JP2008195307A - Power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power steering device capable of greatly reducing power consumption and contributing to improvement of fuel consumption.
Oil paths P1 and P2 are connected to oil chambers 24 and 25 of a power cylinder 20, respectively, and an electric pump unit 30, a reservoir tank 40 and a flow path control mechanism 50 are connected to the oil paths P1 and P2. It is connected so that it can communicate. The control mechanism 50 includes mechanical valves 51 and 52 provided in the oil passages P1 and P2 and a differential pressure operation mechanism unit 53. The differential pressure operation mechanism unit 53 includes a rod 53a, a differential pressure piston 53b, and a cylinder 53c, and pressure chambers 53d and 53e are formed. The pressure chambers 53d and 53e are connected to discharge oil passages 34 and 33 communicating with the oil pump 31, respectively. Then, by introducing the hydraulic oil into the pressure chambers 53d and 53e, the flow path control position of the mechanical valves 51 and 52 is switched to the communication prohibited position.
[Selection] Figure 2

Description

  The present invention includes a steering mechanism coupled to a steering shaft for transmitting a steering wheel operation by a driver, a power cylinder for assisting a steering force for steering a steered wheel coupled to the steering mechanism, A reversible oil pump having a pair of discharge ports for pumping hydraulic oil through a first oil passage or a second oil passage communicating with each oil chamber of the power cylinder, and an electric motor for rotating the oil pump forward and backward. An electric pump unit, a reservoir tank that can communicate with the first oil passage and the second oil passage, and a flow passage that permits or prohibits communication between the first oil passage, the second oil passage, and the reservoir tank. The present invention relates to a power steering device including a control mechanism.

  Conventionally, for example, a power steering apparatus as shown in Patent Document 1 below is known. This conventional power steering device includes a bypass passage that mutually bypasses both discharge-side communication passages communicated with both pressure chambers of the power cylinder, and an electromagnetic valve provided in the middle of the bypass passage. . And this solenoid valve will be in a closed state by energizing, and will be in an open state by releasing energization. By providing such an electromagnetic valve, when a failure is detected in the power steering apparatus, the electromagnetic valve is opened, and the operation of the power cylinder is set free by the bypass flow path. This prevents the steering feeling from deteriorating and ensures a manual steering state.

  Conventionally, for example, a power steering apparatus as shown in Patent Document 2 below is also known. This conventional power steering apparatus includes a fail-safe valve provided on an oil passage that communicates the first oil passage and the second oil passage communicated with both pressure chambers of the power cylinder without using an oil pump. As the fail-safe valve, a normally open valve that is closed when a voltage is supplied and opened when no voltage is supplied is used. By providing such a fail-safe valve, even if some abnormality occurs in the steering system and the power supply is shut down, both pressure chambers of the power cylinder can be brought into communication, and the assist torque Normal steering without any can be secured.

Furthermore, conventionally, for example, a power steering apparatus as shown in Patent Document 3 below is also known. The conventional power steering device includes a first branch oil passage and a second branch oil passage connected to the first oil passage and the second oil passage communicated with both pressure chambers of the power cylinder and communicating with the reservoir tank, A first electromagnetic switching valve and a second electromagnetic switching valve are provided for the first branch oil passage and the second branch oil passage, respectively. The first electromagnetic switching valve and the second electromagnetic switching valve are in a closed state when a voltage is supplied, and a normally open valve that is in an open state when no voltage is supplied is used. . By providing such a first electromagnetic switching valve and a second electromagnetic switching valve, even if some abnormality occurs in the steering system and the supply of power is shut down, both pressure chambers of the power cylinder are stored in the reservoir tank. In this way, normal steering without assist torque can be secured.
JP 2002-145087 A JP-A-2005-47296 JP 2005-41302 A

  By the way, in the power steering apparatus shown in Patent Documents 1 to 3 described above, when assist torque is applied to the rotation operation of the steering wheel by the driver, an electromagnetic valve, a fail-safe valve, the first or second electromagnetic wave is provided. It is necessary to continue supplying voltage to the switching valve. As a result, during normal travel, there is a concern that the amount of power consumption increases and the fuel consumption deteriorates. Moreover, in the power steering apparatus shown by the said patent documents 1-3, the complicated electric circuit for electrically controlling an electromagnetic valve, a fail safe valve, and the 1st or 2nd electromagnetic switching valve is required. The power steering device itself becomes complicated.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a power steering device that can greatly reduce power consumption and contribute to improvement in fuel consumption.

  In order to achieve the above object, a feature of the present invention is that a steering mechanism connected to a steering shaft for transmitting a steering wheel operation by a driver and a steered wheel connected to the steering mechanism are steered. A reversible oil pump having a power cylinder for assisting steering force, a pair of discharge ports for pumping hydraulic oil through a first oil passage or a second oil passage communicating with each oil chamber of the power cylinder, and the oil An electric pump unit comprising an electric motor for rotating the pump forward and reverse, a reservoir tank capable of communicating with the first oil passage and the second oil passage, the first oil passage, the second oil passage, and the reservoir tank A power steering apparatus including a flow path control mechanism that permits or prohibits communication with the flow path control mechanism, wherein the flow path control mechanism is disposed between the first oil path and the reservoir tank. And an oil pump that is provided between the second oil passage and the reservoir tank, and can be switched between a communication permission state that permits the flow of hydraulic oil and a communication prohibition state that prohibits the flow of hydraulic oil. From a pair of mechanical valves that maintain the communication permission state by an elastic member that is set to a predetermined biasing force when the oil pump is stopped, and the oil pump that is operated to When hydraulic oil is pumped to the first oil path or the second oil path, the first oil path side or the second oil path side from which the hydraulic oil is pumped from the discharge port of the pair of mechanical valves The difference between the mechanical valve provided in the switch from the communication permission state to the communication prohibition state against the urging force of the elastic member using the pressure of the hydraulic oil pumped from the discharge port. It lies in the configuration in the operation mechanism.

  In this case, the differential pressure operation mechanism portion is a rod that can contact the pair of mechanical valves, a piston that is liquid-tightly fixed to the rod, and the rod and the piston that are liquid-tight and slidable. A cylinder that is movably accommodated, and pumps one of the pressure chambers formed by the rod, piston, and cylinder from one of the pair of discharge ports as the electric pump unit operates. First hydraulic oil is introduced, and the rod and piston are moved by a pressure difference caused by the pressure of the introduced hydraulic oil, and the hydraulic oil is pumped from the discharge port of the pair of mechanical valves. When the mechanical valve provided on the road side or the second oil path side is switched from the communication permission state to the communication prohibition state against the urging force of the elastic member. There.

  According to these, when the driver operates the steering wheel to steer the steered wheels, the electric pump unit operates in accordance with the operation direction of the steering wheel, and the first oil passage with respect to each oil chamber of the power cylinder. Alternatively, the steering force is assisted (assisted) by pumping hydraulic oil through the second oil passage. At this time, in the flow path control mechanism, the differential pressure operation mechanism unit uses the pressure of the hydraulic oil pumped by the operation of the electric pump unit, and the first oil path or the second oil path to which the hydraulic oil is pumped, More specifically, the mechanical valve provided on the side corresponding to the first oil passage or the second oil passage that supplies high-pressure hydraulic oil to the oil chamber of the power cylinder is switched from the communication permission state to the communication prohibition state.

  More specifically, by introducing hydraulic oil to one of the pressure chambers formed by constituting the differential pressure operation mechanism portion from a rod, a piston and a cylinder, a pressure difference is generated between these pressure chambers. The rod and the piston move integrally in the low pressure side direction. The mechanical valve provided on the side corresponding to the first oil passage or the second oil passage that supplies high-pressure hydraulic oil to the oil chamber of the power cylinder communicates with the force that acts mechanically as the rod moves. It is switched from the permitted state to the communication prohibited state. Thereby, it is possible to prevent high-pressure hydraulic oil from flowing to the reservoir tank via the mechanical valve, and the power cylinder can appropriately assist (assist) the steering force. Therefore, the driver can easily operate the steering wheel.

  As described above, the mechanical valve can be switched from the communication permission state to the communication prohibition state by using the pressure of the hydraulic oil necessary for assisting the steering force. That is, when operating the power cylinder to assist the steering force, it is not necessary to provide a member that requires electric power, such as an electromagnetic switching valve, except for the electric pump unit. Therefore, useless power consumption can be greatly reduced, and as a result, improvement in fuel consumption can be expected. Further, since the mechanical valve can be mechanically switched, a complicated electric circuit is not required. Therefore, the power steering device itself can be simplified.

  Further, when the electric pump unit is stopped, for example, when the steering wheel is not operated by the driver or when the electric pump unit is stopped due to a failure, the hydraulic oil is not pumped, so a pair of mechanical pumps The valve is maintained in a communication-permitted state by an elastic member. Therefore, particularly when the electric pump unit is out of order, the first oil passage and the second oil passage are in communication with the reservoir tank, in other words, the oil chambers of the power cylinder and the reservoir tank are in communication. Therefore, the hydraulic oil can be circulated between each oil chamber of the power cylinder and the reservoir tank. Therefore, even when the electric pump unit is out of order, the driver can steer the steered wheels by operating the steering wheel, although assistance by the power cylinder cannot be obtained.

  In addition, another feature of the present invention is that an additional force greater than an urging force of an elastic member that maintains the pair of mechanical valves in the communication permission state between the electric pump unit and the flow path control mechanism. There may be provided a control valve having an elastic member set to a force to control the pressure of the hydraulic oil in the first oil passage and the second oil passage to a predetermined pressure.

  According to this, it is possible to provide a control valve having an elastic member set to an urging force larger than the urging force of the elastic member that maintains the mechanical valve in the communication permission state between the electric pump unit and the flow path control mechanism. it can. As a result, the electric pump unit starts pressure feeding of the hydraulic oil, and the differential pressure operation mechanism is preferentially operated before the pumped hydraulic oil flows from the first oil path or the second oil path to the reservoir tank. As a result, the mechanical valve can be promptly switched from the communication permitted state to the communication prohibited state. As a result, the hydraulic oil can be pumped to each oil chamber of the power cylinder with high responsiveness to the steering wheel operation by the driver, and the steering force can be assisted. Therefore, the driver can obtain a good steering feeling.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically shows an embodiment in which a power steering apparatus according to the present invention is applied to a rack and pinion type power steering apparatus. The power steering apparatus includes a steering wheel 11 that is rotated by a driver. The steering wheel 11 is fixed to the upper end of the steering shaft 12, and a pinion gear 13 constituting a rack-and-pinion type steering mechanism is integrally assembled to the lower end of the steering shaft 12. And the pinion gear 13 has meshed | engaged with the rack bar 14 which comprises a steering mechanism.

  The rack bar 14 moves in the axial direction when the rotation of the pinion gear 13 that rotates integrally with the turning operation of the steering wheel 11 by the driver is transmitted. Thereby, steered wheels (not shown) connected to both ends of the rack bar 14 in a well-known manner are steered as the rack bar 14 moves in the axial direction. In this power steering device, the axial movement of the rack bar 14, in other words, the turning operation of the steering wheel 11 by the driver is assisted (assisted) by the power cylinder 20.

  The power cylinder 20 is configured such that a part of the rack bar 14 serves as a rod 21 and a part of the housing 15 that houses a turning mechanism composed of the pinion gear 13 and the rack bar 14 serves as a cylinder 22. . A piston 23 is fixed in a liquid-tight manner on the outer periphery of the rod 21, and the piston 23 is accommodated in a liquid-tight manner and slidably between the inner peripheral surface of the cylinder 22. In the power cylinder 20 configured as described above, the first oil chamber 24 and the second oil chamber 25 are formed by the rod 21, the cylinder 22 and the piston 23. And the 1st oil path P1 and the 2nd oil path P2 are connected to the formed 1st oil room 24 and the 2nd oil room 25, respectively, and the 1st oil path P1 and the 2nd oil path P2 are connected, respectively. The electric pump unit 30 and the reservoir tank 40 are connected so as to be able to communicate with each other.

  The electric pump unit 30 includes a reversible oil pump 31 and an electric motor 32 that rotates the oil pump 31 forward and backward. The oil pump 31 has a pair of first discharge port 31 a and second discharge port 31 b that switch the discharge direction according to the rotation direction of the electric motor 32. The first discharge port 31 a of the oil pump 31 is connected to the first oil passage P <b> 1 via the first discharge oil passage 33 and communicates with the first oil chamber 24 of the power cylinder 20. The second discharge port 31 b of the oil pump 31 is connected to the second oil passage P <b> 2 via the second discharge oil passage 34 and communicates with the second oil chamber 25 of the power cylinder 20.

  The reservoir tank 40 is provided in communication with a third oil passage P3 that connects the end portion of the first oil passage P1 and the end portion of the second oil passage P2. The reservoir tank 40 is maintained at atmospheric pressure, and hydraulic oil for supplying and discharging the first oil chamber 24 and the second oil chamber 25 with the operation of the power cylinder 20 and the electric pump unit 30 is supplied. It is something to store.

  Further, the first oil passage P1 and the second oil passage P2 can communicate with a flow path control mechanism 50 that switches between supply and discharge of hydraulic oil to and from the power cylinder 20 between the electric pump unit 30 and the reservoir tank 40. It is connected to the. The flow path control mechanism 50 includes a first mechanical valve 51 provided in the first oil path P1, a second mechanical valve 52 provided in the second oil path P2, and flow control of the first and second mechanical valves. And a differential pressure operation mechanism unit 53 for switching positions.

  The first mechanical valve 51 and the second mechanical valve 52 include first ports 51a and 52a connected to the arrangement side (hereinafter referred to as the upstream side) of the electric pump unit 30 in the first oil passage P1 or the second oil passage P2. A flow path that has second ports 51b and 52b connected to the arrangement side (hereinafter referred to as the downstream side) of the reservoir tank 40, and permits communication between the first ports 51a and 52a and the second ports 51b and 52b. A control position (hereinafter, this position is referred to as a communication permission position) and a flow path control position (hereinafter, this position is referred to as a communication prohibition position) that prohibits the communication state between the first ports 51a, 52a and the second ports 51b, 52b. Is a 2-port 2-position switching valve. Further, the first mechanical valve 51 and the second mechanical valve 52 are provided with springs 51c and 52c as elastic members that apply a biasing force so that the flow path control position changes from the communication prohibition position to the communication permission position, respectively. ing.

  The differential pressure operation mechanism 53 moves in the axial direction to switch the flow path control position of the first or second mechanical valve 51, 52 from the communication permission position to the communication prohibition position, and the liquid with respect to the rod 53a. A differential pressure piston 53b that is tightly caulked and fixed and a cylinder 53c that accommodates the differential pressure piston 53b in a liquid-tight and slidable manner are configured. With this configuration, in the differential pressure operation mechanism unit 53, the first pressure chamber 53d and the second pressure chamber 53e are formed by the rod 53a, the differential pressure piston 53b, and the cylinder 53c. The formed first pressure chamber 53 d communicates with the second discharge oil passage 34 in the electric pump unit 30 via the first branch oil passage 54. Further, the formed second pressure chamber 53 e communicates with the first discharge oil passage 33 in the electric pump unit 30 via the second branch oil passage 55.

  By configuring the flow path control mechanism 50 in this way, in a situation where a pressure difference is generated between the first pressure chamber 53d and the second pressure chamber 53e of the differential pressure operation mechanism unit 53, the rod 53a and the differential pressure piston. 53b moves from the high pressure side to the low pressure side. When the rod 53a and the differential pressure piston 53b move as described above, the flow control position of the first mechanical valve 51 or the second mechanical valve 52 in the moving direction is obtained by applying a mechanical force accompanying the movement of the rod 53a. Are switched from the communication permission position to the communication prohibition position against the urging force of the springs 51c and 52c. Further, in a situation where no pressure difference is generated between the first pressure chamber 53d and the second pressure chamber 53e of the differential pressure operation mechanism 53, the rod 53a and the differential pressure piston 53b are connected to the first mechanical valve 51 and the second mechanical valve 51b. The spring 52c of the valve 52 moves to the neutral position by the urging force of the springs 52c. Thereby, the flow path control positions of the first mechanical valve 51 and the second mechanical valve 52 are each maintained at the communication permission position.

  Here, the pressure receiving area of the differential pressure piston 53b is set larger than the pressure receiving areas of the first port 51a and the first port 52a. For this reason, even if the pressure of the hydraulic fluid in the first discharge oil passage 33 or the second discharge oil passage 34 increases, the flow control position of the first mechanical valve 51 or the second mechanical valve 52 is surely set. It is possible to maintain the communication prohibited position.

  Furthermore, composite valves 60 are respectively provided between the electric pump unit 30 and the flow path control mechanism 50 in the first oil path P1 and the second oil path P2. The composite valve 60 includes a check valve 61 that prohibits the flow of hydraulic oil from the upstream side to the downstream side of the first oil path P1 or the second oil path P2, and hydraulic oil from the upstream side to the downstream side at a predetermined pressure or higher. And a check valve 62 with a spring as a control valve that permits the flow of the gas. The check valve 62 with a spring includes a spring 62a as an elastic member set to a biasing force larger than the biasing force of the springs 51c and 52c in the first and second mechanical valves 51 and 52, and the spring 62a determines a predetermined force. Allow the hydraulic fluid to flow from the upstream side to the downstream side at a pressure higher than.

  Further, the power steering device is provided with an electric control device 70 that controls the rotational drive of the electric motor 32 constituting the electric pump unit 30. The electric control device 70 includes a steering angle sensor 71 that detects a rotation operation amount (corresponding to the actual steering angle) of the steering wheel 11 by the driver, and a rotation operation force (corresponding to the actual steering torque) of the steering wheel 11 by the driver. ) Is detected.

  For example, the steering angle sensor 71 is assembled to a steering shaft 12 that rotates integrally with the steering wheel 11, and outputs a rotation operation amount of the steering wheel 11 by the driver as a steering angle θ. For example, the steering torque sensor 72 is assembled to the steering shaft 12, detects the amount of twist associated with the rotation of the shaft 12, and outputs the torque corresponding to the detected amount of twist as the steering torque T.

  These sensors 71 and 72 are connected to the electronic control unit 73. The electronic control unit 73 includes a microcomputer including a CPU, a ROM, a RAM, and the like as main components, and controls the rotational drive of the electric motor 32 by executing various programs (not shown). For this reason, a drive circuit 74 for rotating the electric motor 32 is connected to the output side of the electronic control unit 73. In the drive circuit 74, a current detector 74a for detecting a drive current flowing through the electric motor 32 is provided. The drive current detected by the current detector 74a is fed back to the electronic control unit 73. Based on the fed back drive current, the electronic control unit 73 drives the electric motor 32 to rotate and rotates the motor 32. It is determined whether or not the drive is normal.

  Next, the operation of the power steering apparatus according to this embodiment configured as described above will be described. When the steering wheel 11 is rotated in the left-right direction by the driver, the electronic control unit 73 performs an electric pump unit according to the detected steering angle θ and the detected steering torque T from the steering angle sensor 71 and the steering torque sensor 72. 30 electric motors 32 are driven to rotate. More specifically, when the driver rotates the steering wheel 11 in the right direction in FIG. 1, the electronic control unit 73 drives the electric motor 32 to rotate forward. When the driver is turning the steering wheel 11 leftward in FIG. 1, the electronic control unit 73 drives the electric motor 32 to rotate in the reverse direction. In the following description, the driver will rotate the steering wheel 11 in the right direction, in other words, the case where the electric motor 32 is driven to rotate in the forward direction will be described in detail.

  When the electric motor 32 of the electric pump unit 30 is driven to rotate in the forward direction, the oil pump 31 also rotates in the forward direction along with the forward rotation drive. As a result, the oil pump 31 supplies the pressurized hydraulic oil from the first discharge port 31 a to the first oil path P <b> 1 via the first discharge oil path 33 and is connected to the first discharge oil path 33. Pressurized hydraulic oil is supplied to the second pressure chamber 53e in the differential pressure operation mechanism 53 of the flow path control mechanism 50 through the two-branch oil path 55.

  Thus, in a state where pressurized hydraulic oil is supplied from the oil pump 31 to the first oil passage P1 and the second pressure chamber 53e of the differential pressure operation mechanism 53, first, the flow of the first mechanical valve 51 The road control position is switched from the communication permission position to the communication prohibition position. Hereinafter, the switching of the flow path control position will be specifically described with reference to FIG.

  As described above, the check valve 61 forming the composite valve 60 prohibits the flow of hydraulic oil from the upstream side to the downstream side. The check valve 62 with spring forming the composite valve 60 prohibits the flow of the hydraulic oil from the upstream side to the downstream side by the urging force of the spring 62a until the hydraulic oil pressure becomes a predetermined pressure or higher. For this reason, the pressure of the hydraulic oil discharged from the first discharge port 31a of the oil pump 31 is such that the first discharge oil passage 33 and the composite valve 60 are used when the flow control position of the first mechanical valve 51 is in the communication permission position. In the first oil passage P1, the second branch oil passage 55, and the second pressure chamber 53e of the differential pressure operation mechanism 53 on the upstream side, the pressure is increased until a predetermined pressure is reached.

  On the other hand, when the oil pump 31 rotates forward, hydraulic oil is sucked through the second discharge port 31b. That is, when the oil pump 31 is rotating forward, a pressure difference is generated between the first discharge port 31a side and the second discharge port 31b side, and the hydraulic oil on the second discharge port 31b side It becomes a low pressure compared with the 1 discharge port 31a side. Therefore, the second discharge oil passage 34 that communicates with the second discharge port 31b, the second oil passage P2, the first branch oil passage 54, and the first branch oil passage 54 that communicate with the second discharge passage 34 communicate with each other. The first pressure chamber 53d is also at a relatively low pressure.

  Here, since the flow path control position of the second mechanical valve 52 is maintained at the communication permission position, the upstream side (the arrangement side of the electric pump unit 30) is lower than the composite valve 60, and the downstream side (the reservoir tank 40) (Placement side) becomes equal to atmospheric pressure. Then, due to this pressure difference, as shown in FIG. 2, the check valve 61 of the composite valve 60 is allowed to flow hydraulic oil from the downstream side to the upstream side, and the second discharge oil passage 34, the second oil passage P2, the first branch oil passage 54, the first pressure chamber 53d, and the reservoir tank 40 are in communication with each other. As a result, the hydraulic oil can flow from the reservoir tank 40 toward the second discharge port 31b of the oil pump 31, and is on the second discharge port 31b side, that is, in the first pressure chamber 53d of the differential pressure operation mechanism 53. The pressure of the hydraulic oil is on the low pressure side equal to the atmospheric pressure.

  By the way, the urging force of the spring 51 c provided in the first mechanical valve 51 is set to be smaller than the urging force of the spring 62 a in the check valve 62 with the spring forming the composite valve 60. For this reason, before the check valve 62 with a spring of the composite valve 60 permits the flow of the hydraulic oil from the upstream side to the downstream side, in other words, before the pressure of the pressurized hydraulic oil becomes a predetermined pressure, The rod 53a and the differential pressure piston 53b are integrated with the first mechanical valve against the urging force of the spring 51c by the pressure of the hydraulic oil flowing from the first discharge port 31a of the oil pump 31 to the two pressure chambers 53e. Move in the direction of 51. Thereby, the flow path control position of the first mechanical valve 51 is switched from the communication permission position to the communication prohibition position as shown in FIG. Here, since the pressure receiving area of the differential pressure piston 53b is set larger than the pressure receiving area of the first port 51a, even if the pressure of the hydraulic oil in the first discharge oil passage 33 rises, The flow path control position of the 1 mechanical valve 51 can be maintained at the communication prohibited position.

  The rod 53a and the differential pressure piston 53b integrally move in the direction of the first mechanical valve 51, whereby the hydraulic oil in the first pressure chamber 53d of the differential pressure operation mechanism unit 53 is compressed. In this case, since the second discharge oil passage 34, the second oil passage P2, the first branch oil passage 54, the first pressure chamber 53d, and the reservoir tank 40 are in communication, a part of the compressed hydraulic oil is oil. The air is sucked in from the second discharge port 31b of the pump 31, and the remainder flows into the reservoir tank 40 and is stored.

  As described above, when the pressure of the hydraulic oil discharged from the first discharge port 31a of the oil pump 31 rises above a predetermined pressure in a state where the flow path control position of the first mechanical valve 51 is switched to the communication prohibition position. The check valve 62 with a spring permits the flow of hydraulic oil from the upstream side to the downstream side. In this situation, since the flow path control position of the first mechanical valve 51 is the flow prohibition position, the composite valve 60 (from the first oil chamber 24 of the power cylinder 20 and the power cylinder 20 of the first oil path P1). Specifically, until the check valve 61 and the check valve with spring 62), the pressure in the first discharge passage 33, the second branch oil passage 55, and the second pressure chamber 53e of the differential pressure operation mechanism 53 is equal to or higher than a predetermined pressure. Becomes equal.

  On the other hand, the second oil chamber 25 of the power cylinder 20 communicates with the second oil passage P2. Here, as described above, the pressure of the hydraulic oil in the second oil passage P2 is equal to the atmospheric pressure. For this reason, the pressure of the hydraulic oil in the second oil chamber 25 is also equal to the atmospheric pressure. As a result, the piston 23 of the power cylinder 20 moves together with the rod 21 in the direction of the second oil chamber 25 on the low pressure side due to the pressure difference between the first oil chamber 24 and the second oil chamber 25. Therefore, when the driver rotates the steering wheel 11 in the right direction in FIG. 2, an appropriate assist force is applied by the power cylinder 20, and the steering torque T input to the steering wheel 11 by the driver is applied. Can be small.

  Further, when the driver does not rotate the steering wheel 11, that is, the driver holds the steering wheel 11 at the neutral position so that the vehicle travels straight, the steering angle θ and the steering torque T are substantially “ In the case of “0”, the electronic control unit 73 does not rotate the electric motor 32 of the electric pump unit 30. For this reason, hydraulic oil is not discharged from the oil pump 31, and the pressure difference between the first pressure chamber 53d and the second pressure chamber 53e in the differential pressure operation mechanism portion 53 of the flow path control mechanism 50 is as shown in FIG. Does not occur. Therefore, the flow path control positions of the first mechanical valve 51 and the second mechanical valve 52 are maintained at the communication permission position by the urging force of the springs 51c and 52c, respectively.

  On the other hand, the flow of the hydraulic oil from the first oil chamber 24 and the second oil chamber 25 of the power cylinder 20 to the reservoir tank 40 is performed by the composite valve 60 provided in each of the first oil passage P1 and the second oil passage P2. It is regulated by a check valve 61 and a check valve 62 with a spring. That is, the pressure of the hydraulic oil in the first oil chamber 24 and the second oil chamber 25 of the power cylinder 20 is adjusted by the check valve 62 with a spring so as to be less than a predetermined pressure. Thereby, for example, even when a disturbance is input from the steered wheels due to the unevenness of the road surface, the pressure of the hydraulic oil in the first oil chamber 24 and the second oil chamber 25 is appropriately maintained and is good. Can obtain a good damping characteristic.

  Furthermore, even if an abnormality occurs in the operation of the electric motor 32 or the power supply in the electric pump unit 30 and an appropriate assist force cannot be applied, the driver pushes the steering wheel 11 by a manual operation without the assist force. The steered wheels can be steered by turning. Specifically, when the electronic control unit 73 determines that an abnormality has occurred in the operation or power supply of the electric motor 32 based on the drive current fed back from the current detector 74a of the drive circuit 74, the electric motor The rotational drive of 32 is stopped. In this case, for example, when a pressure difference is generated between the first pressure chamber 53d and the second pressure chamber 53e in the differential pressure operation mechanism unit 53, the first branch oil passage 54 and the second branch oil are respectively obtained. By communicating with the passage 55 and the oil pump 31, the pressure difference is eliminated. Thereby, the flow path control positions of the first mechanical valve 51 and the second mechanical valve 52 are switched to the communication permission position by the biasing force of the springs 51c and 52c, respectively, as shown in FIG.

  In this state, when the driver rotates the steering wheel 11 in the left-right direction, the rotation of the wheel 11 is transmitted to the rack bar 14 via the steering shaft 12 and the pinion gear 13. The rack bar 14 moves in the axial direction together with the piston 23 of the power cylinder 20 by the transmitted rotation. Thereby, for example, if the steering wheel 11 is rotated to the right in FIG. 3 by the driver, the piston 23 moves to the right, and if the steering wheel 11 is rotated to the left, the piston 23 moves to the left. Move to. As a result, in the power cylinder 20, the pressure of the hydraulic oil in the second oil chamber 25 is increased by the movement of the piston 23 in the right direction, and the operation in the first oil chamber 24 is performed by the movement of the piston 23 in the left direction. The oil pressure increases.

  As described above, when the pressure of the hydraulic oil in the first oil chamber 24 or the second oil chamber 25 of the power cylinder 20 increases, the first oil passage P1 or the second oil passage communicated with each of the oil chambers 24 and 25, respectively. The pressure of the hydraulic oil in the oil path P2 also increases. When the pressure of the hydraulic oil in the first oil path P1 or the second oil path P2 increases to a predetermined pressure or higher, the check valve with spring 62 that forms the composite valve 60 permits the flow of the hydraulic oil to the downstream side. Then, the distributed hydraulic oil flows to the reservoir tank 40 through the first mechanical valve 51 or the second mechanical valve 52.

  On the other hand, in the second oil chamber 25 or the first oil chamber 24 on the opposite side to the direction in which the piston 23 moves, hydraulic oil is sucked in as the piston 23 moves. That is, in the second oil chamber 25 or the first oil chamber 24 on the opposite side, the second oil communicated with each of the oil chambers 25, 24 due to a relative decrease in pressure as the piston 23 moves. The pressure of the hydraulic oil in the path P2 or the first oil path P1 is also relatively reduced. When the pressure of the hydraulic oil in the second oil passage P2 or the first oil passage P1 is relatively decreased, the check valve 61 forming the composite valve 60 is connected to the hydraulic oil in the reservoir tank 40 equal to the atmospheric pressure. Due to the pressure difference between the two oil passages P2 and the hydraulic oil in the first oil passage P1, a state in which the circulation of the hydraulic oil from the reservoir tank 40 toward the second oil chamber 25 or the first oil chamber 24 is permitted. . As a result, the hydraulic oil stored in the reservoir tank 40 flows through the second mechanical valve 52 or the first mechanical valve 51 to the second oil chamber 25 or the first oil chamber 24.

  Therefore, even if the electric motor 32 of the electric pump unit 30 does not operate, the hydraulic oil can be circulated appropriately. As a result, an increase in steering torque T required during manual operation can be prevented.

  As can be understood from the above description, according to the present embodiment, a member (for example, an electromagnetic valve) that is electrically operated to apply an appropriate assist force, except for the electric motor 32 of the electric pump unit 30. Can be eliminated. Thereby, power consumption can be reduced significantly, and fuel consumption can be improved with this reduction in power consumption. Further, the flow path control mechanism 50 can be mechanically operated using the hydraulic oil supplied to the power cylinder 20. For this reason, it is not necessary to use a complicated electric circuit for controlling the electrically operated electromagnetic valve, and the configuration of the power steering device itself can be simplified.

  Further, when the electric motor 32 of the electric pump unit 30 is stopped, for example, when the steering wheel 11 is held at the neutral position by the driver or when the electric pump unit 30 is stopped due to a failure, Since hydraulic oil is not pumped, the flow path control position of the pair of mechanical valves 51 and 52 is maintained at the communication permission position by the springs 51c and 52c. Therefore, particularly when the electric pump unit 30 is out of order, the first oil passage P1 and the second oil passage P2 and the reservoir tank 40 communicate with each other, in other words, each oil chamber 24 of the power cylinder 20. 25 and the reservoir tank 40 are maintained in communication with each other. As a result, hydraulic oil can be circulated between the oil chambers 24 and 25 of the power cylinder 20 and the reservoir tank 40. Therefore, even if the electric pump unit 30 is out of order, the driver can operate the steering wheel 11 to steer the steered wheels, although assistance by the power cylinder 20 cannot be obtained.

  Further, the electric pump unit 30 includes a check valve 62 with a spring having a spring 62a set to a biasing force larger than the biasing force of the springs 51c and 52c for biasing the flow path control position of the mechanical valves 51 and 52 to the communication permission position. And the flow path control mechanism 50 can be provided. As a result, the electric pump unit 30 starts pressure feeding of the hydraulic oil, and the differential pressure operation mechanism section is preferentially given before the pumped hydraulic oil flows from the first oil path P1 or the second oil path P2 to the reservoir tank 40. 53 can be operated, and as a result, the mechanical valves 51 and 52 can be quickly switched from the communication permission position to the communication prohibition position. As a result, hydraulic oil can be pumped to the oil chambers 24 and 25 of the power cylinder 20 with high responsiveness to the operation of the steering wheel 11 by the driver, and the steering torque T can be reduced. Therefore, the driver can obtain a good steering feeling.

  In the said embodiment, the flow-path control mechanism 50 was implemented so that it might comprise using the 1st mechanical valve 51, the 2nd mechanical valve 52, and the differential pressure | voltage action mechanism part 53 separately. In this case, the functions of the first mechanical valve 51, the second mechanical valve 52, and the differential pressure operation mechanism unit 53 can be integrated and implemented. Hereinafter, although this modified example is demonstrated, detailed description is abbreviate | omitted by attaching | subjecting the code | symbol corresponding to the flow-path control mechanism 50 of the said embodiment.

  As shown in FIG. 4, the flow path control mechanism 150 in this modification is provided in the first oil path P <b> 1 and the second oil path P <b> 2 and corresponds to the first mechanical valve 51 and the second mechanical valve 52. In order to switch between 151 and 152 and the cut valves 151 and 152, rods 153a, differential pressure pistons 153b and cylinders 153c corresponding to the rod 53a, differential pressure piston 53b and cylinder 53c are provided.

  The cut valves 151 and 152 have first ports 151a and 152a connected to the upstream side and second ports 151b and 152b connected to the downstream side, respectively. The cut valves 151 and 152 include valve portions 151d and 152d to which the urging force of the springs 151c and 152c is applied, and valve seats 151e and 152e, respectively.

  And about the flow-path control position in this cut valve 151,152, valve part 151d, 152d resists the urging | biasing force of spring 151c, 152c, and contact | abuts to valve seat 151e, 152e, 1st port 151a, 152a. It becomes a communication prohibition position which prohibits communication between the 2nd ports 151b and 152b. On the other hand, when the valve portions 151d and 152d are separated from the valve seats 151e and 152e by the urging force of the springs 151c and 152c, the communication permission for permitting communication between the first ports 151a and 152a and the second ports 151b and 152b. Position. The urging force of the springs 151c and 152c in this modification is also set smaller than the urging force of the spring 62a of the check valve 62 with the spring constituting the composite valve 60, similarly to the springs 51c and 52c in the above embodiment. Yes.

  Further, in the flow path control mechanism 150 in this modification, the valve portions 151d and 152d of the cut valves 151 and 152 are arranged at both ends of the rod 153a. In the flow path control mechanism 150 in this modification, the first pressure chambers 153d and 153e corresponding to the first pressure chambers 53d and 53e in the above embodiment are formed by the rod 153a, the differential pressure piston 153b, and the cylinder 153c. . The formed first pressure chamber 153d communicates with the second discharge oil passage 34 in the electric pump unit 30 via the first branch oil passage 154, and the formed second pressure chamber 153e has a second branch. The first discharge oil passage 33 in the electric pump unit 30 communicates with the first oil passage 155 via the oil passage 155.

  Also in the flow path control mechanism 150 configured as described above, the cut valves 151 and 152 are switched using the pressurized hydraulic oil for the power cylinder 20 to generate the assist force as in the above embodiment. It can be operated. That is, when the driver rotates the steering wheel 11 in the left-right direction, the electronic control unit 73 rotates the electric motor 32 of the electric pump unit 30 according to the rotation operation direction of the wheel 11. As a result, the hydraulic oil discharged from the oil pump 31 is controlled by the second discharge oil passage 34 and the first branch oil passage 154 or the first discharge oil passage 33 and the second branch oil passage 155. It flows into the first pressure chamber 153d or the second pressure chamber 153e of the mechanism 150.

  Then, when the hydraulic oil pressurized into the first pressure chamber 153d flows when the steering wheel 11 is turned leftward, the rod 153a and the differential pressure piston 153b move integrally in the cut valve 152 direction. Thus, the valve portion 152d abuts against the valve seat 152e against the urging force of the spring 152c. Further, when the hydraulic oil pressurized into the second pressure chamber 153e flows by turning the steering wheel 11 to the right, the rod 153a and the differential pressure piston 153b move integrally in the cut valve 151 direction. As a result, the valve portion 151d abuts against the valve seat 152e against the urging force of the spring 151c.

  Thereby, the flow path control position of the cut valve 151 or the cut valve 152 is switched to the communication prohibition position in accordance with the turning operation direction of the steering wheel 11, and the flow path control position of the other cut valve 152 or the cut valve 151 is changed. The communication permission position is maintained. Therefore, also in this modification, when the driver rotates the steering wheel 11 in the left-right direction, an appropriate assist force is applied, and the driver can easily rotate the steering wheel 11. it can.

  When the steering wheel 11 is maintained at the neutral position or when an operation abnormality occurs in the electric motor 32 of the electric pump unit 30, the flow path control positions of the cut valves 151 and 152 are the same as those in the above embodiment. Similarly, both are maintained at the communication permission position. Accordingly, when the vehicle travels straight while the steering wheel 11 is maintained at the neutral position, the pressure upstream of the combined valve 60 in the first oil passage P1 and the second oil passage P2 is adjusted by the check valve 62 with spring. The pressure is maintained at a predetermined pressure. Thereby, it is possible to exhibit excellent damping characteristics against disturbance input via the steered wheels.

  Further, even when an operation abnormality occurs in the electric motor 32 of the electric pump unit 30, the flow path control positions of the cut valves 151 and 152 are both maintained at the communication permission position as in the case of the above embodiment. Accordingly, when the pressure in the first oil chamber 24 or the second oil chamber 25 of the power cylinder 20 becomes equal to or higher than a predetermined pressure as the steering wheel 11 is turned, the first oil chamber 24 is moved by the spring-loaded check valve 62. Alternatively, the second oil chamber 25 and the reservoir tank 40 are in communication with each other. On the other hand, when the pressure in the second oil chamber 25 or the first oil chamber 24 decreases relatively, the check valve 61 causes the second oil chamber 25 or the first oil chamber 24 and the reservoir tank 40 to communicate with each other. Therefore, even when an operation abnormality occurs in the electric motor 32, the hydraulic oil can be reliably circulated, and an increase in the steering torque T during manual operation can be prevented.

  In carrying out the present invention, the present invention is not limited to the above-described embodiments and modifications, and various modifications can be made without departing from the object of the present invention.

  For example, in the above-described embodiments and modifications, the present invention is applied to a power steering apparatus having a steering mechanism that employs a rack and pinion system. However, any steering mechanism may be used as long as the steered wheels can be steered according to the turning operation of the steering wheel 11 by the driver.

1 is a schematic diagram schematically showing a power steering device according to an embodiment of the present invention. It is the schematic for demonstrating a state when a driver | operator rotates the steering wheel. It is the schematic for demonstrating a state when the electric pump unit is not act | operating. It is the schematic which showed a part in cross section in order to demonstrate the modification of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Steering wheel, 12 ... Steering shaft, 13 ... Pinion gear, 14 ... Rack bar, 20 ... Power cylinder, 21 ... Rod, 22 ... Cylinder, 23 ... Piston, 24 ... First oil chamber, 25 ... Second oil chamber 30 ... Electric pump unit, 31 ... Oil pump, 31a ... First discharge port, 31b ... Second discharge port, 32 ... Electric motor, 33 ... First discharge oil passage, 34 ... Second discharge oil passage, 40 ... Reservoir Tank, 50 ... flow path control mechanism, 51 ... first mechanical valve, 52 ... second mechanical valve, 51c, 52c ... spring, 53 ... differential pressure operation mechanism, 53a ... rod, 53b ... differential pressure piston, 53c ... cylinder 53d: first pressure chamber, 53e: second pressure chamber, 54: first branch oil passage, 55: second branch oil passage, 60: composite valve, 61: check valve, 62: spring Check valve, 62a ... spring, 70 ... electric control device, 71 ... steering angle sensor, 72 ... steering torque sensor, 73 ... electronic control unit, 74 ... drive circuit, 74a ... current detector, P1 ... first oil passage , P2 ... Second oil passage

Claims (3)

A steering mechanism connected to a steering shaft for transmitting a steering wheel operation by a driver, a power cylinder for assisting a steering force for steering a steered wheel connected to the steering mechanism, and each of the power cylinders An electric pump unit comprising a reversible oil pump having a pair of discharge ports for pumping hydraulic oil through a first oil passage or a second oil passage communicating with an oil chamber, and an electric motor for rotating the oil pump forward and backward A reservoir tank that can communicate with the first oil passage and the second oil passage, and a flow path control mechanism that permits or prohibits communication between the first oil passage, the second oil passage, and the reservoir tank. A power steering device comprising:
The flow path control mechanism is
A communication permission state provided between the first oil passage and the reservoir tank and between the second oil passage and the reservoir tank to permit the flow of hydraulic oil and a communication for prohibiting the flow of hydraulic oil. A pair of mechanical valves that can be switched to a prohibited state and maintain the communication permission state by an elastic member set to a predetermined urging force when the oil pump is stopped;
The discharge of the pair of mechanical valves when the oil pump is operated to pump hydraulic oil from one of the pair of discharge ports to the first oil path or the second oil path. A mechanical valve provided on the first oil passage side or the second oil passage side to which hydraulic oil is pumped from a port is used against the urging force of the elastic member using the pressure of the hydraulic oil pumped from the discharge port. A power steering device comprising: a differential pressure operation mechanism that switches from the communication permission state to the communication prohibition state. In the power steering device according to claim 1,
The differential pressure operation mechanism unit is
A rod capable of contacting the pair of mechanical valves;
A piston liquid-tightly fixed to the rod;
The rod and the piston are composed of a cylinder that accommodates the liquid-tight and slidably,
Introducing hydraulic oil pumped from one of the pair of discharge ports with the operation of the electric pump unit to one of the pressure chambers formed by the rod, piston and cylinder, A mechanical valve provided on the first oil passage side or the second oil passage side in which the hydraulic oil is pumped from the discharge port of the pair of mechanical valves by moving the piston due to the pressure difference caused by the pressure of the introduced hydraulic oil Is switched from the communication permission state to the communication prohibition state against the urging force of the elastic member. The power steering apparatus according to claim 1, further comprising:
Between the electric pump unit and the flow path control mechanism, the elastic member having an urging force set larger than an urging force of the elastic member that maintains the pair of mechanical valves in the communication permission state, A power steering device comprising a control valve for controlling the pressure of hydraulic oil in the first oil passage and the second oil passage to a predetermined pressure.

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