JP2012179999A - Engine starting control device of hybrid vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately control driving force fluctuation by torque control of a motor-generator even if the ignition of the engine is delayed, when the engine is started by cranking by connecting a K0 clutch.SOLUTION: When connecting the K0 clutch 34 and cranking and starting the engine 12, the slip control of the K0 clutch 34 is carried out so that a rotation speed difference ΔN may become a target rotation speed difference tΔN, and the slip control is continued even when the ignition of engine 12 is delayed in order to end the slip control when the bootstrap rotation of the engine 12 is detected and the K0 clutch 34 is connected completely. Therefore, the driving force fluctuation by the rotational resistance torque by the friction torque etc. can be appropriately controlled by the torque compensation of the motor generator MG regardless of the variation of the ignition timing of engine 12 by carrying out the torque compensation by the motor generator MG according to an oil pressure command value SPK0 of the K0 clutch 34.

Description

  The present invention relates to an engine start control device of a hybrid vehicle, and more particularly to an improvement of an engine start control device that starts an engine by cranking an engine by engaging a hydraulic friction clutch.

  Engine start control for cranking and starting the engine by engaging the hydraulic friction clutch with respect to a hybrid vehicle having an engine connected to a power transmission path via a hydraulic friction clutch and a motor generator The device is known. The device described in Patent Document 1 is an example, and an engine and a motor generator are connected via a first clutch (corresponding to the hydraulic friction clutch), which is closer to the driving wheel than the motor generator. By slipping the second clutch, the engine is cranked by engaging the first clutch while suppressing fluctuations in the driving force when starting the engine. Further, in Patent Document 2, negative torque due to friction torque or the like when cranking the engine is compensated by torque control of the motor generator to suppress fluctuations in driving force.

JP 2007-314097 A JP 2009-227277 A

  However, when the engine is started by slip-controlling the second clutch as in Patent Document 1, the thermal load of the second clutch is large and durability becomes a problem. On the other hand, when the driving force fluctuation is suppressed by torque control of the motor generator as in Patent Document 2, the engine torque is based on the estimated torque including, for example, when the engine is ignited even after the friction clutch for cranking the engine is completely engaged. It is conceivable to compensate the torque with the motor generator until the engine stabilizes.However, if the ignition of the engine is delayed during cold weather, etc., the difference between the estimated torque and the actual torque will increase, and the torque compensation by the motor generator will not be performed properly. There is a possibility that a shock will occur.

  FIG. 5 is an example of a time chart for starting the engine 12 by cranking the engine 12 with the K0 clutch 34 engaged in the hybrid vehicle 10 of FIG. 1, and the estimated engine torque sTE indicated by a dashed line in the engine torque column. Is set based on a change in engine torque when the engine 12 is properly ignited. Torque compensation is performed by the motor generator MG based on the estimated engine torque sTE. However, when the engine 12 does not ignite properly and the engine torque TE changes as shown by a solid line, for example, the actual engine torque TE and Around time t3 when the deviation from the estimated engine torque sTE becomes large, there is a possibility that a large shock may occur by torque compensation by the motor generator MG.

  The present invention has been made against the background of the above circumstances, and the object of the present invention is when the ignition of the engine is delayed when the engine is cranked and started by engaging a hydraulic friction clutch. However, it is to be able to appropriately suppress fluctuations in driving force by controlling the torque of the motor generator.

  To achieve this object, the first invention relates to a hybrid vehicle having an engine connected to a power transmission path via a hydraulic friction clutch and a motor generator, and engaging the hydraulic friction clutch. In the engine start control device that starts cranking and cranking the engine and suppresses fluctuations in driving force at the start of the engine by torque control of the motor generator, (a) the hydraulic friction clutch is disposed in an oil bath state. (B) detecting the rotational speed difference before and after the hydraulic friction clutch, and controlling the hydraulic friction by hydraulic control so that the engine-side rotational speed becomes a predetermined target rotational speed difference. Slip control means for cranking the engine while controlling the engagement torque of the clutch; and (c) detecting the self-rotation of the engine The exit pressure control by the slip control means, characterized by having a, a slip control ending process means for completely engage the hydraulic friction clutch oil pressure is increased in the hydraulic friction clutches.

  According to a second aspect of the present invention, in the engine start control device for a hybrid vehicle according to the first aspect, (a) the hydraulic friction clutch is disposed in an oil bath in a torque converter, and (b) the slip control means includes: Feedback obtained based on a feedforward value ff corresponding to a predetermined torque smaller than the rotational resistance torque of the engine when cranking the engine and a deviation between the target rotational speed difference and the actual rotational speed difference The hydraulic pressure command value SPK0 is obtained by adding the value fb, and hydraulic control of the hydraulic friction clutch is performed according to the hydraulic pressure command value SPK0.

  According to a third aspect of the present invention, in the engine start control device for a hybrid vehicle according to the second aspect of the invention, the slip control end processing means has a predetermined value (ff−fb) obtained by subtracting the feedback value fb from the feedforward value ff. The self-rotation of the engine is detected when the determination value is equal to or greater than Cs.

  In such an engine start control device for a hybrid vehicle, when the hydraulic friction clutch is engaged and the engine is cranked and started, the slip control means causes the rotational speed difference between the front and rear of the hydraulic friction clutch to be a predetermined value. The hydraulic control is performed so that the target rotational speed difference is obtained, and when the self-rotation of the engine is detected, the hydraulic control by the slip control means is terminated, and the hydraulic pressure is increased to fully engage the hydraulic friction clutch. Therefore, the hydraulic control by the slip control means is continued even when the ignition of the engine is delayed during cold weather or the like. For this reason, for example, by performing torque control (torque compensation) by the motor generator according to the hydraulic pressure command value of the hydraulic friction clutch by the slip control means, the friction torque, pumping loss, etc., regardless of variations in the ignition timing of the engine Driving force fluctuation due to engine rotational resistance torque can be appropriately suppressed by torque compensation of the motor generator. Further, since the hydraulic friction clutch is disposed in an oil bath state, the thermal load is reduced, and sufficient durability can be obtained even in a slip state having a predetermined rotational speed difference.

  In the second invention, the feedforward value ff corresponding to a predetermined torque smaller than the rotational resistance torque of the engine is added to the feedback value fb obtained based on the deviation between the target rotational speed difference and the actual rotational speed difference. Thus, the hydraulic pressure command value SPK0 is obtained, and the hydraulic pressure control of the hydraulic friction clutch is performed according to the hydraulic pressure command value, so that the hydraulic friction clutch quickly enters a slip state having a predetermined rotational speed difference based on the feedforward value ff. Be controlled. That is, the hydraulic friction clutch arranged in the oil bath state in the torque converter needs to push away the hydraulic oil to be frictionally engaged, resulting in poor responsiveness, but the feedforward value ff is set. Thus, the engine can be started quickly by shifting to a predetermined slip state.

  Further, since the feedforward value ff corresponds to a predetermined torque smaller than the rotational resistance torque of the engine, it is suppressed that the hydraulic friction clutch is completely engaged during the slip control and a shock is generated. In particular, since the hydraulic friction clutch is disposed in the torque converter in an oil bath, it is affected by the circulating pressure of the torque converter, and the engagement torque changes due to fluctuations in the circulating pressure. By defining a feedforward value ff corresponding to a predetermined torque smaller than the torque, complete engagement is appropriately suppressed. Although complete engagement is also suppressed by feedback control, there is a possibility of complete engagement when the influence of the circulation pressure is large, and complete engagement becomes difficult if the target rotational speed difference is increased. There is a possibility that the engine rotation speed becomes low at the vehicle speed and the engine cannot be started.

  In the third aspect of the invention, since the value obtained by subtracting the feedback value fb from the feedforward value ff (ff−fb) is equal to or greater than the predetermined ignition determination value Cs, the engine self-rotation is detected. The self-rotation can be accurately detected and the hydraulic friction clutch can be completely engaged. By accidentally engaging the clutch, it is possible to prevent the torque compensation by the motor generator from becoming incompatible and causing fluctuations in the driving force. That is, when the engine rotation speed increases and the engine rotation speed increases, the rotation speed difference becomes smaller than the target rotation speed difference and the feedback value fb becomes negative, so the (ff−fb) value increases. Based on this (ff−fb) value, it is possible to reliably detect the self-rotation due to the ignition of the engine.

It is the schematic block diagram which showed the principal part of the control system | strain in addition to the main point figure of the hybrid vehicle to which this invention is applied suitably. It is a block diagram of the hydraulic circuit regarding the K0 clutch with which the hydraulic control apparatus of FIG. 1 is provided. It is a control block diagram explaining the hydraulic control (slip control) by the slip control means functionally provided in the electronic control unit of FIG. 2 is a flowchart for specifically explaining signal processing by slip control means functionally included in the electronic control device of FIG. 1. The time which shows the change of K0 clutch oil pressure command value, engine torque, and the rotational speed of each part at the time of engaging the K0 clutch and starting the engine by the engine start control means functionally provided in the electronic control unit of FIG. It is an example of a chart.

  The engine generates power by combustion of fuel, and is cranked by being connected to a power transmission path via a hydraulic friction clutch, and is started by starting control such as fuel supply and ignition. The hydraulic friction clutch is a single-plate or multi-plate clutch that is frictionally engaged by a hydraulic cylinder, and is used in an oil bath state in a torque converter or the like. The engine is connected to, for example, a power transmission path in which a motor generator is disposed, and is configured to rotationally drive a common drive wheel, and is disposed so as to be directly connected to the motor generator by a hydraulic friction clutch. The power transmission path (for example, the rear wheel drive side) on which the motor generator is disposed may be disposed on a different power transmission path (for example, the front wheel drive side). The motor generator can be used as a generator by performing regenerative control (also referred to as power generation control), and can also be used as an electric motor by performing power running control.

  The torque control of the motor generator to suppress the driving force fluctuation at the time of engine start is to reduce the driving force fluctuation, and is synonymous with absorbing or compensating the driving force fluctuation. Say. The driving force fluctuation suppressing means for performing the torque control may control the torque of the motor generator according to the engagement torque of the hydraulic friction clutch while the hydraulic friction clutch is slip controlled by the slip control means. For example, the control may be performed based on the hydraulic pressure command value of the hydraulic cylinder. After the engine is ignited and the hydraulic friction clutch is completely engaged by the slip control end processing means, the torque of the motor generator may be controlled in accordance with the engine torque, for example, a predetermined estimated idle torque or the like. Control may be based on this.

  The slip control means does not immediately perform slip control of the hydraulic friction clutch when an engine start request is made, but is preferably performed following the first fill that quickly supplies hydraulic oil to the hydraulic cylinder. Since the engine has a larger overpass torque when compressing the first cylinder than the rotational resistance torque due to friction torque, etc., the first fill is continued until a predetermined rotation judgment value is exceeded so that the overpass torque can be passed. When the rotation determination value is exceeded, it is desirable to shift to slip control. When the hydraulic friction clutch is placed in an oil bath, the response of the engagement torque is poor, so if the engine speed is increased sufficiently and then the control shifts to the slip control, a complete engagement may occur and a shock may occur. There is sex. For this reason, by shifting to slip control in a relatively low rotation state where the above overcoming torque can be passed, a slip state in which the engine rotation speed is rapidly increased and a predetermined target rotation speed difference is obtained while avoiding complete engagement. Can be taken quickly.

  The target rotational speed difference is set to a constant value of, for example, about 100 to several hundred rpm in consideration of the feedback control gain and the circulating pressure of the torque converter so that the hydraulic friction clutch is not completely engaged. However, the rotational speed on the power transmission path side can also be set as a parameter so that the engine can be started. For example, when an engine is connected to a motor generator via a hydraulic friction clutch, the target rotational speed is set so that a predetermined engine rotational speed can be secured when the rotational speed is low with the rotational speed of the motor generator as a parameter. The difference may be reduced.

  The hydraulic control (slip control) of the hydraulic friction clutch by the slip control means is preferably performed according to the hydraulic command value SPK0 obtained by adding the feedforward value ff and the feedback value fb as in the second invention, for example. In carrying out the first invention, it is possible to perform hydraulic control only with the feedback value fb. In the second invention, the feedforward value ff is determined based on a predetermined torque smaller than the rotational resistance torque of the engine at the time of cranking the engine. A feed forward value ff corresponding to substantially the same engagement torque as the resistance torque may be used. The feedforward value ff and the feedback value fb of the second invention may relate to the engagement torque of the hydraulic friction clutch, but are determined based on the pressure receiving area of the hydraulic shilling according to the engagement torque. It may be related to the engagement hydraulic pressure.

  The slip control end processing means raises the hydraulic pressure of the hydraulic friction clutch to fully engage when detecting the self-rotation of the engine, but in order to prevent shock due to sudden engagement, the rotational speed of the hydraulic friction clutch before and after It is desirable to increase the hydraulic pressure at a predetermined rate of change until they substantially coincide (synchronize), and to increase to the maximum pressure at once when synchronized.

  Self-rotation of the engine can be detected when the value (ff−fb) obtained by subtracting the feedback value fb from the feedforward value ff is equal to or greater than a predetermined ignition determination value Cs as in the third aspect of the invention. Since it is mainly the feedback value fb that changes due to the increase in the engine rotational speed due to rotation, whether or not the feedback value fb has become a predetermined negative value or less, or the rotational speed difference before and after the hydraulic friction clutch is itself. It is also possible to detect whether or not the value has become a predetermined value or less.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic configuration diagram including a skeleton diagram of a drive system of a hybrid vehicle 10 to which the present invention is preferably applied. This hybrid vehicle 10 includes, for example, an engine 12 that is an internal combustion engine such as a gasoline engine or a diesel engine, and a motor generator MG that functions as an electric motor and a generator. The outputs of the engine 12 and the motor generator MG are transmitted from the torque converter 14 which is a fluid transmission device to the transmission 20 via the turbine shaft 16 and the C1 clutch 18, and further, the output shaft 22 and the differential gear device. 24 to the left and right drive wheels 26. The torque converter 14 includes a lock-up clutch 30 that directly connects the pump impeller and the turbine impeller, and an oil pump 32 is integrally connected to the pump impeller, and the engine 12 and the motor generator MG It is designed to be mechanically rotated. The transmission 20 is a stepped or continuously variable automatic transmission that is shifted by hydraulic pressure, and shift control is performed by an electromagnetic hydraulic control valve, a switching valve, or the like provided in the hydraulic control device 28. The C1 clutch 18 functions as an input clutch of the transmission 20 and is similarly controlled to be disengaged by the hydraulic control device 28.

  Between the engine 12 and the motor generator MG, there is provided a K0 clutch 34 that directly couples them together via a damper 38. This K0 clutch 34 is a single-plate or multi-plate hydraulic friction clutch that is frictionally engaged by a hydraulic cylinder 36 (see FIG. 2). From the viewpoint of cost, durability, etc., oil is placed in the oil chamber 40 of the torque converter 14. It is arranged in a bath state. Motor generator MG is connected to battery 44 via inverter 42.

  The hydraulic control device 28 includes the hydraulic circuit 50 of FIG. 2 for controlling the K0 clutch 34, and the hydraulic pressure output from the hydraulic supply source 52 having the oil pump 32 and the like is controlled by an electromagnetic hydraulic control valve 54. By adjusting the pressure, the K0 clutch hydraulic pressure PK0 supplied to the hydraulic cylinder 36 is controlled, and the engagement torque (K0 clutch torque) TK0 of the K0 clutch 34 is controlled according to the K0 clutch hydraulic pressure PK0. The hydraulic control valve 54 is controlled according to the hydraulic pressure command value SPK0 of the K0 clutch hydraulic pressure PK0 output from the electronic control unit 60.

  The electronic control unit 60 includes a so-called microcomputer having a CPU, a ROM, a RAM, an input / output interface, and the like, and performs signal processing according to a program stored in the ROM in advance using the temporary storage function of the RAM. Do. The electronic control device 60 is supplied with a signal representing the rotational speed (engine rotational speed) NE of the engine 12 from the engine rotational speed sensor 46 and from the MG rotational speed sensor 48 to the rotational speed (MG rotational speed) of the motor generator MG. ) A signal representing NMG is provided. In addition, various information necessary for various controls such as the required output amount such as the accelerator operation amount, the rotational speed of the turbine shaft 16 (turbine rotational speed), and the rotational speed of the output shaft 22 (corresponding to the vehicle speed) are supplied. It is like that.

  The electronic control device 60 functionally includes hybrid control means 62, shift control means 64, driving force fluctuation suppression means 66, and engine start control means 70. The hybrid control means 62 controls the operation of the engine 12 and the motor generator MG, for example, an engine running mode in which only the engine 12 is used as a driving force source, or a motor running mode in which the motor generator MG is used as a driving force source. A plurality of predetermined driving modes such as an engine + motor running mode that uses both of them, a charging running mode in which the motor generator MG is controlled to generate power (also referred to as regeneration control) during vehicle deceleration, etc., and the battery 44 is charged. The travel mode is switched according to the driving state such as the accelerator operation amount and the vehicle speed. The shift control means 64 controls an electromagnetic hydraulic control valve, a switching valve, and the like provided in the hydraulic control device 28, thereby changing the gear ratio and gear stage of the transmission 20 to an operating state such as an accelerator operation amount and a vehicle speed. Is controlled according to a predetermined shift map as a parameter.

  The engine start control means 70 engages the K0 clutch 34 when an engine start request is supplied from the hybrid control means 62, for example, when switching from the motor drive mode to the engine drive mode or the engine + motor drive mode. Thus, the engine 12 is cranked and the engine 12 is started by supplying fuel and igniting. Specifically, slip control means 72 that outputs the hydraulic pressure command value SPK0 of the K0 clutch hydraulic pressure PK0 and engages the K0 clutch 34 in a predetermined slip state, and supplies the fuel and ignites in the slip state to start the engine 12 And an igniting means 74 for activating the engine and a slip control end processing means 76 for ending the slip control by the slip control means 72 and completely engaging the K0 clutch 34 when the engine 12 is ignited and rotates by itself. Yes.

  FIG. 3 is a control block diagram of slip control by the slip control means 72, and FIG. 4 is a flowchart for specifically explaining signal processing of the slip control. In FIG. 3, the plant 84 to be controlled includes the hydraulic control valve 54, the hydraulic cylinder 36, the K0 clutch 34, etc., and the rotational speed difference ΔN before and after the K0 clutch 34, specifically, the MG rotational speed. A rotational speed difference (NMG-NE) between NMG and engine rotational speed NE is detected as a control amount. Then, the feed forward value ff and the feedback value fb are added to obtain the target K0 clutch torque tTK0 so that the rotation speed difference ΔN becomes a predetermined target rotation speed difference tΔN, and the target K0 clutch torque tTK0 is obtained. The hydraulic pressure command value SPK0 is calculated and the K0 clutch hydraulic pressure PK0 is controlled according to the hydraulic pressure command value SPK0, so that the K0 clutch 34 is slip-controlled so that the actual rotational speed difference ΔN becomes the target rotational speed difference tΔN. . The adjustment unit 80 calculates a feedback value fb by multiplying a deviation (tΔN−ΔN) between the target rotational speed difference tΔN and the actual rotational speed difference ΔN by a predetermined gain k1, and the operation unit 82 sets the target K0. The clutch torque tTK0 is multiplied by a coefficient k2 determined according to the pressure receiving area of the hydraulic cylinder 36, etc., and converted to a hydraulic pressure command value SPK0 related to the hydraulic pressure PK0 of the K0 clutch 34.

  More specifically, in accordance with the flowchart of FIG. 4, in step S1, whether or not the engine start process is in progress, that is, the end process by the slip control end process means 76 is completed after an engine start request is received from the hybrid control means 62. Judge whether it is before or not. If the engine start process is not in progress, step S11 is executed and the K0 slip control completion flag is returned to 0FF, while if the engine start process is in progress, step S2 is executed. In step S2, it is determined whether the engine speed NE exceeds a predetermined rotation determination value NEs and the K0 slip control completion flag is OFF. If both are satisfied, step S3 and the subsequent steps are executed. When there is an engine start request, the hydraulic cylinder 36 is rapidly filled with the hydraulic oil by the first fill (see FIG. 5) that outputs the hydraulic oil at a high pressure so that the K0 clutch 34 has the engagement torque (K0 clutch torque) TK0. Then, the engine speed NE is increased.

  Here, since the engine 12 has a larger overpass torque when compressing the first cylinder than a rotational resistance torque due to friction torque or the like, the engine 12 uses the predetermined rotation determination value NEs so that the overpass torque can be passed. The first fill is continued until the rotation determination value is exceeded, and when the rotation determination value NEs is exceeded, the slip control in step S5 and thereafter is executed. When the K0 clutch 34 is disposed in the oil chamber 40 of the torque converter 14 in the oil bath state, the responsiveness of the K0 clutch torque TK0 is poor, and therefore the shift to the slip control is performed after the engine speed NE is sufficiently high. Then, there is a possibility that a shock may occur due to complete engagement, and therefore, by shifting to slip control in a relatively low rotation state where the above overcoming torque can be passed, the engine speed NE can be quickly increased while avoiding complete engagement. It can be quickly raised to a slip state where a predetermined target rotational speed difference tΔN is obtained. From this point of view, the rotation determination value NEs is set to a relatively low rotation value within a range in which the engine speed NE can be quickly increased by passing the overcoming torque. The time t2 in FIG. 5 is a time when the engine speed NE exceeds the rotation determination value NEs.

  When the engine rotation speed NE exceeds the rotation determination value NEs, the K0 slip control completion flag is OFF at the beginning of the engine start process, so step S3 is subsequently executed and the K0 slip control execution flag is turned ON. In step S4, it is determined whether or not a value (ff−fb) obtained by subtracting the feedback value fb from the feedforward value ff is smaller than a predetermined ignition determination value Cs, and during (ff−fb) value <Cs. Slip control after step S5 is executed. The ignition determination value Cs is used to determine whether or not the engine 12 has ignited and has rotated by itself. When the engine 12 has rotated by itself, the engine 12 regardless of feedback control of the K0 clutch hydraulic pressure PK0. Since the rotational speed NE increases and the feedback value fb becomes negative, a constant value that can determine ignition of the engine 12 based on a change in the feedback value fb is set in advance.

  In step S5, the feed forward value ff of the K0 slip control is set based on the rotational resistance torque (torque at F / C) due to friction torque or the like when cranking the engine 12. This rotational resistance torque is obtained from the required torque TMG of the motor generator MG at that time, for example, by completely engaging the K0 clutch 34 in the fuel cut state (F / C) and cranking the engine 12 by the motor generator MG. . Further, by controlling the slippage of the K0 clutch 34, the engine 12 is rotated in the fuel cut state and rotated, and the K0 clutch torque TK0 (corresponding to the hydraulic pressure PK0) is reduced to cause the K0 clutch when the engine speed NE starts to decrease. It can also be obtained from the torque TK0 (hydraulic pressure PK0). On the other hand, the rotational resistance torque differs depending on the operating conditions such as the engine speed NE, the engine water temperature, the throttle valve opening, and the like, and these operating conditions are set as parameters. The feedforward value ff is set to a value smaller than the rotational resistance torque by a predetermined value α. That is, since the K0 clutch 34 is disposed in the torque converter 14 in an oil bath state, the K0 clutch torque TK0 is changed by the fluctuation of the circulating pressure due to the influence of the circulating pressure of the torque converter 14, and the K0 clutch 34 is changed. May be completely engaged, and in order to suppress this, a predetermined torque smaller than the rotational resistance torque is set as the feedforward value ff.

  In step S6, the feedback value fb of the K0 slip control is calculated based on the deviation (tΔN−ΔN) between the target rotational speed difference tΔN and the actual rotational speed difference ΔN. Specifically, the feedback value fb is obtained by multiplying the deviation (tΔN−ΔN) by the gain k1 of the feedback control. This feedback value fb is related to the K0 clutch torque TK0, like the feedforward value ff. The target rotational speed difference tΔN is set to a constant value of, for example, about 100 to several hundred rpm in consideration of the feedback control gain k1, the circulating pressure of the torque converter 14 and the like so that the K0 clutch 34 is not completely engaged. Note that the target rotational speed difference tΔN can be set using the MG rotational speed NMG or the like as a parameter so that the engine 12 can be started even at a low vehicle speed. For example, when the MG rotational speed NMG is low, a predetermined value is set. The target rotational speed difference tΔN may be reduced so that the engine rotational speed NE can be secured.

  In the next step S7, the target K0 clutch torque tTK0 is calculated by adding the feedforward value ff and the feedback value fb. In step S8, the target K0 clutch torque tTK0 is calculated based on the pressure receiving area of the hydraulic cylinder 36 and the like. The K0 hydraulic pressure command value SPK0 is calculated by multiplying a predetermined constant coefficient k2. Then, the hydraulic control valve 54 is controlled so that the K0 clutch hydraulic pressure PK0 changes according to the K0 hydraulic pressure command value SPK0. Thus, the K0 clutch 34 is slip-controlled so that the rotational speed difference ΔN becomes the target rotational speed difference tΔN, and the engine rotational speed NE becomes a rotational speed lower than the MG rotational speed NMG by the target rotational speed difference tΔN. In the meantime, the engine 12 is started by ignition processing by the ignition means 74 or the like.

  As described above, when the engine 12 is ignited by the ignition process by the ignition means 74 or the like during the slip control of the K0 clutch 34 and starts to rotate by itself, the engine speed NE increases and the rotational speed difference ΔN becomes the target rotational speed difference tΔN. The feedback value fb becomes negative and the value (ff−fb) increases. When the (ff−fb) value becomes equal to or greater than the ignition determination value Cs, the determination in step S4 is NO (negative), the slip control is terminated, and steps S9 and S10 are executed. In step S9, the K0 slip control completion flag is turned ON, whereby the hydraulic control by the slip control end processing means 76 is started. In step S10, the K0 slip control execution flag is turned OFF. At time t5 in FIG. 5, (ff−fb) value ≧ Cs is satisfied and the determination in step S4 is NO, and the K0 slip control completion flag is switched ON in step S9, whereby the hydraulic control by the slip control end processing unit 76 is performed. Is the time when was started.

  FIG. 5 is an example of a time chart when the engine 12 is started by the engine start control means 70. The time t1 is the time when the engine start request is made, and the time t2 is the time when the slip control by the slip control means 72 is started. It's time. Prior to the slip control by the slip control means 72, the K0 clutch 34 is rapidly filled with hydraulic oil by first fill, the engine 12 starts to rotate by the engagement torque TK0 of the K0 clutch 34, and the start process by the ignition means 74 starts. Is done. Therefore, the engine 12 is ignited at around time t3 at the earliest and rotates by itself, and the engine torque changes like the estimated engine torque sTE indicated by a one-dot chain line in the engine torque column, but the engine torque changes when the engine is cold. When it is difficult to ignite 12, the K0 clutch 34 is slip-controlled by the slip control means 72, so that the engine torque TE and the engine speed NE change as indicated by solid lines, and the engine 12 is ignited around time t4. There is a case. The time chart of FIG. 5 shows the case where the engine torque TE changes as shown by the solid line and ignites near time t4. At time t5, the self-rotation is detected and the end process by the slip control end processing means 76 is started. It's time. The slip control end processing means 76 has a predetermined rate of change until the rotational speeds before and after the K0 clutch 34, that is, the engine rotational speed NE and the MG rotational speed NMG substantially coincide (synchronize) to prevent shock due to sudden engagement. Then, the K0 clutch hydraulic pressure PK0 is increased, and when synchronized (time t6), the K0 clutch hydraulic pressure PK0 is increased to the maximum pressure (line pressure) at once and the K0 clutch 34 is completely engaged. In this way, the series of engine start processing is completed by raising the K0 clutch hydraulic pressure PK0 to the maximum pressure, and the determination in step S1 is NO (negative) and step S11 is executed, so that the K0 slip control completion flag is set. Is turned off.

  On the other hand, the driving force fluctuation suppressing means 66 suppresses the driving force fluctuation at the time of starting the engine by the torque control of the motor generator MG, and while the K0 clutch 34 is in the slip state (before time t6), the engine In order to absorb (cancel) the transmission torque TK0 of the K0 clutch 34 generated by the rotational resistance torque due to the friction torque of 12, the hydraulic pressure command value so that the MG torque TMG changes substantially symmetrically with respect to the K0 clutch hydraulic pressure PK0. Torque control of motor generator MG is performed based on SPK0. The ff hydraulic pressure and the fb hydraulic pressure in the column of the K0 clutch hydraulic pressure command value SPK0 in FIG. 5 are the hydraulic pressure based on the feedforward value ff and the hydraulic pressure based on the feedback value fb, and correspond to k2 × ff and k2 × fb, respectively. Further, after the K0 clutch 34 is completely engaged (after time t6), the torque of the motor generator MG according to a canceling torque pattern determined in advance based on the idle torque or the like so as to suppress the driving force fluctuation due to the engine torque TE. Control TMG. Thereby, the driving force fluctuation | variation resulting from the change of the engine torque TE at the time of starting of the engine 12 is suppressed.

  Note that the estimated engine torque sTE in FIG. 5 suppresses fluctuations in driving force at the time of engine start in the case where the engine start process is performed by controlling the engine 12 to a predetermined K0 clutch oil pressure PK0 that can crank the engine 12. Therefore, this is based on the feedforward control of the torque of the motor generator MG. Therefore, if the engine 12 does not properly ignite near the time t3, the actual engine torque TE and the estimated engine torque sTE may deviate and a large shock may occur due to torque compensation by the motor generator MG. there were.

  Thus, in the hybrid vehicle 10 of this embodiment, when the engine 12 is cranked and started by engaging the K0 clutch 34, the slip control means 72 causes the rotational speed difference ΔN before and after the K0 clutch 34 (= Slip control is performed so that NMG-NE) becomes a predetermined target rotational speed difference tΔN. When the self-rotation of the engine 12 is detected, the slip control by the slip control means 72 is terminated, and the K0 clutch hydraulic pressure PK0 is increased. Since the K0 clutch 34 is completely engaged, the slip control by the slip control means 72 is continued even when the ignition of the engine 12 is delayed during cold weather or the like. Therefore, by performing torque control (torque compensation) by the motor generator MG in accordance with the hydraulic pressure command value SPK0 of the K0 clutch 34 by the slip control means 72, friction torque, pumping loss, etc. regardless of variations in the ignition timing of the engine 12 The driving force fluctuation due to the rotational resistance torque of the engine 12 can be appropriately suppressed by torque compensation of the motor generator MG. In addition, since the K0 clutch 34 is disposed in the torque converter 14 in an oil bath state, the thermal load is reduced, and sufficient durability is obtained even in a slip state having a predetermined target rotational speed difference tΔN. It is done.

  Further, a feedback value fb obtained based on a feedforward value ff of a predetermined torque smaller than the rotational resistance torque of the engine 12 and a deviation (tΔN−ΔN) between the target rotational speed difference tΔN and the actual rotational speed difference ΔN. Is added to obtain the hydraulic pressure command value SPK0, and the hydraulic pressure control of the K0 clutch 34 is performed according to the hydraulic pressure command value SPK0. Therefore, the K0 clutch 34 enters a slip state having the target rotational speed difference tΔN based on the feedforward value ff. Control promptly. In other words, the K0 clutch 34 disposed in the torque converter 14 in an oil bath state has a poor responsiveness because it is necessary to disengage the hydraulic oil and frictionally engage it, but the feedforward value ff is set. Thus, the engine 12 can be started quickly by shifting to a predetermined slip state.

  Further, since the feedforward value ff is set to a value that is smaller than the rotational resistance torque of the engine 12 by a predetermined value α, it is possible to prevent the K0 clutch 34 from being completely engaged during the slip control and causing a shock. . In particular, since the K0 clutch 34 is disposed in the torque converter 14 in an oil bath state, the K0 clutch torque TK0 is affected by the circulation pressure of the torque converter 14 and changes in the circulation pressure. By defining a feedforward value ff that is smaller by a predetermined value α than the rotational resistance torque, complete engagement is appropriately suppressed. Although complete engagement is suppressed even in feedback control, there is a possibility of complete engagement when the influence of the circulation pressure is large, and it becomes difficult to complete engagement if the target rotational speed difference tΔN is increased. There is a possibility that the engine rotation speed NE becomes low and the engine cannot be started at a low vehicle speed.

  Further, since the value obtained by subtracting the feedback value fb from the feedforward value ff (ff−fb) becomes equal to or greater than a predetermined ignition determination value Cs, the self-rotation of the engine 12 is detected. The rotation can be accurately detected and the K0 clutch 34 can be completely engaged. By accidentally engaging the K0 clutch 34, it is possible to prevent the torque compensation by the motor generator MG from becoming incompatible and causing fluctuations in driving force. That is, when the engine 12 rotates by itself and the engine rotational speed NE increases, the rotational speed difference ΔN becomes smaller than the target rotational speed difference tΔN and the feedback value fb becomes negative, so the (ff−fb) value. The self-rotation due to the ignition of the engine 12 can be reliably detected based on this (ff−fb) value.

  As mentioned above, although the Example of this invention was described in detail based on drawing, this is an embodiment to the last, and this invention is implemented in the aspect which added various change and improvement based on the knowledge of those skilled in the art. Can do.

  10: Hybrid vehicle 12: Engine 14: Torque converter 34: K0 clutch (hydraulic friction clutch) 60: Electronic control device 66: Driving force fluctuation suppressing means 70: Engine start control means 72: Slip control means 76: Slip control end processing Means MG: Motor generator SPK0: Hydraulic pressure command value ff: Feed forward value fb: Feedback value ΔN: Rotational speed difference tΔN: Target rotational speed difference Cs: Ignition judgment value

Claims (3)

A hybrid vehicle having an engine connected to a power transmission path via a hydraulic friction clutch and a motor generator, and starting the engine by cranking the engine by engaging the hydraulic friction clutch, In the engine start control device that suppresses driving force fluctuation at the time of engine start by torque control of the motor generator,
While the hydraulic friction clutch is disposed in an oil bath state,
While detecting the rotational speed difference before and after the hydraulic friction clutch and controlling the engagement torque of the hydraulic friction clutch by hydraulic control so that the engine-side rotational speed becomes a predetermined target rotational speed difference. Slip control means for cranking the engine;
Slip control end processing means for ending hydraulic control by the slip control means when detecting the self-rotation of the engine, raising the hydraulic pressure of the hydraulic friction clutch and completely engaging the hydraulic friction clutch;
An engine start control device for a hybrid vehicle, comprising: The hydraulic friction clutch is disposed in an oil bath in the torque converter,
The slip control means calculates a deviation between a feedforward value ff corresponding to a predetermined torque smaller than the rotational resistance torque of the engine when cranking the engine, and a difference between the target rotational speed difference and the actual rotational speed difference. 2. The hybrid vehicle according to claim 1, wherein a hydraulic pressure command value SPK <b> 0 is obtained by adding the feedback value fb obtained based on the hydraulic pressure, and hydraulic control of the hydraulic friction clutch is performed according to the hydraulic pressure command value SPK <b> 0. Engine start control device. The slip control end processing means detects the self-rotation of the engine when a value (ff−fb) obtained by subtracting the feedback value fb from the feedforward value ff is equal to or greater than a predetermined ignition determination value Cs. The engine start control device for a hybrid vehicle according to claim 2.

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