JP2009262885A - Hydraulic power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic power steering device capable of preventing itself from being into a vibration mode of a snaking phenomenon. <P>SOLUTION: This hydraulic power steering device has a hydraulic cylinder 23, which has two cylinder chambers 23b and 23c and assists steering force of a steering wheel for steering front wheels of a vehicle, and a rotary valve 27 for controlling supply/discharge of oil to/from the two cylinder chambers 23b and 23c. Piping L connecting between the cylinder chamber 23b and the rotary valve 27 is provided with a flow rate variable valve 24 capable of limiting a flow rate of the oil passing therethrough. During the time when the vehicle tows a towed vehicle, a flow rate of the oil passing through the flow rate variable valve 24 is adjusted to restrict movement of the hydraulic cylinder 23. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to hydraulic power steering, and particularly to a vehicle that pulls a towed vehicle.

  As shown in FIG. 3, when a lane change is performed while the tractor 51 (towing vehicle) is running while towing a trailer 52 (towed vehicle), the trailer 52 is swung left and right, and depending on conditions, A phenomenon called a snakeing phenomenon occurs in which vibration is difficult to attenuate. The vibration in the snake phenomenon becomes more severe as the vehicle speed increases. Further, in the snaked state, the vehicle body is shaken and the steering is also shaken, as can be seen from the change in the steering angle in FIG. 4A and the change in the yaw rate in FIG. 4 (a) and 4 (b) are actual measurements in which the steering is in a free state after an impulse-like steering input at a vehicle speed of 100 km / h.

JP 2006-111179 A

  In Patent Document 1, it is determined whether or not the pendulum vibration is generated by the snakeing phenomenon by detecting the traveling direction of the tow vehicle, the vehicle speed, and the yaw rate, and it is determined that the pendulum vibration is generated by the snakeing phenomenon. In this case, when the yaw rate is small, a load is applied to the steering operation, and when the yaw rate is large, the towing vehicle is braked to control vibration due to the snake phenomenon.

  However, in reality, it is difficult to determine whether or not the snake phenomenon has occurred, the response control is delayed, and there is a possibility of falling into the vibration mode.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a hydraulic power steering that suppresses falling into a vibration mode of a snake phenomenon.

The hydraulic power steering according to the first invention for solving the above-mentioned problems is as follows.
A hydraulic cylinder having two cylinder chambers and assisting a steering force of a steering wheel for steering a front wheel of the vehicle;
A control valve for controlling supply and discharge of oil to and from the two cylinder chambers;
At least one of two pipes connecting between the two cylinder chambers and the control valve is provided with a flow rate control means for controlling the flow rate of oil passing therethrough,
When the vehicle is towing the towed vehicle, the flow rate of oil passing through the flow rate control means is adjusted to suppress the movement of the hydraulic cylinder.

  According to the present invention, the flow rate control means is provided in the pipe between the hydraulic cylinder and the control valve of the hydraulic power steering, and when the towed vehicle is towed, the flow rate of the oil passing through the flow rate control means is adjusted. When towing a towed vehicle, the hydraulic power steering increases damping and suppresses the movement of the hydraulic cylinder, making it difficult for the driver to steer suddenly. Even if it occurs, the vibration mode can be suppressed to improve the sense of security of steering.

  Hereinafter, a hydraulic power steering according to the present invention will be described in detail with reference to the drawings.

  First, a vehicle using the hydraulic power steering according to the present embodiment will be described with reference to a schematic configuration diagram shown in FIG.

  The tractor 1 (vehicle) is capable of towing a trailer (towed vehicle) using a hitch ball (towing tool). The tractor 1 is provided with a handle 11 for steering the front wheel 14 of the tractor 1, and this handle 11 is connected to a hydraulic power steering 13 via a steering shaft 11a. Accordingly, the steering force applied to the handle 11 is assisted by the hydraulic power steering 13 and transmitted to the front wheels 14.

  In the tractor 1, the steering shaft 11 a is provided with a steering angle sensor 12 that detects the steering angle of the handle 11. The front wheel 14 is provided with a wheel speed sensor 15 that detects a wheel speed proportional to the vehicle speed. A yaw rate sensor 20 that detects the yaw rate of the tractor 1 is provided at the center of the tractor 1. In the hitch ball, the trailer is connected to the brake harness, and the trailer towing is detected based on the presence or absence (towing detection means). The hydraulic power steering 13 is controlled by an ECU (Electronics Control Unit; control means) (not shown) based on the detected values by the steering angle sensor 12, the wheel speed sensor 15, the yaw rate sensor 20, the traction detection means, and the like. Yes. As the traction detection means, for example, the traction of the trailer may be detected by the ECU based on the weight gradient before and after the shift up in the transmission of the tractor 1, the resistance deviation, and the like.

  In the tractor 1, the front wheel 14 and the rear wheel 18 are connected via a propeller shaft 16 and an electric control coupling 17 to form a so-called 4WD (4 Wheels Drive). An actuator 19 for performing the above steering is also provided, which is a so-called 4WS (4 Wheels Steering) configuration. These are also controlled by the ECU.

  Note that the tractor 1 shown in FIG. 1 is one example of application, and the configuration of 4WD and 4WS is not necessarily required in the present invention.

  Next, with reference to FIG. 1 as well, a description will be given using the schematic diagram of FIG. 2 showing an example of the hydraulic power steering according to the present embodiment.

  The hydraulic power steering 13 according to the present embodiment is provided in the tractor 1 that can pull the trailer. The hydraulic power steering 13 includes a reserve tank 25 that stores oil recovered via a pipe T, an oil pump 26 that pressurizes and supplies oil stored in the reserve tank 25 via a pipe P, and a handle. 11, a rotary valve 27 (control valve) for supplying and discharging oil supplied from the oil pump 26 to and from the power cylinder 23 in accordance with the direction and magnitude of the steering force applied to the cylinder 11, and cylinder chambers 23b on both sides of the piston 23a , 23c, and a double-acting power cylinder 23. Further, the flow rate of oil passing through at least one of the pipes L, R connecting the power cylinder 23 and the rotary valve 27 is controlled. A flow rate variable valve 24 (flow rate control means) is provided. In addition, as the flow variable valve 24, for example, a solenoid valve including a solenoid, a spring, a movable iron core, or the like is applicable.

  The rotary valve 27 is a rotary control valve that utilizes the rotation of the steering shaft 11 a that transmits the operation of the handle 11. Specifically, the rotary valve 27 is divided into an input shaft (not shown) connected to the steering shaft 11a side and an output shaft 29 connected to the rack shaft 21 side, and is coaxially connected via a torsion bar 28. This is a structure in which an input shaft (inner valve) 27b integrally formed with the other connecting end is fitted inside a cylindrical outer valve 27a engaged with one connecting end so as to be relatively rotatable.

  Further, the output shaft 29 is provided with a pinion gear 22, arranged so as to intersect with the rack shaft 21 connected to the piston 23 a, and configured so that the pinion gear 22 and the rack gear 21 a of the rack shaft 21 mesh with each other. Has been. Therefore, when the steering wheel 11 is steered, the steering force is transmitted to the output shaft 29 and the pinion gear 22 via the torsion bar 28, and the rack shaft 21 is moved in the axial direction as the pinion gear 22 rotates. At the same time, the steering force is assisted by the power cylinder 23, and the front wheel 14 is steered via the tie rod 30 provided at the end of the rack shaft 21.

  In the rotary valve 27, a plurality of axially extending grooves are provided in the circumferential direction on the inner peripheral side of the outer valve 27a and the outer peripheral side of the inner valve 27b, and the plurality of grooves of the outer valve 27a are provided in the circumferential direction. The cylinder chamber 23b or the cylinder chamber 23c is alternately communicated, and the plurality of grooves of the inner valve 27b are alternately communicated with the pipe P or the pipe T in the circumferential direction. That is, in the outer valve 27a, grooves (hereinafter referred to as LH grooves) communicating with the cylinder chamber 23b and grooves (hereinafter referred to as RH grooves) communicating with the cylinder chamber 23c are alternately arranged in the circumferential direction. In the inner valve 27b, grooves communicating with the pipe P (hereinafter referred to as supply grooves) and grooves communicating with the pipe T (hereinafter referred to as recovery grooves) are alternately arranged in the circumferential direction.

  Then, in the rotary valve 27, when a steering force is applied to the steering shaft 11a, it communicates with any one groove of the outer valve 27a from the groove of the adjacent inner valve 27b in accordance with the direction of the steering force. One groove to be selected is selected, oil is supplied to one of the cylinder chamber 23b and the cylinder chamber 23c, and the oil is recovered from either one. When a steering force is applied to the steering shaft 11a, a relative angular displacement is generated between the outer valve 27a and the inner valve 27b as the torsion bar 28 is twisted, and communication is performed according to the relative angular displacement. In the throttle portion between the groove of the outer valve 27a and the groove of the inner valve 27b, the throttle area is changed, and the flow rate of the passing oil is controlled.

  For example, in a neutral state in which no steering force is applied to the handle 11 and the torsion bar 28 is not twisted, the grooves of the adjacent inner valve 27b are simultaneously formed with respect to any one groove of the outer valve 27a. Communicate. For this reason, the oil supplied to the rotary valve 27 is supplied to the supply groove of the inner valve 27b and then flows into the recovery groove of the inner valve 27b through the groove of the outer valve 27a communicating with the oil. It passes through and is collected in the reserve tank 25. As a result, no pressure difference is generated between the cylinder chamber 23b and the cylinder chamber 23c communicating with each groove of the outer valve 27a, and the power cylinder 23 does not generate any force.

  On the other hand, when a steering force is applied to the handle 11, a relative angular displacement occurs between the outer valve 27a and the inner valve 27b as the torsion bar 28 is twisted, so that any one groove of the outer valve 27a is displaced. Thus, one groove communicating from the grooves of the adjacent inner valve 27b is selected, and the throttle area of the throttle portion between the groove of the outer valve 27a communicating with the groove of the inner valve 27b changes.

  For example, in FIG. 2, the supply groove of the inner valve 27b is selected for the LH groove of the outer valve 27a, and the recovery groove of the inner valve 27b is selected for the RH groove of the outer valve 27a. At this time, the oil supplied to the rotary valve 27 is supplied to the supply groove of the inner valve 27b, and then introduced to the LH groove of the outer valve 27a through the throttle portion on the side where the throttle area has been increased. It passes through the variable flow valve 24 and is supplied to the cylinder chamber 23b. On the other hand, the recovery groove of the inner valve 27b that communicates with the pipe T communicates with the RH groove of the outer valve 27a that communicates with the pipe R, so that the oil in the cylinder chamber 23c flows into the RH groove of the pipe R and the outer valve 27a. The recovery groove 25 of the inner valve 27b and the pipe T are sequentially passed back to the reserve tank 25. As a result, a pressure difference is generated between the cylinder chamber 23b and the cylinder chamber 23c, and this pressure difference is applied to the rack shaft 21 connected to the piston 23a to assist the steering force.

  In this embodiment, the flow rate variable valve 24 is provided in at least one of the pipes L, R connecting the power cylinder 23 and the rotary valve 27 (pipe L in FIG. 2). When it is detected that the trailer is being pulled, a control signal is applied from the ECU to the flow variable valve 24, and the valve opening degree of the flow variable valve 24 is electrically controlled to control the oil passing through the variable flow valve 24. The flow rate is adjusted. Thus, the hydraulic power steering 13 increases damping, suppresses the movement of the power cylinder 23 (steering system), and increases the operating resistance of the rack shaft 21. On the other hand, when the ECU does not detect the trailer towing, the flow rate variable valve 24 is not operated or the valve opening degree is made larger than when the trailer is towing, and the oil is allowed to pass therethrough.

  Thus, in the hydraulic power steering 13, the flow rate variable valve 24 is provided in at least one of the pipes L, R between the power cylinder 23 and the rotary valve 27, and when the trailer is pulled, the flow rate variable valve 24 is used. Since the flow rate of the oil passing through is adjusted, when the trailer is towed, the hydraulic power steering 13 increases damping and suppresses the movement of the power cylinder 23 (steering system). For this reason, it becomes difficult for the driver to steer suddenly, so that it does not fall into the snake phenomenon, and even if the snake phenomenon occurs beyond the control limit by the rear wheel steering device, the vibration is attenuated, The change in the behavior can be made as gentle as possible. As a result, the driving stability can be improved and the sense of security of steering can be improved. On the other hand, when the trailer is not towed, the flow rate of the oil passing through the flow rate variable valve 24 is not restricted. Therefore, when the trailer is not towed, the stability can be improved without giving a sense of incongruity to steering.

  The hydraulic power steering according to the present invention is suitable for towing a towed vehicle such as a trailer.

1 is a schematic configuration diagram showing a vehicle in which a hydraulic power steering according to the present invention is used. It is a schematic diagram which shows an example of the hydraulic power steering which concerns on this invention. It is a figure explaining a snakeing phenomenon. (A) is a graph of the actual measurement value of the steering angle in the snaked state, and (b) is a graph of the actual value of the yaw rate in the snaked state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 13 Hydraulic power steering 21 Rack shaft 21a Rack gear 22 Pinion gear 23 Power cylinder 23a Piston 23b, 23c Cylinder chamber 24 Flow variable valve 25 Reserve tank 26 Oil pump 27 Rotary valve 28 Torsion bar 29 Output shaft

Claims (1)

A hydraulic cylinder having two cylinder chambers and assisting a steering force of a steering wheel for steering a front wheel of the vehicle;
A control valve for controlling supply and discharge of oil to and from the two cylinder chambers;
At least one of two pipes connecting between the two cylinder chambers and the control valve is provided with a flow rate control means for controlling the flow rate of oil passing therethrough,
A hydraulic power steering characterized in that when the vehicle is towing a towed vehicle, the flow rate of oil passing through the flow rate control means is adjusted to suppress the movement of the hydraulic cylinder.

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