JP2007145093A - Vehicle height adjusting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To change a vehicle height in a short time, and prevent impact noises attendant on movement of working oil, and fluctuation of the vehicle height. <P>SOLUTION: Hydraulic cylinders 20a-20d are installed between wheel side members 11a-11d and vehicle body side members 12a-12d of a vehicle. The working oil is supplied to the hydraulic cylinders 20a-20d via oil paths L1a-L1d, so as to adjust the vehicle height. Accumulators 15a-15d are connected with the oil paths L1a-L1d via electromagnetic switch valves 16a-16d for switching a spring constant. The electromagnetic switch valves 16a-16d are constituted in a normally-open-type set to a closed state by energization, and is set to the closed state even under a non-energized condition under a condition that a differential pressure between the hydraulic pressure in the accumulators 15a-15d and the hydraulic pressure in the hydraulic cylinders 20a-20d is larger than a biasing force of springs built in the electromagnetic switch valves 16a-16d. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle height adjusting device that changes a vehicle height by supplying and discharging fluid to and from a fluid pressure cylinder provided between a wheel side member and a vehicle body side member of the vehicle.

Conventionally, a fluid pressure cylinder provided between a wheel side member and a vehicle body side member of a vehicle and capable of changing the vehicle height by supplying and discharging fluid, and supplying and discharging fluid to and from the fluid pressure cylinder via a fluid passage. A vehicle height adjusting device including a fluid supply / discharge device to be controlled is well known. In this vehicle height adjusting device, for example, as shown in Patent Document 1 below, an accumulator is connected to a fluid passage so as to apply a spring force to the vertical movement of the vehicle body. When a normally open type electromagnetic switching valve is interposed between the fluid passage and the accumulator, the fluid in the hydraulic cylinder is quickly discharged with the electromagnetic switching valve closed when the vehicle height is lowered. The vehicle body can be lowered to a target low position in a short time. In addition, when raising the vehicle height to a high position, supply the fluid to the fluid pressure cylinder with the electromagnetic switching valve closed to raise the vehicle height to a predetermined position and then open the electromagnetic switching valve. To supply fluid to the fluid pressure cylinder and accumulator and raise the vehicle height to the target high position, or supply the fluid to the fluid pressure cylinder and accumulator with the electromagnetic switching valve open from the beginning to achieve the vehicle height. I try to raise it to a higher position.
JP 2005-88766 A

  However, in the above-described conventional apparatus, when the vehicle height is lowered in a short time and the energization to the electromagnetic switching valve is stopped, the electromagnetic switching valve opens and the fluid in the accumulator moves to the fluid pressure cylinder. However, there is a problem that the movement of the fluid causes the generation of impact sound due to the fluid and the fluctuation of the vehicle height. In addition, when raising the vehicle height, it is necessary to re-supply the fluid to the accumulator or supply the fluid to both the fluid pressure cylinder and the accumulator at the same time, and it takes time to raise the vehicle height to the target high position. Cost. In order to shorten the rising time of the vehicle height, a pump with a large discharge amount is required, and the entire apparatus cannot be increased in size and weight, and the manufacturing cost is increased accordingly.

  The present invention has been made to cope with the above-described problems, and its object is to make it possible to change the vehicle height in a short time without causing an increase in the size and weight of the apparatus, and the impact caused by the movement of the fluid. It is an object of the present invention to provide a vehicle height adjusting device that can prevent the generation of sound and the fluctuation of the vehicle height.

  In order to achieve the above object, the present invention is characterized in that a fluid pressure cylinder provided between a wheel side member and a vehicle body side member of a vehicle and capable of changing a vehicle height by supplying and discharging a fluid, and a fluid pressure cylinder Vehicle height adjustment comprising a fluid supply / discharge device that controls supply / discharge of fluid through the fluid passage, an accumulator connected to the fluid passage, and an electromagnetic switching valve interposed between the fluid passage and the accumulator In the apparatus, the electromagnetic switching valve is configured as a normally open type that is set to a closed state by energization, the fluid pressure in the accumulator is higher than the fluid pressure in the fluid pressure cylinder, and the pressure difference between them is higher than a predetermined value. On the condition that it is large, it is configured to be set to a closed state even in a non-energized state.

  In this case, for example, the electromagnetic switching valve has a spring and urges the valve body in the direction opposite to the direction in which the valve body is seated on the valve seat by the fluid pressure in the fluid pressure cylinder and the spring force of the spring. It is good to be comprised so that a valve body may be urged | biased in the direction seated on a valve seat with the internal fluid pressure. The spring urging force when the valve body is seated on the valve seat is F, the seal area of the valve body when the valve body is seated on the valve seat is A, and the vehicle height is set high. If the fluid pressure difference obtained by subtracting the fluid pressure in the fluid pressure cylinder when the vehicle height is set to a low state from the fluid pressure in the fluid pressure cylinder is ΔPo, the relationship ΔPo · A> F is established. Good.

  When the vehicle height is actually lowered from a high position to a low position using the vehicle height adjustment device configured as described above, the vehicle height is controlled by discharging the fluid in the fluid pressure cylinder by controlling the fluid supply / discharge device. A lowering control means for lowering is provided. Then, when the fluid pressure difference obtained by subtracting the fluid pressure in the fluid pressure cylinder from the fluid pressure in the accumulator and the fluid pressure difference that changes as the vehicle height decreases is ΔPx, the decrease control means starts from the decrease in vehicle height. The energization control of the electromagnetic switching valve is preferably performed in a period in which at least the relationship of ΔPx · A ≦ F is satisfied within the period until the end of the decrease. Note that the energization control of the electromagnetic switching valve at least during a period in which the relationship of ΔPx · A ≦ F is satisfied means that the energization control of the electromagnetic switching valve is performed during the entire period from the start to the end of the decrease in vehicle height. is there.

  Further, when the vehicle height adjustment device configured as described above is used to actually raise the vehicle height from a low position to a high position, the vehicle is controlled by supplying fluid to the fluid pressure cylinder by controlling the fluid supply / discharge device. A raising control means for raising the height is provided. Then, when the fluid pressure difference, which is the fluid pressure difference obtained by subtracting the fluid pressure in the fluid pressure cylinder from the fluid pressure in the accumulator and changes as the vehicle height rises, is ΔPy, the ascent control means The energization control of the electromagnetic switching valve is preferably performed in a period in which at least the relationship of ΔPy · A ≦ F is established within the period until the end of the rise. It should be noted that the energization control of the electromagnetic switching valve in a period in which at least the relationship of ΔPy · A ≦ F is satisfied includes the energization control of the electromagnetic switching valve in all the periods from the start to the end of the vehicle height. is there.

  According to the present invention, when the vehicle height is lowered from a high position to a low target position, it is only necessary to discharge the fluid only in the fluid pressure cylinder by closing the electromagnetic switching valve by energization. High can be reduced in a short time. Even if the electromagnetic switching valve is de-energized after the vehicle height has been lowered to the target low position, the electromagnetic switching valve is caused by the pressure difference between the fluid pressure in the accumulator and the fluid pressure in the fluid pressure cylinder. Can be kept closed. Therefore, even after energization of the electromagnetic switching valve is stopped, the fluid in the accumulator does not move to the fluid pressure cylinder, and it is possible to avoid the generation of impact sound and fluctuations in the vehicle height due to the movement of the fluid. Also, when raising the vehicle height from a low position to a target high position, as described above, the electromagnetic switching valve is kept closed even after the vehicle height reduction control, and the fluid in the accumulator is kept at a high pressure. Therefore, both the fluid pressure cylinder and the accumulator require a small amount of fluid to set the vehicle height to a target high state, and the vehicle height is set to a high target without preparing a large discharge pump. It can be raised to the position in a short time.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a vehicle suspension apparatus including a vehicle height adjusting apparatus according to the present invention.

  This vehicle suspension apparatus includes a fluid between a wheel side member (for example, a lower arm) 11a to 11d that holds front and rear, left and right wheels Wfl, Wfr, Wrl, and Wrr, and a vehicle body side member 12a to 12d that is integrally displaced with the vehicle body. Pressure cylinders 20a to 20d are respectively provided. The fluid pressure cylinders 20a to 20d are respectively provided with cylindrical housings 21a to 21d whose upper ends are fixed to the vehicle body side members 12a to 12d. In the housings 21a to 21d, pistons 22a to 22d that slide in a liquid-tight manner in the axial direction are accommodated, respectively. The pistons 22a to 22d partition the housings 21a to 21d into upper oil chambers 23a to 23d and lower oil chambers 24a to 24d, respectively. The pistons 22a to 22d are provided with orifices 25a to 25d that allow the upper oil chambers 23a to 23d and the lower oil chambers 24a to 24d to communicate with each other.

  Upper ends of piston rods 26a to 26d are fixed to the pistons 22a to 22d, respectively. The piston rods 26a to 26d have their lower portions protruding from the housings 21a to 21d so as to be able to advance and retreat, and their lower ends are connected to the wheel side members 11a to 11d. A coil spring (not shown) is provided between the outer peripheral surfaces of the housings 21a to 21d and the vehicle body side members 12a to 12d, and the fluid pressure cylinders 20a to 20d together with the coil springs have a vehicle body with respect to the wheel side members 11a to 11d. Is supported so that it can vibrate up and down. In the vertical vibration of the vehicle body, a damping force is applied by the movement of the hydraulic oil between the upper and lower oil chambers 23a to 23d and 24a to 24d through the orifices 25a to 25d.

  One ends of oil passages L1a to L1d are connected to the upper oil chambers 23a to 23d of the fluid pressure cylinders 20a to 20d via variable orifices 13a to 13d, respectively. The variable orifices 13a to 13d are electrically controlled to change the passage area of the hydraulic oil. The oil passages L1a to L1d are connected to accumulators 14a to 14d and accumulators 15a to 15d, respectively, which provide a spring action with respect to the vertical movement of the vehicle body. The accumulators 14a to 14d and 15a to 15d have a housing and a partition member for partitioning the inside of the housing. Each chamber communicates with the oil passages L1a to L1d, and an elastic body is accommodated in each other chamber. They all have a spring function. As the accumulators 14a to 14d and 15a to 15d, any of a bellows type, a bladder type, and a piston type may be adopted. The spring constants of the accumulators 15a to 15d are set larger than the spring constants of the accumulators 14a to 14d.

  Between the accumulators 15a to 15d and the oil passages L1a to L1d, electromagnetic switching valves 16a to 16d for switching the spring constant are interposed. As shown in detail in FIG. 2, the electromagnetic switching valves 16 a to 16 d include a housing 31 in which a stepped columnar space 31 a is formed. A sleeve 32 is fixed to the housing 31 with a tip portion entering the cylindrical space 31a. A cylindrical support rod 33, which is fixed by allowing the rear portion to enter the cylindrical space 31 a, enters the inner circumferential surface of the sleeve 32 and is fixed. A cylindrical valve seat member 34 is assembled and fixed to the front portion of the support rod 33. A valve body 35 is incorporated in the internal space of the support rod 33 so as to face the valve seat portion 34 a of the valve seat member 34. The valve body 35 is fixed to a distal end portion of a drive rod 36 that is slidably incorporated in the support rod 33 in the axial direction.

  A coiled spring 37 is assembled between the tip of the drive rod 36 and the valve seat member 34. The spring 37 urges the drive rod 36 and the valve body 35 rearward (rightward in the drawing). A pusher (movable element) 38 that can be displaced in the axial direction in the sleeve 32 is fixed to the rear end portion of the drive rod 36. The plunger 38 is attracted forward (leftward in the figure) by energization of the coil 39 wound around the outside of the sleeve 32, and urges the drive rod 36 and the valve body 35 forward (leftward in the figure). The passage to the valve seat member 34 in the cylindrical space 31a and the passage in the valve seat member 34 communicate with the oil passages L1a to L1d, that is, the fluid pressure cylinders 20a to 20d via the oil passage 31b provided in the housing 31. Yes. The passage (passage on the valve element 35 side) facing the valve seat 34 a in the support rod 33 is an accumulator through an oil passage 33 a provided through the side wall of the support rod 33 and an oil passage 31 c provided in the housing 31. It communicates with 15a-15d. The sleeve 32 has a passage (passage on the valve element 35 side) facing the valve seat 34 a in the support rod 33 through the space between the inner peripheral surface of the support rod 33 and the outer peripheral surface of the drive rod 36. Communicate.

  In the electromagnetic switching valves 16a to 16d configured as described above, even when other forces are applied, the drive rod 36 and the valve element 35 are always displaced in the left direction in FIG. The valve body 35 is seated on the valve seat portion 34a and the oil passages 31b and 31c are always closed (see FIG. 3B). On the other hand, in the state where the power supply to the coil 39 is stopped, unless the force resulting from the differential pressure obtained by subtracting the oil pressure of the oil passage 31b from the oil pressure of the oil passage 31c is larger than the urging force of the spring 37, the drive rod 36 and the valve body 35 is displaced rightward in FIG. 2 by the urging force of the spring 37, and the valve body 35 is not seated on the valve seat portion 34a (see FIG. 3A). However, if the force resulting from the differential pressure is greater than the biasing force of the spring 37, the differential pressure overcomes the biasing force of the spring 37 even when the coil 39 is not energized, and the valve body 35 It sits on the part 34a (see FIG. 3C). Thus, the electromagnetic switching valves 16a to 16d function as normally open electromagnetic switching valves that are set to a closed state by energization, and the hydraulic pressure in the accumulators 15a to 15d is higher than the hydraulic pressure in the fluid pressure cylinders 20a to 20d. It functions to be set to a closed state even in a non-energized state on condition that the pressure difference is high and each pressure difference is larger than a predetermined value.

  More specifically, the electromagnetic switching valves 16a to 16d urge the valve body 35 in the direction opposite to the direction in which the valve body 35 is seated on the valve seat portion 34a by the oil pressure of the oil passage 31b and the spring force of the spring 37, and the oil passage The valve body 35 is seated on the valve seat 34a by the hydraulic pressure 31c and is urged in the direction. Therefore, when the energization to the coil 39 is stopped, the open / close states of the electromagnetic switching valves 16a to 16d are determined by the balance between the spring force of the spring 37 and the oil pressure of the oil passages 31b and 31c. In the electromagnetic switching valves 16a to 16d, the urging force of the spring 37 when the valve body 35 is in the position seated on the valve seat portion 34a is F, and the valve body 35 is seated on the valve seat portion 34a. In the fluid pressure cylinders 20a to 20d when the vehicle height is set to a low state from the oil pressure P2 in the fluid pressure cylinders 20a to 20d when the seal area of the valve body 35 is A and the vehicle height is set to a high state. If the hydraulic pressure difference obtained by subtracting the hydraulic pressure P1 is ΔPo, the relationship ΔPo · A> F is established (see FIG. 5). As will be described in detail later, in this suspension device, the vehicle height is raised and lowered by supplying and discharging hydraulic oil to and from the fluid pressure cylinders 20a to 20d, and the hydraulic oil is supplied to the fluid pressure cylinders 20a to 20d. The vehicle height is set high with the hydraulic pressure in the upper and lower oil chambers 23a to 23d and 24a to 24d being increased, the hydraulic oil in the fluid pressure cylinders 20a to 20d is discharged, and the upper and lower oil chambers 23a to 23d and 24a to 24d are discharged. The vehicle height is set low while the hydraulic pressure of the vehicle is low.

  The fluid pressure cylinders 20a to 20d are connected to the center cylinder 17 via oil passages L1a to L1d. The center cylinder 17 includes a stepped cylindrical housing 17a having a central portion with a large diameter and both side portions with a small diameter. Inside the housing 17a, a large-diameter first piston 17b and small-diameter second and third pistons 17e integrally connected at both axial positions of the first piston 17b via connecting rods 17c and 17d, 17f is accommodated in a liquid-tight and slidable manner.

  The function of the center cylinder 17 will be briefly described. When pitching occurs in the vehicle body, there is a difference between the hydraulic pressure in the fluid pressure cylinders 20a and 20b of the left and right front wheels Wfl and Wfr and the hydraulic pressure in the fluid pressure cylinders 20c and 20d of the left and right rear wheels Wrl and Wrr. In this case, both hydraulic pressures in the fluid pressure cylinders 20a and 20b communicating with the respective oil chambers on the outer sides of the second and third pistons 17e and 17f of the center cylinder 17 are equal, and both sides of the first piston 17b of the center cylinder 17 are the same. Both hydraulic pressures in the fluid pressure cylinders 20c and 20d communicating with the oil chambers are also equal. Therefore, the first to third pistons 17b, 17e, and 17f are not displaced, and there is no movement of the hydraulic oil between the fluid pressure cylinders 20a to 20d and the center cylinder 17. As a result, the fluid pressure cylinders 20a to 20d operate independently and generate a large damping force, so that the pitching of the vehicle body is effectively suppressed.

  When rolling occurs in the vehicle body, the sum of the hydraulic pressures in the fluid pressure cylinders 20a and 20c for the left front wheel Wfl and the left rear wheel Wrl and the hydraulic pressures in the fluid pressure cylinders 20b and 20d for the right front wheel Wfr and the right rear wheel Wrr. A difference arises from the sum of In this case, the hydraulic pressure in the fluid pressure cylinder 20a communicating with the oil chamber outside the second piston 17e of the center cylinder 17 and the hydraulic pressure within the fluid pressure cylinder 20c communicating with the oil chamber between the first and third pistons 17b and 17f. And the hydraulic pressure in the fluid pressure cylinder 20b communicating with the oil chamber outside the third piston 17f and the hydraulic pressure in the fluid pressure cylinder 20d communicating with the oil chamber between the first and second pistons 17b and 17e. The sum is equal. Therefore, the first to third pistons 17b, 17e, and 17f are not displaced, and there is no movement of the hydraulic oil between the fluid pressure cylinders 20a to 20d and the center cylinder 17. As a result, the fluid pressure cylinders 20a to 20d operate independently and generate a large damping force, so that rolling of the vehicle body is effectively suppressed.

  On the other hand, when only one of the left and right front and rear wheels Wfl, Wfr, Wrl, Wrr, for example, the left front wheel Wfl rides on a bump on the road, the hydraulic pressure of the fluid pressure cylinder 20a rapidly increases. In this case, since the hydraulic pressure in the other fluid pressure cylinders 20b to 20d is maintained as before, the oil pressure outside the second piston 17e of the center cylinder 17 increases as the hydraulic pressure of the fluid pressure cylinder 20a increases. Only the indoor hydraulic pressure rises, and the first to third pistons 17b, 17e, and 17f are displaced rightward in the drawing. Accordingly, the volume of the oil chamber outside the second piston 17e and the volume of the oil chamber between the first and second pistons 17b and 17e increase, and the oil chamber between the first and third pistons 17b and 17f, and The volume of the oil chamber outside the third piston 17f decreases. This is equivalent to the hydraulic oil in the fluid pressure cylinders 20a and 20d flowing into the fluid pressure cylinders 20b and 20c. As a result, the impact on the vehicle body caused by the left front wheel Wfl riding on the bump on the road. Is relaxed well.

  Even when other wheels ride on the bumps, the impact on the vehicle body is alleviated by the same action of the center cylinder 17 as described above. Further, when one of the left and right front and rear wheels Wfl, Wfr, Wrl, Wrr falls into a depression on the road contrary to the above, another hydraulic pressure is placed in the hydraulic cylinder of the wheel at the diagonal position. The hydraulic oil flows into the cylinder, and in this case as well, the impact on the vehicle body when it falls into the depression on the road is well mitigated. Since the function of the center cylinder 17 is not directly related to the present invention, the description thereof is omitted.

  This vehicle suspension device includes a fluid supply / discharge device that controls supply and discharge of hydraulic fluid to the fluid pressure cylinders 20a to 20d via the flow paths L1a to L1d in order to adjust the vehicle height. As will be described in detail later, the fluid supply / discharge device includes a pump 41 for supplying hydraulic oil to the fluid pressure cylinders 20a to 20d when raising the vehicle height. The pump 41 is driven by the electric motor 42 to pump up the hydraulic oil in the reservoir 43 and discharge the hydraulic oil to the oil passage L <b> 2 via the check valve 44. An accumulator 45 for silencing is connected to the oil passage L2, and an accumulator 47 for accumulating pressure is also connected via an electromagnetic switching valve 46. The electromagnetic switching valve 46 is a normally closed type that is set to an open state by energization. Between the oil passage L2 and the reservoir 43, a normally closed type outflow control electromagnetic switching valve 48 which is set in an open state by energization is interposed. As will be described in detail later, the electromagnetic switching valve 48 is for discharging hydraulic oil in the fluid pressure cylinders 20a to 20d when the vehicle height is lowered.

  The oil passage L2 communicates with the oil passages L1a to L1d via oil passages L3a to L3d having electromagnetic switching valves 51a to 51d for controlling the vehicle height. The electromagnetic switching valves 51a to 51d are normally closed types that are set to an open state by energization. Between the oil passages L3a and L3b, a normally closed electromagnetic switching valve 52a which is set to an open state by energization is connected on the oil passages L1a and L1b side. Between the oil passages L3c and L3c, a normally closed electromagnetic switching valve 52b that is set to an open state by energization is connected on the oil passages L1c and L1d side. These electromagnetic switching valves 52a and 52b are for energization control when the electromagnetic switching valves 16a to 16d are switched from the closed state to the open state to suppress the pulsation of the hydraulic oil accompanying the switching.

  Next, an electric control device that controls the various electric components described above will be described. The electric control device includes a plurality of pressure sensors P that are provided in various oil passages and detect oil pressure. The pressure detected by the pressure sensor P is supplied to an electronic control unit (hereinafter referred to as ECU) 60, and the ECU 60 performs various controls according to the detected pressure. However, since the control based on the detected pressure is not directly related to the present invention, detailed description thereof is omitted. Further, vehicle height sensors 61a to 61d are assembled between the wheel side members 11a to 11d and the vehicle body side members 12a to 12d, respectively. The vehicle height L at the position is detected and output to the ECU 60.

  The ECU 60 controls various electromagnetic switching valves, variable orifices 13a to 13d and the operation of the electric motor 42 by executing various programs including the vehicle height control program of FIG. A vehicle height mode switch 62, a vehicle height adjustment switch 63, and various sensors 64 are connected to the ECU 60. The vehicle height mode switch 62 is provided in the passenger compartment and is operated by the driver, and is used for switching between an automatic mode in which the vehicle height is automatically changed and a manual mode in which manual operation is performed. The vehicle height adjustment switch 63 is provided in the passenger compartment and is operated by the driver, and is used to instruct switching of the vehicle height when the manual mode is selected. The various sensors 64 detect the state of the vehicle and include a vehicle speed sensor, a shift position detection sensor, a parking brake sensor, a yaw rate sensor, a lateral acceleration sensor, and the like.

  The operation of the embodiment configured as described above will be described. By turning on the ignition switch, the ECU 60 repeatedly executes the vehicle height control program shown in FIG. 4 every predetermined short time. The execution of the vehicle height control program is started in step S10, and the ECU 60 determines whether there is a vehicle height down request or an up request in steps S11 and S12, respectively. For example, in the state where the manual mode is selected by the vehicle height mode switch 62, when an instruction to lower the vehicle height is issued by the vehicle height adjustment switch 63, it is determined that there is a down request. Further, when the vehicle is stopped with the auto mode selected by the vehicle height mode switch 62 and then the parking brake is operated or the shift lever is switched to the parking position, there is a down request. Determined. This is to make it easier for the passenger to get on and off the vehicle. On the other hand, when an instruction to increase the vehicle height is given by the vehicle height adjustment switch 63 while the manual mode is selected by the vehicle height mode switch 62, it is determined that there is an up request. In addition, when the auto mode is selected by the vehicle height mode switch 62 and the shift lever is switched to the drive position after turning on the ignition switch, it is determined that there is an up request. This is to return the vehicle height lowered for getting on and off the occupant to a higher position.

  If it is determined in steps S11 and S12 that both "No", that is, neither a vehicle height down request nor a vehicle up request is determined, the vehicle height control program is terminated in step S23. If it is determined in step S11 that "Yes", that is, there is a request for lowering the vehicle height, the ECU 60 energizes the electromagnetic switching valves 16a to 16d for switching the spring constant in step S13, and the electromagnetic switching valves 16a to 16d. 16d is set to the closed state. That is, as shown in FIG. 3B, when the coil 39 is energized, the plunger 38 is urged to the left, and the valve body 35 is displaced to the left together with the drive rod 36 and is seated on the valve seat 34a. . As a result, the electromagnetic switching valves 16a to 16d are set in a closed state. Next, in step S14, after a predetermined short time has passed since the energization start of the electromagnetic switching valves 16a to 16d, the vehicle height control electromagnetic switching valves 51a to 51d and the outflow control electromagnetic switching valve 48 are switched to. Energization is performed, and the electromagnetic switching valves 51a to 51d and 48 are set to an open state. As a result, the hydraulic oil in the fluid pressure cylinders 20a to 20d is discharged to the reservoir 43 via the oil passages L1a to L1d, L3a to L3d, and L2. As a result, as shown in FIG. 5, the vehicle height L at the positions of the left and right front and rear wheels Wfl, Wfr, Wrl, Wrr gradually decreases, and the hydraulic pressure in the fluid pressure cylinders 20a to 20d also gradually decreases.

  After the processing of step S14, the ECU 60 inputs the vehicle heights L detected by the vehicle height sensors 61a to 61d, and the vehicle heights L at the left and right front and rear wheels Wfl, Wfr, Wrl, Wrr are targeted. Judge whether it became equal to a low vehicle height value. The electromagnetic switching valves 51a to 51d, 48 are kept open and the electromagnetic switching valve 16a until each vehicle height L at each position of the left and right front and rear wheels Wfl, Wfr, Wrl, Wrr is equal to a target low vehicle height value. ˜16d is kept closed. When the vehicle heights L at the positions of the left and right front and rear wheels Wfl, Wfr, Wrl, Wrr are equal to the target low vehicle height value, the ECU 60 determines “Yes” in step S15, and in steps S16, S17. Execute the process.

  In step S16, the energization to the vehicle height control electromagnetic switching valves 51a to 51d and the outflow control electromagnetic switching valve 48 is released, and the electromagnetic switching valves 51a to 51d, 48 are set to a closed state. As a result, the discharge of the hydraulic oil in the fluid pressure cylinders 20a to 20d to the reservoir 43 is stopped, and the decrease in vehicle height at each of the left and right front and rear wheels Wfl, Wfr, Wrl, Wrr is stopped. In step S17, the energization of the electromagnetic switching valves 16a to 16d for switching the spring constant is canceled after a predetermined short time has elapsed since the energization stop of the electromagnetic switching valves 51a to 51d and 48. In this case, as shown in FIG. 5, the hydraulic pressures in the accumulators 15a to 15d are maintained at the hydraulic pressure P2 in the fluid pressure cylinders 20a to 20d when the vehicle height is set high. On the other hand, the hydraulic pressure in the fluid pressure cylinders 20a to 20d is a hydraulic pressure P1 set to a low vehicle height. Since the force due to the hydraulic pressure difference ΔPo (= P2−P1) is larger than the spring force F of the spring 37, the electromagnetic switching valves 16a to 16d are maintained in the closed state even after the energization is released (FIG. 3 ( C)). As a result, the hydraulic pressure in the accumulators 15a to 15d continues to be maintained at a high hydraulic pressure P2.

  The processing in steps S15 to S17 is performed for each of the left and right front and rear wheels Wfl, Wfr, Wrl, Wrr. When the vehicle height at one wheel position reaches a target vehicle height, the vehicle height The energization of each one of the electromagnetic switching valves 51a to 51d for control and the electromagnetic switching valves 16a to 16d for switching the spring constant corresponding to the one wheel is stopped. When the vehicle heights at all the wheel positions reach the target vehicle height, the energization of the electromagnetic switching valve 48 for outflow control is controlled to stop.

  Thus, when lowering the vehicle height from a high position to a target low position, it is only necessary to discharge the hydraulic oil only in the fluid pressure cylinders 20a to 20d by closing the electromagnetic switching valves 16a to 16d by energization. Therefore, the vehicle height can be reduced in a short time. And even if energization to electromagnetic switching valves 16a-16d is stopped after this vehicle height is lowered to a target low position, the hydraulic pressure in accumulators 15a-15d and the hydraulic pressure in fluid pressure cylinders 20a-20d are reduced. Due to the hydraulic pressure difference, the electromagnetic switching valves 16a to 16d can be kept closed. Accordingly, even after the energization of the electromagnetic switching valves 16a to 16d is stopped, the hydraulic oil in the accumulators 15a to 15d does not move to the fluid pressure cylinders 20a to 20d, impact noise is generated due to the movement of the hydraulic oil, and the vehicle height fluctuates. Can be avoided.

  Next, a case where the vehicle height is switched from a low state to a high state will be described. When there is a request for increasing the vehicle height as described above, the ECU 60 determines “Yes” in step S12, and in step S18, similarly to the processing in step S13, electromagnetic switching for switching the spring constant is performed. The valves 16a to 16d are energized to set the electromagnetic switching valves 16a to 16d in a closed state. Next, in step S19, after a predetermined short period of time has elapsed from the start of energization of the electromagnetic switching valves 16a to 16d, the electromagnetic switching valves 51a to 51d for vehicle height control are set to an open state by energization, and the electric motor The operation of the pump 41 is started by operating 42. As a result, the hydraulic oil discharged from the pump 41 is supplied to the fluid pressure cylinders 20a to 20d via the oil passages L2, L3a to L3d, and L1a to L1d. As a result, as shown in FIG. 5, the vehicle height L at each of the left and right front and rear wheels Wfl, Wfr, Wrl, Wrr gradually increases, and the hydraulic pressure in the fluid pressure cylinders 20a to 20d also gradually increases.

  After the process of step S19, the ECU 60 inputs the vehicle heights L detected by the vehicle height sensors 61a to 61d, and the vehicle heights L at the left and right front and rear wheels Wfl, Wfr, Wrl, Wrr are targeted. It is determined whether the vehicle height value is equal. The electromagnetic switching valves 51a to 51d are maintained in an open state and the pump 41 is maintained in an operating state until each vehicle height L at each position of the left and right front and rear wheels Wfl, Wfr, Wrl, Wrr is equal to a target high vehicle height value. The electromagnetic switching valves 16a to 16d are maintained in the closed state. When the vehicle height L at each position of the left and right front and rear wheels Wfl, Wfr, Wrl, Wrr becomes equal to the target high vehicle height value, the ECU 60 determines “Yes” in step S20, and in steps S21, S22. Execute the process.

  In step S21, the energization of the vehicle height control electromagnetic switching valves 51a to 51d is released, and the electromagnetic switching valves 51a to 51d are set in a closed state. Further, the operation of discharging the hydraulic oil from the pump 41 is stopped by stopping the operation control for the electric motor 42. As a result, the supply of hydraulic oil to the fluid pressure cylinders 20a to 20d is stopped, and the increase in vehicle height at each of the left and right front and rear wheels Wfl, Wfr, Wrl, and Wrr is stopped. In step S22, energization of the electromagnetic switching valves 16a to 16d for switching the spring constant is canceled after the electromagnetic switching valves 51a to 51d are set in a closed state and a predetermined short time has elapsed since the pump 41 was stopped. In this case, as shown in FIG. 5, the hydraulic pressures in the accumulators 15a to 15d are equal to the hydraulic pressure P2 in the fluid pressure cylinders 20a to 20d, and there is no difference between these hydraulic pressures. ˜16d are switched to the open state (see FIG. 3A). As a result, the fluid pressure cylinders 20a to 20d and the accumulators 15a to 15d communicate with each other via the variable orifices 13a to 13d, and the spring force by the accumulators 15a to 15d acts on the vertical movement of the vehicle body.

  The processing in steps S20 to S22 is also performed for each of the left and right front and rear wheels Wfl, Wfr, Wrl, Wrr. When the vehicle height at one wheel position reaches a target vehicle height, the vehicle height The energization of each one of the electromagnetic switching valves 51a to 51d for control and the electromagnetic switching valves 16a to 16d for switching the spring constant corresponding to the one wheel is stopped. And when the vehicle height of all the wheel positions reaches the vehicle height with a low target, the discharge operation of the hydraulic oil of the pump 41 is also stopped by the operation stop control of the electric motor 42.

  Thus, when raising the vehicle height from a low position to a target high position, as described above, the electromagnetic switching valves 16a to 16d for switching the spring constant are kept closed even after the lowering control. Since the hydraulic oil in the accumulators 15a to 15d is kept at a high pressure, the amount of hydraulic oil necessary for both the fluid pressure cylinders 20a to 20d and the accumulators 15a to 15d to set the vehicle height to a target high state is The vehicle height can be raised to a target high position in a short time without preparing a pump 41 having a large discharge amount.

  Furthermore, the present invention is not limited to the above-described embodiment, and various modifications can be employed within the scope of the present invention.

  For example, when the vehicle height is lowered and raised, the energization start of the spring constant switching electromagnetic switching valves 16a-16 is made earlier than the energization start of the vehicle height control electromagnetic switching valves 51a-51d, and the electromagnetic switching valve The energization stop of the electromagnetic switching valves 16a to 16d was made slower than the energization stop of 51a to 51d. However, even when the energization of the electromagnetic switching valves 16a to 16d is stopped, the force due to the oil pressure difference obtained by subtracting the oil pressure in the fluid pressure cylinders 20a to 20d from the oil pressure in the accumulators 15a to 15d is the spring force (biasing force) of the spring 37. As long as it is larger than F, the electromagnetic switching valves 16a to 16d are kept closed.

  Therefore, if a hydraulic pressure difference obtained by subtracting the hydraulic pressure in the fluid pressure cylinders 20a to 20d from the hydraulic pressure in the accumulators 15a to 15d when the vehicle height decreases is ΔPx, at least ΔPx in the period from the start of the decrease in the vehicle height to the end of the decrease. The energization control of the electromagnetic switching valves 16a to 16d may be performed in a period in which the relationship of A ≦ F is established (see FIG. 5). Further, if a hydraulic pressure difference obtained by subtracting the hydraulic pressure in the fluid pressure cylinders 20a to 20d from the hydraulic pressure in the accumulators 15a to 15d when the vehicle height is increased is ΔPy, at least ΔPy · The electromagnetic switching valves 16a to 16d may be energized and controlled while the relationship A ≦ F is satisfied (see FIG. 5). A is the sealing area of the valve body 35.

1 is a schematic view of a vehicle suspension device including a vehicle height adjusting device according to an embodiment of the present invention. It is a longitudinal cross-sectional view which shows the electromagnetic switching valve for spring constant switching of FIG. (A)-(C) are schematic sectional drawings for demonstrating the action | operation of the said electromagnetic switching valve. It is a flowchart which shows the vehicle height control program performed by the electronic control unit of FIG. It is a time chart for demonstrating the action | operation of the vehicle height adjustment apparatus of FIG.

Explanation of symbols

11a to 11d: Wheel side member, 12a to 12d ... Car body side member, 14a to 14d, 15a to 15d ... Accumulator, 16a to 16d, 48, 51a to 51d ... Electromagnetic switching valve, 20a to 20d ... Fluid pressure cylinder, 61a to 61d ... Vehicle height sensor, 17 ... Center cylinder, 41 ... Pump, 42 ... Electric motor, 60 ... Electronic control unit (ECU), Wfl, Wfr, Wrl, Wrr ... Left and right front and rear wheels

Claims (4)

A fluid pressure cylinder provided between a wheel side member and a vehicle body side member of the vehicle and capable of changing a vehicle height by supplying and discharging fluid;
A fluid supply / discharge device that controls supply / discharge of fluid to / from the fluid pressure cylinder via a fluid passage;
An accumulator connected to the fluid passage;
In a vehicle height adjusting device comprising an electromagnetic switching valve interposed between the fluid passage and the accumulator,
The electromagnetic switching valve is configured as a normally open type that is set to a closed state by energization, and the fluid pressure in the accumulator is higher than the fluid pressure in the fluid pressure cylinder, and the pressure difference thereof is greater than a predetermined value. A vehicle height adjusting device configured to be set to a closed state even in a non-energized condition on the condition that it is large. In the vehicle height adjustment device according to claim 1,
The electromagnetic switching valve has a spring and urges the valve body in a direction opposite to the direction in which the valve body is seated on the valve seat by the fluid pressure in the fluid pressure cylinder and the spring force of the spring. The valve body is configured to be biased in the direction in which the valve body is seated on the valve seat by the fluid pressure of
The biasing force of the spring when the valve body is in the position seated on the valve seat is F, the seal area of the valve body when the valve body is seated on the valve seat is A, and the vehicle height is If a fluid pressure difference obtained by subtracting the fluid pressure in the fluid pressure cylinder when the vehicle height is set to a low state from the fluid pressure in the fluid pressure cylinder when set to a high state is ΔPo, ΔPo · A> F A vehicle height adjustment device that allows the relationship to be established. The vehicle height adjusting device according to claim 2, further comprising:
This is a fluid pressure difference obtained by controlling the fluid supply / discharge device to lower the vehicle height by discharging the fluid in the fluid pressure cylinder and subtracting the fluid pressure in the fluid pressure cylinder from the fluid pressure in the accumulator. If the fluid pressure difference that changes as the vehicle height decreases is ΔPx, the electromagnetic switching valve is energized at least during the period from the start to the end of the vehicle height until the end of the decrease. A vehicle height adjusting device provided with a lowering control means for controlling. The vehicle height adjusting device according to claim 2, further comprising:
A fluid pressure difference obtained by controlling the fluid supply / discharge device to raise the vehicle height by supplying fluid to the fluid pressure cylinder and subtracting the fluid pressure in the fluid pressure cylinder from the fluid pressure in the accumulator. When the fluid pressure difference that changes as the vehicle height increases is ΔPy, the electromagnetic switching valve is energized and controlled at least during the period from the start of the vehicle height increase to the end of the vehicle height, where ΔPy · A ≦ F. A vehicle height adjusting device provided with a rising control means.

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