JP2530371B2 - Suspension control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Use] The present invention relates to a suspension control device used in a vehicle, and more particularly to a vehicle that includes a sensor for detecting the vehicle height at each wheel position and detects the detected vehicle height. The present invention relates to a suspension control device that performs suspension control according to high information.

[Prior Art] In the device disclosed in Japanese Patent Laid-Open No. 63-269709, a vehicle height of a control amount of a suspension detected by a vehicle height sensor, a differential value of the vehicle height, and a vertical acceleration detected by an acceleration sensor. It is determined according to the value obtained by adding each component of.

[Problems to be Solved by the Invention] For example, in a suspension control device including a vehicle height sensor and performing suspension control according to the detection result of the vehicle height sensor as in Japanese Patent Laid-Open No. 63-269709, a circuit is provided in the vehicle height sensor. When a short circuit or an open abnormality occurs, the detected vehicle height becomes 0 or the full-scale vehicle height, so the detected vehicle height error becomes extremely large and the vehicle height changes abruptly. That is, even when the actual vehicle height matches the target vehicle height, the differential component corresponding to the detected vehicle height change, for example, the difference between the previously detected vehicle height and the vehicle height detected this time is temporarily abnormal. Since the value becomes large, the control amount of the pressure control system increases corresponding to the differential component, and a shock is transmitted to the occupant due to a change in suspension pressure, that is, a change in vehicle height.

If the control gain for the differential component is reduced,
Although the shock due to the abrupt vehicle height change described above can be reduced, the followability of suspension control for a rapid vehicle height change is deteriorated.

The present invention, when an abnormality occurs in the means for detecting the vehicle height,
An object of the present invention is to provide a suspension control device that prevents a shock from appearing and that has a good high-speed response.

[Configuration of the Invention] [Means for Solving the Problems] In order to solve the above problems, in the present invention, a suspension mechanism including an actuator that expands and contracts according to the supply and discharge of hydraulic oil; Vehicle height detecting means for detecting changes; pressure source means for supplying hydraulic oil to the actuator; adjusting valve means for controlling supply / discharge of hydraulic oil from the pressure source means to the actuator;
The value of the detected vehicle height detected by the vehicle height detecting means is passed through a digital filter process to remove a predetermined high frequency change component, and based on the difference between the processing result and the control target value, at least a proportional term and Feedback control means for calculating a control amount for making the difference substantially zero by a feedback calculation including a differential term, and adjusting the adjusting valve means accordingly; and identifying whether or not there is an abnormality in the vehicle height detecting means, An electronic control unit is provided which adjusts the parameters of the digital processing when the presence of an abnormality is identified and lowers the cutoff frequency of the filter processing as compared with the normal case.

[Operation] By passing the detected value through the digital filter that constitutes the low-pass filter, it is possible to suppress a high-frequency change component of the detected value, that is, a rapid change in the detected value. Therefore, by performing control according to the error between the result passed through the filter and the target value, the change in the error becomes gradual.
Therefore, when the cut-off frequency of the filter is low, the amount of attenuation of the differential value of the error due to the filter is large, thereby preventing an abnormally large differential value from being generated, and abrupt control pressure change is avoided.

In the present invention, when the abnormality of the vehicle height detecting means is detected, the cutoff frequency of the filter is lowered as compared with the normal state, so that the attenuation amount of the differential component by the filter becomes larger than that in the normal state. Therefore, even if a sudden change occurs in the vehicle height detection value due to the open or short circuit of the vehicle height sensor, the change is smoothed by passing the filter, and the differential component is prevented from becoming abnormally large.
The occurrence of shock due to sudden changes in vehicle height is avoided.

By the way, for example, when the vehicle height sensor outputs vehicle height information in the form of an analog signal, by inserting an analog filter circuit (low-pass filter) between the output of the vehicle height sensor and the A / D converter. It is possible to reduce the shock generated when an abnormality occurs in the vehicle height sensor. However, in that case, even when trying to perform independent attitude control for each attitude element by obtaining the detection values of each of the attitude elements based on the plurality of vehicle height information obtained from the plurality of vehicle height sensors, Since the change speed of the detected value for the posture element of 1 is determined by the characteristics of the same analog filter, the response speed of the posture control is set to be the same for any posture element. However, it is preferable to set the response speed to the optimum condition for each posture element.

In the present invention, since the detected value is subjected to digital filter processing, even when a plurality of vehicle height sensors are used to detect a plurality of vehicle height postures, the characteristics of the filter can be switched for each determined posture element. Therefore, the optimum response speed can be obtained for each posture element.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[Embodiment] FIG. 1 shows an outline of a mechanical portion of a vehicle suspension device embodying the present invention. The hydraulic pump 1, which is a radial pump, is arranged in the engine room, is connected to the drive output of an on-vehicle engine (not shown) by a belt, and when driven to rotate, sucks oil from the reservoir 2 to a predetermined level or more. The oil is discharged into the high-pressure port 3 at a predetermined flow rate at the rotation speed of.

The high pressure port 3 of the suspension pump radial pump is connected to the pulsation absorbing accumulator 4, the main check valve 50 and the relief valve 60m.
High-pressure oil from the high-pressure port 3 is supplied to the high-pressure supply pipe 8 through the main check valve 50.

The main check valve 50 prevents the reverse flow of oil from the high pressure supply pipe 8 to the high pressure port 3 when the pressure of the high pressure port 3 is lower than the pressure of the high pressure supply pipe 8.

When the pressure of the high-pressure port 3 becomes equal to or higher than a predetermined pressure, the relief valve 60m allows the high-pressure port 3 to flow through a reservoir return pipe 11, which is one of the oil return paths to the reservoir 2, to substantially reduce the pressure of the high-pressure port 3. Maintain the upper constant pressure.

The high pressure charge pipe 8, the front wheel suspension 100f _L, a front wheel high pressure feed pipe 6 for supplying a high voltage to 100FR, rear suspension 100r _L, the wheel high pressure charge tube 9 after for supplying a high voltage to 100rr communicated An accumulator 7 (for front wheels) is provided on the front wheel high-pressure supply pipe 6, and an accumulator is provided on the rear wheel high-pressure supply pipe 9.
10 (for rear wheels) is in communication.

A pressure control valve 80fr is connected to the front wheel high pressure supply pipe 6 via an oil filter, and the pressure control valve 80fr changes the pressure of the front wheel high pressure supply pipe 6 (hereinafter referred to as front wheel line pressure) to a required pressure (electricity thereof). Pressure corresponding to the current flowing through the coil: Suspension support pressure) is adjusted (reduced) to cut valve 70fr
And give to the relief valve 60fr.

The cut valve 70fr is provided with the output port 84 (to the suspension) of the pressure control valve 80fr and the suspension 10 when the pressure of the front wheel high pressure supply pipe 6 (front wheel side line pressure) is lower than a predetermined low pressure.
0fr shock absorber 101fr hollow piston rod 10
2fr is cut off to prevent pressure loss from the piston rod 102fr (shock absorber 101fr) to the pressure control valve 80fr, and the output pressure of the pressure control valve 80fr is maintained while the front wheel side line pressure is higher than a predetermined low pressure. (Suspension support pressure) is directly supplied to the piston rod 102fr.

The relief valve 60fr limits the internal pressure of the shock absorber 101fr to the upper limit value or less. That is, the pressure control valve 80
When the pressure of the output port 84 of fr (suspension support pressure) exceeds a predetermined high pressure, the output port 84 is set to the reservoir return pipe.
As a flow through 11, the pressure of the output port of the pressure control valve 80fr is maintained substantially below a predetermined high pressure. Further, the relief valve 60fr serves to buffer the propagation of this impact to the pressure control valve 80fr when the inner pressure of the shock absorber 101fr rises due to the impact of pushing up the front right wheel from the road surface, and the shock absorber 101fr. When the internal pressure of the shock absorber rises, the internal pressure of the shock absorber 101fr is discharged to the reservoir return pipe 11 via the piston rod 100fr and the cut valve.

The suspension 100fr is roughly composed of a shock absorber 101fr and a suspension coil spring 119fr. The pressure supplied to the shock absorber 101fr via the output port 84 of the pressure control valve 80fr and the piston rod 102fr (pressure control). The body is supported at a height (relative to the front right wheel) corresponding to the pressure regulated by the valve 80fr: suspension support pressure.

The support pressure applied to the shock absorber 101fr is detected by the pressure sensor 13fr, and the pressure sensor 13fr generates an analog signal indicating the detected support pressure.

A vehicle height sensor 1 is installed on the vehicle body near the suspension 100fr.
5fr is installed, and the link connected to the rotor of the vehicle height sensor 15fr is connected to the front right wheel. The vehicle height sensor 15fr generates an electric signal (digital data) indicating the vehicle height of the front right wheel portion (height of the vehicle body with respect to the wheel).

Similar to the above, pressure control valve 80f _L , cut valve 70f _L ,
Relief valve 60f _L , vehicle height sensor 15f _L and pressure sensor
Similarly, 13f _L is assigned to the suspension 100f _L on the front left wheel, and the pressure control valve 80f _L is connected to the front wheel high pressure supply pipe 6 to provide a required pressure (supporting pressure) to the suspension 100f _L. Shock absorber 101f _L of piston rod 102f _L of.

Similar to the above, pressure control valve 80rr, cut valve 70rr, relief valve 60rr, vehicle height sensor 15rr and pressure sensor 13r
Similarly, r is assigned to the suspension 100rr of the rear right wheel, and is equipped, and the pressure control valve 80rr is connected to the rear wheel high pressure supply pipe 9 to provide a required pressure (support pressure) to the shock absorber of the suspension 100rr. 101rr piston rod 10
Give to 2rr.

Further, as described above, the pressure control valve 80r _L and the cut valve 70
r _L, relief valve 60r _L, height sensors 15r _L and the pressure sensor 13r _L is likewise suspension of the front left wheel portion 100r
_The pressure control valve 80r _L is connected to the rear wheel high pressure supply pipe 9 to provide a required pressure (supporting pressure) to the piston rod 102r _L of the shock absorber 101r _L of the suspension 100r _L.

In this embodiment, the engine is mounted on the front wheel side, and accordingly, the hydraulic pump 1 is mounted on the front wheel side (engine room), and the pipe length from the hydraulic pump 1 to the rear wheel suspension 100rr, 100r _{L is} reduced. It is longer than the piping length from the hydraulic pump 1 to the front wheel side suspension 100fr, 100f _L. Therefore, the pressure drop due to the pipe line is large on the rear wheel side, and if oil leakage occurs in the pipe, the pressure drop on the rear wheel side is the largest. So, in the rear wheel high pressure supply pipe 9,
The pressure sensor 13rm for line pressure detection is connected. On the other hand, the pressure of the reservoir return pipe 11 is the lowest at the end on the reservoir 2 side, and the pressure tends to increase as the distance from the reservoir 2 increases. Therefore, the pressure of the reservoir return pipe 11 is also on the rear wheel side, and the pressure sensor 13rt is used. I try to detect.

A bypass valve 120 is connected to the rear wheel high pressure supply pipe 9. The bypass valve 120 regulates the pressure of the high pressure supply pipe 8 (obtains a required line pressure) to a pressure corresponding to the value of the electric current flowing through the electric coil. Further, when the ignition switch is opened (engine stop: pump 1 stop), the line pressure is set to substantially zero (the atmospheric pressure of the reservoir 2 through the reservoir return pipe 11) (this line pressure decrease causes the cut valve 70fr , 70f _L , 70rr, 70r _L
Is turned off to prevent pressure loss from the shock absorber) and reduce the load when the engine (pump 1) is restarted.

Fig. 2 shows an enlarged vertical section of the suspension 100fr. The piston 103 fixed to the piston rod 102fr of the shock absorber 101fr is arranged in the inner cylinder 104 in the upper chamber 10 roughly.
It is divided into 5 and lower chamber 106. Suspension support pressure (hydraulic pressure) is supplied to the piston rod 102fr from the output port of the cut valve 70fr.
It joins the upper chamber 105 in the inner cylinder 104 through the side port 107 of 02fr, and further through the vertical through port 108 of the piston 103, the lower chamber 10
Join 6 A supporting pressure proportional to the product of this pressure and the cross-sectional area of the piston rod 102fr (square of rod radius × π) is applied to the piston rod 102fr.

The lower chamber 106 of the inner cylinder 104 communicates with the lower space 110 of the damping valve device 109. The upper space of the damping valve device 109 is divided into a lower chamber 112 and an upper chamber 113 by a piston 111, and the oil in the lower space 110 flows through the lower chamber 112 through the damping valve device 109. Is filled with a high pressure gas.

When the piston rod 102fr relatively attempts to rapidly enter below the inner cylinder 104 due to the push-up of the front right wheel,
The internal pressure of the inner cylinder 104 suddenly rises, and similarly the pressure of the lower space 110 tends to suddenly become higher than the pressure of the lower chamber 112. At this time, the damping valve device 109 allows the oil to flow from the lower space 110 to the lower chamber 112 at a predetermined pressure difference or more, but prevents the oil from flowing in the reverse direction. From lower chamber 112
Flow, the piston 111 rises and buffers the impact (upward) applied from the wheel to the piston rod 102fr. That is, wheel impact on the vehicle body (upward thrust)
Is propagated.

When the piston rod 102fr relatively tries to come out above the inner cylinder 104 due to the sudden fall of the front right wheel, the inner cylinder
The internal pressure of 104 suddenly lowers, and similarly the pressure of the lower space 110 tries to suddenly become lower than the pressure of the lower chamber 112. At this time, the damping valve device 109 allows the oil to flow from the lower chamber 112 to the lower space 110 at a predetermined pressure difference or more, but prevents the oil from flowing in the reverse direction. To the lower space 110, whereby the piston 111 descends and buffers the impact (downward) applied from the wheel to the piston rod 102fr. That is, the propagation of the wheel impact (falling down) to the vehicle body is buffered.

In addition, shock absorber 101f
As the pressure applied to r rises, the pressure in the lower chamber 112 rises, the piston 111 rises, and the piston 111 comes to a position corresponding to the vehicle body load.

When there is no vertical movement of the piston rod 102fr relative to the inner cylinder 104, such as during parking, the seal between the inner cylinder 104 and the piston rod 102fr substantially prevents oil from leaking from the inner cylinder 104 into the outer cylinder 114. There is no. However, in order to reduce the vertical movement load of the piston rod 102fr, the seal has a sealing characteristic such that a slight oil leak occurs when the piston rod 102fr moves up and down. The oil leaked to the outer cylinder 114 passes through the outer cylinder 114,
It is returned to the reservoir 2 through a drain 14fr (Fig. 1) for releasing the atmosphere and a drain return pipe 12 (Fig. 1) which is a second return pipe. The reservoir 2 is equipped with a level sensor 28 (Fig. 1),
Generates a signal (oil shortage signal) indicating this when the oil level in the reservoir 2 is equal to or lower than the lower limit value.

The structures of the other suspensions 100f _L , 100rr and 100r _L are substantially the same as the structure of the suspension 100fr described above.

FIG. 3 shows an enlarged vertical cross section of the pressure control valve 80fr. The sleeve 81 has a spool accommodating hole formed in the center thereof, and a ring-shaped groove 83 communicating with the line pressure port 82 and a ring-shaped groove 86 communicating with the low pressure port 85 are formed on the inner surface of the spool accommodating hole. Has been done. These ring-shaped grooves 83
Output port 84 is open in the middle between and 86. Spool 90 inserted in the spool storage hole, in the middle of its side peripheral surface,
A ring-shaped groove 91 having a width corresponding to the distance between the right edge of the groove 83 and the left edge of the groove 86 is provided. A valve housing hole is formed at the left end of the spool 90, and the valve housing hole communicates with the groove 91. The valve body 93 pushed by the compression coil spring 92 is inserted into the valve housing hole. This valve body 93 has a through orifice in the center, and this orifice communicates the space of the groove 91 (output port 84) with the space accommodating the valve body 93 and the compression coil spring 92. Therefore, the spool 90 receives the pressure of the output port 84 (regulated pressure to the suspension 100fr) at the tip thereof, and thereby receives the force that is driven to the right. Incidentally, when the pressure of the output port 84 is increased by impact, the valve body 93 moves to the left against the pressing force of the compression coil spring 92 and creates a buffer space at the right end of the valve body 93. When the output port 84 rises suddenly, this shocking upward pressure does not immediately apply to the left end face of the spool 90, but
Has an effect of buffering the rightward movement of the spool 90 against a sudden increase in pressure of the output port 84. On the contrary, it exerts a function of buffering the leftward movement of the spool 90 against the shocking pressure drop of the output port 84.

The pressure of the target pressure space 88 communicating with the high pressure port 87 via the orifice 88f is applied to the right end surface of the spool 90, and this pressure causes the spool 90 to receive a force to be driven to the left. The high pressure port 87 is supplied with a line pressure. The target pressure space 88 communicates with the low pressure port 89 through a flow path 94, and a flow opening of the flow path 94 is defined by a needle valve 95.
When the needle valve 95 closes the flow path 94, the orifice 88
The pressure of the target pressure space 88 communicating with the high pressure port 87 via f becomes the pressure (line pressure) of the high pressure port 87,
90 is driven to the left, so that the groove 91 of the spool 90 communicates with the groove 83 (line pressure port 82), and the groove 91 (output port
The pressure of 84) rises and this is transmitted to the left side of the valve body 93, and the right driving force is given to the left end of the spool 90. When the needle valve 95 fully opens the flow path 94, the pressure in the target pressure space 88 becomes
Since it is throttled by the orifice 88f, it is significantly lower than the pressure (line pressure) of the high pressure port 87, and the spool 90 moves to the right, whereby the groove 91 of the spool 90 communicates with the groove 86 (low pressure port 85). The pressure in the groove 91 (output port 84) is reduced, and this is transmitted to the left side of the valve body 93, and the right driving force at the left end of the spool 90 is reduced. In this way, the spool 90
This is a position where the pressure in the target pressure space 80 and the pressure in the output port 84 are balanced. That is, a pressure that is substantially proportional to the pressure in the target pressure space 88 appears at the output port 84.

The pressure in the target pressure space 88 is determined by the position of the needle valve 95, and since this pressure is substantially inversely proportional to the distance of the needle valve 95 with respect to the flow path 94, the output port 84 eventually has a substantial distance to the distance of the needle valve 95. Inversely proportional pressure appears.

The needle valve 95 penetrates the fixed core 96 made of a magnetic material.
The right end of the fixed core 96 is frustoconical, and the end face of the magnetic plunger 97 having a bottomed conical hole faces the right end face. The needle valve 95 is fixed to the plunger 97. The fixed core 96 and the plunger 97 enter inside the bobbin around which the electric coil 99 is wound.

When the electric coil 99 is energized, magnetic flux flows in the loop of the fixed core 96-magnetic material yoke 98a-magnetic material end plate 98b-plunger 97-fixed core 96, and the plunger 97 is attracted to the fixed core 96 and moves to the left. Then, the needle valve 95 approaches the flow path 94 (the distance becomes shorter). By the way, the left end of the needle valve 95 receives the pressure in the target pressure space 88 as a right driving force,
Since the right end of 95 is the atmospheric pressure through the low pressure port 98c of the atmosphere release, the needle valve 95 is driven by the pressure of the target pressure space 88 to the right drive corresponding to its pressure value (this corresponds to the position of the needle valve 95). Under the influence of force, the needle valve 95 is eventually connected to the flow path 94.
On the other hand, the distance is substantially inversely proportional to the current value of the electric coil 99. In order to make the relationship between the current value and the distance linear, as described above, one of the fixed core and the plunger has a truncated cone shape, and the other has a bottomed conical hole shape corresponding thereto.

As a result, a pressure that is substantially proportional to the value of the current flowing through the electric coil 99 appears at the output port 84. The pressure control valve 80fr outputs, to the output port 84, a pressure proportional to an energizing current within a predetermined range.

FIG. 4 shows an enlarged vertical cross section of the cut valve 70fr. A line pressure port 72, a pressure adjusting input port 73, an oil discharge port 74, and an output port 75 are in communication with the valve housing hole formed in the valve base 71. The line pressure port 72 and the pressure adjusting input port 73 are separated by a ring-shaped first guide 76, and the pressure adjusting input port 73 and the output port 75 are separated from each other by a cylindrical guide 77a,
Separated by 77b and 77c. The oil drain port 74 is the second
The second guide 77 communicates with the ring-shaped groove on the outer periphery of the guide 77c.
a, 77b and 77c to return oil
Return to.

A spool 78 pushed leftward by a compression coil spring 79 passes through the first and second guides 76 and 77a to 77c, and a line pressure is applied to the left end surface of the spool 78. The guide hole of the central projection of the second guide 77c, into which the left end of the spool 78 has entered, communicates with the return conduit 11 through the ring-shaped groove on the outer periphery of the second guide 77c and the oil discharge port 74. When the line pressure is less than the predetermined low pressure, as shown in FIG. 4, the spool 78 is driven to the leftmost side by the repulsive force of the compression coil spring 79, and the spool 78 is provided between the output port 75 and the pressure adjusting input port 73. Is closed by fully closing the inner opening of the second guide 77a. When the line pressure becomes equal to or higher than a predetermined low pressure, the spool 79 starts to be driven rightward against the repulsive force of the compression coil spring 79 by this pressure, and the spool 79 is located at the rightmost position (fully opened) at a pressure higher than the predetermined low pressure. . That is, when the spool 78 moves to the right of the inner opening of the second guide 77a, the pressure adjusting input port 73 communicates with the output port 75, and the line pressure (line pressure port 72) rises to a predetermined low pressure, the cut valve 70fr becomes , Pressure adjusting input port 73 (Pressure control valve
80fr pressure regulating output) and output port 75 (shock absorber)
When the line pressure (port 72) further rises after starting the flow between the pressure control input port 73 (pressure control output of the pressure control valve 80fr) and the output port 75 (shock absorber 101f).
Fully open between r). When the line pressure drops,
Conversely, when the line pressure becomes lower than the predetermined low pressure, the output port 75 (shock absorber 101fr) is completely shut off from the pressure adjusting input port 73 (pressure adjusting output of the pressure control valve 80fr).

FIG. 5 shows an enlarged vertical cross section of the relief valve 60fr.
An input port 62 and a low pressure port 63 are opened in the valve housing hole of the valve base 61. A cylindrical first guide 64 and a second guide 67 are inserted in the valve housing hole, and the input port 62 communicates with the inner space of the first guide 64 through the filter 65. A valve body 66 having an orifice at its center is inserted into the first guide 64, and the valve body 66 is pushed to the left by a compression coil spring 66a. The space of the first guide 64 accommodating the valve body 66 and the compression coil spring 66a passes through the orifice of the valve body 66, and the input port.
62, and through the opening of the spring seat 66b,
It communicates with the inner space of the second guide 67. Conical valve body 68
Is pushed to the left by the repulsive force of the compression coil spring 69,
The opening of the spring seat 66b is closed. When the pressure (control pressure) of the input port 62 is less than the predetermined high pressure, the pressure of the coil spring 66a storage space communicating with the input port 62 through the orifice of the valve body 66 is relatively higher than the repulsive force of the compression coil spring 69. Since it is low, the valve body 68 closes the central opening of the valve seat 66b, as shown in FIG. 5, and therefore the output port 62 is in communication with the low pressure port 63 through the hole 67a. It is cut off from the space. That is, the output port 62 is cut off from the low pressure port 63.

When the pressure (control pressure) of the input port 62 rises to a predetermined high pressure, this pressure is applied to the central opening of the valve seat 66b through the orifice of the valve body 66, the valve body 68 starts to be driven right by this pressure, and the input port 62 When the pressure further rises, the valve element 68 is driven to the right. That is, the pressure at the input port 62 is
It is discharged to the low pressure port 63, and the control pressure is suppressed below a predetermined high pressure.

If a high pressure is applied to the input port 62 due to shock, the valve body
66 is driven right, and the input port 62 is the side opening of the first guide 64.
It communicates with the bubble storage space of the base body 61 through 64a and communicates with the low pressure port 63. Since this flow passage area is large, a sudden pressure increase (pressure impact) of the output port 62 is buffered.

FIG. 6 shows an enlarged vertical cross section of the main check valve 50. An input port 52 and an output port 53 are communicated with a valve housing hole formed in the bubble base body 51. A cylindrical valve seat 54 with a bottom is housed in the valve housing hole, and a flow valve 55 of the valve seat 54 is pressed by a compression coil spring 56 to a ball valve 57.
Is closed, but when the pressure at the input port 52 is higher than the pressure at the output port 53, the ball valve 57 is pushed to the right by the pressure at the input port 52 to open the passage port 55. Ie input port
Oil flows from 52 to the output port 53. However, when the pressure at the output port 53 is higher than the pressure at the input port 52, the ball valve 57 closes the flow port, so that oil does not flow from the output port 53 toward the input port 52.

FIG. 7 shows an enlarged vertical cross section of the bypass valve 120.
The input port 121 communicates with the inner space of the first guide 123, and the valve body 124a pushed leftward by the compression coil spring 124b is housed in the inner space. The valve body 124a has an orifice at the center of the left end face, and the input port 121 communicates with the inner space of the first guide 123 through this orifice. The internal space communicates with the low pressure port 122 through the flow path 122b, and the flow path 122b is opened and closed by the needle valve 125.

The solenoid device composed of the needle valve 125 to the electric coil 129 has the same structure and the same size as the solenoid device composed of the needle valve 95 to the electric coil 99 shown in FIG. 3 (designed commonly for the pressure control valve and the bypass valve). And the orifice
The distance of the needle valve 125 with respect to 122b is substantially inversely proportional to the value of the current flowing through the electric coil 129. Since the flow opening of the orifice 122b is inversely proportional to this distance, the oil flow rate from the input port 121, through the orifice of the valve element 124a, through the inner space of the first guide 123, through the orifice 122b, and out to the low pressure port 122 is , Is proportional to the differential pressure across the orifice on the left end surface of the valve body 124a.

As a result of the above, the pressure at the input port 121 is
The pressure is substantially proportional to the value of the energizing current. This bypass valve 120 changes the pressure (line pressure) of the input port 121 to
The applied current is within a predetermined range and the pressure is proportional to it.
Further, when the ignition switch is off (the engine is stopped: the pump 1 is stopped), the energization of the electric coil 129 is stopped, so that the needle valve 125 moves to the rightmost position.
The input port 121 (line pressure) becomes a low pressure near the return pressure.

When the pressure in the input port 121 rises explosively,
The valve body 124a is driven rightward by receiving this pressure on the left end face, and the low pressure port 122a communicating with the low pressure port 122 communicates with the input port 121. Since the low pressure port 122a is a relatively large opening, the shocking rising pressure of the input port 21 immediately escapes to the low pressure port 122a.

The relief valve 60m has the same structure as the relief valve 60fr described above, but has a conical valve body (68: fifth
The compression coil spring (69) that pushes the figure) has a slightly smaller spring force, and the pressure at the input port (62) (pressure at the high pressure port 3) is reduced by the relief valve 60fr. The output port (62) is disconnected from the low pressure port (63) when the pressure is lower than a predetermined high pressure, which is a little lower than the pressure discharged to the low pressure port 63.
When the pressure of the input port (62) becomes higher than a predetermined high pressure, the valve body (68) is driven to the right. That is, the pressure of the input port (62) is released to the low pressure port (63), and the pressure of the high pressure port 3 is suppressed to a predetermined high pressure or less.

With the configuration described above, in the suspension device shown in FIG. 1, the main check valve 50 supplies the oil from the high pressure port 3 to the high pressure supply pipe 8, but prevents the reverse flow from the high pressure supply pipe 8 to the high pressure port 3. .

The relief valve 60m suppresses the pressure of the high-pressure port 3, that is, the pressure of the high-pressure supply pipe 8 to a predetermined high pressure or less, and when the pressure of the high-pressure port 3 rises impulsively, the relief valve 60m returns it.
The shock pressure transmission to the high-pressure supply pipe 8 is buffered.

The bypass valve 120 controls the pressure of the rear wheel high pressure supply pipe 9 substantially linearly within a predetermined range, and maintains the pressure of the rear wheel high pressure supply pipe 9 at a predetermined constant pressure in a steady state. This constant pressure control is performed by controlling the energizing current value of the bypass valve 120 with reference to the pressure detected by the pressure sensor 13rm. Also,
When there is a shock pressure increase in the rear wheel suspension, it is released to the return pipe 11 to buffer the propagation to the high pressure supply pipe 8. Further, when the ignition switch is opened (engine stopped: pump 1 stopped), the energization is cut off and the rear wheel high pressure supply pipe 9 is made to flow to the return pipe 11, and the rear wheel high pressure supply pipe 9 (high pressure supply pipe 8 ) Release the pressure.

Pressure control valves _{80fr, 80f L, 80rr, 80r} L is the suspension pressure control, to provide the required support pressure to the suspension, the energization current value of the electrical coil (99) is controlled,
The required supporting pressure is output to the output port (84). When the shock pressure from the suspension propagates to the output port (84), it is buffered and the spool for pressure control (9
Suppress the irregularity of 1) (disturbance of output pressure). That is, the required pressure is stably applied to the suspension.

The cut valves 70fr, 70f _L , 70rr, 70r _L are provided for the suspension pressure supply line (the pressure control valve output port 84 and the suspension when the line pressure (front wheel high pressure supply pipe 6, rear wheel high pressure supply pipe 9) is lower than a predetermined low pressure. Between) to prevent the pressure from escaping from the suspension and fully open the pressure supply line when the line pressure is equal to or higher than a predetermined low pressure. This allows
An abnormal drop in suspension pressure when the line pressure is low is automatically prevented.

The relief valves 60fr, 60f _L , 60rr, 60r _L limit the pressure (mainly suspension pressure) in the suspension pressure line (between the output port 84 of the pressure control valve and the suspension) to below the high pressure upper limit value to prevent wheel collision. When there is a shocking pressure increase in the pressure supply line (suspension) due to lifting or throwing when mounting a heavy object, this is released to the return pipe 11 to mitigate the shock of the suspension and a hydraulic line connected to the suspension. And increase the durability of the mechanical elements connected to it.

FIG. 8a shows the configuration of an electric component part for controlling the hydraulic circuit of FIG. Referring to Figure 8a, this circuit is a control unit.
It is composed of an ECU and various switches, various sensors, various solenoids, etc. connected to its many input terminals and output terminals.

First, the sensors will be described. The vehicle height sensors 15f _L , 15fr, 15r _L and 15rr arranged near the shock absorbers at the FL, FR, RL, and RR positions are the distances between the wheels at each position and the vehicle body, that is, at each position. Outputs a signal according to the vehicle height. Although each vehicle height sensor detects vehicle height information in the form of a digital signal, this information is converted into an analog voltage signal and output.

13f _L , 13fr, 13r _L and 13rr are FL, FR, RL and
It is a pressure sensor located inside each shock absorber of RR, and outputs a voltage (analog signal) corresponding to each hydraulic pressure. As shown in FIG. 1, 13rm and 13rt are pressure sensors arranged in the high pressure supply pipe 8 and the reservoir return pipe 11, respectively, and output a voltage (analog signal) corresponding to the pressure at each position. Further, 16p and 16r are G sensors that output a voltage (analog signal) according to acceleration (G), 16p detects the longitudinal direction of the vehicle body, and 16r detects G in the lateral direction of the vehicle body, respectively.

SN1 is a steering sensor that outputs a pulse signal according to the amount of rotation of the steering wheel, and outputs two-phase signals that are out of phase with each other. RG is one output terminal of the regulator that stabilizes the output voltage of the generator, and outputs a binary signal indicating whether or not the engine is rotating.
SN2 is a throttle sensor that outputs a 3-bit binary signal corresponding to the opening of the throttle valve. SW2 is a reed switch that detects the rotation of the permanent magnet connected to the speedometer cable, and outputs a pulse whose period changes according to the vehicle speed.

Further, RY, SW1, SW3, SW4, SW5 and SW6 are a main relay, an ignition switch, a stop lamp switch, a door switch, a reservoir level warning switch and a vehicle height adjusting switch, respectively. SOL1, SOL2, SO
L3 and SOL4 are linear control valves (80f _L , 80fr, 80r _L , 80r) provided in the hydraulic control units of FL, FR, RL and RR respectively.
r) is a solenoid, and SOL5 is a solenoid of the bypass valve 120.

FIG. 8b shows a specific configuration of the control unit ECU shown in FIG. 8a. Referring to FIG. 8b, the control unit ECU includes two CPUs (microcomputers) 17,18, an I / O expansion unit 130, a reset control unit 140, an A / D conversion unit 150, an active filter unit 160, and a duty cycle. A control unit 170, a current detection unit 180, drivers 190 and 200, a power supply 210, a backup power supply 220, a driver 230, and an input buffer 240 are provided.

The signals applied to the input terminals IG, SPD, SS1 and SS2 of this control unit ECU are C through the input buffer 240, respectively.
Applied to the input ports PA0, ASR0, ASR1 and ASR2 of PU17. ASR0 to ASR2 are interrupt request ports. In addition, the information of the signals applied to the input terminals ICL, L1, L2, L3, STP, DOOR, LOIL and HIGH is controlled by the CP via the I / O expansion unit 130.
Applied to input ports PA4 to PA7 of U17.

Vehicle height sensor 15f _L , 15fr, 15r _L , 15rr, pressure sensor 13f _L , 13
The analog signals output by fr, 13r _L , 13rr, 13rm, 13rt and G sensor 16p, 16r are active filter units.
It is applied to each analog signal input terminal of the A / D conversion unit 150 via 160. Further, an analog signal corresponding to the current flowing through each of the solenoids SOL1 to SOL5 is generated by the current detection unit 180 and applied to each analog signal input terminal of the A / D conversion unit 150. By controlling the A / D conversion unit 150, the CPU 18 can convert the level of the signal applied to each analog signal input terminal into a digital signal and read it. CPU18 and A / D conversion unit 15
Information between 0 and 0 is transmitted through the serial output port So and the serial input port Si.

The value of the current flowing through the solenoids SOL1 to SOL5 of each solenoid valve is
Adjusted by pulse duty control (PWM). A pulse for controlling on / off of energization of each solenoid is generated by the duty control unit 170. By writing a predetermined instruction code and data for determining the duty value to the duty control unit 170 by the CPU 18,
The duty control unit 170 outputs a pulse having a duty corresponding to the data to each output terminal. Driver 20
0 controls ON / OFF of energization of each solenoid according to H / L of each pulse signal output from the duty control unit.

By the way, in this embodiment, two C's are provided in the control unit ECU.
It is equipped with PUs 17 and 18, and these two CPUs control the operation of the entire system while exchanging information with each other. Each of the CPUs 17 and 18 is provided with an 8-bit bidirectional input / output port (data bus) PB (PB7 to PB0), and these 8-bit ports are connected to each other via a signal line group 306. In addition, in the signal line group 306, all the eight lines are connected to the power supply line (+5
When the ports PB of the two CPUs are in the input state at the same time, all the lines of the signal line 306 are fixed to the high level H.

The data transmitted between the CPUs 17 and 18 is the signal line group 306.
Via 8 bit parallel data. Also,
To match the timing of sending and receiving this data,
The CPUs 17 and 18 are further connected to each other by two control lines 307 and 308. The control line 307 is an output port PA3 of the main CPU17 and an interrupt request port input IR of the sub CPU18.
The other control line 308 connects between the output port PA4 of the CPU 18 on the sub side and the interrupt request input port IRP of the CPU 17 on the main side.

The CPUs 17 and 18 store programs that control the pressure of each suspension. According to this program, the CPU 18 mainly detects the vehicle height sensors 15f _L , 15fr, 15r _L , 15rr provided in the suspension system shown in FIG.
And pressure sensors 13f _L , 13fr, 13r _L , 13rr, 13rm, 13rt, and the vertical acceleration sensor 16p and lateral acceleration sensor 16r on the vehicle, and the pressure control valves 80f _L , 80fr, 80r.
_L , 80rr and the value of the current supplied to the electric coils (99, 129) of the bypass valve 120 are controlled.

The CPU 17 handles the line pressure setting / release of the suspension system (Fig. 1), the determination of the vehicle operating state, and the determination result from the time the ignition switch is closed until it is opened, and immediately after the ignition switch is opened. In addition, the required pressure (pressure to be set for each suspension) required to establish an appropriate vehicle height and body posture is calculated, and various detected values are received from the CPU 18 to determine the vehicle operating state.
The current value required to set the required pressure is given to the CPU 18.

Hereinafter, with reference to the flowchart shown in FIG.
The control operation of the CPUs 17 and 18 will be explained.First, for ease of understanding, the symbols assigned to the main registers assigned to the internal memory of the CPU17 and the contents of the main data written to each register are described. Are summarized in Table 1 below.

In the flow chart of the drawings and the description below, the register symbol itself may mean the contents of the register.

First, refer to FIG. 9a. On-board battery to itself
When the power from 19 is supplied (step 1), the CPU 17
The internal register, the counter, the timer, etc. are set to the contents of the predetermined initial standby state, and the signal level for setting the initial standby state (the electric elements of the mechanism are not electrically energized) is output to the output port (step 2: In parentheses below, words such as steps and subroutines are omitted and only the symbols attached to them are noted).

Next, the CPU 17 checks whether the ignition switch SW1 is closed (3), and when it is open, waits until it is closed. When the ignition switch SW1 is closed, the coil of the relay RY is energized to close the contact piece of the self-holding relay RY and maintain that state (4). When the relay RY turns on, the power circuit 210
Since it is connected to 9, even if the ignition switch SW1 is opened thereafter, all the electric circuit system shown in FIG. 8 is electrically energized until the CPU 17 turns off the relay RY. Stay in the state.

When the relay RY is turned on, the CPU 17 permits execution of various interrupt processes executed in response to arrival of a pulse signal to the interrupt input ports ASR0 to ASR2 (5).

Here, the outline of the interrupt processing in response to the pulse signal to the input ports ASR0 to ASR2 will be described. First, the interrupt processing (input port ASR2) in response to the pulse generated by the vehicle speed sensor SW2 that generates the vehicle speed synchronization pulse will be described.
When a pulse is generated, responding to this, interrupt processing (ASR2)
Go to, read the contents of the vehicle speed clock register at that time, restart the vehicle speed clock register, calculate the vehicle speed value from the read contents (cycle of the vehicle speed synchronization pulse), and save the previous several times. The value Vs obtained by calculating the vehicle speed calculated value and the weighted average is written in the vehicle speed register VS, and the process returns to the step immediately before proceeding to this interrupt processing (return). By executing this interrupt processing (ASR2), data indicating the vehicle speed at that time (time-series smoothed value of vehicle speed calculation value) is constantly stored in the vehicle speed register VS.
Vs is held.

The interrupt processing (input port ASR0) generated by the rotary encoder SN1 for detecting the rotation direction of the steering shaft in response to the generated pulse of the first set will be described below. When proceeding to interrupt processing (ASR0) and proceeding to interrupt processing (ASR0) in response to a rising edge, write H to the flag register for rotation direction discrimination, and proceeding to interrupt processing (ASR0) in response to a falling edge. , Clears the flag register (writes L), and returns to the step immediately before proceeding to this interrupt processing.

When the rising edge of the pulse of the first set of the rotary encoder SN1 (flag register = H) appears next to the rising edge of the pulse of the second set, the steering shaft is driven to rotate counterclockwise and the rising edge of the pulse of the first set. When the trailing edge of the second set of pulses appears after the trailing edge (flag register = L), the steering shaft is driven to rotate clockwise.

The interrupt processing (input port ASR1) of the rotary encoder SN1 in response to the generated pulse of the second set to detect the rotation speed (steering angular velocity) of the steering shaft will be explained. When it arrives, in response to this, it proceeds to the interrupt processing (ASR1), reads the contents of the steering clock register at that time, restarts the steering clock register, and reads the contents (the period of the steering angular velocity synchronization pulse), If the content of the flag register for discriminating the direction of rotation is H, a sign of + (left rotation) is attached, and if the content of the flag register is L, a sign of − (right rotation) is attached, and the speed value ( (Including directions + and-),
The value Ss obtained by taking the speed average value and the weighted average held several times before is written in the steering angular velocity register SS, and returns to the step immediately before proceeding to this interrupt processing (return).
By executing this interrupt processing (ASR1), the steering angular velocity register SS always stores data Ss indicating the steering angular velocity (time-series smoothed value of the speed calculation value) at that time (+ indicates left rotation, − indicates right rotation).
Is held.

When the above-mentioned interrupt processing is permitted, the CPU 17 checks whether the CPU 18 gives a ready signal (6).

By the way, the CPU 18 executes initialization when the power is turned on to itself, sets internal registers, counters, timers, etc. to the contents of the initial standby state, and the output port has an initial standby state (mechanical elements). No electrical energization) is output to the duty controller 170 (data designating that all electric coils are off). Then, the duty controller 170 is supplied with the maximum current value data that causes the bypass valve 120 to be fully closed, and the energization of the bypass valve 120 is instructed. With the above settings, the pressure control valves 80f _L , 80fr,
80r _L , 80rr has a current value of zero and its output port (84)
The pressure in the return pipe 11 is output to the bypass valve 12
When 0 is fully closed and the pump 1 is rotationally driven while the engine is rotating, the pressures of the high pressure supply pipe 8, the front wheel high pressure supply pipe 6 (accumulator 7) and the rear wheel high pressure supply pipe 9 (accumulator 10) are reduced. Start climbing.

Thereafter, the CPU 18 sets the vehicle height sensor 15f _L , 15 at the first set cycle.
fr, 15r _L , 15rr, pressure sensor 13f _L , 13fr, 13r _L , 13rr, 13rm, 1
3rt, the detected values of the acceleration sensors 16p and 16r, and the current detected values of the solenoids SOL1 to SOL5 are read, updated and written in the internal register, and when the CPU17 requests the transfer of the detected data, The data in the internal register is CPU1
Transfer to 7.

When the CPU 17 sends the energizing current target value data of each of the pressure control valves 80f _L , 80fr, 80r _L , 80rr and the bypass valve 120, each of these target values and the solenoids SOL1 to SO.
Each control duty value is generated based on the corresponding current detection value of L5, and these are generated.
Give to 0.

When the CPU 18 gives a busy signal in the checks in steps 6 and 7 described above, the CPU 17 waits there and executes the waiting process (8 to 11). In the standby process (8), the presence / absence of abnormality is determined by referring to the pressure detection values of all the pressure sensors, the current detection values of all the solenoids, and the vehicle height detection values of all the vehicle height sensors, and the suspension control waits (while stopped). When the pressure is set (the bypass valve 120 is de-energized, it is fully opened and the pressure control valve is de-energized), and if an abnormality is judged, an alarm corresponding to the abnormality and pressure setting (bypass valve 120 de-energized, pressure control valve de-energized) ) (10).
If no abnormality is determined, the abnormality processing is canceled (abnormality notification is cleared) (11).

Now, when the CPU 18 outputs the ready, the above-mentioned abnormal processing (which may not be executed) is canceled (12) and the standby processing (which may not be executed) is canceled (13).

Then, the CPU 17 instructs the CPU 18 to transfer the detected pressure data Dph of the pressure sensor 13rm, receives this, and receives the register DPH.
Write (14) to the detected pressure (pressure on the rear wheel side of the high pressure supply pipe 8) Dp
Check whether h is equal to or greater than a predetermined value Pph (pressure value lower than a predetermined low pressure at which the cut valves 70f _L , 70fr, 70r _L , 70rr start to open) (whether the line pressure has risen to some extent) (1
Five). If the line pressure has not risen, the process returns to step 6.

When the line pressure rises, the CPU17
13f _L , 13fr, 13r _L , 13rr Detection pressure (initial pressure) data Pf _L0 , Pf
It instructs transfer of r ₀ , Pr _L0 , Prr ₀ , receives them, and writes them in registers PFL ₀ , PFR ₀ , PRL ₀ , PRR ₀ (16).

Then, in one area (table 1) of the internal ROM, the energization current value data required to obtain the required pressure is stored in registers PFL ₀ , PFL
Contents of FR ₀ , PRL ₀ , PRR ₀ Pf _L0 , Pfr ₀ , Pr _L0 , Prr ₀ access and solenoid current required to output pressure Pf _L0 to output port 84 of pressure control valve 80f _L Ihf _L , pressure Pfr ₀ , the energizing current value required to output the pressure control valve 80fr output port Ihfr, pressure Pr _{L 0} , the energizing current value required to output the pressure control valve 80r _L output port Ihr _L , and pressure Prr Current value required to output ₀ to the output port of pressure control valve 80rr
Ihrr, is read from table 1 and output register IH
Write to f _L , IHfr, IHr _L and IHrr (17) and transfer the data of these output registers to the CPU 18. The CPU 18 uses these data as the target value of the current, and based on this and the detected current value of the solenoid, generates a duty value that makes them equal, and uses that value as the duty controller 17
Give to 0.

The duty controller 170 generates a pulse signal of a duty corresponding to each input duty value, and controls energization of each solenoid valve via the driver 200.

Depending on the current setting (target value) at this time, the pressure control valve 80
f _L , 80fr, 80r _L , 80rr are the pressures of Pf _L0 , Pfr ₀ , Pr _L0 , Prr _{0 which} are substantially output to the output port (84) when the line pressure is higher than the specified low pressure. When the cut valves 70f _L , 70fr, 70r _L , 70rr open in response to the rise above a predetermined low pressure, the pressure (initial pressure) of each suspension at that time Pf _L0 , Pfr ₀ , Pr _L0 , Prr ₀ Substantially equal pressure is applied through the cut valves 70f _L , 70fr, 70r _L , 70rr to the pressure control valves 80f _L
Suspension 100f _L , 100fr, 100r _L , 100 from r, 80r _L , 80rr
Supplied to rr.

Therefore, the ignition switch SW1 changes from open (engine stopped: pump 1 stopped) to closed (pump 1 driven),
When the cut valves 70f _L , 70fr, 70r _L , 70rr are opened for the first time (line pressure is lower than a predetermined low pressure) and the hydraulic line of the suspension communicates with the output port of the pressure control valve, the output pressure of the pressure control valve and the suspension pressure are Are substantially equal to each other, and sudden pressure fluctuations in the suspension do not occur. That is, no shocking change in the vehicle body posture occurs.

The above is the pressure control valve 80 when the ignition switch SW1 is switched from open to closed (immediately after starting the engine).
Initial output pressure setting of f _L , 80fr, 80r _L , 80rr.

 Next, the CPU 17 starts a timer ST for the ST time period.

ST is the contents of register ST, and register ST contains CPU1
Data ST indicating a second setting cycle which is longer than the first setting cycle in which the detection value 8 is read is written.

When the timer ST is started, the CPU 17 reads the status (20)
Perform In this, the ignition switch SW2
Open / close signal, open / close signal of brake pedal depression detection switch SW3, throttle opening data of absolute encoder SN1, and signal of reservoir level detection switch SW5 are read and written to internal register, and CPU18 is instructed to transfer detection data. Then, the vehicle height sensor 15f _L , 15fr, 15
Vehicle height detection data of r _L , 15 rr Df _L , Dfr, Dr _L , Drr, pressure sensor
13f _L , 13fr, 13r _L , 13rr, 13rm, 13rt pressure detection data Pf _L , P
_{fr, Pr L, Prr, Prm} , Prt, and a pressure control valve and the bypass valve 80f _L, 80FR, 80 r _L, receives the transfer of the electric current value detection data 80Rr, 120, written into the internal register.

Then, referring to these read values, it is determined whether there is an abnormality or not, and when it is abnormal, the process proceeds to step 8.

When normal, the CPU 17 next executes line pressure control (LPC). In this case, the reference pressure (relief valve 60
Absolute value and polarity (high / low) of the deviation of the detection line pressure Prm with respect to a fixed value (slightly lower than the relief pressure of m (predetermined high pressure))
To calculate the current value of the bypass valve 120 at this time by adding a correction value to the current value of the current flowing in the bypass valve 120, which corresponds to the deviation and makes the deviation zero. Write to output register. The contents of this output register are transferred to the CPU 18 in step 36 described later.

By this "line pressure control" (LPC), the bypass valve 120 is set so that the pressure of the rear wheel high pressure supply pipe 9 becomes a predetermined value slightly lower than the relief pressure (predetermined high pressure) of the relief valve 60m.
The energizing current value of is controlled.

Now referring to FIG. 9b. After completing the line pressure control (LPC), the CPU 17 checks whether the switch 20 is open or closed (2
2) If it is open, stop processing (23) is performed, the relay 22 is turned off, and interrupts ASR0 to ASR2 are prohibited. In the stop processing (23), first, the bypass valve
120 is de-energized and fully opened (the line pressure is released to the return pipe 11).

The switch SW1 is opened (engine stopped: pump 1 stopped), high-pressure discharge of the pump 1 is stopped, and the bypass valve 120 is fully opened.
The pressure of the (accumulator 7) and the rear wheel high pressure supply pipe 9 (accumulator 10) becomes the pressure of the return pipe 11, and the pressure of the return pipe 11 is released to the reservoir 2, whereby the high pressure supply pipe 8 and the like become atmospheric pressure. The high pressure supply pipe 8 etc.
At the timing when f _L , 70fr, 70r _L , and 70rr reach a pressure equal to or lower than the predetermined low pressure at which complete shutoff is performed, the CPU 17 sets the pressure control valve 80f _L ,
80fr, 80r _L , 80rr are de-energized.

Now, when the switch SW1 is closed, the parameter indicating the vehicle traveling state is calculated (25). That is, the content Ss of the steering angular velocity register SS is read, and [subroutine 20
Then, calculate the throttle opening Tp read this time, the throttle opening Tp read this time-the throttle opening read last time] = Ts (throttle opening / closing speed), and write it to the register TS.

Next, the CPU 17 executes "vehicle height deviation calculation" (31),
The suspension pressure correction amount (first correction amount: required to calculate the deviation of the vehicle body height from the target vehicle height and set it to zero)
For each suspension). For details of this content,
This will be described later with reference to FIG. 10a.

The CPU 17 executes a “pitching / rolling prediction calculation” (32) after the “vehicle height deviation calculation” (31), and executes a suspension pressure correction amount (the second one) corresponding to the vertical and lateral accelerations actually applied to the vehicle body. 2 Correction amount: for each suspension), and calculate the [suspension initial pressure (Pf _L0 , Pfr ₀ , Pr _L0 , Pr
r ₀ ) + first correction amount + second correction amount] (calculation intermediate value: for each suspension). For details of this content, see Section 10b.
It will be described later with reference to the drawings.

Next, the CPU 17 executes the "pressure correction" (33) to correspond to the line pressure (high pressure) detected by the pressure sensor 13rm and the return pressure (low pressure) detected by the pressure sensor 13rt, and calculates the "calculated intermediate value". Is corrected. For details of this content, see Section 10c.
It will be described later with reference to the drawings.

CPU17 then is a "pressure / current conversion" (34), and the correction "calculation intermediate value" (the respective per suspension), the pressure control valve _{(80f L, 80fr, 80r L} , 80rr) current to flow in the Convert to This content will be described later with reference to FIG. 10d.

The CPU17 then uses "warp correction" (35) to determine the lateral acceleration Rg.
And a turning warp correction value (current correction value) corresponding to the steering speed Ss is calculated, and the current value to be passed through the pressure control valve is added. For details on this content, see Section 10e
It will be described later with reference to the drawings.

Next, the CPU 17 transfers the current value that should be passed through the pressure control valve calculated in the above “output” (36) to each pressure control valve to the CPU 18, and at the same time as the above “line pressure control”. (LPC), the current value to be passed through the bypass valve 120 is transferred to the CPU 18 to the bypass valve 120.

Here, the CPU 17 has completed all the tasks included in the suspension pressure control for one cycle. Therefore, wait until the timer ST times out (37),
When the time is over, the process returns to step 19, restarts the timer ST, and executes the task of the suspension pressure control in the next cycle.

Due to the suspension pressure control operation of the CPU 17 described above, the CPU 18 requests the CPU 18 to transfer the sensor detection value in the ST cycle (second setting cycle) (subroutine 20), and in response thereto, the CPU 18 The read values of the past several times and the sensor detection value data that has been subjected to the weighted average smoothing are read in one set cycle and transferred to the CPU 17. Further, in the ST cycle, the current value data to be passed through each of the pressure control valves and the bypass valve 120 is transferred from the CPU 17 to the CPU 18, and each time the CPU 18 receives this transfer, these current value data and the solenoid The duty value is calculated from the detected current value and the value is output to the duty controller 170. Therefore, the current value of each of the pressure control valves and the bypass valve 120 is S
It is updated to approach the target current value in the T cycle.

The contents of the “vehicle height deviation calculation” (31) will be described with reference to FIG. 10a. First, in the overview, the vehicle height sensors 15f _L , 15fr, 15
Vehicle height detection value of r _L , 15 rr Df _L , Dfr, Dr _L , Drr (Register DFL, DF
R, DRL, DRR), heave (height) DHT, pitch (difference between front wheel height and rear wheel height) DPT, roll (right wheel height and left wheel height) Difference) DRT and warp (difference between the sum of the front right wheel vehicle height and the rear left wheel vehicle height and the front left wheel vehicle height and the rear right wheel vehicle height) DWT are calculated. That is,
Each wheel height (contents of registers DFL, DFR, DRL, DRR) is converted into posture parameters (heave DHT, pitch DPT, roll DRT and warp DWT) of the entire vehicle body.

DHT = DFL + DFR + DRL + DRR, DPT =-(DFL + DFR) + (DRL + DRR), DRT = (DFL-DFR) + (DRL-DRR), DWT = (DFL-DFR)-(DRL-DRR). This DPT is calculated in "Pitching error CP calculation" (51), and DRT is calculated in "Rolling error C".
Calculation of R ”(52) and calculation of DWT is“ Warp error ”
Calculation of CW ”(53).

Then, in “Calculation of heave error CH” (50), the vehicle speed Vs
Derivation of the target heave Ht from the calculated heave DHT,
Calculate the heave error amount for the target heave Ht, and
For (proportional, integral, derivative) control, the calculated heave error amount is subjected to PID processing to calculate a heave correction amount CH corresponding to the heave error.

Similarly, in "Calculation of pitching error CP" (51), the target pitch Pt is derived from the vertical acceleration Pg, and the calculated pitch is calculated.
Calculate the pitch error amount for the target pitch Pt of DPT, and
For ID (proportional, integral, derivative) control, the calculated pitch error amount is subjected to PID processing to calculate a pitch correction amount CP corresponding to the pitch error.

Similarly, in "Calculation of rolling error CR" (52), the target roll Rt is derived from the lateral acceleration Rg and the calculated roll is calculated.
Calculate the roll error amount for the target roll Rt of DRT and PID
For the (proportional, integral, derivative) control, the calculated roll error amount is subjected to PID processing to calculate a roll correction amount CR corresponding to the roll error.

Similarly, in the “calculation of warp error CW” (53), the target warp Wt is set to zero, and the target warp W
Calculate the warp error amount for t and calculate the PID (proportional, integral,
For differential control, the calculated warp error amount is subjected to PID processing to calculate a warp correction amount CW corresponding to the warp error. When the absolute value of the calculated warp error amount (DWT because the target warp is zero) is less than or equal to a predetermined value (within the allowable range), the warp error amount for PID processing is set to zero, and when it exceeds the predetermined value. Let the amount of warp error for PID processing be −DWT.

To explain in detail the content of “calculation of heave error CH” (50), the CPU 17 firstly sets the target heave Ht corresponding to the vehicle speed Vs.
Is read from one area (table 2H) of the internal ROM and written in the heave target value register HT (39).

As shown as “Table 2H” in FIG. 10a, the vehicle speed V
The target heave Ht associated with s is that the vehicle speed Vs is VsaKm.
At low speeds below / h, the high value is Ht ₁ , and at high speeds above VsbKm / h, the low value is Ht ₂ , but in the range where Vs is above Vsa and below Vsb, the target value is Vs. Changes linearly (may be a curve). In this way, the target value is changed linearly if, for example, 100 Km / h or less, the target value is changed to H
When the target value is switched to Ht ₂ stepwise at t ₁ and 100 Km / h or more, when Vs is near 100 Km / h, the target heave changes greatly in steps due to a slight change in Vs velocity. This is to prevent the vehicle height from being raised and lowered frequently at high speeds and the vehicle height stability being deteriorated. Above table
According to the setting of 2H, the target value changes only slightly when the vehicle speed Vs changes slightly, so the vehicle height target value changes only slightly and the vehicle height stability increases.

In step 40, the heave amount obtained by the calculation of DFL + DFR + DRL + DRR is stored in the register DHT.

In the next step 40B, a filter processing subroutine is executed. Details of this processing will be described with reference to FIG. 10f. The contents of each symbol in Fig. 10f are as follows.

Fhf: Vehicle height sensor error flag KFH: Register holding filter variables KFHH: Filter constant when vehicle height sensor is normal KFHL: Filter constant when vehicle height sensor is abnormal (KFHH> KFHL) In step 92, the height sensor (vehicle height (Sensor), the voltage of the signal obtained from is monitored, and it is discriminated whether it is within a predetermined range (between VHmax and VHmin in the graph in FIG. 10f). Identify whether the sensor is abnormal. Normally, that is, when there is no abnormality in the height sensor, KFH
The constant KFHH is stored in, but when an abnormality of the vehicle height sensor is detected, the constant KFHL is stored in KFH.

The amount of heave retained in the DHT is digitally filtered in a processing step not shown, but the content of KFH is used as a parameter to determine the cutoff frequency of the filter characteristic during the filtering. It
In this embodiment, KFHH> KFHL is set, and when an abnormality occurs in the vehicle height sensor, KFHL is selected, so the cutoff frequency of the filter can be switched to a value sufficiently lower than that in the normal state. .

When the cutoff frequency of the filter is high, even if the detected heave amount (DHT) changes relatively quickly, the heave amount equivalent to the input can be obtained at the output of the filtering process.
When the cutoff frequency is low, the output of the filter is smoothed and the change becomes gentle. In other words, when a sudden change appears in the DHT value, the change is greatly attenuated and appears in the filter output.

When the cutoff frequency of the filter is set low, the response of control to the heave error deteriorates. Therefore, in order to perform preferable suspension control, it is necessary to set the cutoff frequency of the filter higher. In this embodiment, when the vehicle height sensor is regarded as normal, a relatively high cutoff frequency (corresponding to KFHH) is set, and when an abnormality of the vehicle height sensor is detected, a relatively low cutoff frequency (corresponding to KFHL). ) Is set, the responsiveness of suspension control is not deteriorated by the filtering process unless an abnormality occurs in the vehicle height sensor.

Also, for example, if a failure such as a circuit open or short circuit occurs in the vehicle height sensor, a rapid change occurs in the vehicle height sensor output VH. Therefore, if the detected value is directly used for detecting the heave amount, The differential term, that is, the value corresponding to the heave change amount (EHT2-EHT1) temporarily becomes extremely large, a sudden pressure control is performed, the vehicle height suddenly changes, and a shock is transmitted to the occupant. However, in this embodiment, in such a case, an abnormality of the vehicle height sensor is detected, so that the cutoff frequency of the filtering process is set to a low value (KFH
L). Therefore, the detected heave amount (D
Even if a sudden change in (HT) occurs, the change in the filtered heave amount (DHT2), that is, the heave change amount (EHT2-EHT1) does not become abnormally large, and It is possible to avoid shock caused by changes.

Although not shown, the past N points and the latest DHT value detected at regular intervals are actually stored in the memory, and the DHT values are averaged in the digital filter processing. ing. For example, by averaging the latest 100 DHTs obtained every 1 msec, the heave amount averaged every 100 msec can be obtained. Of the frequency components included in DHT, the component with a longer period (lower frequency) with respect to the averaging period passes through the filter without being attenuated, so it appears in the output (DHT2), but with respect to the averaging period, Therefore, the components with short cycle (high frequency) are attenuated and do not appear in the value of DHT2. In this example, this averaging period is the parameter stored in register KFH, namely KFHH or KFHL.
Determined by

For example, the detection cycle of the heave amount by the vehicle height sensor is ΔT.
Then, when the averaging cycle of the filter processing is N · ΔT,
Even if the amount of change in the instantaneous value of DHT is Vmax, the change in DHT2 per control cycle is Vmax / N, and if N is sufficiently large, an increase in the amount of change in the filter output can be suppressed.

Next, write the contents of the register EHT2 in which the previously calculated heave error amount is written to the register EHT1 (41), calculate the current heave error amount HT-DHT2, and register this.
Write to EHT2 (42). As described above, the heave error amount of the previous time (before ST) is stored in the register EHT1, and the heave error amount of this time is stored in the register EHT2. Next, the CPU 17 writes the content of the register ITH2 in which the error integrated value up to the previous time is written into the register ITH1 (43), and calculates the current PID correction amount ITh by the following formula.

ITh = Kh ₁ / EHT ₂ + Kh ₂ / (EHT ₂ + Kh ₃ / ITH 1) + Kh ₄ / Kh _{5
· (EHT2-EHT1) Kh 1} · EHT2 is P (proportional) term of the PID operation, Kh ₁ coefficients of the proportional term, EHT2 is the content of register EHT2 (Hibuera amount of time).

Kh ₂ · (EHT2 + Kh ₃ · ITH1) is the I (integral) term,
Kh ₂ is the coefficient of the integral term, ITH 1 is the correction amount integral value up to the previous time (the integral value of the correction amount output from the initial pressure setting 16-18),
Kh ₃ is a weighting coefficient between the current error amount EHT2 and the correction amount integral value ITH1.

_{Kh 4 · Kh 5 · (EHT2} -EHT1) is a D (differential) term,
The coefficient of the differential term is Kh ₄ · Kh ₅ , but Kh ₄ uses a value associated with the vehicle speed Vs, and Kh ₅ uses a value associated with the steering angular velocity Ss. That is, the vehicle speed correction coefficient Kh ₄ associated with the vehicle speed Vs at that time is read from one area of the internal ROM (table 3H), and the steering angular velocity Vs at that time is read from one area of the internal ROM (table 4H). The associated steering angular velocity correction coefficient Kh ₅ is read out and the product Kh ₄
・ Kh ₅ is the coefficient of the differential term.

As shown as “Table 3H” in FIG. 10a, the vehicle speed correction coefficient Kh ₄ is generally a larger value as the vehicle speed Vs is higher, and the weight of the differential term is increased. This is a correction term in which the derivative term tries to quickly accommodate the change in the heave to the target value, and the higher the vehicle speed, the faster the vehicle height changes with respect to the disturbance, so it is increased according to the vehicle speed. . On the other hand, vehicle speed Vs
When the value exceeds a certain level (VsdKm / h or higher in Table 3H), sudden changes in the vehicle body posture occur when the brake pedal is depressed / released, the accelerator pedal accelerates / decelerates, and the steering wheel turns / turns back. However, it becomes extremely large, and the excessive differential term that quickly compensates for such a sudden change in posture deteriorates the vehicle height control stability. Therefore, more precisely, the vehicle speed correction coefficient Kh ₄ of the table 3H changes greatly with respect to changes in the vehicle speed Vs when the vehicle speed Vs is low, and changes with decreasing vehicle speed Vs. That is, when the vehicle speed Vs is low, the weight of the differential term changes greatly with respect to the vehicle speed fluctuation, but when the vehicle speed Vs is high, the weight change of the differential term with respect to the vehicle speed fluctuation is small.

As shown as “Table 4H” in FIG. 10a, the steering angular velocity correction coefficient Kh ₅ is generally a larger value as the steering angular velocity Ss is higher, and the weight of the differential term is increased. This is a correction term for the derivative term to try to fit this into the target value faster with respect to the change in the heave, and the higher the steering angular speed Ss, the faster the vehicle height change speed with respect to disturbance, so the steering angle speed depends on the steering angle speed. I am raising. On the other hand, when the steering angular velocity Ss is below a certain level (Ssa ° / msec or less in Table 4H), the change in the traveling direction is extremely gentle and the weighting of the differential term is small, exceeding Ssa and Ssb ° / msec.
In the following, the vehicle height change appears at a speed that is substantially proportional to the steering angular speed Ss. At steering angular velocities of Ssb and above, changes in the vehicle body posture become abrupt and extremely large, and an excessive differential term that quickly compensates for such a sudden posture change will be dangerous because the stability of the vehicle height control will be lost. Therefore, the steering angular velocity
The coefficient Kh ₅ of the differential term corresponding to Ss is a constant value when Ss is Ssa or less, a high value that is substantially proportional to Ss when Ss is above Ssb and below Ssb, and a constant value when Ssb is above Ssb. There is.

With the introduction of more than differential term Kh ₄ · Kh ₅ · described (EHT2-EHT1), or even, the coefficient Kh ₄ increased in response to the vehicle speed Vs, correspondingly greater coefficient Kh ₅ to the steering angular velocity Ss By doing so, weighted differential control corresponding to the vehicle speed Vs and the steering angular speed Ss is realized, and highly stable vehicle height control is realized with respect to variations in the vehicle speed Vs and the steering angular speed Vs.

At step 44, the values of the proportional term, integral term, and derivative term of the PID calculation are added, and the result is obtained as a heave error correction amount ITh.

Next, the CPU 17 writes the calculated heave error correction amount ITh in the register ITH2 (45), and adds a heave error correction amount weighting coefficient Kh ₆ (weighting to a pitch error correction amount, a roll error correction amount, and a warp error correction amount described later: Multiply by the contribution ratio of the total correction amount) and write it in the heave error register CH.

When the calculation (50) of the heave error CH is performed as described above, the CPU 17 executes the “calculation of the pitching error CP” (51), calculates the pitch error correction amount CP in the same manner as the heave error CH, and Write to register CP. In this case, the pitch target value PT corresponding to the heave target value HT is the data Pt corresponding to the vertical acceleration Pg at that time (target corresponding to the longitudinal acceleration Pg) from one area of the internal ROM of the CPU 17 (Table 2P). Value) is read and obtained.

The vehicle height sensor 15f _L , 15f
In order to prevent a shock at the time of failure of r, 15r _L, and 15rr, the detected pitching amount DPT is subjected to the same digital filter processing as that for the heave amount.

Fig. 11a shows the contents of table 2P. The pitch target value Pt corresponding to the vertical (forward / backward) acceleration Pg is the vertical acceleration Pg.
It is in the direction to cancel (decrease) the pitch appearing by. The region a is intended to save energy by increasing the target pitch as the vertical acceleration Pg increases (decreases). The region b is considered to be an abnormal sensor for abnormal Pg, so the pitch target value should be reduced. , This is to prevent giving a pit target value even though Pg is not actually generated. The other calculation processing operations are the same as the contents of the above-mentioned “calculation of heave error CH” (50), the HT and Ht of step 39 are replaced with PT and Pt, and the DHT calculation formula of step 40 is changed to the above-mentioned DPT. Replace with calculation formula, EHT1, EH in step 41
Replace T2 with EPT1, EPT2 and EP for EHT2, HT, DHT in step 42
Replace with T2, PT, DPT and replace ITH1, ITH2 in step 43 with ITP1, ITP
2 is replaced, the ITh calculation formula of the subroutine 44 is replaced with a pitch error correction amount ITp calculation formula which has a completely corresponding relationship with it, and the table 3H is replaced with a coefficient table (3P) for pitch correction amount ITp calculation, The table 4H is also replaced with the coefficient table (4P) for calculating the pitch correction amount ITp, and the ITH at step 45 is replaced.
2, replacing the ITh in ITP2, ITp, and CH of the step 46, Kh _6, IT
By replacing h with CP, Kp ₆ , ITp, the pitch error C
A flow chart showing the contents of "Calculation of P" (51) appears. The CPU 17 executes the processing represented by this flowchart.

Next, the CPU 17 "calculates rolling error CR" (52)
To execute the roll error correction amount CR and the heave error CH.
Calculate in the same way as and write to the roll error register CR. In this case, the roll target value RT corresponding to the heave target value HT is the data Rt (lateral acceleration) corresponding to the lateral acceleration Rg at that time from one area of the internal ROM of the CPU 17 (table 2R).
Roll target value corresponding to Rg) is read and obtained.

Also in calculating roll error, vehicle height sensor 15f _L , 15f
In order to prevent a shock at the time of failure of r, 15r _L and 15rr, the detected rolling amount DRT is subjected to the same digital filter processing as that for the heave amount.

Figure 11b shows the contents of Table 2R. The roll target value Rt corresponding to the lateral acceleration Rg is in a direction (decreasing) for canceling the roll that appears due to the lateral acceleration Rg. The region a is intended to save energy by increasing the target roll as the lateral acceleration Rg increases (decreases). The region b is considered to be an abnormal sensor due to an abnormal Rg. This is to prevent the roll target value from being given even if Rg has not actually occurred. For other calculation processing operations, refer to "Calculation of heave error CH" (5
0) is the same as that in step 39, and HT, Ht in step 39 is changed to RT, R
Replace with t, replace the DHT formula in step 40 with the above DRT formula, replace EHT1, EHT2 in step 41 with ERT1, ERT2, replace EHT2, HT, DHT in step 42 with ERT2, RT, DPT. Replace,
ITH1 and ITH2 in step 43 are replaced with ITR1 and ITR2, the ITh calculation formula of the subroutine 44 is replaced with a roll error correction amount ITr calculation formula that has a completely corresponding relationship with it, and the table 3H is used for calculating the roll correction amount ITr. Replace with the coefficient table (3R),
Table 4H is also a coefficient table (4
Substituted with R), the ITH2, ITh in step 45 is replaced with ITR2, ITr, and CH of the step 46, by replacing the Kh _6, ITh CR, and Kr _6, ITr, "calculation of roll error CR" A flowchart showing the contents of (51) appears. The CPU 17 executes the processing represented by this flowchart.

Next, the CPU 17 executes "calculation of warp error CW" (53), calculates the warp error correction amount CW in the same manner as the heave error CH, and writes it in the warp error register CW. In addition,
In this, the warp target value corresponding to the heave target value HT
PW is set to zero.

Even when calculating the warp error, the vehicle height sensor 15f _L , 15f
In order to prevent a shock at the time of failure of r, 15r _L and 15rr, the detected warp amount DWT is subjected to the same digital filter processing as that for the heave amount.

The other calculation processing operations are the same as those in the above-mentioned “calculation of heave error CH” (50).
Replace T, Ht with WT, 0 and replace the DHT calculation formula in step 40 with D
Replace with EWT1, EHT2 in step 41 by replacing with WT calculation formula
Replace the contents of step 42 with the absolute value of DWT, which is the predetermined value W.
When it is m or less (within the allowable range), WT is set to 0, and when Wm is exceeded, WT is set to −DWT and WT is written to the register EWT2, and ITH1 and ITH2 in step 43 are changed to ITW1 and ITW2.
, The ITh calculation formula of the subroutine 44 is replaced with a warp error correction amount ITw calculation formula that has a completely corresponding relationship, and table 3h is replaced with a coefficient table (3W) for calculating the warp correction amount ITr. 4H is also replaced with the coefficient table (4W) for calculating the warp correction amount ITw, and ITH in step 45
2, ITh is replaced with ITW2, ITw, and CH, Kh ₆ , IT in step 46
Replacing h with CW, Kw ₆ ,, ITw gives the "warp error C
A flowchart showing the contents of the calculation (53) of W appears. The CPU 17 executes the processing shown in this flowchart.

As described above, when the heave error correction amount CH, the pitch error correction amount CP, the roll error correction amount CR, and the warp error correction amount WP are calculated, the CPU 17 determines these correction amounts as the suspension pressure correction amount EHf _{L of} each wheel portion. (Suspension 100f _L addressed), EHfr (100fr addressed), EHr _L (100r _L addressed), EHrr (100rr addressed). That is, the suspension pressure correction amount is calculated as follows.

EHf _L = Kf _L · Kh ₇ · (1/4) · (CH-CP + CR + CW), EHfr = Kfr · Kh ₇ · (1/4) · (CH-CP – CR-CW), EHr _L = Kr _L · Kh ₇ · (1/4) · (CH + CP + CR-CW), EHrr = Krr · Kh ₇ · (1/4) · (CH + CP-CR + CW) Coefficients Kf _L , Kfr, Kr _L , Krr are line pressure reference point 13rm And the return pressure reference point 13rt, suspension 100 f _L ,
This is a correction coefficient for compensating the suspension supply pressure deviation due to the difference in pipe length of 100fr, 100r _L , 100rr. Kh
Reference numeral ₇ is a coefficient for increasing / decreasing the vehicle height deviation correction amount corresponding to the steering angular velocity Ss, and is read from one area (table 5) of the internal ROM of the CPU 17 corresponding to the steering angular velocity Ss. . If the steering angular velocity Ss is large, a large change in attitude is expected, and an increase in the amount of attitude error is expected. Therefore, the coefficient Kh
₇ is generally set to be large in proportion to the steering angular velocity Ss. However, the steering angular velocity Ss is below a certain level (Table 5
At Ssc ° / msec or less), the change in the traveling direction is extremely gentle, the posture change is small, and it exceeds Ssc and Ssd ° / m
At sec or less, the posture change appears at a speed substantially proportional to the steering angular speed Ss. At steering angular velocities that exceed Ssd, the change in the vehicle body posture becomes abrupt and extremely large, and an excessive correction amount that quickly compensates for such a sudden posture change is
The vehicle height control stability deteriorates. Therefore, the correction coefficient Kh ₇ corresponding to the steering angular velocity Ss is a constant value when Ss is Ssc or less,
Above Ssc and below Ssd, a high value that is substantially proportional to Ss,
When Ssd is exceeded, the value at Ssd is kept constant.

Next, with reference to FIG. 10b, the contents of the “pitching / rolling prediction calculation” (32) will be described. The above-mentioned "vehicle height deviation calculation" (31) is generally used to detect the current vehicle body posture from the current vehicle height and steering angular velocity so as to maintain the vehicle body posture at a predetermined and appropriate one, and to determine the current vehicle body posture. While the suspension pressure is adjusted (feedback control) so as to obtain the predetermined appropriate value, the "pitching / rolling prediction calculation" (32) is based on the vertical and lateral acceleration applied to the vehicle body. It is intended to suppress changes in the body posture.

The CPU 17 first calculates a correction amount CGT for suppressing a change in pitch due to a change in vertical acceleration Pg (55 to 58). In this case, the contents of the register GPT2 that previously wrote the correction amount corresponding to Pg are written to the register GPT1 (55),
The correction amount Gpt corresponding to Vs and Pg is read from one area of ROM (table 6) and is written in the register GPT2 (5
7). The data Gpt in Table 6 is grouped with Vs as an index, and the CPU 17 specifies the group with Vs,
Read the Pg-compatible data Gpt in the specified group. In each group, the smaller the Vs is assigned, the dead zone a width (Gpt = in Table 6 shown in FIG. 10b).
The width of 0) is set to a large value. b is a region where the gain is increased and the control performance is improved as the vertical acceleration Pg is increased, and c is a region where the control performance is reduced because more than the sensor is considered.

Next, the CPU 17 calculates the correction amount CGP for suppressing the change in the vertical acceleration Pg by the following equation and writes it in the register CGP (58).

CGP = Kgp ₃ · _{[Kgp 1 · GPT2 + Kgp 2 ·} (GPT2-GPT1) ] GPT2 represents the content of register GPT2, time, table 6
This is the correction amount Gpt read out. GPT1 is register GPT1
And the correction amount read out from the table 6 last time. Kgp ₁ of P (proportional) term Kgp ₁ · GPT2 is the coefficient of the proportional term.

D Kgp ₂ of (differential) term Kgp ₂ · (GRT2-GRT1) is a coefficient of differential term, this factor Kgp _2, the internal in response to the vehicle speed Vs RO
It is read from one area of M (Table 7).
As shown as “Table 7” in FIG. 10b, the coefficient Kgp
₂ is generally the larger the higher the vehicle speed Vs, the larger the weight of the differential term. This is a correction term in which the differential term tries to suppress the change in the vertical acceleration Pg faster, and the higher the vehicle speed, the more the vehicle is depressed / released and the accelerator pedal is used to increase / decrease.
This is because changes in the vertical acceleration Pg due to turning / turning back due to deceleration, rotation of the steering, and the like are fast, so that the posture change is quickly suppressed in response to the fast changes. On the other hand, when the vehicle speed Vs exceeds a certain level, when the brake pedal is depressed / released, the accelerator pedal accelerates / decelerates, or the steering wheel turns / turns back, the longitudinal acceleration Pg changes rapidly and is extremely large. Therefore, an excessive differential term that quickly suppresses a sudden posture change at this time destroys the stability of suppressing the longitudinal acceleration. Therefore, more precisely, the coefficient Kgp _{2 of the} table 7 changes greatly with respect to the change of the vehicle speed Vs when the vehicle speed Vs is low, and is constant when the vehicle speed Vs is a predetermined value or more. That is, vehicle speed Vs
When is low, the weight of the differential term changes greatly with respect to the change in vehicle speed, but when the vehicle speed Vs is high, there is no change in weight of the differential term with respect to the change in vehicle speed.

The calculated correction amount CGP for suppressing the change in the vertical acceleration Pg is the pitch correction amount for the suspension, and Kgp ₃ is
This is a weighting coefficient for a roll correction amount CGR and a GES described later.

Next, the CPU 17 calculates a correction amount CGR for suppressing the roll change due to the change of the lateral acceleration Pg (that is, suppressing the change of the lateral acceleration Pg) (59 to 62). In this case, the previous contents of the register GRT2 in which the correction amount corresponding to Rg is written is written to the register GRT1 (59), and the correction amount Grt corresponding to Vs and Rg is read from one area (table 8) of the internal ROM. Write this to register GRT2 (61). The data Grt in Table 8 is grouped with Vs as a ring, and C
The PU 17 designates a group with Vs and reads the Rg-compatible data Grt in the designated group. In each group, the dead band a width (the 10th
In Table 8 shown in FIG. b, the horizontal width of Grt = 0) is set to be large. b is a region where the gain is increased and the control performance is improved as the lateral acceleration Rg is increased, and c is a region where the sexual control performance is deteriorated because more than the sensor is considered.

Next, the CPU 17 calculates a correction amount CGR for suppressing the change of the lateral acceleration Rg by the following equation and writes it in the register CGR (62).

CGR = Kgr ₃ · _{[Kgr 1 · GRT2 + Kgr 2 ·} (GRT2-GRT1) ] GRT2 represents the content of register GRT2, a correction amount Grt read from this table 8. GRT1 is the content of the register GRT1 and is the correction amount read from the table 8 last time. P (proportional) term Kgr ₁ · Kgr ₁ of GRT ₂ is a coefficient of the proportional term.

D Kgr ₂ of (differential) term Kgr ₂ · (GRT2-GRT1) is a coefficient of differential term, this factor Kgr _2, the internal in response to the vehicle speed Vs RO
It is read from one area of M (Table 9).
As shown as “Table 9” in FIG. 10b, the coefficient Kgr
₂ is generally the larger the higher the vehicle speed Vs, the larger the weight of the differential term. This is a correction term in which the differential term tries to suppress the change in lateral acceleration Rg faster, and the higher the vehicle speed, the faster the change in vertical acceleration Rg due to turning / turning back due to rotation of the steering wheel. This is because it is intended to quickly suppress this by correspondingly. On the other hand, vehicle speed Vs
When the value becomes a certain value or more, turning / returning by turning the steering wheel suddenly causes a rapid and extremely large change in lateral acceleration Rg, and an excessive differential term that suppresses such a rapid change quickly. The stability of lateral acceleration suppression is impaired. Therefore, the coefficient Kg in Table 9
More precisely, r ₂ greatly changes with respect to changes in the vehicle speed Vs when the vehicle speed Vs is low, and is constant when the vehicle speed Vs is equal to or higher than a predetermined value. That is, when the vehicle speed Vs is low, the weight of the differential term largely changes with respect to the vehicle speed variation, but when the vehicle speed Vs is high, the differential term weight does not change with respect to the vehicle speed variation.

The calculated CGR is a roll correction amount for the suspension, and Kgr ₃ is a weighting coefficient for the pitch correction amount CGP and the roll correction amount GES described later,
When the vehicle speed Vs is low, the change rate of the lateral acceleration Rg is low, so the contribution ratio of this roll correction amount CGR is lowered in the low speed range.
The coefficient data Kgr ₃ corresponding to the vehicle speed Vs is stored in one area (table 10) of the internal ROM so as to have a constant value in the high speed range. The CPU 17 reads the coefficient Kgr ₃ corresponding to the speed Vs and uses it for the above-described calculation of CGR.

Next, the CPU 17 converts the calculated pitch correction amount CGP, roll correction amount CGR, and roll correction amount DES into a pressure correction amount for each suspension, and this pressure correction amount is first subjected to "vehicle height deviation calculation" ( 31) Value EHf _L , EHfr, EHr _L , EHrr
Add to (registers EHf _L , EHfr, EHr _L , EHrr contents),
The obtained sum Ehf _L , Ehfr, Ehr _L , Ehrr is set to the register EHf _L , EHfr, EHr _L ,
Update and write to EHrr (66).

Ehf _L = EHf _L + Kgf _L · (1/4) · (-CGP + Kcgrf · CGR + Kg
ef _L・ GES) Ehfr ＝ EHfr ＋ Kgfr ・ (1/4) ・ (-CGP-Kcgrf ・ CGR ＋ Kg
efr ・ GES) Ehr _L ＝ EHr _L ＋ Kgr _L・ (1/4) ・ (CGP ＋ Kcgrr ・ CGR ＋ Kger
_L・ GES) Ehrr = EHrr ＋ Kgrr ・ (1/4) ・ (CGP ＋ Kcgrr ・ CGR ＋ Kger
r · GES) The first term on the right-hand side of the above equation is the value that was previously calculated in “Vehicle height deviation calculation” (31) and was written in the registers EHf _L , EHfr, EHr _L , EHrr. Yes, the second term on the right-hand side represents the above-mentioned pitch correction amount CGP, roll correction amount CGR, and roll correction amount GES,
It is a value converted into a pressure correction value for each suspension. Note that the coefficients of the second term on the right side Kgf _L , Kgfr, Kgr _L and Kgrr
Is Kgf _L ＝ Kf _L・ Kgs, Kgfr ＝ Kfr ・ Kgs, Kgr _L ＝ Kr _L・ Kgs, Kgrr ＝ Krr ・ Kgs, and Kf _L , Kfr, Kr _L , Krr are of each suspension with respect to the pressure reference point. A coefficient for correcting a pressure error due to a variation in the pipe length (a pipe length correction coefficient), and Kgs is a coefficient that is predetermined in association with the steering angular velocity Ss, as shown in Table 12. "Vehicle height deviation calculation" (31)
The pressure correction value calculated in “Pitching / rolling prediction calculation” (32) for the pressure correction value calculated in Step 3 to suppress acceleration change (the second term on the right side of the above equation: (1/4)
(-CGP-Kcgrf / CGR + Kgef _L / GES) etc.) is specified. If the steering angular velocity Ss is large, a rapid acceleration change is expected, and it is preferable to increase the weighting of the pressure correction value for suppressing the acceleration change. Therefore, the coefficient Kgs is generally set to be large in proportion to the steering angular velocity Ss. However, the steering angular velocity Ss is below a certain level (Sse ° /
(msec or less), the change in acceleration is extremely small, and if it exceeds Sse and Ssf ° / msec or less, the acceleration changes at a speed substantially proportional to the steering angular speed Ss. At steering angular velocities of Ssf and above, changes in turning radius are rapid and extremely large, and acceleration changes (especially lateral acceleration) are extremely large. An excessive amount of correction that quickly compensates for such rapid acceleration changes is
The stability of acceleration control is lost. Therefore, the steering angular velocity
The weighting coefficient Kgs corresponding to Ss is a constant value when Ss is Sse or less, a high value that is substantially proportional to Ss when Ss is more than Sse and less than Ssf, and a constant value at Ssf when Ssf is exceeded.

Next, the CPU 17 writes the initial pressure data written in the initial pressure registers PFL ₀ , PFR ₀ , PRL ₀ and PRR ₀ (set in steps 16 to 18).
Is the sum of the correction pressure for the vehicle height deviation adjustment and the correction pressure for the acceleration suppression control (register
EHf _L , EHfr, EHr _L , EHrr)) to calculate the pressure to be set for each suspension and register EHf _L , EHf
Update and write to r, EHr _L and EHrr (67).

Explaining the contents of the "pressure correction" (33) with reference to FIG. 10c, the CPU 17 determines that the output pressure of the pressure control valve due to the line pressure fluctuation corresponding to the detected pressure Dph of the pressure sensor 13rm (contents of the register DPH). The correction value PH that compensates for the fluctuation of
Read from area (table 13H) and pressure sensor 1
The correction value PLf (front wheel side correction value) and PLr (rear wheel side correction value) that compensate for the fluctuation of the output pressure of the pressure control valve due to the fluctuation of the return pressure corresponding to the detected pressure Dp _L (content of register DPL) of 3rt are set. Pressure correction value that is read from one area of internal ROM (table 13L) and compensates for fluctuations in pressure control valve output pressure due to fluctuations in line pressure and return pressure applied to the pressure control valve
Calculate PDf = PH-PLf and PDr = PH-PLr (68,6
9). The correction value corresponding to the return pressure is divided into the front wheel side and the rear wheel side because the front wheel side is close to the reservoir, the rear wheel side is far from the reservoir, and the pressure sensor 13rt for low pressure detection is the rear wheel side return. Since the pressure is detected, the return pressure difference between the rear wheel side and the front wheel side is relatively large, so that the error due to this is reduced. Table 13L stores two groups, a correction value data group assigned to the rear wheel side and a correction value data group assigned to the front wheel side, the latter data for the front wheel side suspension and the former data for the rear wheel side suspension. A correction value corresponding to the pressure detected by the pressure sensor 13rt at that time is read from the group.

After calculating the correction values PDf and PDr, the CPU 17 updates and writes these correction values in the registers EHf _L , EHfr, EHr _L , EHrr in addition to the contents of the registers EHf _L , EHfr, EHr _L , EHrr (7
0).

Explaining the contents of the "pressure / current conversion" (34) with reference to Fig. 10d, the CPU 17 determines the pressure indicated by the data EHf _L , EHfr, EHr _L and EHrr of the registers EHf _L , EHfr, EHr _L and EHrr. Pressure control valves 80f _L , 80fr, 80r _L and 80
The current values Ihf _L , Ihfr, Ihr _L and Ihrr to be passed to rr are read from the pressure / current conversion table 1 and written in the current output registers IHf _L , IHfr, IHr _L and IHrr, respectively (34).

The content of the warp correction (35) will be described with reference to FIG. 10e. This warp correction (35) is applied to lateral acceleration Rg and steering angular velocity.
Calculate the appropriate target warp DWT from Ss (73), and
Calculate the warp that appears when the contents of the above-mentioned registers IHf _L , IHfr, IHr _L , and IHrr are output, and calculate the target warp
Calculating the error warp amount for DWT (74 to 76), the error warp amount required to zero, the current correction value dIf _L, d
Ifr, dIr _L, calculates the DIRR (77), these current correction value register IHF _L, adds IHfr, IHr _L, the content of IHrr, updates writes the sum to these Digista (78).

The warp target value Idr corresponding to the lateral acceleration Rg is written in one area (table 14) of the internal ROM of the CPU 17, and the warp target value Ids corresponding to the steering angular velocity Ss is written in the table 15. , Table 16 is written with the warp correction amount Idrs corresponding to the vehicle longitudinal inclination and lateral acceleration Rg (lateral inclination) defined by the values of the registers IHf _L , IHfr, IHr _L , and IHrr to be output. There is. The front-back inclination is expressed by K = | (Ihf _L + Ihfr) / (Ihr _L + Ihrr) |, and the data group corresponding to this K is written in Table 16, and each data of each data group is It is associated with the acceleration Rg.

The CPU 17 reads the warp target value Idr corresponding to the lateral acceleration Rg from the table 14, the warp target value Idr corresponding to the steering angular velocity Ss, and the registers IHf _L , IHfr, IHr.
Vehicle longitudinal inclination and lateral acceleration specified by the values of _L and IHrr
Table 16 shows the warp correction amount Idrs corresponding to Rg (lateral inclination).
Then, the warp target value DWT is calculated from the following equation (73).

DWT = Kdw ₁ · Idr + Kdw ₂ · Ids + Kdw ₃ · Idrs CPU17 then writes the contents of registers IHf _L , IHfr, IHr _L and IHrr to Ih
Calculate the warp (Ihf _L −Ihfr) − (Ihr _L −Ihrr) specified by f _L , Ihfr, Ihr _L , Ihrr and check whether it is within the allowable range (dead zone) ( 74) If it is outside the allowable range, write the value obtained by subtracting the calculated warp (Ihf _L −Ihfr) − (Ihr _L −Ihrr) from the target warp DWT to the warp error correction amount register DWT (75), within the allowable range. When, the contents of register DWT (DWT) are not changed.
Then, the warp error correction amount DWT (contents of register DWT)
, The weighting coefficient Kdw ₄ is multiplied, and the product is updated and written in the register DWT (76), and this warp error correction amount DWT is set to the suspension pressure correction amount (correctly, the pressure control valve corresponding to the pressure correction amount). (77) and convert the corresponding amount to the current output registers IHf _L , IHfr, IHr _L and IH
Add to the contents of rr (78).

These current output registers IHf _L , IHfr, IHr _L and IHrr
Data is transferred to the CPU 18 by the "output" (36) subroutine addressed to the pressure control valves 80f _L , 80fr, 80rr and 80rr, and the CPU 18 gives it to the duty controller 32.

[Effect] As described above, according to the present invention, the detected vehicle height information (DHT) is subjected to digital filter processing, and the vehicle height detection means (15f _L , 15fr, 15r _L , 15rr) fails. Sometimes the cutoff frequency of the filter is lowered, so even when a sudden change appears in DHT, that change is smoothed and affects the value of the differential term, so there is no risk of an abnormally large differential term value being generated. Therefore, it is possible to prevent the suspension from being shocked.

[Brief description of drawings]

FIG. 1 is a block diagram showing a hydraulic circuit of a suspension control device according to an embodiment of the present invention. 2, 3, 4, 5, 6 and 7 are respectively the suspension 100fr, pressure control valve 80fr, cut valve 70fr, relief valve 60fr and main check shown in FIG. FIG. 5 is an enlarged vertical sectional view of a valve 50 and a bypass valve 120. 8a and 8b are block diagrams showing a configuration of an electric control system for controlling the suspension control device shown in FIG. 9a and 9b are flowcharts showing the control operation of the microprocessor 17 shown in FIG. Figures 10a, 10b, 10c, 10d, 10e and 1
FIG. 0f is a flow chart showing the contents of the subroutine shown in FIG. 9b. 11a and 11b are graphs showing the contents of data written in the internal ROM of the CPU 17. 1: Pump, 2: Reservoir, 3: High pressure port 4: Attenuator, 6: Front wheel high pressure supply pipe, 7: Accumulator 8: High pressure supply pipe, 9: Rear wheel high pressure supply pipe, 10: Accumulator 11: Reservoir return pipe , 12: Drain return pipe 13f _L , 13fr, 13r _L , 13rr, 13rm, 13rt: Pressure sensor 14f _L , 14fr, 14r _L , 14rr: Air release drain 15f _L , 15fr, 15r _L , 15rr: Height sensor, 16p, 16r: Accelerometer 17, 18: Microprocessor, 19: Battery 50: Main check valve 51: Valve base, 52: Input port, 53: Output port 54: Valve seat, 55: Flow port 56: Compression coil spring , 57: Ball valve 60fr, 60f _L , 60rr, 60r _L : Relief valve, 61: Valve base 62: Input port, 63: Low pressure port, 64: 1st guide 65: Filter, 66: Valve body, 67: 2nd Guide 68: valve body, 69: compression coil spring 60 m: main relief valve _{70fr, 70f L, 70rr, 70r} L: cut valve 71: valve body, 72: line圧Po DOO, 73: tone pressure input port 74: the oil discharge port, 75: output port, 76: first guide 77: guide, 78: spool 79: compression coil spring _{80fr, 80f L, 80rr, 80r} L: pressure control valve 81 : Sleeve, 82: Line pressure port, 83: Groove 84: Output port, 85: Low pressure port, 86: Groove 87: High pressure port, 88: Target pressure space, 88f: Orifice 89: Low pressure port, 90: Spool, 91: Groove 92: Compression coil spring, 93: Valve body 94: Flow path, 95: Needle valve, 96: Fixed core 97: Plunger, 98a: Yoke, 98b: End plate 98c: Low pressure port 100fr, 100f _L , 100rr, 100r _L : Suspension 101fr, 101f _L , 101rr, 101r _L : Shock absorber 102fr, 102f _L , 102rr, 102r _L : Piston rod 103: Piston, 104: Inner cylinder, 105: Upper chamber 106: Lower chamber, 107: Side port, 108 : Vertical through port 109: Damping valve device, 110: Lower space, 111: Piston 112: Lower chamber, 113: Upper chamber, 114: Outer cylinder 120: Bypass valve, 121: Input port 122: Low pressure port, 122a: Low pressure port Port, 122b: flow path 123: first guide, 124a: valve body 124b: compression coil spring, 125: needle valve 150: A / D conversion unit 170: duty control unit (duty controller) 180: current detection unit, 190.200 : Driver RY: Relay, SW1: Ignition switch SW2: Vehicle speed sensor (lead switch) SW3: Stop lamp switch, SW4: Door switch SW5: Reservoir level warning switch SW6: Vehicle height adjustment switch, SN1: Steering sensor SN2: Throttle sensor SOL1 ~ SOL5: Solenoid

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kunihito Sato 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation (72) Inventor Takeshi Goto 1, Toyota Town, Aichi Prefecture, Toyota Motor Corporation (72) Inventor Takashi Yonekawa 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. (72) Inventor Toshio Yutani, 1 Toyota Town, Toyota City, Aichi Toyota Motor Company, Ltd. Examiner, Shogo Oshima (56) Reference Reference JP 62-283010 (JP, A)

Claims (1)

(57) [Claims] 1. A suspension mechanism including an actuator that expands and contracts according to the supply and discharge of hydraulic oil; a vehicle height detection unit that detects a vehicle height change due to expansion and contraction of the actuator; a pressure source unit that supplies hydraulic oil to the actuator. Adjustment valve means for controlling supply / discharge of hydraulic oil from the pressure source means to the actuator; a value of the detected vehicle height detected by the vehicle height detection means is passed through a digital filter process to remove a predetermined high frequency change component. Then, based on the difference between the processing result and the control target value, a control amount for making the difference substantially zero is calculated by a feedback calculation including at least a proportional term and a derivative term, and the adjusting valve means is operated accordingly. Feedback control means for adjusting; and whether or not there is an abnormality in the vehicle height detection means. To adjust the parameters,
A suspension control device comprising: an electronic control unit that lowers a cutoff frequency of the filtering process as compared with a normal time.