For example, a shift position of the shift lever is detected by a shift position sensor as an operation state detection means, and is input to the control unit as a shift position signal Ss. The operation state of the accelerator pedal that the driver depresses and operates is detected by an accelerator position sensor and input to the control unit as an accelerator position signal Sa. The operation state of the brake pedal is detected by a brake position sensor and is input to the control unit as a brake position signal Sb. The operation state of these pedals is detected by converting a stroke into a voltage using a variable resistor.

  Further, as a means for detecting the traveling state of the four-wheel drive vehicle, the rotational speed of each wheel 46 is detected by a wheel speed sensor provided for each wheel, and is input to the control unit as a wheel speed signal Sr. As the wheel speed sensor, a speed sensor or a current sensor for detecting a driving current of the motor can be used. As for the load on each wheel 46, the stroke of each suspension is detected by a load sensor, or the stress is directly detected as a detection voltage by a piezoelectric element strain gauge, and is input to the control unit as a weight signal Sw. The acceleration in the longitudinal direction of the vehicle is detected by an acceleration sensor and input to the control unit as an acceleration signal Sac. The rotational acceleration around the Z-axis of the vehicle, that is, the turning acceleration of the vehicle is detected by the yaw rate sensor and input to the control unit as the yaw rate signal Sy. The acceleration detected by the acceleration sensor corresponds to the longitudinal acceleration (vertical G), and the turning acceleration detected by the yaw rate sensor corresponds to the lateral acceleration (lateral G).

  Next, a fuel cell system that is a power source will be described. The fuel cell system supplies power to the power system 4, and includes a fuel gas supply system 1, an oxidizing gas supply system 2, and a cooling system 3 with a fuel cell stack 10 as a center.

The fuel cell stack 10, a hydrogen gas as the fuel gas, air as an oxidizing gas, and because a separator having a flow path of the cooling water, put between a pair of separators MEA and (M embrane E lectrode A ssembly) It has a stack structure in which a plurality of cells are stacked. The MEA has a structure in which a polymer electrolyte membrane is sandwiched between two electrodes, an anode and a cathode. The anode is provided with an anode catalyst layer on the porous support layer, and the cathode is provided with a cathode catalyst layer on the porous support layer. Since the fuel cell causes a reverse reaction of water electrolysis, hydrogen gas, which is a fuel gas, is supplied from the fuel gas supply system 1 to the anode side, and air, which is an oxidizing gas, is the oxidizing gas to the cathode side. Supplied from the supply system 2. The fuel cell stack 10 connects single cells in series to generate a predetermined high voltage (for example, about 500 V) between the anode electrode A and the cathode electrode C, which are output terminals, and the high voltage converter 41 of the power system 4 Supplying as primary side input.

  The fuel gas supply system 1 is a system for supplying hydrogen gas to the fuel cell stack 10. The fuel gas supply system 1 includes a hydrogen tank 11, a cutoff valve (original valve) SV 1, a regulator RG, a fuel cell inlet cutoff valve SV 2, and the fuel cell stack 10. A fuel cell outlet cutoff valve SV3, a gas-liquid separator 12 and a cutoff valve SV5, a hydrogen pump 13, a purge cutoff valve SV5, and a check valve RV are provided. A part of the hydrogen gas discharged from the fuel cell stack 10 is purged through the purge cutoff valve SV5 and discharged to the outside, but the rest is returned to the fuel gas flow path again through the check valve RV. It has become.

  The hydrogen tank 11 has a structure as a high-pressure hydrogen tank. The shut-off valve SV1 is a main valve that controls whether or not hydrogen gas is supplied to the fuel gas passage. The regulator RG is a pressure regulating valve that regulates the hydrogen gas pressure in the circulation path. The shutoff valve SV3 is shut off when the supply of hydrogen gas to the fuel cell stack 10 is stopped. The shut-off valve SV4 controls the discharge of hydrogen off gas from the fuel cell stack 10. The gas-liquid separator 12 removes moisture and other impurities generated by the electrochemical reaction of the fuel cell stack 10 during normal operation from the hydrogen off-gas and discharges them to the outside through the shut-off valve SV5. The hydrogen pump 13 can forcibly circulate hydrogen gas in the circulation path. The purge shut-off valve SV5 is opened at the time of purging, but is shut off at the time of normal operation state and pipe gas leak determination. The hydrogen off gas purged from the purge shutoff valve SV5 is processed in an exhaust system including a diluter (not shown). The check valve RV can prevent the backflow of hydrogen gas in the circulation path.

  The oxidizing gas supply system 2 is a system that supplies air, which is an oxidizing gas, to the fuel cell stack 10, and includes an air cleaner 21, a compressor 22, a humidifier 23, and the like. The air cleaner 21 can clean the outside air and take it into the fuel electric system. The compressor 22 compresses the taken-in air according to the control of the control unit 50, and changes the amount of air to be supplied and the air pressure. The humidifier 23 can add an appropriate humidity to the compressed air by exchanging air off-gas and moisture. The air off-gas discharged from the fuel cell stack 10 and separated by the humidifier 23 is discharged after diluting the hydrogen off-gas from the purge cutoff valve SV5 in a diluter (not shown).

  The cooling system 3 includes a radiator 31, a fan 32, and a cooling pump 33, and coolant is circulated and supplied into the fuel cell stack 10. Specifically, when the coolant enters the fuel cell stack 10, it is supplied to each single cell via the manifold, flows through the coolant flow path of the separator, and takes heat from power generation.

Next, a torque distribution method according to this embodiment will be described with reference to the flowchart of FIG.
In the present embodiment, the control system 5 is controlled to realize the following functional means.
1) When the electric power required for the four-wheel drive vehicle exceeds the output power of the fuel cell stack 10 that is the power source of this system, the total torque distributed to each wheel 46 is the fuel. Means for correcting so as not to exceed the output power of the battery stack 10; and
2) A means for distributing torque between the front wheels 46fR / L and the rear wheels 46rR / L so that the acceleration of the four-wheel drive vehicle can be maintained.
Specifically, when the torque to be distributed to each wheel 46 is in an output limited state, the torques of the front wheels 46fR / L and the rear wheels 46rR / L are distributed so that the torque of the rear wheels 46rR / L is a predetermined value or less. Is done.

  From the standpoint of maintaining the cruising distance, the fuel cell system limits output to the fuel cell system depending on the amount of hydrogen gas remaining in the fuel cell system, the degree of deviation from the IV characteristics, the amount of charge of the secondary battery, etc. Must be multiplied. The present invention realizes torque distribution so that acceleration performance is not significantly reduced even in such an output limited state.

FIG. 2 relates to this torque distribution processing and is periodically performed when the four-wheel drive vehicle is in a traveling state.
First, based on detection signals from various sensors, an operation state for the four-wheel drive vehicle and a running state of the four-wheel drive vehicle are detected (S1). As the operation state, the shift position of the shift lever is detected based on the shift position signal Ss. Based on the accelerator position signal Sa, an operation state such as an accelerator pedal depression amount is detected. Based on the brake position signal Sb, an operation state such as an amount of depression of the brake pedal is detected. As the traveling state of the four-wheel drive vehicle, the rotational speed of each wheel 46 is detected based on the wheel speed signal Sr. Based on the weight signal Sw, the load applied to each wheel 46 is detected. Based on the acceleration signal Sac, the longitudinal acceleration of the vehicle is detected as a vertical G. Based on the yaw rate signal Sy, the rotational acceleration around the Z-axis of the vehicle (vehicle turning acceleration) is detected as a lateral G. Is detected by the yaw rate sensor and input to the controller.

  The control unit 50 calculates the required driving force and calculates the torque distribution of each wheel 46 according to the operation state and traveling state of the four-wheel drive vehicle obtained based on these detection signals. In the invention, the output limitation is considered from the various conditions in the fuel cell system as follows.

  First, the output restriction rate in the fuel cell stack 10 is calculated, and the output possible power value in the fuel cell is calculated (S2). For example, when the remaining amount of hydrogen gas charged in the hydrogen tank 11 is less than a certain value, the consumption of hydrogen gas must be reduced to maintain the cruising distance. In such a case, the output limit rate P1 of the amount of power generated by the fuel cell stack 10 is determined. When there is no reason for output limitation, P1 is set to 100%.

  In addition, as a condition for such output limitation, the output of the fuel cell may be similarly limited when the temperature of a high-pressure auxiliary machine such as a compressor or pump of the fuel cell system is higher than a predetermined temperature. This is because, if the temperature of these auxiliary machines deviates from the normal range, it causes malfunction and accelerates the breakage or deterioration of the motor.

Next, the output restriction rate for the secondary battery is calculated (S3).
FIG. 3 shows the charging characteristics of the secondary battery 40. As shown in FIG. 3, when the secondary battery is charged to near the maximum power capacity that can be charged, it enters an overcharged state, and when discharged to near the fully discharged state, it enters an overdischarged state. Either state is not preferable because it damages the battery or shortens its life. In this embodiment, the battery computer 51 manages the state of charge of the secondary battery 40, and the amount of charge, that is, the SOC value fluctuates in a control target range set with a margin for these overcharge regions and overdischarge regions. To be controlled.

  Here, when the amount of electric power supplied to the traction motor 45 is increased over a long period of time, or when the output limit is applied to the fuel cell, the entire amount of electric power generated from the fuel cell stack 10 is used. In order to make up for this, it may continue to output a large amount of power from the secondary battery. In such a case, a constant charge amount cannot be maintained even under the control of the battery computer 51, and the SOC value may deviate from the control target range. If it is determined that such a situation has occurred, an output limiting rate P2 for the secondary battery 40 is determined as shown in FIG. When there is no reason for output limitation, P2 is set to 100%.

  Subsequently, torque distribution, that is, power distribution is performed according to the traveling state at that time, and further, the output restriction rate is calculated for each motor based on the current value of each trunk motor 45 (S4 to S7).

  For each wheel 46, traction motor 45, and traction inverter 44, when there is a situation where power supply corresponding to the original torque distribution cannot be performed, that is, when there is an output restriction, an output restriction rate is calculated according to the degree. Each traction motor 45 has an appropriate drive current range, but a current that deviates from the normal range may flow for a certain time or longer due to a long-time high-load operation, an accident, or an abnormal state. If such a state is left unattended, the motor may be damaged or the life may be deteriorated. For this reason, the current value of each traction motor 45 is sequentially measured, and when the measured current value is larger than the predetermined value for a certain time, the output limiting rate for the traction motor 45 and the wheel 46 is calculated, and each motor Output restriction ratios P3 (P3fL, P3fR, P3rL, P3rR) are respectively determined. When there is no reason for output limitation, the output limitation rate P3 of each wheel is set to 100%.

  Alternatively, the coil temperature of each traction motor 45 and the temperature of the stator can be detected, and when these temperatures exceed a predetermined temperature, the output of the fuel cell may be limited. This is because if the temperature of each part of the traction motor deviates from the normal range, the malfunction is caused and the motor is damaged or deteriorated earlier.

  Next, based on the maps as shown in FIGS. 4A to 4C, an appropriate torque distribution calculation is performed for each wheel in a state in which the output restriction is not considered. The method for obtaining the torque for each wheel 46 is based on various known techniques. For example, the torque distribution for each wheel includes the height of the center of gravity of the four-wheel drive vehicle, the distance from the center of gravity to the front wheels, the distance from the center of gravity to the rear wheels, the width of the left and right wheels, the turning acceleration, that is, the lateral G value, the vertical direction It is calculated by the acceleration, that is, the vertical G value. Specifically, referring to the map shown in FIG. 4A, the torque distribution ratio T1 of each wheel is obtained from the torque command value corresponding to the required driving force of each wheel and the lateral G. Further, with reference to the map shown in FIG. 4B, the torque distribution ratio T2 is obtained from the yaw acceleration value. These are the distribution correction coefficients. This torque distribution ratio T is calculated by T = T1 × T2. 4C, torque distribution is determined from the load distribution of each wheel and the torque distribution ratio T.

Next, for the appropriate torque distribution, the permissible power for each wheel is obtained in consideration of the output limit rate calculated in steps S2 to S7, and the total permissible power is calculated. S8). Assuming that the maximum power value that can be output by each traction inverter 44 is P _MAX , for example, for the traction inverter 44 fL, the power value PafL that can actually be output is
PafL = P1 × P2 × P3fL × P _MAX (1);
It becomes. Similarly, the power values that can be output for other traction inverters are as follows:
PafR = P1 × P2 × P3fR × P _MAX (2);
ParL = P1 × P2 × P3rL × P MAX ... (3);
ParR = P1 × P2 × P3rR × P MAX ... (4);
Is calculated. Therefore, the power Pa that can be permitted to output in this output restriction state is the sum of the output permission power values for the four wheels,
Pa = PafL + PafR + ParL + ParR (5)
Can be calculated. The output permission power Pa cannot supply power that is higher than the output permission power Pa, that is, it is prohibited to supply an output that is higher than this value.

  Next, the required power Pr to be supplied with power in the fuel cell system is determined based on the operation state of the four-wheel drive vehicle obtained in step S1, for example, the amount of depression of the accelerator and the shift position of the shift lever (S9).

  If power can be supplied from the fuel cell system according to the required power Pr, traveling control according to the operation state and traveling state at that time can be performed. However, when the required power Pr exceeds the output permission power Pa, output according to the required power Pr cannot be performed. Therefore, first, the required power Pr for the system is compared with the output permission power Pa calculated from the output restriction condition (S10). When the required power Pr for the system is smaller than the output permission power Pa, there is no need to actually limit the output. For this reason, when the required power Pr for the system is smaller than the output permission power Pa (S10: NO), the torque is distributed according to the normal procedure without particularly restricting the output, and the power corresponding to the distributed torque is supplied to each traction. It is supplied to the inverter 44.

  On the other hand, when the required power Pr for the system is equal to or higher than the output permission power Pa, it is necessary to limit the output. Here, if the power supplied to each traction inverter 44 is limited in accordance with the output limiting rate and the torque generated in each motor 45 is reduced, inconvenience may occur. Generally, a vehicle is accelerated by generating a high torque on a heavily loaded wheel to generate a propulsive force. However, if the torque generated in each wheel 46 is reduced by a similar amount in accordance with the output restriction rate, the torque is reduced even in a wheel having a relatively high load. If the torque of a loaded wheel is reduced, the acceleration performance is significantly reduced.

  Therefore, in the present embodiment, control is performed so that more torque is generated by the wheel having a relatively high load. Here, in the four-wheel drive vehicle, it is assumed that the fuel cell system is housed in a storage portion in the forward direction of the vehicle, and the front wheel 46fL / R has a larger load than the rear wheel 46rL / R. In order to correctly measure the torque, functions that may cause the wheel operation to fluctuate irregularly, such as an anti-lock brake function or a traction control function, are stopped (S11). In this state, the amount of torque generated in each motor is measured by, for example, measuring the current amount of the traction motor 45. Then, it is compared whether the total torque amount of the rear wheels 46rL / R is larger than a predetermined torque amount (S12). The predetermined torque amount is a threshold value for preventing the torque amount at the rear wheel having a relatively small load from being excessive. When the torque amount of the rear wheel is smaller than the predetermined value (S12: NO), it is assumed that a sufficient torque amount is generated on the front wheel side, and the anti-lock brake function and the traction control function are restored, Allow the vehicle to travel with the amount of torque generated.

  On the other hand, when the torque amount of the rear wheel 46rL / R is equal to or greater than the predetermined value (S12: YES), it can be determined that the torque generated in the rear wheel with a small load is too large. Therefore, in such a case, while maintaining the total power supply, the power supplied to the rear-wheel traction inverter 44rL / R is reduced, and the power supplied to the front-wheel traction inverter 44fL / R is reduced. A calculation is performed to correct the torque distribution so as to increase the amount of torque generated in the front wheel 46fL / R relatively (S13). By this correction calculation, more torque can be distributed to wheels with relatively large loads. Extremely zero torque may be generated in the rear wheels. This is the same case as complete front-wheel two-wheel drive.

  FIG. 5 shows the torque distribution between the front wheels and the rear wheels in the torque distribution correction control performed in the processes of steps S10 to S13. As shown in FIG. 5, the rear-wheel torque Tr increases with the front-wheel torque Tf until the torque Tr generated at the rear-wheel reaches a predetermined value Tth (see step S12). The torque Tr reaches a peak, and only the front wheel torque Tf is increased, so that the driving force of the front wheels is controlled to increase. By making the torque of the front wheels larger than the torque of the rear wheels, it is possible to maintain the acceleration performance and prevent the driver from feeling uncomfortable due to a flaw between the accelerator pedal operation and the actual acceleration amount. Is possible.

  As described above, according to the first embodiment, when the output permission power Pa based on the output restriction is smaller than the required power Pr of the system, the correction calculation is performed within the range of power that can cover the torque supplied to the wheels.

  According to the first embodiment, even when the torque correction is performed according to the output restriction, the torque is corrected and distributed so that the torque of the rear wheel 46rL / R becomes a predetermined value or less. It is possible to prevent the driver from feeling uncomfortable in driving operation without lowering.

  Specifically, according to the first embodiment, the torque distribution of each wheel is determined according to the load distribution in each wheel, so that the acceleration performance can be enhanced.

  Further, according to the first embodiment, when the torque distributed to the front wheels and the rear wheels is grasped, the antilock brake function and / or the traction control function are stopped, so that correct torque distribution can be calculated.

(Embodiment 2)
The second embodiment relates to a four-wheel drive vehicle in which two motors, which are drive sources, are provided for front wheels and rear wheels.
FIG. 6 shows a system configuration diagram of the four-wheel drive vehicle in the present embodiment. In FIG. 6, the configuration of the fuel cell system is the same as that of the first embodiment shown in FIG.
As shown in FIG. 6, the power system 4 of the second embodiment includes a secondary battery 40, a high voltage converter 41, a low voltage converter 42, a low voltage system auxiliary machine 43, a front wheel traction inverter 44f / 44r, a traction motor 45f / 45r, A differential 47f / 47r and wheels 46fR, 46fL, 46rR, 46rL (hereinafter, represented by "wheel 46") are provided.

  The difference between the second embodiment and the first embodiment is that the first embodiment includes the traction inverter 44 and the traction motor 45 for each wheel, whereas the second embodiment has two for the front wheel and the rear wheel. The output of the motor 45 is divided by a differential 47f / 47r, and a set of a front wheel 46f and a rear wheel 46r is divided. Since other configurations are the same as those in the first embodiment, the description thereof is omitted.

  The operation in the second embodiment is performed similarly to the first embodiment (FIG. 2). The state of each system is detected (see S1 in FIG. 2), and the output limiting rate for the fuel cell system and the secondary battery 40 is calculated (see S2 and S3). The output limit for each wheel (see S4 to S7) is calculated separately for the front wheel and the rear wheel, instead of the output limit rate calculation performed separately for the four wheels of the first embodiment. In the calculation of the output permission power Pa (see S8), the output permission powers for the front wheels and the rear wheels are totaled. Subsequent processing, that is, the torque of the front wheel 46f and the rear wheel 46r is corrected and distributed so that the torque of the rear wheel 46r is equal to or less than the predetermined value Tth (see S9 to S13).

  According to the second embodiment, even in a system including two traction motors, torque distribution is performed as in the present invention.

(Modification)
The present invention is not limited to the above-described embodiment, and can be variously modified and applied.
In the said embodiment, although this invention was applied only to the four-wheel drive vehicle, it is not influenced by the number of wheels. The present invention can be similarly applied to a vehicle having four or more wheels as drive wheels, such as a two-wheel vehicle, a three-wheel drive vehicle, and a large vehicle. In other words, when it can be determined that the torque amount for the driving wheel with a heavy load is relatively small with respect to the original torque distribution, a correction operation for increasing the torque of the driving wheel may be performed. By performing such processing, it is possible to suppress a decrease in acceleration performance corresponding to the operation state.

  Further, in the above embodiment, the final output is specified by multiplying the separately calculated torque distribution by the output limit rate. Also good.

  Further, when calculating the torque distribution for each wheel, the torque distribution of each wheel may be weighted according to the magnitude of the load. This is because the object of the present invention can be achieved if control can be performed so that more torque can be generated on a relatively heavy wheel.

System configuration diagram of the four-wheel drive vehicle of Embodiment 1 The flowchart explaining the torque distribution process of embodiment Charging / discharging characteristics diagram explaining secondary battery output limitation Relationship diagram of lateral acceleration (lateral G), torque command value, and torque distribution ratio T1 Relationship diagram between yaw acceleration and torque distribution ratio T2 Relationship diagram between load distribution and torque distribution Relationship diagram between front wheel torque distribution Tf and rear wheel torque Tr System configuration diagram of a four-wheel drive vehicle of Embodiment 2

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel gas supply system, 2 ... Oxidation gas supply system, 3 ... Cooling system, 4 ... Electric power system, 5 ... Control system, 10 ... Fuel cell stack, 46fR, 46fL, 46rR, 46rL ... Wheel, 50 ... Control part

Claims (6)

A torque distribution device to each wheel for a moving body comprising a plurality of wheels,
When the power required for the system exceeds the output possible power of the power source of the system, the total torque distributed to each wheel is corrected so as not to exceed the output possible power, and the mobile body The torque distribution device is characterized in that the torque of each wheel is distributed so that the acceleration of the wheel can be maintained. A torque distribution device to each wheel for a moving body having a front wheel and a rear wheel,
Means for correcting the sum of the torques distributed to each wheel not to exceed the output power of the power source of the system when the power required for the system exceeds the output power of the power source of the system; ,
Means for distributing torque between the front wheel and the rear wheel so that the acceleration of the movable body can be maintained. A torque distribution device to each wheel for a moving body comprising a front wheel and a rear wheel,
A torque distribution device that distributes the torque of the front wheel and the rear wheel so that the torque of the rear wheel is less than or equal to a predetermined value when the torque distributed to each of the wheels is in an output limited state.   The torque distribution device according to any one of claims 1 to 3, wherein a distribution of torque of each wheel is determined according to a load distribution in each wheel.   The torque distribution device according to any one of claims 1 to 4, wherein an anti-lock brake function and / or a traction control function is stopped when grasping the torque distributed to the front wheels and the rear wheels. A torque distribution device to each wheel for a moving body comprising a plurality of wheels,
When the power required for the system exceeds the output power of the power source of the system,
The torque is corrected so that the total torque distributed to each wheel does not exceed the output power, and the torque distribution of each vehicle is determined according to the load distribution on each wheel. Dispensing device.

Images