Drive force control system for hybrid vehicle

Abstract

Drive force control system for a hybrid vehicle (Ve) which features: a primary drive comprising an internal combustion engine (1) and an electric motor (2); a particulate filter (7) that captures fine dust contained in exhaust gas emitted by the internal combustion engine (1); an electrical storage device (5) that supplies electrical energy to the electric motor (2), where at least one operating mode of the hybrid vehicle (Ve) is selected from a hybrid mode in which the hybrid vehicle (Ve) is driven by at least a part of a power generated by the internal combustion engine (1) and a power generated by the electric motor (2), and an electric motor mode in which the hybrid vehicle (Ve) is driven only by the power generated by the electric motor (2), and a control device (6) that controls the internal combustion engine (1) and the electric motor (2), wherein the control device (6) is configured, to switch the operating mode from electric motor mode to hybrid mode based on a state of charge of the electrical storage device (5), and a threshold level of the state of charge in order to switch the operating mode from electric motor mode to hybrid mode, to a higher level, characterized in that the control device (6) remains configured, to set an upper limit power of the combustion engine (1) in hybrid mode to a lower power in a situation where the amount of fine dust accumulated in the particulate filter (7) is equal to or less than a predetermined amount, compared with the threshold level and the upper limit power set in a situation where the amount of fine dust accumulated in the particulate filter (7) is greater than the predetermined amount.

Description

[0001] The present invention claims the advantage of JP 2022 - 081 290 A, which was filed with the Japanese Patent Office on May 18, 2022. BACKGROUND Area of ​​Revelation

[0002] Embodiments of the present invention relate to a drive force control system for a hybrid vehicle, in which a primary drive comprises an internal combustion engine and an electric motor. Discussion of the state of the art

[0003] JP 2009-24559A describes an exhaust emission control system for preventing an increase in exhaust emissions during the regeneration process of particulate matter captured by a particulate filter. To this end, the exhaust emission control system described in JP 2009-24559A is configured to reduce the flow rate of the exhaust gas entering the particulate filter during the particulate matter regeneration process. According to the teaching of JP 2009-24559A, the exhaust emission control system is specifically configured to reduce the air intake to an internal combustion engine and the flow rate of exhaust gas emitted by the internal combustion engine, or to increase the exhaust gas recirculation (EGR) rate.This means that the exhaust emission control system prevents the release of particulate matter through the particulate filter by limiting the output / power of an internal combustion engine when the cross-sectional area of ​​the particulate filter through which the exhaust gas flows is increased as a result of the particulate matter regeneration process.

[0004] The exhaust emission control system described in JP 2009 - 24 559 A limits the output / power of the combustion engine to prevent an increase in exhaust emissions during the particulate matter regeneration process. Therefore, the combustion engine may not be able to generate the driving power requested by a driver during the particulate matter regeneration process.

[0005] Furthermore, DE 10 2021 103 558 A1 discloses a hybrid system in which the operating mode is changed depending on the battery charge level (SOC), wherein the SOC threshold is changed depending on the loading of the particulate filter. SUMMARY

[0006] Aspects of embodiments of the present invention were conceived taking into account the aforementioned technical problems, and it is therefore an objective of the present invention to provide a drive force control system for a hybrid vehicle that is configured to prevent an increase in emissions / output while simultaneously achieving a required drive force in a state in which the accumulation of fine dust on a particulate filter is low.

[0007] According to the present invention, a drive force control system is provided for use in a hybrid vehicle comprising: a primary drive system comprising an internal combustion engine and an electric motor; a particulate filter that captures / collects fine dust contained in exhaust gas emitted by the internal combustion engine; and an electrical storage device that supplies electrical energy to the electric motor. An operating mode of the hybrid vehicle can be selected from at least: a hybrid mode in which the hybrid vehicle is driven by at least a portion of power / energy generated by the internal combustion engine and power / energy generated by the electric motor; and an electric motor mode in which the hybrid vehicle is driven solely by power / energy generated by the electric motor.To achieve the above-described objective, the drive force control system, according to the present invention, is provided with a control device that controls the internal combustion engine and the electric motor. The control device is configured as follows: to switch the operating mode from electric motor mode to hybrid mode based on the state of charge of the electrical storage device; and to set a threshold level of the state of charge to a higher level in order to switch the operating mode from electric motor mode to hybrid mode.According to the invention, the control device is further configured to set an upper limit power / energy of the combustion engine in hybrid mode to a lower power / energy in a situation where the amount of fine dust accumulated in the particulate filter is equal to or less than a predetermined amount, compared with the threshold level and upper limit power set in a situation where the amount of fine dust accumulated in the particulate filter is greater than the predetermined amount.

[0008] In a non-restrictive embodiment, the control device can further be configured to increase the power of the combustion engine in a range below the upper limit power with a reduction in the state of charge, in a situation where the amount of fine dust accumulated in the particulate filter is equal to or less than the predetermined amount.

[0009] In a non-restrictive embodiment, the control device can further be configured to set a target power of the combustion engine to a higher value in the situation where the amount of particulate matter accumulated in the particulate filter is equal to or less than the predetermined amount, compared to the target power set in the situation where the amount of particulate matter accumulated in the particulate filter is greater than the predetermined amount.

[0010] In a non-restrictive embodiment, the control device may further be configured to: determine the amount of fine dust accumulated in the particulate filter based on a pressure difference in electric motor mode between one side upstream and one side downstream of the particulate filter; and determine the pressure difference by allowing air-containing gas to flow through the particulate filter by rotating the internal combustion engine while holding / stopping / shutting down a fuel supply to the internal combustion engine.

[0011] Thus, in situations where the amount of particulate matter accumulated in the particulate filter is equal to or less than the predetermined amount, the combustion engine's power output is limited to the upper limit in hybrid mode, thereby reducing the exhaust gas flow rate through the particulate filter. According to the present invention, the emission of particulate matter through the particulate filter can therefore be reduced, i.e., the exhaust gas can be cleaned. Furthermore, even with limited combustion engine power, the tractive force required to propel the hybrid vehicle can be achieved by an auxiliary torque from the electric motor.

[0012] Additionally, when the amount of particulate matter accumulated in the particulate filter is equal to or less than the predetermined amount, the threshold for switching the operating mode from electric motor mode to hybrid mode is raised. According to the present invention, a shortage of electrical energy to supply the electric motor can thus be prevented despite increased power consumption during the limitation of the combustion engine torque. For this reason, a drop in driving power due to a lack of electrical energy can be prevented. Furthermore, an increase in exhaust gas emissions due to increased combustion engine power can be prevented. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Features, aspects and advantages of exemplary embodiments of the present invention will become apparent by reference to the following description and the accompanying drawings, which are not intended to limit the invention in any way. Fig. Figure 1 is a schematic representation showing an example of the construction of a hybrid vehicle to which the drive force control system according to the embodiment of the present invention is attached; Fig. Figure 2 is a flowchart showing an example of a process carried out by the drive force control system according to the embodiment of the present invention; Fig. 3 is a characteristic map that is used during the execution of normal control to determine a target power output of the internal combustion engine; and Fig. 4 is a characteristic map that is used during the execution of an internal combustion engine power limitation control to determine a target power of the internal combustion engine. DETAILED DESCRIPTION OF THE PREFERRED FORM(S)

[0014] Embodiments of the present invention will now be explained with reference to the accompanying drawings. It should be noted that the embodiments shown below are merely examples of the present invention and do not limit it.

[0015] In Fig. Figure 1 shows an exemplary assembly of a vehicle Ve to which the drive force control system according to the exemplary embodiment of the present invention is attached. In the Fig. The vehicle shown in section 1 is a hybrid vehicle, in which a primary drive is an internal combustion engine (in Fig. 1 (labeled “ENG”) 1 and a drive electric motor (in Fig. 1 designated as “MG”) 2 comprising, which serves as an electric motor of the embodiment of the present invention.

[0016] For example, a conventional gasoline or diesel internal combustion engine can be used as the internal combustion engine 1, which generates power by burning an air-fuel mixture. To transmit the power of the internal combustion engine 1 to a pair of front wheels 3, an output shaft (not shown) of the internal combustion engine 1 is connected to a power train 4.

[0017] The powertrain 4 comprises a power-sharing mechanism that distributes the torque of the internal combustion engine 1 to the front wheel pair 3 and a generator (not shown), as well as a differential that distributes the torque supplied by the internal combustion engine 1 to the front wheels 3. A single-pinion planetary gear set, for example, can be used as the power-sharing mechanism. Specifically, the power-sharing mechanism comprises: a sun gear; a ring gear arranged concentrically around the sun gear; a plurality of planet gears arranged between the sun gear and the ring gear, meshing with these gears; and a carrier that rotatably supports / mounts the planet gears.

[0018] A reaction electric motor (not shown), acting as a generator, is connected to the sun gear, the internal combustion engine 1 is connected to the carrier, and the differential gear unit is connected to the ring gear via a gear train. The drive electric motor 2 is connected in a torque transmission path to any of the rotating elements located closer to the front wheels 3 than the ring gear. Alternatively, the drive electric motor 2 can also be connected to a pair of rear wheels to transmit its torque to the rear wheels.

[0019] Like conventional electric motors used in electric and hybrid vehicles, the drive motor 2 functions as an electric motor to generate power when excited and as a generator to produce electricity when passively rotated. Examples of suitable drive motors 2 include permanent magnet synchronous electric motors and induction electric motors. Similarly, such a generating electric motor can also be used as the aforementioned reaction electric motor.

[0020] The drive electric motor 2 and the reaction electric motor are electrically connected to an electrical storage device (in Fig. The drive electric motor 2 and the reaction electric motor 5 are connected to the electrical storage device 5 (referred to as "BATT") at a relatively high voltage. Therefore, these electric motors are operated as electric motors using electrical energy supplied by the electrical storage device 5, and the electrical storage device 5 is charged with the electrical energy generated by these electric motors. The drive electric motor 2 and the reaction electric motor are also electrically connected, so that any one electric motor (e.g., the drive electric motor 2) can be operated as an electric motor by operating the other electric motor (i.e., the reaction electric motor) as a generator to supply the electrical energy generated by the reaction electric motor to the drive electric motor 2 without passing through the electrical storage device 5. The electrical storage device 5 comprises, for example, a conventional secondary battery and a capacitor.In order to detect a state of charge (hereinafter abbreviated as SOC) - degree / level of the electrical storage device 5, the electrical storage device 5 is additionally equipped with an SOC sensor 6.

[0021] In vehicle Ve, the drive torque generated by the internal combustion engine 1 is transferred to the front wheels 3 via the power distribution mechanism to propel vehicle Ve by generating a reaction torque via the reaction electric motor. To propel vehicle Ve, the drive electric motor can also be operated to generate drive torque. When the reaction electric motor operates as a generator to transfer the power of the internal combustion engine 1 to the front wheels 3, the electrical energy generated by the reaction electric motor is at least partially supplied to the drive electric motor 2 to operate it as an electric motor. Furthermore, electrical energy can also be supplied to the drive electric motor 2 from the electrical storage device 5 to operate it as an electric motor.This means that the electrical energy corresponding to the difference between the amount of electrical energy generated by the reaction electric motor and the amount of electrical energy supplied to the drive electric motor 2 is stored in the electrical storage device 5. In the exemplary embodiment of the present invention, an operating mode in which the vehicle Ve is driven by the delivery of the torque of the internal combustion engine 1 to the front wheels 3 is referred to as hybrid mode (hereinafter abbreviated as HV mode).

[0022] In the vehicle Ve, the drive electric motor 2 is mechanically connected to the front wheels 3, so that the vehicle Ve can be driven by transmitting the torque of the drive electric motor 2 to the front wheels 3 while the combustion of the internal combustion engine 1 is discontinued, i.e., without generating drive torque by the internal combustion engine 1. In the exemplary embodiment of the present invention, an operating mode in which the vehicle Ve is driven only by the delivery of torque by the drive electric motor 2 is referred to as electric motor mode (hereinafter abbreviated as EV mode).

[0023] During operation in high-voltage (HV) mode, the combustion engine 1 emits / expels exhaust gas containing particulate matter as a result of the combustion of the air / fuel mixture. To prevent the emission of particulate matter outside the vehicle Ve, a gasoline particulate filter (hereinafter abbreviated as GPF) 7 is therefore arranged on an exhaust pipe 8. The GPF 7 has a multitude of pores to allow the exhaust gas to pass through and to capture / collect the particulate matter. In addition, the GPF 7 can act as a catalyst to clean the exhaust gas by oxidizing and reducing the nitrogen oxides, carbon monoxides, or hydrocarbons contained in the exhaust gas. For this purpose, platinum, palladium, rhodium, etc., are applied to the walls of the pores of the GPF 7.

[0024] To estimate the amount of particulate matter accumulated in the GPF 7, a differential pressure sensor 9 detects the difference between the pressures upstream of (before) and downstream of (after) the GPF 7. According to the exemplary embodiment of the present invention, the control system determines that a large amount of particulate matter has accumulated in the GPF 7 when the aforementioned pressure difference is large. If the amount of particulate matter accumulated in the GPF 7 exceeds a predetermined amount, the control system oxidizes and removes the accumulated particulate matter from the GPF 7 by means of the regeneration process described in JP 2009-24559A.

[0025] The system used to control the combustion engine 1 and the drive electric motor 2 is located in Fig. The vehicle shown in Figure 1 is equipped with an electronic control unit (hereinafter referred to as ECU) 10, the main component of which is a microcomputer. The ECU 10 is configured to calculate the output torques of the internal combustion engine 1 and the drive electric motor 2 based on data transmitted by sensors as well as pre-installed maps and formulas, and to transmit the calculation results to the internal combustion engine 1 and the drive electric motor 2 in the form of a command signal.

[0026] For this purpose, signals from the differential pressure sensor 9, the SOC sensor 6, an accelerator pedal sensor that detects the position of an accelerator pedal (both not shown), and a vehicle speed sensor that detects the speed of the vehicle Ve are transmitted to the ECU 10.

[0027] In a case where the amount of particulate matter accumulated in the GPF 7 is small, the cross-sectional area of ​​the GPF 7 through which the exhaust gas flows is large. Therefore, in this case, the separation / capture efficiency of the GPF 7 is reduced. This means that if the flow rate of the exhaust gas passing through the GPF 7 is high immediately after the vehicle Ve is assembled or immediately after the particulate matter regeneration process, the particulate matter contained in the exhaust gas from the vehicle Ve can be emitted through the GPF 7. To avoid this disadvantage, the ECU 10 is configured to limit the power output of the combustion engine 1 when the amount of particulate matter accumulated in the GPF 7 is low. However, if the power output of the combustion engine 1 is limited, the required driving force may not be generated.In order to achieve the required driving force during locomotion / propulsion in HV mode, the ECU 10 is therefore configured to generate power through the internal combustion engine 1 up to a limited upper limit and to operate / actuate the drive electric motor 2 to compensate for the missing power.

[0028] For this purpose, the ECU 10, according to an exemplary embodiment of the present invention, introduces a Fig. The process shown in section 2 is as follows. Fig. In the sequence shown in Figure 2, step S1 determines whether an internal combustion engine warning light illuminates to inform a driver of a failure / malfunction of the internal combustion engine 1. Specifically, the ECU 10 has a fault diagnosis function to determine a failure / malfunction of the internal combustion engine 1 based on detection values ​​from the sensors located in the vehicle Ve, and such a determination in step S1 is made using the fault diagnosis function.

[0029] If the combustion engine warning light is off, so that the answer from step S1 is NO, the process continues with step S2 to determine whether the difference between the upstream and downstream pressures of the GPF 7, as detected by the differential pressure sensor 9 (hereinafter referred to as differential pressure P), is equal to or less than a predetermined value P0. This determination in step S2 is made to ascertain whether the particulate matter contained in the exhaust gas has accumulated in the GPF 7 to such an extent that it can be detected / collected when the combustion engine 1 is producing maximum power. For this purpose, the amount of particulate matter accumulated in the GPF 7 required to reduce the flow rate of the exhaust gas entering the GPF 7 is predetermined, and, for example, the predetermined value P0 is set to the differential pressure P at the aforementioned amount of particulate matter accumulated in the GPF 7.Instead, the predetermined value P0 can also be varied depending on the flow rate of the exhaust gas flowing to the GPF 7.

[0030] For example, the pressure difference P during operation in EV mode can be detected by the pressure difference sensor 9 in step S2 while air-containing gas flows through the exhaust pipe 8 by electrically driving the combustion engine 1 and interrupting the fuel supply to the combustion engine 1. Alternatively, in step S2, a pressure difference P can also be used based on the difference between the upstream and downstream pressures of the GPF 7 stored in the ECU 10 immediately before switching the operating mode from HV mode to EV mode.

[0031] If the combustion engine warning light is on, resulting in a YES response from step S1, or if the pressure differential P is greater than the predetermined value P0, resulting in a NO response from step S2, the process proceeds to step S3 to execute normal control. If the response to step S1 is YES, the torque for driving the vehicle Ve is controlled, taking into account the failure / malfunction of combustion engine 1. If the response to step S2 is NO, the operating mode of the vehicle Ve is selected based on the accelerator pedal position and the vehicle speed Ve, and the torques of combustion engine 1 and drive motor 2 are controlled normally, depending on the selected operating mode.

[0032] According to the exemplary embodiment of the present invention, the drive force control system is configured to change a condition for switching the operating mode from EV mode to HV mode and a target power output of the combustion engine 1 with respect to a power demanded by the driver, depending on the amount of particulate matter accumulated on the GPF 7. Here, the condition for switching the operating mode from EV mode to HV mode and the target power output of the combustion engine 1 in HV mode are explained in the situation where the amount of particulate matter accumulated on the GPF 7 is large and therefore normal control is selected.

[0033] In this case, after normal control has begun in step S3, the process proceeds to step S4 to set the condition for switching the operating mode from EV mode to HV mode. Specifically, in step S4, the fact that the state of charge (SOC) level of the electrical storage device 5 is lower than a threshold level is used as the condition for switching the operating mode from EV mode to HV mode. For example, the threshold level can be set to a permissible lower limit level of the electrical storage device 5, which is determined by the characteristics of the electrical storage device 5.

[0034] Then, in step S5, the target power of the combustion engine 1 is determined in relation to the power requested by the driver, using a reference to a... Fig. The characteristic curve shown in section 3 is determined, and then the process returns to the previous one. In the section shown in Fig. In the characteristic map shown in Figure 3, the horizontal axis represents the power demanded by the driver, the vertical axis represents the target power of the internal combustion engine 1, the solid line indicates the target power of the internal combustion engine 1 relative to the power demanded by the driver when the state of charge (SOC) of the electrical storage device 5 is high, and the dashed line indicates the target power of the internal combustion engine 1 relative to the power demanded by the driver when the state of charge (SOC) of the electrical storage device 5 is low. The in Fig. The map shown in Figure 3 is configured such that the target power of the combustion engine 1 is set to a total value consisting of the power demanded by the driver and the power required to charge the electrical storage device 5. That is, the target power of the combustion engine 1 is increased by increasing the power demanded by the driver and decreasing the state of charge (SOC) of the electrical storage device 5. In particular, the power demanded by the driver can be calculated based on the accelerator pedal position and the vehicle speed Ve.

[0035] In a case where the pressure difference P is equal to or less than the predetermined value P0, so that the answer from step S2 is YES, the particulate matter can be discharged through the GPF 7 in a high-performance area if the output power of the combustion engine 1 is relative to the value in Fig. The characteristic map shown in Figure 3 is controlled. If the answer from step S2 is YES, the process proceeds to step S6 to execute an internal combustion engine power limitation control to restrict the output power of the internal combustion engine 1 to a predetermined power. As described later, as a consequence of limiting the output power of the internal combustion engine 1, the drive torque generated by the drive electric motor 2 is increased to achieve the required drive force to propel the vehicle Ve, and thus the state of charge (SOC) of the electrical storage device 5 is reduced more rapidly.

[0036] When the combustion engine power limitation control is activated, the point in time for switching the operating mode from EV mode to HV mode is therefore brought forward. For this purpose, the process proceeds to step S7 to set the condition for switching the operating mode from EV mode to HV mode. In step S7, specifically, the threshold value of the state of charge (SOC) level of the electrical storage device 5 for switching the operating mode from EV mode to HV mode is set to a higher level than in normal control. That is, in step S7, the available time for generating auxiliary torque by the drive electric motor 2 during propulsion in HV mode is extended. For this purpose, an additional value α is added in step S7 to the threshold value used in normal control. The additional value α can be not only a fixed value but also a variable, e.g.,depending on the history of the performance demanded by the driver and depending on the situation (e.g. when driving on a mountain road).

[0037] Subsequently, in step S8, the target power of the combustion engine 1 is determined in relation to the power demanded by the driver, with reference to a value in Fig. The characteristic curve shown in section 4 is determined, and then the process returns to the previous stage. In the section shown in Fig. In the characteristic map shown in Figure 4, the horizontal axis represents the power demanded by the driver, the vertical axis represents the target power of the internal combustion engine 1, the solid line indicates the target power of the internal combustion engine 1 relative to the power demanded by the driver when the state of charge (SOC) of the electrical storage device 5 is high, and the dashed line indicates the target power of the internal combustion engine 1 relative to the power demanded by the driver when the state of charge (SOC) of the electrical storage device 5 is low. As shown in Figure 4, the horizontal axis represents the power demanded by the driver, the vertical axis represents the target power of the internal combustion engine 1 relative to the power demanded by the driver when the state of charge (SOC) of the electrical storage device 5 is low. Fig. As shown in Figure 4, the map is configured to set an upper limit P1 to the output power of the combustion engine 1. Specifically, the upper limit P1 is set to a value that allows for the collection of all the particulate matter contained in the exhaust gas of the combustion engine 1 flowing into the GPF 7. That is, in this case, the combustion engine 1 operates while its output power is limited to the upper limit P1, which is lower than the maximum output power determined by the specifications of the combustion engine 1.

[0038] In this case, the target power of the combustion engine 1 is adjusted to a total value of the power demanded by the driver and the power required to charge the electrical storage device 5 when the power demanded by the driver falls below a low-load range that is lower than the upper limit power P1 of the combustion engine 1. That is, the target power of the combustion engine 1 is increased with an increase in the power demanded by the driver and a decrease in the state of charge (SOC) of the electrical storage device 5. Furthermore, the in Fig. The map shown in Figure 4 is configured to increase the target power of the combustion engine 1 in order to charge the electrical storage device 5 in the low-load range, to a higher value than that shown in Figure 4. Fig. 3 of the characteristic map shown. For example, if normal control is executed and the power demanded by the driver is P2, the target power of the combustion engine 1 is set to P3 in order to charge the electrical storage device 5, as shown in Fig. 3 shown. However, if the combustion engine power limitation control is executed and the power requested by the driver is P2, the target power of the combustion engine 1 is set to P4 in order to charge the electrical storage device 5, which is higher than P3 by a predetermined value, as shown in Fig. 4 shown.

[0039] In this case, during driving in a high-load range where the power demanded by the driver is higher than the upper limit power P1 of the output power of the internal combustion engine 1, the internal combustion engine 1 is operated to generate the upper limit power P1, and the electrical energy corresponding to a lack of power to achieve the power demanded by the driver is supplied to the drive electric motor 2 by the electrical storage device 5.

[0040] Therefore, if the pressure difference P between one side upstream and one side downstream of the GPF 7 is small, i.e., if the accumulation of particulate matter in the GPF 7 is small, the flow rate of the exhaust gas flowing through the GPF 7 can be reduced by limiting the output power of the combustion engine 1. Consequently, the emission of particulate matter by the GPF 7 can be reduced, i.e., the exhaust gas can be cleaned. Specifically, according to the exemplary embodiment of the present invention, the output power of the combustion engine 1 is limited to the upper limit at which the particulate matter can be collected by the GPF 7. According to the exemplary embodiment of the present invention, the particulate matter can therefore be collected by the GPF 7 in a timely / immediate manner, thereby improving the particulate matter collection efficiency of the GPF 7 in a timely / immediate manner. For this reason, the limitation of the output power of the combustion engine 1 can be lifted in a timely / immediate manner.

[0041] Furthermore, even with limited power output from the combustion engine 1, the tractive force required by the driver to propel the vehicle Ve can be achieved through the auxiliary torque of the drive electric motor 2. In this case, at a higher state of charge (SOC) of the electrical storage device 5, the operating mode switches from EV mode to HV mode. Therefore, despite increased power consumption when the combustion engine torque is limited, the SOC of the electrical storage device 5 will not drop excessively. For this reason, a decrease in tractive force due to a lack of electrical energy can be prevented. Additionally, an increase in exhaust emissions due to an increase in the output power of the combustion engine 1 can be prevented.

[0042] When the vehicle Ve is driven in the low-load range during the execution of the combustion engine power limitation control, the target power of the combustion engine 1 is increased compared to the target power set during normal control operation, so that the state of charge (SOC) of the electrical storage device 5 can be maintained at a high level. This prevents the SOC of the electrical storage device 5 from immediately dropping to the lower limit level when moving in the high-load range. Therefore, a reduction in driving power due to a lack of electrical energy can be prevented. Furthermore, an increase in exhaust emissions can also be prevented by increasing the output power of the combustion engine 1.

[0043] Although the exemplary embodiments of the present invention have been described above, it will be understood by those skilled in the art that the present invention is not limited to the exemplary embodiments described and that various changes and modifications can be made within the scope of the present invention. As described, in the exemplary embodiment of the present invention, the drive force control system is used for a series-parallel hybrid vehicle in which the electrical storage device 5 is charged by the generator and the driving electric motor 2 generates an auxiliary torque.Alternatively, the drive force control system according to the exemplary embodiment of the present invention can also be used for a series hybrid vehicle in which the power of an internal combustion engine is converted into electrical energy by a generator, and an electric motor is operated to propel the hybrid vehicle using electrical energy supplied by the generator and a battery. In this case, in hybrid mode, the power of the internal combustion engine is converted into electrical energy by the generator, and in electric motor mode, the internal combustion engine is stopped, and the electrical energy is supplied to the electric motor solely from the battery. Furthermore, the drive force control system according to the exemplary embodiment of the present invention can also be used for a parallel hybrid vehicle without a generator, in which an internal combustion engine and an electric motor are connected to drive wheels.In this case, in hybrid mode, the power of the combustion engine and the electric motor is transferred to the drive wheels, while in electric-only mode, the combustion engine is switched off / stopped and power is transferred to the drive wheels solely by the electric motor. If the combustion engine's power output is limited in a parallel hybrid vehicle, the aforementioned controls can be implemented by operating the electric motor as a generator in a low-load range.

Claims

[1] Drive force control system for a hybrid vehicle (Ve) which features: a primary drive comprising an internal combustion engine (1) and an electric motor (2); a particulate filter (7) that captures fine dust contained in exhaust gas emitted by the internal combustion engine (1); an electrical storage device (5) that supplies electrical energy to the electric motor (2), where at least one operating mode of the hybrid vehicle (Ve) is selected from a hybrid mode in which the hybrid vehicle (Ve) is driven by at least a part of a power generated by the internal combustion engine (1) and a power generated by the electric motor (2), and an electric motor mode in which the hybrid vehicle (Ve) is driven only by the power generated by the electric motor (2), and a control device (6) that controls the internal combustion engine (1) and the electric motor (2), wherein the control device (6) is configured, to switch the operating mode from electric motor mode to hybrid mode based on a state of charge of the electrical storage device (5), and to set a higher threshold level for the state of charge in order to switch the operating mode from electric motor mode to hybrid mode, characterized by , that the control device (6) remains configured, to set an upper limit power of the combustion engine (1) in hybrid mode to a lower power in a situation where the amount of fine dust accumulated in the particulate filter (7) is equal to or less than a predetermined amount, compared with the threshold level and the upper limit power set in a situation where the amount of fine dust accumulated in the particulate filter (7) is greater than the predetermined amount. [2] Drive force control system for the hybrid vehicle (Ve) according to claim 1, wherein the control device (6) is further configured to increase the power of the internal combustion engine (1) within a range that is lower than the upper limit power when the state of charge decreases in the situation in which the amount of fine dust accumulated in the particulate filter (7) is equal to or less than the predetermined amount. [3] Drive force control system for the hybrid vehicle (Ve) according to claim 1 or 2, wherein the control device (6) is further configured to set a target power of the internal combustion engine (1) with respect to a power required to drive the hybrid vehicle (Ve) to a higher value in the situation in which the amount of particulate matter accumulated in the particulate filter (7) is equal to or less than the predetermined amount, compared to the target power set in the situation in which the amount of particulate matter accumulated in the particulate filter (7) is greater than the predetermined amount. [4] Drive force control system for the hybrid vehicle (Ve) according to claim 1, wherein the control device (6) is further configured as follows: to determine the amount of fine dust accumulated in the particle filter (7) based on a pressure difference (P) between a side upstream and a side downstream of the particle filter (7); and to detect the pressure difference (P) in electric motor mode by allowing air-containing gas to flow through the particulate filter (7) by rotating the combustion engine (1) while a fuel supply to the combustion engine (1) is stopped.

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