Control device for hybrid vehicle

Abstract

To provide a technology that can maximize a proportion satisfied by engine torque, of required torque in accordance with the operating status of the engine.SOLUTION: A control device for a hybrid vehicle, comprises: an information collection unit that collects status information indicating an operating state of an engine; and a setting unit that sets engine torque and motor generator torque according to required torque. The setting unit refers to a threshold value for NOx emission amounts, and a correspondence relation corresponding to the status information, of correspondence relations between fuel injection amounts and NOx emission amounts, and calculates a maximum torque of when fuel is injected at a maximum injection amount that results in the NOx emission amount below the threshold value, and if the required torque is greater than the maximum torque, sets the maximum torque as engine torque, and sets torque corresponding to a difference between the required torque and the maximum torque as motor generator torque, and if the required torque is smaller than the maximum torque, sets the required torque as the engine torque.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device for a hybrid vehicle. [Background technology]

[0002] Hybrid vehicles using an engine and a motor generator as drive sources are known. In such hybrid vehicles, as disclosed in Patent Document 1, the engine and the motor generator each share the load to respond to the torque required during acceleration. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-77897 Summary of the Invention [Problem to be solved by the invention]

[0004] Even if the same injection amount of fuel is injected into the engine, the amount of NOx emissions outside the hybrid vehicle varies depending on the operating conditions of the engine. Therefore, when fuel injection is controlled assuming that the threshold for NOx emissions does not fluctuate, even if fuel is injected at a predetermined injection amount assuming that the NOx emissions will be below the threshold and close to the threshold, the NOx emissions may be below the threshold but not close to the threshold. In such cases, the injection amount can be further increased from the predetermined injection amount until the NOx emissions reach the threshold, but the amount of engine torque that satisfies the required torque cannot be maximized. Therefore, there has been a demand for technology that can maximize the amount of engine torque that satisfies the required torque depending on the operating conditions of the engine. Patent Document 1 does not take into account the fact that the amount of NOx emissions into the hybrid vehicle varies depending on the operating conditions of the engine.

[0005] The present invention has been made to solve at least part of the above-mentioned problems, and aims to provide a technology in a control device for a hybrid vehicle that can maximize the amount of engine torque that is satisfied in relation to the required torque, depending on the operating state of the engine. [Means for solving the problem]

[0006] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following aspects.

[0007] (1) According to one aspect of the present invention, there is provided a control device for a hybrid vehicle, the control device being a hybrid vehicle having an engine and a motor generator as drive sources, the control device including: an information collecting unit that collects at least an engine speed and an air-fuel ratio as state information indicating an operating state of the engine; and a setting unit that sets an engine torque output from the engine and a motor-generator torque output from the motor-generator according to a required torque required of the hybrid vehicle, the setting unit referring to a correspondence relationship between a fuel injection amount in the engine and NOx emissions to the outside of the hybrid vehicle that corresponds to the state information and a threshold value for the NOx emissions, and calculating a maximum torque that is the engine torque when the fuel is injected with a maximum injection amount among the injection amounts that results in the NOx emissions being equal to or less than the threshold value; if the required torque is greater than the maximum torque, setting the maximum torque as the engine torque and setting a torque corresponding to the difference between the required torque and the maximum torque as the motor-generator torque; and if the required torque is smaller than the maximum torque, setting the required torque as the engine torque.

[0008] The maximum injection amount among the injection amounts at which the NOx emissions are equal to or less than the threshold varies depending on the operating state of the engine, just like the NOx emissions. With this configuration, the maximum injection amount is calculated from a correspondence relationship based on the state information, and the engine torque when fuel is injected with the calculated maximum injection amount is calculated as the maximum torque. Therefore, when the required torque is greater than the maximum torque, the maximum torque is set as the engine torque, thereby maintaining the NOx emissions at or below the threshold and maximizing the amount of engine torque that satisfies the required torque depending on the operating state of the engine.

[0009] (2) In the control device of the above aspect, when the current engine torque is smaller than the required torque, the setting unit may set the engine torque so that the engine torque increases at a torque rate that is equal to or less than an upper limit value of a torque rate, which is a time increase rate of the engine torque. According to this configuration, engine torque can be increased at a torque rate equal to or less than the upper limit of the torque rate. Therefore, if the upper limit of the torque rate is set to a value that does not cause a sudden increase in engine noise, the increase in engine noise can be gradual even when engine torque increases. Furthermore, if the upper limit of the torque rate is set to a value that does not cause an increase in exhaust gas due to a sudden change in engine operating conditions, a sudden change in engine operating conditions can be suppressed even when engine torque increases, so an increase in exhaust gas can be prevented.

[0010] (3) In the control device of the above aspect, when calculating the maximum torque, the setting unit may refer to a corrected threshold value that is increased as the purification rate of a catalyst that purifies exhaust gas from the engine increases. According to this configuration, the maximum torque can be calculated by referencing the corrected threshold value that is increased and corrected according to the purification rate of the catalyst. Because the corrected threshold value is a value corrected according to the purification rate of the catalyst, even if fuel is injected with the maximum injection amount calculated by referencing the corrected threshold value, NOx emissions to the outside of the hybrid vehicle 1 can be kept below the threshold value due to purification by the catalyst. Therefore, when the required torque is greater than the maximum torque, by setting the maximum torque as the engine torque, it is possible to maximize the amount of engine torque that satisfies the required torque according to the engine operating state and the purification rate of the catalyst while maintaining NOx emissions below the threshold value.

[0011] (4) In the control device of the above embodiment, when the amount of electricity stored in a secondary battery that supplies power to the motor generator and stores the electricity generated by the motor generator is greater than a preset storage amount, the setting unit may set the engine torque to be smaller than when the storage amount is equal to or less than the set storage amount, and may set the motor generator torque to be larger than when the storage amount is equal to or less than the set storage amount. According to this configuration, when the amount of electricity stored in the secondary battery is greater than a preset amount, the amount of engine torque required to meet the required torque can be reduced and the amount of motor-generator torque required can be increased, compared to when the amount of electricity stored in the secondary battery is equal to or less than the preset amount, thereby reducing NOx emissions.

[0012] The present invention can be realized in various forms, for example, in the form of a hybrid vehicle equipped with the control device, a control method for a hybrid vehicle, and the like. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is an explanatory diagram showing a hybrid vehicle equipped with a control device of a first embodiment. [Figure 2] 5 is a flowchart showing the procedure of a torque setting process in the first embodiment. [Figure 3]FIG. 2 is an explanatory diagram illustrating an example of a map group. [Figure 4] FIG. 10 is an explanatory diagram of a method for specifying an inclusion map. [Figure 5] FIG. 4 is an explanatory diagram showing NOx emissions by a control device of a comparative example. [Figure 6] FIG. 3 is an explanatory diagram showing the amount of NOx emissions by the control device of the first embodiment. [Figure 7] 10 is a flowchart showing the procedure of a torque setting process in the second embodiment. [Figure 8] 10 is a flowchart showing the procedure of a torque setting process in the second embodiment. [Figure 9] 10 is a flowchart showing the procedure of a torque setting process in the second embodiment. [Figure 10] FIG. 10 is an explanatory diagram of advantages of the control device according to the second embodiment. [Figure 11] FIG. 10 is an explanatory diagram showing a hybrid vehicle equipped with a control device of a third embodiment. [Figure 12] 10 is a flowchart showing the procedure of a torque setting process in a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] First Embodiment 1 is an explanatory diagram illustrating the configuration of a hybrid vehicle 1 equipped with a control device 20 (details of which will be described later) according to a first embodiment. In addition to the control device 20, the hybrid vehicle 1 is equipped with an engine 11, a transmission 12, a propeller shaft 13, a differential gear 14, a drive shaft 15, tires 16, a motor generator 17, and a secondary battery 18.

[0015] In hybrid vehicle 1, engine torque (hereinafter referred to as EG torque) output from engine 11 is transmitted to propeller shaft 13 as axle torque. Furthermore, during power running, motor generator torque (hereinafter referred to as MG torque) output from motor generator 17 using power supplied from secondary battery 18 is transmitted to propeller shaft 13 as axle torque. The axle torque is transmitted to tires 16 as drive torque via differential gear 14 and drive shaft 15. In this way, hybrid vehicle 1 uses engine 11 and motor generator 17 as drive sources.

[0016] On the other hand, during regeneration, the axle torque is transmitted to the motor generator 17 as MG torque. This MG torque is used for generating electricity by the motor generator 17. The electric power generated by the motor generator 17 is charged into the secondary battery 18. In this way, the secondary battery 18 supplies electric power to the motor generator 17 during power running, and stores the electric power generated by the motor generator 17 during regeneration.

[0017] The control device 20 includes a setting unit 21, an EG drive control unit 23, an MG drive control unit 25, and an information collection unit 27. The setting unit 21 sets the EG torque and the MG torque according to the required torque required of the hybrid vehicle 1. The required torque is calculated by the setting unit 21, which detects the depression amount of an accelerator pedal (not shown) of the hybrid vehicle 1. The setting unit 21 then refers to a map or a regression equation that indicates the correspondence between the depression amount of the accelerator pedal and the required torque. The EG drive control unit 23 drives the engine 11 according to the set EG torque. The MG drive control unit 25 drives the motor generator 17 according to the set MG torque. The information collection unit 27 collects driving information related to the hybrid vehicle 1 while it is running. The information collection unit 27 periodically collects driving information while the hybrid vehicle 1 is operating and transmits a signal indicating the information to the setting unit 21. The driving information includes status information indicating the operating state of the engine 11. The information collecting unit 27 collects, as state information, at least the rotation speed and air-fuel ratio of the engine 11. The rotation speed and air-fuel ratio of the engine 11 are detected by a rotation speed sensor and an air-fuel ratio sensor, and then signals indicating the information are transmitted from the rotation speed sensor and the air-fuel ratio sensor to the information collecting unit 27, whereby the information is collected by the information collecting unit 27.

[0018] 2 is a flowchart showing the procedure of the torque setting process executed by the setting unit 21. The torque setting process is a process for setting the EG torque and the MG torque according to the required torque. The torque setting process is executed periodically while the hybrid vehicle 1 is traveling. When the torque setting process is started, the setting unit 21 first calculates the required torque Tq_trg (step S11).

[0019] Next, the setting unit 21 reads the status information (step S12). The setting unit 21 reads the latest status information from the status information transmitted from the information collecting unit 27. The status information read by the setting unit 21 may be information indicating the average values ​​of the status information transmitted from the information collecting unit 27 during a certain period from the present time onward (the average value of the rotation speed of the engine 11 and the average value of the air-fuel ratio).

[0020] Next, the setting unit 21 uses the map group GR to identify a map MP that is appropriate for the read state information (step S13). FIG. 3 shows an example of the map group GR. The map group GR includes maps MP1 to MP6 that are examples of the maps MP. As shown in map MP3, each of the maps MP1 to MP6 included in the map group GR indicates a correspondence relationship between the amount of fuel injected in the engine 11 and the amount of NOx emitted to the outside of the hybrid vehicle 1. For example, map MP3 indicates a correspondence relationship when the rotation speed of the engine 11 is 2000 rpm and the air-fuel ratio is 20. For example, when the fuel injection amount is 10 mm 3 / st, the NOx emission amount is 0.0001g / st. The map MP6 also shows the correspondence when the rotation speed of the engine 11 is 2000 rpm and the air-fuel ratio is 30. For example, when the fuel injection amount is 10 mm / s, the NOx emission amount is 0.0001g / s. 3 / st indicates that the NOx emissions are 0.0002 g / st. In this way, the correspondence relationship between the fuel injection amount in engine 11 and the NOx emissions to the outside of hybrid vehicle 1 varies depending on the operating state of engine 11, and therefore maps corresponding to each state information are included in map group GR. Note that the larger the values ​​of the engine speed and air-fuel ratio indicated in the state information, the larger the NOx emissions when fuel is injected with the same injection amount. Map group GR may be stored in setting unit 21, or may be stored in an external device or server capable of communicating with setting unit 21.

[0021] FIG. 4 is an explanatory diagram illustrating a response when the map group GR does not include a map corresponding to the state information. When the map group GR does not include a map corresponding to the state information, the map is identified using equations (1) to (3) described below. The horizontal axis of FIG. 4 represents the engine speed, and the vertical axis of FIG. 4 represents the air-fuel ratio (A / F). Each of the maps M1 to M4 is stored in the map group GR and corresponds to the state information indicated by the horizontal and vertical axes of FIG. 4. Each of the maps M1, M2 and M3, M4 corresponds to state information in which the engine 11 has the same engine speed but a different air-fuel ratio. The non-included map NI is a virtual map not included in the map group GR. Each of the line segments La and Lb connects the maps M1, M2 and M3, M4. The line segment Lc is a line segment that intersects the line segments La and Lb and passes through the non-included map NI. Distances a and b are the distances from junctions J1 and J2 of line segments Lc and La and Lb to maps M1, M3 and maps M2, M4, respectively. Distances c and d are the distances from junctions J1 and J2 to the non-inclusion map NI, respectively. When the NOx emissions at each injection amount shown in maps M1 to M4 are denoted by x1 to x4, the NOx emissions X1 and X2 at each injection amount shown in the virtual map based on the state information at junctions J1 and J2 are expressed by the following equations (1) and (2). X1=(ax2+bx1) / (a+b) (1) X2=(ax4+bx3) / (a+b) (2) The NOx emission amount xI at each injection amount shown in the non-inclusion map NI is expressed by the following equation (3). xI=(cX2+dX1) / (c+d) (3) When the map corresponding to the state information read by the processing of step S12 is the non-inclusive map NI, the NOx emission amount xI corresponding to each injection amount shown in the non-inclusive map NI is calculated by applying the NOx emission amount x1 to x4 corresponding to each injection amount shown in the maps M1 to M4 surrounding the non-inclusive map NI to the above-mentioned formulas (1) to (3). That is, the non-inclusive map NI is identified as the map MP corresponding to the read state information using the map group GR.

[0022] Returning to the description of FIG. 2, after the map MP corresponding to the read state information is identified (step S13), the setting unit 21 refers to the identified map MP and the threshold value Th of the NOx emission amount to calculate the maximum fuel injection amount MI for the engine 11 (step S14). The maximum injection amount MI is the maximum injection amount among the injection amounts at which the NOx emission amount is equal to or less than the threshold value Th. The threshold value Th is a preset value that is an upper limit value of the allowable range of NOx emission to the outside of the hybrid vehicle 1. Running of the hybrid vehicle 1 with an NOx emission amount higher than the threshold value Th is acceptable if it continues for only a short period of time, but is not preferable if it continues for a long period of time. The threshold value Th may be stored in the setting unit 21, or may be stored in an external device or server that can communicate with the setting unit 21. The setting unit 21 refers to the identified map MP to calculate, as the maximum injection amount MI, the injection amount corresponding to the maximum NOx emission among the NOx emission amounts lower than the threshold value Th. For example, when the identified map MP is map MP3 (see FIG. 3) and the threshold value Th is 0.0075 g / st, the maximum NOx emission amount among the NOx emission amounts lower than the threshold value Th is 0.0070 g / st. Therefore, the injection amount 40 mm corresponding to the maximum NOx emission amount is 0.0070 g / st. 3 / st is calculated as the maximum injection amount MI. Although the map MP3 does not describe the injection amount corresponding to 0.0075 g / st, based on each of the correspondence relationships shown in the map MP3, an injection amount of 45 mm is calculated as the injection amount corresponding to 0.0075 g / st. 3 In this case, when the threshold value Th is 0.00725 g / st, the injection amount is 42.5 mm 3 / st can also be calculated as the maximum injection amount MI.

[0023] Next, the setting unit 21 calculates the maximum torque Tq_max, which is the EG torque when fuel is injected at the maximum injection amount MI calculated in step S14 (step S15). The setting unit 21 stores a conversion formula for converting the injection amount into the EG torque.

[0024] Next, the setting unit 21 determines whether the required torque Tq_trg is greater than the maximum torque Tq_max (step S16). If the required torque Tq_trg is greater than the maximum torque Tq_max (step S16: YES), the setting unit 21 sets the maximum torque Tq_max as the EG torque, and sets the torque corresponding to the difference between the required torque Tq_trg and the maximum torque Tq_max as the MG torque (step S17). Thereafter, the setting unit 21 ends the torque setting process.

[0025] On the other hand, if the required torque Tq_trg is smaller than the maximum torque Tq_max (step S16: NO), the setting unit 21 sets the required torque Tq_trg as the EG torque (step S18). At this time, the setting unit 21 does not set the MG torque or sets the MG torque to 0. Thereafter, the setting unit 21 ends the torque setting process.

[0026] FIG. 5 is an explanatory diagram showing the amount of NOx emissions from a hybrid vehicle equipped with a control device of a comparative example. FIG. 6 is an explanatory diagram showing the amount of NOx emissions from a hybrid vehicle 1 equipped with the control device 20 of the first embodiment. The horizontal axis of FIGS. 5 and 6 represents the elapsed time during traveling, and the vertical axis of FIGS. 5 and 6 represents the amount of NOx emissions. As shown in FIG. 5, with the control device of the comparative example that does not perform control to maintain the amount of NOx emissions below the threshold Th, the amount of NOx emissions may exceed the threshold Th. On the other hand, as shown in FIG. 6, with the control device 20 of the first embodiment, the amount of NOx emissions is always maintained below the threshold Th.

[0027] As described above, the amount of NOx emissions to the outside of the hybrid vehicle 1 varies depending on the operating state of the engine 11. That is, the maximum injection amount MI of the injection amounts at which the amount of NOx emissions is equal to or less than the threshold also varies depending on the operating state of the engine 11. The control device 20 of the first embodiment described above calculates the maximum injection amount MI from the map MP based on the state information indicating the operating state of the engine 11, and also calculates the maximum torque Tq_max (EG torque when fuel is injected at the maximum injection amount MI). Therefore, if the required torque Tq_trg is greater than the maximum torque Tq_max (YES in step S16), the maximum torque Tq_max is set as the EG torque, thereby making it possible to maximize the amount of EG torque that satisfies the required torque Tq_trg in accordance with the operating state of the engine 11 while maintaining the amount of NOx emissions equal to or less than the threshold Th. Furthermore, since the maximum torque Tq_max is calculated with high accuracy according to the operating state of the engine 11, even if the required torque Tq_trg is smaller than the maximum torque Tq_max (step S16: NO), by setting the required torque Tq_trg as the EG torque, the required torque Tq_trg can be satisfied by the EG torque alone while maintaining NOx emissions below the threshold value Th.

[0028] Furthermore, according to the control device 20 of the first embodiment described above, as long as the EG torque is smaller than the maximum torque Tq_max, the NOx emissions do not exceed the threshold value Th even if the torque rate (Nm / s) is increased, and therefore it is possible to increase the EG torque at a high torque rate, thereby improving the acceleration response of the hybrid vehicle 1. The torque rate is the rate of increase of the EG torque over time.

[0029] Second Embodiment 7 to 9 are flowcharts showing the procedure of the torque setting process performed in a hybrid vehicle equipped with a control device of the second embodiment. The torque setting process performed in the second embodiment is the same as the torque setting process (FIG. 2) described in the first embodiment in steps S11 to S15, but differs in the process after step S15. The torque setting process of the second embodiment is performed periodically while the hybrid vehicle is running, similar to the torque setting process of the first embodiment.

[0030] In the torque setting process of the second embodiment, the setting unit 21 calculates the maximum torque Tq_max (step S15), and then determines whether the current EG torque TqEG is smaller than the required torque Tq_trg (step S21). The current EG torque TqEG refers to the EG torque currently being output from the engine 11. The traveling information transmitted from the information collecting unit 27 to the setting unit 21 includes information indicating the current EG torque TqEG.

[0031] If the current EG torque TqEG is greater than the required torque Tq_trg (step S21: NO), that is, if deceleration is required of the hybrid vehicle, the setting unit 21 determines whether the required torque Tq_trg is greater than the maximum torque Tq_max (step S22), similar to step S16 (see FIG. 2). If the required torque Tq_trg is greater than the maximum torque Tq_max (step S22: YES), the setting unit 21 sets the maximum torque Tq_max as the EG torque, and sets the torque corresponding to the difference between the required torque Tq_trg and the maximum torque Tq_max as the MG torque (step S23), similar to step S17 (see FIG. 2). Thereafter, the setting unit 21 ends the torque setting process.

[0032] On the other hand, if the required torque Tq_trg is smaller than the maximum torque Tq_max (step S22: NO), the setting unit 21 sets the required torque Tq_trg as the EG torque (step S24), similar to step S18 (see FIG. 2). At this time, the setting unit 21 does not set the MG torque, or sets the MG torque to 0. Thereafter, the setting unit 21 ends the torque setting process.

[0033] FIG. 8 is a flowchart showing the procedure of the process executed when the current EG torque TqEG is smaller than the required torque Tq_trg (step S21: YES). When the current EG torque TqEG is smaller than the required torque Tq_trg (step S21: YES), that is, when acceleration is required of the hybrid vehicle, the setting unit 21 calculates a torque increase ΔT (step S31). The torque increase ΔT is a value obtained by multiplying the upper limit value dT of the torque rate (Nm / s) by the execution period dTime (the time interval at which step S11 is executed) of the torque setting process of the second embodiment. The upper limit value dT is a value that is set in advance, taking into consideration not causing a sudden increase in noise caused by the engine 11 and not causing an increase in exhaust gas due to a sudden change in the operating state of the engine 11. In other words, the torque increase ΔT is the torque increase after the control period dTime when the EG torque continues to increase at the upper limit value dT.

[0034] Next, the setting unit 21 determines whether the torque corresponding to the sum of the current EG torque TqEG and the torque increase ΔT is greater than the required torque Tq_trg (step S32). If the torque corresponding to the sum of the current EG torque TqEG and the torque increase ΔT is greater than the required torque Tq_trg (step S32: YES), the setting unit 21 determines whether the required torque Tq_trg is greater than the maximum torque Tq_max (step S33), similar to step S16 (see FIG. 2) and step S22 (see FIG. 7). If the required torque Tq_trg is greater than the maximum torque Tq_max (step S33: YES), the setting unit 21 sets the maximum torque Tq_max as the EG torque, and sets the torque corresponding to the difference between the required torque Tq_trg and the maximum torque Tq_max as the MG torque (step S34), similar to step S17 (see FIG. 2) and step S23 (see FIG. 7). Thereafter, the setting unit 21 ends the torque setting process.

[0035] On the other hand, if the required torque Tq_trg is smaller than the maximum torque Tq_max (step S33: NO), the setting unit 21 sets the required torque Tq_trg as the EG torque (step S35), similar to step S18 (see FIG. 2) and step S24 (see FIG. 7). At this time, the setting unit 21 does not set the MG torque, or sets the MG torque to 0. Thereafter, the setting unit 21 ends the torque setting process.

[0036] 9 is a flowchart showing the procedure of a process executed when the torque corresponding to the sum of the current EG torque TqEG and the torque increase ΔT is smaller than the required torque Tq_trg (step S32: NO). When the torque corresponding to the sum of the current EG torque TqEG and the torque increase ΔT is smaller than the required torque Tq_trg (step S32: NO), the setting unit 21 determines whether the torque corresponding to the sum of the current EG torque TqEG and the torque increase ΔT is greater than the maximum torque Tq_max (step S36). When the torque corresponding to the sum of the current EG torque TqEG and the torque increase ΔT is greater than the maximum torque Tq_max (step S36: YES), the setting unit 21 sets the maximum torque Tq_max as the EG torque and sets the torque corresponding to the difference between the required torque Tq_trg and the maximum torque Tq_max as the MG torque (step S37), similar to steps S17 (see FIG. 2), S23 (see FIG. 7), and S34 (see FIG. 8). Thereafter, the setting unit 21 ends the torque setting process.

[0037] On the other hand, if the torque corresponding to the sum of the current EG torque TqEG and the torque increase ΔT is smaller than the maximum torque Tq_max (step S36: NO), the setting unit 21 sets the torque corresponding to the sum of the current EG torque TqEG and the torque increase ΔT as the EG torque, and sets the torque corresponding to the difference between the required torque Tq_trg and the torque corresponding to this sum as the MG torque (step S38). Thereafter, the setting unit 21 ends the torque setting process.

[0038] 7 to 9, when the current EG torque TqEG is smaller than the required torque Tq_trg (step S21: YES), the setting unit 21 sets the EG torque so that the EG torque increases at a torque rate equal to or lower than the upper limit value dT of the torque rate. That is, when acceleration is required of the hybrid vehicle, the EG torque is set so that the EG torque increases at a torque rate lower than the upper limit value dT of the torque rate in any of steps S34, S35, S37, and S38. More specifically, as described with reference to FIG. 8, when the maximum torque Tq_max is set as the EG torque in the processing of step S34, the maximum torque Tq_max is smaller than the required torque Tq_trg (step S33: YES), and the required torque Tq_trg is smaller than the torque corresponding to the sum of the current EG torque TqEG and the torque increase ΔT (step S32: YES). Furthermore, as explained in Fig. 8, when the required torque Tq_trg is set as the EG torque in the processing of step S35, the required torque Tq_trg is smaller than the torque corresponding to the sum of the current EG torque TqEG and the torque increase ΔT (step S32: YES). Furthermore, as explained in Fig. 9, when the maximum torque Tq_max is set as the EG torque in the processing of step S37, the maximum torque Tq_max is smaller than the torque corresponding to the sum of the current EG torque TqEG and the torque increase ΔT (step S36: YES). Furthermore, as explained in Fig. 9, in the processing of step S38, the torque corresponding to the sum of the current EG torque TqEG and the torque increase ΔT is set as the EG torque.

[0039] FIG. 10 is an explanatory diagram of advantages of the control device of the second embodiment. The horizontal axis of FIG. 10 represents elapsed time during driving, and the vertical axis of FIG. 10 represents torque. The thick line HL represents the required torque Tq_trg. The thin line TL represents the maximum torque Tq_max. The dashed line DL represents the EG torque controlled by the control device of the second embodiment. The dashed-dotted line CL represents the EG torque controlled by the control device of the comparative example. The control device of the comparative example sets the EG torque without considering the upper limit value dT of the torque rate, so the EG torque may be increased at a torque rate equal to or greater than the upper limit value dT. As shown in FIG. 10, the increase in the EG torque (dashed line DL) controlled by the control device of the second embodiment is smoother than the increase in the EG torque (dashed line CL) controlled by the control device of the comparative example. A smooth increase in EG torque improves the comfort of occupants of the hybrid vehicle.

[0040] According to the control device of the second embodiment described above, like the control device 20 of the first embodiment, it is possible to output EG torque while maintaining the NOx emission amount at or below the threshold value Th according to the operating state of the engine 11.

[0041] Furthermore, according to the control device of the second embodiment, if the current EG torque TqEG is smaller than the required torque Tq_trg (step S21: YES), the EG torque is set so that the EG torque increases at a torque rate equal to or less than the upper limit value dT of the torque rate. The upper limit value dT of the torque rate is set in consideration of preventing a sudden increase in noise caused by the engine 11 and preventing an increase in exhaust gas due to a sudden change in the operating state of the engine 11. Therefore, even if the EG torque increases, the increase in noise caused by the engine 11 can be made gradual. Furthermore, even if the EG torque increases, a sudden change in the operating state of the engine 11 can be suppressed, thereby preventing an increase in exhaust gas.

[0042] Third Embodiment 11 is an explanatory diagram illustrating the configuration of a hybrid vehicle 1a equipped with a control device 20a of the third embodiment. The control device 20a of the third embodiment differs from the control device 20 of the first embodiment in that it includes a setting unit 21a that is different from the setting unit 21 of the first embodiment. The hybrid vehicle 1a also differs from the hybrid vehicle 1 of the first embodiment in that it includes an exhaust pipe 19p and a catalyst unit 19c.

[0043] The exhaust pipe 19p connects the engine 11 and the catalyst unit 19c and is a pipe for sending exhaust gas from the engine 11 to the catalyst unit 19c. The catalyst unit 19c contains a catalyst that purifies the exhaust gas from the engine 11. The exhaust gas sent from the exhaust pipe 19p passes through the catalyst inside the catalyst unit 19c and is then discharged to the outside of the hybrid vehicle 1a.

[0044] The driving information transmitted from the information collecting unit 27 to the setting unit 21a includes the bed temperature of the catalyst housed in the catalyst unit 19c and the flow rate of exhaust gas flowing into the catalyst unit 19c. The bed temperature of the catalyst may be detected by a temperature sensor capable of directly detecting the temperature of the catalyst, or may be detected indirectly by a temperature sensor capable of detecting the temperature near the catalyst. The flow rate of exhaust gas may be detected by a flow rate sensor capable of directly detecting the flow rate of exhaust gas flowing inside the exhaust pipe 19p, or may be detected indirectly by a flow rate sensor capable of detecting the flow rate of gas taken into the engine 11.

[0045] Setting unit 21a calculates the purification rate of the catalyst using the catalyst bed temperature and the flow rate of exhaust gas flowing into catalyst unit 19c included in the travel information (corresponding to step S41 in FIG. 12 described later). In detail, setting unit 21a calculates the purification rate of the catalyst by referring to a map showing the correspondence between the catalyst bed temperature, the flow rate of exhaust gas flowing into catalyst unit 19c, and the purification rate of the catalyst. This map may be stored in setting unit 21a, or may be stored in an external device or server that can communicate with setting unit 21a. The calculated purification rate is used to correct threshold value Th for NOx emission amount (corresponding to step S42 in FIG. 12 described later).

[0046] 12 is a flowchart showing the procedure of the torque setting process performed by the setting unit 21a. The torque setting process performed by the setting unit 21a differs from the torque setting process (FIG. 2) described in the first embodiment in that, in addition to steps S11 to S18, steps S41 and S42 are performed between steps S13 and S14. The torque setting process in the third embodiment is performed periodically while the hybrid vehicle 1a is traveling, similar to the torque setting processes in the first and second embodiments.

[0047] After the map MP corresponding to the read state information is identified (step S13), the setting unit 21a calculates the purification rate a of the catalyst (step S41). In detail, the setting unit 21a calculates the purification rate a of the catalyst using the catalyst bed temperature and the flow rate of exhaust gas flowing into the catalyst unit 19c included in the traveling information transmitted from the information collecting unit 27.

[0048] Next, the setting unit 21a corrects the threshold value Th of the NOx emission amount (step S42). When the corrected threshold value Th is set to the corrected threshold value Tc, the setting unit 21a corrects the threshold value Th to the corrected threshold value Tc using the following equation (4) which expresses the relationship between the threshold value Th, the purification rate a of the catalyst, and the corrected threshold value Tc. Tc=100Th / (100-a) (4)

[0049] Next, the setting unit 21a calculates the maximum fuel injection amount MI for the engine 11 by referring to the map MP identified in step S13 and the corrected threshold Tc for the NOx emission amount (step S14). That is, the setting unit 21a calculates, as the maximum injection amount MI, the injection amount corresponding to the maximum NOx emission amount among the NOx emission amounts lower than the corrected threshold Tc by referring to the identified map MP. Then, the setting unit 21a calculates the maximum torque Tq_max when fuel is injected with the maximum injection amount MI calculated in step S14 (step S15). The processing from step S16 onwards is the same as in the first embodiment.

[0050] As described above, in the third embodiment, when calculating the maximum torque Tq_max (step S15), the setting unit 21a refers to the corrected threshold value Tc, which is obtained by increasing the threshold value Th as the purification rate a of the catalyst increases, in order to calculate the maximum injection amount MI required for calculating the maximum torque Tq_max (step S14).

[0051] In the control device 20a of the third embodiment described above, similarly to the control device 20 of the first embodiment, the EG torque can be output while maintaining the NOx emission amount at or below the threshold value Th according to the operating state of the engine 11.

[0052] Furthermore, according to the control device 20a of the third embodiment, the maximum torque Tq_max can be calculated by referring to the corrected threshold Tc, which is the threshold Th corrected according to the purification rate a of the catalyst. Because the corrected threshold Tc is a value corrected according to the purification rate a of the catalyst, even if fuel is injected with the maximum injection amount MI calculated with reference to the corrected threshold Tc (an injection amount MI greater than the maximum injection amount calculated with reference to the threshold Th), the amount of NOx emissions outside the hybrid vehicle 1 can be kept equal to or less than the threshold Th due to purification by the catalyst. Therefore, if the required torque Tq_trg is greater than the maximum torque Tq_max (step S16: YES), by setting the maximum torque Tq_max as the EG torque, the amount of NOx emissions that is satisfied by the EG torque relative to the required torque Tq_trg can be maximized according to the operating state of the engine 11 and the purification rate a of the catalyst while maintaining the amount of NOx emissions equal to or less than the threshold Th.

[0053] <Fourth embodiment> The control device of the fourth embodiment differs from the control device 20 of the first embodiment in that the EG torque setting and the MG torque setting are adjusted according to the amount of electricity stored in the secondary battery 18.

[0054] In the fourth embodiment, the setting unit 21 first sets the EG torque and the MG torque, and then, when the amount of stored power in the secondary battery 18 is greater than a preset set amount of stored power, sets an EG torque that is smaller than when the amount of stored power in the secondary battery 18 is equal to or smaller than the set amount of stored power, and sets an MG torque that is larger than when the amount of stored power in the secondary battery 18 is equal to or smaller than the set amount of stored power. The set amount of stored power is set to, for example, 60%, assuming that the amount of stored power is 100% when the secondary battery 18 is fully charged.

[0055] The setting of the EG torque and MG torque unique to the fourth embodiment will be specifically described below with reference to FIG. 2 . That is, in step S17, the setting unit 21 of the fourth embodiment temporarily sets the maximum torque Tq_max as the EG torque and temporarily sets the torque corresponding to the difference between the required torque Tq_trg and the maximum torque Tq_max as the MG torque. Then, if the amount of power stored in the secondary battery 18 is greater than the set amount of power stored, the setting unit 21 of the fourth embodiment temporarily sets the EG torque smaller than the maximum torque Tq_max that was temporarily set as the EG torque and sets the MG torque larger than the torque corresponding to the difference between the required torque Tq_trg and the maximum torque Tq_max that was temporarily set as the MG torque in step S17. On the other hand, if the amount of power stored in the secondary battery 18 is equal to or less than the set amount of power stored, the setting unit 21 of the fourth embodiment maintains the EG torque and MG torque that were temporarily set in step S17.

[0056] As with the control device 20 of the first embodiment, the control device of the fourth embodiment described above can output EG torque while maintaining the NOx emission amount at or below the threshold Th according to the operating state of the engine 11. Furthermore, according to the control device of the fourth embodiment, when the amount of electricity stored in the secondary battery 18 is greater than the set amount of electricity stored, the amount of electricity required to be satisfied by the EG torque can be reduced and the amount of electricity required to be satisfied by the MG torque can be increased, compared to when the amount of electricity stored in the secondary battery 18 is equal to or less than the set amount of electricity stored. As a result, the amount of NOx emission can be reduced.

[0057] <Modification of this embodiment> The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0058] In the above-described embodiment, the air-fuel ratio collected as status information is detected by an air-fuel ratio sensor, but instead of the air-fuel ratio sensor, the air-fuel ratio may be indirectly detected by a flow sensor capable of detecting the flow rate of gas taken into the engine 11 and an injection amount sensor capable of detecting the amount of fuel injected.

[0059] In the above-described embodiment, the correspondence relationship between the amount of fuel injected in the engine 11 and the amount of NOx emitted outside the hybrid vehicle 1 is shown as a map MP, but is not limited to this. The correspondence relationship between the amount of fuel injected in the engine 11 and the amount of NOx emitted outside the hybrid vehicle 1 may be shown as a regression equation. In other words, when calculating the maximum injection amount MI, the regression equation and the threshold value Th for NOx emissions may be referenced.

[0060] In the above-described embodiment, the upper limit value dT of the torque rate is a value that is set in advance, but it may be a value that varies depending on the operating state of the engine 11, such as the rotation speed and air-fuel ratio of the engine 11, and the current EG torque TqEG. In such a case, the setting unit 21 calculates the upper limit value dT of the torque rate by referring to a map or a regression equation that indicates the correspondence relationship between the operating state of the engine 11 and the upper limit value dT.

[0061] In the above-described embodiment, when calculating the purification rate of the catalyst, the setting unit 21a refers to a map showing the correspondence relationship between the catalyst bed temperature, the flow rate of exhaust gas flowing into the catalyst unit 19c, and the purification rate of the catalyst, but this is not limiting. The correspondence relationship between the catalyst bed temperature, the flow rate of exhaust gas flowing into the catalyst unit 19c, and the purification rate of the catalyst may be shown as a regression equation, and the setting unit 21a may calculate the purification rate of the catalyst by referring to this regression equation.

[0062] In the above-described embodiment, the catalyst bed temperature and the flow rate of exhaust gas flowing into catalyst section 19c are detected by a sensor capable of direct detection or a sensor capable of indirect detection, but this is not limiting. For example, the catalyst bed temperature and the flow rate of exhaust gas flowing into catalyst section 19c may be estimated from the operating state of engine 11 (speed, injection amount) and the opening of the throttle, EGR, turbo variable nozzle, etc., by estimating the flow rate of exhaust gas flowing into catalyst section 19c and the outlet exhaust temperature of engine 11, and further predicting changes in the catalyst bed temperature from changes in the flow rate and the outlet exhaust temperature.

[0063] This aspect has been described above based on embodiments and modifications. However, the above-described embodiments are intended to facilitate understanding of this aspect and are not intended to limit this aspect. This aspect may be modified or improved without departing from the spirit and scope of the claims, and equivalents thereof are included in this aspect. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

[0064] The present invention can also be realized in the following forms. [Application example 1] A control device for a hybrid vehicle using an engine and a motor generator as drive sources, an information collecting unit that collects at least the engine speed and air-fuel ratio as status information indicating the operating status of the engine; a setting unit that sets an engine torque output from the engine and a motor generator torque output from the motor generator in accordance with a required torque required for the hybrid vehicle, the setting unit refers to a correspondence relationship between an injection amount of fuel in the engine and an amount of NOx emitted to the outside of the hybrid vehicle, the correspondence relationship being in accordance with the state information, and a threshold value of the NOx emission amount, and calculates a maximum torque that is the engine torque when the fuel is injected at a maximum injection amount among the injection amounts that makes the amount of NOx emission equal to or less than the threshold value; When the required torque is greater than the maximum torque, the maximum torque is set as the engine torque, and a torque corresponding to the difference between the required torque and the maximum torque is set as the motor-generator torque; A control device for a hybrid vehicle, wherein when the required torque is smaller than the maximum torque, the required torque is set as the engine torque. [Application example 2] The control device for a hybrid vehicle according to Application Example 1, The control device for a hybrid vehicle, wherein when the current engine torque is smaller than the required torque, the setting unit sets the engine torque so that the engine torque increases at a torque rate that is equal to or less than an upper limit value of a torque rate, which is a time increase rate of the engine torque. [Application example 3] The control device for a hybrid vehicle according to Application Example 1 or Application Example 2, A control device for a hybrid vehicle, wherein the setting unit, when calculating the maximum torque, refers to a corrected threshold value that is increased as the purification rate of a catalyst that purifies exhaust gas from the engine increases. [Application example 4] The control device for a hybrid vehicle according to any one of Application Examples 1 to 3, When the amount of electricity stored in a secondary battery that supplies power to the motor generator and stores the electricity generated by the motor generator is greater than a preset storage amount, the setting unit sets the engine torque to be smaller than when the storage amount is equal to or less than the set storage amount, and sets the motor generator torque to be larger than when the storage amount is equal to or less than the set storage amount. [Explanation of symbols]

[0065] 1,1a...Hybrid vehicle 11...Engine 12...Gearbox 13...Propeller shaft 14...Differential gear 15...Drive shaft 16...Tire 17...Motor generator 18…Secondary battery 19c...Catalyst section 19p...Exhaust pipe 20, 20a...Control device 21,21a...Setting section 23...EG drive control unit 25...MG drive control unit 27...Information Gathering Department

Claims

1. A control device for a hybrid vehicle using an engine and a motor generator as drive sources, an information collecting unit that collects at least the engine speed and air-fuel ratio as status information indicating the operating status of the engine; a setting unit that sets an engine torque output from the engine and a motor generator torque output from the motor generator in accordance with a required torque required for the hybrid vehicle, the setting unit refers to a correspondence relationship between an injection amount of fuel in the engine and an amount of NOx emitted to the outside of the hybrid vehicle, the correspondence relationship being in accordance with the state information, and a threshold value of the amount of NOx emitted, and calculates a maximum torque that is the engine torque when the fuel is injected at a maximum injection amount among the injection amounts that makes the amount of NOx emitted equal to or less than the threshold value; When the required torque is greater than the maximum torque, the maximum torque is set as the engine torque, and a torque corresponding to the difference between the required torque and the maximum torque is set as the motor-generator torque; A control device for a hybrid vehicle, wherein when the required torque is smaller than the maximum torque, the required torque is set as the engine torque.

2. 2. The control device for a hybrid vehicle according to claim 1, The control device for a hybrid vehicle, wherein when the current engine torque is smaller than the required torque, the setting unit sets the engine torque so that the engine torque increases at a torque rate that is equal to or less than an upper limit value of a torque rate, which is a time increase rate of the engine torque.

3. 3. The control device for a hybrid vehicle according to claim 1 or 2, A control device for a hybrid vehicle, wherein the setting unit, when calculating the maximum torque, refers to a corrected threshold value that is increased as the purification rate of a catalyst that purifies exhaust gas from the engine increases.

4. 3. The control device for a hybrid vehicle according to claim 1 or 2, When the amount of electricity stored in a secondary battery that supplies power to the motor generator and stores the electricity generated by the motor generator is greater than a preset storage amount, the setting unit sets the engine torque to be smaller than when the storage amount is equal to or less than the set storage amount, and sets the motor generator torque to be larger than when the storage amount is equal to or less than the set storage amount.

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