JP2898899B2 - Motor-driven hydraulic actuator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor-driven hydraulic actuator which converts the rotation of a motor into a linear motion of a plunger via a screw mechanism and controls the hydraulic pressure by the motion of the plunger. In particular, the present invention relates to a technique that can be effectively used for various types of brake control such as automatic braking and traction control.

[0002]

BACKGROUND OF THE INVENTION A hydraulic actuator of this type generally includes a motor that rotates in response to a drive signal, a screw mechanism for converting rotation to linear motion in accordance with the rotation of the motor, and a screw mechanism. And a plunger that receives a force associated with the linear movement at one end and linearly moves by itself, and receives a hydraulic pressure corresponding to the linear movement at the other end. The screw mechanism section includes a bolt member and a nut member that are screwed together, and one of the bolt member and the nut member rotates according to the rotation of the motor, and the other member moves linearly. is there. For such a motor-driven hydraulic actuators, the publications, eg KOKOKU 6-57525 Patent, or real-Open No. 6-18132 reveals.

When operating such a hydraulic actuator, a plunger moved from an initial position by rotation of a motor receives a reaction force due to hydraulic pressure. Therefore, in order to keep the plunger in a stopped state, it is necessary to continue driving the motor (that is, keep energizing the motor) to generate a torque balanced with the reaction force, or to cut off the energization to the motor. A separate clutch mechanism must be provided to prevent reverse rotation of the motor. However, the method of generating torque in the motor itself as in the former has problems such as an increase in power consumption and overheating of the motor, while the method of separately providing a clutch mechanism as in the latter increases the number of parts and assembles. And the cost increases.

[0004]

An object of the present invention is to provide a technique that can counteract the reaction force caused by the hydraulic pressure by a mechanical method, not by an electric method of continuing to energize a motor. It is an object of the present invention to provide a technique capable of obtaining a similar function without providing another clutch mechanism. In other words, an object of the present invention is to provide a hydraulic actuator which has a small number of parts, is easy to assemble, and is cost-effective.

[0005]

In the present invention, attention has been paid to making the screw mechanism itself have the same function as the above-mentioned clutch mechanism. Here, with reference to FIG. 1, consider a case where the motor rotates a male screw (bolt member), and the male screw applies a thrust (force of linear motion) to a female screw (nut member) that is screw-coupled to the male screw. .
First, let's specify the relevant signs. α: Thread angle β: Lead angle μ: Screw surface friction coefficient ρ: Friction angle T: Rotational torque of male screw (bolt member) F: Thrust of female screw (nut member) d: Effective screw diameter When converting the rotational force into thrust, T = F × (d / 2) × tan (β + ρ), screw efficiency η = tan
β / tan (β + ρ), and when converting thrust into rotational force, T =
F × (d / 2) × tan (β−ρ). given that,
When β> ρ, a rotational force is generated by the thrust. However, when β ≦ ρ, the screw is locked and no rotational force is generated even when the thrust is received. Therefore, the screw shape of the screw mechanism may be a shape that satisfies the following equation (2).

(Equation 2)

According to the equation, α and β related to the screw shape
In addition, the equation can be satisfied by setting the value of the screw surface friction coefficient μ. However, the thread surface friction coefficient μ is easily affected by environmental conditions such as lubrication. Therefore, it is very difficult to determine the thread angle α and the lead angle β in advance, and then make the value of the screw surface friction coefficient μ satisfy the condition of the equation. Therefore, it is preferable to first set the screw surface friction coefficient μ, and then determine α and β under the conditions. The value of μ is usually about 0.2, and it is thought that even if it decreases, it does not become 0.1 or less. On the other hand, in order to ensure the condition of β ≦ ρ in the above equation, the larger the value of μ, the better. Therefore, conversely, considering the range of variation of μ due to environmental conditions, the value of μ is set to a smaller value,
For example, it can be said that it is preferable to set the value to 0.2, 0.1, or even 0.05, and to set α and β relating to the screw shape below the value. In addition, among α and β, as the thread angle α increases, the efficiency of converting the rotational force into thrust decreases, and when the angle decreases, the centering property deteriorates. From these facts, it is generally appropriate that the value of α is about 30 °. As a result, after determining the values in the order of μ and α, it is optimal to determine the lead angle β so as to satisfy the above expression.
Specifically, when α = 30 ° and μ = 0.2, β ≦ ρ = 11.69 °, and when μ = 0.1, β ≦ ρ
= 5.91 ° and μ = 0.05, β ≦ ρ = 2.96
°. The value of the lead angle β may be slightly smaller than the value of ρ. For example, when μ = 0.05, β is set to 2.95 ° which satisfies the expression. In this case, the screw mechanism itself including the bolt member and the nut member performs the same function as the mechanical clutch described above. Therefore, it is easy to assemble without increasing the number of parts,
It is also very advantageous in terms of cost.

[0007]

FIG. 2 shows an embodiment in which the present invention is applied to an automatic brake system. FIG. 2 is an overall piping system diagram of the automatic brake system, and FIG. 3 is a diagram of a motor-driven hydraulic actuator. FIG. 4 is an enlarged sectional view of a portion surrounded by a circle 4 in FIG. In FIG. 2, a master cylinder 12 carrying a reservoir 10 is of a tandem type, and its operation is assisted by a booster 14. The master cylinder 12 and the booster 14 are connected to each other with their axes aligned, and are operated by a depression operation of a brake pedal 16 on the axis. Tandem type master cylinder 12
Has two hydraulic chambers in the axial direction, and brake pipes 21 and 22 extend from two discharge ports 12a and 12b communicating with the respective hydraulic chambers. Pipes in this brake system are front and rear pipes, a brake pipe 21 on the side near the cylinder bottom is a rear brake pipe, and the other brake pipe 22 is a front brake pipe. The motor-driven hydraulic actuator 50 of the present invention
It is located in the middle of the rear brake pipe 21 communicating from the second side to the wheel cylinders of the wheel brake devices 18R, 18L, and functions as an emergency brake when the vehicle is stopped. That is, when the vehicle starts moving when the vehicle is stopped, particularly when there is no driver, the hydraulic actuator 50 detects the movement and increases the braking force of the rear wheel brake devices 18R and 18L, thereby stopping the vehicle. This is a device for executing an automatic braking system that maintains the vehicle speed. Note that the concept of the automatic braking during a stop is already known, for example, from Japanese Patent Application Laid-Open No. 61-102357. Further, the hydraulic actuator 50 can be arranged in the middle of the front brake pipe 22. However, on the rear side, the load of the load loaded by the vehicle can be received, and a more sufficient stopping force can be given as compared with the front side.

Next, the internal structure of the hydraulic actuator 50 will be described with reference to FIG. The casing of the hydraulic actuator 50 includes a stepped cylinder body 60 and a box part 70. Cylinder body 6
Numeral 0 has a cylinder hole along the axial direction inside, and the box portion 70 is arranged orthogonal to the axis of the cylinder main body 60. Such box portion 70 includes a thick substrate 72 and a cover 74 supported on the substrate 72. The substrate 72 is attached to the open end of the large-diameter portion 610 of the cylinder body 60, whereby the box part 70 and the part of the cylinder body 60 are integrated. Substrate 72
Is a base for supporting the electric motor 80, and a cover 74 is internally provided with a gear mechanism 82 for transmitting rotation.
To accommodate. The rotation transmission gear mechanism 82 includes a small gear 82s and a large gear 82b, and the small gear 82s is
And the large gear 82b are integrally supported by the rod 90, respectively. The rotation of the electric motor 80 is transmitted to the rod 90 side in a reduced form through the small gear 82s and the large gear 82b. Therefore, the rotation transmission mechanism 82 is also a speed reduction mechanism. In the hydraulic actuator 50, since the rotating shaft 81 of the electric motor 80 and the rod 90 receiving the rotating force from the motor 80 are arranged side by side, the overall length in the axial direction is relatively short. . Of course, if space is allowed, the rotating shaft 81
Each axis of the rod 90 and the rod 90 may be the same.

The rod 9 which receives the rotational force of the electric motor 80
0 is supported by the bearing 100. The bearing 100 itself is a lid member 110 with a flange 110f.
It is supported inside. The lid member 110 clamps the substrate 72 between the end of the cylinder body 60 and its own flange 110f by its own screw coupling force. In addition, the lid member 110 is attached to the sleeve 1 in the large diameter portion 610.
20 is prevented from slipping out. A notch is formed in the inner sleeve 120 at the outer periphery of the end facing the inner end of the lid member 110. The notch is used for positioning the sleeve 120 in the axial direction and for preventing the sleeve 120 from rotating around the large diameter portion 610. That is, the sleeve 120
The cylindrical member 8 fixed to the back of the boss 611
02 (operator 80 for a limit switch 800 described later)
1), and the above-mentioned positioning and detent are applied. The hole 120h on the inner periphery of the sleeve 120 has a hexagonal cross section, and the shape matches the outer shape of the nut member 300. Such a sleeve 120
Guides the axial movement of the nut member 300 while inhibiting the rotation of the nut member 300. A ring member 130 is provided at the inner end of the sleeve 120, and the ring member 130 is one stopper having a cushion function of restricting the maximum movement of the nut member 300. The other stopper for the nut member 300 is a cup member 14 having an L-shaped cross-section located in the middle of the rod 90.
0, and the cushion member 1 on the inner periphery of the cup member 140
50. The cushion member 150 includes the rod 90
The force from the nut member 300 is absorbed via the cup member 140 while being supported by the flange portion 90f integral with the flange member 90f.
Both stoppers exert their functions when the nut member 300 has an overstroke.
Therefore, those stoppers do not come into contact with the nut member 300 in a range where the nut member 300 makes a normal stroke.

The rod 90 has a substantially middle flange portion 90.
A male screw is cut into a portion located inward of the cylinder main body 60 from the boundary of f to form a bolt member 95. The male screw of the bolt member 95 is compatible with the female screw of the nut member 300, and the nut member 300 and the bolt member 95 constitute a screw mechanism for converting rotation to linear movement. From the point of view of motion transmission, the rotation of the electric motor 80
0, and the rotating rod 90, that is, the bolt member 95, moves the nut member 300 in a linear direction. The nut member 300 that moves linearly is connected to the plunger 20.
Produces 0 strokes. The plunger 200 is inside the cylinder main body 60 and extends from the large diameter portion 610 to the small diameter portion 620. The plunger 200 includes a concave portion 202 at an end of the cylinder main body 60 on the large diameter portion 610 side,
While receiving the bolt member 95 in the concave portion 202,
The open end portion of the concave portion 202 faces one end surface of the nut member 300. In addition, the opposite end of the plunger 200 (the bottom side of the cylinder body 60, that is, the small diameter portion 620).
Side end) receives a biasing force from the return spring 160 while incorporating the center valve 430.

The cylinder body 60 has three bosses 621, 622, 623 on the small diameter portion 620 side and one boss portion 611 on the large diameter portion 610 side. Boss 6 near bottom
Reference numeral 21 denotes a pipe connecting portion that communicates with each wheel cylinder of the wheel brake devices 18R and 18L.
Reference numeral 22 denotes a pipe connection portion that communicates with the master cylinder 12 side. Further, the remaining boss portion 623 of the small diameter portion 620 is a mounting portion for mounting the hydraulic pressure switch 700, and further,
The boss portion 611 of the large diameter portion 610 is
This is a mounting part for mounting 0. Plunger 200
There are seal rings 410 and 420 at a distance from each other on the outer periphery of the. Accordingly, the first hydraulic chamber 910 is provided between the two seal rings 410 and 420 inside the small diameter portion 620 of the cylinder body 60, and the second hydraulic chamber is provided between the cylinder bottom and the seal ring 420. Is partitioned. First hydraulic chamber 91
0 is the master cylinder 12 through the inner circumference of the boss 622.
Side, and the second hydraulic chamber 920 is connected to the boss portion 62.
1 is communicated to the wheel cylinder side through the inner circumference, and at the same time, the detected hydraulic pressure is applied to the hydraulic pressure switch 700 of the boss 623.

The state shown in FIG. 3 is an initial state without a brake operation, at which time the center valve 430 is open and the first hydraulic chamber 910 and the second hydraulic chamber 920 are in communication. . However, when the brake is activated, the plunger 20
With the movement of 0, the center valve 430 is closed, and the communication between the first and second hydraulic chambers 910 and 920 is shut off. As a result, the plunger 200 is further moved to the cylinder bottom side, whereby the second hydraulic chamber 9 is moved.
A hydraulic pressure is generated in 20.

In the present invention, the screw mechanism including the bolt member 95 and the nut member 300 of the hydraulic actuator 50 has a specific clutch function. In this example, a metric trapezoidal screw is used as the screw for the bolt member 95 and the nut member 300, and the thread angle α
= 30 ° and the lead angle β is set to 2.95 ° which is equal to or less than 2.96 ° under the condition of the screw surface friction coefficient μ = 0.05 so as to satisfy the relationship of β ≦ ρ in the above equation. doing.
Therefore, as described above, the screw mechanism converts the rotation of the bolt member 95 into a linear thrust of the nut member 300. Even if the nut member 300 receives a thrust in the opposite direction, the screw mechanism section converts the rotation into a linear thrust. It does not convert to 95 torque.

Here, the behavior when the vehicle equipped with the brake system including the hydraulic actuator 50 is stopped will be considered. When the vehicle is stopped only by operating the parking brake, the effect of the parking brake is insufficient.
Suppose the vehicle starts moving. The movement of the vehicle is detected by a vehicle speed sensor, and the energization of the electric motor 80 is started accordingly. As a result, the hydraulic actuator 50 moves the plunger 200 to the cylinder bottom side, generates a hydraulic pressure in the second hydraulic chamber 920, and supplies it to the wheel cylinder. Then, when the hydraulic pressure reaches a predetermined pressure enough to maintain the stop, for example, 70 kg / cm ² ,
This is detected by the hydraulic switch 700, and the power supply to the electric motor 80 is cut off. At this time, the second hydraulic chamber 9 is connected to the nut member 300 via the plunger 200.
Although a force corresponding to the hydraulic pressure of 20 is applied, the hydraulic pressure holding state is maintained by locking the screw.

When the hydraulic actuator 50 is not operated, the center valve 430 is open, so that the hydraulic pressure of the master cylinder 12 can be supplied to the wheel cylinder through the opened center valve 430. On the other hand, when the hydraulic actuator 50 is operating, the center valve 430 is
As 00 moves to the cylinder bottom side, the end of the rod 430a moves away from the pin member 430b fixed to the cylinder body 60 and is closed. However, in this state, when the brake pedal 16 is operated and a hydraulic pressure higher than the hydraulic pressure supplied to the wheel cylinders of the wheel brake devices 18R and 18L is generated in the master cylinder 12, the high hydraulic pressure Is driven from the second hydraulic chamber 920 to the wheel cylinder side while the center valve 430 is opened.

Further, after the hydraulic actuator 50 is operated, when the parking brake is released while the brake pedal 16 is depressed, energization is started to reversely rotate the electric motor 80 in response to such operation. Then, the screw mechanism converts the rotation to the linear movement, and moves the nut member 300 to return to the initial state. Then, by the limit switch 800,
When it is detected that the nut member 300 has returned to the initial position, the power supply to the electric motor 80 is cut off.

Since such a hydraulic actuator 50 is an emergency brake, it is rarely operated. Therefore, it is preferable to periodically check whether or not it operates normally. The check mechanism will be built into an electrical control unit related to the brake system. In the check mechanism,
Check time by timer (for example, once a month)
When the check time comes, the ignition switch is turned on, the electric motor 80 starts rotating, and the hydraulic actuator 50 is operated until the hydraulic switch 700 is operated. Then, the electric motor 80
Is switched so as to rotate in the reverse direction, and when the limit switch 800 detects that the nut member 300 has returned to the initial position, the power supply to the electric motor 80 is cut off and the check ends. Should the electric motor 80
If the hydraulic switch 700 does not operate after the power supply to the hydraulic switch 700 starts, or if the limit switch 800 does not operate after the hydraulic switch 700 operates, it is determined that a failure has occurred. It is notified by a warning lamp or the like.

Although the rotation of the bolt member 95 is converted into the linear motion of the nut member 300 in the illustrated embodiment, the rotation of the nut member may be converted into the linear motion of the bolt member. it can.

[Brief description of the drawings]

FIG. 1 is a screw structure diagram for explaining the present invention.

FIG. 2 is a piping diagram showing a brake system to which the present invention is applied.

FIG. 3 is a sectional structural view of a hydraulic actuator.

FIG. 4 is an enlarged view of a portion surrounded by a circle 4 in FIG.

[Explanation of symbols]

 Reference Signs List 50 hydraulic actuator 60 cylinder body 80 electric motor (motor) 95 bolt member 200 plunger 300 nut member 700 hydraulic switch 800 limit switch

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B60T 7/12

Claims (5)

(57) [Claims] 1. A motor that rotates upon receiving a drive signal, a screw mechanism that converts rotation to linear motion in accordance with the rotation of the motor, and receives, at one end, a force associated with the linear motion of the screw mechanism. themselves to linear motion, moreover, a plunger for receiving a fluid pressure in accordance with the linear movement to the other end, stop the vehicle Te
The plunger is used for an automatic brake system for maintaining a vehicle. A motor-driven actuator having a function of preventing the motor from rotating in the reverse direction when the motor does not receive a drive signal.
The screw mechanism section includes a bolt member and a nut member that are screw-coupled to each other, one of the bolt member and the nut member rotates according to the rotation of the motor, and the other member moves linearly. Further, the screw shape of the screw mechanism portion is a shape that produces the following clutch function A, and is a motor-driven hydraulic actuator. A. The one member is rotated by receiving a rotational force from a motor, and the other member is linearly moved in accordance with the rotation. The screw mechanism is locked. 2. The motor-driven hydraulic actuator according to claim 1, wherein the screw shape of the screw mechanism satisfies the following equation (1). (Equation 1) 3. α in Equation 1 is approximately 30 °.
The motor-driven hydraulic actuator according to claim 2. 4. A cylinder body having a cylinder hole extending along an axial direction, a motor supported by the cylinder body and rotating upon receiving a drive signal, a rotation transmission gear mechanism for transmitting rotation of the motor, and the cylinder hole. And a nut member that is connected to one of the gears of the rotation transmission gear mechanism and that is screw-coupled to the bolt member, and that converts rotation of the bolt member into linear motion of the nut member. A mechanism portion, a plunger positioned inside the cylinder hole, receiving a force associated with linear movement of a nut member of the screw mechanism portion at one end, and defining a control hydraulic chamber together with the cylinder body at the other end. Keeps the vehicle parked
A motor-driven hydraulic actuator for use in an automatic braking system , wherein the plunger moves between a position where the hydraulic pressure of the control hydraulic chamber reaches a predetermined pressure and a position in an initial state where no brake operation is performed. Strokes in accordance with the rotation of the motor, the screw shape in the screw mechanism portion is a shape that produces the next clutch function of A, and in a state where the motor does not receive a drive signal, to prevent reverse rotation of the motor. A motor-driven hydraulic actuator characterized in that the screw mechanism itself has a function. A. The one member rotates by receiving a rotational force from a motor, and linearly moves the other member in accordance with the rotation. On the other hand, in a state where the motor does not receive a drive signal, the plunger is driven by the hydraulic pressure. The screw mechanism is locked. 5. The cylinder body is provided with the following B and C hydraulic pressure switches and limit switches, and the screw shape in the screw mechanism satisfies the following D formula, and the D formula Is approximately 30 °
The motor-driven hydraulic actuator according to claim 4. B. A hydraulic switch for detecting a hydraulic pressure of the control hydraulic chamber and stopping the driving of the motor when the hydraulic pressure reaches a predetermined pressure. C. A limit switch that detects a position of the nut member in the axial direction and stops driving the motor when the nut member returns to an initial position. D.