JPH01120354A - Air pressure supply apparatus - Google Patents

Abstract

PURPOSE:To perform the effective and smooth starting of rotation with respect to a member marked in the hardening at low temp. such as a bellows member, by providing the first control means driving so as to bring the air pressure of an air pump for supplying an air stream to an ink jet head to the first air pressure and the second control means driving so as to bring the second air pressure higher than the first air pressure and driving the second control means only at the initial time of starting and driving the first control means during a stable driving period. CONSTITUTION:When an air pump ON-command (a) is inputted to a control system 12, the change-over switch 15 of a driver is changed over to a kick voltage driver 15 by the control signal (b) outputted by the control system 12. A trigger signal (c) is inputted to the kick voltage driver 15 from the control system 12 and diving voltage Vdm is outputted to be applied to an air pump 14. Then, the air pump 14 is forcibly rotated to start the rising of pressure. Next, the driver change-over switch 16 is changed over to a control driver 13 and the voltage applied to the air pump 14 is changed over to Vdc. Vdc is the drive voltage determined in the control system 12 on the basis of the pressure value detected by a pressure detection system 11 and becomes a characteristic curve wherein a voltage value drops as the rising in pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a pneumatic supply device for an on-demand inkjet head that uses an air flow to improve signal response characteristics.

Conventional technology An inkjet recording device using a so-called air flow type on-demand inkjet in which an air flow is added to ink ejection is disclosed in, for example, Japanese Patent Application Laid-Open No. 52-82426. The structure and operating principle are explained in detail in Japanese Patent Publication No. 5J-4SEC+S. The rising and falling characteristics of the airflow supplied to the head at the time of starting and ending the apparatus are described in detail in, for example, Japanese Patent Application Laid-Open No. 132565/1983.

Now, FIG. 2 is a relationship diagram showing the configuration of an on-demand type inkjet head with an added air flow, an air pressure supply device, and an ink supply system. The structure of the head is that an ink chamber 3.5 divided into two units is connected by a connecting passage 4, and an ink outflow path 6 is located on the straight line thereof, and an air chamber 7 having an air outflow path 8 is further provided outward. . By applying an electric signal from the electric signal source 14 to the electrostrictive element 1 bonded to the diaphragm 2, a bending moment acts on the diaphragm 2, the pressure in the inner ink chamber 3 increases, and the pressure in the connecting passage 4 increases. Ink located near the straight line is pushed out from the ink outflow passage 6. The air flow sent from the air pressure supply device 19 through the pulsating flow absorption capacity tank 15, the air supply pipe 12, and the air inlet 11 is as follows:
It passes through the air chamber 7 and constantly flows out from the air outflow path 8, and helps the ink droplets coming out from the ink outflow path 6 to fly in response to an electric signal. Ink is supplied to the inkjet head from an ink tank 18 through an ink supply pipe 13 and an ink inlet 10 to an outer ink chamber 5 .

By using air flow in the head, (1) the flying speed of ink droplets can be increased and the speed can be increased. (2) Ink dripping can be prevented. (3) Curving of ink droplets can be prevented. (4) Improved gradation characteristics. (5) The minimum ejection voltage becomes lower. There are other advantages. On the other hand, if there are pressure fluctuations in the airflow, the airflow acts directly on the ejected ink droplets, resulting in density unevenness and a significant deterioration in image quality. Therefore, the air pressure supply device 19 drives and controls an air pump in the configuration shown in FIG. 3(a), for example, in order to reduce pressure fluctuations. That is, in FIG. 3(a), a pressure detection system 31 is used to monitor the current pressure and form an input signal for the control system 32. In FIG. In the control system 32, an air pump drive signal is created based on a characteristic curve as shown in FIG. is Vd o to Vdr, Vd
The driving voltage decreases from t to Vd 2 and finally becomes Vdc at the pressure Pc where the leakage amount and the supply amount are balanced. If the pressure fluctuates around Pc, the driving voltage changes Vdc along the characteristic curve so as to keep it constant.

FIG. 4 shows an example of the pressure characteristics of the air pump 34 shown in FIG. 3(a), using the drive voltage Vd as a parameter.

Therefore, by controlling the pressure via the pressure feedback system shown in FIG. 3(a), it is possible to construct an air pressure supply device with extremely small pressure fluctuations.

Problem to be Solved by the Invention The air flow for the above purpose has a flow rate of about 2. O1,/rnx n
The permissible value of pressure fluctuation that does not cause density unevenness when used at a set value of s pressure of approximately 0.13 kg 7 cm2 is approximately 1.5% or less. Pressure fluctuations greater than this result in density unevenness and a deterioration in image quality. Normally, motor-driven air pumps are not applicable to the above-mentioned purpose because, when driven at a fixed voltage, the pressure fluctuations are relatively small, ranging from several to over ten or more.

Therefore, a control system as shown in the example described above is required. The selection of an air pump requires that it has an appropriate supply capacity for the above-mentioned flow rate and pressure settings, and that it must be operated via the above-mentioned control system, so it must be easy to control the flow rate, pressure, etc., and be inexpensive and have a long lifespan. The current situation is that the range of choices is limited because of the long length and other considerations.

FIG. 5 shows an example of the construction of an air pump for the above purpose. A cam 53 attached to the motor shaft 52 converts the rotational movement of the motor 51 into vertical movement of the shaft 54, and the vertical movement of the bellows 55 attached to the tip of the shaft 54 and the valve A56.
, the pressurized air flow is sent to the air supply port 5 by opening and closing the valve B57.
Output from 9. The load effect on the air pump drive is
These include those related to the air intake and air supply systems, as well as those related to rotation and vertical movement, but the movement of the bellows is particularly important.For example, if the engine is left at low temperatures for a long time, the bellows members may harden, making it difficult to start. In particular, when applied to the above purpose, the larger the difference between the air pump's supply capacity and the air pressure set value (air usage amount), the more difficult it is to suppress pressure fluctuations. The closer it is, the better for controlling pressure fluctuations. Therefore, if the supply amount exceeds the set value (air usage amount), a leak valve or the like is used to reduce the supply amount to an appropriate value, or the operating voltage of the air pump is lowered to reduce the supply amount. However, with the method of using a leak valve, the power supply, etc. must be prepared as is to accommodate the extra supply capacity, resulting in extremely poor efficiency.
Therefore, the method of reducing the supply amount by lowering the entire operating voltage of the other side is a more practical method with better performance. However, with this low-voltage drive type, there are problems such as hardening of the bellows, etc., which occurs when left at low temperatures for a long time, instability in starting rotation due to heavy loads, and, in the worst case, failure to start rotation. Occur.

In view of the above-mentioned prior art, the present invention provides an air pressure supply device that is an inexpensive air pump and is capable of effectively and smoothly starting rotation of materials that harden significantly at low temperatures, such as bellows members.

Means for Solving the Problems The present invention provides an air pump for supplying an air flow to an inkjet head, a first control drive means for driving the air pump so that the air pressure of the air pump becomes a first air pressure;
a second control drive means for driving the air pump so that the air pressure of the air pump becomes a second air pressure higher than the first air pressure; and the second control drive means only at the initial stage of starting the air pump. The above object is achieved by providing a switching control means for driving the air pump and driving the first control driving means during the stable driving period of the air pump.

Operation The present invention has the above-mentioned configuration, and when the air pump starts, the second control drive means is driven by the switching control means,
The air pump is initially rotated using a high drive voltage such as a kick voltage driver. When a certain period of time or a certain pressure increase is detected, the switching control means switches from the kick voltage driver or the like to the first control drive means, and shifts to drive voltage control determined by pressure detection or the like. The drive voltage output from the kick voltage driver is determined by experimentally determining a voltage value that is not affected by the pump operating environment. When the air pump is forced to start, moving parts such as the bellows of the inkjet head, which have hardened due to being left at low temperatures, will rise in temperature due to their own action, gradually becoming smoother, and returning to the same state as at room temperature. .

Embodiment FIG. 1(a) is a block diagram of a main part of an air pressure supply device according to an embodiment of the present invention, and FIG. 1(b) is a diagram showing the transition of the air pump driving voltage according to the present invention.

What is shown in Figure 1 is that when the pump is left at low temperatures for a long time, or when a starting torque greater than the normal control range is required due to other factors, the pump is activated only at the initial stage of startup, regardless of pressure control. This is to increase the applied voltage to ensure smooth initial rotation.

In Fig. 1, air pump ON command a is set to control system 1.
2, the driver selector switch 16 switches to control system 1.
The kick voltage driver 15 uses the control signal output from 2.
Switched to the side. A trigger signal C is input from the control system 12 to the kick voltage driver 15, and as a result, as shown in FIG. 1(b)
A driving voltage Vdm as shown in is outputted and applied to the air pump 14. Then, the air pump 14 is forcibly rotated and the pressure starts to rise. As shown in FIG. 1(b), the applied voltage Vdm is maintained from the ON command input point (A) of the air pump 14 to the point at which the ON command is applied.

Here, the point (b) is determined based on an experimentally determined constant time format or a rising pressure value detected by the pressure detection system 11. From point (b), switch the driver selector switch 16 to the control driver 13 side and change the voltage applied to the air pump 14 to V.
Switch to dc. Vdc is generated by a drive voltage determined within the control system 12 based on the pressure value detected by the pressure detection system 11, and has a characteristic curve in which the voltage value decreases as the pressure increases. Therefore, between points (b) and (c), the pressure decreases in inverse proportion to the pressure rise at the pressure rising section, and the set pressure is reached at point (c), and after that, Vdc decreases in order to absorb pressure fluctuations relative to the set pressure. When the pressure decreases, a higher voltage is applied, and when the pressure increases, a lower voltage is applied to control the pressure to the set pressure, resulting in constant pressure control.

Note that in this embodiment, the control drino (13) and the kick voltage driver 15 are shown separately through a changeover switch 16, but it is also possible to bring this changeover switch function to the control system 12 and use only one driver 15. This is the intended scope of the present invention.

Effects of the Invention As described above, the present invention is capable of effectively and smoothly starting rotation of materials that harden significantly at low temperatures, such as bellows members, using an inexpensive air pump. In addition, since low voltage drive control can be adopted without considering the lack of torque at startup, the degree of freedom in air pump selection is expanded, and it is possible to minimize normal pressure fluctuations while efficiently utilizing the drive power capacity. It is possible to construct a stable air pressure supply device.

[Brief explanation of the drawing]

FIG. 1(a) is a block diagram of an air pressure supply device according to an embodiment of the present invention, FIG. 1(b) is a diagram showing the transition of the driving voltage of the air pump 1 regarding the same device, and FIG. 2 is a diagram showing the air flow. A cross-sectional view showing the relationship between the configuration of the conventional on-demand ink jet head and the pneumatic supply device.
Figure (a) is a block diagram of a conventional air pressure supply device, Figure 3 (b) is a diagram showing the pressure control characteristic curve of the same device, Figure 4 is a diagram showing the pressure increase characteristic of the air pump of the same device, FIG. 5 is a structural diagram of the air pump of the same device. 11...Pressure detection system, 12...Control system, 13...
Control driver, 14...Air pump, 15...Kick voltage driver, 16...Driver changeover switch. Name of agent: Patent attorney Toshio Nakao and 1 other person Figure 1

Claims (1)

[Claims] an air pump that supplies an air flow to an inkjet head; a first control drive means that drives the air pump such that the air pressure of the air pump is a first air pressure; a second air pump that drives the air pump to a second air pressure higher than the air pressure;
and a switching control means for driving the second control and drive means only in the initial stage of starting of the air pump and for driving the first control and drive means during the stable drive period of the air pump. Feeding device.