JP2012101571A - Brake system of electric vehicle, and control method of electric negative pressure pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress noise by an electric negative pressure pump in an electric vehicle.SOLUTION: The brake system 100 of an electric vehicle includes a brake booster 1, a sub pump 2S and a main pump 2M supplying negative pressure to the brake booster 1, a joining path 33 and a first branch path 31 connecting the sub pump 2S to the brake booster 1, the joining path 33 and a second branch path 32 connecting the main pump 2M to the brake booster 1, a control part 10 controlling driving of the sub and main pumps 2S and 2M and a vehicle speed sensor 9 detecting vehicle speed of the electric vehicle. The sub pump 2S has a capacity smaller than that of the main pump 2M. The control part 10 controls the main pump 2M to be non-driven and the sub pump 2S to be driven when the vehicle speed detected by the vehicle speed sensor 9 is lower than a prescribed vehicle speed.

Description

  The present invention relates to a brake system for an electric vehicle and a control method for an electric negative pressure pump.

  Conventionally, a master back (also referred to as a brake booster or a brake booster), which is a device that amplifies the depression force of a brake pedal, is known as a brake system (for example, Patent Document 1). The master back has a pressure chamber to which a negative pressure is supplied, and amplifies the depression force of the brake pedal using this negative pressure.

  The negative pressure is supplied to the master back by a negative pressure pump driven by the engine or a negative pressure pump driven electrically.

JP 2006-123798 A

  However, since an engine is not mounted in an electric vehicle, an engine-driven negative pressure pump cannot be used. Therefore, an electric negative pressure pump is used in a brake system for an electric vehicle.

  By the way, since an electric vehicle does not have an engine, it has the characteristic that the noise of a vehicle is small. In particular, it is quiet when driving at low speeds such as creeping or when stopping. As a result, the driving noise of the electric negative pressure pump becomes conspicuous during low speed running or when stopped. That is, in an electric vehicle, since the vehicle is quiet, the drive sound of the electric negative pressure pump may be annoying.

  This invention is made | formed in view of this point, The place made into the objective is to suppress the noise by an electric negative pressure pump in an electric vehicle.

  The present invention is directed to a brake system for an electric vehicle having a master back. The brake system of the electric vehicle includes first and second electric negative pressure pumps that supply negative pressure to the master back, a first supply path that connects the first electric negative pressure pump to the master back, A second supply path for connecting the second electric negative pressure pump to the master back, a control means for controlling the driving of the first and second electric negative pressure pumps, and a vehicle speed detecting means for detecting the vehicle speed of the electric vehicle. The first electric negative pressure pump has a smaller capacity than the second electric negative pressure pump, and the control means is configured such that the vehicle speed detected by the vehicle speed detection means is less than a predetermined vehicle speed. Furthermore, the first electric negative pressure pump is driven, and the rotation speed of the second electric negative pressure pump is made lower than the rotation speed when the vehicle speed is equal to or higher than the predetermined vehicle speed.

  In the case of the above configuration, when the vehicle speed is equal to or higher than the predetermined vehicle speed, at least the second electric negative pressure pump is driven at a predetermined rotation speed. On the other hand, when the vehicle speed is less than the predetermined vehicle speed, the first electric negative pressure pump is driven, and the rotation speed of the second electric negative pressure pump is reduced below the predetermined rotation speed when the vehicle speed is equal to or higher than the predetermined vehicle speed. . Here, in order to reduce the rotation speed of the second electric negative pressure pump, it is assumed that the second electric negative pressure pump is brought into a non-driving state where the rotation speed is zero.

  When the vehicle speed is less than the predetermined vehicle speed, the road noise is small and the vehicle noise is relatively low. Since the first electric negative pressure pump has a smaller capacity than the second electric negative pressure pump, the driving sound is low. That is, when the vehicle noise is low and the vehicle speed is lower than the predetermined vehicle speed, the rotational speed of the second electric negative pressure pump is reduced and the first electric negative pressure pump is driven, thereby making the pump driving sound inconspicuous. Can be made.

  In addition, since the operation range in which the rotation speed of the second electric negative pressure pump is reduced and the first electric negative pressure pump is driven is a relatively low speed range in which the vehicle speed is less than the predetermined vehicle speed, the required negative pressure of the master back is small. Therefore, even when the first electric negative pressure pump with a small capacity is driven and the rotation speed of the second electric negative pressure pump with a large capacity is reduced, the required negative pressure can be met.

  Further, in a driving region where the vehicle speed is equal to or higher than a predetermined vehicle speed, the required negative pressure increases because the vehicle speed increases and a large braking force is required. In this case, the second electric negative pressure pump is driven at a higher rotational speed than when the vehicle speed is lower than the predetermined vehicle speed, and the capacity of the second electric negative pressure pump is larger than that of the first electric negative pressure pump. Since it is large, the required negative pressure can be secured. Further, when the vehicle speed is increased, vehicle noise such as road noise increases, so even if the number of rotations of the second electric negative pressure pump having a relatively large capacity is increased, the drive sound is not a problem.

  Further, the control means may put the second electric negative pressure pump in a non-driving state where the rotational speed is zero when the vehicle speed detected by the vehicle speed detection means is less than the predetermined vehicle speed.

  According to the above configuration, when the vehicle speed is lower than the predetermined vehicle speed, the second electric negative pressure pump is not driven, so that the driving sound of the pump can be made less noticeable.

  Further, by properly using the first electric negative pressure pump and the second electric negative pressure pump with a predetermined vehicle speed as a boundary, it is possible to reduce the deviation in driving time of the two electric negative pressure pumps. Thereby, the reliability of the electric negative pressure pump can be improved.

  Here, it is preferable that the first supply path and the second supply path are parallel to each other, and the first supply path has a smaller volume than the second supply path.

  In the case of the configuration described above, since the volume of the first supply path is small, the required negative pressure can be transmitted to the master back even with the first electric negative pressure pump having a small capacity. As a result, the required negative pressure for the master back can be secured even with the first electric negative pressure pump having a small capacity. Moreover, the drive time of a 1st electric negative pressure pump can be reduced and power consumption can be suppressed.

  The brake system of the electric vehicle further includes negative pressure detecting means for detecting negative pressure supplied to the master back, and the control means is only one of the first and second electric negative pressure pumps. When the negative pressure detected by the negative pressure detecting means is less than a predetermined value, it is preferable to drive the first and second electric negative pressure pumps regardless of the vehicle speed.

  In the case of the above-described configuration, basically, the first and second electric negative pressure pumps are selectively used according to the vehicle speed in order to reduce the drive noise of the electric negative pressure pump. However, when the negative pressure supplied to the master back is too small, it is necessary to increase the negative pressure supplied to the master back immediately. Therefore, when the negative pressure is less than the predetermined value, priority is given to the rapid increase of the negative pressure over the reduction of the driving sound of the electric negative pressure pump. Specifically, both the first and second electric negative pressure pumps are driven regardless of the vehicle speed. Thereby, the negative pressure of the master back can be secured immediately.

  The control means preferably stops the first and second electric negative pressure pumps when the negative pressure detected by the negative pressure detection means becomes equal to or greater than the predetermined value.

  That is, when both the first and second electric negative pressure pumps are driven and priority is given to a rapid increase in negative pressure over a reduction in driving sound of the electric negative pressure pump, the negative pressure supplied to the master back is reduced. When the pressure becomes equal to or greater than the predetermined value, the first and second electric negative pressure pumps are stopped. Thereby, unnecessary driving of the electric negative pressure pump can be suppressed, power consumption required for the driving can be suppressed, and driving sound can be suppressed.

  Another aspect of the present invention is directed to a method for controlling an electric negative pressure pump in a brake system of an electric vehicle including a master back and an electric negative pressure pump that supplies negative pressure to the master back. The electric negative pressure pump control method includes a vehicle speed detecting step for detecting a vehicle speed, and a first electric negative pressure pump having a relatively small capacity when the vehicle speed detected in the vehicle speed detecting step is less than a predetermined vehicle speed. And a driving step for reducing the rotational speed of the second electric negative pressure pump having a capacity larger than that of the first electric negative pressure pump than the rotational speed when the vehicle speed is equal to or higher than the predetermined vehicle speed.

  In the case of the above configuration, when the vehicle speed is equal to or higher than the predetermined vehicle speed, at least the second electric negative pressure pump is driven at a predetermined rotation speed. On the other hand, when the vehicle speed is less than the predetermined vehicle speed, the first electric negative pressure pump is driven, and the rotation speed of the second electric negative pressure pump is reduced below the predetermined rotation speed when the vehicle speed is equal to or higher than the predetermined vehicle speed. . Here, in order to reduce the rotation speed of the second electric negative pressure pump, it is assumed that the second electric negative pressure pump is brought into a non-driving state where the rotation speed is zero.

  When the vehicle speed is less than the predetermined vehicle speed, the road noise is small and the vehicle noise is relatively low. Since the first electric negative pressure pump has a smaller capacity than the second electric negative pressure pump, the driving sound is low. That is, when the vehicle noise is low and the vehicle speed is lower than the predetermined vehicle speed, the rotational speed of the second electric negative pressure pump is reduced and the first electric negative pressure pump is driven, thereby making the pump driving sound inconspicuous. Can be made.

  In addition, since the operation range in which the rotation speed of the second electric negative pressure pump is reduced and the first electric negative pressure pump is driven is a relatively low speed range in which the vehicle speed is less than the predetermined vehicle speed, the required negative pressure of the master back is small. Therefore, even when the first electric negative pressure pump with a small capacity is driven and the rotation speed of the second electric negative pressure pump with a large capacity is reduced, the required negative pressure can be met.

  Further, in a driving region where the vehicle speed is equal to or higher than a predetermined vehicle speed, the required negative pressure increases because the vehicle speed increases and a large braking force is required. In this case, the second electric negative pressure pump is driven at a higher rotational speed than when the vehicle speed is lower than the predetermined vehicle speed, and the capacity of the second electric negative pressure pump is larger than that of the first electric negative pressure pump. Since it is large, the required negative pressure can be secured. Further, when the vehicle speed is increased, vehicle noise such as road noise increases, so even if the number of rotations of the second electric negative pressure pump having a relatively large capacity is increased, the drive sound is not a problem.

  Further, in the driving step, when the vehicle speed detected in the vehicle speed detecting step is less than the predetermined vehicle speed, the second electric negative pressure pump may be set in a non-driving state where the rotation speed is zero.

  According to the above configuration, when the vehicle speed is lower than the predetermined vehicle speed, the second electric negative pressure pump is not driven, so that the driving sound of the pump can be made less noticeable.

  Further, by properly using the first electric negative pressure pump and the second electric negative pressure pump with a predetermined vehicle speed as a boundary, it is possible to reduce the deviation in driving time of the two electric negative pressure pumps. Thereby, the reliability of the electric negative pressure pump can be improved.

  The method of controlling the electric negative pressure pump further includes a negative pressure detecting step of detecting a negative pressure supplied to the master back, and the driving step includes either one of the first and second electric negative pressure pumps. It is preferable to drive the first and second electric negative pressure pumps regardless of the vehicle speed when only the pressure is used and the negative pressure detected in the negative pressure detection step is less than a predetermined value. .

  In the case of the above-described configuration, basically, the first and second electric negative pressure pumps are selectively used according to the vehicle speed in order to reduce the drive noise of the electric negative pressure pump. However, when the negative pressure supplied to the master back is too small, it is necessary to increase the negative pressure supplied to the master back immediately. Therefore, when the negative pressure is less than the predetermined value, priority is given to the rapid increase of the negative pressure over the reduction of the driving sound of the electric negative pressure pump. Specifically, both the first and second electric negative pressure pumps are driven regardless of the vehicle speed. Thereby, the negative pressure of the master back can be secured immediately.

  Further, in the driving step, it is preferable that the first and second electric negative pressure pumps are stopped when the negative pressure detected in the negative pressure detection step becomes equal to or greater than the predetermined value.

  That is, when both the first and second electric negative pressure pumps are driven and priority is given to a rapid increase in negative pressure over a reduction in driving sound of the electric negative pressure pump, the negative pressure supplied to the master back is reduced. When the pressure becomes equal to or greater than the predetermined value, the first and second electric negative pressure pumps are stopped. Thereby, unnecessary driving of the electric negative pressure pump can be suppressed, power consumption required for the driving can be suppressed, and driving sound can be suppressed.

  According to the present invention, the first electric negative pressure pump having a relatively small capacity is driven at a low speed or when the vehicle is stopped, and the rotational speed of the second electric negative pressure pump having a relatively large capacity is reduced. Noise due to the negative pressure pump can be suppressed.

It is the schematic of the system configuration | structure of the brake system of the electric vehicle which concerns on embodiment. It is a flowchart of starting control. It is a flowchart of normal control. It is a graph which shows the time change of the negative pressure by a sub pump and a main pump in creep stop mode. It is a graph which shows the time change of the negative pressure by sub pump 2S and main pump 2M in run mode.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram of a system configuration of a brake system for an electric vehicle according to an embodiment.

  The brake system 100 according to the present embodiment is mounted on an electric vehicle driven by an electric motor. The brake system 100 amplifies the pedal force of a brake pedal (not shown) using a negative pressure and transmits it to a master cylinder (not shown), and a sub electric negative pressure that supplies the master back 1 with a negative pressure. Master back the pump (simply referred to as “sub pump”) 2S, main electric negative pressure pump (also simply referred to as “main pump”) 2M for supplying negative pressure to the master back 1, and the sub pump 2S and main pump 2M. 1, a supply path 3 connected to 1, a discharge path 4 for discharging air from the sub pump 2 </ b> S and the main pump 2 </ b> M, first and second boost sensors 51 and 52 for detecting negative pressure supplied to the master back, The first and second negative pressure tanks 61 and 62 disposed in the supply path 3; the first to fourth check valves 71 to 74 disposed in the supply path 3; An exhaust chamber 8 which is disposed in the path 4, a vehicle speed sensor 9 for detecting a vehicle speed of the electric vehicle, and a control unit 10 for controlling the driving of the subordinate fuel pump 2S and the main pump 2M. The vehicle speed sensor 9 constitutes vehicle speed detection means, and the control unit 10 constitutes control means.

  The master back 1 has two pressure chambers separated by a diaphragm. Negative pressure is supplied to the two pressure chambers, and the inside thereof is basically negative pressure. When the brake pedal is depressed, one pressure chamber is opened to the atmosphere, and a pressure difference is generated between the two pressure chambers. The master back 1 amplifies the depression force of the brake pedal by this pressure difference and transmits it to the master cylinder. The configuration of the master back 1 is not particularly limited, and any configuration can be adopted.

  The sub pump 2S and the main pump 2M are well-known electric negative pressure pumps. The sub pump 2S has a smaller capacity than the main pump 2M. That is, the sub pump 2S generates less negative pressure than the main pump 2M, and accordingly, the drive sound is also smaller. The sub pump 2S constitutes a first electric negative pressure pump, and the main pump 2M constitutes a second electric negative pressure pump.

  The supply path 3 has a first branch path 31 extending from the sub-pump 2S, a second branch path 32 extending from the main pump 2M, and a merge where the first branch path 31 and the second branch path 32 are joined and connected to the master back 1. And a path 33. The first branch path 31 and the combined flow path 33 constitute a first supply path, and the second branch path 32 and the combined flow path 33 constitute a second supply path. The first supply path and the second supply path are parallel to each other.

  In the joint channel 33, the first and second boost sensors 51 and 52 are arranged in parallel. The first and second boost sensors 51 and 52 are sensors that detect a negative pressure in the combined flow path 33, that is, a negative pressure supplied to the master back 1. Two boost sensors are provided for fail-safe. Basically, the detection result of the first boost sensor 51 is used for control to be described later. The second boost sensor 52 is used to determine whether the first and second boost sensors 51 and 52 are operating normally by comparing the detection result with the detection result of the first boost sensor 51. . These first and second boost sensors 51 and 52 constitute negative pressure detecting means.

  The second branch path 32 is provided with the first negative pressure tank 61 and the second negative pressure tank 62 in order from the upstream side. The first and second negative pressure tanks 61 and 62 are tanks having the same volume, and are for securing a negative pressure generated by the main pump 2M. That is, the first and second negative pressure tanks 61 and 62 are basically maintained in a negative pressure state at all times, and can recover quickly even if the negative pressure of the master back 1 is reduced. Yes.

  Further, a first check valve 71 is provided in the combined flow path 33. The first check valve 71 allows only the flow from the master back 1 to the downstream side.

  A second check valve 72 is provided in the first branch path 31. The second check valve 72 allows only the flow toward the sub pump 2S.

  A third check valve 73 is provided at a portion of the second branch path 32 between the first negative pressure tank 61 and the second negative pressure tank 62. The third check valve 73 allows only the flow from the first negative pressure tank 61 to the second negative pressure tank 62. Further, a fourth check valve 74 is provided at a portion of the second branch path 32 between the second negative pressure tank 62 and the main pump 2M. The fourth check valve 74 allows only the flow from the second negative pressure tank 62 to the main pump 2M.

  The discharge path 4 includes a first branch path 41 extending from the sub pump 2S, a second branch path 42 extending from the main pump 2M, and a merge path 43 extending by the merge of the first branch path 41 and the second branch path 42. have.

  An exhaust chamber 8 is provided in the combined flow path 43. The exhaust chamber 8 is for reducing the exhaust sound (especially high frequency component) of the air discharged from the main pump 2M and the sub pump 2S. By providing the exhaust chamber 8 in the combined flow path 43, the main pump 2M and the sub pump 2S are made common. Thereby, cost reduction and effective utilization of space can be aimed at.

  The control unit 10 is configured by an arbitrary CPU, and may include a ROM, a RAM, and the like. First and second boost sensors 51 and 52 and a vehicle speed sensor 9 are connected to the control unit 10 and their detection signals are input. The control unit 10 is connected to a sub pump 2S and a main pump 2M. The sub pump 2S and the main pump 2M are controlled to be driven and stopped by a control signal from the control unit 10.

  When the main pump 2M is driven, the air upstream of the main pump 2M is sucked and discharged downstream. That is, the air in the pressure chamber of the master back 1 is sucked into the main pump 2M via the combined flow path 33, the second branch path 32, the first negative pressure tank 61, and the second negative pressure tank 62, and the second branch path 42. The gas is discharged through the combined flow path 43 and the exhaust chamber 8.

  On the other hand, when the sub pump 2S is driven, the air upstream of the sub pump 2S is sucked and discharged downstream. That is, the air in the pressure chamber of the master back 1 is sucked into the sub-pump 2S through the combined flow path 33 and the first branch path 31, and is discharged through the first branch path 41, the combined flow path 43, and the exhaust chamber 8.

  Here, by providing the second check valve 72 in the first branch path 31 and the third check valve 73 in the second branch path 32, a negative pressure supply system by the sub pump 2S and a negative pressure supply system by the main pump 2M are provided. Can function independently. That is, when driving the sub pump 2S, it is possible to prevent the sub pump 2S from drawing air from the main pump 2M side via the second branch path 32, and to draw air from the master back 1. On the other hand, when driving the main pump 2M, it is possible to prevent the main pump 2M from drawing air from the sub pump 2S side via the first branch path 31, and to draw air from the master back 1.

  Further, the second check valve 72 of the first branch path 31 can prevent air from flowing back upstream, that is, toward the master back 1 when the sub pump 2S is stopped. That is, the negative pressure state of the master back 1 can be maintained when the sub pump 2S is stopped.

  Similarly, by providing the fourth check valve 74 in the second branch path 32, it is possible to prevent air from flowing backward toward the upstream side, that is, the master back 1 when the main pump 2M is stopped. That is, the negative pressure state of the first and second negative pressure tanks 61 and 62 and the master back 1 can be maintained when the main pump 2M is stopped.

  Further, by providing the first check valve 71 in the combined flow path 33, even if any failure occurs downstream of the first check valve 71, the negative pressure state of the master back 1 is maintained. Can do.

  Next, drive control of the sub pump 2S and the main pump 2M by the control unit 10 will be described.

  When the electric vehicle is started, the control unit 10 first performs start control. This start-up control is a control for increasing the negative pressure of the master back 1 to a predetermined negative pressure (hereinafter referred to as a reference negative pressure) Pr. FIG. 2 shows a flowchart of activation control.

  First, the control part 10 detects the negative pressure Pb of the master back 1 in step Sa1. Specifically, the control unit 10 reads detection signals from the first and second boost sensors 51 and 52. The control unit 10 detects the negative pressure Pb of the master back 1 based on the detection signal of the first boost sensor 51, and based on the difference between the detection signal of the first boost sensor 51 and the detection signal of the second boost sensor 52. Thus, failure determination of the first and second boost sensors 51 and 52 is performed. The control unit 10 determines that the first and second boost sensors 51 and 52 are normal when the difference between the detection signals is less than a predetermined value, and when the difference between the detection signals is equal to or greater than the predetermined value. Then, it is determined that one of the first and second boost sensors 51 and 52 is out of order.

  Subsequently, in step Sa2, the control unit 10 determines whether or not the negative pressure Pb is larger than a predetermined threshold value Ps. Here, “large negative pressure” means that the absolute value of negative pressure is large, and “small negative pressure” means that the absolute value of negative pressure is small. The predetermined threshold value Ps is a negative pressure that is a threshold value, that is, a negative value. That is, “the negative pressure Pb is larger than the predetermined threshold value Ps” means that the absolute value of the negative pressure Pb is larger than the absolute value of the threshold value. The threshold value Ps is smaller than the reference negative pressure Pr (that is, the absolute value of the threshold value Ps is smaller than the absolute value of the reference negative pressure Pr). When the negative pressure Pb is larger than the threshold value Ps, the process proceeds to step Sa3. When the negative pressure Pb is smaller than the threshold value Ps, the process proceeds to step Sa4.

  In step Sa3, the control unit 10 drives the sub pump 2S. On the other hand, in step Sa4, the control unit 10 drives the main pump 2M. That is, if the negative pressure Pb is large to some extent, the difference from the reference negative pressure is small. Therefore, the negative pressure Pb is increased using the sub pump 2S. If the negative pressure is relatively small, the difference from the reference negative pressure is Since the difference is large, the main pump 2M is used to increase the negative pressure Pb.

  Thereafter, the control unit 10 detects the negative pressure Pb again in step Sa5. In step Sa6, the control unit 10 determines whether or not the negative pressure Pb is greater than a predetermined reference negative pressure Pr. When the negative pressure Pb is equal to or lower than the reference negative pressure Pr, the process returns to step Sa5. When the negative pressure Pb is higher than the reference negative pressure Pr, the process proceeds to normal control described later. That is, until the negative pressure Pb exceeds the reference negative pressure Pr, the pump selected in step Sa3 or step Sa4 is continuously driven and the start-up control is continued.

  When the negative pressure Pb of the master back 1 becomes larger than the reference negative pressure Pr by the above startup control, the control unit 10 performs normal control for adjusting the negative pressure Pb by controlling the driving of the main pump 2M and the sub pump 2S. By this normal control, the negative pressure Pb of the master back 1 is controlled to a predetermined state. FIG. 3 shows a flowchart of normal control.

  First, the controller 10 detects the vehicle speed V and the negative pressure Pb of the master back 1 in step Sb1. Specifically, the control unit 10 reads the detection signal of the vehicle speed sensor 9 and detects the vehicle speed V. This corresponds to the vehicle speed detection step. Further, the control unit 10 reads the detection signal of the first boost sensor 51 and detects the negative pressure Pb of the master back 1. This corresponds to the negative pressure detection step. At this time, the control unit 10 also reads the detection signal of the second boost sensor 52 as in Step Sa1, and based on the difference between the detection signal of the first boost sensor 51 and the detection signal of the second boost sensor 52. Thus, failure determination of the first and second boost sensors 51 and 52 is performed.

  Next, in step Sb2, the control unit 10 determines whether or not the vehicle speed V is slower than the reference vehicle speed V0. The reference vehicle speed V0 is a vehicle speed at which the driving sound of the main pump 2M is not bothered by noise such as road noise of an electric vehicle, and is, for example, a creep vehicle speed (vehicle speed during creep running).

  When the vehicle speed V is slower than the reference vehicle speed V0 (for example, when creeping or stopping), the control unit 10 is in a creep stop mode in which negative pressure is supplied to the master back 1 mainly using the sub pump 2S. Become. In detail, the control part 10 progresses to step Sb3, and sets the value for creep stop modes to various negative pressure determination values. Here, Pson is a negative pressure serving as a reference for starting the driving of the sub pump 2S. Psoff is a negative pressure serving as a reference for stopping the sub pump 2S. Pmon is a negative pressure that serves as a reference for starting the driving of the main pump 2M. Pmoff is a negative pressure that serves as a reference for stopping the main pump 2M. In step Sb3, Pson_0 is set as Pson, Psoff_0 is set as Psoff, Pmon_0 is set as Pmon, and Pmoff_0 is set as Pmoff. Since these negative pressure determination values are negative pressures, they are negative values. Among the four values, the absolute value of Pmon_0 is the smallest, and then the absolute value of Pson_0 is the smallest. Psoff_0 and Pmoff_0 have the same value. The reference negative pressure Pr has the same value as Psoff_0 and Pmoff_0.

  On the other hand, when the vehicle speed V is equal to or higher than the reference vehicle speed V0 (for example, during normal travel), the control unit 10 is in a travel mode in which negative pressure is supplied to the master back 1 mainly using the main pump 2M. In detail, the control part 10 progresses to step Sb4, and sets the value for driving modes to various negative pressure determination values. Specifically, Pson_1 is set as Pson, Psoff_1 is set as Psoff, Pmon_1 is set as Pmon, and Pmoff_1 is set as Pmoff. Since these negative pressure determination values are negative pressures, they are negative values. Among the four values, the absolute value of Pson_1 is the smallest, and increases in the order of the absolute value of Psoff_1, the absolute value of Pmon_1, and the absolute value of Pmoff_1. Note that the absolute value of Pson_1 is larger than the absolute value of Pmon_0 and smaller than the absolute value of Pson_0. The absolute value of Psoff_1 is the same value as the absolute value of Pson_0. The absolute value of Pmon_1 and the absolute value of Pmoff_1 are larger than the absolute value of Pmoff_0.

  Subsequently, in step Sb5, the control unit 10 determines whether or not the negative pressure Pb is smaller than Pson. When the negative pressure Pb is smaller than Pson, the control unit 10 drives the sub pump 2S at a predetermined rotational speed (for example, rated rotational speed (rated rotational speed)) in step Sb6 (that is, the sub pump 2S has already been operated). If the sub pump 2S is stopped, it is driven when it is driven, and is driven when the sub pump 2S is stopped. On the other hand, when the negative pressure Pb is equal to or higher than Pson, the control unit 10 proceeds to step Sb7 without changing the state of the sub pump 2S.

  Next, the control part 10 determines whether the negative pressure Pb is smaller than Pmon in step Sb7. When the negative pressure Pb is smaller than Pmon, the control unit 10 drives the main pump 2M at a predetermined rotation speed (for example, a rated rotation speed (rated rotation speed)) in step Sb8. On the other hand, when the negative pressure Pb is equal to or higher than Pmon, the control unit 10 proceeds to step Sb9 without changing the state of the main pump 2M.

  In the present embodiment, since the absolute value of Pmon is smaller than the absolute value of Pson, the negative pressure Pb is smaller than Pson whenever the negative pressure Pb is smaller than Pmon. That is, whenever the main pump 2M is driven, the sub pump 2S is also driven.

  In the flow of these steps Sb5 to Sb8, the control unit 10 controls the start of driving of the pump. That is, the control unit 10 starts driving the main pump 2M and the sub pump 2S when the negative pressure Pb is smaller than Pmon, and starts driving only the sub pump 2S when the negative pressure Pb is equal to or higher than Pmon and smaller than Pson. When the negative pressure Pb is equal to or higher than Pson, neither the main pump 2M nor the sub pump 2S is driven. These steps Sb5 to Sb8 and steps Sb9 to Sb12 described later correspond to driving steps.

  Thereafter, in step Sb9, the control unit 10 determines whether or not the negative pressure Pb is larger than Psoff. When the negative pressure Pb is larger than Psoff, the control unit 10 sets the sub pump 2S to the non-driven state (rotation speed is 0) in step Sb10 (that is, when the sub pump 2S is driven). If the sub-pump 2S is already stopped, the stopped state is maintained as it is. On the other hand, when the negative pressure Pb is equal to or lower than Psoff, the control unit 10 proceeds to step Sb11 without changing the state of the sub pump 2S.

  Next, the control part 10 determines whether the negative pressure Pb is larger than Pmoff in step Sb11. When the negative pressure Pb is larger than Pmoff, the control unit 10 puts the main pump 2M into a non-driven state in step Sb12. On the other hand, when the negative pressure Pb is equal to or higher than Pmoff, the control unit 10 proceeds to return without changing the state of the main pump 2M.

  In the present embodiment, since Psoff and Pmoff are the same value, the main pump 2M is also in a non-driven state whenever the sub pump 2S is in a non-driven state.

  In the flow of these steps Sb9 to Sb12, the control unit 10 controls the drive stop of the pump. That is, the control unit 10 stops driving the main pump 2M and the sub pump 2S when the negative pressure Pb is larger than Psoff and Pmoff.

  Hereinafter, specific operations of the sub pump 2S and the main pump 2M controlled by such a flow will be described. FIG. 4 is a graph showing the time variation of the negative pressure due to the sub pump 2S and the main pump 2M in the creep stop mode, and FIG. 5 is a graph showing the time variation of the negative pressure due to the sub pump 2S and the main pump 2M in the travel mode.

  First, the creep stop mode will be described. Here, a case where the creep stop mode is started from a state immediately after the start control is completed will be described. Immediately after the start control is completed, the negative pressure Pb exceeds the reference negative pressure Pr, and the sub pump 2S or the main pump 2M is driven. Since the reference negative pressure Pr is the same value as Pmoff_0 and Psoff_0, it is driven because the negative pressure Pb exceeds Pmoff_0 and Psoff_0 regardless of which of the sub pump 2S and the main pump 2M is driven. One pump is stopped, and both pumps are stopped.

  Here, even if both the sub pump 2S and the main pump 2M are stopped, the negative pressure Pb is allowed due to the structure of the master back 1, the first check valve 71, and the first and second negative pressure tanks 61 and 62. Maintained as much as possible. However, when the driver performs a braking operation, the negative pressure Pb decreases. Then, the negative pressure Pb eventually becomes smaller than Pson_0. When the negative pressure Pb becomes smaller than Pson_0, the control unit 10 starts driving the sub pump 2S. When the sub pump 2S is driven, the negative pressure Pb starts to increase. Eventually, the negative pressure Pb exceeds Psoff_0. Then, the control part 10 stops the subpump 2S. As described above, once the negative pressure Pb exceeds Pmoff_0 and Psoff_0, the control unit 10 repeats driving and stopping of the sub pump 2S so that the negative pressure Pb falls between Pson_0 and Psoff_0.

  Even if the negative pressure Pb decreases and becomes smaller than Pson_0, when the sub pump 2S is driven, the negative pressure Pb usually starts to increase. Therefore, the negative pressure Pb does not become much smaller than Pson_0. However, when the driver executes the pumping brake, the negative pressure Pb rapidly decreases. As a result, the negative pressure Pb may be significantly lower than Pson_0 and smaller than Pmon_0. Thus, when the negative pressure Pb rapidly decreases and becomes smaller than Pmon_0, the control unit 10 starts driving the main pump 2M in addition to the sub pump 2S. When the main pump 2M is driven, the negative pressure Pb increases as shown in the left diagram of FIG. When the sub pump 2S and the main pump 2M are driven, the negative pressure Pb increases rapidly as compared to the case where the sub pump 2S or the main pump 2M is driven alone (that is, the left and right diagrams in FIG. 4). Negative pressure increases with a larger slope than the figure). Thereby, the negative pressure Pb is rapidly recovered.

  Thus, in the creep stop mode, basically, the sub pump 2S supplies a negative pressure to the master back 1, and when a large negative pressure is required, the main pump 2M is driven in addition to the sub pump 2S.

  In FIG. 4, the driving of the main pump 2M is started when the negative pressure Pb is Pmon_0. However, when the negative pressure Pb is smaller than Pmon_0, the driving of the main pump 2M is started from that point. . The same applies to the sub pump 2S. When the negative pressure Pb is smaller than Pson_0, the driving of the sub pump 2S is started from that point.

  In the above description, the case where the creep stop mode is started when the negative pressure Pb is the reference negative pressure Pr has been described. However, when the negative pressure Pb is smaller than Pmon_0 at the start of the creep stop mode, the sub pump 2S and the main The driving of the pump 2M is started, and when the negative pressure Pb is smaller than Pson_0, the driving of the sub pump 2S is started.

  Next, the travel mode will be described. Here, a case will be described in which the travel mode is started from a state immediately after completion of the start control. Immediately after the start control is completed, the negative pressure Pb exceeds the reference negative pressure Pr, and the sub pump 2S or the main pump 2M is driven. Since the reference negative pressure Pr has the same value as Pmoff — 0 and Psoff — 0, the negative pressure Pb is larger than Psoff — 1 and smaller than Pmon — 1. Therefore, when the sub pump 2S is driven, the sub pump 2S is stopped and the driving of the main pump 2M is started. On the other hand, when the main pump 2M is driven, the state is maintained. As a result, as shown in the left diagram of FIG. 5, the negative pressure Pb increases and eventually the negative pressure Pb exceeds Pmoff_1. When the negative pressure Pb exceeds Pmoff_1, the main pump 2M is stopped. In FIG. 5, the driving of the main pump 2M is started when the negative pressure Pb is Pmon_1. However, when the negative pressure Pb is smaller than Pmon_1, the driving of the main pump 2M is started from that point. .

  When the driver performs a brake operation in a state where both the sub pump 2S and the main pump 2M are stopped, the negative pressure Pb decreases as described above. Then, the negative pressure Pb eventually becomes smaller than Pmon_1. When the negative pressure Pb becomes smaller than Pmon_1, the control unit 10 starts driving the main pump 2M. When the main pump 2M is driven, the negative pressure Pb starts to increase. Eventually, the negative pressure Pb exceeds Pmoff_1. Then, the control unit 10 stops the main pump 2M. Thus, once the negative pressure Pb exceeds Pmoff_1, the control unit 10 repeats driving and stopping of the main pump 2M so that the negative pressure Pb falls between Pmon_1 and Pmoff_1.

  Even if the negative pressure Pb decreases and becomes smaller than Pmon_1, when the main pump 2M is driven, the negative pressure Pb usually starts to increase. Therefore, the negative pressure Pb does not become much smaller than Pmon_1. However, when the driver executes the pumping brake, the negative pressure Pb rapidly decreases. As a result, the negative pressure Pb may be significantly lower than Pmon_1 and lower than Pson_1. Thus, when the negative pressure Pb rapidly decreases and becomes smaller than Pson_1, the control unit 10 starts driving the sub pump 2S in addition to the main pump 2M. When the sub pump 2S is driven, the negative pressure Pb increases as shown in the right diagram of FIG. Since Pson_1 is smaller than Pmon_1, the negative pressure Pb is always smaller than Pmon_1 when the negative pressure Pb is smaller than Pson_1. Therefore, when the negative pressure Pb is smaller than Pson_1, the driving of the main pump 2M is always started in addition to the sub pump 2S. Therefore, the negative pressure Pb increases rapidly as compared with the case where the main pump 2M and the sub pump 2S are driven alone (that is, the negative pressure increases with a larger slope than the left and right diagrams in FIG. 5). To do). Thereby, the negative pressure Pb is rapidly recovered. If the negative pressure Pb exceeds Psoff_1, the sub pump 2S is stopped, and only the main pump 2M is driven until the negative pressure Pb reaches Pmoff_1. In FIG. 5, the driving of the sub pump 2S is started when the negative pressure Pb is Pson_1. However, when the negative pressure Pb is smaller than Pson_1, the driving of the sub pump 2S is started from that point.

  As described above, in the traveling mode, the main pump 2M basically supplies a negative pressure to the master back 1, and when a large negative pressure is required, the sub pump 2S is driven in addition to the main pump 2M.

  In the above description, the case where the traveling mode is started when the negative pressure Pb is the reference negative pressure Pr has been described. However, when the negative pressure Pb is smaller than Pson_1 at the start of the traveling mode, the sub-pump 2S and the main pump 2M. When the negative pressure Pb is larger than Pmon_1, the drive of the pump driven by the start control is maintained.

  Basically, the sub pump 2S and the main pump 2M are controlled according to the vehicle speed V and the negative pressure Pb. However, if either the sub pump 2S or the main pump 2M breaks down, the vehicle speed V or the negative pump 2M is controlled. Regardless of the pressure Pb, the negative pressure is adjusted using a normal pump.

  Therefore, according to the present embodiment, in the driving region where the vehicle speed is relatively slow (including when the vehicle is stopped), the pump drive sound is noticeable by supplying negative pressure to the master back 1 mainly using the sub pump 2S. Can be prevented. That is, in a driving region where the vehicle speed is relatively slow, vehicle noise such as road noise is small. Therefore, the driving sound of the pump tends to be more noticeable than when the vehicle speed is high. However, since the sub pump 2S has a smaller capacity than the main pump 2M, the driving sound is also small. In other words, in a driving environment where the vehicle noise is small, it is possible to make it difficult for the occupant to recognize the driving sound of the pump by using the sub-pump 2S having a low driving sound.

  Further, in a driving region where the vehicle speed is relatively slow, such as during creep running or when the vehicle is stopped, the negative pressure required for the master back 1 is small, so even the sub pump 2S can meet the required negative pressure of the master back 1. Can do.

  Further, in a driving region where the vehicle speed is relatively high, the negative pressure is supplied to the master back 1 mainly using the main pump 2M. Can respond to pressure. And in the driving | running | working area | region where a vehicle speed is comparatively fast, since vehicle noises, such as road noise, are a certain amount loud, the drive sound of a pump is not conspicuous. That is, the driving sound of the pump is not easily recognized as noise by the occupant.

  Further, by using two pumps, even when one of the pumps fails, the other pump can supply negative pressure, which is preferable from the viewpoint of fail-safe.

  Furthermore, even when two pumps are used, not only one of the pumps is mainly used, but the sub-pump 2S and the main pump 2M are selectively used to reduce the drive time bias, thereby improving the reliability of the pump. Can be improved.

  Further, by making the volume of the first supply path between the sub pump 2S and the master back 1 smaller than the volume of the second supply path between the main pump 2M and the master back 1, the sub pump 2S having a small capacity can be used. Even if it exists, it can respond to the required negative pressure of the master back 1 immediately, and can reduce the drive time of the subpump 2S and can suppress power consumption.

  Further, the negative pressure tanks 61 and 62 are provided in the second supply path of the main pump 2M, while the negative pressure tank is not provided in the first supply path of the sub-pump 2S having a relatively small capacity. The response of the negative pressure adjustment by the sub pump 2S to the required negative pressure can be further enhanced.

  Further, by making the exhaust chamber 8 common to the main pump 2M and the sub pump 2S, it is possible to achieve cost reduction and effective utilization of space.

<< Other Embodiments >>
The present invention may be configured as follows with respect to the embodiment.

  In the creep stop mode, when the negative pressure Pb becomes too small (specifically, when the negative pressure Pb becomes smaller than Pmon_0), both the sub pump 2S and the main pump 2M are driven. However, it is not limited to this. For example, in such a case, the sub pump 2S may be stopped and only the main pump 2M may be driven.

  In the creep stop mode, the negative pressure determination value Psoff_0 for stopping the sub pump 2S and the negative pressure determination value Pmoff_0 for stopping the main pump 2M are set to the same value, but they may be different from each other. In that case, either may be made higher.

  In the first place, the magnitude relationship of Ps, Pr, Pson_0, Psoff_0, Pmon_0, Pmoff_0, Pson_1, Psoff_1, Pmon_1, Pmoff_1, and the like is merely an example, and is not limited thereto.

  Furthermore, the control of the sub pump 2S and the main pump 2M in the creep stop mode and the traveling mode is an example, and is not limited thereto. In the creep stop mode, any control can be adopted as long as a negative pressure is supplied to the master back 1 by driving a pump having a capacity smaller than that of the pump used in the traveling mode. For example, in the creep stop mode, only the sub pump 2S may be driven without driving the main pump 2M at all. However, in the configuration in which the capacity of the sub-pump 2S cannot cope with the maximum required negative pressure of the master back 1, it is preferable to use the main pump 2M urgently as in the above embodiment. In that case, both the sub pump 2S and the main pump 2M may be driven as in the above embodiment, or only the main pump 2M may be driven. In the traveling mode, any control can be adopted as long as a negative pressure is supplied to the master back 1 by driving a pump having a capacity larger than that of the pump used in the creep stop mode. For example, in the travel mode, only the main pump 2M may be driven without driving the sub pump 2S at all. Alternatively, both the sub pump 2S and the main pump 2M may always be driven.

  In addition, although two negative pressure tanks 61 and 62 are provided in the second supply path between the main pump 2M and the master back 1, either one or both may be omitted. Furthermore, a negative pressure tank may be provided in the first supply path between the sub pump 2S and the master back 1.

  Further, the first to fourth check valves 71 to 74 may be appropriately selected according to the configurations of the sub pump 2S and the main pump 2M and the circuit configuration. A further check valve may be provided.

  The exhaust chamber 8 is common to the sub pump 2S and the main pump 2M, but may be provided separately.

  Further, in the present embodiment, in the creep stop mode in which the vehicle speed is less than the predetermined vehicle speed, the sub pump 2S is driven and the main pump 2M is not driven, but the main pump 2M may be driven. In this case, the drive rotation speed of the main pump 2M in the creep stop mode is made lower than the drive rotation speed in the travel mode. As a means for changing the driving speed, it is conceivable to change the driving voltage of the pump by duty control or the like. Even if the main pump 2M is not completely driven, the driving sound of the main pump 2M can be suppressed only by reducing the rotational speed.

  In addition, the above embodiment is an essentially preferable illustration, Comprising: It does not intend restrict | limiting the range of this invention, its application thing, or its use.

  As described above, the present invention is useful for the brake system of an electric vehicle and the control method of the electric negative pressure pump.

1 Master back 2S Sub pump (1st electric negative pressure pump)
2M main pump (second electric negative pressure pump)
31 First branch path (first supply path)
32 Second branch path (second supply path)
33 Combined flow path (first supply path, second supply path)
51 1st boost sensor (negative pressure detection means)
52 Second boost sensor (negative pressure detecting means)
9 Vehicle speed sensor (vehicle speed detection means)
10 Control unit (control means)
100 brake system

Claims (9)

A brake system for an electric vehicle with a master back,
First and second electric negative pressure pumps for supplying negative pressure to the master back;
A first supply path connecting the first electric negative pressure pump to the master back;
A second supply path for communicating the second electric negative pressure pump to the master back;
Control means for controlling the driving of the first and second electric negative pressure pumps;
Vehicle speed detecting means for detecting the vehicle speed of the electric vehicle,
The first electric negative pressure pump has a smaller capacity than the second electric negative pressure pump,
The control means drives the first electric negative pressure pump when the vehicle speed detected by the vehicle speed detection means is less than a predetermined vehicle speed, and sets the rotation speed of the second electric negative pressure pump to the predetermined vehicle speed. A brake system for an electric vehicle, characterized in that the number of revolutions is reduced more than the above. The brake system for an electric vehicle according to claim 1,
The brake system for an electric vehicle, wherein the control means sets the second electric negative pressure pump in a non-driven state when the vehicle speed detected by the vehicle speed detection means is less than the predetermined vehicle speed. The electric vehicle brake system according to claim 1 or 2,
The first supply path and the second supply path are parallel to each other,
The brake system for an electric vehicle, wherein the first supply path has a smaller volume than the second supply path. The brake system for an electric vehicle according to any one of claims 1 to 3,
A negative pressure detecting means for detecting a negative pressure supplied to the master back;
The control means adjusts the vehicle speed when only one of the first and second electric negative pressure pumps is in use and the negative pressure detected by the negative pressure detection means is less than a predetermined value. Regardless, a brake system for an electric vehicle that drives the first and second electric negative pressure pumps. The brake system for an electric vehicle according to claim 4,
The control system stops the first and second electric negative pressure pumps when the negative pressure detected by the negative pressure detection means exceeds the predetermined value. . An electric negative pressure pump control method for supplying negative pressure to a master back in a brake system of an electric vehicle,
A vehicle speed detection step for detecting the vehicle speed;
When the vehicle speed detected in the vehicle speed detection step is less than a predetermined vehicle speed, the first electric negative pressure pump having a relatively small capacity is driven, while the second electric negative having a capacity larger than that of the first electric negative pressure pump. And a driving step of reducing the rotational speed of the pressure pump below the rotational speed when the vehicle speed is equal to or higher than the predetermined vehicle speed. In the control method of the electric negative pressure pump according to claim 6,
In the driving step, when the vehicle speed detected in the vehicle speed detecting step is less than the predetermined vehicle speed, the second electric negative pressure pump is set in a non-driven state. In the control method of the electric negative pressure pump according to claim 6 or 7,
A negative pressure detecting step of detecting a negative pressure supplied to the master back;
In the driving step, when only one of the first and second electric negative pressure pumps is in use and the negative pressure detected in the negative pressure detecting step is less than a predetermined value, the vehicle speed is increased. Regardless, a method of controlling the electric negative pressure pump, wherein the first and second electric negative pressure pumps are driven. In the control method of the electric negative pressure pump according to claim 8,
In the driving step, when the negative pressure detected in the negative pressure detection step becomes equal to or greater than the predetermined value, the first and second electric negative pressure pumps are stopped. Control method.

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