JPS62221972A - Rear-wheel steering gear - Google Patents

Abstract

PURPOSE:To improve the reliability of rear-wheel steering, by installing a directional control valve operating with pilot pressure sensitively responding to a car speed and a variable throttle valve. CONSTITUTION:Each of fixed throttles 41 and 42 is installed in each point midway in pressure oil lines 40a and 40b as a steering mechanism 20 for rear wheels, while a variable throttle valve 44 in parallel with a directional control valve 28 is installed in a bypass line 43 connecting these pressure oil lines 40a and 40b. These valves 28 and 44 are connected to a car speed sensitive type pilot hydraulic pump 45 via pilot circuits 29a and 29b. And, the directional control valve 28 is selected by this hydraulic pump 44, and these rear wheels are steered to the same phase or the opposite phase while controlling flow of the line 43 with the variable throttle 44.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rear wheel steering device used in a four-wheel steering system of a vehicle.

[Conventional technology]

In recent years, in order to improve the steering stability of four-wheeled vehicles when driving at high speeds and the maneuverability when driving at low speeds,
Four-wheel steering vehicles are coming into practical use.

As an example, there is a configuration as shown in FIG.

In other words, on the front wheel Tf side of a four-wheeled vehicle → double ^1#LI
J + Shihe, 1 person ~ I Neya, - Bolt - It has a steering mechanism 1, and has a steering mechanism 2 on the rear wheel Tr side,
This steering mechanism 2 includes a power cylinder 2G connected to an axle Ar of a rear wheel Tr, a controller 2b into which a detection signal from a steering wheel operation in the power steering mechanism 1 is input together with other detection signals such as vehicle speed, and a controller 2b. It is comprised of a direction switching solenoid valve 2C that is switched by a signal from the controller 2b to supply pressure oil to either of the power cylinders 2α.

In such a conventional four-wheel steering vehicle, the direction of supply of pressure oil to the power cylinder 2α is switched by an output signal from the controller 2b, which receives a signal as the front wheel Tf is steered, so that the rear wheel Tr is steered to the desired position. It will be steered in the direction.

However, in the above-mentioned conventional system, switching of the direction of the pressure oil supplied to the power cylinder 2α is performed exclusively by the controller 2.
Since it is said to be based on the output signal from h, the rear wheel T
In order to steer the r, it is necessary to equip various sensors and maintain a controller that processes and outputs input signals from these various sensors, which leads to an increase in the number of parts and the complexity of the entire device. This increase in the number of parts and the complexity of the entire device result in higher costs.

Moreover, there is a problem that the durability tends to be deteriorated.

Therefore, recently, in an attempt to resolve this inconvenience,
A four-wheel steering system having a configuration as shown in the figure has been devised. In this system, the steering mechanism 20 for the rear wheels Tr includes a rear wheel axle A
r, a pressure oil supply pump 22 that supplies pressure oil to the power cylinder 21, and a pressure oil line from the pressure oil supply pump 22 to the power cylinder on the rear wheel side. 21 pressure chamber 21α or 21b
and a directional solenoid valve 23 for supplying pressure oil to the
In the middle of the line that supplies pressure oil from the pressure oil supply pump 22 to the power cylinder 21 on the rear wheel side, the power cylinder 1 in the power steering mechanism 10 on the front wheel Tf side
A hydraulic pilot flow control valve 24 is provided which controls the flow rate of the pressure oil supplied to the power cylinder on the rear wheel Tr side. In the figure.

12 is a rack provided on the axle Af of the front wheel Tf; 13 is a power steering control valve that supplies pressure oil from the engine speed-dependent pressure oil supply pump 14 to the pressure chamber 11α or 11b of the power cylinder 11;

15 is a handle; 16 is a pinion that is engaged with the rack 12 and rotates when the handle 15 is operated to move the axle 47 leftward or rightward to change the direction of the front wheel f; Pressure chamber 21α of wheel side power cylinder 21
, 21h have built-in reaction springs, and 26 is a flow rate control solenoid valve that controls the discharge flow rate from the pressure oil supply pump 22.

27 is vehicle speed, steering angle, and power steering output.

This is a controller that inputs signals to the direction switching solenoid valve 23 and the flow rate control device 26 based on the engine rotation speed and the like.

Shima hyl of the recently proposed four-wheel steering system mentioned above.
a = anchorage The direction of the curved throttle W and the direction of the chair μ or V is operated based on the command from the controller 27, and the steering direction of the rear wheels relative to the front wheels is in the opposite phase at low speeds, and in the same phase at high speeds. By using the internal pressure generated inside the power cylinder 11 in the front wheel power steering mechanism as pilot pressure, a desired amount of pressure oil can be supplied into the power cylinder 21 in the rear wheel steering mechanism according to the steering direction of the front wheels. Therefore, there is an advantage that the increase/decrease in the amount of steering of the rear wheels can be made to follow the increase/decrease in the amount of steering of the front wheels without using a controller, and the drawbacks of the conventional method shown in FIG.

[Problem that the invention seeks to solve]

However, even with the recently proposed rear wheel steering system shown in FIG. The cost and complexity of the equipment increases. Furthermore, since the steering direction of the rear wheels is changed by the direction switching solenoid valve 23, the direction cannot be changed in response to oil pressure depending on the vehicle speed, and therefore the direction cannot be changed reliably depending on the vehicle speed, making it unreliable. There may be some drawbacks to this.

Therefore, the present invention aims to improve the certainty and reliability of operation by operating the rear wheel directional control valve etc. with a pilot pressure sensitive to vehicle speed, and furthermore, it is possible to reduce costs by omitting control parts. It is an object of the present invention to provide a rear wheel steering device for a four-wheel steering vehicle.

[Means for solving problems]

In order to achieve the above object, the present invention provides a rear wheel steering device in which pressure oil supplied to the power cylinder of the front wheel power steering mechanism is supplied to the rear wheel power cylinder via a directional control valve. In the middle of the line connecting the front wheel side power cylinder and the rear wheel side power cylinder, there is a variable throttle valve that controls the flow rate, and the rear wheel side power cylinder is switched so that the steering direction of the rear wheels with respect to the front wheels is in the same phase or in the opposite phase. A directional switching valve is provided in parallel, and a pressure on the pump discharge side corresponding to the heavy speed acts as a pilot pressure on these variable throttle valves and directional switching so that switching can be performed.

[For production]

At low speeds, the directional control valve uses the force of a built-in spring to guide hydraulic oil to the power cylinder on the rear wheel side so that the rear wheels are in opposite phase to the front wheels.At medium and high speeds, the directional control valve is switched by pilot pressure to direct the front wheels to the power cylinder. Pressure oil is guided to the power cylinder on the rear wheel side so that the rear wheels are in the same phase.

〔Example〕

Hereinafter, the present invention will be described in detail based on the drawings.

FIG. 1 shows an embodiment of the present invention, in which a hydraulically operated directional valve 28 is used in place of the directional solenoid valve 23 in FIG. 10 in a configuration similar to that shown in FIG. 10. ing. Further, as the rear wheel steering mechanism 20, fixed throttles 41 and 42 are provided in the middle of each of the pressure oil lines 40α and 40b, and a variable throttle in parallel with the directional control valve 28 is provided on the bypass line 43 connecting the pressure oil lines 40α and 40b. Valve 44
has been established. These direction switching 3P28 and variable throttle valve 44 are connected to a vehicle speed sensitive pilot hydraulic pump 45 via pilot circuits 29α and 29b. The hydraulic pump 45 is relied on to switch the direction switching valve 28, and while controlling the flow rate of the line 43 with the variable throttle 44, the rear wheels Tr are steered in the same phase or in the opposite phase with respect to the front wheels Tf according to the steering angle of the front wheels. Make it.

As shown in detail in FIG. 2, the direction switching 5P28 has a spool 31 built into the axial center of the housing 30 so as to be movable in the axial direction, and is interposed between the inside of the housing 30 and the end of the spool 31. The spool 31 is pushed toward one end of the housing 30 by the elasticity of the spring 32, and at this time, the flow path 33.
Among the channels 34, 35, and 36, the channels 33, 35%, and 36 are selectively communicated with the channel 31cL of the spool 3, and a cap 3 is provided at one end of the housing 30.
7 is provided, and the pilot pressure from the pilot line 29α is applied to the spool 31 through the through hole 37α of the cap 37.
It is designed to act on one end face of the. By the way, if the pilot pressure is low at low speed, the spring 32 will cause the spool 31 to
is pushed to the right, pressure oil is supplied from the flow path 34, 36 to the left pressure chamber 21α of the power cylinder 21, and when the pilot pressure increases at high speed, this pilot pressure causes the spool 31 to
is moved to the left in the figure against the spring 32, and pressure oil is supplied to the right pressure chamber 21b of the power cylinder 21 via the passage 33, 35 of the spool 31.

In FIG. 1, the same parts as in FIG. 10 are given the same reference numerals.

Pilot pressure acts on the directional switching valve 28 and the variable throttle valve 44 at the same time to switch them. That is,
A hydraulic pump 45 that is driven by a gear or belt as the propeller shaft or drive shaft rotates and discharges water depending on the vehicle speed, and a throttle 47 installed between the pump discharge part and the tank 46 to a rear wheel switching valve 48. The flow rate discharged from the pump 45 depending on the actual speed is returned to the tank 46 via a throttle 47, and the pressure on the upstream side of this throttle 47 is used as a pilot pressure to be connected to pilot lines 29α, 29h. Through directional control valve 2
8 and the variable throttle valve 44, the rear wheel side power cylinder 2 is actuated to move the rear wheels in opposite phases to the front wheels at low speeds, and to move the rear wheels in the same phase as the front wheels at medium and high speeds.
1 is operated by controlling the flow rate with a variable throttle valve 44 and then switching the flow path.

Since the hydraulic pump 45 discharges pressure oil depending on the vehicle speed, the vehicle speed and pump discharge amount are 1. As shown in diagram f5, there is a proportional relationship, and as the vehicle speed increases, the pump discharge amount also increases. Since the discharge flow rate of this pump 45 passes through the throttle 47 and returns to the tank 46, the pilot pressure generated upstream of the throttle 47 increases as the vehicle speed increases (low speed range → medium speed range → high speed range). It increases as shown. This pilot pressure is applied to the variable throttle valve 44 and the spool 31 of the direction switching 3P28.
Since the pilot pressure is small in the low speed range, the directional control valve 28 is pushed to the right by the spring 32. However, as the vehicle speed increases to the middle speed range or higher (speed 01 or higher), the pilot pressure decreases. is raised and acts on the directional switching valve 28, so the directional switching valve 28 is switched by moving the spool 31 to the left in the figure, and the movement of the power cylinder 21 is reversed.

On the other hand, the variable throttle valve 44 bypasses the pressure oil from the high pressure line to the low pressure line, but when the pilot pressure increases according to the vehicle speed, the variable throttle valve 44 throttles the bypass according to that pressure.
High-pressure oil flows more toward the power cylinder 21 side, and the higher the speed, the more the rear wheels will cut.

Therefore, as shown in the off-line diagram, the vehicle speed and the rear wheel shear amount are in opposite phases in the low speed range, but in the middle and high speed ranges they are in phase, and the shear signal increases proportionally.

Further, the bypass adjustment flow rate passing through the variable throttle valve 44 at this time is shown in FIG. 8 Cα), and the supply amount supplied to the rear wheel side power cylinder 21 is similarly shown in FIG. 8(b).

FIG. 3 shows an embodiment of the variable throttle valve 44, which is composed of a housing 50, a spool 51 movably inserted into the housing 50, and a spring 51.
It has ports 52 and 53 that communicate with α, ports 54 and 55 that communicate with line 40A, and port 56 that communicates with pilot circuit 29b. A passage 57 is formed in the center of the spool 51, and this passage 57 is connected to the port 52.5.
4 or ports 53 and 55 depending on the pilot pressure, and the flow rate is controlled by the spool 510 land.

Similarly, FIG. 4 shows another embodiment of the variable throttle valve 44. This has a housing 58, a plunger type spool 59, and a spring 62, and a port 60 that opens to the line 40α and a port 6 that opens to the line 40A.
1 and a port 63 that opens to the pilot circuit 294.

A chamber 65 is provided in the housing 58, and a partition member 64 in which an aperture hole 65 is formed is provided in the chamber 65.
A port 60.61 communicates with the through hole 65.

Notches 67 and 68 are formed on the outer periphery of the spool 59,
When the spool 59 is moved by the pilot pressure against the spring 62 and inserted into the through hole 65, the through hole 65 is narrowed.
The flow rate corresponds to the area of the notches 67 and 68.

It goes without saying that as the pilot pressure, pressure oil from the pressure oil supply pump 14, which depends on the engine speed, may be applied to the direction switching 5P28 and the variable throttle valve 44.

〔Effect of the invention〕

As described above, the rear wheel steering device of the present invention incorporates a directional control valve and a variable throttle valve operated by pilot pressure responsive to vehicle speed for switching the rear wheels. This can be done reliably depending on the steering angle corresponding to the vehicle speed and the actual vehicle speed, improving reliability.
This eliminates the need for control parts such as proportional solenoids and controllers, thereby achieving excellent effects such as cost reduction and a simplified structure.

[Brief explanation of drawings]

Fig. 1 is a schematic plan view of a four-wheel steering vehicle showing an embodiment of the rear wheel steering device of the present invention, and Fig. 2 is a sectional view showing details of the rear wheel steering device of the present invention. Figures 1, 83, and 4 are cross-sectional views of examples of variable throttle valves, Figure 5 is a graph showing the relationship between pump discharge amount and vehicle speed, and Figure 6 is a graph showing the relationship between pilot pressure and vehicle speed. Graph, Yoshi 7
The figure shows the relationship between the amount of rear wheel breakage and vehicle speed, Figure 8 (α) shows the relationship between bypass flow rate and vehicle speed, and Figure 8 (b) also shows the relationship between supply flow rate and vehicle speed. FIG. 9 is a schematic plan view showing a conventional four-wheel steering system, and FIG. 10 is a schematic plan view of a four-wheel steering system that has been recently considered. 10... Front wheel side power steering mechanism, 11...
Power cylinder, 14...Pressure oil supply pump, 20...
・Rear wheel steering mechanism, 21...power cylinder, 28・
... Directional switching valve, 29α. 29b... Pilot line, 44... Variable throttle valve, 45... Hydraulic pump, 47... Throttle, 48...
... Rear wheel switching section. Fig. 1 Fig. 2 Pump rotation speed Fig. 7, Fig. 8 (Q) Fig. 8 (b) ■1 Wheel Fig. 10 Procedure amendment (rl. June 1985/λ mouth Commissioner of the Patent Office Black) (092) Kayaba Chogyo Co., Ltd. 4, Agent's address Yaesu 2-chome, Chuo-ku, Tokyo [110-8 Yatun Building (271) 7854-5 (1) Detailed explanation of the invention of the detailed reading As per the attached sheet ・4'' Shimabetsu Paper (1) Detailed reading In the 14th line of page 10, correct "valve 44" to "valve 44."
"On the right side of the figure," in line 7, "on the left side of the figure," should be corrected to "human power in the figure," and in line 20, "same," should be corrected to "results." (3) Specifications - Page 13, line 2 says, "It will be shown." [It will be shown.] ] Correct. (4) From line 1 to line 2 of page 14 of the Ming Dynasty: “This room 65
'' is corrected to ``this room 66'', and the 5th and 8th lines respectively read ``notch 67, 6B'' and ``tsukuchiro 7''. (5) Regarding page 156, C is shown in Figures 1 and 3 as shown in the attached sheet.
Figures and 4 (Correct each of 4. Figure 4 Figure 1

Claims (4)

[Claims] (1) In the middle of the line that supplies pressure oil to the power cylinder of the front wheel side power steering mechanism to the rear wheel side power cylinder, a switching operation is performed to steer the rear wheels in the same phase or in the opposite phase with respect to the front wheels. In a rear wheel steering system equipped with a directional switching valve, a variable throttle valve is installed in parallel with the directional switching valve in the middle of the above line, and the pump discharge side pressure is applied to these directional switching valves and the variable throttle valve according to the vehicle speed. A rear wheel steering device characterized in that each actuates as a pilot pressure. (2) The rear wheel steering device according to claim 1, wherein pressure on the high pressure side of the front wheel side power steering mechanism is used as the pilot pressure. (3) The rear wheel steering system according to claim 1, wherein the pilot pressure is the pressure on the discharge side of the pump, which is discharged depending on the actual vehicle speed due to rotation of the drive shaft and propeller shaft. (4) Claim 3: A throttle is provided in the circuit to the tank of the oil pump that discharges oil depending on the vehicle speed as the propeller shaft or drive shaft rotates, and the upstream pressure of the throttle acts as pilot pressure. Rear wheel steering device as described in section.