JP3382440B2 - Control method of negative pressure pump - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the operation of a negative pressure pump connected to a negative pressure tank in order to maintain the internal pressure of the negative pressure tank within a predetermined range. The present invention relates to a method for controlling a negative pressure pump to be controlled. A vehicle running on a gasoline engine uses a negative pressure generated in an intake passage to operate a negative pressure booster of a brake device, but an electric vehicle using an electric motor as a driving source for driving. Cannot use the intake negative pressure, the negative pressure generated by a negative pressure pump driven by a pump motor is stored in a negative pressure tank to operate a negative pressure booster. However, since the energy loss increases if the negative pressure pump is operated at all times, the absolute pressure in the negative pressure tank rises and reaches the upper limit. The negative pressure pump is stopped when the absolute pressure in the tank decreases to a lower limit as a result. [0003] In order to maintain a constant relative pressure between the atmospheric pressure, which determines the capacity of the negative pressure booster, and the absolute pressure in the tank, as shown in FIG. Upper limit (pump operating pressure) and lower limit (pump stop pressure) of the absolute pressure in the tank that is lower than the atmospheric pressure by a certain relative pressure
Let it be assumed that the negative pressure pump is activated when the absolute pressure in the tank reaches the upper limit, and the negative pressure pump is stopped when the absolute pressure in the tank reaches the lower limit. At this time, there is no problem if the atmospheric pressure is sufficiently high, but if the altitude increases and the atmospheric pressure decreases, the lower limit of the absolute pressure in the tank falls below the maximum capacity that the negative pressure pump can generate. The pump may be in a continuous operation state. In order to solve such a problem, FIG.
As shown in (b), if the upper limit value (pump operating pressure) and the lower limit value (pump stop pressure) of the absolute pressure in the tank are constant regardless of the atmospheric pressure, the negative pressure pump will be in a continuous operation state. However, when the altitude increases and the atmospheric pressure decreases, the relative pressure between the atmospheric pressure and the absolute pressure in the tank decreases, and the capacity of the negative pressure booster decreases. Therefore, as shown in FIG. 8 (c), the upper limit (pump operating pressure) and the lower limit (pump stop pressure) of the absolute pressure in the tank are reduced by using a large capacity negative pressure pump. Although the above problem can be solved by setting to, when the altitude is low and the atmospheric pressure is high, the relative pressure between the atmospheric pressure and the absolute pressure in the tank becomes excessive in the shaded area in the figure, and the energy loss increases. Problems occur. The present invention has been made in view of the above circumstances, and provides a method of controlling a negative pressure pump which can always optimally control the operation / stop of the negative pressure pump regardless of a change in atmospheric pressure. The purpose is to: [0007] In order to achieve the above object, the invention according to claim 1 is connected to the negative pressure tank so as to maintain the internal pressure of the negative pressure tank within a predetermined range. The relative pressure between the atmospheric pressure and the absolute pressure in the tank is less than a first relative pressure predetermined value, and the absolute pressure in the tank is equal to the first absolute pressure. of the time it is absolutely圧所value or actuates the suction pump, a negative pressure pump when the relative pressure is the first relative圧所value greater than the second relative圧所value or more
The pump is stopped, and the negative pressure pump is also stopped when the absolute pressure in the tank is less than a second predetermined absolute pressure value lower than the first predetermined absolute pressure value. Embodiments of the present invention will be described below based on reference examples shown in the accompanying drawings and embodiments of the present invention. 1 to 3 show a reference example, FIG. 1 is an overall configuration diagram of an electric vehicle, FIG. 2 is a flowchart for explaining the operation, and FIG. 3 is a graph showing threshold values for operating and stopping a negative pressure pump. It is. As shown in FIG. 1, this electric vehicle is a four-wheeled vehicle having a pair of rear wheels Wr, Wr as driven wheels and a pair of front wheels Wf, Wf as driving wheels.
Wf is a traveling motor 2 using the battery 1 as an energy source.
Via a transmission 3. A power drive unit 4 is interposed between the battery 1 and the traveling motor 2 to control the driving of the traveling motor 2 by the battery 1 and to charge the battery 1 with electric power generated by the motor 2 in association with regenerative braking. Control. The power drive unit 4 is connected to a motor control ECU 5, which is connected to a brake ECU 6. The master cylinder 8 operated by the brake pedal 7 is connected to the brake cylinders 11f, 11f of the front wheels Wf, Wf via a differential pressure valve 9 and a modulator 10.
f and brake cylinders 11r, 11 of the rear wheels Wr, Wr.
r. The modulator 10 has front wheels Wf, Wf
And when the rear wheels Wr, Wr tend to lock, the brake cylinders 11f, 11f; 11r, 11r
Decrease the brake hydraulic pressure transmitted to the motor. A negative pressure tank 13 is connected to a negative pressure booster 12 provided on the master cylinder 8, and a negative pressure pump 15 driven by a pump motor 14 has a check valve 16 connected to the negative pressure tank 13. Connected via. The negative pressure tank 13 is provided with an absolute pressure sensor 18 for detecting the absolute pressure in the tank, and a hydraulic pressure sensor 19 is provided in an oil passage between the master cylinder 8 and the differential pressure valve 9. The signals from the absolute pressure sensor 18 and the oil pressure sensor 19 and the signal from the atmospheric pressure sensor 20 provided at a suitable position on the vehicle body are input to the brake ECU 6, which controls the operation of the differential pressure valve 9 and the pump motor 14. I do. A motor control ECU 5 connected to the brake ECU 6 controls the operation of the power drive unit 4 of the traveling motor 2. Next, the operation of the reference example having the above-described configuration will be described. When the driver operates the master cylinder 8 by depressing the brake pedal 7 to brake the vehicle, the differential pressure valve 9 is kept closed until the oil pressure detected by the oil pressure sensor 19 reaches a predetermined value. . As a result, the brake oil pressure generated by the master cylinder 8 is not transmitted to the brake cylinders 11f, 11f of the front wheels Wf, Wf,
Only the brake cylinders 11r, 11r of the rear wheels Wr, Wr to which the brake hydraulic pressure is transmitted generate a hydraulic braking force. At this time, the motor ECU 5 controls the traveling motor 2 via the power drive unit 4 so that the regenerative braking force corresponding to the decrease in the hydraulic braking force of the front wheels Wf and Wf due to the closing of the differential pressure valve 9 is used for traveling. The battery 1 is charged with electric power generated by the motor 2 and generated by the traveling motor 2.
Thus, while reducing the decrease in the hydraulic braking force with a regenerative braking force to ensure a constant total braking force, the regenerative braking is prioritized over the hydraulic braking to improve the energy recovery efficiency.
The travelable distance per charge of the battery 1 can be extended. When the oil pressure detected by the oil pressure sensor 19 exceeds the predetermined value, the differential pressure valve 9 is gradually opened in accordance with an increase in the depression force of the brake pedal 7, and the brake cylinders 11f of the front wheels Wf, Wf are opened. 11f starts to generate the hydraulic braking force. That is, the differential pressure valve 9 transmits the differential pressure obtained by subtracting the brake oil pressure corresponding to the magnitude of the regenerative braking force from the brake oil pressure generated by the master cylinder 8 to the brake cylinders 11f, 11f of the front wheels Wf, Wf. in this way,
By regulating the upper limit of the regenerative braking force, the traveling motor 2 may generate regenerative braking force exceeding the limit and may be damaged.
The battery 1 is prevented from being damaged by overcharging. Now, the operation of the negative pressure booster 12 causes the absolute pressure in the negative pressure tank 13 to gradually increase, so that the absolute pressure in the negative pressure tank 13 falls between the predetermined upper limit and lower limit. The brake ECU 6 controls the operation / stop of the pump motor 14 (that is, the operation / stop of the negative pressure pump 15) based on the output of the absolute pressure sensor 18 and the output of the atmospheric pressure sensor 20. Hereinafter, the control contents will be described with reference to the flowchart of FIG. 2 and the graph of FIG. [0018] First, compared with the predetermined value Pa ₀ set in advance and the atmospheric pressure Pa detected by the atmospheric pressure sensor 20 in step S1, the atmospheric pressure Pa in order altitude is relatively low predetermined value P
proceeds to step S2 when it is a ₀ or more, when the atmospheric pressure Pa in order altitude is relatively high is less than the predetermined value Pa ₀ moves to step S6. If Pa ≧ Pa ₀ in step S 1, the atmospheric pressure Pa detected by the atmospheric pressure sensor 20 and the tank absolute pressure P detected by the absolute pressure sensor 18 are determined in step S 2.
b, and a relative pressure ΔPb (ΔPb = Pa−Pb) is compared with a threshold value ΔPb _ON which is a preset constant value.
Is less than the threshold value ΔPb _ON , that is, if the absolute pressure Pb in the tank is increased by the operation of the negative pressure booster 12, the negative pressure pump 15 is operated in step S3 to
Reduce the pressure. As a result, the relative pressure Delta] Pb becomes equal to or higher than the threshold Delta] Pb _ON tank absolute pressure Pb decreases, the step S
If the answer to 2 is NO, the process moves to step S4. In step S4, the relative pressure ΔPb and a predetermined threshold value ΔPb _OFF (ΔPb _OFF >
ΔPb _ON ) and the relative pressure ΔPb becomes the threshold ΔPb _OFF
If this is the case, that is, if the absolute pressure Pb in the tank has decreased due to the operation of the negative pressure pump 15, the negative pressure pump 15 is stopped in step S5 to stop reducing the pressure in the negative pressure tank 13. In this way, when the atmospheric pressure Pa is equal to or higher than the predetermined value Pa ₀ because the altitude is relatively low, the relative pressure ΔPb
Is compared with the two threshold values ΔPb _ON and ΔPb _OFF to control the operation / stop of the negative pressure pump 15. If Pa <Pa ₀ in step S1, in step S6 the absolute pressure Pb in the tank is compared with a preset threshold value Pb _ON, and if the absolute pressure Pb in the tank is equal to or greater than the threshold Pb _ON , If there is, that is, the negative pressure booster 12
If the absolute pressure Pb in the tank has risen by the operation of, the negative pressure pump 15 is operated in step S7 to
3 is depressurized. As a result, when less than the threshold Pb _ON tank absolute pressure Pb decreases, the answer at step S6 is NO
And the process moves to step S8. In step S8, the tank absolute pressure P
b and a predetermined threshold Pb _OFF (Pb _OFF
<Pb _ON ), the absolute pressure Pb in the tank becomes the threshold Pb
If it is less than _OFF, that is, if the absolute pressure Pb in the tank is reduced by the operation of the negative pressure pump 15, the negative pressure pump 15 is stopped in step S9 to stop reducing the pressure in the negative pressure tank 13. In this way, when the atmospheric pressure Pa is less than the predetermined value Pa ₀ because the altitude is relatively low, the absolute pressure Pb in the tank is compared with the two thresholds Pb _ON and Pb _OFF to thereby reduce the negative pressure of the pump. 15 is controlled to start and stop. In this embodiment, the control shown in FIG. 8A is performed when the atmospheric pressure Pa is equal to or higher than the predetermined value Pa ₀ , and when the atmospheric pressure Pa is lower than the predetermined value Pa ₀ , the control shown in FIG. (C)
By performing the control described above, it is possible to avoid energy loss in the area shown by hatching in FIG. 8 (c) and to avoid continuous operation of the negative pressure pump 15 shown in FIG. 8 (a). In this embodiment, the relative pressure ΔPb between the atmospheric pressure Pa and the absolute pressure Pb in the tank is determined from the outputs of the atmospheric pressure sensor 20 and the absolute pressure sensor 18. The layout of the sensor is easier than in the case of obtaining from the output. The reason is that the absolute pressure sensor 18 must be provided in the negative pressure tank 13 (or a pipe connected from the negative pressure tank 13 to the negative pressure booster 12), but the atmospheric pressure sensor 20 is not particularly limited in installation location.
On the other hand, when a relative pressure sensor is used instead of the atmospheric pressure sensor 20, both the absolute pressure sensor 18 and the relative pressure sensor are connected to the negative pressure tank 13 (or a pipe connecting the negative pressure tank 13 to the negative pressure booster 12). )
Layout flexibility is reduced. Next, the actual <br/>施例of the present invention will be described with reference to FIGS. In this embodiment, the same control as the control of the operation / stop of the negative pressure pump 15 in the reference example can be performed based on another control program. First, step S in the flowchart of FIG.
Comparing the relative pressure Delta] Pb and threshold Delta] Pb _ON at 11, relative pressure Delta] Pb is shifted to the step S12 if it is less than the threshold value Delta] Pb _ON. In step S12, the tank absolute pressure Pb and the threshold P
comparing the b _ON, if the absolute pressure Pb at the threshold Pb _ON or tank, ie if "AND condition" is satisfied in step S11 and step S12, activating the negative pressure pump 15 in step S3. Step S11 and step S1
The area where the “AND condition” of No. 2 is satisfied is indicated by the oblique line (A) in FIG.
The negative pressure pump 15 can be operated in this area (A) in the same manner as in the reference example. Subsequently, in step S14, the relative pressure ΔPb is compared with the threshold value ΔPb _OFF, and the relative pressure ΔPb is set to the threshold value ΔPb.
_OFF , or in step S15, the absolute pressure Pb in the tank is compared with the threshold Pb _OFF to determine the absolute pressure P in the tank.
If b is less than the threshold Pb _OFF, i.e. if "OR condition" is satisfied at step S14 and step S15, causes stops negative pressure pump 15 in step S16. Step S1
The area where the "OR condition" is satisfied in step 4 and step S15 is the area indicated by oblique lines (B) in FIG. 5. In this area (B), the negative pressure pump 15 can be stopped in the same manner as in the reference example. According to this embodiment, the same operation and effect as those of the above-described reference example can be obtained by a control program that is simpler than that of the above-described reference example. Next, a second reference example will be described with reference to FIG. The relative pressure of the second reference example negative actuation and stop of the pressure pump 15, the atmospheric pressure Pa and the absolute pressure sensor 18 tank absolute pressure Pb detected by detected by the atmospheric pressure sensor 20 delta
It is controlled by Pb, and the control signal is the atmospheric pressure Pa
Is not used directly. Therefore, instead of providing the atmospheric pressure sensor 20 and the absolute pressure sensor 18, it is also possible to provide one relative pressure sensor and detect the relative pressure ΔPb. FIG. 6A shows a case where the atmospheric pressure is high, and a threshold ΔP having a constant relative pressure with respect to the atmospheric pressure Pa.
b _ON-OFF is set, and when the relative pressure ΔPb between the atmospheric pressure Pa and the absolute pressure Pb in the tank is reduced by the operation of the negative pressure booster 12 and becomes smaller than the threshold value ΔPb _ON-OFF , the negative pressure tank 1 is set.
The negative pressure pump 15 operates to reduce the pressure of the pump 3. The negative pressure pump 15 operates to increase the relative pressure ΔPb, and the relative pressure ΔPb
b is a negative pressure pump 15 is stopped when the predetermined time T ₁ is elapsed from greater than or equal to a threshold value ΔPb _ON-OFF. As described above, when the atmospheric pressure is high, the relative pressure ΔPb is rapidly increased by the operation of the negative pressure pump 15, so that the negative pressure pump 15
Can be started and stopped without any trouble. On the other hand, when the atmospheric pressure is low as shown in FIG. 6 (b), even if the relative pressure ΔPb becomes smaller than the threshold value ΔPb _ON-OFF and the negative pressure pump 15 is operated, the relative pressure ΔPb is quickly increased. Therefore, the pressure ΔPb cannot be equal to or greater than the threshold value ΔPb _ON-OFF , and as a result, the negative pressure pump 15 may fall into a continuous operation state. Therefore, in the second reference example, the negative pressure pump 1
When 5 has elapsed after operated for a predetermined time T ₂ has to stop the suction pump 15 forcibly, the threshold ΔPb
Change _ON-OFF to decrease. Thereafter, based on the changed threshold value ΔPb _ON-OFF , the negative pressure pump 15 can be started and stopped without any trouble in the same manner as in FIG. 6A. In the second embodiment, one threshold value ΔP
Two thresholds ΔPb _ON and ΔPb _OFF are set instead of b _ON-OFF , the threshold ΔPb _ON is used as a condition for operating the negative pressure pump 15, and the threshold ΔPb _OFF and the predetermined time T ₁ are stopped for the negative pressure pump 15. It may be used as a condition for causing it to occur. Next, a third reference example will be described with reference to FIG. FIG. 7A shows a case where the atmospheric pressure is high. Two thresholds ΔPb _ON and ΔPb _OFF having a constant relative pressure with respect to the atmospheric pressure Pa are set, and the relative pressure ΔPb is set. When the pressure decreases and becomes less than the threshold value ΔPb _ON , the negative pressure pump 15 is operated to reduce the pressure in the negative pressure tank 13, and when the relative pressure ΔPb becomes equal to or more than the threshold value ΔPb _OFF by the operation of the negative pressure pump 15, the negative pressure pump 15 is stopped. Let it.
As described above, when the atmospheric pressure is high, the relative pressure ΔPb is rapidly increased by the operation of the negative pressure pump 15, so that the negative pressure pump 15 can be operated and stopped without any trouble. On the other hand, when the atmospheric pressure is low as shown in FIG. 7B, even if the relative pressure ΔPb becomes smaller than the threshold value ΔPb _ON and the negative pressure pump 15 is operated, the relative pressure ΔPb increases quickly. As a result, the threshold value ΔPb _OFF cannot be exceeded, and as a result, the negative pressure pump 15 may fall into a continuous operation state. Therefore, in the third reference example, the negative pressure pump 1
When 5 has elapsed after operated for a predetermined time T ₂ has to stop the suction pump 15 forcibly, the two threshold Δ
Change both Pb _ON and ΔPb _OFF to the decreasing side. Thus,
Thereafter, based on the changed thresholds ΔPb _ON and ΔPb _OFF , the negative pressure pump 15 can be started and stopped without any trouble in the same manner as in FIG. 7A. [0038] To control based only on the relative pressure ΔPb the operation and stop of the third reference example is also the negative pressure pump 15, provided one of the relative pressure sensor instead of providing the atmospheric pressure sensor 20 and absolute pressure sensor 18 be able to. [0039] The second 及 beauty third reference example as well, to minimize wasteful operation of the vacuum pump 15 regardless of variations in the atmospheric pressure Pa, avoiding a reduction in the generation and durability of energy loss can do. Moreover, since only the relative pressure ΔPb is required for the control, the control program can be simplified as compared with the case where the relative pressure ΔPb and the absolute pressure Pb in the tank are used for the control signal. Although the embodiments of the present invention have been described in detail, various design changes can be made in the present invention without departing from the gist thereof. For example, in the embodiment, the negative pressure pump 15 for depressurizing the negative pressure tank 13 of the electric vehicle has been described. Can be. As described above, according to the first aspect of the invention, the relative pressure between the atmospheric pressure and the absolute pressure in the tank is less than the first relative pressure predetermined value, and the absolute pressure activates the negative pressure pump when it is first absolute圧所value or more, negative when the relative pressure is the first relative圧所value greater than the second relative圧所value or more Pressure pump
The negative pressure pump is also stopped when the tank absolute pressure is lower than the second absolute pressure predetermined value that is lower than the first absolute pressure predetermined value. It is possible to prevent the energy loss from being increased by necessity, and to secure as large a relative pressure as possible while preventing the negative pressure pump from operating continuously when the atmospheric pressure is low. be able to.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph Figure 4 showing an entire configuration diagram [2] threshold for actuating and stopping the flow chart Figure 3 vacuum pump for explaining an operation of the reference example of the electric vehicle real illustrating the operation of a time chart 7 third reference example for explaining the operation of the graph 6 second reference example for explaining the flow chart Figure 5 effects the actual施例explaining the operation of施例FIG. 8 is a diagram for explaining control of a conventional negative pressure pump. [Description of References] 13 Negative pressure tank 15 Negative pressure pump Pa Atmospheric pressure Pb Absolute pressure Pb in tank _ON threshold (first absolute pressure predetermined value) ) Pb _OFF threshold (second absolute圧所value) Delta] Pb relative pressure Delta] Pb _ON threshold (first relative圧所value) Delta] Pb _OFF threshold (second relative圧所value)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References Japanese Utility Model Showa 58-64877 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) F04B 49/06 B60T 17/02 F04B 37 / 16

Claims (1)

(57) Claims 1. The operation of a negative pressure pump (15) connected to the negative pressure tank (13) to maintain the internal pressure of the negative pressure tank (13) within a predetermined range. In the method of controlling the negative pressure pump for controlling the stop, the relative pressure (ΔPb) between the atmospheric pressure (Pa) and the absolute pressure in the tank (Pb) is less than a first relative pressure predetermined value (ΔPb _ON ), and When the internal absolute pressure (Pb) is equal to or more than a first absolute pressure predetermined value (Pb _ON ), the negative pressure pump (15) is operated, and the relative pressure (ΔPb) is changed to the first relative pressure predetermined value (Pb _ON ). When the second relative pressure is larger than ΔPb _ON ) or more than the second relative pressure predetermined value (ΔPb _OFF ) , the negative pressure pump (15) is _{turned off.}
The negative pressure pump (15) is also stopped when the tank absolute pressure (Pb) is less than a second absolute pressure predetermined value (Pb _OFF ) lower than the first absolute pressure predetermined value (Pb _ON ). A method of controlling a negative pressure pump, characterized by stopping the operation.