JP4134960B2 - Drive control apparatus for hybrid vehicle - Google Patents

Description

  The present invention relates to a drive control apparatus for a hybrid vehicle that uses both an engine and a travel motor as a vehicle drive source.

Patent Document 1 discloses a hybrid vehicle that uses both an engine and a traveling motor as a vehicle propulsion source, and realizes motor traveling that mainly drives driving wheels by the motor and engine traveling that mainly drives driving wheels by the engine. It is disclosed.
JP 2001-112118 A

  A planetary gear mechanism having three rotating elements linked by gears is used, a generator is connected to the first rotating element, an engine is connected to the second rotating element, and power is transmitted between the third rotating element and the drive wheel. In a hybrid vehicle provided with a traveling motor and a transmission on the path and provided with a lock-up clutch that switches between fastening and releasing of the second rotating element and the third rotating element, by controlling the rotational speed of the generator, It becomes possible to control the engine speed to a high speed with high fuel efficiency.

  In such a hybrid vehicle, motor driving that mainly drives the drive wheels by a driving motor with the lock-up clutch released, and engine driving that drives the driving wheels mainly by the engine with the lock-up clutch engaged. It can be carried out. For example, when starting a vehicle from a state in which the engine is stopped (so-called idle stop), the vehicle is first started quickly by motor driving with the clutch released, and then the motor driving is started. Switch to engine running. At the time of the travel switching, the engine is driven by the generator to start the engine and the power running / regenerative operation by the generator is controlled to control the engine rotational speed toward a desired lockup target rotational speed. If the lock-up clutch is engaged when the rotation speed of the third rotating element reaches the lock-up target rotation speed due to the driving, the travel mode can be switched without a torque shock due to the engagement of the clutch.

  However, since the travel load at the time of start changes due to the gradient of the road surface (vehicle on the road surface), the degree of change in the vehicle speed during acceleration, that is, the rotational speed of the third rotating element connected to the travel motor and drive wheels The degree of change will be different. In particular, when the traveling motor is relatively small, this tendency appears greatly. For example, on a steep uphill with a large road gradient, the traveling load at the time of start is large, and the rise of the vehicle speed and the rotation speed of the third rotation element becomes gentle. Therefore, the third rotation is compared with the rise of the engine rotation speed. The rise of the rotational speed of the element is greatly delayed, and therefore the rotational speed difference between the two becomes large, the rotational speed of the generator linked by the planetary gear mechanism becomes excessively high, and the output and rating required for the generator (Physique) will be large. For this reason, there exists a possibility of causing the enlargement and weight increase of a generator.

  Furthermore, in such a situation where the traveling load (gradient) at the time of starting is large, the time until the rotation speed of the third rotation element reaches the lock-up target rotation speed becomes long and the lock-up clutch is engaged. As a result, the acceleration response decreases and energy loss due to the generator and the traveling motor increases, resulting in a decrease in fuel consumption. Increasing the rating (physique) of the generator and the traveling motor in order to shorten the time until the lockup clutch is engaged is not preferable because it increases the size and weight of the device.

  The present invention has been made in view of such a problem, and includes a differential gear device having two degrees of freedom and three elements, and on a collinear diagram showing a relationship between the rotational speeds of each element of the differential gear device. A generator and a traveling motor are connected to the elements on both sides, an engine is connected to the inner element, the element to which the traveling motor is connected is connected to a power transmission path that connects to the drive wheels, and each element In a hybrid vehicle drive control device having a lockup clutch that switches between an integrated state and a rotatable state with two degrees of freedom, when the vehicle is stopped with the engine stopped, the lockup clutch In the state where the motor is driven, the motor traveling means for driving the drive wheels by the traveling motor, and the generator at the time of traveling switching from the motor traveling to the engine traveling. And a traveling switching means for engaging the lockup clutch by controlling the engine rotational speed toward a predetermined lockup target rotational speed, and this traveling load is large according to the traveling load at the start of the vehicle As described above, the lockup target rotational speed is reduced.

  When starting the vehicle while the engine is stopped (during so-called idle stop), it is preferable to start the vehicle quickly by motor travel and then switch from motor travel to engine travel. During such travel switching, the engine speed is controlled and maintained at the lockup target rotational speed by the generator, and the rotational speed of the elements of the differential gear unit that is connected to the travel motor as the vehicle speed is increased by the travel motor. When the torque reaches the lockup target rotation speed, the lockup clutch may be engaged. However, since the torque of the traveling motor is limited, the degree of change in the vehicle speed and the number of rotations of the elements connected to the traveling motor, that is, the acceleration responsiveness differs depending on the traveling load caused by the road surface gradient or the like. It will be a thing. For this reason, for example, in a situation where the gradient is large and the traveling load is large such as a steep uphill, the increase in the rotational speed toward the lockup target rotational speed of the element connected to the traveling motor becomes gradual, Since the deviation from the engine speed becomes large, the speed of the generator linked by the differential gear unit becomes excessively high, and the output and physique (rated) required for the generator become large. There is a risk of increasing the size and weight of the machine. In the present invention, the lockup target rotational speed is reduced as the traveling load increases in accordance with the traveling load caused by the road surface gradient or the like. Therefore, the excessive increase in the rotational speed of the generator is effectively performed. It can be reduced and avoided, and the generator can be reduced in size and weight.

  FIG. 1 is a schematic configuration diagram illustrating a drive control apparatus for a hybrid vehicle according to an embodiment of the present invention. This device includes an engine 10 and a traveling motor 12 as a vehicle propulsion source, and also connects a generator 14, a planetary gear mechanism 16 as a differential gear device, a continuously variable transmission 18, and a pair of drive wheels 20. It has a shaft 22 and the like.

  As is well known, the engine 10 generates driving force by burning gasoline or light oil. Both the traveling motor 12 and the generator 14 are connected to a battery 24 via an inverter 26, and are a three-phase AC motor generator capable of both a power running operation and a regenerative operation. The battery 24 supplies power to the traveling motor 12 and the generator 14 and charges the power generated and regenerated by the traveling motor 12 and the generator 14. For example, during motor driving in which the driving wheel 20 is driven mainly by the driving motor 12, the DC electric energy of the battery 24 is converted into three-phase AC by the inverter 26, and the AC electric energy is converted into mechanical energy by the driving motor 12. Transmitted to the wheel shaft 22. During regenerative braking, mechanical energy transmitted from the engine 10 and the drive wheel 20 side is converted into three-phase AC energy by the motor 12, further converted into DC by the inverter 26, and charged to the battery 24.

  A planetary gear mechanism 16 as a two-degree-of-freedom three-element differential gear device includes a sun gear 16a as a first rotating element connected to the generator 14, and a ring gear 16b as a third rotating element connected to the drive wheel 20 side. The plurality of pinion gears 16c meshing with the outer periphery of the sun gear 16a and the inner periphery of the ring gear 16b, and the carrier as a second rotating element connected to the engine 10 while rotatably supporting the plurality of pinion gears 16c. 16d, and a lock-up clutch 28 that can mechanically fix the ring gear 16b and the carrier 16d.

  The continuously variable transmission 18 is a belt-type or toroidal-type automatic transmission whose gear ratio can be continuously changed in a range from the maximum (lowest) to the minimum (highest), and includes a ring gear 16 b and a drive wheel 20. It is provided in the power transmission path between. However, a known stepped transmission may be used instead of the continuously variable transmission.

  The travel motor 12 is provided in a power transmission path between the ring gear 16b and the continuously variable transmission 18, and is connected in series to the input shaft of the continuously variable transmission 18 in this embodiment. That is, the ring gear 16 b that is a gear element to which the traveling motor 12 is connected is coupled to a power transmission path that is connected to the drive wheels 20. The traveling motor 12 and the generator 14 function as motors when operating to increase rotation, that is, when outputting positive torque during positive rotation or when outputting negative torque during negative rotation. Power is consumed from the battery 24 via The traveling motor 12 and the generator 14 function as a generator when operating to reduce rotation, that is, when outputting negative torque during positive rotation, or when outputting positive torque during negative rotation, The battery 24 is charged via the inverter 26.

  The driving force necessary for running the vehicle is mainly output by the engine 10 and the motor 12. Typically, motor driving is performed using only the motor 12 as a vehicle propulsion source in an idle range, a low speed range, or a medium / high speed / low load range where the engine efficiency is not good, and the engine 10 is mainly used for vehicle propulsion in an operation range where the engine efficiency is good. When the engine driving is performed as a source and the required driving force of the vehicle cannot be obtained only by the output of the engine 10, electric power is supplied from the battery 24 to the motor 12 to drive the motor 12, and this motor torque Is added to the engine torque (assist). The motor 12 can recover the deceleration energy by performing a regenerative operation when the vehicle is decelerated, and can charge the battery 24 via the inverter 26 or can operate as a generator while the engine is running.

  Next, the operation of the planetary gear mechanism 16 will be described. When the number of teeth of the ring gear 16b is Zr, the number of teeth of the sun gear 16a is Zs, and the gear ratio between the ring gear 16b and the sun gear 16a is λ, the relationship is λ = Zs / Zr. When the rotational speed of the ring gear 16b is Nr, the rotational speed of the sun gear 16a is Ns, and the rotational speed of the carrier 16d is Nc, the relationship between the rotational speed and the gear ratio λ is expressed by the following equation (1).

Nr + λNs = (1 + λ) Nc (1)
2 and 3 are collinear diagrams showing the relationship between the rotational speeds of the elements of the planetary gear mechanism 16. On this alignment chart, the generator 14 and the traveling motor 12 are connected to the sun gear 16a and the ring gear 16b which are elements on both sides, respectively, and the engine 10 is connected to the carrier 16d which is an inner element. The ring gear rotation speed Nr corresponding to the input rotation speed of the continuously variable transmission 18 changes according to the vehicle speed and the transmission gear ratio of the continuously variable transmission 18. For example, the transmission gear ratio of the continuously variable transmission 18 is the same as during high speed travel. In a situation where it is kept to a minimum, it varies depending on the vehicle speed. Therefore, as shown in the collinear diagram of FIG. 2, by adjusting and controlling the rotational speed of the sun gear 16a (the rotational speed of the generator 14), the rotational speed of the carrier 16d, that is, the engine rotational speed can be changed with high accuracy. Can be controlled. When the two gears of the planetary gear mechanism 16 are fixed, Nr = Ns = Nc and the gear ratio is 1. Therefore, when the ring gear 16b and the carrier 16d are fastened by the lockup clutch 28, the three rotating elements 16a, 16b, and 16d constituting the planetary gear mechanism 16 rotate integrally.

  Referring to FIG. 1 again, this hybrid vehicle includes a known CPU, ROM, RAM, and input / output interface, and includes control devices 30 to 36 that store and execute various functions as programs. That is, the hybrid vehicle includes an engine control device 31 that performs engine control such as fuel injection control and ignition timing control, a motor control device 32 that controls the rotational speed and torque of the traveling motor 12 via the inverter 26, A generator control device 33 that controls the rotational speed and torque of the generator 14 via the inverter 26, a battery control device 34 that detects the state of charge of the battery 24, and the engagement / disengagement of the lock-up clutch 28 according to the vehicle running condition. A clutch control device 35 that performs switching control of opening and a transmission control device 36 that performs shift control of the continuously variable transmission 18 are provided. These control devices 31 to 36 are electrically connected to a vehicle control device 30 that comprehensively controls the operation of the vehicle. The vehicle control device 30 is shown in FIGS. 4 to 9 to be described later based on vehicle operating states detected from various sensors such as an accelerator opening sensor 37, a vehicle speed sensor 38, a rotation sensor 39, and a gradient detection sensor 40. A control routine such as this is executed. As is well known, the gradient detection sensor 40 detects the gradient of the road surface and the vehicle on the road surface or the gradient rate.

  4 to 9 are flowcharts showing a control flow according to the present embodiment. Referring to FIG. 4, in S (step) 1, the accelerator opening detected by accelerator opening sensor 37 is read. In S2, the vehicle speed detected by the vehicle speed sensor 38 is read. In S3, the battery charge state (SOC) detected by the battery control device 34 is read. In S4, the vehicle target output Preq is calculated. Specifically, first, a vehicle required drive output necessary for vehicle travel is obtained based on the accelerator opening and the vehicle speed. The vehicle required drive output is typically searched from a map prepared in advance using the accelerator opening and the vehicle speed as parameters. Also, the required power generation output of the battery is obtained from the SOC. For this required power generation output, for example, a numerical value set in advance for each SOC is used. The vehicle target output Preq is obtained by adding the power consumption of the auxiliary machine and the power train loss to the sum of the vehicle required drive output and the required power generation output.

  In S5, this Preq is compared with the motor travel permission output Ptable. The motor travel permission output Ptable is calculated by the vehicle control device 30 based on the rated characteristics of the motor 12 itself, the state of charge (SOC) of the battery 24, and the like. When Preq is larger than Ptable, the mode shifts to the engine travel mode (FIG. 6), and at least a predetermined motor travel condition including that Preq is equal to or less than Ptable, the mode shifts to the motor travel mode (FIG. 5).

  Note that the motor travels basically even during deceleration. However, the vehicle traveling speed may be limited according to the maximum rotation speed and the maximum output of the generator 14.

  The motor travel mode will be described with reference to FIG. In S6, it is determined whether the lockup clutch 28 is ON, that is, engaged. If it is in the engaged state, the process proceeds to S7 and the lockup clutch 28 is released. In S8, the target torque of the motor 12 is calculated based on the rotation speed of the motor 12 detected or estimated by a known rotation sensor or the like and the vehicle drive output. In S9, this target torque is commanded to the motor control device 32. In S10, the target (input) rotational speed of the continuously variable transmission 18 is set according to the target torque and the vehicle speed so that the motor 12 operates at an efficient rotational speed, and this is sent to the transmission control device 36. Command. In response to this command, the continuously variable transmission 18 is shift-controlled. If the generator 14 is in a no-load state during motor running (unless torque control or rotational speed control is performed), the rotation of the carrier 16d is caused by the friction of the engine 10 as shown in FIG. The number is maintained at 0 (zero), and the sun gear 16a rotates backward with respect to the ring gear 16b.

  The engine travel mode will be described with reference to FIG. In S11, the actual rotational speed rNe of the engine 10 detected by the rotation sensor 39 is read. In S12, the target engine speed tNe is calculated based on the vehicle required output Preq and a control map (not shown) indicating the best fuel consumption line of the engine set and stored in advance. That is, the engine target torque set based on the accelerator opening and the like is mapped on the best fuel consumption line of the map to set the target rotational speed tNe. In S13, it is determined whether or not the engine has been started, that is, whether or not the engine is generating power by igniting the fuel. If it has not started, it shifts to the engine start mode (see FIG. 7). If the engine has been started, the process proceeds to S14, and the target rotational speed tNe is commanded to the transmission control device 36 as the target input rotational speed of the continuously variable transmission 18. In S15, in response to the command, the transmission control device 36 starts the shift control of the continuously variable transmission 18 toward the target input rotational speed.

  For example, in a situation where the vehicle speed is low, by controlling the gear ratio of the continuously variable transmission 18, even if the lockup clutch 28 is engaged, the input rotational speed of the continuously variable transmission 18, that is, the ring gear rotational speed Nr is set as the target engine. The rotation speed tNe can be maintained. However, when the vehicle speed is high, etc., if the lockup clutch 28 is engaged, the ring gear rotational speed Nr can be reduced to the target engine rotational speed tNe even if the speed ratio of the continuously variable transmission 18 is set to the minimum. Can not. Therefore, in the present embodiment, the engagement / release of the lockup clutch 28 is switched based on the comparison between the target engine speed tNe and the ring gear speed Nr. Specifically, in S16, the ring gear rotation speed Nr is compared with the target engine rotation speed tNe. The ring gear rotation speed Nr may be detected directly using a known rotation sensor or the like, or the rotation speed of the traveling motor 12 may be substituted, or the vehicle speed and the speed change state of the continuously variable transmission 18 may be determined. Calculation and estimation may be performed based on the above. That is, in S15, the continuously variable transmission 18 is controlled so that the ring gear rotational speed Nr approaches the target engine rotational speed tNe, and then the process proceeds to S16 to determine whether the ring gear rotational speed Nr is equal to or higher than the target engine rotational speed tNe. Comparing. Therefore, the determination in S16 is that it is determined whether or not the ring gear rotation speed Nr when the speed ratio of the continuously variable transmission 18 is the minimum, that is, the lower limit value of the ring gear rotation speed Nr is equal to or greater than the target engine rotation speed tNe. In other words.

  When tNe is greater than or equal to Nr, that is, when the operating condition is such that the ring gear rotational speed Nr can be maintained at the target engine rotational speed tNe by controlling the transmission of the continuously variable transmission 18 even with the lockup clutch 28 engaged. When shifting to the planetary fixed mode (FIG. 8) in which the lock-up clutch 28 is engaged and tNe is lower than Nr, that is, with the lock-up clutch 28 still engaged, the ring gear rotation speed is maintained even if the continuously variable transmission 18 is controlled to shift. When the operating condition is such that Nr cannot be reduced to the target engine speed tNe, the operation mode shifts to the planetary differential mode (FIG. 9) in which the lockup clutch 28 is released.

  The engine start mode will be described with reference to FIG. For example, when accelerating from an idle operation range or an extremely low load range, the motor travel mode is shifted to the engine start mode. While the motor is running, the lock-up clutch 28 is opened to reduce engine friction. Therefore, if the generator 14 is in a no-load state, the engine speed is maintained at almost 0 (zero) by engine friction. ing. Therefore, as is clear from the above formula (1) and FIG. 3A, the generator 14 is negatively rotated (reversely rotated with respect to the ring gear 16b). The actual rotational speed of the generator can be obtained from, for example, the ring gear rotational speed Nr and the engine rotational speed rNe. In order to ignite and start the engine 10, it is necessary to increase the engine speed to the engine startable speed Nestart (for example, 600 rpm). A target rotational speed of the generator corresponding to the engine startable rotational speed Nestart is calculated, and a target torque of the generator is calculated based on a difference between the target rotational speed and the actual rotational speed of the generator. The torque is commanded to the generator control device 33 (S17). As a result, the generator is controlled to increase the speed in the forward rotation direction, and the engine speed increases toward Nestart. Thus, in the process of increasing the engine speed toward Nest, typically, the target torque of the generator is always positive torque, and the generator shifts from negative rotation to positive rotation. When the power is being generated, the battery is generating power, and the battery is charged with power. When the battery is rotating in the forward direction, power is consumed from the battery. In S18, the actual engine speed rNe is compared with Nestart. When rNe reaches Nestart, engine start (fuel supply and spark ignition) is started (S19). A nomographic chart of a typical engine start mode is shown in FIG. 3 (B ′) → (B).

  The planet fixed mode will be described with reference to FIG. In S20, it is determined whether the lockup clutch 28 is in the engaged state (ON) or in the released state (OFF). If the clutch 28 is ON, an engine target torque tTe is calculated from the vehicle request output and the actual engine speed rNe (S24), and this target torque tTe is commanded to the engine control device 31 (S25). When the clutch is thus engaged, the output of the engine 10 is directly transmitted to the generator 14 and the drive wheel 20 side. When the engine target torque tTe is larger than the engine maximum torque Temax, the motor 12 assists the insufficient torque (tTe−Temax) if possible. When tTe is larger than the target drive output tTd, the surplus torque (tTd−tTe) is regenerated by one or both of the generator 14 and the motor 12.

  If it is determined in S20 that the clutch is in the released state, the process proceeds to S21A. In S21A, based on the gradient detected by the gradient detection sensor 40, the setting map shown in FIG. 10 is referenced to calculate and set the lockup target rotation speed Neup (lockup target rotation speed setting means). In other words, the lockup target rotational speed Neup is changed according to the road surface gradient. Specifically, as shown in FIG. 10, the lockup target rotational speed increases as the gradient increases (that is, the uphill becomes steep). Neup is increased. In S21B, the target torque (or target speed) of the generator 14 is calculated so that the actual engine speed rNe becomes the lockup target speed Neup based on the lockup target speed Neup. In S21C, this target torque (or target rotation speed) is commanded to the generator control device 33. Thereby, operation | movement of the generator 14 is controlled toward target torque (or target rotation speed).

  In subsequent S22, it is determined whether the actual engine speed rNe is equal to the ring gear speed Nr, or whether the deviation between the two is less than a predetermined value. For example, when switching from motor running to engine running during acceleration from an idle or low speed range, the engine speed is quickly increased to the lockup target speed Neup by the generator 14 by the processing of S21A to S21C described above. Then, with the engine speed maintained in the vicinity of the lockup target speed Neup, the ring gear speed Nr increased to the lockup target speed Neup as the vehicle speed increased by driving the motor 12. At the time, rNe and Nr are almost equal.

  If it is determined in S22 that rNe and Nr are substantially equal and the lockup clutch 28 can be smoothly engaged, the process proceeds to S23, and the lockup clutch 28 is engaged. After the clutch is engaged, as described above, the engine target torque tTe is calculated from the vehicle request output and the actual engine speed rNe (S24), and this target torque tTe is commanded to the engine control device 31 (S25). After the lockup clutch 28 is engaged, the continuously variable transmission 18 is controlled so that the ring gear rotation speed Nr approaches the target engine rotation speed tNe. A typical alignment chart of this planetary fixed mode is shown in FIGS. 3 (C) and 3 (D).

  With reference to FIG. 9, the planetary differential mode will be described. First, the state of the lock-up clutch 28 is detected. If the clutch 28 is engaged, the process proceeds from S26 to S27, and the clutch 28 is quickly released. In S28, the target rotational speed (or target torque) of the generator is calculated based on the difference between the target engine rotational speed tNe and the ring gear rotational speed Nr, and this target rotational speed (or target torque) is sent to the generator control device 33. The generator is commanded to control the rotational speed (or torque control) of the generator. Alternatively, the target torque of the generator is calculated from tNe and rNe, and this target torque is commanded to the generator control device 33. In this planetary differential mode, since tNe is smaller than rNe, the target torque of the generator is negative torque, the generator 14 is decelerated and the battery 24 is charged. Therefore, even if the SOC of the battery 24 is low, this routine can be executed. In S29, a target torque of the engine is calculated from the vehicle request output and rNe, and this target torque is commanded to the engine control device (S30). A typical alignment chart of this planetary differential mode is shown in FIGS.

  FIG. 11 is a time chart when starting the vehicle while the vehicle is stopped with the engine 10 stopped, that is, in an idle stop state such as waiting for a signal. At the time of starting from such an idle stop, first, the vehicle is promptly started in the motor driving mode in which the lock-up clutch 28 is released, the engine 10 is started by the generator and the lock-up clutch 28 is fastened. Transition from mode to engine running mode. In FIG. 11, (A) corresponds to the case where the gradient is small (for example, the gradient rate is 0%) and (B) and (C) are large (for example, the gradient rate is 30%). .

  First, in the motor travel until the time Tup at which the lockup clutch 28 is engaged, the drive wheels 20 are driven by the motor 12 and the vehicle speed and the transmission input rotational speed, that is, the rotational speed Nr of the ring gear that is the third gear element. Is gradually increased, the engine 10 is started by the generator 14 and the engine speed is controlled toward the lockup target speed Neup. When a motor 12 having a general rating is used, since the increase in the ring gear rotation speed Nr by the motor 12 is usually delayed as compared with the increase in the engine rotation speed, the engine rotation speed quickly reaches the lockup target rotation speed Neup. The lockup clutch 28 is engaged when the transmission input rotational speed Nr reaches the lockup target rotational speed Neup while maintaining the lockup target rotational speed Neup.

  The degree of increase in the transmission input rotational speed Nr varies depending on the traveling load such as the road surface gradient. Specifically, as the road surface gradient, that is, the traveling load increases, the increase in the transmission input rotational speed Nr becomes more gradual. Therefore, as shown in FIG. 10B, if the lockup target rotational speed is set to the same value Neup1 as when the slope is low (A), the deviation ΔN between the engine rotational speed and the transmission input rotational speed becomes large. The rotational speed (sun gear rotational speed) Ns of the generator 14 becomes excessively high. In general, the output and torque tend to decrease greatly as the rotational speed of the generator 14 increases. Therefore, when the rotational speed of the generator 14 increases, the rating required for the generator 14 increases, It will increase the weight. In addition, since the timing Tup for fastening the lockup clutch 28 is delayed, the energy loss of the generator 14 and the motor 12 is increased, and the acceleration response is reduced.

  On the other hand, in this embodiment, as shown in FIG. 10C, the lockup target rotation speed Neup2 is lowered (smaller) as the gradient increases, that is, as the traveling load increases. Therefore, the deviation ΔN between the engine speed and the transmission input speed is suppressed low, and an excessive increase in the speed Ns of the generator 14 is suppressed. Therefore, the output and rating of the generator 14 can be suppressed low, and the generator 14 can be reduced in size and weight. Further, the timing Tup for fastening the lockup clutch 28 is accelerated, energy loss is suppressed, and acceleration performance is improved.

  For example, in a situation where the gradient is small as shown in FIG. 10 (A), if the lockup target rotational speed Neup2 is set low as in the case where the gradient is large as shown in FIG. 10 (C), the engine speed is reduced. The ring gear rotation speed Nr may reach the lockup target rotation speed Neup before being stably maintained at the lockup target rotation speed Neup, and there is a possibility that the lockup clutch 28 cannot be properly engaged. In this embodiment, since the lockup target rotational speed Neup is set in accordance with the gradient, the lockup clutch 28 can be tightened smoothly and quickly, and an excessive increase in the generator 14 can be suppressed. It is.

  More preferably, the input power to the battery 24 may be limited depending on the coil temperature of the generator 14 and the state of charge (SOC) of the battery. Therefore, the higher the coil temperature and SOC, the lower the lockup target rotation speed Neup. . As a result, the lockup target rotational speed Neup can be further optimized, and the generator 14 can be further reduced in size and weight.

  The technical ideas of the present invention that can be grasped from the above description are listed below. However, the present invention is not limited to the configuration of the illustrated embodiment with reference numerals, and includes various modifications and changes without departing from the spirit of the present invention.

(1) It includes a differential gear device 16 having two degrees of freedom and three elements,
On the alignment chart showing the rotational speed relationship of each element 16a, 16b, 16d of the differential gear device, the generator 14 and the traveling motor 12 are connected to the elements 16a, 16b on both sides, respectively, and the inner element 16d is connected. The engine 10 is connected to the power transmission path connecting the driving wheel 20 to the element 16b to which the traveling motor 12 is connected,
And it has the lockup clutch 28 which switches the state which integrated each element and the state which can be rotated maintaining 2 degrees of freedom.

Motor traveling means for performing motor traveling mainly driving the driving wheels 20 by the traveling motor 12 in a state in which the lock-up clutch 28 is released when the vehicle 10 is stopped and the engine 10 is stopped.
Travel switching means for controlling the engine speed toward the predetermined lockup target speed Neup by the generator 14 and fastening the lockup clutch 28 at the time of travel switching from the motor travel to the engine travel; Have
In accordance with the travel load at the start of the vehicle, the lockup target rotation speed Neup is reduced as the travel load increases.

  (2) More preferably, as shown in FIG. 10, the lockup target rotational speed Neup is decreased as the gradient increases.

  (3) More preferably, the lockup target rotational speed Neup is decreased as at least one of the coil temperature of the generator 14 and the charged amount of the battery 24 increases.

  (4) More specifically, as shown in FIG. 11, when switching from the motor running to the engine running during vehicle start acceleration, the engine 10 is started by the generator 14 and the engine speed rNe is locked to the target rotation. When the rotational speed Nr of the element connected to the traveling motor by the traveling motor 12 reaches the lockup target rotational speed Neup, the lockup clutch 28 is engaged.

  (5) Typically, the differential gear device is a planetary gear mechanism 16, and the three elements are a carrier 18d and a ring gear 16b that support a sun gear 16a and a planetary gear 16c.

  In this case, as shown in FIG. 11, the rotation of the generator 14 linked by the planetary gear mechanism 16 increases as the deviation ΔN between the engine speed and the ring gear speed increases during the motor travel before the clutch engagement Tup. The number increases (see FIGS. 2 and 3). According to the present invention, by changing the lockup target rotational speed Neup in accordance with the road surface gradient, the deviation ΔN can be suppressed, and an excessive increase in the rotational speed of the generator 14 can be suppressed.

(6) a differential gear device 16 including a first rotating element 16a, a second rotating element 16d, and a third rotating element 16b;
A generator 14 connected to the first rotating element 16a;
An engine 10 connected to the second rotating element 16d;
A traveling motor 12 provided in a power transmission path between the third rotating element 16b and the drive wheel 20;
A lock-up clutch 28 for switching between fastening and releasing of the second rotating element 16d and the third rotating element 16b;
Motor traveling means (FIG. 5) for performing motor traveling mainly driving the driving wheels by the traveling motor 12 with the lock-up clutch 28 opened;
Engine traveling means (FIG. 8) for performing engine traveling mainly driving the drive wheels by the engine 10 in a state where the lock-up clutch 28 is engaged;
Lockup target rotation speed setting means (S21A in FIG. 8) for setting the lockup target rotation speed Neup;
At the time of travel switching from the motor travel to the engine travel, travel switching means for controlling the engine speed rNe toward the lockup target speed Neup by the generator 14 and fastening the lockup clutch 28 (FIG. 8). S21B, S21C and S22),
Gradient detecting means (gradient detection sensor 40) for detecting the gradient of the road surface,
The lockup target rotation speed setting means changes the lockup target rotation speed in accordance with the road surface gradient (see FIG. 10).

1 is a schematic configuration diagram illustrating a vehicle torque control device according to an embodiment of the present invention. The alignment chart of the planetary gear mechanism which concerns on a present Example. The alignment chart of the planetary gear mechanism which similarly concerns on a present Example. A part of flowchart which shows the flow of control of a present Example. A part of the flowchart showing the processing contents of the motor running mode. A part of the flowchart showing the processing contents of the engine running mode. A part of the flowchart showing the processing contents of the engine start mode. A part of the flowchart showing the processing contents of the planetary fixed mode. A part of the flowchart showing the processing contents of the planetary differential mode. An example of the setting map of lockup target rotation speed. The time chart at the time of the vehicle acceleration which switches from motor driving | running | working to engine driving | running | working.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Engine 12 ... Motor for driving | running | working 14 ... Generator 16 ... Planetary gear mechanism (differential gear apparatus)
16a ... Sun gear (first rotating element)
16b ... Ring gear (third rotating element)
16d ... Carrier (second rotating element)
DESCRIPTION OF SYMBOLS 18 ... Continuously variable transmission 20 ... Drive wheel 24 ... Battery 28 ... Lock-up clutch 40 ... Gradient detection sensor (gradient detection means)

Claims (4)

A two-degree-of-freedom three-element differential gear device,
On the collinear chart showing the relationship between the rotational speeds of each element of this differential gear unit, the generator and traveling motor are connected to the elements on both sides, the engine is connected to the inner element, and the traveling motor is connected Connected to the power transmission path connected to the drive wheels,
And in the drive control device of a hybrid vehicle having a lock-up clutch that switches between a state in which each element is integrated and a state in which it can rotate while maintaining two degrees of freedom,
Motor traveling means for performing motor traveling mainly driving the driving wheels by the traveling motor in a state in which the lock-up clutch is released when starting with the engine stopped when the vehicle is stopped;
Travel switching means for controlling the engine speed toward a predetermined lockup target rotational speed by the generator and fastening the lockup clutch at the time of travel switching from the motor travel to the engine travel;
The travel switching means starts the engine by the generator and maintains the engine speed at the lock-up target rotational speed when switching from the motor travel to the engine travel during vehicle start acceleration, and the travel motor When the rotational speed of the element of the differential gear device connected to the traveling motor reaches the lockup target rotational speed, the lockup clutch is engaged,
A drive control apparatus for a hybrid vehicle, characterized in that the lockup target rotational speed is decreased as the traveling load increases in accordance with the traveling load at the time of starting the vehicle. Having a slope detecting means for detecting the slope of the road surface;
2. The drive control apparatus for a hybrid vehicle according to claim 1, wherein the lockup target rotational speed is decreased as the gradient increases.   3. The drive control apparatus for a hybrid vehicle according to claim 1, wherein the lockup target rotation speed is decreased as at least one of the coil temperature of the generator and the amount of electricity stored in the battery increases. A said differential gear unit is a planetary gear mechanism, the three elements a sun gear, a carrier for supporting the planetary gears, and a drive control apparatus for a hybrid vehicle according to any one of claims 1 to 3, characterized in that the ring gear .