JP5423565B2 - Regenerative braking control device - Google Patents

Description

  The present invention relates to a technical field in which regenerative control is performed using a rotating electrical machine.

  2. Description of the Related Art Conventionally, in hybrid vehicles and EV vehicles, a technique for generating a braking force equivalent to an engine brake is known in order to match the feeling with an internal combustion engine type vehicle. For example, in Patent Document 1, when the accelerator is turned off, a target braking force is determined based on the vehicle speed immediately before the accelerator, and a regenerative braking force corresponding to the engine brake is generated according to the determined target braking force. Technology has been proposed. Specifically, in this technique, the target braking force is reduced as the vehicle speed increases. Patent Document 2 proposes a technique for increasing the regenerative braking force as the vehicle speed increases in an EV vehicle to which a regenerative braking force equivalent to engine braking is applied.

JP-A-9-37407 JP-A-11-32404

  However, in the technique described in Patent Document 1 above, since the target braking force is determined based on the vehicle speed immediately after the accelerator is turned off, even if the vehicle speed subsequently changes, the regenerative braking force corresponding to the engine brake is not changed. It was. Therefore, the technique described in Patent Document 1 is considered to have room for further improvement in fuel consumption.

  The present invention has been made to solve the above-described problems, and provides a regenerative braking control device capable of improving the regenerative efficiency by appropriately controlling a braking force equivalent to an engine brake. This is the issue.

In one aspect of the present invention, a braking force mounted on a vehicle having a rotating electrical machine configured to be able to generate a regenerative braking force and at least using the regenerative braking force when the accelerator is turned off. In the regenerative braking control device having control means for performing control to generate the engine, the control means increases the braking force equivalent to the engine brake that is generated when the accelerator is turned off as the vehicle speed decreases. In addition to performing control to make it larger than the case, control is performed to reduce the braking force equivalent to the engine brake when the braking force equivalent to the engine brake exceeds the limit value of the regenerative braking force.

The above-described regenerative braking control device is suitably applied to a vehicle having a rotating electrical machine configured to generate a regenerative braking force during braking. The control means uses at least the regenerative braking force to perform control to generate a braking force equivalent to engine braking (engine braking equivalent braking force) when the accelerator is turned off. Specifically, the control means performs control to increase the engine brake equivalent braking force generated when the accelerator is off as the vehicle speed is lower than when the vehicle speed is higher. Thereby, compared with the case where the said control is not performed, the ratio of the regenerative braking force to the total braking force becomes large when the same braking force is realized. Therefore, according to the above-described regenerative braking control device, it is possible to reduce the energy loss due to friction braking during braking and increase the amount of deceleration energy recovered due to regeneration. Therefore, regeneration efficiency can be improved and fuel consumption can be improved.
Further, the control means performs control to reduce the engine brake equivalent braking force so that the engine brake equivalent braking force approaches the regenerative braking force in order to increase the ratio of the regenerative braking force to the engine brake equivalent braking force. Thereby, the energy loss by performing friction braking in order to implement | achieve engine braking equivalent braking force can be suppressed. Also, by performing control to reduce the braking force equivalent to engine braking, the amount of energy regenerated by the rotating electrical machine at the time of realizing the same braking is increased compared with the case where the control is not performed, so that fuel efficiency is improved. Is possible.

  The “regenerative braking force limit value” is determined according to, for example, the input / output limit of the battery to which regenerative power is charged, the input / output possible value (power or torque) of the rotating electrical machine, and the like.

  In a preferred example, when the braking force equivalent to the engine brake exceeds the limit value of the regenerative braking force, the control means controls to decrease the braking force equivalent to the engine brake by an amount that the braking force equivalent to the engine brake exceeds the limit value. It can be performed.

In another aspect of the present invention, a braking force mounted on a vehicle having a rotating electrical machine configured to be able to generate a regenerative braking force and at least using the regenerative braking force when the accelerator is turned off. In the regenerative braking control device having control means for performing control for generating the vehicle , the regenerative braking control apparatus further comprises means for calculating a target braking force to be applied to the vehicle at the time of braking of the vehicle, wherein the control means has the accelerator turned off. The braking force equivalent to the engine brake generated at the time of braking is controlled to be larger as the vehicle speed is lower than when the vehicle speed is higher, and based on the relationship between the driving characteristics for the driver's braking and the target braking force. Thus, control is performed to change the braking force corresponding to the engine brake so that the braking force applied to the vehicle approaches the target braking force.

In the above-described regenerative braking control device, the control means is based on the relationship between the driving characteristics of the driver and the target braking force, so that the braking force applied to the vehicle approaches the target braking force. Control to change. For example, in the case of driving characteristics in which the driver strongly brakes against the target braking force, the control means reduces the engine braking equivalent braking force and the driving characteristics in which the driver performs braking weakly with respect to the target braking force. In this case, the braking force equivalent to engine brake is increased. As a result, the regeneration efficiency can be improved regardless of the driving characteristics of the driver.

  Control means mounted on a vehicle having a rotating electrical machine configured to be able to generate a regenerative braking force, and performing control to generate a braking force equivalent to an engine brake when the accelerator is turned off using at least the regenerative braking force In the regenerative braking control device, the control means performs control to increase the braking force equivalent to the engine brake generated when the accelerator is turned off as the vehicle speed is lower than when the vehicle speed is higher. . Thereby, the deceleration energy recovery amount by regeneration can be increased. Therefore, regeneration efficiency can be improved and fuel consumption can be improved.

The schematic block diagram of the hybrid vehicle which concerns on this embodiment is shown. The figure for demonstrating the reason for performing 1st control in this embodiment is shown. The figure for demonstrating the 1st control in this embodiment concretely is shown. The figure for demonstrating the 2nd control in this embodiment concretely is shown. The figure for demonstrating concretely the 2nd control performed in the vehicle speed area | region where regenerative braking force does not exceed a limit value is shown. The figure for demonstrating the reason for changing a 1st vehicle speed range and a 2nd vehicle speed range is shown. The figure for demonstrating the effect at the time of changing the 1st vehicle speed range and the 2nd vehicle speed range according to the change of the limit value of regenerative braking power is shown. The figure for demonstrating the 4th control in this embodiment concretely is shown. An example of the braking force variation according to the change of a predetermined parameter is shown. It is a flowchart which shows the regenerative braking process in this embodiment. The schematic block diagram of the hybrid vehicle which concerns on a modification is shown.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

[Device configuration]
FIG. 1 is a block diagram illustrating a schematic configuration of a hybrid vehicle 1 according to the present embodiment. In FIG. 1, broken lines indicate electrical connection, and alternate long and short dash lines indicate signal input / output. In FIG. 1, for convenience of explanation, only components that are directly related to the present embodiment are illustrated, and other members are not illustrated.

  As shown in FIG. 1, the hybrid vehicle 1 mainly includes an engine (ENG) 11, motor generators MG1 and MG2, a battery (BAT) 12, a PCU (Power Control Unit) 13, and an ECU (Electronic Control Unit). ) 20, a brake position sensor (BR) 21, an accelerator position sensor (ACC) 22, and a vehicle speed sensor (S) 23.

  A hybrid vehicle (hereinafter also simply referred to as “vehicle”) 1 basically uses engine 11 only for power generation, and uses motor generator MG2 as a drive source of hybrid vehicle 1. That is, the hybrid vehicle 1 is a so-called series-type hybrid vehicle.

  The battery 12 is composed of, for example, a lithium ion battery or the like, can supply power to the motor generators MG1 and MG2, and can be charged by regenerative power of the motor generators MG1 and MG2 supplied through the PCU 13.

  Motor generator MG1 has a rotor connected to the drive shaft of engine 11. Motor generator MG1 generates electric power when the rotor rotates as the drive shaft of engine 11 rotates. On the other hand, the motor generator MG1 can crank the engine 11 by being supplied with power from the battery 12 via the PCU 13.

  Motor generator MG2 has a rotor connected to a power transmission mechanism. The motor generator MG2 outputs driving force to the driving wheels 14 via the power transmission mechanism when electric power is supplied from at least one of the battery 12 and the motor generator MG1 via the PCU 13. On the other hand, motor generator MG2 also functions as a regenerative brake. That is, the motor generator MG2 has a regenerative function for converting kinetic energy into electric energy, and generates electric power by performing regenerative operation (in other words, regenerative braking) when the hybrid vehicle 1 is braked. Motor generator MG2 is an example of the “rotary electric machine” in the present invention.

  The brake position sensor 21 detects a brake operation amount by the driver, and supplies a detection signal corresponding to the detected brake operation amount to the ECU 20. The accelerator position sensor 22 detects an accelerator operation amount (in other words, an accelerator opening degree) by the driver, and supplies a detection signal corresponding to the detected accelerator operation amount to the ECU 20. The vehicle speed sensor 23 detects the vehicle speed of the hybrid vehicle 1 and supplies a detection signal corresponding to the detected vehicle speed to the ECU 20.

  The ECU 20 includes a CPU, a ROM, a RAM, and the like, and controls each component in the hybrid vehicle 1. For example, the ECU 20 controls the motor generator MG2 so as to adjust the braking force (regenerative braking force) generated by the motor generator MG2 during braking. Further, for example, when the accelerator is turned off, the ECU 20 performs control to generate a braking force equivalent to engine braking (hereinafter simply referred to as “engine braking equivalent braking force”). Thus, the ECU 20 corresponds to an example of the “regenerative braking control device” in the present invention. Specifically, the ECU 20 corresponds to an example of a “control unit” in the present invention.

  The engine brake equivalent braking force is basically realized by using a regenerative braking force by motor generator MG2, but not only such a regenerative braking force but also a braking force by a friction brake (hereinafter referred to as "friction braking force"). It may be realized using "." For example, when the engine brake equivalent braking force is a value exceeding the limit value of the regenerative braking force, the engine brake equivalent braking force is realized using not only the regenerative braking force but also the friction braking force.

[Control method]
Next, a control method performed by the ECU 20 in the present embodiment will be described. Specifically, the first control to the fourth control performed by the ECU 20 will be described.

(First control)
First, the first control performed by the ECU 20 in the present embodiment will be described. In the present embodiment, the ECU 20 performs a first control in which the engine brake equivalent braking force generated when the accelerator is off is increased as the vehicle speed is lower than when the vehicle speed is higher. That is, the ECU 20 performs control to set an engine brake equivalent braking force having a larger value as the vehicle speed is lower and to generate the engine brake equivalent braking force when the accelerator is off.

  Here, the reason why such first control is performed will be described with reference to FIG. In FIG. 2, the horizontal axis indicates the brake operation amount, and the vertical axis indicates the braking force. In FIG. 2, a graph 201 indicates the total braking force obtained by combining the regenerative braking force and the friction braking force. A graph 202 shows the distribution of the regenerative braking force and the friction braking force according to the amount of brake operation, which is determined from the viewpoint of improving driving feeling. Further, the braking force indicated by reference numeral 200 corresponds to the limit value of the regenerative braking force (in other words, the regeneration upper limit). The limit value 200 of the regenerative braking force is an input / output limit of the battery 12 that changes in accordance with an environmental state such as a temperature of the battery 12 or a state of charge (SOC), or an input / output possible value (power or torque) of the motor generator MG2. It is calculated based on the above. Further, the limit value 200 of the regenerative braking force is calculated in consideration of restrictions on drivability.

  From the above-described graphs 201 and 202 and the limit value 200 of the regenerative braking force, for example, as shown by the hatched region in FIG. 2, the region where the regenerative braking force is used (hereinafter referred to as “regenerative braking region”) and the friction. A region where the braking force is used (hereinafter referred to as “friction braking region”) is defined. Further, the braking force indicated by the arrow 203 corresponds to the engine braking equivalent braking force, and the braking force indicated by the arrow 204 is applied according to the braking operation amount (specifically, the braking force proportional to the braking operation amount). Power). The engine brake equivalent braking force 203 is a braking force applied when the accelerator is off, and is applied regardless of the brake operation amount. In this case, the engine brake equivalent braking force 203 is basically realized by a regenerative braking force.

  Here, the ratio of the friction braking force to the total braking force during braking (during deceleration) is basically determined according to the distribution shown in the graph 202, the limit value 200 of the regenerative braking force, and the like. It is considered that the ratio of the frictional braking force to the vehicle changes depending on the magnitude of the braking force equivalent to the engine brake. For example, when the brake operation amount is relatively large and the engine brake equivalent braking force is small even if the total braking force is the same, the friction braking force occupying the total braking force is larger than when the engine brake equivalent braking force is large. The ratio is thought to increase. In this case, the ratio of regenerative energy to deceleration kinetic energy tends to decrease, that is, the amount of energy recovered by regeneration tends to decrease. In particular, when driving at low vehicle speeds such as in urban areas, the frequency of deceleration is high, and the brake operation by the driver increases. Therefore, it can be said that such a reduction in energy recovery is likely to occur due to regeneration.

  From the above, in the present embodiment, the braking force equivalent to the engine brake that is realized when the accelerator is off to reduce the energy loss due to friction braking and increase the energy recovery amount due to regeneration during deceleration braking at low vehicle speeds. The first control to be increased is performed. Specifically, ECU 20 sets an engine brake equivalent braking force having a larger value as the vehicle speed is lower, and controls motor generator MG2 so that the engine brake equivalent braking force is generated when the accelerator is off. That is, the engine brake equivalent braking force is realized by the regenerative braking force by the motor generator MG2. For example, the ECU 20 performs such first control when the vehicle speed when the accelerator is off is lower than a predetermined speed set in advance. In one example, a reference engine brake equivalent braking force is set in advance, and a correction amount for correcting the reference engine brake equivalent braking force is set in advance according to the vehicle speed. The reference engine brake equivalent braking force can be corrected by the corresponding correction amount.

  With reference to FIG. 3, the 1st control in this embodiment is demonstrated concretely. In FIGS. 3A and 3B, the horizontal axis represents the brake operation amount, and the vertical axis represents the braking force.

  FIG. 3A shows a diagram when the first control in the present embodiment is not applied, that is, a diagram when the control for increasing the braking force equivalent to the engine brake is not performed. Specifically, FIG. 3A shows a view similar to FIG. 2 for comparison with the first control. Therefore, elements having the same reference numerals as those in FIG. 2 have the same meaning, and the description thereof is omitted.

  On the other hand, FIG.3 (b) has shown the figure at the time of applying the 1st control in this embodiment. In the first control, for example, as indicated by an arrow 213, an engine brake equivalent braking force larger than the engine brake equivalent braking force 203 in FIG. When such an engine brake equivalent braking force 213 is used, the total braking force is represented by a graph 211, and the distribution between the regenerative braking force and the friction braking force is represented by a graph 212. The braking force applied according to the brake operation amount is represented by an arrow 214.

  Here, when the first control is not applied, for example, when the braking force 210 is realized, a friction braking force as indicated by reference numeral 207 in FIG. 3A is used. On the other hand, when the first control is applied, a friction braking force as indicated by reference numeral 217 in FIG. 3B is used when the same braking force 210 is realized. This friction braking force 217 is smaller than the friction braking force 207. Therefore, in the case where the same braking force is realized, it can be said that when the first control is performed, the ratio of the friction braking force to the total braking force is reduced as compared with the case where the first control is not performed. That is, it can be said that the ratio of the regenerative braking force to the total braking force increases. Therefore, according to the first control, energy loss due to friction braking can be reduced, and the amount of energy recovered by regeneration can be increased, that is, the ratio of regenerative energy to deceleration kinetic energy can be increased. Therefore, according to the first control, the regeneration efficiency can be improved, and the fuel consumption can be improved.

  Further, comparing FIG. 3 (a) and FIG. 3 (b), when the first control is applied, the same braking force is realized as compared with the case where the first control is not applied. It can be seen that the amount of brake operation required is small. Therefore, according to the first control, the amount of brake operation by the driver at the time of deceleration tends to decrease, so that the regeneration efficiency can be improved for the same reason as described above.

(Second control)
Next, the second control in the present embodiment will be described. In the present embodiment, when the regenerative braking force by the motor generator MG2 exceeds the limit value, in other words, the ECU 20 reduces the braking force equivalent to engine brake realized when the accelerator is off in a region where the regenerative power is exceeded. 2 Control is performed. Specifically, the ECU 20 decreases the engine brake equivalent braking force in a vehicle speed range in which the engine brake equivalent braking force exceeds the limit value of the regenerative braking force. In this case, the ECU 20 performs the second control for reducing the engine brake equivalent braking force in the vehicle speed range higher than the vehicle speed range to which the first control is applied. In one example, the ECU 20 decreases the engine brake equivalent braking force so that the engine brake equivalent braking force approaches the regenerative braking force in order to increase the ratio of the regenerative braking force to the engine brake equivalent braking force.

  Here, the second control in the present embodiment will be specifically described with reference to FIG. In FIGS. 4A and 4B, the horizontal axis indicates the vehicle speed, and the vertical axis indicates the braking force.

  FIG. 4A shows a diagram when the second control in this embodiment is not applied, that is, a diagram when the control for reducing the braking force corresponding to the engine brake is not performed. A graph 221 shows the relationship between the vehicle speed and the braking force corresponding to the limit value of the regenerative braking force, and a graph 222 shows the engine braking equivalent braking force. From the graphs 221 and 222, for example, as shown in FIG. 4A, a regenerative braking region and a friction braking region are defined. From this, it can be seen that in the high vehicle speed range, the limit value 221 of the regenerative braking force due to the regenerative power limit is reduced, so that the regenerative braking region tends to become smaller and the friction braking region tends to become larger. When the engine brake equivalent braking force is realized at such a high vehicle speed range, if the engine brake equivalent braking force to be realized is large, the engine brake equivalent braking force is realized by the friction braking force, for example, as shown by an arrow 223. It turns out that the ratio to do becomes large. That is, the ratio of the friction braking force to the engine braking equivalent braking force increases. Therefore, it can be said that energy loss due to friction braking tends to increase at high vehicle speeds.

  For this reason, in this embodiment, when the accelerator is off, in an area where the regenerative power is exceeded, specifically in a vehicle speed range where the braking force equivalent to the engine brake exceeds the limit value of the regenerative braking force. The second control for reducing the braking force equivalent to the engine brake is performed. That is, the ECU 20 reduces the ratio of the friction braking force to the engine brake equivalent braking force by reducing the engine brake equivalent braking force. For example, the ECU 20 performs such second control when the vehicle speed when the accelerator is off is higher than a predetermined speed set in advance. Further, the ECU 20 sets an engine brake equivalent braking force having a smaller value as the vehicle speed is higher, for example. In one example, a reference engine brake equivalent braking force is set in advance, and a correction amount for correcting the reference engine brake equivalent braking force is set in advance according to the vehicle speed. The reference engine brake equivalent braking force can be corrected by the corresponding correction amount.

  FIG. 4B shows a diagram in the case where the second control in the present embodiment is applied. In the second control, as indicated by an arrow 224, the engine braking equivalent braking force is decreased. Specifically, the engine brake equivalent braking force 222 is reduced to, for example, the engine brake equivalent braking force 225 (shown by a broken line). By performing such second control, compared to the case where the second control is not performed, for example, when the arrow 223 and the arrow 226 are compared, the ratio of the friction braking force to the engine brake equivalent braking force is reduced. I understand that. Therefore, according to the second control, it is possible to reduce energy loss due to friction braking in order to realize engine braking equivalent braking force.

  In the above description, it is described that the second control is performed in the vehicle speed range where the regenerative braking force exceeds the limit value. However, not only in the vehicle speed range but also in the vehicle speed range where the regenerative braking force does not exceed the limit value. Alternatively, the second control may be performed. In other words, even in a region where the regenerative power does not exceed, specifically, the engine brake equivalent braking force is reduced even in a vehicle speed range where the original engine braking equivalent braking force does not exceed the limit value of the regenerative braking force. The second control can be performed.

  With reference to FIG. 5, the second control performed in the vehicle speed range where the regenerative braking force does not exceed the limit value will be specifically described. FIG. 5 shows the vehicle speed on the horizontal axis and the braking force on the vertical axis.

  A graph 231 shows the relationship between the vehicle speed and the braking force corresponding to the limit value of the regenerative braking force. A graph 232 shows an engine brake equivalent braking force when the second control is not applied. When such an engine brake equivalent braking force 232 is used, at a high vehicle speed in which the vehicle speed is often maintained, if the engine brake equivalent braking force is relatively large as indicated by an arrow 237, for example, the vehicle speed is reduced. Opportunities to re-accelerate tend to increase, that is, opportunities to re-accelerate to maintain a high vehicle speed. In this case, a loss may occur in a path from regeneration (deceleration regeneration) to powering (reacceleration powering) in the vehicle 1. Specifically, in the process of energy conversion in the path “vehicle 1 → motor generator MG2 → PCU 13 → battery 12 → PCU 13 → vehicle 1”, that is, in the process of energy conversion such as “kinetic energy → electric energy → kinetic energy”. Loss can occur.

  For this reason, the second control for reducing the braking force equivalent to the engine brake in order to reduce the loss generated in the process of energy conversion as described above even in the vehicle speed range where the regenerative braking force does not exceed the limit value. Is considered desirable. For example, a graph 234 (shown by a broken line) in FIG. 5 shows an engine brake equivalent braking force obtained by reducing the engine brake equivalent braking force 232 as shown by an arrow 233 based on such a viewpoint. When the engine brake equivalent braking force is reduced in this way, for example, as shown by an arrow 238, the regenerative energy can be suppressed, and the amount of energy stored as the vehicle kinetic energy can be increased. The proportion of energy stored in 1 can be increased. As a result, it is possible to reduce a loss that occurs in the process of energy conversion when maintaining a high vehicle speed, and to improve fuel efficiency.

(Third control)
Next, the third control in the present embodiment will be described. In the present embodiment, the ECU 20 executes the third control that is performed by switching between the first control and the second control described above according to the vehicle speed range. Specifically, the ECU 20 performs the first control in a predetermined vehicle speed range (hereinafter referred to as “first vehicle speed range”), and performs the second control on a predetermined vehicle speed higher than the first vehicle speed range. (Hereinafter referred to as “second vehicle speed range”). That is, the ECU 20 performs a first control that increases the engine brake equivalent braking force in the first vehicle speed range, and performs a second control that decreases the engine brake equivalent braking force in the second vehicle speed range.

  In the present embodiment, the ECU 20 changes the first vehicle speed range and the second vehicle speed range according to the limit value of the regenerative braking force when performing the third control as described above. Specifically, when the limit value of the regenerative braking force is large, the ECU 20 sets the first vehicle speed region and the second vehicle speed region on the high vehicle speed side as compared with the case where the regenerative braking force is small. In other words, when the limit value of the regenerative braking force is small, the ECU 20 sets the first vehicle speed range and the second vehicle speed range to the low vehicle speed side as compared with the case where the limit value is large.

  Here, the reason for changing the first vehicle speed range and the second vehicle speed range as described above will be described with reference to FIG. 6 (a) and 6 (b), the horizontal axis indicates the vehicle speed, and the vertical axis indicates the braking force.

  FIG. 6A is a diagram for explaining a problem that may occur when the limit value of the regenerative braking force is reduced. A graph 241 shows the relationship between the vehicle speed and the braking force corresponding to the limit value of the regenerative braking force before the decrease. The graphs 242, 242a, and 242b indicate engine braking equivalent braking force, respectively. Specifically, the engine brake equivalent braking force 242 shows an example of the engine brake equivalent braking force to which the first control and the second control are not applied. The engine brake equivalent braking force 242a is an example of an engine brake equivalent braking force obtained by applying the first control to the engine brake equivalent braking force 242. The engine brake equivalent braking force 242b is an engine brake equivalent braking force 242b. An example of an engine brake equivalent braking force in which the second control is applied to 242 is shown.

  In accordance with such an engine brake equivalent braking force 242a, 242b, in the third control, for example, an engine brake equivalent braking force (shown by a thick line) as shown by a graph 243 is used. The engine brake equivalent braking force 243 uses the engine brake equivalent braking force 242a to which the first control is applied in the first vehicle speed range, and uses the engine brake equivalent braking force 242b to which the second control is applied in the second vehicle speed range. ing. Further, the engine brake equivalent braking force 243 is defined so that the transition between the engine brake equivalent braking force 242a and the engine brake equivalent braking force 242b is performed gently along the limit value 241 of the regenerative braking force. .

  Here, consider the case where the limit value 241 of the regenerative braking force is reduced to the limit value 241a as indicated by an arrow A1. In this case, if the engine brake equivalent braking force 243 is used without being changed, the friction braking force is used for the engine brake equivalent braking force 243 that exceeds the limit value 241a of the regenerative braking force in the hatching region 244. Therefore, as described in the second control above, it can be said that the ratio of realizing the engine braking equivalent braking force 243 by the friction braking force increases, and the energy loss due to friction braking tends to increase.

  On the other hand, FIG. 6B shows a diagram for explaining a problem that may occur when the limit value of the regenerative braking force increases. A graph 246 shows the relationship between the vehicle speed and the braking force corresponding to the limit value of the regenerative braking force before the increase. Graphs 242, 242a, and 242b respectively show engine braking equivalent braking forces similar to those shown in FIG. From such a limit value 246 of the regenerative braking force and the engine brake equivalent braking force 242a, 242b, in the third control, for example, an engine brake equivalent braking force (shown by a thick line) as shown in the graph 247 is used. The engine brake equivalent braking force 247 uses the engine brake equivalent braking force 242a to which the first control is applied in the first vehicle speed range, and uses the engine brake equivalent braking force 242b to which the second control is applied in the second vehicle speed range. Yes. Further, the engine brake equivalent braking force 247 is defined so that the transition between the engine brake equivalent braking force 242a and the engine brake equivalent braking force 242b is performed gently along the limit value 246 of the regenerative braking force. .

  Here, consider the case where the limit value 246 of the regenerative braking force increases to the limit value 246a as indicated by an arrow A2. In this case, if the engine brake equivalent braking force 247 is used without being changed, the total braking force is applied in the hatching region 248 (assuming that the region is in the low vehicle speed region) as described in the first control above. It can be said that the ratio of the regenerative energy to the deceleration kinetic energy tends to decrease as the ratio of the friction braking force to the motor increases. In other words, it can be said that the amount of energy recovered by regeneration tends to decrease.

  From the above, in the present embodiment, the first vehicle speed range to which the first control is applied and the second vehicle speed range to which the second control is applied are changed according to the change in the limit value of the regenerative braking force. Specifically, when the limit value of the regenerative braking force decreases, the ECU 20 changes the first vehicle speed region and the second vehicle speed region to the low vehicle speed side and increases the limit value of the regenerative braking force. Changes the first vehicle speed range and the second vehicle speed range to the higher vehicle speed side, respectively. In this case, the ECU 20 causes the transition between the engine brake equivalent braking force to which the first control is applied and the engine brake equivalent braking force to which the second control is applied to moderately along the limit value of the regenerative braking force after the change. The braking force equivalent to engine brake is defined as follows.

  With reference to FIG. 7, the effect when the first vehicle speed range and the second vehicle speed range are changed in accordance with the change in the limit value of the regenerative braking force will be described. In FIG. 7A and FIG. 7B, the horizontal axis indicates the vehicle speed, and the vertical axis indicates the braking force. In FIG. 7, elements having the same reference numerals as those in FIG. 6 have the same meaning, and the description thereof is omitted.

  As indicated by an arrow A1 in FIG. 7A, when the limit value 241 of the regenerative braking force decreases to the limit value 241a, the above-described engine brake equivalent braking force 243 (indicated by a broken line) is, for example, the engine brake. The braking force is changed to the equivalent braking force 251 (indicated by a thick line). That is, the engine brake equivalent braking force 243 is changed to the engine brake equivalent braking force 251 on the low vehicle speed side. The engine brake equivalent braking force 251 is a transition value between the engine brake equivalent braking force 242a to which the first control is applied and the engine brake equivalent braking force 242b to which the second control is applied. It is specified to be performed gently along the line 241a. When such an engine brake equivalent braking force 251 is used, the engine brake equivalent braking force for the hatched region 254 is reduced. Thereby, if the hatching area 254 is a high vehicle speed area, the effect of the second control described above can be expanded. That is, it is possible to reduce energy loss due to friction braking in order to realize engine braking equivalent braking force.

  On the other hand, when the limit value 246 of the regenerative braking force increases to the limit value 246a as indicated by an arrow A2 in FIG. 7B, the above-described engine brake equivalent braking force 247 (shown by a broken line) is For example, the engine braking equivalent braking force 252 (indicated by a thick line) is changed. That is, the engine brake equivalent braking force 247 is changed to the engine brake equivalent braking force 252 on the high vehicle speed side. The engine brake equivalent braking force 252 is a transition value between the engine brake equivalent braking force 242a to which the first control is applied and the engine brake equivalent braking force 242b to which the second control is applied. It is specified to be performed gently along 246a. When such an engine brake equivalent braking force 252 is used, the engine brake equivalent braking force for the hatched region 258 is increased. Thereby, if the hatching region 258 is a low vehicle speed region, the effect of the first control described above can be expanded. That is, energy loss due to friction braking can be reduced, and the amount of energy recovered by regeneration can be increased.

  As described above, according to the third control, the adjustment range of the vehicle speed range to which the first control and the second control are applied can be appropriately expanded, and the fuel efficiency can be improved.

(4th control)
Next, the fourth control in the present embodiment will be described. In the present embodiment, the ECU 20 performs the fourth control for changing the engine braking equivalent braking force according to the driving characteristics of the driver with respect to braking. Specifically, the ECU 20 calculates a target braking force to be applied to the vehicle 1 during braking of the vehicle 1 and actually applies it to the vehicle 1 based on the relationship between the driving characteristics of the driver and the target braking force. Control is performed to change the engine braking equivalent braking force so that the applied braking force approaches the target braking force. Specifically, the ECU 20 reduces the engine braking equivalent braking force when the driving characteristic is such that the driver strongly brakes the target braking force as compared with the case where the driving characteristic substantially matches the target braking force. . In other words, the ECU 20 increases the engine brake equivalent braking force in the case of driving characteristics in which the driver performs braking weakly with respect to the target braking force, compared to the case where the driving characteristics substantially match the target braking force. .

  The ECU 20 calculates, for example, a change in vehicle speed with time and a deceleration that is a time differential value, and regenerates the change in the kinetic energy of the vehicle 1 at the start of deceleration and at the end of deceleration to the maximum, A target braking force having a braking force shape that provides smooth braking without sudden change in deceleration is calculated. In one example, the ECU 20 calculates a target braking force having a braking force shape such that the braking force on the low vehicle speed side is stronger than the high vehicle speed side.

  Further, the ECU 20 records information obtained by recording temporal changes such as vehicle speed, accelerator operation amount, brake operation amount, regenerative limit braking force, regenerative limit braking power, acceleration, and the like caused by the driver's braking operation, Used as driving characteristics for driver's braking.

  Here, with reference to FIG. 8, the 4th control in this embodiment is demonstrated concretely. In FIGS. 8A and 8B, the horizontal axis indicates the vehicle speed, and the vertical axis indicates the braking force.

  FIG. 8A shows a diagram when the fourth control in the present embodiment is not applied, that is, a diagram when the control for changing the engine brake equivalent braking force is not performed according to the driving characteristics. A graph 261 shows the relationship between the vehicle speed and the braking force corresponding to the limit value of the regenerative braking force, and a graph 262 shows the engine braking equivalent braking force. A graph 263 shows an example of the target braking force, and a graph 264 shows an example of driving characteristics with respect to the driver's braking.

  As shown in the hatched region 265, it can be seen that the driving characteristic 264 is a characteristic in which the driver performs braking more weakly than the target braking force 263 in a relatively low vehicle speed side region. In this area, for example, the regenerative braking force indicated by the arrow 266a is used. In this case, compared with the case where the target braking force 263 is used, for example, the regenerative missing of the amount indicated by the arrow 266b occurs. To do. Therefore, it can be said that the regenerative efficiency is reduced as compared with the case where the target braking force 263 is used.

  Further, as shown in the hatching region 267, it can be seen that the driving characteristic 264 is a characteristic in which the driver performs braking more strongly than the target braking force 263 in the region on the relatively high vehicle speed side. In this region, for example, the friction braking force indicated by the arrow 268a is used. In this case, compared to the case where the target braking force 263 is used, for example, the friction braking region corresponding to the amount indicated by the arrow 268b is used. Becomes wider. Therefore, it can be said that the regenerative efficiency is reduced as compared with the case where the target braking force 263 is used.

  For this reason, in the present embodiment, the braking force applied to the vehicle 1 is suppressed in order to suppress a decrease in regeneration efficiency that may occur when the driving characteristics for the driver's braking and the target braking force are far from each other. The fourth control is performed to change the engine braking equivalent braking force so as to approach the target braking force. Specifically, in the case of driving characteristics in which the driver strongly brakes the target braking force, the ECU 20 reduces the braking force corresponding to the engine brake, and the driver performs braking weakly with respect to the target braking force. In the case of driving characteristics, the braking force equivalent to engine braking is increased. For example, the ECU 20 changes the engine braking equivalent braking force to a greater extent as the difference between the braking force and the target braking force in the driving characteristics for the driver's braking increases. In one example, a reference engine brake equivalent braking force is set in advance, and a correction amount for correcting the reference engine brake equivalent braking force is set according to a difference between the braking force and the target braking force in the driving characteristics. The ECU 20 can correct the reference braking force corresponding to the engine brake by a correction amount corresponding to the difference between the braking force and the target braking force in the driving characteristics.

  FIG. 8B shows a diagram in the case where the fourth control in the present embodiment is applied. In FIG. 8B, elements having the same reference numerals as those in FIG. 8A have the same meaning, and the description thereof is omitted.

  In the fourth control, when the target braking force 263 and the driving characteristic 264 as described above are obtained, the engine brake equivalent braking force 262 is increased to the engine brake equivalent braking force 262a as indicated by hatching 271, for example. For example, as indicated by hatching 272, the engine brake equivalent braking force 262 is reduced to the engine brake equivalent braking force 262b. When the braking force equivalent to the engine brake is adjusted in this way, for example, a braking characteristic (indicated by a thick line) as indicated by reference numeral 273 is obtained.

  Specifically, the braking characteristic 273 obtained by adjusting the braking force equivalent to the engine brake is the target braking force in a region where the driver has a weak driving characteristic as shown in the hatching region 274. You can see that it is approaching H.263. In such a braking characteristic 273, for example, a regenerative braking force as indicated by an arrow 275 is used, so that the regenerative braking amount increases as compared with the case where the fourth control is not applied. Therefore, according to the fourth control, it is possible to reduce the missed regeneration and improve the regeneration efficiency.

  Further, it can be seen that the braking characteristic 273 is close to the target braking force 263 in the region where the driving characteristic in which the driver strongly brakes is obtained, as indicated by the hatched region 276. In such a braking characteristic 273, for example, a friction braking force as indicated by an arrow 277 is used, so that the amount of friction braking is reduced as compared with the case where the fourth control is not applied. Therefore, according to the fourth control, energy loss due to friction braking can be reduced, and the regeneration efficiency can be improved.

[Increase / decrease in braking force equivalent to engine brake]
In the first to fourth controls described above, the control for increasing or decreasing the engine brake equivalent braking force is described. By the way, it is considered that such increase / decrease in braking force equivalent to engine brake acts as a disturbance to the driver's vehicle speed control, and may cause deterioration in drivability such as vehicle speed controllability. Therefore, it can be said that it is desirable to increase / decrease the engine braking equivalent braking force within a range in which the drivability does not deteriorate.

  Here, as shown in FIG. 9, it is conventionally known that the braking force by engine braking (hereinafter also referred to as “engine braking braking force”) changes in accordance with the change of a predetermined parameter. For example, such a change range of the braking force (in other words, a change range of the deceleration) can be adopted as an increase / decrease range of the engine brake equivalent braking force in the first to fourth controls. As a result, it is possible to appropriately keep the deterioration range of the vehicle speed controllability due to the increase or decrease of the braking force equivalent to the engine brake within the allowable range of the driver.

  Specifically, the following indices (1) to (4) can be adopted as the increase / decrease width of the braking force equivalent to the engine brake.

  (1) As the increase / decrease width of the engine brake equivalent braking force, the change width of the deceleration due to the water temperature, the oil temperature, and the gear position when the engine brake is used in the engine equipped vehicle is adopted.

  When the water temperature or the oil temperature is high, the engine friction decreases, so the engine brake braking force decreases. When the water temperature or the oil temperature is low, the engine friction increases, and the engine brake braking force tends to increase. Further, the engine brake braking force in the low gear tends to be larger than the engine brake braking force in the high gear. Such a change in the engine braking force is basically within the allowable range of the driver. Therefore, the change width of the engine brake braking force can be suitably applied to the increase / decrease width of the engine brake equivalent braking force.

  (2) As the increase / decrease width of the engine brake equivalent braking force, a deceleration change width corresponding to the vehicle weight change at the same braking force is adopted.

  For example, the deceleration tends to change (specifically, inversely proportional) in accordance with changes in vehicle weight due to passengers or cargo. Such a change in deceleration is basically within the allowable range of the driver. Accordingly, the deceleration change width can be suitably applied to the increase / decrease width of the engine brake equivalent braking force.

  (3) As the increase / decrease width of the engine brake equivalent braking force, a deceleration change width corresponding to the gradient change amount at the same braking force is adopted.

  The deceleration due to the engine braking force tends to change according to the gradient of the travel path. Such a change in deceleration is basically within the allowable range of the driver. Accordingly, the deceleration change width can be suitably applied to the increase / decrease width of the engine brake equivalent braking force.

  (4) The increase / decrease width (adjustment range) selected by the driver is adopted as the increase / decrease width of the braking force equivalent to the engine brake. That is, the driver can select the adjustment range in advance and use the adjustment range as the increase / decrease width of the engine brake equivalent braking force.

  In the first control to the third control described above, in consideration of the indicators (1) to (4), an amount by which the engine brake equivalent braking force is increased or decreased for each vehicle speed range is set in advance. It is desirable to always carry out during traveling according to the setting.

  The adjustment for the increase / decrease width of the engine brake equivalent braking force as described above is preferably performed by the regenerative device (motor generator) independently of the vehicle operating speed, the driving force, and the braking force request, regardless of the engine operating point. The present invention is applied to a vehicle having a configuration capable of determining an operating point. For example, the present invention is suitably applied to series-type hybrid vehicles and EV vehicles.

[Regenerative braking process]
Next, a regenerative braking process performed by the ECU 20 in the present embodiment will be described with reference to FIG. FIG. 10 is a flowchart showing the regenerative braking process in the present embodiment. In the regenerative braking process, the above-described fourth control is mainly executed. Further, this process is repeatedly executed by the ECU 20 at a predetermined cycle.

  First, in step S101, the ECU 20 displays various information such as information indicated by signals output from the brake position sensor 21, the accelerator position sensor 22, the vehicle speed sensor 23, and the like, and information indicating the shift position in the shift operation device, for example. get. Then, the process proceeds to step S102.

  In step S102, the ECU 20 determines whether there is a deceleration request based on the information acquired in step S101. If there is no deceleration request (step S102; No), the process ends.

  When there is a deceleration request (step S102; Yes), the ECU 20 changes with time such as vehicle speed, accelerator operation amount, brake operation amount, regenerative limit braking force, regenerative limit braking power, acceleration, and the like due to the driver's braking operation. Is recorded (step S103). In other words, the ECU 20 records, for example, vehicle speed, accelerator operation amount, brake operation amount, regenerative limit braking force, regenerative limit braking power, acceleration, and the like together with time information. The information recorded in this way is used as the driving characteristics for the driver's braking described above. Then, the process proceeds to step S104.

  In step S104, the ECU 20 performs control to adjust the engine brake equivalent braking force. Specifically, the ECU 20 adjusts the engine brake equivalent braking force based on the adjustment value of the engine brake equivalent braking force calculated in step S107 described later. That is, the ECU 20 adjusts the engine brake equivalent braking force so that the braking force applied to the vehicle 1 approaches the target braking force regardless of the driving characteristics of the driver. Then, the process proceeds to step S105.

  In the case where there is no adjustment value for adjusting the engine brake equivalent braking force (that is, the initial stage where the adjustment value has not yet been calculated), in one example, one of the above-described first control to third control The braking force equivalent to engine brake can be adjusted based on at least one of them. In another example, the adjustment value for adjusting the engine brake equivalent braking force may be set to zero, that is, the engine brake equivalent braking force may not be adjusted.

  In step S105, the ECU 20 determines whether the deceleration request has been completed based on the information acquired in the process of step S103. When the deceleration request has not ended (step S105; No), the process returns to step S103, and the ECU 20 executes the processes after step S103 again.

  On the other hand, when the deceleration request has been completed (step S105; Yes), the ECU 20 calculates a target braking force (step S106). Specifically, the ECU 20 calculates the time change of the vehicle speed and the deceleration that is the time differential value, and regenerates the change in the kinetic energy of the vehicle 1 at the start of deceleration and at the end of deceleration to the maximum. Then, a target braking force having a braking force shape that provides smooth braking without sudden change in deceleration is calculated. For example, the ECU 20 calculates a target braking force having a braking force shape such that the braking force on the low vehicle speed side becomes stronger than the high vehicle speed side. Then, the process proceeds to step S107.

  In step S107, the ECU 20 calculates an adjustment value of the engine brake equivalent braking force based on the relationship between the driving characteristics of the driver recorded in step S103 and the target braking force calculated in step S106. In this case, the ECU 20 calculates the adjustment value of the engine brake equivalent braking force so that the braking force applied to the vehicle 1 approaches the target braking force. Specifically, in the case of driving characteristics in which the driver strongly brakes the target braking force, the ECU 20 calculates an adjustment value that decreases the engine braking equivalent braking force, and with respect to the target braking force. In the case of driving characteristics where the driver weakly brakes, an adjustment value that increases the braking force equivalent to the engine brake is calculated. For example, the ECU 20 increases the adjustment value of the engine brake equivalent braking force as the difference between the braking force and the target braking force in the driving characteristics with respect to the driver's braking increases. The adjustment value calculated in this way is stored in a memory or the like (for example, the adjustment value calculated last time is overwritten) and used in the next process of step S104. Then, the process ends.

[Modification]
In the above, the example in which the present invention is applied to the series-type hybrid vehicle 1 has been described. However, the present invention can be applied to a so-called series-parallel type hybrid vehicle.

  FIG. 11 is a block diagram illustrating a schematic configuration of a series-parallel hybrid vehicle 2 according to a modification. In FIG. 11, broken lines indicate electrical connections, and alternate long and short dash lines indicate signal input / output. Note that in FIG. 11, components having the same reference numerals as those in FIG. 1 have the same functions, and the description thereof is omitted.

  As shown in FIG. 11, the hybrid vehicle 2 mainly includes an engine 11, motor generators MG1 and MG2, a battery 12, a PCU 13, a planetary gear mechanism 15, an ECU 20, a brake position sensor 21, and an accelerator position. A sensor 22 and a vehicle speed sensor 23 are provided.

  The planetary gear mechanism 15 includes, for example, a sun gear S, a pinion gear, a carrier CA that supports the pinion gear so that it can rotate and revolve, and a ring gear R. The sun gear S of the planetary gear mechanism 15 is connected to the rotor of the motor generator MG1, the carrier CA is connected to the engine 11 and the oil pump (O / P), and the ring gear R is connected to the power transmission mechanism. The motor generator MG2 is coupled to the rotor.

  In the hybrid vehicle 2, the power of the engine 11 is divided by the planetary gear mechanism 15 and used for power generation by the motor generator MG <b> 1 and driving of the hybrid vehicle 2. That is, the hybrid vehicle 2 uses at least a part of the power of the engine 11 for power generation, and uses the other part of the power of the engine 11 and the power of the motor generator MG2 as the driving force of the hybrid vehicle 2. It is configured as a hybrid vehicle.

  The present invention is not limited to application to a series-type hybrid vehicle or a series-parallel type hybrid vehicle. For example, a hybrid vehicle capable of switching between a series method and a parallel method, a series method and a series- The present invention can also be applied to a hybrid vehicle that can switch between the parallel system and the like.

  Further, the present invention is not limited to the application to the hybrid vehicle as described above, but can be applied to an EV vehicle (electric vehicle).

  Furthermore, the brake pedal operation amount is not limited to the brake operation amount, and a physical amount that changes with the driver's brake operation (for example, a hydraulic value in the case of a friction brake system using hydraulic pressure) is braked. It may be used as an operation amount. Even when such a physical quantity is used, an effect equivalent to the effect described above can be obtained.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification. Regenerative braking control with such a change is possible. The apparatus is also included in the technical scope of the present invention.

1, 2 Hybrid vehicle 11 Engine 12 Battery 13 PCU
20 ECU
MG1, MG2 motor generator

Claims (3)

Control means mounted on a vehicle having a rotating electrical machine configured to be able to generate a regenerative braking force, and performing control to generate a braking force equivalent to an engine brake when the accelerator is turned off using at least the regenerative braking force A regenerative braking control device comprising:
The control means performs control to increase the braking force corresponding to the engine brake generated when the accelerator is turned off, as the vehicle speed is lower than when the vehicle speed is higher, and to control the engine brake. A regenerative braking control device that performs control to reduce a braking force corresponding to the engine brake when power exceeds a limit value of the regenerative braking force . When the braking force equivalent to the engine brake exceeds the limit value, the control means performs control to reduce the braking force equivalent to the engine brake by an amount that the braking force equivalent to the engine brake exceeds the limit value. The regenerative braking control device according to claim 1 . Control means mounted on a vehicle having a rotating electrical machine configured to be able to generate a regenerative braking force, and performing control to generate a braking force equivalent to an engine brake when the accelerator is turned off using at least the regenerative braking force A regenerative braking control device comprising:
Means for calculating a target braking force to be applied to the vehicle during braking of the vehicle;
The control means performs control to increase the braking force equivalent to the engine brake generated when the accelerator is turned off as the vehicle speed is lower than when the vehicle speed is high, and to drive the driver against braking. based on the relationship between the characteristic and the target braking force, as the braking force applied to the vehicle approaches the target braking force, and performing control for changing the braking force of corresponding said engine brake regeneration Braking control device.

Images