JP2009023402A - Steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To early detect and notify a condition with a possibility of damage in rack boots 26R, 26L and intrusion of foreign matter in a gear housing 30. <P>SOLUTION: A check valve 70 and a pressure sensor 71 are provided in the gear housing 30. The inside of the gear housing 30 is maintained at a pressure higher than the atmosphere by supplying high pressure air from the check valve 70. The pressure (atmospheric pressure) in the gear housing 30 is detected by the pressure sensor 70, and when a condition where a detected pressure Px is lower than a determination reference value Pref continues for a determination reference time or longer, it is determined that an abnormality has occurred in air-tightness in a turning part 20 and an alarm 111 is operated. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a steering device for turning a wheel by a turning shaft provided in a housing so as to be displaceable in an axial direction (vehicle width direction).

  Conventionally, in a steering apparatus for a vehicle, the rotational movement of a steering shaft connected to a steering handle is converted into an axial movement of a rack shaft (steering shaft) by a rack and pinion mechanism and connected to both ends of the rack shaft. The wheel is steered by applying a steering force to the knuckle of the wheel via the tie rod (connection shaft). In such a steering device, the rack shaft is housed in the gear housing. Both ends of the rack shaft protrude from both end openings of the gear housing, and a tie rod is swingably connected via a ball joint. In the electric power steering apparatus, a ball screw mechanism is formed on the rack shaft as a speed reducer, and the ball screw nut is rotated by an electric motor provided coaxially with the rack shaft, thereby driving the rack shaft in the axial direction. Such a configuration is also known.

  In such a steering device, the front end opening of the gear housing is covered with a boot made of a bellows tube so that foreign matter does not enter the gear housing. Specifically, by fixing one end of the boot to the outer peripheral surface of the gear housing and fixing the other end of the boot to the outer peripheral surface of the tie rod, the connecting portion between the rack shaft and the tie rod that is the front end opening of the gear housing Covering. In such a configuration, when the boot is torn, water enters the gear housing and the deterioration (rust or the like) of the steering device is promoted. Further, when the electric motor is provided, the electric motor may be lost due to the invading water.

Therefore, in the steering device of Patent Document 1, a water sensor is provided at the distal end portion of the gear housing so as to detect water entering the gear housing.
JP 2006-111032 A

  However, in the above-described steering apparatus, even if water intrusion into the gear housing can be detected, intrusion of sand, foreign matter, etc. cannot be detected. Further, it is not possible to immediately detect an abnormality such as a broken boot. That is, in the steering device proposed in Patent Document 1, it is possible to detect a boot break only after water has entered the gear housing, and no abnormality can be detected until then. Therefore, there is a risk that the speed reduction mechanism in the gear housing will deteriorate in the meantime.

  The present invention has been made in order to cope with the above-described problem, and has an object to detect an abnormality such as a broken boot, that is, a state in which foreign matter may enter the gear housing at an early stage and notify the passenger. .

  In order to achieve the above object, the present invention is characterized in that a steered shaft that is displaced in an axial direction in accordance with a steering operation, and both ends of the steered shaft that are fixed to a vehicle body are exposed to make the steered shaft axial. A housing that is displaceably accommodated in the housing, a connecting shaft that is swingably connected to both ends of the steered shaft, and that transmits an operating force of the steered shaft to wheels, and is provided at both ends of the housing and seals the inside of the housing In the steering apparatus having a cover that covers a state, a gas that has a supply port for supplying a gas into the housing and that is supplied with the gas from the supply port and maintains the pressure inside the housing at a state higher than the atmospheric pressure. An enclosure means, a pressure detection means for detecting the atmospheric pressure in the housing held at a state higher than the atmospheric pressure, and the presence of an abnormality based on a decrease in the atmospheric pressure in the housing detected by the pressure detection means. And abnormality detecting means for determining, in that it comprises an abnormality informing means for informing the abnormality if it is determined there is an abnormality by said abnormality detection means.

  In the present invention, the steered shaft is displaced in the axial direction, and the wheels are steered via the connecting shafts connected to both ends of the steered shaft. The steered shaft is accommodated in the housing with its both ends (connecting portions with the connecting shaft) exposed. Covers that cover the housing in a sealed state are provided at both ends of the housing that houses the steered shaft. As this cover, for example, a boot is used. The housing is held in a state where the internal pressure is higher than the atmospheric pressure by the gas sealing means. The gas sealing means has a supply port for supplying a gas having a pressure higher than atmospheric pressure into the housing, and a closing function for closing the gas so as not to escape from the supply port after the gas is supplied. Accordingly, unless the cover is damaged or the seal abnormality of the housing does not occur, the pressure inside the housing is kept higher than the atmospheric pressure.

  The atmospheric pressure in the housing is detected by pressure detection means. The abnormality detection means determines the presence or absence of abnormality (presence or absence of abnormality in sealing of the housing) based on the detected decrease in atmospheric pressure in the housing. When a cover breakage or seal abnormality occurs, gas flows out from the abnormality occurrence part, and the atmospheric pressure in the housing decreases. Therefore, the abnormality detection means can determine the occurrence of an abnormality from this decrease in atmospheric pressure. For example, the detected atmospheric pressure in the housing (atmospheric pressure detected by the pressure detection means) is compared with a predetermined determination reference value, and it is determined that an abnormality has occurred when the detected atmospheric pressure falls below the determination reference value. The abnormality detection result is notified to the occupant by the abnormality notification means. As a result, it is possible to detect a state where a foreign object may enter the housing at an early stage and notify the occupant.

  Another feature of the present invention is that the gas sealing means is a check valve that allows gas to flow into the housing and prevents gas from flowing out of the housing.

  According to this invention, since the supply of the high-pressure gas into the housing and the closing operation after the gas supply are performed by the check valve, the gas sealing means can be configured simply. Further, the gas supply into the housing can be performed easily and reliably.

  Another feature of the present invention is that an electric motor driven in accordance with a steering operation is provided in the housing, and the rotational motion of the electric motor is converted into motion in the axial direction of the steered shaft via a ball screw mechanism. This is to provide a turning force.

In the present invention, the rotational torque of the electric motor is transmitted to the steered shaft via the ball screw mechanism to give the steered force. When such a ball screw mechanism is provided, it is particularly necessary to prevent foreign matters such as dust and sand from entering the ball screw mechanism in order to operate the electric motor reliably. In addition, it is necessary to prevent water from entering the connection portion of the electric motor. On the other hand, the present invention detects such a state (abnormal state) in which foreign matter or water may possibly enter at an early stage and notifies the occupant, so that it is possible to meet such a demand. As a result, the reliability of the steering control using the electric motor is improved.
The present invention is not limited to an electric power steering device that assists a steering operation performed by a driver with an electric motor, but also an electric motor that mechanically separates a steering handle and a steered shaft and operates in accordance with the steering operation. The present invention can also be applied to a by-wire type steering device that displaces the steered shaft in the axial direction with only the force of.

  Another feature of the present invention includes motor temperature acquisition means for acquiring estimated temperature information of the electric motor, and the abnormality detection means is adapted to reduce the atmospheric pressure in the housing based on the estimated temperature information of the electric motor. It is to change the abnormality determination level based on.

In this invention, since the electric motor is provided in the housing, the temperature in the housing changes depending on the energized state of the electric motor. For this reason, the atmospheric pressure in the housing changes. On the other hand, when drive control of an electric motor is performed, control for estimating the temperature of the electric motor in order to protect the motor from overheating and limiting the upper limit of the motor energization amount based on the estimated temperature may be incorporated. Therefore, in the present invention, the estimated temperature information of the electric motor is acquired, and the abnormality determination level based on the decrease in the atmospheric pressure in the housing is changed based on the estimated temperature. For example, the abnormality detection unit includes a comparison unit that compares the detected atmospheric pressure in the housing with a determination reference value, and a reference value change unit that changes the determination reference value to an increasing side as the estimated temperature increases, When the value falls below the criterion value, it is determined that an abnormality has occurred.
Therefore, the abnormality determination level becomes appropriate according to the temperature condition in the housing, and the abnormality determination accuracy is improved. Further, since the estimated motor temperature information is used, it is not necessary to provide a special temperature sensor for detecting the temperature in the housing.

  Hereinafter, an electric power steering apparatus as an embodiment according to the steering apparatus of the present invention will be described with reference to the drawings. The electric power steering apparatus of the present embodiment is a rack-and-pinion type steering apparatus having a power assist function. As shown in the schematic configuration diagram of FIG. A steering unit 20 that steers the wheel and a steering electronic control unit 100 (hereinafter referred to as a steering ECU 100). The operation unit 10 includes a steering handle 11 for a driver to perform a steering operation, and a steering shaft 12 having the steering handle 11 connected to one end and a pinion gear 13 fixed to the other end. The steering shaft 12 is provided with a torsion bar in the middle thereof, and a steering torque sensor 14 for detecting a steering torque based on a twist angle of the torsion bar by a steering operation.

  As shown in FIG. 2, the steered portion 20 includes a rack bar 21 (corresponding to a steered shaft of the present invention) formed with rack teeth 22 that mesh with the pinion gear 13, and a hollow cylindrical shape that houses the rack bar 21. The gear housing 30 is provided. The gear housing 30 includes a first housing 31 on the right wheel side, a second housing 32 on the left wheel side, and a yoke housing 33 provided between the housings 31, 32. Are connected coaxially. Each of the connecting portions of the three housings 31, 32, and 33 is provided with an elastic seal member. Air flows out of the gear housing 30 through the connecting portions, or air flows into the gear housing 30. To keep it airtight.

  The rack bar 21 is accommodated in the gear housing 30 so as to be movable in the axial direction. Both ends of the gear housing 30 are opened, and the tips (both ends) of the rack bar 21 are exposed from the openings. Rack end sockets 23R and 23L are fixed to the left and right ends of the rack bar 21, respectively. In the rack end sockets 23R and 23L, ball joints 25R and 25L provided at one ends of the left and right tie rods 24R and 24L are housed so as to be swingable. The tie rods 24R and 24L correspond to the connecting shaft of the present invention that connects the knuckle (not shown) fixed to the wheel and the rack bar 21, and the ball joints 25R and 25L provided at one end thereof are connected to the rack end socket 23R, By being housed in 23L, the rack bar 21 is swingably connected.

  In addition, rack boots 26 </ b> R and 26 </ b> L are attached to openings at both ends of the gear housing 30 so that foreign matter does not enter the gear housing 30. The rack boots 26R and 26L are made of rubber or elastic synthetic resin to form a bellows tube, one end of which is attached in close contact with the outer peripheral surface of the gear housing 30, and the other end is an intermediate portion of the tie rods 24R and 24L. It is attached in close contact with the outer peripheral surface. The rack boots 26R, 26L are attached by tightening radially inward using the bands 27R, 27L, 28R, 28L. Thereby, the inner peripheral surface of one end of the rack boots 26R, 26L and the outer peripheral surface of the gear housing 30 and the inner peripheral surface of the other end of the rack boots 26R, 26L and the outer peripheral surface of the tie rods 24R, 24L are in an airtight contact. Air does not flow in or out during that time. The rack boots 26R and 26L correspond to the cover of the present invention.

  In such a rack-and-pinion type steering device, when the driver rotates the steering handle 11, the steering shaft 12 is rotated by this operating force, and this rotational motion is transmitted to the rack bar 21 via the pinion gear 13. Is converted into a linear motion in the axial direction (vehicle width direction). As a result, the tie rods 24R, 24L are turned by turning the knuckles provided on the wheels in the pulling direction or rotating in the pushing direction.

  A cylinder hole 37 is formed in the first housing 31 at a position facing the pinion gear 13 across the rack bar 21 in a direction perpendicular to the axis of the rack bar 21, and is joined to the circumferential surface of the rack bar in the cylinder hole 37. A rack guide 38 is slidably accommodated. The rack bar 21 is pressed against the pinion gear 13 by a biasing force of a spring 39 provided on the back side of the rack guide 38. The cylinder hole 37 is hermetically sealed by a cap.

  An electric motor 40 is provided around the rack bar 21 in the yoke housing 33. The electric motor 40 is a brushless DC motor, and includes a drive stator 41 serving as a stator and a motor shaft 42 serving as a rotor. The drive stator 41 is configured by winding a coil around an iron core, and is fixed to the inner peripheral surface of the yoke housing 33. The motor shaft 42 has a hollow cylindrical shape, and is loosely fitted around the rack bar 21 coaxially. On the outer peripheral surface of the motor shaft 42, permanent magnets 43 are fixed at equal intervals in the circumferential direction so as to face the drive stator 41. The electric motor 40 is provided with a rotation angle sensor 44 that detects the rotation angle of the motor shaft 42. Since the detected angle detected by the rotation angle sensor 44 is proportional to the turning angle of the wheel, the rotation angle sensor 44 is also used as the turning angle sensor.

  One end of the motor shaft 42 extends into the first housing 31, is rotatably supported by the first housing 31 by a thrust bearing 34, and the other end is a connecting portion between the yoke housing 33 and the second housing 32. And is supported rotatably on the yoke housing 33 by a radial bearing 35. This also prevents the motor shaft 42 from moving relative to the gear housing 30 in the axial direction.

  A ball screw mechanism 50 is provided between the motor shaft 42 and the rack bar 21. The ball screw mechanism 50 includes a ball nut 51 that is fixed to one end of the motor shaft 42 so as not to be relatively rotatable, a ball screw 52 formed on the outer peripheral surface of the rack bar 21, and the ball nut 51 and the ball screw 52. And a plurality of rolling balls 53 provided so as to be capable of rolling.

  In the ball screw mechanism 50, when the electric motor 40 is energized, the motor shaft 42 rotates around the rack bar 21 with a predetermined torque. At this time, the ball nut 51 connected and fixed to the motor shaft 42 also rotates together with the motor shaft 42. Thereby, the rotational force of the ball nut 51 is converted into the moving force in the axial direction of the rack bar 21 via the rolling ball 53. Thus, the movement of the rack bar 21 in the axial direction causes the tie rods 24R and 24L to turn the knuckle of the wheel in the pulling direction or in the pushing direction. Thereby, the left and right wheels are steered.

  The second housing 32 is formed with a small-diameter portion 32a at the center so as to support the rack bar 21 so as to be relatively movable in the axial direction. A spiral communication groove (not shown) is formed on the inner peripheral surface of the small-diameter portion 32a, and both spaces are provided so that the right-side space and the left-side space of the small-diameter portion 32a in the second housing 32 have the same pressure. Is communicated. Therefore, the gear housing 30 communicates from the opening of the first housing 31 (connection with the rack boot 26R) to the opening of the second housing (connection with the rack boot 26L). It has become.

  The second housing 32 is formed with a tapered portion 32 b that is widened in a trumpet shape at a connection location with the yoke housing 33. A conical ring-shaped space S is formed around the rack bar 21 in the tapered portion 32b. The tapered portion 32b is provided with a check valve 70 and a pressure sensor 71 through the wall surface. The check valve 70 and the pressure sensor 71 are hermetically penetrated and fixed to the wall surface of the tapered portion 32b through a seal member (not shown).

  The check valve 70 constitutes the gas sealing means of the present invention, and forms a supply port for supplying high-pressure air into the gear housing 30, and air does not escape from the supply port to the outside of the gear housing 30. Has a function of closing. The check valve 70 is urged in a valve closing direction in a cylindrical valve housing 70a that communicates the inside and outside of the gear housing 30 (outside the gear housing 30) to form a gas supply port (not shown). A valve body is provided, and the valve closing state is maintained when the pressure inside the gear housing 30 is higher than the outside pressure, and the outside pressure is greater than a predetermined value than the pressure inside the gear housing 30 (more than the valve closing energizing pressure of the valve body). ) Open the valve when it is high. Therefore, the check valve 70 prevents gas from flowing out from the inside of the gear housing 30 and allows gas to flow into the gear housing 30. At the tip of the valve housing 70a of the check valve 70, a connection port (not shown) for connecting a high-pressure air supply device when air is sealed is formed.

  The pressure sensor 71 corresponds to atmospheric pressure detection means for detecting the pressure (atmospheric pressure) in the gear housing 30, and outputs a detection signal representing a detected atmospheric pressure value Px (hereinafter simply referred to as pressure Px) to the steering ECU 100.

  The gear housing 30 is attached to the vehicle body (suspension member) via rubber bushes 63 and 64 at two connecting portions 61 and 62 separated in the vehicle width direction.

  In the structure of the steered portion 20 described above, all the parts connected to the gear housing 30 from the outside are hermetically sealed by the sealing member, and both end openings of the gear housing 30 are also hermetically sealed by the rack boots 26R and 26L. Sealed. In the steering unit 20 assembled in this way, high pressure air is supplied from the check valve 70 into the gear housing 30 using a high pressure air supply device (not shown), and the internal pressure (atmospheric pressure) of the gear housing 30 is higher than atmospheric pressure. Adjusted to set pressure. In this case, the function of the check valve 70 prevents the air supplied into the gear housing 30 from flowing out. Accordingly, high-pressure air is sealed in the gear housing 30 and after the sealing, the internal pressure of the gear housing 30 is maintained within a predetermined range that is assumed in advance with reference to the set pressure.

  On the other hand, when the rack boots 26R and 26L are torn (hereinafter referred to as boot torn) or a failure occurs in the seal member provided at the external component connection location, the air enclosed in the gear housing 30 flows out. The internal pressure of the gear housing 30 decreases. Therefore, an abnormality in the steered portion 20 can be detected based on a decrease in the internal pressure of the gear housing 30.

  The internal pressure of the gear housing 30 varies depending on the environmental temperature, the heat generation state of the electric motor 40, the expansion and contraction of the rack boots 26R and 26L, and the like. Therefore, in the present embodiment, the set pressure in the gear housing 30 is determined so that normal / abnormal can be determined even if such fluctuations in internal pressure occur. For example, the set pressure is determined so that the pressure fluctuation range in the gear housing 30 at the normal time is higher than the maximum pressure value in the pressure fluctuation range in the gear housing 30 at the time of abnormality (at the time of air leakage).

  Next, the steering ECU 100 will be described. The steering ECU 100 includes a microcomputer including a CPU, a ROM, a RAM, and the like as a main part, and also includes a drive circuit, a current sensor, and the like (not shown) necessary for driving and controlling the electric motor 40. The steering ECU 100 connects sensors such as a steering torque sensor 14, a rotation angle sensor 44 (steering angle sensor), a vehicle speed sensor 110, and a pressure sensor 71 in order to perform steering assist control and turning unit abnormality detection processing. An alarm device 111 that provides various information such as abnormality information to the driver is connected.

  Next, steering assist control executed by the steering ECU 100 will be described. Since this steering assist control does not constitute a characteristic part of the present invention, only a brief description will be given. The steering ECU 100 performs steering assist control according to a steering assist control program stored in the ROM. When the steering assist control is started, the steering ECU 100 reads detection signals from the steering torque sensor 14 and the vehicle speed sensor 110, and calculates a target assist torque value corresponding to the detected steering torque and vehicle speed. Subsequently, the target current value of the electric motor 40 necessary for obtaining the target assist torque is calculated, and the target current value is fed back as an actual current value (current value flowing through the electric motor 40 detected by the current sensor). By doing so, the target drive voltage of the electric motor 40 according to the deviation between the target current value and the actual current value is set. Then, a motor drive circuit (not shown) is controlled by a motor control signal (for example, PWM control signal) corresponding to the target drive voltage. As a result, the electric motor 40 is driven and controlled according to the driver's steering operation state and the vehicle speed, and the optimum steering assist torque is obtained.

  Next, a steering part abnormality detection process executed by the steering ECU 100 will be described. FIG. 3 is a flowchart showing a steered portion abnormality detection routine executed by steering ECU 100. This steering part abnormality detection routine is stored as a control program in the ROM of the steering ECU 100, and is activated when an unillustrated ignition switch is turned on, and is repeated at a predetermined short cycle. The steered portion abnormality detection process is performed in parallel with the steering assist control described above.

  When the steered portion abnormality detection routine is activated, the steering ECU 100 reads the pressure Px detected by the pressure sensor 71 in step S11. Thereby, the pressure (atmospheric pressure) in the gear housing 30 is detected. Subsequently, in step S12, it is determined whether or not the detected pressure Px is lower than the determination reference value Pref.

  The gear housing 30 is filled with high-pressure air and maintained at a pressure higher than atmospheric pressure. The internal pressure of the gear housing 30 varies depending on the temperature in the gear housing 30, the expansion / contraction operation state of the rack boots 26R and 26L, and the variation range can be assumed in advance. Therefore, the determination reference value Pref used in step S12 is set to a value smaller than the minimum value of the assumed pressure fluctuation range. That is, when the steered portion is normal (when the rack boot is not broken or the seal is not abnormal), the determination reference value Pref is set to exceed the internal pressure Px of the gear housing 30.

  If the steered portion 20 is normal, “NO” is determined in step S12. In this case, the steering ECU 100 advances the process to step S13, and confirms whether or not the flag F is set to F = 0. The flag F is set to F = 0 when the steering unit abnormality detection routine is started, and is set to F = 1 immediately after the pressure drop in the gear housing 30 is detected as will be described later. Since F = 0 is set at the start of the steered portion abnormality detection routine, in this case, the determination in step S13 is “YES”, and the steered portion abnormality detection routine is once ended.

  The steered portion abnormality detection routine is repeated at a predetermined short cycle. If the pressure Px in the gear housing 30 falls below the determination reference value Pref while the processes in steps S11 to S13 are being repeated, the determination in step S12 is “YES”, and the steering ECU 100 proceeds to step S14. Proceed. In step S14, the setting state of the flag F is confirmed (F = 0?). If F = 0, F = 1 is set (S15). Subsequently, the steering ECU 100 increments the timer value of the clock timer by one unit in step S16. On the other hand, if it is determined in step S14 that the flag F is set to F = 1, the flag setting process is skipped and the timer increment process in step S16 is performed.

  Subsequently, in step S17, the steering ECU 100 reads the count value of the timer and determines whether or not the time is up, that is, whether or not the timer value has reached the determination reference time. If the time has not expired, the steered portion abnormality detection routine is once terminated. The steered portion abnormality detection routine is repeated at a predetermined short cycle, but in the next control cycle, the routine starts with the flag F set to F = 1. Therefore, in the next control cycle, when the pressure Px in the gear housing 30 is still below the determination reference value Pref (S12: YES), the timer is incremented as it is (S16), and the time-up determination process is performed. Is performed (S17).

  On the other hand, when the pressure Px in the gear housing 30 once lowered increases and exceeds the determination reference value Pref (S12: NO), the steering ECU 100 checks the flag F in step S13 (S13: NO), The process proceeds to step S19 to reset the timer. That is, the timer value is cleared to zero. Subsequently, the steering ECU 100 sets the flag F to F = 0 in step S20.

  The steering ECU 100 determines whether or not the state in which the pressure Px in the gear housing 30 has decreased continues for the determination reference time by repeating such processing (S11 to S17). And even if the pressure Px in the gear housing 30 decreases, a temporary thing, that is, the state where the pressure Px decreases does not continue for the determination reference time, and the pressure Px becomes equal to or higher than the determination reference value in the middle. In this case (S12: NO), the timer value is returned to the initial value (zero) at that time (S19).

  When the steering ECU 100 determines that the state in which the pressure Px in the gear housing 30 has decreased continues for the determination reference time (S17: YES), the steering ECU 20 determines that the steered portion 20 is abnormal, and step S18. The alarm 111 is operated to inform the driver of the abnormality. As the alarm device 111, a warning lamp or a warning buzzer may be used, but a display device that displays an abnormality by characters or an image may be used. Further, error information indicating the abnormality content is stored in a nonvolatile memory provided in the steering ECU 100.

  When the steering ECU 100 notifies the driver of the abnormality in step S18, the steering unit abnormality detection routine is terminated. In this case, the steered portion abnormality detection routine may be repeatedly executed even after the abnormality is detected, or may be terminated in a state where the operation of the alarm device 111 is continued.

  According to the steered portion abnormality detection routine described above, when the pressure in the gear housing 30 is set higher than the atmospheric pressure, and the decrease in the pressure Px detected by the pressure sensor 71 continues for a determination reference time or longer, It is determined that an abnormality (boot tear or seal abnormality) has occurred in the steered portion 20. Therefore, since the abnormality of the steered portion 20 can be detected at an early stage, it is possible to notify the driver of the abnormality before foreign matter, water, or the like enters the gear housing 30. As a result, it is possible to prevent problems such as short-circuiting of the electric motor 40 due to water intrusion and catching of foreign matters in the ball screw mechanism 50 and the rack and pinion gear mechanism.

  In addition, in determining the abnormality, since a temporary decrease in the pressure Px is excluded, an erroneous determination of abnormality is prevented. It should be noted that the determination reference time for checking the continuation of time may be appropriately set by a test or the like because an appropriate value varies depending on various conditions. Also, it is not always necessary to check time continuity. In this case, steps S13 to S17 and S19 to S20 of the steered portion abnormality detection routine can be omitted.

  Next, the modification regarding a steering part abnormality detection process is demonstrated. FIG. 4 is a flowchart showing a turning portion abnormality detection routine executed by the steering ECU 100 as a modified example. This steering part abnormality detection routine is obtained by adding the processes of steps S31 and S332 to the above-described steering part abnormality detection routine shown in FIG. 3, and the other processes are the same. Accordingly, the same steps as those described above are denoted by the same step numbers in the drawings and description thereof is omitted.

  In this modification, the processes of steps S31 and S32 are added between step S11 and step S12 in the previous steering part abnormality detection routine. In step S31, the estimated motor temperature Tm is read. The steering ECU 100 performs steering assist control in parallel with the abnormality detection process. When the steering assist control is being performed, the temperature of the electric motor 40 is estimated by calculation in order to prevent overheating of the electric motor 40, and the current that is supplied to the electric motor 40 based on the estimated motor estimated temperature Tm. The upper limit value is set. Therefore, in step S31, the latest motor estimated temperature Tm information calculated by the steering assist control is read.

Since a method for estimating the motor temperature is proposed in, for example, Japanese Patent Application Laid-Open No. 2006-115553, only a brief description will be given here.
The temperature of the electric motor 40 can be estimated from the ambient temperature and the amount of heat generated by energization. Therefore, the motor temperature is detected using a temperature detection value of a temperature sensor (not shown) provided in a motor drive circuit in the steering ECU 100 and a current detection value of a current sensor (not shown) that measures the current flowing through the electric motor 40. Is estimated. The electric motor 40 and the motor drive circuit are different from each other in the distance from the engine serving as a heat source. For this reason, a temperature difference ΔT exists between the ambient temperature To of the electric motor 40 and the detection value Ts of the temperature sensor. This temperature difference ΔT is assumed in advance. Therefore, the atmospheric temperature To of the electric motor 40 is obtained by adding this temperature difference ΔT to the detection value Ts of the temperature sensor.

On the other hand, the temperature fluctuation due to energization can be obtained by the following equation.
dTm = a · dTm−1 + β · (1−a) · Ix ²
Here, dTm is the current motor temperature fluctuation, Tm-1 is the previous motor temperature fluctuation (1 control period before), Ix is the current value flowing through the electric motor, and the value a is greater than “0” and “1”. A smaller constant, value β, is a predetermined temperature conversion coefficient. The motor temperature estimation calculation is repeatedly executed at an early control cycle.

The first term a · dTm−1 in the equation increases as the previous motor temperature fluctuation dTm−1 increases, and decreases as the previous motor temperature fluctuation dTm−1 decreases. This is a term representing the influence of the previous motor temperature fluctuation dTm-1 on the current motor temperature fluctuation dTm in consideration of natural heat radiation to the outside air of 40. The second term β · (1-a) · Ix ² is a term representing the amount of heat generated by flowing the motor current Ix through the electric motor 40. Therefore, the estimated motor temperature Tm is calculated by adding the ambient temperature To of the electric motor and the current motor temperature fluctuation dTm.
Tm = To + dTm

  Returning to the description of the steering part abnormality detection routine of FIG. When the steering ECU 100 reads the estimated motor temperature Tm information in step S31, the steering ECU 100 next calculates a determination reference value Pref corresponding to the estimated motor temperature Tm. This determination reference value Pref is a comparison determination value used for detecting a pressure drop in step S12 described above. For example, as shown in FIG. 5, the determination reference value Pref is set so as to increase (in this example, increase linearly) as the estimated motor temperature Tm increases. The steering ECU 100 stores the relationship of the determination reference value Pref with respect to the estimated motor temperature Tm in the ROM in the form of a function or a reference table, and calculates the determination reference value Pref using this function or the reference table.

  In step S12, the pressure reduction is determined using the calculated determination reference value Pref. About the process after step S12, it is the same as the steering part abnormality detection routine shown in FIG. 3 mentioned above.

  According to the steering part abnormality detection routine of this modification, the temperature state in the gear housing 30 is predicted using the estimated motor temperature Tm, and the determination reference value Pref is set according to the estimated motor temperature Tm. . The air pressure in the gear housing 30 increases as the temperature of the air in the gear housing 30 increases. Therefore, when the estimated motor temperature Tm is high and the gear housing 30 is predicted to be in a high temperature state, a large determination reference value Pref corresponding to that is used, and conversely, the gear housing 30 is in a normal temperature state. When a certain prediction is made, a small criterion value Pref corresponding to the prediction is used.

  Therefore, it is possible to perform the turning unit abnormality determination using an appropriate determination reference value Pref corresponding to the temperature state. As a result, it is possible to improve the sealing abnormality determination accuracy of the steered portion and prevent erroneous determination. Further, when the determination reference value Pref is fixed as in the previous steering part abnormality detection routine (FIG. 3), it is necessary to set the determination reference value Pref in consideration of the pressure fluctuation due to temperature change in advance. The determination reference value Pref is set lower. On the other hand, in the modified example, since the determination reference value Pref corresponding to the temperature condition is used, an abnormality can be detected early even under a high temperature condition. Further, since the temperature detection in the gear housing 30 is replaced with the estimated motor temperature, there is no need to provide a temperature sensor, and the number of parts and the cost are not increased.

As mentioned above, although the steering apparatus of this embodiment was demonstrated, this invention is not limited to the said embodiment, A various change is possible unless it deviates from the objective of this invention.
For example, in the present embodiment, an example of an electric power steering device that assists steering by the electric motor 40 has been described. However, the present invention may be applied to a steering device that assists steering by hydraulic pressure, or a steering device that does not have a steering assist function. Can also be applied. Further, the present invention can also be applied to a by-wire type steering device in which the mechanical connection between the operation unit that the driver operates the steering wheel and the steering unit that steers the wheel is disconnected.

  In the present embodiment, air is supplied in order to increase the pressure in the gear housing 30. However, the present invention is not limited to air, and other gases can be used.

It is a schematic structure figure of an electric power steering device of an embodiment. It is sectional drawing of the steering part in the electric power steering apparatus of embodiment. It is a flowchart showing the steering part abnormality detection routine which steering ECU in the electric power steering device of embodiment implements. It is a flowchart showing the modification of a steering part abnormality detection routine. It is a graph showing the relationship between motor estimated temperature and a criterion value.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Operation part, 11 ... Steering handle, 12 ... Steering shaft, 13 ... Pinion gear, 20 ... Steering part, 21 ... Rack bar (steering shaft), 22 ... Rack tooth, 24R, 24L ... Tie rod (connection shaft), 26R, 26L ... rack boot (cover), 30 ... gear housing (housing), 31 ... first housing, 32 ... second housing, 33 ... yoke housing, 40 ... electric motor, 50 ... ball screw mechanism, 51 ... ball nut 53 ... Rolling balls, 70 ... Check valve (gas sealing means), 70a ... Valve housing, 71 ... Pressure sensor, 100 ... Steering electronic control unit, 111 ... Alarm, Tm ... Motor estimated temperature.

Claims (4)

A steered shaft that is displaced in the axial direction in accordance with a steering operation;
A housing fixed to the vehicle body, exposing both ends of the steered shaft, and housing the steered shaft so as to be freely displaceable in the axial direction;
A connecting shaft that is swingably connected to both ends of the steered shaft, and that transmits the operating force of the steered shaft to the wheels;
A steering apparatus provided with covers provided at both ends of the housing and covering the inside of the housing in a sealed state,
A gas inlet means for supplying a gas into the housing, wherein gas is supplied from the supply port and the atmospheric pressure in the housing is kept higher than atmospheric pressure;
Pressure detecting means for detecting the atmospheric pressure in the housing held at a state higher than the atmospheric pressure;
An abnormality detection means for determining the presence or absence of an abnormality based on a decrease in the atmospheric pressure in the housing detected by the pressure detection means;
A steering apparatus comprising: an abnormality notifying unit that notifies an abnormality when the abnormality detecting unit determines that there is an abnormality.   The steering apparatus according to claim 1, wherein the gas sealing means is a check valve that allows gas to flow into the housing and prevents gas from flowing out of the housing.   An electric motor driven in accordance with a steering operation is provided in the housing, and a turning force is applied by converting a rotational movement of the electric motor into a movement in the axial direction of the turning shaft via a ball screw mechanism. The steering apparatus according to claim 1 or 2. Motor temperature acquisition means for acquiring estimated temperature information of the electric motor,
4. The steering apparatus according to claim 3, wherein the abnormality detection means changes an abnormality determination level based on a decrease in atmospheric pressure in the housing based on estimated temperature information of the electric motor.

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