JPS6365545B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power steering device, and particularly to a power steering device for promoting energy saving.

Recently, demand for power steering devices is expected to increase due to an increase in the number of front-wheel drive vehicles accompanied by an increase in the front wheel load, an increase in the number of female drivers, etc. However, amidst the soaring oil prices and the wave of resource and energy conservation, power steering devices are also becoming increasingly important, and there is a strong desire to make systems smaller and lighter and to reduce energy consumption.

FIG. 1 is a system diagram showing a conventional power steering device, in which a hydraulic cylinder 1 and a power control valve 2 constitute a power assist mechanism of a steering gear device (not shown). Reference numeral 3 denotes a pump, which is constantly driven by the engine 4 through a pulley 5 at the same time as the engine is started and during its rotation;
The fluid (generally oil) in the reservoir tank 6 is supplied to the power assist mechanism, and the tank 6
to circulate.

The oil passage from the pump 3 to the power control valve 2 includes a throttle 9, a relief valve 7 that short-circuits the oil passage to the reservoir tank 6 when the hydraulic pressure in the power control valve 2 becomes excessive, and a discharge amount of the pump 3. A fail-safe mechanism consisting of a flow control valve 8 that short-circuits the oil passage to the reservoir tank 6 when the fluid pressure in the oil passage becomes excessive is provided to prevent sudden pressure in the circuit. Preventing the rise.

However, the prior art as shown in FIG. 1 has the following drawbacks.

Since the pump 3 is directly connected to the engine 4, it constantly rotates while the engine is rotating and supplies pressurized fluid to the power assist mechanism, regardless of whether or not power assist is required for the steering gear device. As a result, the load on the engine increases accordingly, resulting in a large loss of energy consumed to drive the engine.

Conventionally used pumps are constant displacement pumps, and as the rotational speed increases, the discharge flow rate and energy consumption increase linearly. On the other hand, when driving a car, the engine speed increases during acceleration and high speed driving. In both cases of acceleration and high-speed running, the steering resistance during steering wheel operation is small, and almost no power assistance is required. In other words, when the engine speed increases when the car is accelerating or driving at high speed, the pump rotation speed increases and the discharge flow rate increases, but the operation of the pump during this period does not play any role in the steering operation of the car. The loss of energy consumed is large.

In order to reduce the above losses, there are pumps that incorporate flow control valves or drooping valves, but the discharge flow rate of the pump itself does not change, and the stirring resistance inside the pump is shown in Figure 2 as a function of the rotation speed. Since the loss increases in a quadratic manner, the loss cannot be significantly reduced. In Figure 2, the driving horsepower PS is plotted on the vertical axis and the rotational speed N is plotted on the horizontal axis as factors including the stirring resistance inside the pump.

This invention solves the above-mentioned drawbacks of the prior art, and especially when accelerating a car or driving at high to medium speeds, etc.
The object of the present invention is to provide a power steering device that greatly reduces the driving power of the power steering device while the steering gear device hardly requires power assist, and greatly reduces energy consumption. .

FIG. 3 is a system diagram showing an embodiment of the present invention, in which a pump supplies pressurized fluid to a steering gear device including a hydraulic cylinder 10 and a power steering servo valve 11 (power control valve). Two types of pumps, a large-capacity pump 12 and a small-capacity pump 13, are used, and the large-capacity pump 12 is used, for example, when steering a car stationary (when the engine is idling) and when the vehicle speed is low and requires power assist. The main idea is to activate the small capacity pump 13 and only drive the small capacity pump 13 during acceleration, medium-speed, and high-speed running when little power assistance is required.

The large capacity pump 12 is driven by an electromagnetic clutch 14.
The fluid (generally oil) in the reservoir tank 16 is supplied to the power steering servo valve 11 via the hydraulic circuit 17, and then circulated to the reservoir tank 16. . The hydraulic circuit 17 for the pressurized fluid discharged by the large-capacity pump 12 includes a known variable throttle 18 that controls the amount of pressure fluid supplied to the power steering servo valve 11, a flow control valve 19, and a A relief valve 20 is provided to limit the fluid pressure, and a check valve 21 is further provided to prevent pressure fluid from flowing backward from the power steering servo valve 11 and the small capacity pump 13 (to be described later) to the large capacity pump 12. There is.

The small capacity pump 13 is configured to be driven by an electric motor 25 that is driven by a power source battery 22 via a switch 23 and a relay 24, and the fluid in the reservoir tank 16 is transferred to the power steering servo valve 11 via a hydraulic circuit 26. supply and reservoir tank 1
Reflux to 6.

The hydraulic circuit 26 includes a check valve 2 that prevents pressure fluid from flowing backward from the power steering servo valve 11 and the large capacity pump 12 to the small capacity pump 13.
7, and a throttle 28 for controlling the amount of pressure fluid supplied to the power steering servo valve 11 and operating a reaction mechanism described later, and the discharge fluid pressure of the small capacity pump 13 becoming excessive. A relief valve 29 is provided to prevent this.

An electromagnetic clutch 14, which connects and disconnects the driving force of the large capacity pump 12, is connected to a power source battery 22 via an ignition key switch 30, a switch 31, and a relay 32, and performs connection and disconnection operations to be described later.

The electromagnetic clutch 14 and the electric motor 25 are connected to a vehicle speed sensor 33 that generates an electric signal corresponding to a change in vehicle speed, an engine rotation speed sensor 34 that generates an electric signal corresponding to a change in engine rotation speed, and a power steering servo valve. The switches 31 and 23 are opened and closed and controlled via an electrical control device 36 by electrical signals obtained from all or one or two of the circuit pressure sensors 35 that generate electrical signals corresponding to changes in circuit pressure.

The electrical control device 36 controls each of the sensors 33,
The switches 23 and 31 are operated by electrical signals from one or two or all of the switches 34 and 35, but if the vehicle is stopped or running at low speed, the switch 31 is turned on and the switch 23 is turned off. and when the vehicle speed is medium or high, turn switch 31.
In addition, in the on/off operation of the switches 31 and 23, both switches 31 and 23 are turned on during the transition from the low speed range to the medium speed range and vice versa. It is assumed that the function is given as follows.

When the ignition key switch 30 is on and the vehicle is turned off while the engine is idling, or when the vehicle is being steered at low speed, the switch 31 is on and the switch 23 is off. , the relay 32 closes and the electromagnetic clutch 14 is connected, and the large capacity pump 12 is driven by the engine.
4 is turned off, stopping the electric motor 25, and the small capacity pump 13 is inactive. Therefore, the above-mentioned deferral,
During low-speed driving, the pressure fluid discharged from the large capacity pump 12 passes through the hydraulic circuit 17 and reaches the power steering servo valve 1.
1. It is supplied to the hydraulic cylinder 10 and performs power assist for the steering gear device. on the other hand,
Although the small capacity pump 13 is stopped, a check valve 27 is provided in its hydraulic circuit 26, so that the pressurized fluid discharged by the large capacity pump 12 does not flow back to the small capacity pump 13, and the pump remains stationary. operation,
Alternatively, even if the fluid pressure in the hydraulic circuit 17 increases due to steering during low-speed running, there is no effect on the small capacity pump 13, and it is sufficient that the small capacity pump 13 is small and has low pressure resistance.

When the vehicle speed gradually increases, the vehicle speed sensor 33,
Engine speed sensor 34, circuit pressure sensor 3
5, the control device 36 turns on the switch 23 and relay 2
4 to drive the electric motor 25. Therefore, the small capacity pump 13 starts rotating and starts supplying fluid from the reservoir tank 16 toward the power steering servo valve 11 . As the vehicle speed further increases, the control device 36 activates the switch 31 by an electric signal from one or more of the sensors 33, 34, 35.
is off. Therefore, the relay 32 of the power supply circuit of the electromagnetic clutch 14 is turned off, and the electromagnetic clutch 14 is turned off.
is disconnected, and the rotation of the large capacity pump 12 is stopped.
Therefore, the supply of pressure fluid to the power steering servo valve 11 is performed only by the small capacity pump 13. Steering is only assisted by the pressure fluid discharged from the displacement pump 13, and a stable steering feeling can be obtained. The pressure fluid discharged from the small capacity pump 13 is transferred to the large capacity pump 12 by a check valve 21.
Entry to the side is blocked.

Further, as an application, a throttle 28 is provided in the hydraulic circuit 26 of the small capacity pump 13, and the generated fluid pressure is introduced into the hydraulic reaction chamber 37 of a known reaction force mechanism, for example, when operating the steering wheel during high-speed driving. By configuring the steering wheel to apply an appropriate steering reaction force, a more stable steering feeling can be obtained.

Here, the discharge oil amount _l1 of the large-capacity pump 12 is set to the maximum when the engine rotation speed N (or vehicle speed) reaches the idling rotation A as shown in FIG.
After that, the design is such that it decreases as the vehicle speed increases and reaches _zero just before the electromagnetic clutch 14 is disengaged. If the amount of oil discharged from the power steering servo valve 1 is reduced to 1/2, the amount of oil discharged as shown in Fig.
1, a continuous fluid supply curve is obtained across the low speed range L, medium speed range M, and high speed range H, and the electromagnetic clutch 14 is turned off and the large capacity pump 12 is stopped. Also, the causes of unstable steering feeling are eliminated.

The amount of oil discharged by the small-capacity pump 13 only needs to be the minimum flow rate required during high-speed running, so a very small-capacity pump is sufficient, and it is convenient to drive it with a small electric motor powered by a battery. be.

In Figure 3, two pumps of large capacity and small capacity are used as described above, and the large capacity pump is driven only when the vehicle is stopped or at low speeds, and the large capacity pump is stopped and the small capacity pump is operated while the vehicle is running at medium or high speeds. Since only the capacity pump is driven, (the small capacity pump may be driven by a belt that follows the rotation of the engine, but it is convenient to control it by directly connecting it to the electric motor instead of being driven by a belt as in the example). ) The driving power of the power steering device is significantly reduced. Furthermore, it goes without saying that the small capacity pump may be of the type directly connected to the engine and driven all the time as described above.

As described above, a large-capacity pump and a small-capacity pump are arranged in parallel, and the pressure fluid discharged from the large-capacity pump provides steering assistance when the vehicle is stationary and when running at very low speeds, and when accelerating or driving at medium or high speeds. By stopping the drive of the large-capacity pump and activating only the small-capacity pump to obtain the required steering assistance and reaction force, light steering force is achieved during stationary steering operations and at extremely low speeds. is obtained, and when accelerating,
A stable steering feel can be obtained during medium and high speed driving, and the driving force of the power steering device, that is, the engine load, can be significantly reduced during acceleration and medium and high speed driving, thereby preventing energy loss.

Figure 5 shows the driving horsepower of the power steering device on the vertical axis.
FIG. 2 is a diagram showing changes in drive horsepower with increase in vehicle speed of a conventional power steering device B and a power steering device A of the present invention, with PS and vehicle speed S on the horizontal axis,
This figure also proves a significant reduction in energy loss.

The above describes a power steering device that connects and disconnects the driving force of a large-capacity pump using an electromagnetic clutch. In particular, the driving force of the large-capacity pump can be connected or disconnected using a friction plate clutch that operates in response to changes in the hydraulic pressure supplied to the power control valve, that is, changes in steering torque.

In FIG. 6, 40 is a steering handle;
The steering gear device includes a hydraulic cylinder 41 such as a rack cylinder and a power control valve 42.
Equipped with Reference numeral 43 is an engine, and an engine crank pulley 15 is attached to its output shaft, and belt drives a friction plate clutch 50, which will be described later. 44
is a fluid pressure passage that applies fluid pressure to the power control valve 42 to control the engagement and disengagement of the friction plate clutch 50.

As shown in FIG. 7, the friction plate clutch 50 includes a pulley 51 driven by a belt to the engine crank pulley 15, friction plates 52 disposed on both sides of the pulley 51, and a flange portion 5 in contact with one of the friction plates 52.
3, and a key 55 is attached to the shaft 54 of the large capacity pump 12.
The shaft boss 56 and the other friction plate 5 are fixed via the
A cylinder 58 is integrally fixed to the housing of the large-capacity pump 12 and rotatably and slidably engages the plunger 57.
By supplying pressure fluid to the cylinder 58 and clamping the friction plate 52 and the pulley 51 between the plunger 57 and the flange portion 53 of the shaft boss 56, the clutch is connected and the engine 43 is started. The driving force is transferred to the shaft 5 of the large capacity pump 12.
4 to drive the pump 12. Then, fluid pressure to the power control valve 42 is introduced into the cylinder 58 through the fluid pressure passage 44, and the plunger 57 is operated.

Now the ignition key switch (not shown)
When turned on, the switch of the small electric motor 25 is turned on in conjunction, and the electric motor 25 starts rotating to drive the small capacity pump 13. By driving the pump 13, the fluid in the reservoir tank 16 is transferred to the hydraulic circuit 26.
through the power control valve 42, the hydraulic cylinder 41, and the cylinder 58 of the friction plate clutch 50.
The circulating fluid and excess pressure fluid are returned to the reservoir tank 16. Small capacity pump 1
The hydraulic pressure discharged from the cylinder 58 is so low that it does not have enough force to urge the plunger 57 of the cylinder 58 toward the friction plate 52. Therefore, even if the engine is driven and the crank pulley 15 rotates, the pulley 51 driven by the belt idles and the large capacity pump 12 remains stopped.

When the handle 40 is started to be operated in this state, the hydraulic pressure inside the power control valve 42 increases as the steering resistance increases due to the small capacity pump 13 continuing to discharge pressurized fluid, and the hydraulic cylinder 41 control of the pressure fluid to start steering force assistance.

As a result, the fluid pressure in the hydraulic circuit for the power control valve 42 also increases, and pressure fluid is supplied to the cylinder 58 of the friction plate clutch 50 via the fluid pressure passage 44, urging the plunger 57 toward the friction plate 52. , increases the clamping pressure on the friction plate 52 and the pulley 51 between the shaft boss 56 and the flange portion 53.

When the clamping pressure exceeds a certain value due to an increase in fluid pressure, the clutch becomes connected, and the rotational force transmitted to the pulley 51 causes the shaft 5 of the large capacity pump 12 to
Start driving 4. That is, from this stage, the discharge pressure fluid of the large capacity pump 12 is supplied to the hydraulic cylinder 41 via the power control valve 42.
Full-scale steering power assistance, or power assist, begins.

When power assist is started, the more the fluid pressure in the hydraulic circuit increases, the more the friction plate 52 and pulley 5
1 increases, the torque transmission ratio from the pulley 51 to the shaft boss 56 increases, and the pulley 51 is prevented from idling.

In order to prevent this clamping pressure from becoming excessive, a cut valve 60 as shown in FIG. The plunger 61 may be actuated to move the plunger 61 to the left against the bias of the spring 62, thereby cutting off the supply of pressure fluid to the cylinder 58.

When the handle operation is completed, the fluid pressure in the power control valve 42 decreases, so the fluid pressure in the fluid pressure passage 44 also decreases. Therefore, the friction plate 52,
The clamping pressure on the pulley 51 also decreases, and when the clamping pressure reaches a certain value or less, the pulley 51 begins to idle.
The clutch becomes disengaged and the rotation of the large capacity pump 12 stops.

A pressure switch 35 as shown in FIG. 7 is provided in the fluid pressure passage 44, and the electric motor 25 is stopped by a signal from the switch 35 via the control device 36 just before the fluid pressure increases and the clutch is connected. , the drive of the small capacity pump 13 is stopped, and on the other hand, just before the clutch shifts from the connected state to the disconnected state, the electric motor 25 is started via the control device 36 in response to a signal from the pressure switch 35, and the small capacity pump 13 is driven. By doing so, it is possible to avoid wasting energy while the large capacity pump 12 is operating.

Furthermore, control signals for starting and stopping the small capacity pump can be similarly obtained using a vehicle speed sensor that is activated by detecting changes in vehicle speed.

In other words, in this embodiment, the large-capacity pump is operated only when the steering wheel is operated in a state that requires power assist when stopped or when driving at low speeds, so it is activated only when the steering wheel is operated in a state that requires power assist. Compared to conventional systems that drive large-capacity pumps, the pump's driving force can be significantly reduced, reducing engine load and achieving energy savings.Friction plates that use hydraulic pressure Since a clutch is used, responsiveness in torque transmission can be fully demonstrated, and heat generation caused by friction plate slippage can be greatly reduced. Furthermore, by simply adding a friction plate clutch and a small-capacity pump to a conventional power steering device, conventional power control valves, large-capacity pumps, etc. can be used as they are, making it easy to improve conventional devices. It is.

As detailed above, according to the present invention, various excellent effects as listed below can be obtained, and the steering gear device hardly requires power assist when the automobile is accelerating or driving at high to medium speeds. It is possible to provide a power steering device that significantly reduces the driving power of the power steering device between the two, thereby significantly reducing energy consumption.

(1) The pump means for circulating the pressure fluid is
This system is composed of a large-capacity pump and a small-capacity pump arranged in parallel, and the operation of both pumps is controlled by a control device in response to changes in the operating conditions of the vehicle, which is extremely advantageous in terms of energy saving.

That is, under operating conditions that require steering force assistance, the large-capacity pump is driven to supply pressurized fluid to the steering gear device, while under operating conditions that require little steering force assistance, Since the small capacity pump is driven to supply pressure fluid to the steering gear device, these two types of pumps, large capacity and small capacity, are used to control changes in vehicle speed, engine speed, and steering control. The resistors and the like can be used very efficiently and the loss of energy consumption can be reduced as much as possible.

(2) A power connection/disconnection mechanism that connects/disconnects the rotational force of the engine is provided in the drive section of the large-capacity pump, and
When the power connection/disconnection mechanism is connected/disconnected, the discharge amount of the large-capacity pump is set to almost zero, so that the change in the flow rate of the pressure fluid when the large-capacity pump is connected/disconnected is minimized. A continuous fluid supply curve is obtained throughout the range, medium speed range and high speed range.

Therefore, even if the large-capacity pump stops, there is no sudden change in the steering feeling, and a stable steering feeling can be obtained over the entire range of travel speeds.

(3) The pumping means includes a small-capacity pump, and is configured such that under operating conditions that require little steering force assistance, the large-capacity pump is not activated and only the small-capacity pump is driven. Therefore, when little steering force assistance is required, the power steering device can be driven with only a small-capacity electric motor, making it possible to configure a compact and easily controllable system.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing a conventional power steering device, Fig. 2 is a diagram showing the relationship between the rotation speed of the pump and its driving horsepower, and Fig. 3 is a system diagram showing an embodiment of the present invention. Figure 4 is a diagram showing the relationship between the engine speed and the amount of fluid supplied to the power steering servo valve, Figure 5 is a diagram showing the relationship between vehicle speed and the driving horsepower of the power steering device, and Figure 6 is a diagram showing the relationship between the engine speed and the amount of fluid supplied to the power steering servo valve. A system diagram showing an example;
FIG. 7 is a sectional view showing an example of a friction plate clutch, and FIG. 8 is a sectional view showing a cut-off valve. 10, 41...Hydraulic cylinder, 11...Power steering servo valve (power control valve), 42
...Power control valve, 12...Large capacity pump, 13...Small capacity pump, 14...Electromagnetic clutch, 15...Engine crank pulley, 16
...Reservoir tank, 17...Hydraulic circuit, 18
... Throttle, 19 ... Flow rate control valve, 20 ... Relief valve, 21 ... Check valve, 22 ... Power supply battery,
25... Electric motor, 26... Hydraulic circuit, 27... Check valve, 28... Throttle, 29... Relief valve,
33...Vehicle speed sensor, 34...Engine speed sensor, 35...Circuit pressure sensor (pressure switch), 36...Control device, 37...Reaction chamber, 44
...Fluid pressure passage, 50...Friction plate clutch, 51
...Pulley, 52...Friction plate, 54...Shaft, 56
...Shaft boss, 57...Plunger, 58...Cylinder, 60...Cut valve.

Claims (1)

[Scope of Claims] 1. A power steering device that assists steering power by providing a pump means for supplying pressure fluid to a steering gear device equipped with a power assist mechanism and circulating the pressure fluid to a reservoir tank, comprising: The pump means is constituted by a large capacity pump and a small capacity pump arranged in parallel, and a hydraulic circuit from the large capacity pump to the steering gear device and a hydraulic circuit from the small capacity pump to the steering gear device, respectively. , a check valve for preventing backflow of pressure fluid is provided, a power connection/disconnection mechanism for connecting/disconnecting the rotational force of the engine is provided in the drive section of the large capacity pump, and the operation of the power connection/disconnection mechanism and the small capacity pump is controlled. A control device is installed that detects and controls changes in vehicle operating conditions, and under operating conditions that require steering force assistance,
The large-capacity pump is driven to supply pressure fluid to the steering gear device, while the small-capacity pump is driven to supply pressure fluid to the steering gear device under operating conditions that require little steering force assistance. A power steering device, characterized in that: when the power connection/disconnection mechanism is connected/disconnected, the discharge amount of the large capacity pump is set to approximately zero to reduce a change in the flow rate of the pressure fluid. . 2. The power connection/disconnection mechanism is configured with an electromagnetic clutch, and the small capacity pump is driven by an electric motor powered by a power source battery, and the control device is configured to monitor the operation status of the vehicle by a vehicle speed sensor, an engine, etc. Claims include an electric control device that controls the operation of the electromagnetic clutch and the electric motor of the small capacity pump by detecting an electric signal from one or more of a rotation speed sensor, a circuit pressure sensor, and a steering torque sensor. 1. The power steering device according to 1. 3. The power connection/disconnection mechanism is operated by fluid pressure generated by the operation of a power assist mechanism and a friction plate clutch provided in the drive section of the large capacity pump, and the increase in fluid pressure connects the friction plate clutch. 2. The power steering device according to claim 1, further comprising: a fluid pressure cylinder that disconnects said friction plate clutch due to a decrease in fluid pressure. 4. The small capacity pump is to be driven by an electric motor using a power battery as a driving source, and the control device is configured to detect the operation status of the vehicle by an electric signal from one or more of a vehicle speed sensor, a circuit pressure sensor, and a steering torque sensor. 4. The power steering device according to claim 3, wherein the power steering device is an electric control device that controls the electric motor by detecting the power. 5. The power steering device according to any one of claims 1 to 4, wherein fluid pressure of the discharge pressure fluid of the small capacity pump is applied to a reaction force mechanism of the power steering device.