JPS61238568A - Vehicle power steering device provided with variable displacement type pump - Google Patents

Abstract

PURPOSE:To make the power loss of a vehicle power steering device substantially zero during steering operation, by utilizing all pressure fluid discharged from a pump as an assist operation effected by a power cylinder. CONSTITUTION:A power steering device has a steering mechanism 10 and an electrical hydraulic pressure generating mechanism P coupled to a rotary motor M. Further, the steering mechanism 10 moves a rack bar through a pinion 12a in association with the rotary motion of the pinion 12a. An electrical hydraulic generating mechanism P is composed of a variable displacement type oil pump 30, a pilot valve 40 and a linear actuator 50 which are incorporated in a housing. The oil pump 30 has a ball bearing 32 disposed in a housing section 21, and control piston mechanisms 38, 29 are provided to the outer race of the ball bearing 32. Therefore, the ball bearing is deflected under the control of the piston mechanisms so that the discharge volume of the oil pump is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a power steering device for a vehicle, and more particularly to a power steering device for a vehicle equipped with a variable displacement pump.

[Prior art]

Conventionally, this type of power steering device employs, for example, a variable displacement oil pump, a constant differential pressure actuator, and a variable throttle valve, and the constant differential pressure actuator controls the differential pressure between upstream and downstream of the variable throttle valve. The variable capacity of the oil pump is controlled so that the amount of pressure oil supplied from the oil pump via the variable throttle valve to the servo valve assembled to the steering shaft of the steering wheel is constant. Some devices are designed to reduce power loss.

[Problem that the invention seeks to solve]

However, in such a configuration, the above-mentioned servo valve partially supplies the pressure oil from the variable throttle valve to the power cylinder according to the rotational force on the steering wheel, and discharges the remaining pressure oil to the reservoir. Therefore, the entire amount of pressure oil discharged from the oil pump is not used by the power cylinder to assist the operation of the steering wheel, resulting in a problem of power loss.

The present invention has been made to address these problems.
In a power steering system for a vehicle equipped with a variable displacement pump, the entire pressure fluid discharged from the pump is used for assisting action by a power cylinder.

[Means for solving the problem] In order to solve the problem, the present invention has a structure that includes a steering mechanism that transmits rotation of a steering shaft of a vehicle to a piston shaft of a power cylinder to steer a steering wheel, and a prime mover. a variable displacement pump that is driven by a variable displacement pump that generates pressure fluid in an amount corresponding to a variable displacement and supplies it to one of both chambers of the power cylinder; a switching means for selectively switching the supply of pressure fluid to both chambers so that the power cylinder assists the operation of the steering mechanism; a capacity control means for controlling the variable capacity of the pump to maintain the variable capacity at a maximum capacity value and to decrease the variable capacity in response to a rise in the pressure of the pressure fluid to the predetermined pressure value or above; detection means for detecting steering torque generated in the steering mechanism in response to rotation and generating it as a torque signal; an output signal generating means for determining the applied pressure value according to the l·lux signal from a predetermined relationship determined to increase (or lower) the applied pressure value and generate it as an output signal; The present invention further includes an application permitting means for permitting application of the pressure fluid from the pump to the capacity control means.

[Effect]

By configuring the present invention in this manner, the output signal generating means, in cooperation with the detecting means, determines the pressure value of the pressure fluid applied from the pump to the displacement controlling means in accordance with the steering torque. is generated as an output signal, and the capacity control means generates pressure fluid at the maximum capacity value under the drive of the prime mover in cooperation with the application permitting means in response to the output signal. The variable capacity of the pump is reduced to reduce the amount of pressure fluid generated, and the pressure fluid is directed in the direction of rotation of the steering shaft with an amount corresponding to the maximum capacity value of the variable capacity or its reduced capacity value. Under the switching control of the responsive switching means, pressure fluid is supplied to one of the two chambers of the power cylinder so as to assist the operation of the steering mechanism at a degree corresponding to the amount of the pressure fluid. The maximum capacity value of the pump, that is, the amount of pressure fluid generated starts to decrease earlier when the steering torque is large and later when it is small;
Almost all of the pressure fluid generated from the pump is supplied to the power cylinder via the switching means in an amount necessary and sufficient for assisting the power cylinder.

As a result, it is possible to reduce the power loss during steering of this type of power steering device to almost zero, while ensuring an appropriate steering feel that matches the change in the steering torque.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.
The figure shows a power steering device for a vehicle according to the present invention. This power steering device includes a steering mechanism 10 and an electric hydraulic pressure generation mechanism P connected to a rotary electric motor M.
0 indicates that the pinion 12a at the tip of the steering shaft 12 is rotated to the left due to the leftward (or rightward) rotation of the steering shaft 12 in conjunction with the leftward (or rightward) rotation of the steering handle 11. Rack bar 13 through rotation in the direction (or right direction)
is pivoted to the left (or right) to steer the steering wheel 14 to the left (or right) via a tie opening/nod (not shown).

As shown in FIGS. 2 and 3, the electric oil pressure generating mechanism P includes a variable displacement oil pump 30,
As shown in FIG. 24~
24, the bottle 2 is assembled on the other side of the housing section 21 through both oil seals 25a and 25b.
6 are assembled by tightening with a plurality of screws 27.

The oil pump 30 has an input shaft 31 which is rotatably supported in the annular boss 23a of the end bracket 23 via the sleeve ring 2B and coaxially with the inner end host 26a of the bottle 26. The shaft 31 is connected to the output shaft of the rotary electric motor M at its outer end 31a. Moreover, this oil pump 30 has a housing sexidine 2.
A ball bearing 32 is rotatably fitted into the large diameter inner hole 21a of the bottle 1, and an annular bush 3 is attached to the inner end boss 26a of the bottles 1 to 26 within the hollow part of the ball hair ring 32.
It has an annular rotor 34 which is rotatably supported through a rotor 3, and the inner diameter of the large diameter inner hole 21a is based on the center of the inner end boss 26a of the bottle 26 (indicated by the symbol 0 in FIG. 3). As shown in Fig. 3, the ball bearing 32
The center (indicated by reference numeral 01 in FIG. 3) is set to be eccentric. In such a case, the ball bearing 32
The eccentricity e is designed to be maximum in the state shown in FIG. Note that the bushing 33 is press-fitted into the inner peripheral surface of the hollow portion of the rotor 34. Further, in FIG. 2, reference numeral 29 does not indicate an oil seal.

The rotor 34 has a plurality of protrusions 34 as shown in FIG.
A is connected to the inner end 31b of the input shaft 31 so as to rotate integrally with the input shaft 31, and each plunger 35 (cross section U (consisting of letter shapes) are slidably fitted as shown in FIGS. 2 and 3. Each coil spring 36 is interposed between each plunger 35 and bush 33 to form each pump chamber 37 in each cylinder hole 34b, and the hemispherical head of each plunger 35 is connected to the inner ring of the ball bearing 32. Each pump chamber 37 is biased so as to be brought into contact with each communication hole 33a of the bush 33.
It is designed to be connected to the half-moon-shaped suction notch 26b or discharge notch 26C (see FIGS. 2 and 3) of the bottle 26 through it. Note that the suction notch 26b is
The oil passage Pi (see FIG. 1) communicates with the reservoir R through the suction passage 26d of the bottle 26, while the discharge notch 26C communicates with the oil passage P2 (see FIG. 1) through the discharge passage 26e of the bottle 26.
is connected to.

A control piston mechanism 38 is provided on a cylindrical boss 21b (see FIG. 3) that protrudes from an intermediate portion on one side of the housing section 21.
A control piston mechanism 39 is provided in a cylindrical boss 21C (see FIG. 3) protruding from the other intermediate portion of the piston 1.

The control piston mechanism 38 has a control piston 38a that is slidably inserted into the cylindrical boss 21b. The ball bearing 3 is pushed into the large diameter inner hole 21a by being biased by the engaged coil spring 38c.
2 and an oil chamber 3 in the cylindrical boss 21b.
Form 8d.

The control piston mechanism 39 has a control piston 39a that is slidably fitted into the cylindrical boss 21c and has a male threaded plug 39b screwed onto the outer end of the cylindrical boss 21. An oil chamber 39c is formed therebetween, and the outer ring of the ball bearing 32 is in contact with the outer ring. In this case, the pressure receiving area of the control piston 39a for the oil pressure in the oil chamber 39c is larger than the pressure receiving area for the oil pressure in the oil chamber 38d of the control piston 38a. This means that the eccentricity e of the ball bearing 32 is caused by the pushing force to the left in FIG. This means that it changes according to the difference between the pressure force and the pushing force to the right in FIG. 3 based on the oil pressure in the oil chamber 38d.

Also, the change in eccentricity e of the coil spring 38
This is achieved when the oil pressure in the oil chamber 39c is equal to or higher than a predetermined oil pressure value Ps in relation to the initial setting load c and the difference in pressure receiving area between the control pistons 38a and 39a.

The pilot valve 40, as shown in FIGS. 2 and 3,
It is provided in the upper part of the housing section 21 coaxially with the linear actuator 50, and a cylindrical sleeve 42 and a rod-shaped magnetic material are installed in the stepped inner hole 41 formed in the upper part of the housing section 21. A valve body 4 consisting of
3. It is constructed by assembling a coil spring 44 and an annular collar 45. As shown in FIG. The sleeve 42 is biased toward the right side in the figure, and an annular valve portion 42c that partitions and forms a low pressure chamber 42a and a high pressure chamber 42b is provided in the hollow portion of the sleeve 42, protruding from the center of the inner circumferential surface of the hollow portion of the sleeve 42. has been done. In this case, the low pressure chamber 42a communicates with the large diameter inner hole 21a of the housing section 21 through the hollow portion of the collar 45, the large diameter portion 41b of the stepped inner hole 41, and the communication passage 41C. On the other hand, the high pressure chamber 42b communicates with the oil chamber 38d through the communication passage 4.1d, and communicates with the discharge passage 26e through the communication passage 41e, the annular groove 26g of the bottle 26, and the communication passage 26f. Thus, the sleeve 42 is displaced and slid according to the difference between the elastic force of the coil spring 44, the sum of the oil pressure in the low pressure chamber 42a, and the oil pressure in the high pressure chamber 42b. However, the initial set load of the coil spring 44 is determined so as to be balanced with the oil pressure in the high pressure chamber 42b when the low pressure chamber 42a and the oil chamber 39c communicate with each other, as described later. Note that the collar 45 is adapted to engage with a stepped portion of the stepped inner hole 41.

The valve body 43 also serves as a plunger for the linear actuator 50, and is fitted in the annular valve portion 42c of the sleeve 42 so as to be slidable relative thereto. It is biased towards The valve body 43 has an annular groove 43a facing the inner peripheral surface of the valve portion 42c of the sleeve 42, and an H-shaped communication passage 43b communicating with the annular groove 43a. is somewhat narrower than the width of the valve portion 42c. Further, the communication passage 43b passes through an annular groove 44 bored in the housing section 21 concentrically with the valve body 43 between the stepped inner hole 41 and the linear actuator 50.
It communicates with the inside of the oil chamber 39c via a.

The linear actuator 50 has a housing section 2
1, a valve body 43 fitted in a hollow part of the solenoid 51 so as to be displaceable concentrically, and the coil spring 52.
The coil spring 52 is engaged with a cap 53 screwed into the opening of the mounting hole 50a, urges the valve body 43 to the left in FIG.
is superimposed on the valve portion 42C to form the annular groove 43a into the low pressure chamber 42a.
and shut off from the high pressure chamber 42b. The solenoid 51 moves the valve body 43 to the coil spring 52 in response to an increase in the inflow current.
It is attracted and displaced against the elastic force of. This means that the linear actuator 50 cooperates with the pilot valve 40 to connect the annular groove 43a of the valve body 43 to the low pressure chamber 42a and the high pressure chamber 4.
It means to selectively bring about communication with 2b.

The electromagnetic switching valve 60 is a three-way electromagnetic switching valve, and when both solenoids 61 and 62 are demagnetized, it connects the oil passage P2 and the oil passages P3 and P4 connected to the power cylinder 70 via the oil passage P5. Connect to reservoir R. Further, the electromagnetic switching valve 60 causes the oil passage P3 to communicate with the oil passage P2 and the oil passage P4 by energizing the solenoid 61, and connects the oil passage P4 to the oil passage P2 by energizing the solenoid 62.
The oil passage P3 is made to communicate with the oil passage P5. The power cylinder 70 has a piston 72 pivotally supported by the rank par 13 in the cylinder 71 and slidably fitted therein to form left and right chambers 73 and 74.
These left and right chambers 73, 74 are connected to both oil passages P4. They are each connected to the electromagnetic switching valve 60 by P3.

Therefore, the power cylinder 70 is supplied with pressure oil from the oil pump 30 through the oil passage P2, the electromagnetic switching valve 60, and the oil passage P4 into the left chamber 73 to assist in turning the steering wheel 11 in the right direction. Move the piston 72 to the right. Further, the power cylinder 70 is connected to the oil passage P2 from the oil pump 30 in the right chamber 74. Pressure oil is applied through the electromagnetic switching valve 60 and the oil passage P3 to move the piston 72 to the left to assist in turning the steering handle 11 to the left. Note that the pressure oil in the right chamber 74 (or left chamber 73) flows through the oil passage P3 (or P4), the electromagnetic switching valve 60, and the oil passage P as the piston 72 moves to the right (or left).
5 and is discharged into the reservoir R.

Further, the power steering device has an electric control mechanism 80 configured together with the linear actuator 50 and the electromagnetic switching valve 60 of the electric oil pressure generating mechanism P, as shown in FIG. This electric control mechanism 80 includes a torsion sensor 81, a torque sensor 82, a vehicle speed sensor 83, and these torsion sensors 81. It has an electric control circuit 84 connected to a torque sensor 82 and a vehicle speed sensor 83, and a torsion sensor 81.
is composed of a strain sensor provided on the steering shaft 12, and detects rotation to the left (or right) with respect to the neutral state of the steering shaft 12 (corresponding to the neutral state of the steering handle 11), and detects twisting. Occurs as a signal. In such a case, the level of the torsion signal from the torsion sensor 81 becomes positive (or negative) when the steering shaft 12 rotates to the left (or right).

The torque sensor 82 detects the amount of torsion of the steering shaft 12 as a steering torque, and generates this as a l·lux voltage. Vehicle speed sensor 83 detects the vehicle speed of the vehicle and generates a pulse signal at a frequency proportional to this.

The electric control circuit @84 has two voltage dividers 8 as shown in FIG.
4al, 84a2, a comparator 84b connected to the voltage divider 84a1 and the torsion sensor 81, and a voltage divider 84a2.
and a comparator 84C connected to the torsion sensor 81, and power amplifiers 84d and 84e connected to each of these comparators 84b and 84c, respectively.
4a1 divides the power supply voltage +Vc from the DC power source by both series resistors rl and r2, and generates a positive divided voltage from the common terminal of both series resistors rl and r2. On the other hand, voltage divider 84a2
are both series resistors r3. The power supply voltage -Vc from another DC power supply is divided by r4, and both series resistors r3. A negative divided voltage is generated from the common terminal of r4. In such a case, voltage divider 8
The positive divided voltage from voltage divider 84a1 corresponds to the leftward rotation angle of the steering shaft 12 from the neutral position, while the positive divided voltage from voltage divider 84a2
The negative partial voltage from the steering shaft 12 corresponds to an idle rotation angle of the steering shaft 12 from the neutral position to the right.

Comparator 84b generates a high level signal only when the level of the torsion signal from torsion sensor 81 is higher than the positive divided voltage from voltage divider 84a1, while comparator 84C generates a high level signal only when the level of the torsion signal from torsion sensor 81 is higher than the positive divided voltage from voltage divider 84a1. A high level signal is produced only when it is lower than the negative divided voltage from voltage divider 84a2. The power amplifier 84d amplifies the power of the high level signal from the comparator 84b and applies it to the solenoid 61 as an excitation signal necessary for excitation of the solenoid 61 of the electromagnetic switching valve 60, while the power amplifier 84e amplifies the high level signal from the comparator 84. The high level signal from c is amplified in power and applied to the solenoid 62 of the electromagnetic switching valve 60 as an excitation signal necessary for excitation of the solenoid 62.

The electric control circuit 84 also includes a frequency-voltage converter 84f (hereinafter referred to as an F-■ converter 84) connected to the vehicle speed sensor 83.
), a torque sensor 82 and an F-V converter 84
Each A-D converter 84g, 84h connected to f, a function generator 84i connected to both these A-D converters 84g, 84h, and D connected to this function generator 84i.
-A converter 84j, a voltage-current converter 84 connected to this I)-A converter 84j, and a power amplifier 847 connected to this voltage-current converter 84k! It is equipped with F
-V converter 84f converts the frequency of the pulse signal from vehicle speed sensor 83 into a vehicle speed voltage proportional to this frequency. The A-D converter 84g converts the torque voltage from the torque sensor 82 into a torque digital voltage Vt, while the A-D converter 84
h converts the vehicle speed voltage from the F-V converter 84f into a vehicle speed digital voltage Vs.

The function generator 84i specifies the communication switching pressure value of the annular groove 4.3H of the valve body 43 to the high pressure chamber 42b.
A three-dimensional map M (indicated by a solid line in FIG. 5) representing the relationship between the optimum oil pressure upper limit value PO proportional to the upper limit digital voltage ■0, the torque digital voltage yt, and the heavy speed digital voltage VS is stored in advance. Based on this three-dimensional map M, a limit value digital voltage Vo is determined according to the torque digital voltage Vt from the A-D converter 84g and the vehicle speed digital voltage VS from the A-1) converter 84h.
It occurs in search of. In such a case, in the three-dimensional map M, Vo=Voi (hereinafter referred to as initial upper limit digital voltage Voi) is Vt=0 (i.e., the steering shaft 12
This corresponds to the case when the amount of twist of -〇).

The r)-A converter 84j converts the upper limit digital voltage VO from the function generator 84i into an upper limit voltage.

The voltage-current converter 84 converts the upper limit voltage from the DA converter 84j into a current proportional to the upper limit voltage and generates it as an upper limit current signal. Power amplifier 84I! is generated as a drive signal by power amplifying the upper limit current signal from the voltage-current converter 84k. This means that the linear actuator 50 controls the solenoid 51 based on the current flowing into the solenoid 51 according to the value of the drive signal from the power amplifier 84I2.
This means that the valve body 43 is attracted against the coil spring 52 after an electromagnetic force is generated.

In this embodiment configured as described above, when the vehicle is driven in a straight line under the operation of the device of the present invention, the rotor 34 of the oil pump 30 is driven by the rotary electric motor M as shown in FIG. and rotate in the direction of the arrow shown. At this time, since no oil pressure is generated in the oil chamber 39C of the control piston mechanism 39, the rotor 34 of the oil pump 30 rotates to the position shown in FIG. Each piston 35 corresponds to the lower half of the rotor 34 in the figure.
slides outward from each cylinder hole 34b of the rotor 34 and enters the pump chamber 37 from the reservoir R to the oil passage P1. Inhalation is carried out through the suction passage 26d of the bottle 26, the suction notch 26b, and each communication hole 33a of the bush 33.

Next, each piston 35 sucked in this way is moved to the rotor 3.
4, each piston 35 slides into each cylinder hole 34b in cooperation with the ball hair ring 32, and its respective pump chamber 37 Push the hydraulic oil inside: each communication hole 33a of L33, discharge notch 26c of bottle 26, and discharge passage 2
6e and discharges it as pressure oil into the oil passage P2, and also through the communication passage 26c of the bottle 26, the annular groove 26g, and the dual-speed passages 41e and 41d to the oil chamber 38 of the control piston mechanism 38.
Discharge within d. Further, at this time, discharge pressure oil flows into the high pressure chamber 4.2b of the sleeve 42 from the communication passage 41e, but since the pressure of this discharge pressure oil is smaller than the elastic force of the coil spring 44, the collar 45 is stepped. The low pressure chamber 42a of the sleeve 42 is brought into communication with the annular groove 438 of the valve body 43 by engaging with the stepped portion of the inner hole 41. The valve body 43 is located at the left end position in FIG. 3 under the biasing force of the coil spring 52 while the solenoid 51 of the linear actuator 50 is demagnetized.

In addition, in such a state, both comparators 84b, 8
4c is the torsion sensor 81 and both voltage dividers 84al, 84a
2 does not generate a high level signal, and the electromagnetic switching valve 60 demagnetizes each oil passage P2. P3 and P4 are communicated with oil passage P5. Further, the A-reverse converter 84g generates a torque digital voltage Vt (currently, Vt=O when the amount of twist of the steering shaft 12 is zero) in cooperation with the torque sensor 82, and the F -V converter 84f generates a vehicle speed voltage in cooperation with vehicle speed sensor 83, A-D converter 84h generates the vehicle speed voltage as vehicle speed digital (L4 voltage Vs),
The function generator 84i is based on the three male V-tube M, and the A-D converter 8
An initial upper limit value digital voltage Vo=Vo i is determined according to the torque digital voltage Vt=O from the A-D converter 84h and the vehicle speed digital voltage Vs from the A-D converter 84h, and the D-A converter 84j calculates the initial upper limit value digital voltage Vt=O from the A-D converter 84h. Analog converts voltage Voi to upper limit voltage and converts voltage to current converter 84 k
generates the upper limit voltage from the DA converter 84j as an upper limit current signal, and in response, the power amplifier 84β generates a drive signal.

Then, the electromagnetic coil 51 of the linear actuator 50 becomes the power amplifier 847! An electromagnetic force is generated in response to an inflow current corresponding to the value of the drive signal (corresponding to the initial value - the limit value digital voltage Voi), and the valve body 43 is moved by the coil spring 5.
Aspirate against 2. In this case, since the initial upper limit digital voltage Voi is small, the low pressure chamber 42a of the sleeve 42 and the annular groove 432 of the valve body 43 remain in communication with each other. Therefore, in such a state, the pressure oil discharged from the oil pump 30 into the oil passage P2 is discharged into the reservoir R from the electromagnetic switching valve 60 and the oil passage P5 under the maximum value of the eccentricity e. At this time, the amount of pressure oil discharged from the oil pump 30 reaches the maximum value represented by the straight line L1 in FIG.

In this state, when the steering wheel 11 is rotated to the left, the steering shaft 12 is rotated to the left and the pinion 1 is rotated to the left.
2a is rotated to the left, the rack bar 13 is moved to the left, and the steering wheel 14 is steered to the left. Further, since the level of the torsion signal generated from the torsion sensor 81 as the steering shaft 12 rotates to the left becomes higher than the positive divided voltage from the voltage divider 84a1, a high level signal is output to the comparator 84b.
is generated as an excitation signal by the power amplifier 84d. As a result, the electromagnetic switching valve 60 is connected to the power amplifier 84.
By excitation of the solenoid 61 in response to the excitation signal from d, the oil passage P2 is communicated with the oil passage P3, and the oil passage P
4 is communicated with the oil passage P5. At this time, the oil pressure in the discharge passage 26e of the bottle 26, that is, in the high pressure chamber 42b of the sleeve 42 rises in accordance with the communication between the oil passages P2 and 23, causing the sleeve 42 to slide against the coil spring 44.

Further, the amount of leftward twisting that occurs in the steering shaft 12 in response to the leftward rotation of the steering shaft 12 as described above is generated as a torque voltage by the torque sensor 82, and this torque voltage is transmitted to the A-D converter. 84g is converted into a torque digital voltage Vt.

Then, the function generator 84+ generates A- based on the three-dimensional map M.
D converter 84. Torque digital voltage Vt from g
(>0) and the upper limit digital voltage Vo (>Vo
i), and the power amplifier 84d responds to the upper limit digital voltage vO by determining the DA converter 84j and the voltage -
The current converter 84 generates the optimum oil pressure upper limit value PO as a drive signal by means of the tr/+(bar) in substantially the same manner as described above.Then, the current flowing into the electromagnetic coil 51 of the linear actuator 50 The valve body 43 is further attracted by the electromagnetic coil 51 against the coil spring 52, thereby communicating the annular groove 43a with the high pressure chamber 42b of the sleeve 42.

In this case, communication between the annular groove 43a of the valve body 43 and the high pressure chamber 42b of the sleeve 42 is established through both oil passages P2. P3
This is achieved by displacing the sleeve 42 and the valve body 43 in opposite directions in response to an increase in the oil pressure in the high pressure chamber 42b due to the communication and an increase in the current flowing into the electromagnetic coil 51 of the linear actuator 50. The discharge pressure oil flows into the oil chamber 39c through the annular groove 43a, the communication path 43b, the annular groove 44, and the communication path 4.48 of the valve body 43, and flows into the oil chamber 39c.
Increase the oil pressure in c.

Further, as described above, from the oil pump 30 to the oil path P2
The pressure oil discharged into the inside flows into the right chamber 74 of the power cylinder 70 through the electromagnetic switching valve 60 and the oil path P3, and the pressure oil in the left chamber 73 flows into the oil path P4. It passes through the electromagnetic switching valve 60 and the oil passage P5 and is discharged into the reservoir R. This results in
The power cylinder 70 is powered by the piston 7 using pressure oil in the right chamber 74.
2, that is, the leftward movement of the rack bar 13 is promoted and the leftward rotation of the steering handle 11 is started to be assisted. After that, the oil pressure in the oil chamber 39C of the control piston mechanism 39 exceeds the optimum oil pressure upper limit Po, and the predetermined oil pressure value Ps (both straight lines L in FIG.
1. When the ball bearing 32 rises to a point corresponding to the intersection of L2, the ball bearing 32 receives the sum of the pushing force of the control piston 39a based on the predetermined oil pressure value Ps in the oil chamber 39C, the oil pressure in the oil chamber 38d, and the elastic force of the coil spring 38c. Piston 38 based on
Due to the difference between the pushing force of a and the pushing force, it rapidly deviates to the left in FIG. This means that the eccentricity e of the oil pump 30 rapidly decreases. Therefore, the amount of pressure oil discharged from the oil pump 30 into the oil passage P2 rapidly decreases at the same time as the oil pressure in the oil chamber 39C matches the optimum oil pressure upper limit value PO, and the steering wheel 11 is rotated to the left. The assisting action of the power cylinder 70 for dynamic operation is rapidly reduced.

As can be understood from the above explanation, the assisting action for the leftward rotation operation of the steering handle 11 is smoothly performed according to the maximum discharge pressure oil amount from the oil pump 30 under the maximum value of the eccentricity e. After the oil pressure in the oil chamber 39C reaches the predetermined oil pressure value Ps, the pressure of the steering wheel 11 is suppressed according to the sudden decrease in the amount of pressure oil discharged from the oil pump 30 based on the sudden decrease in the eccentricity Ne. The steering feeling is light at the start of the operation and then becomes heavy, thereby ensuring a stable steering feeling.

Also, such a change in steering sensation is caused by the map M in Fig. 5.
As can be easily understood from the above, the larger the steering force on the steering wheel 11 (that is, the amount of twist of the steering shaft 12), the faster the steering force is applied, and the greater the steering force is, the faster the steering feeling at the start of operation of the steering wheel 11 is. The steering feeling after that is light and becomes heavy quickly as the steering force increases.

Furthermore, as can be easily understood from the map M in FIG.
The annular groove 43a of the valve body 43 of 0 is connected to the low pressure chamber 4 of the sleeve 42.
The higher the vehicle speed, the higher the vehicle speed, the lower the oil pressure in the high pressure chamber 42b corresponding to the pressure value communicated by leftward movement of the valve body 43 becomes lower than the predetermined oil pressure value Ps in the order of curves L1-L2-L3 in FIG. . In other words, the higher the vehicle speed, the more the annular groove 43 of the valve body 43
The communication switching pressure value from the high pressure chamber 42b to the low pressure chamber 4.2a becomes lower, and as a result, the higher the vehicle speed, the lower the pressure value at which the eccentricity Ne of the oil pump 30 starts decreasing from the maximum value, and the steering wheel The suppression pressure value of the assisting action of the power cylinder 7o for leftward steering of the power cylinder 7o is lowered. This means that the higher the vehicle speed, the heavier the steering feel on the steering wheel 11 becomes.

Further, as described above, since the full pressure oil from the oil pump 30 is applied to the right chamber 74 of the power cylinder 7° via the electromagnetic switching valve 60, the power loss of the oil pump 30 is reduced to almost zero, and the oil pressure relative to the steering wheel 11 is reduced. The feeling of steering to the left can be made heavier (or lighter) as the vehicle speed increases (or decreases). Note that, since only the torque sensor 82 and the angle sensor 81 are attached to the steering shaft 12, the steering shaft 12 has a neat shape.

Further, in the above-mentioned operation, the case where the steering wheel 11 is rotated to the left has been explained, but instead of this, the above-mentioned operation and effect can also be achieved when the steering wheel 11 is rotated to the right. Substantially similar effects can be achieved. In such a case, the level of the torsion signal from the torsion sensor 81 accompanying the rightward rotation of the steering shaft 12 becomes lower than the negative divided voltage from the voltage divider 84a2, and in response, a high level signal is output from the comparator 84c. is generated as an excitation signal by the power amplifier 84e, and the solenoid 62 is energized in response to the excitation signal by the electromagnetic switching valve 60, thereby causing the oil passage P2 to communicate with the oil passage P4, and also connecting the oil passage P2 to the oil passage P4.
3 is communicated with the oil passage P5, and assists the rightward rotation of the steering handle 11 based on the rightward movement of the rank par 13 by the power cylinder 70. It is only different from the effect associated with .

In the above embodiment, the pressure oil supply switching control to the power cylinder 70 was performed by the electromagnetic switching valve 60, but instead of this, a directional switching valve having substantially the same function as the electromagnetic switching valve 60 may be used. coaxially assembled on the steering shaft 12,
This directional switching valve may be controlled in the same way as the electromagnetic switching valve 60 in response to changes in the direction of rotation of the steering shaft 12.

Further, in the embodiment described above, the oil pump 30 was driven by the rotary electric motor M, but instead of this,
The oil pump 30 may be driven by an internal combustion engine.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention, FIG. 2 is a cross-sectional view of the electric hydraulic pressure generating mechanism shown in FIG. 1, and FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. 4 is a block diagram of the electric control circuit of FIG. 1, FIG. 5 is a three-dimensional map stored in the function generator 84j of FIG. 4, and FIG. 6 is a diagram of the oil pump of FIGS. 2 and 3. It is a graph which shows the relationship between the discharge pressure oil amount and discharge oil pressure. Explanation of symbols 10... Steering mechanism, 12... Steering shaft, 30... Oil pump, 38.39... Control piston mechanism, 40
...Pilot valve, 50...Linear actuator, 60...Solenoid switching valve, 70...Power cylinder, 7
1... Right ventricle, 72... Piston, 73... Left ventricle,
81...Torsion sensor, 82...Torque sensor, 8
41...Function generator, M...Rotating electric motor, P...
Electric hydraulic pressure generation mechanism.

Claims (1)

[Claims] A steering mechanism that transmits the rotation of the steering shaft of the vehicle to the piston shaft of the power cylinder to steer the steering wheels; and a steering mechanism that is driven by a prime mover to generate pressure fluid in an amount according to a variable capacity, and that is driven by a prime mover and generates pressure fluid in an amount according to a variable capacity, and has two chambers of the power cylinder. a variable displacement pump for supplying pressure fluid to one of the two chambers of the power cylinder, and supplying pressure fluid from the pump to both chambers of the power cylinder in response to the direction of rotation of the steering shaft, so that the power cylinder assists the operation of the steering mechanism. a switching means for selectively switching the pressure fluid; when the pressure fluid is applied from the pump and the pressure of the pressure fluid is less than a predetermined pressure value, the variable displacement of the pump is maintained at a maximum capacity value; capacity control means for controlling the variable capacity to decrease in response to a rise above a pressure value; and detection for detecting steering torque generated in the steering mechanism in response to rotation of the steering shaft and generating it as a torque signal. and the torque signal from a predetermined relationship determined to increase (or decrease) the pressure value applied to the pressure fluid from the pump to the capacity control means in accordance with an increase (or decrease) in the steering torque. output signal generating means for determining the applied pressure value and generating it as an output signal; and application permitting means for allowing application of the pressure fluid from the pump to the capacity control means in response to the output signal. A vehicle power steering device equipped with a variable displacement pump.