用fig.add_axes子图绘制双X轴图表是，下X轴数值重叠

在用fig.add_axes子图绘制双X轴图表时，下X轴数值发生了重叠，自己用了tight layout之类的方法的都没有作用，求指教，代码是：
import matplotlib.pyplot as a

fig=a.figure(figsize=(10,10))

left,bottom,width,height=0.1,0.1,1,0.8
fig,ax1=a.subplots()
ax1=fig.add_axes([0.1,0.1,0.8,0.8])

ax1.set_title('yui')
ax1.set_xlabel('x ray')
ax1.set_ylabel('y ray')

x=range(5)
y=[X+1 for X in x]
y2=[X2 for X in x]
y3=[X3 for X in x]
ax1.plot(x,y,label='ert')

ax3=ax1.twinx()
ax3.plot(x,y2,label='dfg')

ax4=ax1.twiny()

ax4.plot(x,y3,label='jkl',c='r')

fig.legend(bbox_to_anchor=(0.26,0.7,0,-0.2))

ax2=fig.add_axes([0.2,0.6,0.25,0.25])
x=range(6)
y=[X+1 for X in x]
ax2.plot(x,y)

a.show()