JP2019137240A - Steering assist system - Google Patents

Abstract

To provide a steering assist system excellent in practicability.SOLUTION: A steering assist system includes: an engine pump 78 driven by rotation of an engine 12; and a motor pump 82 driven by rotation of an electric motor 80, in which an assistance device 92, 76 assisting a turning force is constituted to be capable of accepting hydraulic fluid from the engine pump and the motor pump. The steering assist system prohibits, when a detection temperature of a temperature sensor 110 is a preset temperature or higher, discharging of hydraulic fluid from the motor pump. When resuming the discharging, trial of discharging hydraulic fluid by the motor pump is performed at a trial flow rate smaller than normal discharge flow rate during a set time. Only when change gradient of the detection temperature is less than a preset gradient, the normal discharge of hydraulic fluid by the motor pump is allowed. It can effectively protect the electric motor and a motor pump controller whose upper limit temperatures allowing operation are low.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a steering assist system that is mounted on a vehicle and assists steering of wheels.

  Conventionally, as a steering assist system, there is a system that assists the steering force by the pressure of hydraulic fluid (for example, hydraulic fluid), that is, a hydraulic steering assist system. This hydraulic steering assist system is highly reliable and can generate a relatively large assisting force. The hydraulic steering assist system is generally configured to drive a pump as a high-pressure liquid source by the rotation of an engine. On the other hand, for example, when considering a vehicle driven by a hybrid vehicle, it is desired to assist the steering force even when the engine is not operating. An assist device for assisting the steering force of the hydraulic fluid from the engine pump and the motor pump is provided with both an engine pump driven by the rotation of the motor and a motor pump driven by the rotation of the electric motor. Steering assist systems configured to accept (hereinafter, sometimes referred to as “two-pump hydraulic steering assist systems”) are also being considered.

JP 2014-19290 A

  In a two-pump hydraulic steering assist system as described in the above patent document, generally, when the allowable temperature on the motor pump side is low and the allowable upper limit temperature is exceeded, the motor pump is operated. Must be stopped and protected. This invention is made | formed in view of such a situation, and makes it a subject to shorten the stop time required for protection of a motor pump.

  In order to solve the above problems, a steering assist system of the present invention is the above-described two-pump hydraulic steering assist system, and is a temperature sensor built in a motor pump controller unitized with a motor pump and an electric motor. When the temperature of the hydraulic fluid detected by the above is higher than the set temperature, it is prohibited to discharge the hydraulic fluid by the motor pump, and when trying to allow the hydraulic fluid to be discharged by the prohibited motor pump, Normal operation by the motor pump is performed on the condition that the trial discharge of the hydraulic fluid by the motor pump at the trial flow rate set smaller than the discharge flow rate is executed for a set time, and the temperature change gradient detected by the temperature sensor is smaller than the set gradient. It is configured to allow normal discharge of the hydraulic fluid.

  According to the steering assist system of the present invention, the temperature of the hydraulic fluid circulating in the system can be grasped by the temperature sensor inside the controller, and the stop time for protection can be shortened.

1 is a diagram schematically illustrating a vehicle on which a steering assist system according to an embodiment of the present invention is mounted, and an overall configuration of the steering assist system. FIG. It is a figure which shows the state by which hydraulic fluid is discharged to an assistance apparatus only from an engine pump in the said steering assist system. It is a figure which shows the state by which hydraulic fluid is discharged to an assistance apparatus only from a motor pump in the said steering assist system. It is a graph for demonstrating the action | operation of the said steering assist system in normal time. It is a graph for demonstrating the action | operation of the said steering assist system in the state in which the action | operation of a motor pump is prohibited. It is a flowchart which shows 1 cycle of the steering assist control program performed in the said steering assist system. It is a flowchart which shows the subroutine about the process regarding the resumption of the action | operation of a motor pump performed in the steering assist control program shown in FIG.

  Hereinafter, as a mode for carrying out the present invention, a steering assist system of an embodiment will be described in detail with reference to the drawings. It should be noted that the present invention can be implemented in various forms in which various modifications and improvements are made based on the knowledge of those skilled in the art, in addition to the following examples.

[A] Configuration of a vehicle equipped with a steering assist system A vehicle equipped with a steering assist system of the embodiment (hereinafter sometimes abbreviated as “assist system”) is shown in FIG. The four wheels 10 (two rear wheels are omitted in the figure) are vehicles in which the two front wheels 10 are drive wheels. This vehicle is a hybrid vehicle that can drive the front wheels 10 by both the engine 12 and a drive motor 14 that is an electric motor, and the front wheels 10 are steered wheels.

  The vehicle drive system of the vehicle will be described. The vehicle drive system includes an engine 12, a drive motor 14, a generator 16 that mainly functions as a generator, and a power split mechanism that connects the engine 12 and the generator 16. 18. The power split mechanism 18 has a function of splitting the rotation of the engine 12 into the rotation of the generator 16 and the rotation of the output shaft. The drive motor 14 is connected to the output shaft via a reduction mechanism 20 that functions as a speed reducer. The rotation of the output shaft is transmitted through the differential mechanism 22 and the drive shafts 24L and 24R, and the left and right front wheels 10 are rotationally driven. The generator 16 is connected to the battery 28 via the inverter 26G, and the electric energy obtained by the power generation of the generator 16 is stored in the battery 28. The drive motor 14 is also connected to the battery 28 via an inverter 26M, and the operation of the drive motor 14 and the operation of the generator 16 are controlled by controlling the inverter 26M and the inverter 26G. Control of the vehicle drive system is performed by a hybrid drive electronic control unit (hereinafter sometimes abbreviated as “HB-ECU”) 30, and the HB-ECU 30 uses only the engine 12 as a travel mode depending on the situation. An “engine mode” for driving the vehicle, an “EV mode” for driving the vehicle only by the drive motor 14, and a “hybrid mode” for driving the vehicle by both the engine 12 and the drive motor 14 are selectively realized. .

  The vehicle steering system of the vehicle will be described. The vehicle steering system includes a pair of steering knuckles (hereinafter sometimes abbreviated as “knuckles”) 50 that respectively hold the left and right front wheels 10 and extend in the left-right direction. A steering rod 56 having both ends connected to a knuckle arm 52 of each knuckle 50 via a tie rod 54, a steering wheel 58 that is a steering operation member, and a steering shaft that is held by a steering column and rotates by a rotation operation of the steering wheel 58 60 and a gear box 62 incorporating a motion conversion mechanism (rack and pinion mechanism) that converts the rotational motion of the steering shaft 60 into a lateral motion of the steered rod 56. The left and right front wheels 10 are steered It is configured to.

[B] Hardware Configuration of Steering Assist System The assist system according to the embodiment assists, that is, assists the steering force, which is the force by which the driver steers the front wheels 10 by the hydraulic pressure of the hydraulic fluid (hydraulic oil). The system includes a hydraulic actuator 76 having a piston 70 fixed to the steered rod 56 and a housing 74 that is internally partitioned by the piston 70 into two liquid chambers 72L and 72R. Further, two pumps each serving as a high-pressure liquid source, specifically, an engine pump 78 driven by the engine 12 and a motor pump 82 driven by the electric motor 80 are provided. The engine pump 78 pumps up the hydraulic fluid from a reservoir 84 that stores hydraulic fluid via a first pumping path 86, and supplies a supply flow control mechanism 92 (described later) via a first discharge path 88 and a common discharge path 90. ), Discharge the pumped hydraulic fluid. The motor pump 82 pumps hydraulic fluid from the reservoir 84 via the second pumping path 94, and supplies the pumped hydraulic fluid via the second discharge path 96 and the common discharge path 90 to supply flow control. Discharge to mechanism 92.

  The supply flow control mechanism 92 has, for example, a general structure as shown in FIG. 2 of Japanese Patent Laid-Open No. 6-8840, and specifically, for example, a torsion bar corresponding to the turning force of the driver. On the basis of the torsion amount and the steering direction, the flow rate of the working fluid supplied to the actuator 76 and the function of controlling which of the two fluid chambers 72L and 72R is supplied with the working fluid are provided. The supply flow control mechanism 92 receives the hydraulic fluid discharged from at least one of the engine pump 78 and the motor pump 82, and when no steering force is generated, the supply flow control mechanism 92 is supplied to the reservoir 84 via the return path 98. The received hydraulic fluid is returned. That is, the hydraulic fluid is circulated. On the other hand, when the steering force is generated, the supply flow control mechanism 92 applies at least a part of the received hydraulic fluid to one of the two liquid chambers 72L and 72R of the actuator 76 according to the steering. The hydraulic fluid is supplied at the same flow rate, the hydraulic fluid having the same flow rate is received from the other, and the received hydraulic fluid is also returned to the reservoir 84. The actuator 76 acts on the piston 70 by a force corresponding to the pressure of the hydraulic fluid supplied from the supply flow control mechanism 92 to one of the two liquid chambers 72L and 72R. It is configured to assist the rudder force. That is, in the present assist system, an assist device that includes the supply flow control mechanism 92 and the actuator 76 and assists the turning force in response to the request by returning the received working fluid to the reservoir 84. Is configured.

  The engine pump 78 discharges hydraulic fluid at a flow rate corresponding to the rotational speed of the engine 12 (strictly, it means “rotational speed”). Therefore, this assist system is provided with a flow rate limiting mechanism 100 that limits the flow rate of the hydraulic fluid discharged from the engine pump 78 on the discharge side of the engine pump 78. This flow restricting mechanism 100 has a structure as shown in, for example, Japanese Patent No. 3218788, Japanese Patent Laid-Open No. 8-301132, Japanese Patent Laid-Open No. 6-8840, or the like, that is, a general structure including a valve. Specifically, it has a function of limiting the flow rate of the hydraulic fluid that passes through the engine 12 and is sent to the supply flow control mechanism 92 to the set flow rate when the rotational speed of the engine 12 increases to some extent. ing. Further, in the present assist system, an engine for controlling the flow rate of the hydraulic fluid that is provided in series with the flow rate limiting mechanism 100 on the discharge side from the flow rate limiting mechanism 100 and that is sent from the flow rate limiting mechanism 100 to the supply flow control mechanism 92. A pump discharge flow rate control mechanism 102 is provided. The engine pump discharge flow rate control mechanism 102 is, for example, an electromagnetic valve mechanism having a general structure as shown in FIG. 2 of Japanese Patent Application Laid-Open No. 2014-19290, and the flow rate of the hydraulic fluid according to the current supplied to the solenoid. It has a function to allow passage. The engine pump discharge flow rate control mechanism 102 is controlled by an engine pump discharge flow rate electronic control unit (hereinafter also referred to as “EP-ECU”) 104. It can be considered that the engine pump discharge flow rate control mechanism 102 and the EP-ECU 104 constitute an engine pump discharge flow rate control device, and the flow rate of the hydraulic fluid discharged from the engine pump 78 to the supply flow control mechanism 92 is convenient. In other words, the engine pump discharge flow rate control device has a function of electronically controlling the engine pump discharge flow rate Qe.

  Control of the motor pump 82, specifically, operation of the electric motor 80 that drives the motor pump 82, is performed by a motor pump electronic control unit (hereinafter also referred to as “MP-ECU”) 106 as a motor pump controller. Is called. That is, if the flow rate of the hydraulic fluid discharged from the motor pump 82 to the supply flow control mechanism 92 is called a motor pump discharge flow rate Qm, the MP-ECU 106 has a function of electronically controlling the motor pump discharge flow rate Qm. ing. The motor pump 82, the electric motor 80, and the MP-ECU 106 are unitized and mounted on the vehicle as the motor pump unit 108. By being unitized in this way, the mountability of the motor pump 82, the electric motor 80, and the MP-ECU 106 is good. The MP-ECU 106 includes a temperature sensor 110.

  The EP-ECU 104, the MP-ECU 106, and the HB-ECU 30 described above are connected to a CAN (“car area network” or “contorolable area network”) 112 and communicate with each other so as to execute coordinated control processing. Has been.

[C] Operation of steering assist system
i) Operation in Normal Time FIG. 1 shows a state in which the assist system discharges hydraulic fluid from both the engine pump 78 and the motor pump 82 to the supply flow control mechanism 92. Hereinafter, the operation mode in such a state is referred to as a “both pump mode”. 2 and 3, in which only the assist system is represented, show a state in which hydraulic fluid is discharged from only the engine pump 78 to the supply flow control mechanism 92, respectively. The state of being discharged is shown. Hereinafter, the operation modes in the state shown in FIGS. 2 and 3 are referred to as “engine pump mode” and “motor pump mode”, respectively.

  Explaining the operation in the engine pump mode that has been conventionally performed, the discharge flow rate of the hydraulic fluid from the engine pump 78 increases the rotational speed R of the engine 12 as shown by the broken line in the graph of FIG. As a result, it increases almost linearly. Here, in order to simplify the description, a case where the engine pump discharge flow rate control mechanism 102 is not functioned, that is, a case where the engine pump discharge flow rate Qe is limited only by the flow rate limiting mechanism 100 will be considered. For example, the flow rate restriction mechanism 100 may be adjusted so that the engine pump discharge flow rate Qe is restricted as indicated by the alternate long and short dash line in the graph. In the assist system, a flow rate of the hydraulic fluid that is required to be received by the supply flow control mechanism 92, that is, a necessary assist device receiving flow rate Qa is set. The graph shows a case where the flow rate restriction mechanism 100 is adjusted so that the engine pump discharge flow rate Qe becomes the necessary assist device receiving flow rate Qa. That is, the alternate long and short dash line in the graph can be considered as a line indicating the required assisting device receiving flow rate Qa. Note that when the rotational speed R of the engine 12 increases to some extent, the necessary assisting device receiving flow rate Qa is reduced in order to make the steering operation somewhat heavy when the vehicle travels at a certain high speed. According to the engine pump 78 and the flow rate restriction mechanism 100 configured as described above, the hydraulic fluid at the engine pump discharge flow rate Qe as shown by the solid line is discharged to the supply flow control mechanism 92. Incidentally, since the engine 12 is rotated at the set idling speed Ri or higher, the solid line indicating the engine pump discharge flow rate Qe does not exist in the graph below the idling speed Ri.

  In the present assist system, a relatively small engine pump 78 is employed for the purpose of reducing the load of the engine 12 and the heat generation of the engine pump 78. Therefore, as shown by the broken line in the graph of FIG. The hydraulic fluid discharge flow rate from 78 is smaller than the hydraulic fluid discharge flow rate from the engine pump 78 in the graph of FIG. Accordingly, in the region ΔR where the rotational speed R of the engine 12 is relatively small (hereinafter, sometimes referred to as “low rotation region ΔR”), the shortage flow Qi indicated by hatching, that is, the necessary assist device receiving flow rate for the engine pump discharge flow rate Qe. There will be a flow rate that Qa cannot cover. In this assist system, the insufficient flow rate Qi is covered by the motor pump discharge flow rate Qm that is the flow rate of the hydraulic fluid discharged from the motor pump 82 to the supply flow control mechanism 92. Specifically, when the vehicle is traveling in the engine mode or the hybrid mode, in the region ΔR where the rotational speed R of the engine 12 is relatively small, the motor pump 82 is driven by the MP-ECU 106 to set the motor pump discharge flow rate Qm. It is operated while being controlled so as to have an insufficient flow rate Qi. That is, the assist system is operated in the dual pump mode.

  Note that in the present assist system, the engine pump discharge flow rate control mechanism 102 is actually controlled by the EP-ECU 104 to further limit the engine pump discharge flow rate Qe. Specifically, as indicated by the solid line in the graph of FIG. 4C, the engine pump discharge flow rate Qe is kept small. Therefore, not only the above-mentioned low rotation region ΔR but also the entire region of the rotational speed R at which the engine 12 operates has an insufficient flow rate Qi. Covered by the pump discharge flow rate Qm.

  Incidentally, when the vehicle traveling mode is set to the EV mode, the engine 12 is not operated, so the motor pump mode is set, and the necessary assisting device receiving flow rate Qa is covered by the motor pump discharge flow rate Qm. Thus, the motor pump 82 is controlled by the MP-ECU 106.

ii) Problems in a high temperature situation and coping with them The engine pump 78 is always operated when the vehicle is running in the engine mode or the hybrid mode, and the hydraulic fluid is constantly circulated. The operation of the engine pump 78 contributes to increasing the temperature of the hydraulic fluid. More specifically, since the hydraulic fluid discharged from the engine pump 78 passes through the flow restriction mechanism 100, the passage of the hydraulic pump 78 increases the temperature of the hydraulic fluid. It becomes a big factor to raise. As the temperature of the hydraulic fluid increases, the assist system is placed under a high temperature condition. In normal driving and steering, the temperature of the hydraulic fluid does not increase significantly, but the vehicle is operated severely, for example, while maintaining the rotation of the engine 12 at a high speed, the steering wheel 58 is kept at the steering end. There is a high possibility that the temperature of the hydraulic fluid becomes high when the vehicle operation is continued. Incidentally, even if the hydraulic fluid becomes hot, the temperature of the hydraulic fluid gradually decreases by returning to normal traveling and steering.

  On the other hand, the electric motor 80 for driving the motor pump 82 has a lower upper limit of the temperature at which the operation is allowed compared to the engine pump 78, and the MP-ECU 106 is also an electronic board on which a computer, a driver, etc. are mounted. Similarly, the upper limit of the temperature at which operation is permitted is low. In the present assist system, since the electric motor 80, the motor pump 82, and the MP-ECU 106 are mounted on the vehicle as a unitized motor pump unit 108, the electric motor 80, the MP-ECU 106 due to heat transmitted from the hydraulic fluid. The impact on is great.

  Therefore, in the present assist system, the operation of the motor pump 82 is prohibited when the temperature becomes high. Specifically, when the temperature T detected by the temperature sensor built in the MP-ECU 106 is equal to or higher than the first set temperature T1, the temperature of the hydraulic fluid is equal to or higher than the set temperature. As a result, the MP-ECU 106 prohibits the operation of the motor pump 82. In the state where the operation of the motor pump 82 is prohibited, the operation of the prohibited motor pump 82 is allowed when the temperature of the working fluid decreases and becomes equal to or lower than the second set temperature T2. . Incidentally, in order to prevent a hunting phenomenon in the control, the second set temperature T2 is set lower than the first set temperature T1 so as to provide an appropriate margin ΔT.

  In the state where the operation of the motor pump 82 is prohibited, as shown in the graphs of FIGS. 4B and 4C, the required assist device receiving flow rate Qa cannot be covered only by the engine pump discharge flow rate Qe. That is, the insufficient flow rate Qi cannot be compensated. Therefore, in the present assist system, as shown in FIG. 5, the control of the engine pump discharge flow rate control mechanism 102 by the EP-ECU 104 is stopped, that is, the restriction of the engine pump discharge flow rate Qe by the engine pump discharge flow rate control mechanism 102 is released. At the same time, the idling speed Ri of the engine 12 is changed to a high idling speed Ri ′. Specifically, a command for operating the engine 12 at the idling rotational speed Ri ′ is transmitted from the MP-ECU 106 to the HB-ECU 30, and the HB-ECU 30 operates so as to operate at the idling rotational speed Ri ′. To control. When the operation of the prohibited motor pump 82 is permitted, the control of the engine pump discharge flow rate control mechanism 102 by the EP-ECU 104 is resumed, and the MP-ECU 106 operates the engine 12 at the idling speed Ri. Is transmitted to the HB-ECU 30, and the HB-ECU 30 controls the engine 12 to operate at the idling rotational speed Ri.

  The high idling speed Ri ′ is set to such an extent that the low speed region ΔR does not exist in the graph of FIG. 4B, and the engine 12 operates by the transition from the idling speed Ri to the idling speed Ri ′. In the entire region of the rotational speed R, the necessary assist device receiving flow rate Qa is covered only by the engine pump discharge flow rate Qe. That is, even if the operation of the motor pump 82 is prohibited in a high temperature situation, a sufficient assisting force can be obtained in the engine mode or the hybrid mode.

  In the state where the operation of the motor pump 82 is prohibited, the MP-ECU 106 changes from the MP-ECU 106 to the HB-ECU 30 in the EV mode in order to stop the vehicle traveling in the EV mode and switch to the engine mode or the hybrid mode traveling. A command to prohibit the running of the vehicle is transmitted.

iii) Trial discharge for resuming the operation of the motor pump When the operation of the motor pump 82 is resumed, that is, when the operation of the motor pump 82 that has been prohibited is allowed, in this assist system, the trial discharge by the motor pump 82 is performed. The operation of the motor pump 82 is allowed after confirming that the temperature of the hydraulic fluid will actually decrease according to the result of the trial discharge.

  When the operation of the motor pump 82 is prohibited and the assist system is operated in the engine pump mode, as shown in FIG. 2, the working fluid present in the second pumping path 94 and the second discharge path 96 is circulated. Not allowed. Therefore, the temperature sensor 110 built in the MP-ECU 106 cannot accurately measure the temperature of the working fluid circulating through the first pumping path 86 and the first discharge path 88. For example, when the above-mentioned severe vehicle operation is performed while the operation of the motor pump 82 is prohibited, the high-temperature hydraulic fluid circulates. In that case, even if the temperature detected by the temperature sensor 110 is equal to or lower than the second set temperature T2, when the motor pump 82 is operated, the motor pump 82 pumps up the high-temperature working fluid. May flow into the motor pump 82 and may not sufficiently protect the electric motor 80 and the MP-ECU 106. In view of this, in the present assist system, trial discharge by the pump motor 82 is performed when the operation of the motor pump 82 is resumed.

  In the trial discharge, the motor pump 82 is operated to such an extent that the hydraulic fluid having the trial flow rate Qm ′ set smaller than the motor pump discharge flow rate Qm allowed in the motor pump mode and the both pump modes is discharged. In short, the motor pump 82 is operated at a low speed so that only a considerably small trial flow rate Qm ′ is discharged compared to the normal motor pump discharge flow rate Qm (hereinafter referred to as “low operation”). ) Specifically, the trial flow rate Qm ′ is such that, for example, the amount of hydraulic fluid at which the hydraulic fluid in the second pumping path 94 passes through the motor pump 82 is discharged at the trial discharge time t1U that is the set time. Small flow rate.

  Then, on condition that the detected temperature gradient dT, which is the change gradient of the temperature T detected by the temperature sensor 110 when the motor pump 82 is operated at the trial discharge time t1U at the trial flow rate Qm ′, is smaller than the set gradient dT0. The normal discharge of the hydraulic fluid of the motor pump 82 is allowed. That is, the operation of the motor pump 82 in the motor pump mode and the both pump modes is allowed assuming that the temperature of the hydraulic fluid circulating in the assist system is sufficiently low. In the present assist system, since the restart of the operation of the motor pump 82 is allowed by the determination based on such a condition, a sensor for detecting the temperature of the working fluid circulating through the first pumping path 86 and the first discharge path 88. Therefore, the electric motor 80 and the MP-ECU 106 can be sufficiently protected.

  When the detected temperature gradient dT is equal to or greater than the set gradient dT0, the trial discharge of the motor pump 82 at the trial flow rate Qm ′ is performed again after the set interval time t2U has elapsed, and again, It is determined whether or not the detected temperature gradient dT is smaller than the set gradient dT0. The interval time t2U is set to be longer as the temperature T is higher, based on the temperature T detected by the temperature sensor 110 at the time of determination.

iv) Control flow of the steering assist system The control of the present assist system, which is centered on the control relating to the prohibition of operation of the motor pump 82 under the high temperature condition described above and accompanied by the process relating to the resumption of the operation of the motor pump 82, The MP-ECU 106 functioning as the overall controller is executed by executing the steering assist control program shown in the flowcharts of FIGS. 6 and 7 at a short time pitch (for example, several milliseconds to several tens of milliseconds). Incidentally, a series of processing relating to resumption of the operation of the motor pump 82 is made into a subroutine as shown in FIG. Hereinafter, the flow of processing by the program will be briefly described.

  In the processing according to the program, first, in step 1 (hereinafter abbreviated as “S1”, the same applies to other steps), the temperature T detected by the temperature sensor 110 is specified. Next, in S2, the value of the motor pump low operation flag C is determined. The motor pump low operation flag C is a flag indicating whether or not the trial discharge is performed. The flag value is “1” when the trial discharge is performed, and the flag value is “1” when the trial discharge is not performed. It is a flag set to “0”. When trial ejection is being performed, the processing is skipped to the subroutine shown in FIG. If it is determined in S2 that trial ejection has not been performed, the value of the interval flag I is determined in S3. The interval flag I is a flag indicating whether or not the motor pump 82 is stopped until the trial discharge is performed again (hereinafter sometimes referred to as “interval”). The processing is skipped to the subroutine.

  If the motor pump 82 is not performing trial discharge and is not in the interval, the flag value of the motor pump prohibition flag F is determined in S4. This motor pump prohibition flag F is a flag whose flag value is “1” when the normal operation of the motor pump 82 is prohibited, and whose flag value is “0” when it is permitted. When the flag value is “0”, in S5, the threshold temperature T0 for determining whether the operation of the motor pump 82 is prohibited or permitted is set to the first set temperature T1 described above. When the value is “1”, the threshold temperature T0 is set to the second set temperature T2 described above in S6.

  Next, in S7, it is determined whether or not the temperature T detected by the temperature sensor 110 is equal to or higher than the threshold temperature T0. When it is determined that the temperature T is equal to or higher than the threshold temperature T0, the normal operation of the motor pump 82 is prohibited in S8, the flag value of the motor pump prohibition flag F is set to “1”, and in S9, A command for operating the engine 12 at a high idling rotational speed Ri ′ and a command for prohibiting the vehicle from traveling in the EV mode are transmitted to the HB-ECU 30. A command to prohibit the control of the engine pump discharge flow rate control mechanism 102 is transmitted. That is, as described above, when the normal operation of the motor pump 82 is prohibited, the engine pump discharge flow rate control mechanism 102 does not control the engine pump discharge flow rate Qe.

  When it is determined in S7 that the temperature T detected by the temperature sensor 110 is lower than the threshold temperature T0, in S10, normal operation of the motor pump 82 is permitted, and the flag value of the motor pump prohibition flag F is set to “ Set to 0 ”. Next, in S11, it is determined whether or not the flag value of the motor pump prohibition flag F has changed from “1” to “0” in the current execution of the program. If it is determined that the value has changed from “1” to “0”, that is, whether or not the precondition for restarting the normal operation of the motor pump 82 is satisfied in the current program when the temperature T decreases. Is determined and satisfied, the process proceeds to the subroutine of FIG. If the flag value continues at “0”, in S12, the HB-ECU 30 is instructed to operate the engine 12 at the normal idling speed Ri, and the vehicle travels in the EV mode. Is sent to the EP-ECU 104, and a command to allow control of the engine pump discharge flow rate control mechanism 102 is sent to the EP-ECU 104.

  Then, in the subsequent S13, it is determined whether or not the vehicle is traveling in the EV mode. As described above, if the vehicle is in the EV mode, the target motor pump discharge flow rate Qm is required in S14. When the assist device receiving flow rate Qa is not in the EV mode, the target motor pump discharge flow rate Qm is determined as the insufficient flow rate Qi in S15. After the target motor pump discharge flow rate Qm is determined, in S16, the operation of the motor pump 82 is controlled based on the determined motor pump discharge flow rate Qm.

  If it is determined in S11 that the flag value of the motor pump prohibition flag F has changed from “1” to “0” in the current execution of the program, the process proceeds to S17 in the flowchart of FIG. In S17, the conditions for permitting the normal operation of the motor pump 82 have not been satisfied yet, so the normal operation of the motor pump 82 is prohibited and the flag value of the motor pump prohibition flag F is “1”. Is done. In S18, the flag value of the motor pump low operation flag C is set to “1”. In S19, the motor pump 82 is operated in the low state, that is, the trial discharge of the motor pump 82 at the trial flow rate Qm ′. Is called.

  In S20, the first time counter t1 for measuring the trial discharge time is counted up by the count-up time Δt1. In subsequent S21, it is determined whether or not the value of the first time counter t1 has reached the trial discharge time t1U. If it has reached, the motor pump low operation flag C and the first time counter t1 are set in S22. Reset. If not reached, one execution of the program ends, but the trial discharge of the motor pump 82 is continued by the determination of S2 in the next execution of the program.

  After the trial discharge of the trial discharge time t1U by the motor pump 82, in S23, the change in the temperature T detected by the temperature sensor 110, that is, the detected temperature gradient dT is specified, and the detected temperature gradient dT is determined from the set gradient dT0. If it is smaller, the normal operation of the motor pump 82 is permitted in S24, and the flag value of the motor pump prohibition flag F is set to “0”.

  If it is determined in S23 that the detected temperature gradient dT is equal to or greater than the set gradient dT0, the flag value of the interval flag I is set to “1” to wait for the elapse of the interval time t2U until the trial discharge is performed again. In step S26, the motor pump 82 is stopped. In subsequent S27, an interval time t2U is set based on the detected temperature T, and in S28, the second time counter t2 for determining the elapse of the set interval time t2U counts for the count-up time Δt2. Will be up.

  In the next S29, it is determined whether or not the value of the second time counter t2 has reached the set interval time t2U. If so, the interval flag I and the second time counter t2 are reset in S30. Is done. If not reached, one execution of the program ends, but the motor pump 82 is stopped until the interval time t2U elapses by the determination of S3 in the next execution of the program.

[D] Modification In the assist system of the above embodiment, the engine pump discharge flow rate control mechanism 102 and the EP-ECU 104 are provided to electronically control the engine pump discharge flow rate Qe. It is also possible to build a system. Such an assist system has the advantage of being inexpensive. According to such an assist system, when the operation of the motor pump 82 is allowed, the operation as shown in the graph of FIG. 4B is performed, and the operation of the motor pump 82 is prohibited. The operation as shown in the graph of FIG. 5 is performed. Therefore, this assist system also enjoys the merit of prohibiting the operation of the motor pump 82 under high temperature conditions, like the assist system of the above embodiment.

  Further, the operation as shown in FIG. 4C can be performed only by the engine pump discharge flow rate control mechanism 102 without providing the flow rate restriction mechanism 100.

  The assist system of the present invention can be applied to a rear wheel drive vehicle and a four wheel drive vehicle. Further, the present invention can be applied to a system other than a steering system having a rack and pinion type motion conversion mechanism, for example, a steering system having a recirculating ball type motion conversion mechanism. Further, in addition to the hybrid vehicle, for example, the present invention is also applicable to a vehicle having only an engine as a drive source and having an idling stop function when traveling at a low speed and when stopping.

  12: Engine 76: Actuator 78: Engine pump 80: Electric motor 82: Motor pump 84: Reservoir 100: Flow rate limiting mechanism 102: Engine pump discharge flow rate control mechanism [Engine pump discharge flow rate control device] 106: Motor pump electronic control unit ( MP-ECU) [motor pump controller] 108: motor pump unit 110: temperature sensor Qe: engine pump discharge flow rate Qm: motor pump discharge flow rate Qa: required assist device receiving flow rate Ri, Ri ': idling speed T1: first setting Temperature T2: Second set temperature dT: Detected temperature gradient dT0: Set gradient t1U: Trial discharge time t2U: Interval time

Claims (1)

A reservoir for storing hydraulic fluid;
An engine pump that is driven by an engine that drives the vehicle, pumps up the hydraulic fluid stored in the reservoir, and discharges the hydraulic fluid at a flow rate according to the rotational speed of the engine;
(a) an electric motor; (b) a motor pump that is driven by the electric motor and pumps up and discharges the hydraulic fluid stored in the reservoir; and (c) the motor by controlling the operation of the electric motor. A motor pump unit integrated with a motor pump controller for controlling a motor pump discharge flow rate that is a flow rate of hydraulic fluid discharged from the pump;
The hydraulic fluid discharged from the motor pump and the hydraulic fluid discharged from the engine pump can be received, and the turning force according to the request is returned by the received hydraulic fluid while returning the received hydraulic fluid to the reservoir. A steering assist system mounted on the vehicle with an assisting device for assisting
A temperature sensor is provided in the motor pump controller,
The motor pump controller is
When the temperature detected by the temperature sensor is equal to or higher than a set temperature, the discharge of hydraulic fluid by the motor pump is prohibited,
When allowing the discharge of the hydraulic fluid by the prohibited motor pump, the trial discharge of the hydraulic fluid by the motor pump at a trial flow rate set smaller than a normal discharge flow rate is executed for a set time, A steering assist system configured to allow normal discharge of hydraulic fluid by the motor pump on condition that a temperature change gradient detected by a temperature sensor is smaller than a set gradient.

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