JP2019137241A - 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. When temperature of hydraulic fluid is a preset temperature or less, discharging of hydraulic fluid by the motor pump is prohibited and idling engine speed is increased. In the state of a low temperature, the assistance device accepts sufficient hydraulic fluid to protect the motor pump and the electric motor driving the motor pump, and promote temperature rise of hydraulic fluid in the system so as to be capable of getting out of the low temperature state as soon as possible.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 the two-pump hydraulic steering assist system as described in the above-mentioned patent document, the situation where the temperature of the hydraulic fluid (generally hydraulic fluid) is lower than the set temperature (hereinafter referred to as “low temperature situation”). In some cases, the viscosity of the hydraulic fluid increases and the discharge performance of the motor pump deteriorates. It is also predicted that the electric motor that drives the motor pump will be overloaded. The present invention has been made in view of such circumstances, and at a low temperature, the force for assisting the steering force is stabilized, and the state in which the temperature of the hydraulic fluid is rapidly reduced is removed. This is the issue.

  In order to solve the above-described problems, a steering assist system according to the present invention is the above-described two-pump hydraulic steering assist system, and discharges hydraulic fluid by a motor pump in a situation where the hydraulic fluid temperature is lower than a set temperature. And is configured to increase the engine idling speed.

  According to the present invention, the operation of the motor pump is prohibited under low temperature conditions, and the idling speed of the engine is increased, so that the assisting device receives a sufficient amount of hydraulic fluid, and the motor pump and the electric motor that drives the motor pump. In this way, the temperature of the hydraulic fluid in the steering assist system can be increased, and the low temperature protection state can be quickly removed.

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 the steering assist control program performed in the said steering assist system. It is a flowchart which shows the steering assist control program used as a modification.

  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.

  In the assist system, a temperature sensor 110 that detects the temperature of the hydraulic fluid is provided at a location near the reservoir 84 of the first pumping path 86. The 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 to coordinate control processing. Have been to run.

[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. When the rotational speed R of the engine 12 increases to some extent, the necessary assisting device receiving flow rate Qa decreases because the steering operation force is increased to some extent when the vehicle travels at a certain high speed, and the steering feeling is reduced. It is consideration for improvement. 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 torque of the engine pump 78 in order to improve fuel consumption. Therefore, as shown by a broken line in the graph of FIG. Furthermore, the discharge flow rate of the hydraulic fluid from the engine pump 78 is made smaller than the discharge flow rate of the hydraulic fluid 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 low-temperature situations and coping with them In general, oil is used as the hydraulic fluid, and if the motor pump 82 is the only source of high-pressure fluid, use low-viscosity hydraulic fluid. By doing so, the discharge performance of the motor pump 82 can be sufficiently ensured under low temperature conditions (for example, under the freezing point condition). However, in the assist system, since the engine pump 78 is mounted side by side, the low-viscosity hydraulic fluid has a higher risk of the engine pump 78 being insufficiently lubricated at a high temperature. It is desirable. With a highly viscous hydraulic fluid, the discharge performance of the motor pump 82 is deteriorated, and the electric motor 80 that drives the motor pump 82 is likely to be overloaded.

  Therefore, in the present assist system, the operation of the motor pump 82 is prohibited under low temperature conditions. Specifically, the MP-ECU 106 when the temperature T detected by the temperature sensor 110 provided near the reservoir 84 of the first draw-up path 86 is equal to or higher than the first set temperature T1. However, the operation of the motor pump 82 is prohibited. 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 rises and becomes equal to or higher than the second set temperature T2. . Incidentally, in order to prevent the hunting phenomenon in the control, the second set temperature T2 is set higher 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 engine pump discharge flow rate control mechanism 102 stops the restriction state of the engine pump discharge flow rate Qe under the control of the engine pump discharge flow rate control mechanism 102 by the EP-ECU 104. The restriction on the engine pump discharge flow rate Qe is released, and 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 low temperature condition, a sufficient assisting force can be obtained in the engine mode or the hybrid mode. Further, by driving the engine pump 78 at a high idling rotational speed Ri ′, the temperature rise of the working fluid circulating in the assist system is promoted, and the above-mentioned protection state at a low temperature can be removed in a short time. It is.

  In the state where the operation of the motor pump 82 is prohibited, the MP-ECU 106 instructs the HB-ECU 30 to prohibit the traveling of the vehicle in the EV mode in order to prohibit the traveling of the vehicle in the EV mode. A command is sent.

iii) Control Flow of Steering Assist System The control of this assist system centering on the control relating to the prohibition of operation of the motor pump 82 under the low temperature condition described above is performed by the MP-ECU 106 functioning as a general controller of the assist system shown in FIG. The steering assist control program shown in the flowchart is executed by executing the program at a short time pitch (for example, several milliseconds to several tens of milliseconds). 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 flag value of the motor pump prohibition flag F is determined. The motor pump prohibition flag F is a flag whose flag value is “1” when the 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 S2, the threshold temperature T0 for determining whether the operation of the motor pump 82 is prohibited or allowed is set to the first set temperature T1 described above. When the value is “1”, in S3, the threshold temperature T0 is set to the second set temperature T2 described above.

  Next, in S4, it is determined whether or not the temperature T detected by the temperature sensor 110 is equal to or lower than the threshold temperature T0. When it is determined that the temperature T is equal to or lower than the threshold temperature T0, in S5, the operation of the motor pump 82 is prohibited, the flag value of the motor pump prohibition flag F is set to “1”, and in S6, HB− A command for operating the engine 12 at a high idling rotational speed Ri ′ and a command for prohibiting traveling of the vehicle in the EV mode are transmitted to the ECU 30, and the engine is transmitted to the EP-ECU 104. A command to prohibit the control of the pump discharge flow rate control mechanism 102 is transmitted. Incidentally, as described above, when the 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 S4 that the temperature T detected by the temperature sensor 110 is higher than the threshold temperature T0, the operation of the motor pump 82 is permitted in S7, and the flag value of the motor pump prohibition flag F is set to “0”. In step S8, a command for operating the engine 12 at the normal idling speed Ri and a command for allowing the vehicle to travel in the EV mode are transmitted to the HB-ECU 30. The EP-ECU 104 is instructed to allow control of the engine pump discharge flow rate control mechanism 102. In S9, it is determined whether or not the vehicle is traveling in the EV mode. As described above, in the EV mode, the target motor pump discharge flow rate Qm is the required assist device receiving flow rate Qa in S10. If not in the EV mode, the target motor pump discharge flow rate Qm is determined to be the insufficient flow rate Qi in S11. In S13, the operation of the motor pump 82 is controlled based on the determined motor pump discharge flow rate Qm.

[D] Modification
i) Modified example for coping with low temperature condition In the assist system of the above embodiment, whether or not the temperature is low based on the temperature T of the hydraulic fluid detected by the temperature sensor 110 provided in the first pumping path 86. Was judged. For convenience, it may be determined at another temperature T whether or not “the temperature of the hydraulic fluid is below a set temperature”. For example, as shown in FIG. 1, a temperature sensor 114 built in the MP-ECU 106, a temperature sensor 114 ′ for detecting the outside air temperature, a temperature sensor 114 ″ for detecting the temperature of the cooling water of the engine 12, and the like. It is also possible to substitute the detected temperature T.

  In the assist system of the above-described embodiment, when the temperature T is equal to or lower than the threshold temperature T0 that is the first set temperature T1, the operation of the motor pump 82 is prohibited and the threshold temperature T0 that is set to the second set temperature T2. When the temperature is higher, the operation of the motor pump 82 is allowed. However, for example, when the detected temperature T is equal to or lower than the threshold temperature T0, the operation of the motor pump 82 is prohibited. When the engine pump 78 is operated for the set time t0 or more, it may be determined that the temperature of the hydraulic fluid has risen and the low temperature state has been removed, and the operation of the motor pump 82 may be permitted.

  A steering assist control program in this modification is shown in a flowchart in FIG. The process according to this program will be briefly described with respect to a different part from the program of the above embodiment. In S22, when the temperature T detected by the temperature sensor 114 (114 ′, 114 ″) is equal to or lower than the threshold temperature T0. In S23, the operation of the motor pump 82 is prohibited, and the processing in S24 is performed, and then in S25, the time counter t for measuring the passage of time is counted up by the count-up value Δt, and in S26 When it is determined that the set time t0 has elapsed, the time counter t is reset in S27, and the operation of the motor pump 82 is permitted in S28, and if the set time t0 has not elapsed, the process proceeds to S21. According to the determination, the prohibition of the operation of the motor pump 82 continues until the set time t0 has elapsed. It is.

ii) Other Modifications 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, but they are not provided. It is also possible to construct an assist 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 a low temperature condition, 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 also be applied to a four-wheel drive vehicle and a rear 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. In addition to a hybrid vehicle, for example, a function that has only an engine as a drive source and that stops the engine in a running state and uses the inertia of the vehicle to continue running (for example, a low-speed idling stop function, free The present invention can also be applied to a vehicle having a run function or the like.

  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 T0: Threshold temperature t0: Set time

Claims (2)

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;
An electric motor;
A motor pump that is driven by the electric motor and pumps up and discharges the hydraulic fluid stored in the reservoir;
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 steering assist system configured to prohibit discharge of hydraulic fluid by the motor pump and increase an idle speed of the engine under a situation where the temperature of the hydraulic fluid is equal to or lower than a set temperature. The vehicle is a hybrid vehicle that can be driven by both the engine and a drive motor, and can be driven only by the drive motor;
The steering assist system
2. The steering assist system according to claim 1, configured to prohibit driving the vehicle only by the drive motor under the circumstances.

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