JP2006082568A - Power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power steering device capable of solving the problem that the temperature of working fluid does not rise in a power steering device of the configuration to generate the power assist force by driving an electric motor as necessary, and the force required for the steering is increased to cause a heavy operation. <P>SOLUTION: In the power steering device, a reversible pump 9 is connected to pressure chambers 4a, 4b on both sides of a piston 3 of a power cylinder 2 to give the assist force to steered wheels via a first flow passage 8a and a second flow passage 8b to selectively feed the hydraulic pressure. A communication passage 14 to communicate the first flow passage 8a with the second flow passage 8b is provided, a tank 12 is connected to the communication passage 14 via a solenoid valve 15, and a fluid temperature sensor 17 to detect the temperature of working fluid is provided to constitute a circulation means 19. When the temperature of the fluid temperature sensor 17 is not higher than a predetermined value, the solenoid valve 15 is opened to circulate working fluid via the tank 12. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power steering device that generates a power assist force by rotating an electric motor only when necessary. When the temperature of the hydraulic oil is low, the hydraulic oil is circulated to raise the temperature to reduce the viscous shear force, thereby steering The operating force required for the operation is reduced.

  A motor vehicle is provided with a power steering device that operates a power cylinder to obtain a power assist force (steering assist force) by controlling a flow path switching valve based on an operation of a steering wheel.

A conventional power steering apparatus is configured as described in Patent Document 1. The lower part of the steering shaft is connected to the piston of the power cylinder through a rack and a pinion, and in order to output assist force through the power cylinder, the pump is operated by an electric motor to supply and discharge hydraulic oil to the power cylinder. I am letting. In order to supply and discharge hydraulic oil, the pump and the left and right hydraulic chambers of the power cylinder are connected via first and second hydraulic pipes. On the other hand, a torque sensor is provided on the steering shaft, and a power assist force is generated by rotating the electric motor only when necessary based on signals from the torque sensor and the vehicle speed sensor.
JP-A-6-16145

  However, since the electric motor is rotated only when necessary to generate a power assist force, the temperature of the hydraulic oil cannot be increased by absorbing the heat generated by the pump when the pump is not operating. When the ambient temperature is low, the discharge performance of the motor and the pump is lowered with the increase of the viscous shear force of the hydraulic oil, so that the force required for steering becomes large and the operation becomes heavy.

  Therefore, an object of the present invention is to provide a power steering device that solves the above-described problems by circulating the hydraulic oil and raising the temperature when the temperature of the hydraulic oil is low.

  The invention according to claim 1 is a power cylinder that applies assist force to a steered wheel, and a reversible pump that selectively supplies hydraulic pressure to pressure chambers on both sides of a piston of the power cylinder via first and second flow paths. A motor for rotating the reversible pump forward and backward, assist force detecting means for detecting the assist force of the power cylinder, and applying a predetermined hydraulic pressure to the power cylinder based on the assist force detected by the assist force detecting means. Motor control means for outputting a drive signal to the motor to generate the communication path, and circulating the hydraulic oil from one of the first flow path and the second flow path toward the other; A circulating means having an on-off valve for turning on and off the flow of the communication passage and a temperature measuring means for detecting or estimating the environmental temperature or the hydraulic oil temperature is provided and measured by the temperature measuring means Temperature rotates the opening and the motor the opening and closing valve when it is less than a predetermined value, characterized in that so as to circulate the hydraulic oil by the reversible pump.

  According to this invention, when the temperature measured by the temperature measuring means is equal to or lower than the predetermined value, the on-off valve is opened and the motor rotates to circulate the hydraulic oil by the reversible pump. When this happens, the operating oil can be forced to circulate to raise the temperature of the operating oil. For this reason, when the ambient temperature is low, etc., the discharge performance of the motor and pump decreases with the increase of the viscous shear force of the hydraulic oil, and the conventional problem that the force required for steering increases and the operation becomes heavy Is resolved.

  According to a second aspect of the present invention, in the power steering device according to the first aspect of the present invention, there is a case where the stop state determining means for determining the stop state of the vehicle and the stop state determining means determine that the vehicle is in the stop state. And the travel prevention means which blocks | prevents driving | running | working of a vehicle when the said circulation means is act | operating is provided.

  According to this invention, in the circulation mode in which the hydraulic oil is circulated by the circulation means, the same steering assist as that in the normal state cannot be performed because the on-off valve is open. For this reason, in the circulation mode, the start of the vehicle is blocked by the travel blocking means, thereby preventing a decrease in steering response immediately after the start of travel and a shortage of assist force during travel.

  According to a third aspect of the present invention, in the power steering device according to the second aspect, the stop state determining means is at least one of a hand brake position, a foot brake position, an AT select lever position, an accelerator pedal opening degree, and a tachometer. The stop state of the vehicle is determined based on the signal.

  According to the present invention, in the circulation mode, the stop state of the vehicle can be properly determined from the handbrake position and the like.

Hereinafter, embodiments of a power steering apparatus according to the present invention will be described.
(A) Embodiment 1
First, the first embodiment is shown in FIG. The power steering device 1 is configured as follows. The power cylinder 2 is provided long along the left-right direction of the vehicle. The power cylinder 2 is provided with a piston 3, and a first pressure chamber 4a and a second pressure chamber 4b are formed on both sides of the piston 3. A long rack 5 is integrally coupled to the piston 3 along the left-right direction of the vehicle. The rack 5 meshes with a pinion 8 (not shown) provided at the lower end of a steering shaft 7 having a steering wheel 6.

  The first pressure chamber 4a and the second pressure chamber 4b are connected to a reversible pump 9 via a first flow path 8a and a second flow path 8b, respectively. The reversible pump 9 selectively supplies hydraulic pressure to one of the first pressure chamber 4a and the second pressure chamber 4b and discharges it from the other, so that the piston 3 moves in the left-right direction. Steering wheels are connected to both ends of the rack 5 via tie rods (not shown), and the power cylinder 2 assists the operating force of the steering wheels. The reversible pump 9 is connected to a motor 10 for rotating the reversible pump 9 forward and backward. The first flow path 8a and the second flow path 8b are connected to the tank 12 via suction check valves 11a and 11b. The suction check valves 11 a and 11 b are opened when the pressure in the reversible pump 9 is lower than the pressure in the tank 12. The first flow path 8a and the second flow path 8b are connected via a communication path 14 having check valves 13a and 13b, and a central portion of the communication path 14 is connected via an electromagnetic valve 15 as an on-off valve. Connected to the tank 12.

  A torque sensor 16 for detecting a load torque between the steering shaft 7 and the steering wheel is provided on the steering shaft 7 in order to detect an assist force applied to the steering wheel (not shown) from the power cylinder 2. Further, an oil temperature sensor 17 for detecting the hydraulic oil temperature in the tank 12 is provided as a temperature measuring means for detecting or estimating the environmental temperature or the hydraulic oil temperature.

  An electronic control unit (hereinafter referred to as ECU) 18 is provided. The ECU 18 is connected to the torque sensor 16, the oil temperature sensor 17, a vehicle speed meter, and a tachometer, and further connected to the motor 10 and the electromagnetic valve 15. The ECU 18 detects the torque of the torque sensor 16 and detects the motor 10. In addition to controlling the hydraulic pressure sent to the power cylinder 2 by rotating, the circulating means 19 is configured to circulate the hydraulic oil to raise the temperature of the hydraulic oil.

  The circulation means 19 opens the electromagnetic valve 15 when the measured temperature of the tank 12 is not more than a predetermined value and the load torque between the steering shaft 7 and the steering wheel is not more than a predetermined value. The motor 10 is rotated and the hydraulic oil is guided to the tank 12 by the reversible pump 9 and circulated, thereby raising the temperature of the hydraulic oil. Even when the temperature of the tank 12 is lower than a predetermined value and the steering torque is higher than the predetermined value, a part of the hydraulic oil discharged from the reversible pump 9 flows to the power cylinder 2 while the rest is electromagnetic. The valve 15 is opened by a predetermined amount and led to the tank 12 to be circulated. The hydraulic oil is circulated while assisting to raise the temperature.

  In addition to this, the ECU 18 is connected with a stop state determination means 20 and a travel prevention means 21. The stop state determination means 20 determines whether or not the vehicle is stopped. The travel prevention means 21 determines that the stop state determination means 20 determines the stop state of the vehicle, and the circulation means 19 The vehicle is prevented from traveling when the circulating mode is in operation. The stop state determination means 20 determines the stop state of the vehicle based on at least one of the hand brake position, foot brake position, AT select lever position, accelerator pedal opening, and tachometer. The travel prevention means 21 prevents the vehicle from traveling by at least one of hand brake, foot brake, AT select lever position change prevention, and fuel injection amount restriction.

  Next, functions of the control unit and the like provided in the ECU 18 will be described. The ECU 18 includes a steering force assist control unit for performing steering force assist control when traveling on a general road, and a hydraulic oil temperature determination unit that compares the temperature T of the hydraulic oil detected by the oil temperature sensor 17 with a predetermined temperature. The steering mode determination unit that determines the steering state by comparing the torque S detected by the torque sensor 16 with a predetermined torque, and the circulation mode according to the length of time during which the determination result of the steering state determination unit continues during traveling A circulation mode selection unit for determining whether or not to make a transition, and a circulation mode selection for judging whether a transition is made to a B or C circulation mode, which will be described later, by determining whether the vehicle is stopped or traveling based on the vehicle speed And an electromagnetic valve control unit that opens and closes the electromagnetic valve 15 based on the determination result of the circulation mode transition determination unit, and a motor control unit (motor control means) that controls the motor. The motor control unit is provided with a motor rotation number control unit for controlling the rotation number of the motor 10 to be equal to or less than a predetermined rotation number.

  The operation of the power steering apparatus 1 will be described with reference to FIG. When the ignition switch is turned on in step S1, the oil temperature signal of the hydraulic oil temperature T from the oil temperature sensor 17, the torque sensor signal of the torque S from the torque sensor 16, and the vehicle speed V from the existing speedometer are obtained in step S2. It is read into the ECU 18. In step S3, when the hydraulic oil temperature determination unit of the ECU 18 determines that the hydraulic oil temperature T is lower than the predetermined temperature TA, the circulation mode transition determination unit determines to increase the hydraulic oil temperature T. In step S4, the mode is switched to “circulation mode A” before starting. Then, the stop state determination unit 21 determines the stop state of the vehicle by recognizing the handbrake position and the like, and the travel blocking unit 21 such as the handbrake prevents the start of the automobile.

  On the other hand, when it is determined in step S3 that the hydraulic oil temperature T is higher than the predetermined temperature TA, the process proceeds downward in FIG. 2, and when the electromagnetic valve 15 is closed as in step S5, the following is normal. It becomes operation of driving mode. In the operation in the traveling mode, in step S6, the steering state determination unit receives the signal of the torque S from the torque sensor 16 to determine the steering state, and when the torque S is smaller than the predetermined torque St, “the steering operation is performed”. It is determined that the state is not present, and the process proceeds to step S7. Then, the circulation mode transition determination unit determines that the duration h in which the condition of S ≦ St is satisfied is longer than the predetermined duration h0, and “the state in which no steering wheel operation is performed continues for some time”. If so, the process proceeds to step S8. On the other hand, if it is determined that the time is shorter than the predetermined duration h0, the routine proceeds to steering force assist control in step S13 described later.

  In step S8, the circulation mode selection unit selects the circulation mode according to the vehicle speed. That is, if the vehicle speed is zero, it is determined that the vehicle is in a “stop state such as waiting for a signal” and the process proceeds to “circulation mode B” in step S9. On the other hand, if the vehicle speed is not zero, it is determined that the vehicle is in a “straight-running state such as traveling on an expressway with little steering operation”, and the process proceeds to “circulation mode C” in step S10. If the steering assist force is unnecessary, such as when the vehicle is stopped waiting for a signal or when driving straight ahead on an expressway, etc., operation assistance is achieved by operating the circulation means to enter the circulation mode. The oil temperature of the hydraulic oil can be raised without affecting the oil temperature, and the oil temperature can be maintained at an appropriate value.

  In the case of the general road traveling in which the torque S from the torque sensor 16 is larger than the predetermined torque St in step S6, the process proceeds to step S11 in the lower part of FIG. When it is determined that T is lower than the predetermined temperature TA, the process proceeds to step S12 in order to increase the temperature of the hydraulic oil. And it becomes "circulation mode D" in the driving | running | working of the general road which performs steering force assist control, circulating hydraulic oil. On the other hand, when the hydraulic oil temperature T is higher than the predetermined temperature TA, the process proceeds to step S13 by the determination of the hydraulic oil temperature determination unit. In step S13, the steering force assist control unit performs assist control with the electromagnetic valve 15 being closed in step 5, that is, without circulating the hydraulic oil.

  Next, “circulation mode A” will be described in detail. In step S3 of FIG. 2, when it is determined that the hydraulic oil temperature T is lower than the predetermined temperature TA, the process proceeds to “circulation mode A” before starting as described above. Then, the hydraulic oil is circulated until the hydraulic oil temperature T rises to a predetermined temperature TA, during which the vehicle is prevented from starting by the travel prevention means 21. In the state of the circulation mode A before the start in which the hydraulic oil is circulated by the circulation means, the electromagnetic valve 15 is opened, so that the same steering assist as that when traveling on a general road cannot be performed. For this reason, in the state of the circulation mode A, the start of the vehicle is blocked by the travel blocking means, thereby preventing a decrease in steering response immediately after the start of travel and a shortage of assist force during travel.

  As shown in FIG. 3, when the travel prevention means 21 is turned ON in step S14 and the vehicle cannot travel, the electromagnetic valve control unit stops energization and opens the electromagnetic valve 15 in step S15, and the motor control unit opens in step S16. The motor 10 is rotated. At this time, if hydraulic oil is supplied in the direction of arrow A in FIG. 1, for example, the suction check valve 11a is closed and the check valve 13a is opened. For this reason, the hydraulic oil discharged from the reversible pump 9 is supplied in the direction of arrow A through the first flow path 8a, passes through the check valve 13a, enters the communication path 14, reaches the tank 12 from the electromagnetic valve 15, Circulation is performed by returning from the tank 12 to the reversible pump 9 via the suction check valve 11b and the second flow path 8b. In the state of the circulation mode A, the travel prevention means forcibly prevents the start of the vehicle by hand brake or the like, so that a decrease in steering response immediately after the start of travel and a shortage of assist force during travel are prevented. Next, in step S17, the motor rotation speed controller calls the motor rotation speed N. If the motor rotation speed N is equal to or greater than the predetermined rotation speed (Nmax) in step S18, the rotation speed N is converted into the rotation speed (Nmax) in step S19. Limit to. In the circulation mode, the electromagnetic valve 15 is opened and the load on the motor 10 is reduced, so that the rotational speed of the motor 10 may increase excessively. If such a situation continues, the motor 10 generates heat and the reversible pump 9 However, when the motor rotation speed control unit controls the rotation speed, the motor 10 and the reversible pump 9 are protected and durability is improved. On the other hand, if the motor rotation speed N is smaller than the predetermined rotation speed (Nmax) in step S18, the process proceeds to step S20 as it is. When the hydraulic oil temperature determination unit determines that the hydraulic oil temperature T is equal to or higher than the predetermined temperature TB in step S20, the motor control unit stops the motor 10 in step S21 to end the circulation mode, and in step S22 The travel prevention means 23 is turned OFF, and the “circulation mode is A” ends. If the hydraulic oil temperature T is lower than the predetermined temperature TB in step S20, the process returns to step S14.

  Since the hydraulic oil is forcibly circulated when the temperature of the hydraulic oil becomes a predetermined value or less, the temperature of the hydraulic oil can be maintained at an appropriate value. For this reason, when the ambient temperature is low, etc., the discharge performance of the motor and the pump decreases with the increase of the viscous shear force of the hydraulic oil, and the conventional problem that the steering operation requires a large force and the operation becomes heavy. It will be resolved.

  Here, the temperature TB is set to a temperature equal to or higher than the temperature TA in FIG. 2, but is preferably higher than the temperature TA. When the value of (TB−TA) is set to be large, the degree to which “circulation mode A” is selected decreases. In addition, once the oil temperature rises, the temperature does not drop instantaneously, and the motor 10 and the pump 9 have some self-heating. Therefore, if the handle operation is increased, the time until the oil temperature is lowered becomes longer.

  Next, the “circulation mode B” will be described in detail. In step S8 in FIG. 2, if the stop state such as waiting for a signal of the vehicle speed V = 0 is small because the torque S which is the detection value of the torque sensor 16 is small, whether or not the circulation mode transition determination unit shifts to the circulation mode. And the process proceeds to “circulation mode B” in step S9.

  As shown in FIG. 4, when the hydraulic oil temperature determination unit determines that the oil temperature T is lower than the predetermined temperature TA in step S25, the electromagnetic valve control unit opens the electromagnetic valve 15 in step S26. In step S27, the motor control unit rotates the motor 10, and the hydraulic oil starts to circulate. Next, in step S28, the motor rotation speed controller reads the motor rotation speed N. If the motor rotation speed N is equal to or greater than the predetermined rotation speed (Nmax) in step S29, the motor rotation speed N is set to the predetermined rotation speed in step S30. Limited to (Nmax). On the other hand, if the motor rotational speed N is less than the predetermined rotational speed (Nmax) in step S29, the process proceeds to step S31. In step S31, if the vehicle speed V = 0, the circulation mode selection unit continues the state of the circulation mode B. On the other hand, if the vehicle speed V ≠ 0, the motor 10 is immediately stopped in step S34, and the electromagnetic valve 15 is turned on in step S35. Closed and circulation mode B ends.

  If the vehicle speed V = 0 in step S31, the steering state determination unit determines whether or not the steering state is in the steering state from the signal of the torque sensor 16 in step S32, and the torque S of the torque sensor 16 is smaller than the predetermined torque St. In this case, it is determined that the engine is not in the steering state, and the oil temperature becomes a problem. When the hydraulic oil temperature determination unit determines in step S33 that the hydraulic oil temperature T is equal to or higher than the predetermined temperature TB, the circulation mode B is terminated. Therefore, the process proceeds to step S34, and if it is determined that it is equal to or less than TB, the process returns to step S27. On the other hand, when the torque S is larger than the predetermined torque St in step S32, the process proceeds to step S34 in order to end the circulation mode B. In step S25, when it is determined that the oil temperature T is higher than the predetermined temperature TA, the oil temperature T passes without moving to the circulation mode B.

  Next, the “circulation mode C” will be described in detail. When the detected value of the torque sensor 16 is small in step S6 of FIG. 2 and the vehicle travels straight ahead as in the case of traveling on the highway in step S8, the circulation mode selection unit determines that the operation proceeds to “circulation mode C”. .

  As shown in FIG. 5, when the hydraulic oil temperature determination unit determines that the oil temperature T is lower than the predetermined temperature TA in step S38, the electromagnetic valve control unit opens the electromagnetic valve 15 in step S39. In step S40, the motor control unit rotates the motor 10, and the hydraulic oil starts to circulate. Next, in step S41, the motor rotation speed controller reads the motor rotation speed signal N. If the rotation speed N is equal to or greater than the predetermined rotation speed (Nmax) in step S42, the rotation speed N is converted to the rotation speed (Nmax) in step S43. ). On the other hand, when the rotation speed N is smaller than the predetermined rotation speed (Nmax), this restriction is not present. In step S44, the steering state determination unit determines the steering state based on the signal from the torque sensor 16. If the torque S from the torque sensor 16 is smaller than the predetermined torque St, the hydraulic oil temperature determination unit in step S45. Accordingly, when it is determined that the temperature T of the hydraulic oil is equal to or higher than the predetermined temperature TB, the motor 10 is immediately stopped in step S46 and the electromagnetic valve 15 is closed in step S47 in order to end the circulation mode C. On the other hand, if the torque S from the torque sensor 16 is greater than the predetermined torque St, the process proceeds to step S47 and the circulation mode C is terminated. In step S45, when the hydraulic oil temperature determination unit determines that the hydraulic oil temperature T is lower than the predetermined temperature TB, the process returns to step S40. If it is determined in step S38 that the oil temperature T is higher than the predetermined temperature TA, the oil temperature T passes without moving to the circulation mode C.

  Finally, “circulation mode D” will be described in detail. Even when the vehicle is traveling on a general road, if the hydraulic oil temperature determination unit determines in step S11 in FIG. 2 that the oil temperature T of the hydraulic oil is lower than a predetermined temperature TA, the vehicle travels on a general road to increase the oil temperature. Transition to “circulation mode D”.

  In step S50 of FIG. 6, the solenoid valve controller adjusts the amount of current flowing to the solenoid valve 15 and increases or decreases the valve opening X as a function of the oil temperature T. Thereby, the valve opening X is expressed as X = f (T). As shown in FIG. 7, the relationship between the oil temperature and the valve opening is such that the valve opening X decreases as the oil temperature T increases. When the opening degree of the electromagnetic valve 15 is increased during steering on a general road, the flow rate of hydraulic fluid flowing from the reversible pump 9 through the electromagnetic valve 15 to the tank 12 or the first flow path 8a and the second flow from the tank 12 is increased. Since the flow rate of the hydraulic oil returning to the reversible pump 9 through the flow path on the counter-assist side of the path 8b increases and the assist force may be reduced, an appropriate valve even if the oil temperature rise is delayed It is necessary to maintain the opening. Since the flow rate of the hydraulic oil flowing through the electromagnetic valve 15 depends on the viscosity of the hydraulic oil, the flow rate increases as the temperature increases, provided that the valve opening is the same. For this reason, it is necessary to adjust the valve opening according to the oil temperature.

  In the circulation mode D, not only the circulation of the hydraulic oil is intended, but a part of the hydraulic oil flowing to the power cylinder 2 is transferred to the solenoid valve 15 when the normal assist control is performed while traveling on a general road. It is made to pass and circulate. Therefore, in step 50, the valve opening X is expressed as X = f (T). When the hydraulic oil temperature determining unit determines in step S51 that the hydraulic oil temperature T is equal to or higher than the predetermined temperature TB, the solenoid valve 15 is closed in step S52 while the predetermined temperature TB is closed in order to end the circulation mode D. If it is determined that the following is true, the process returns to step 50. Opening the solenoid valve 15 to circulate the hydraulic oil causes energy loss because the steering assist force is not generated. However, if the temperature of the hydraulic oil is increased, the viscosity of the hydraulic oil decreases and the force required for steering decreases. Therefore, by incorporating the circulation mode D during the steering assist, the oil temperature can be maintained and the steering assist can be performed more appropriately.

As shown in FIG. 7, the oil temperatures TA and TB are set at the positions shown in the figure, and TA <TB. Moreover, the maximum value (Xmax) of the opening degree X of the electromagnetic valve 15 is set as shown in the figure, for example.
(B) Embodiment 2
Next, Embodiment 2 is shown in FIG. In this embodiment, as can be seen from comparison with FIG. 1, the check valves 13 a, 13 b are removed from the communication path 14, and the communication valve 14 is not communicated with the tank 12, and the solenoid valve 15 is provided in the middle of the communication path 14. Is interposed.

  By opening the solenoid valve 15 and operating the reversible pump 9, the hydraulic oil does not circulate to the tank 12 as in the first embodiment, and the reversible pump 9, the first flow path 8a, and the second flow path. The closed flow path formed by 8b and the communication path 14 is circulated along the flow indicated by the arrow A, for example. Since other configurations and operations are the same as those of the first embodiment, description thereof is omitted.

  In addition, although the system of Embodiment 1, 2 was shown as a system which circulates hydraulic oil from either one of the 1st flow path 8a and the 2nd flow path 8b to the other, it is limited to these systems. For example, in FIG. 8, a plurality of combinations of the communication path 14 and the electromagnetic valve 15 may be provided between the first flow path 8a and the second flow path 8b. In addition, display means for displaying that the circulation mode has been entered may be provided in the passenger compartment. As the display means, for example, a warning lamp may be turned on when the circulation mode is set. An inhalation check valve may be used as the reversible pump. In addition, since an electromagnetic valve that opens when the system is defective is used as the on-off valve, the electromagnetic valve opens when a defect occurs, and the first flow path and the second flow path communicate with each other. The hydraulic oil can freely move between the roads, the piston and rack of the power cylinder can freely reciprocate, and steering by manual operation becomes possible.

The technical ideas other than the invention described in the claims, as grasped from the embodiment, will be described below.
(1) In the power steering device according to (2), the travel prevention means is based on at least one of hand brake, foot brake, AT select lever position change prevention, and fuel injection amount restriction. A power steering device characterized in that

According to the present invention, in the circulation mode, the vehicle is forcibly blocked by handbrake or the like to prevent a decrease in steering response immediately after the start of traveling and a shortage of assist force during traveling.
(2) In the power steering apparatus according to any one of (1) to (1), the circulation unit is provided with a motor rotation speed control unit that controls the rotation speed of the motor to a predetermined rotation speed or less. Power steering device.

According to the present invention, in the circulation mode, the opening / closing valve is opened and the load on the motor is reduced, so there is a risk that the rotational speed of the motor will increase excessively. Although the pump may be damaged, the motor rotation speed control unit controls the rotation speed, so that the motor and the reversible pump are protected and durability is improved.
(3) In the power steering apparatus according to (1) to (2), the circulation unit is in a non-steering state in which an assist force by the assist force detection unit is a predetermined value or less, and a temperature by the temperature measurement unit is A power steering device characterized in that hydraulic oil is circulated when it is equal to or less than a predetermined value.

According to the present invention, when the steering assist force is unnecessary, such as when the vehicle is stopped waiting for a signal or when the vehicle is continuously traveling straight on an expressway or the like, the circulation means is operated to enter the circulation mode. By doing so, the oil temperature can be maintained at an appropriate value without affecting the steering assist.
(4) In the power steering apparatus according to any one of claims 1 to 2, the hydration means is in a steering state in which the assist force by the assist force detection means is a predetermined value or more and the temperature by the temperature measurement means is When a predetermined value or less, a part of the hydraulic oil discharged from the reversible pump is allowed to flow to the power cylinder, while the rest is opened and circulated by a predetermined amount to circulate the hydraulic oil while assisting. A power steering device characterized by that.

According to this invention, opening the on-off valve to circulate the hydraulic oil causes an energy loss because the steering assist force is not generated, but when the hydraulic oil is circulated and the temperature is raised, the viscosity of the hydraulic oil decreases. Therefore, the force required for steering is small and sufficient. For this reason, by incorporating the circulation mode during the steering assist, the oil temperature is properly maintained, and the steering assist is performed more appropriately.
(5) The power steering apparatus according to any one of claims 1 to 4, further comprising display means for displaying that the circulation means is in a circulation mode in which the circulation means is operated.

  According to the present invention, since the display means is provided, it can be easily known that the circulation means operates and is in the circulation mode.

1 is a configuration diagram showing a power steering device (Embodiment 1). The flowchart figure which shows the whole effect | action of a power steering apparatus (Embodiment 1). The flowchart figure which shows the circulation mode A of a power steering apparatus (Embodiment 1). The flowchart figure which shows the circulation mode B (Embodiment 1). The flowchart figure which shows the circulation mode C (Embodiment 1). The flowchart figure which shows the circulation mode D (Embodiment 1). The graph which shows the relationship between oil temperature and the opening degree of a solenoid valve (embodiment 1). The block diagram which shows a power steering apparatus (Embodiment 2).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Power steering apparatus 2 ... Power cylinder 3 ... Piston 4a ... 1st pressure chamber 4b ... 2nd pressure chamber 8a ... 1st flow path 8b ... 2nd flow path 9 ... Reversible pump 10 ... Motor 14 ... Communication path 15 ... Electromagnetic valve 16 ... Torque sensor 17 ... Oil temperature sensor 19 ... Circulating means 20 ... Stop state judging means 21 ... Running prevention means

Claims (3)

A power cylinder that applies assist force to the steering wheel, a reversible pump that selectively supplies hydraulic pressure to the pressure chambers on both sides of the piston of the power cylinder via the first and second flow paths, and the reversible pump A motor that rotates in the reverse direction, an assist force detection unit that detects an assist force of the power cylinder, and a motor that drives the motor to generate a predetermined hydraulic pressure based on the assist force detected by the assist force detection unit Motor control means for outputting a signal,
A communication path for circulating hydraulic oil from one of the first flow path and the second flow path toward the other; an on-off valve for turning on and off the flow of the communication path; and an environmental temperature or an operation A circulating means having a temperature measuring means for detecting or estimating the oil temperature;
A power steering apparatus characterized in that when the temperature measured by the temperature measuring means is equal to or lower than a predetermined value, the on-off valve is opened and the motor is rotated so that hydraulic oil is circulated by the reversible pump. . 2. The power steering apparatus according to claim 1, wherein a stop state determination unit that determines a stop state of the vehicle, and a case where the stop state determination unit determines that the vehicle is in a stop state and the circulation unit operates. A power steering device, characterized in that it is provided with a travel prevention means for preventing travel of the vehicle when the vehicle is on. 3. The power steering device according to claim 2, wherein the stop state determining means stops the vehicle based on at least one signal of a hand brake position, a foot brake position, an AT select lever position, an accelerator pedal opening, and a tachometer. A power steering apparatus characterized in that the state is determined.

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